SUPERGEN INC
S-3, 2000-02-14
PHARMACEUTICAL PREPARATIONS
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<PAGE>
   AS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION ON FEBRUARY 14, 2000
                                                     REGISTRATION NO. 333-
- --------------------------------------------------------------------------------
- --------------------------------------------------------------------------------
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549
                            ------------------------

                                    FORM S-3
                             REGISTRATION STATEMENT
                                     UNDER
                           THE SECURITIES ACT OF 1933
                            ------------------------

                                 SUPERGEN, INC.

             (Exact name of Registrant as specified in its charter)

<TABLE>
<S>                             <C>                             <C>
           DELAWARE                          2834                         91-1841574
 (State or other jurisdiction    (Primary Standard Industrial           (IRS Employer
              of                 Classification Code Number)        Identification Number)
incorporation or organization)
</TABLE>

                          TWO ANNABEL LANE, SUITE 220
                          SAN RAMON, CALIFORNIA 94583
                                 (925) 327-0200
  (Address, including zip code, and telephone number, including area code, of
                   Registrant's principal executive offices)

                                JOSEPH RUBINFELD
                                 PRESIDENT AND
                            CHIEF EXECUTIVE OFFICER
                                 SUPERGEN, INC.
                          TWO ANNABEL LANE, SUITE 220
                          SAN RAMON, CALIFORNIA 94583
                                 (925) 327-0200
 (Name, address, including zip code, and telephone number, including area code,
                             of agent for service)

                         ------------------------------

                                   COPIES TO:

<TABLE>
<S>                                                     <C>
               KATHLEEN B. BLOCH                                         PETER T. HEALY
                   JUNLING MA                                        O'Melveny & Myers LLP
                 JAY D. HANSEN                                      Embarcadero Center West
        Wilson Sonsini Goodrich & Rosati                               275 Battery Street
            Professional Corporation                              San Francisco, CA 94111-3305
               650 Page Mill Road                                        (415) 984-8833
            Palo Alto, CA 94304-1050
                 (650) 493-9300
</TABLE>

                         ------------------------------

        APPROXIMATE DATE OF COMMENCEMENT OF PROPOSED SALE TO THE PUBLIC:

AS SOON AS PRACTICABLE AFTER THE EFFECTIVE DATE OF THIS REGISTRATION STATEMENT.

                         ------------------------------

    If the only securities being registered on this Form are being offered
pursuant to dividend or interest reinvestment plans, check the following
box. / /

    If any of the securities being registered on this Form are to be offered on
a delayed or continuous basis pursuant to Rule 415 under the Securities Act of
1933, other than securities offered only in connection with dividend or interest
reinvestment plans, check the following box. / /

    If this Form is filed to register additional securities for an offering
pursuant to Rule 462(b) under the Securities Act, please check the following box
and list the Securities Act registration statement number of the earlier
effective registration statement for the same offering. / /

    If this Form is a post-effective amendment filed pursuant to Rule 462(c)
under the Securities Act, check the following box and list the Securities Act
registration statement number of the earlier effective statement for the same
offering. / /

    If delivery of the prospectus is expected to be made pursuant to Rule 434,
please check the following box. / /

                         ------------------------------

                        CALCULATION OF REGISTRATION FEE

<TABLE>
<CAPTION>
                                                                 PROPOSED MAXIMUM      PROPOSED MAXIMUM
          TITLE OF EACH CLASS                AMOUNT TO BE       OFFERING PRICE PER    AGGREGATE OFFERING        AMOUNT OF
    OF SECURITIES TO BE REGISTERED          REGISTERED(1)            SHARE(2)              PRICE(2)        REGISTRATION FEE(2)
<S>                                      <C>                   <C>                   <C>                   <C>
Common Stock $0.001 par value..........       3,105,000               $47.25             $146,711,250            $38,732
</TABLE>

(1) Includes 405,000 shares of common stock that may be purchased by the
    underwriters from selling stockholders upon exercise of the underwriters'
    over-allotment option.

(2) Estimated solely for the purpose of computing the registration fee and based
    on the average high and low sale prices of the common stock of
    SuperGen, Inc. as reported on the Nasdaq National Market on February 7, 2000
    in accordance with Rule 457 under the Securities Act.

    THE REGISTRANT HEREBY AMENDS THIS REGISTRATION STATEMENT ON SUCH DATE OR
DATES AS MAY BE NECESSARY TO DELAY ITS EFFECTIVE DATE UNTIL THE REGISTRANT SHALL
FILE A FURTHER AMENDMENT WHICH SPECIFICALLY STATES THAT THIS REGISTRATION
STATEMENT SHALL THEREAFTER BECOME EFFECTIVE IN ACCORDANCE WITH SECTION 8(A) OF
THE SECURITIES ACT OR UNTIL THE REGISTRATION STATEMENT SHALL BECOME EFFECTIVE ON
SUCH DATE AS THE COMMISSION, ACTING PURSUANT TO SAID SECTION 8(A), MAY
DETERMINE.

- --------------------------------------------------------------------------------
- --------------------------------------------------------------------------------
<PAGE>
Prospectus (Not Complete)
Issued February   , 2000
The information in this prospectus is not complete and may be changed without
notice. We may not sell these securities until the registration statement filed
with the Securities and Exchange Commission is effective. This prospectus is not
an offer to sell these securities, and we are not soliciting offers to buy these
securities, in any state where the offer or sale of these securities is not
permitted.
<PAGE>
                                2,700,000 SHARES

                                     [LOGO]

                                  COMMON STOCK
                                ----------------

    SuperGen, Inc. is offering 2,000,000 shares of common stock, and the selling
stockholders are offering 700,000 shares of our common stock in a firmly
underwritten offering. We will not receive any of the proceeds from the sale of
shares by the selling stockholders.

                            ------------------------

    Our common stock is traded on the Nasdaq National Market under the symbol
"SUPG." The last reported sale price for our common stock on the Nasdaq National
Market on February   , 2000 was $      per share.

                            ------------------------

    INVESTING IN OUR COMMON STOCK INVOLVES A HIGH DEGREE OF RISK. SEE "RISK
FACTORS" BEGINNING ON PAGE 5.

                            ------------------------

<TABLE>
<CAPTION>
                                                              Per Share      Total
                                                              ---------   -----------
<S>                                                           <C>         <C>
Offering price                                                 $          $
Discounts and Commissions to Underwriters                      $          $
Offering Proceeds to SuperGen                                  $          $
Offering Proceeds to Selling Stockholders                      $          $
</TABLE>

    Neither the Securities and Exchange Commission nor any state securities
commission has approved or disapproved these securities or determined if this
prospectus is truthful or complete. Any representation to the contrary is a
criminal offense.

    The selling stockholders have granted the underwriters the right to purchase
up to an additional 405,000 shares of common stock to cover any over-allotments.
The underwriters can exercise this right at any time within thirty days after
this offering. Banc of America Securities LLC expects to deliver the shares of
common stock to investors on              , 2000.

BANC OF AMERICA SECURITIES LLC
            LEHMAN BROTHERS
                        PRUDENTIAL VECTOR HEALTHCARE
                                    A UNIT OF PRUDENTIAL SECURITIES

                                     WARBURG DILLON READ LLC

                            ------------------------

                                         , 2000.
<PAGE>
    YOU SHOULD RELY ONLY ON THE INFORMATION CONTAINED IN THIS PROSPECTUS. WE
HAVE NOT AUTHORIZED ANYONE TO PROVIDE YOU WITH INFORMATION DIFFERENT FROM THAT
CONTAINED IN THIS PROSPECTUS. WE ARE OFFERING TO SELL, AND SEEKING OFFERS TO BUY
SHARES OF SUPERGEN, INC. COMMON STOCK ONLY IN JURISDICTIONS WHERE OFFERS AND
SALES ARE PERMITTED. THE INFORMATION CONTAINED IN THIS PROSPECTUS IS ACCURATE
ONLY AS OF THE DATE OF THIS PROSPECTUS, REGARDLESS OF THE TIME OF DELIVERY OF
THIS PROSPECTUS OR OF ANY SALE OF THE SUPERGEN, INC. COMMON STOCK. IN THIS
PROSPECTUS, REFERENCES TO "SUPERGEN," "WE," "US" AND "OUR" REFER TO
SUPERGEN, INC. AND ITS SUBSIDIARIES. WE HAVE NOT AUTHORIZED ANYONE TO PROVIDE
YOU WITH INFORMATION THAT IS DIFFERENT. THIS DOCUMENT MAY BE USED ONLY WHERE IT
IS LEGAL TO SELL THESE SECURITIES.

                               TABLE OF CONTENTS

<TABLE>
<S>                                                           <C>
Prospectus Summary..........................................    1
Risk Factors................................................    5
Note Regarding Forward-Looking Statements...................   14
Use of Proceeds.............................................   15
Price Range of Our Common Stock.............................   16
Dividend Policy.............................................   16
Capitalization..............................................   17
Business....................................................   18
Management..................................................   32
Selling Stockholders........................................   35
Description of Capital Stock................................   36
Underwriting................................................   38
Legal Matters...............................................   40
Experts.....................................................   40
Where You Can Find More Information.........................   41
</TABLE>

                            ------------------------

    Nipent, Spartaject and Extra are our trademarks. All other trademarks used
in this prospectus are the property of their respective owners.
<PAGE>
                               PROSPECTUS SUMMARY

    THIS SUMMARY HIGHLIGHTS SELECTED INFORMATION CONTAINED ELSEWHERE IN THIS
PROSPECTUS. THIS SUMMARY DOES NOT CONTAIN ALL THE INFORMATION THAT YOU SHOULD
CONSIDER BEFORE MAKING AN INVESTMENT DECISION. THIS PROSPECTUS CONTAINS
FORWARD-LOOKING STATEMENTS. OUR ACTUAL PERFORMANCE MAY DIFFER FROM THAT
PREDICTED IN SUCH STATEMENTS AS A RESULT OF VARIOUS FACTORS, INCLUDING THOSE SET
FORTH IN "RISK FACTORS" AND ELSEWHERE IN THIS PROSPECTUS. EXCEPT AS OTHERWISE
INDICATED, ALL INFORMATION IN THIS PROSPECTUS ASSUMES NO EXERCISE OF THE
UNDERWRITIERS' OVER-ALLOTMENT OPTION.

                                 SUPERGEN, INC.

    We are an emerging pharmaceutical company dedicated to the acquisition,
rapid development and commercialization of oncology therapies for solid tumors
and hematological malignancies. We seek to minimize the time, expense and
technical risk associated with drug commercialization by identifying and
acquiring pharmaceutical compounds in the later stages of development, rather
than committing significant resources to the research phase of drug discovery.
We intend to retain significant participation in the commercialization of our
proprietary products by funding and undertaking human clinical development
ourselves. We believe this will allow us to maximize the commercial value of our
products by either directly marketing our products or licensing them on more
favorable terms than would be available if licensed earlier in the development
cycle.

    Our lead product candidate is rubitecan, an oral chemotherapy compound in
the camptothecin class which is in pivotal Phase III clinical trials for
pancreatic cancer which is the fourth leading cause of death by cancer in the
United States. Rubitecan is a second-generation topoisomerase I inhibitor that
causes single-strand breaks in the DNA of rapidly dividing tumor cells. We
believe that rubitecan may have significant advantages over many existing
anticancer drugs. These advantages include increased survival, oral dosing and a
superior side effect profile. We believe that rubitecan is a platform drug for
leadership in the treatment of a broad array of solid tumors and hematological
malignancies.

    Results of a Phase II clinical trial conducted by the Stehlin Foundation for
Cancer Research using rubitecan for treatment of pancreatic cancer indicate a
favorable comparison with historical treatment options in terms of quality of
life, survival data and tumor size reduction. In this Phase II trial the median
survival in the 60 evaluable patients who took the required eight week course of
therapy was nearly nine months, significantly greater than the average survival
time of four to five months under other treatment methods.

    We are evaluating rubitecan in three separate stand-alone pivotal Phase III
clinical trials for pancreatic cancer. The trials are randomized, unblinded
studies being conducted in approximately 200 centers and are designed to include
up to 1,800 patients. The primary endpoint of these trials is survival. We
commenced these trials in November 1998 and we have over 700 patients currently
enrolled. If any one of these trials is successful we anticipate filing a New
Drug Application with the U.S. Food and Drug Administration, or FDA, by early
2001.

    We are aggressively pursuing additional Phase II and III trials using
rubitecan both as a single therapeutic agent and in combination with other
anticancer agents in both solid tumors and hematological malignancies. We intend
to make available to physicians copies of peer-reviewed medical journal articles
and other validated scientific information related to these trials. We believe
this will provide physicians with more up-to-date product information and will
better enable them to meet their patients' medical needs.

    In December 1999 we entered into an alliance with Abbott Laboratories under
which Abbott will market and distribute rubitecan and invest in shares of our
common stock. We will co-promote rubitecan with Abbott in the United States and
Abbott has exclusive rights to market rubitecan outside of the United States. In
the U.S. market, we will share profits from product sales equally with Abbott.

                                       1
<PAGE>
Outside of the U.S. market, Abbott will pay us royalties and transfer fees based
on product sales. We will remain responsible for pursuing and funding the
clinical development of rubitecan and obtaining regulatory approval for the
product in the United States, Canada and the member states of the European
Union.

    In addition, we will receive a number of equity investments and cash
payments from Abbott which, when aggregated, amount to approximately
$150 million. Each equity investment and cash payment is conditioned upon the
achievement of certain developmental and sales milestones. In January 2000 we
received a $26.5 million equity investment and a $5 million cash payment from
Abbott. We also granted Abbott an option to purchase up to 49% of the
outstanding shares of our common stock at an exercise price of $85 per share
which expires in March 2003.

    We are also pursuing the clinical development of Nipent and decitabine for
the treatment of certain solid tumor cancers and hematological disorders. We
acquired Nipent from Warner-Lambert Company in 1996 and we are selling this drug
in the United States for the treatment of hairy cell leukemia, a type of
B-lymphocytic leukemia. We believe that Nipent has a unique mechanism of action
and Phase II trials indicate that it may have activity in a variety of other
hematologic cancers. In oncology, we are pursuing treatments for lymphatic
malignancies and disorders, such as cutaneous T-cell lymphoma, chronic
lymphocytic leukemia, non-Hodgkin's lymphoma and prolymphocytic leukemia. In
addition, Nipent has shown activity in various autoimmune diseases, including
graft-versus-host disease which is not responsive to standard therapies, and
rheumatoid arthritis. We estimate the United States markets for both
graft-versus-host disease and rheumatoid arthritis are larger than the market
for Nipent's leukemia applications. We are conducting Phase I clinical trials in
both of these indications.

    Decitabine has been successful in multiple Phase II trials in the United
States and Europe for treating myelodysplastic syndromes, or MDS, chronic
myeloid leukemia and acute myeloid leukemia. Based on positive results from
these studies, we are finalizing the protocol for a randomized Phase III study
comparing decitabine to best supportive care for MDS. We expect to commence
patient enrollment for this study in 2000. In addition, preliminary results
suggest that decitabine has activity in solid tumors such as non-small cell lung
cancer. Phase I clinical trials with decitabine are underway for this
indication.

    We incorporated in March 1991 as a California corporation and changed our
state of incorporation to Delaware in November 1997. Our executive offices are
located at Two Annabel Lane, Suite 220, San Ramon, California, 94583, and our
telephone number at that address is (925) 327-0200. We maintain a website on the
internet at WWW.SUPERGEN.COM. Our website, and the information contained
therein, is not a part of this prospectus.

                                       2
<PAGE>
                                  THE OFFERING

<TABLE>
<S>                                            <C>
Common stock offered by us...................  2,000,000 shares

Common stock offered by the selling
  stockholders...............................  700,000 shares

Common stock to be outstanding after the
  offering...................................  29,654,757 shares

Use of proceeds..............................  We intend to use the proceeds from this
                                               offering:

                                               -  for research and development activities,
                                                  including expansion of clinical trials;

                                               -  to enhance sales and marketing efforts in
                                               the advance of the potential launch of
                                                  rubitecan;

                                               -  to finance possible acquisitions of
                                                  complimentary products, technologies or
                                                  businesses;

                                               -  to improve facilities and potentially
                                               enhance manufacturing capabilities; and

                                               -  for working capital and other general
                                                  corporate purposes.

Nasdaq National Market Symbol................  SUPG
</TABLE>

    The number of shares of our common stock to be outstanding after this
offering is based on the number of shares outstanding as of January 31, 2000 and
does not include the following:

    - 3,499,230 shares of common stock reserved for issuance under our 1993
      Stock Option Plan, 1996 Directors' Stock Option Plan and 1998 Employee
      Stock Purchase Plan, and under options assumed in connection with our
      acquisition of Sparta Pharmaceuticals, Inc. Of these reserved shares,
      options to purchase 3,325,580 shares of common stock were outstanding as
      of January 31, 2000 at a weighted exercise price of $9.59 per share, and

    - 6,312,502 shares of common stock issuable upon exercise of warrants
      outstanding as of January 31, 2000 at a weighted average exercise price of
      $15.32 per share. In September 1999 we notified holders of warrants issued
      in connection with our initial public offering that we will redeem any
      such warrants that remain unexercised on April 16, 2000 at a redemption
      price of $0.25 per share. As of January 31, 2000 there were 3,062,452 of
      such warrants outstanding with an exercise price of $9.00 per share.

                                       3
<PAGE>
                      SUMMARY CONSOLIDATED FINANCIAL DATA

    The following tables present our summary of financial data included
elsewhere in the prospectus. You should read the following data with the more
detailed information contained in "Selected Financial Data," "Management's
Discussion and Analysis of Financial Condition and Results of Operations" and
our financial statements and related notes appearing elsewhere in this
prospectus.

    The summary balance sheet data as of September 30, 1999 is presented on an
actual basis and is also presented to reflect:

    - on a pro forma basis, our sale of 933,394 shares of common stock to Abbott
      in January 2000 with proceeds of $26.5 million; and

    - on a pro forma as adjusted basis, our sale of 2,000,000 shares of common
      stock in this offering at an assumed public offering price of $      per
      share, less estimated underwriting discounts and estimated offering
      expenses to be paid by us.

<TABLE>
<CAPTION>
                                      NINE MONTHS                                            NINE MONTHS ENDED
                         YEAR ENDED      ENDED             YEAR ENDED DECEMBER 31,             SEPTEMBER 30,
                         MARCH 31,    DECEMBER 31,   ------------------------------------   -------------------
                            1995          1995          1996         1997         1998        1998       1999
                         ----------   ------------   ----------   ----------   ----------   --------   --------
                                                 (IN THOUSANDS, EXCEPT PER SHARE DATA)          (UNAUDITED)
<S>                      <C>          <C>            <C>          <C>          <C>          <C>        <C>
CONSOLIDATED STATEMENT
  OF OPERATIONS DATA:
Total revenue..........   $   169       $    13       $   264      $  1,802     $  3,004    $  2,089   $  3,076
Cost of sales..........        --            --           283         1,539        1,925       1,327      1,324
Research and
  development..........     2,986         2,174         6,152         8,583       10,511       7,630     10,730
Selling, general and
  administrative.......       933           643         2,894         4,952        7,046       5,070      7,077
Acquisition of
  in-process research
  and development......        --            --           442         3,506           --          --     10,850
                          -------       -------       -------      --------     --------    --------   --------
Loss from operations...    (3,750)       (2,804)       (9,507)      (16,778)     (16,478)    (11,938)   (26,905)
Other income
  (expense)............       111            75           749           782          901         742     (1,475)
                          -------       -------       -------      --------     --------    --------   --------
Net loss...............   $(3,639)      $(2,729)      $(8,758)     $(15,996)    $(15,577)   $(11,196)  $(28,380)
                          =======       =======       =======      ========     ========    ========   ========
Basic and diluted net
  loss per common
  share................   $ (0.31)      $ (0.22)      $ (0.55)     $  (0.85)    $  (0.77)   $  (0.55)  $  (1.29)
Shares used to compute
  basic and diluted net
  loss per common
  share................    11,908        12,629        15,961        18,765       20,353      20,326     21,993
</TABLE>

<TABLE>
<CAPTION>
                                                                    AS OF SEPTEMBER 30, 1999
                                                              -------------------------------------
                                                                                       PRO FORMA
                                                               ACTUAL    PRO FORMA   AS ADJUSTED(1)
                                                              --------   ---------   --------------
                                                                         (IN THOUSANDS)
                                                                           (UNAUDITED)
<S>                                                           <C>        <C>         <C>
BALANCE SHEET DATA:
Cash, cash equivalents and marketable securities............  $32,886     $59,386      $
Total assets................................................   46,762      73,262
Long-term debt..............................................       --          --              --
Stockholders' equity........................................   43,531      70,031
</TABLE>

- ------------------------

    (1) Does not include the proceeds from the redemption of our outstanding
common stock warrants issued at the time of our initial public offering. If all
warrants outstanding at September 30, 1999 are exercised prior to the redemption
date of April 16, 2000, we will receive approximately $34 million.

                                       4
<PAGE>
                                  RISK FACTORS

    YOU SHOULD CAREFULLY CONSIDER THE RISKS DESCRIBED BELOW, TOGETHER WITH ALL
OF THE OTHER INFORMATION INCLUDED IN OR INCORPORATED BY REFERENCE INTO THIS
PROSPECTUS, BEFORE MAKING AN INVESTMENT DECISION. THE RISKS AND UNCERTAINTIES
DESCRIBED BELOW ARE NOT THE ONLY ONES WE FACE. IF ANY OF THE FOLLOWING RISKS
ACTUALLY OCCUR, OUR BUSINESS COULD BE HARMED. IN SUCH CASE, THE TRADING PRICE OF
OUR COMMON STOCK COULD DECLINE, AND YOU MAY LOSE ALL OR PART OF YOUR INVESTMENT.

IF THE RESULTS OF FURTHER CLINICAL TESTING INDICATE THAT OUR PROPOSED PRODUCTS
ARE NOT SAFE AND EFFECTIVE FOR HUMAN USE, OUR BUSINESS WILL SUFFER.

    Most of our products are in the development stage and prior to their sale
will require the commitment of substantial resources. All of the potential
proprietary products that we are currently developing will require extensive
preclinical and clinical testing before we can submit any application for
regulatory approval. Before obtaining regulatory approvals for the commercial
sale of any of our products, we must demonstrate through pre-clinical testing
and clinical trials that our product candidates are safe and effective in
humans. Conducting clinical trials is a lengthy, expensive and uncertain
process. Completion of clinical trials may take several years or more. The
length of time generally varies substantially according to the type, complexity,
novelty and intended use of the product candidate. Our clinical trials may be
suspended at any time if we or the FDA believe the patients participating in our
studies are exposed to unacceptable health risks. We may encounter problems in
our studies which will cause us or the FDA to delay or suspend the studies. Our
commencement and rate of completion of clinical trials may be delayed by many
factors, including:

    - ineffectiveness of the study compound, or perceptions by physicians that
      the compound is not effective for a particular indication;

    - inability to manufacture sufficient quantities of compounds for use in
      clinical trials;

    - failure of the FDA to approve our clinical trial protocols;

    - slower than expected rate of patient recruitment;

    - inability to adequately follow patients after treatment;

    - unforeseen safety issues;

    - lack of efficacy during the clinical trials; or

    - government or regulatory delays.

    The clinical results we have obtained to date do not necessarily predict
that the results of further testing, including later-stage controlled human
clinical testing, will be successful. If our trials are not successful, or are
perceived as not successful by the FDA or physicians, our business, financial
condition and results of operations will be harmed.

IF WE FAIL TO OBTAIN REGULATORY MARKETING APPROVALS IN A TIMELY MANNER, OUR
BUSINESS WILL SUFFER.

    Even if we believe our trials are successful, the FDA may require additional
clinical testing and, therefore we would have to commit additional unanticipated
resources. The FDA has substantial discretion in the drug approval process. We
cannot assure you that we will obtain the necessary regulatory approvals to
market our products. The FDA and comparable agencies in foreign countries impose
substantial requirements for the introduction of both new pharmaceutical
products and generic products through lengthy and detailed clinical testing
procedures, sampling activities and other costly and time-consuming compliance
procedures. We have not yet received marketing approval for any of our
internally developed proprietary products. Our proprietary drugs and products
will require lengthy

                                       5
<PAGE>
clinical trials along with FDA and comparable foreign agency review as new
drugs. Our generic drugs will also require regulatory review and approval.

    We cannot predict with certainty if or when we might submit for regulatory
review those products currently under development. Once we submit our potential
products for review, we cannot assure you that the FDA or other regulatory
agencies will grant approvals for any of our pharmaceutical products on a timely
basis or at all. Sales of our products outside the United States will be subject
to regulatory requirements governing clinical trials and marketing approval.
These requirements vary widely from country to country and could delay the
introduction of our products in those countries.

IF OUR RELATIONSHIP WITH ABBOTT IS NOT SUCCESSFUL, OUR BUSINESS COULD BE HARMED.

    Our strategic relationship with Abbott is important to our success. However,
that relationship may not be successful. We cannot assure you that we will
receive any additional payments from Abbott or that the relationship will be
commercially successful. The transactions contemplated by our agreements with
Abbott, including the equity purchases and cash payments, are subject to
numerous risks and conditions. For example:

    - we may fail to achieve clinical and sales milestones;

    - rubitecan may fail to achieve regulatory approval domestically and
      internationally;

    - rubitecan may not be commercially successful;

    - Abbott may fail to perform its obligations under our agreements, such as
      failing to devote sufficient resources to marketing rubitecan; and

    - our agreements with Abbott may be terminated in their entirety or on a
      territory-by-territory basis against our will.

The occurrence of any of these events could severely harm our business.

WE HAVE GRANTED CERTAIN RIGHTS TO ABBOTT THAT COULD NEGATIVELY AFFECT YOUR
INVESTMENT.

    We have granted Abbott an option to purchase shares of our common stock so
that upon its exercise Abbott will own up to 49% of our outstanding common
stock. Our ability to satisfy this contractual obligation is subject to a number
of conditions outside of our control, including:

    - stockholder approval of an increase in the number of shares of our
      authorized common stock;

    - stockholder approval of a potential change in control under the rules of
      the Nasdaq National Market; and

    - clearance of the purchase by federal antitrust regulators.

If we do not satisfy any of these conditions, Abbott could terminate our
relationship. If we obtain all necessary approvals and Abbott exercises its
option, the stock ownership of our other stockholders will be diluted and Abbott
will have significant influence over us. Abbott's right to exercise this option,
and Abbott's share ownership after exercise, may discourage other parties from
acquiring us.

    Abbott has a right of first discussion with respect to our product portfolio
and a right of first refusal to acquire us. These rights may discourage third
parties from bidding on any assets that we wish to sell or license and may
discourage acquisition bids. These provisions may limit the price that investors
might be willing to pay in the future for shares of our common stock.

                                       6
<PAGE>
WE HAVE A HISTORY OF OPERATING LOSSES AND AN ACCUMULATED DEFICIT, WE MAY NOT
ACHIEVE OR MAINTAIN PROFITABILITY IN THE FUTURE, AND WE MAY NEED TO OBTAIN
ADDITIONAL FUNDING.

    We incurred cumulative losses of $84.3 million for the period from inception
through September 30, 1999. These losses included non-cash charges of
$18.4 million for the acquisition of in-process research and development.
Currently we are not profitable and we expect to continue to incur substantial
operating losses at least through 2000 and into 2001. Our ability to achieve
profitability will depend primarily on our ability to obtain regulatory approval
for and successfully commercialize rubitecan. Our success will also depend, to a
lesser extent, on our ability to develop and obtain regulatory approval of
Nipent for indications other than hairy cell leukemia and to bring our
proprietary products to market. Our ability to become profitable will also
depend upon a variety of other factors, including the following:

    - increases in the level of our research and development, including the
      timing and costs of any expansion of clinical trials;

    - regulatory approvals of competing products, or expanded labeling approvals
      of existing products;

    - increases in sales and marketing expenses related to the commercial launch
      of rubitecan;

    - delays in or inadequate commercial sales of rubitecan, once regulatory
      approvals have been received; and

    - expenditures associated with acquiring products, technologies or companies
      and further developing these assets.

We cannot predict the outcome of these factors and we cannot assure you that we
will ever become profitable.

    Even if we do become profitable, we may need substantial additional funding.
We expect that our rate of spending will accelerate as a result of increased
clinical trial costs and expenses associated with regulatory approval and
commercialization of our products now in development. We anticipate that our
capital resources after this offering will be adequate to fund operations and
capital expenditures at least through 2001. However, if we experience
unanticipated cash requirements during this period, we could require additional
funds much sooner. Our business, results of operations and cash flows will be
adversely affected if we fail to obtain adequate funding in a timely manner, or
at all. We may receive funds from the sale of equity securities, or the exercise
of outstanding warrants and stock options. Additionally, we may receive funds
upon the achievement of certain developmental and sales milestones pursuant to
our agreement with Abbott. However, we cannot assure you that any of those
fundings will occur, or if they occur, that they will be on terms favorable to
us. Also, the dilutive effect of those fundings could adversely affect our
results per share.

WE HAVE LIMITED SALES AND MARKETING CAPABILITIES AND NO DISTRIBUTION
CAPABILITIES AND MAY NOT BE ABLE TO SUCCESSFULLY COMMERCIALIZE OUR PRODUCTS.

    We currently have limited sales and marketing resources and no distribution
capability. Although we have 18 sales and marketing personnel focusing on the
sale of our products to hospitals and hospital buying groups, we anticipate
relying on third parties to sell and market some of our primary products. For
instance, we will co-promote the potential sale of rubitecan with Abbott.
However, we may not be able to enter into additional sales and marketing
arrangements with others on acceptable terms, if at all. If our arrangements
with third parties are not successful, or if we are unable to enter into
third-party arrangements, then we may need to substantially expand our sales and
marketing force. We may not succeed in enhancing our sales and marketing
capabilities or have sufficient resources to do so. If we do develop such
capabilities, we will compete with other companies that have experienced and
well-funded sales and marketing operations. We currently rely on third parties
to distribute our

                                       7
<PAGE>
products and expect to continue to do so in the future. If we fail to establish
successful sales and marketing capabilities or fail to enter into successful
marketing arrangements with third parties, or if our third party distributors
fail to perform their obligations, our business, financial condition and results
of operations will be materially and adversely affected.

IF WE FAIL TO COMPLY WITH THE GOVERNMENTAL REGULATIONS, OUR BUSINESS WILL
  SUFFER.

    All new drugs, including our products under development, are subject to
extensive and rigorous regulation by the FDA, and comparable agencies in state
and local jurisdictions and in foreign countries. These regulations govern,
among other things, the development, testing, manufacturing, labeling, storage,
premarket approval, advertising, promotion, sale and distribution of our
products. Satisfaction of these requirements typically takes several years and
the time needed to satisfy them may vary substantially, based on the type,
complexity and novelty of the pharmaceutical product. The effect of government
regulation may be to delay or to prevent marketing of our potential products for
a considerable period of time and to impose costly procedures upon our
activities. If regulatory approval of our products is granted, such approval may
impose limitations on the indicated uses for which our products may be marketed.
Further, even if regulatory approval is obtained for a product, later discovery
of previously unknown problems may result in restrictions of the product,
including withdrawal of the product from the market.

    Among the conditions for FDA approval of all of our products in development
is the requirement that the manufacturer's (at either our facilities or those of
a third party manufacturer) quality control and manufacturing procedures conform
to current Good Manufacturing Practices, or GMPs, which must be followed at all
times. The FDA and foreign regulatory authorities strictly enforce GMP
requirements through periodic unannounced inspections. We cannot assure you that
the FDA will determine that our facilities and manufacturing procedures or any
third party manufacturer of our products will conform to GMP requirements.
Additionally, we or our third party manufacturer must pass a preapproval
inspection before we can obtain marketing approval for any of our products in
development. Failure to comply with applicable FDA and other regulatory
requirements can result in sanctions being imposed on us or the manufacturers of
our products including warning letters, product recalls or seizures,
injunctions, refusal to permit products to be imported into or exported out of
the United States, refusals of the FDA to grant premarket approval or to allow
us to enter into government supply contracts, withdrawals of previsouly approved
marketing applications, civil fines and criminal prosecutions.

    The FDA's policies may change and additional government regulations may be
promolgated which could prevent or delay regulatory approval of our products. We
cannot predict the likelihood of adverse governmental regulation which may arise
from future legislative or administrative action, either in the United States or
abroad.

IF WE FAIL TO COMPETE EFFECTIVELY, PARTICULARLY AGAINST LARGER, MORE ESTABLISHED
PHARMACEUTICAL COMPANIES WITH GREATER RESOURCES, OUR BUSINESS WILL SUFFER.

    Factors affecting competition in the pharmaceutical industry vary depending
on the extent to which the competitor is able to achieve a competitive advantage
based on proprietary technology. These factors include financial resources,
research and development capabilities, and manufacturing and marketing
experience and resources. If we are able to establish and maintain a significant
proprietary position with respect to our proprietary products, competition will
likely depend primarily on the effectiveness of our products, their acceptance
in the marketplace and their pricing and the number, gravity and severity of
their unwanted side effects as compared to alternative products.

    Our competitors have substantially greater financial, research and
development, manufacturing and marketing experience and resources than we do and
represent substantial long-term competition for us.

                                       8
<PAGE>
These competitors and probable competitors include established companies such as
Eli Lilly & Co., Ortho-McNeil Pharmaceutical, Amgen Inc., Bristol-Myers Squibb
Company and Immunex Corp. If these companies succeed in developing
pharmaceutical products that are more effective or less costly than any that we
may develop or market, our business will suffer.

THE PATENTS ON THE COMPOUNDS FOR WHICH WE ARE DEVELOPING GENERIC AND EXTRA
PRODUCTS ARE HELD BY THIRD PARTIES. IF THESE PATENTS ARE EXPANDED IN SCOPE OR DO
NOT EXPIRE WHEN ANTICIPATED, OUR BUSINESS COULD SUFFER.

    We plan to develop and market several generic and Extra drugs based on
existing compounds, some of which are currently protected by one or more patents
held by others. If the existing patent protection for these drugs is maintained
or expanded, it is unlikely that we will be able to market our own generic and
Extra versions of those drugs without obtaining a license from the patent owner,
which may not be available on commercially acceptable terms, or at all.

WE DEPEND ON THIRD PARTIES FOR MANUFACTURING AND STORAGE OF OUR PRODUCTS AND OUR
BUSINESS MAY BE HARMED IF THE MANUFACTURE OF OUR PRODUCTS IS INTERRUPTED OR
DISCONTINUED.

    We have no manufacturing facilities and we currently rely on third parties
for manufacturing activities related to all of our products. As we develop new
products and increase sales of our existing products, we must establish and
maintain relationships with manufacturers to produce and package sufficient
supplies of our finished pharmaceutical products, including rubitecan.

    Our manufacturing strategy presents the following risks:

    - delays in scale-up to quantities needed for multiple clinical trials could
      delay clinical trials, regulatory submissions and commercialization of our
      products in development;

    - our current and future manufacturers are subject to ongoing periodic
      unannounced inspection by the FDA and corresponding state agencies for
      compliance with strictly enforced GMP regulations and similar foreign
      standards, and we do not have control over our third-party manufacturers'
      compliance with these regulations and standards;

    - if we need to change to other commercial manufacturing contractors, the
      FDA and comparable foreign regulators must approve these contractors prior
      to our use. This would require new testing and compliance inspections. The
      new manufacturers would have to be educated in, or themselves develop
      substantially equivalent processes necessary for, the production of our
      products. In addition, the FDA and comparable foreign regulators would
      need to approve the new manufacturers;

    - if market demand for our products increases suddenly, our current
      manufacturers might not be able to fulfill our commercial needs, which
      would require us to seek new manufacturing arrangements and may result in
      substantial delays in meeting market demand; and

    - we may not have intellectual property rights, or may have to share
      intellecual rights, to any improvements in the manufacturing processes or
      new manufacturing processes for our products.

    Any of these factors could delay clinical trials or commercialization of our
products under development, interfere with current sales, entail higher costs
and result in our being unable to effectively sell our products.

    In addition, we store the majority of the unpurified, bulk form of Nipent at
a single location. Improper storage, fire, natural disaster, theft or other
conditions at this location that may lead to the loss or destruction of the bulk
concentrate could adversely affect our business, results of operations and cash
flows. We are currently negotiating a long-term agreement with the vendor that
purifies our current supply of crude concentrate to continue its purification
services. However, we cannot assure you

                                       9
<PAGE>
that we will be able to finalize the agreement. If we are not able to do so, our
supply of Nipent may be interrupted while we seek to locate another facility and
have that facility approved by the FDA. The delay could adversely affect our
business, results of operations and cash flows.

    We do not currently intend to manufacture any pharmaceutical products,
although we may choose to do so in the future. If we decide to manufacture
products, we would be subject to the regulatory risks and requirements described
above. We will also be subject to similar risks regarding delays or difficulties
encountered in manufacturing these pharmaceutical products and we will require
additional facilities and substantial additional capital. In addition, we have
only limited experience in manufacturing pharmaceutical products. We cannot
assure you that we would be able to manufacture any of these products
successfully in accordance with regulatory requirements and in a cost-effective
manner.

ASSERTING, DEFENDING AND MAINTAINING INTELLECTUAL PROPERTY RIGHTS COULD BE
DIFFICULT AND COSTLY AND FAILURE TO DO SO WILL HARM OUR ABILITY TO COMPETE AND
THE RESULTS OF OUR OPERATIONS.

    If competitors develop substantially equivalent proprietary information and
techniques or otherwise gain access to our trade secrets, if our trade secrets
are disclosed or if we cannot effectively protect our rights to unpatented trade
secrets, our business will be harmed.

    The pharmaceutical fields are characterized by a large number of patent
filings. A substantial number of patents have already been issued to other
pharmaceutical companies, research or academic institutions or others.
Competitors may have filed applications for or have been issued patents and may
obtain additional patents and proprietary rights related to products or
processes that compete with or are similar to ours. We may not be aware of all
of the patents potentially adverse to our interests that may have been issued to
others.

    We actively seek patent protection for our proprietary products and
technologies. We have a number of United States patents and also have licenses
to, or assignments of, numerous patents issued both in the United States and
elsewhere. We may also license our patents outside the United States.
Limitations on patent protection outside the United States, and differences in
what constitutes patentable subject matter in countries outside the United
States, may limit the protection we have on patents or licenses of patents
outside the United States.

    Litigation may be necessary to protect our patent position, and we cannot be
certain that we will have the required resources to pursue the necessary
litigation or otherwise to protect our patent rights. Our efforts to protect our
patents may fail. In addition to pursuing patent protection in appropriate
cases, we also rely on trade secret protection for unpatented proprietary
technology. However, trade secrets are difficult to protect. Our trade secrets
or those of our collaborators may become known or may be independently
discovered by others.

    Our proprietary products are dependent upon compliance with numerous
licenses and agreements. These licenses and agreements require us to make
royalty and other payments, reasonably exploit the underlying technology of the
applicable patents, and comply with regulatory filings. If we fail to comply
with these licenses and agreements, we could lose the underlying rights to one
or more of these potential products, which would adversely affect our business,
results of operations and cash flows.

                                       10
<PAGE>
    From time to time we receive correspondence inviting us to license patents
from third parties. Although we know of no pending patent infringement suits,
discussions regarding possible patent infringements or threats of patent
infringement litigation either related to patents held by us or our licensors or
our products or proposed products, there has been, and we believe that there
will continue to be, significant litigation in the pharmaceutical industry
regarding patent and other intellectual property rights. Claims may be brought
against us in the future based on patents held by others. These persons could
bring legal actions against us claiming damages and seeking to enjoin clinical
testing, manufacturing and marketing of the affected product. If we become
involved in any litigation, it could consume a substantial portion of our
resources, regardless of the outcome of the litigation. If any of these actions
are successful, in addition to any potential liability for damages, we could be
required to obtain a license to continue to manufacture or market the affected
product. We cannot assure you whether we would prevail in any of these actions
or that we could obtain any licenses required under any of these patents on
acceptable terms, if at all.

IF WE LOSE KEY PERSONNEL OR ARE UNABLE TO ATTRACT AND RETAIN ADDITIONAL, HIGHLY
SKILLED PERSONNEL REQUIRED FOR THE EXPANSION OF OUR ACTIVITIES, OUR BUSINESS
WILL SUFFER.

    Our success is dependent on key personnel, including Dr. Rubinfeld, our
President and Chief Executive Officer, and members of our senior management and
scientific staff. To successfully expand our operations, we will need to attract
and retain additional, highly skilled individuals, particularly in the areas of
sales, marketing, clinical administration, manufacturing and finance. We compete
with other companies for the services of existing and potential employees. We
believe our compensation and benefits packages are competitive for our
geographical region and our industry group. However, we may be at a disadvantage
to the extent that potential employees may favor larger, more established
employers.

THE CONTINUING EFFORTS OF GOVERNMENT AND THIRD-PARTY PAYERS TO CONTAIN OR REDUCE
THE COSTS OF HEALTHCARE MAY ADVERSELY AFFECT OUR REVENUES AND PROFITABILITY.

    Our revenues and profitability may be affected by the continuing efforts of
governmental and third-party payers to contain or reduce the costs of health
care. We cannot predict the effect that these health care reforms may have on
our business, and it is possible that any of these reforms will adversely affect
our business. In addition, in both the United States and elsewhere, sales of
prescription pharmaceuticals are dependent in part on the availability of
reimbursement to the consumer from third-party payers, like government and
private insurance plans. Third-party payers are increasingly challenging the
prices charged for medical products and services. If our current and proposed
products are not considered cost-effective, reimbursement to the consumer may
not be available or be sufficient to allow us to sell products on a competitive
basis.

WE MAY BE SUBJECT TO PRODUCT LIABILITY LAWSUITS AND OUR INSURANCE MAY BE
INADEQUATE TO COVER DAMAGES.

    Clinical trials or marketing of any of our current and potential products
may expose us to liability claims from the use of these products. We currently
carry product liability insurance. However, we cannot be certain that we will be
able to maintain insurance on acceptable terms for clinical and commercial
activities or that the insurance would be sufficient to cover any potential
product liability claim or recall. If we fail to have sufficient coverage, our
business, results of operations and cash flows could be adversely affected.

IF WE ARE UNABLE TO COMPLY WITH ENVIRONMENTAL LAWS AND REGULATIONS, OUR BUSINESS
MAY BE HARMED.

    We are subject to federal, state and local laws and regulations governing
the use, manufacture, storage, handling and disposal of hazardous materials and
waste products. We currently maintain a

                                       11
<PAGE>
supply of several hazardous materials at our facilities. In the event of an
accident, we could be held liable for any damages that result, and the liability
could exceed our resources. While we currently outsource our research and
development programs involving the controlled use of biohazardous materials, if
in the future we conduct these programs, we might be required to incur
significant cost to comply with environmental laws and regulations.

THE REDEMPTION OF OUR OUTSTANDING PUBLIC WARRANTS MAY CAUSE THE PRICE OF OUR
COMMON STOCK TO FALL AND MAY RESULT IN DILUTION.

    On September 20, 1999, we issued a notice of redemption of warrants for the
purchase of shares of our common stock that we issued in connection with our
initial public offering. These warrants enable the holder to purchase shares of
our common stock at a price of $9.00 per share. As of January 31, 2000, there
were 3,062,452 of such warrants outstanding. We will redeem the warrants that
are outstanding as of April 16, 2000 at a price of $0.25 per share. We expect
that holders of the warrants will choose to exercise these warrants rather than
have them redeemed if the price of our common stock trades above $9.00 per share
during the period immediately preceding April 16, 2000. If these holders elect
to sell the common stock issued upon exercise of the warrants, the price of our
common stock may fall.

    Our issuance of common stock at a price of $9.00 per share may result in
dilution to other holders of common stock and may cause the price of our common
stock to fall. In addition, if the price of our common stock for the 30 day
trading period following April 16, 2000 is less than $19.46, or in some cases
$17.56, we may be required to issue additional shares of common stock to
investors that bought our common stock in privately negotiated transactions in
September 1999. Any such issuance would have a dilutive effect on holders of our
common stock.

ANTI-TAKEOVER PROVISIONS MAY PREVENT YOU FROM REALIZING A PREMIUM RETURN.

    Anti-takeover provisions of our certificate of incorporation and bylaws make
it more difficult for a third party to acquire us, even if doing so would be
beneficial to our stockholders. These provisions include:

    - authorization of the issuance of up to 2,000,000 shares of our preferred
      stock;

    - elimination of cumulative voting; and

    - elimination of stockholder action by written consent.

    Our bylaws establish procedures, including notice procedures, with regard to
the nomination, other than by or at the direction of our board of directors, of
candidates for election as directors or for stockholder proposals to be
submitted at stockholder meetings.

    We are also subject to Section 203 of the Delaware General Corporation Law,
an anti-takeover provision. In general, Section 203 of the Delaware General
Corporation Law prevents a stockholder owning 15% or more of a corporation's
outstanding voting stock from engaging in business combinations with a Delaware
corporation for three years following the date the stockholder acquired 15% or
more of a corporation's outstanding voting stock. This restriction is subject to
exceptions, including the approval of the board of directors and of the holders
of at least two-thirds of the outstanding shares of voting stock not owned by
the interested stockholder.

    These provisions are expected to discourage different types of coercive
takeover practices and inadequate takeover bids and to encourage persons seeking
to acquire control of our company to first negotiate with us.

    We believe that the benefits of increased protection of our potential
ability to negotiate with the proponents of unfriendly or unsolicited proposals
to acquire or restructure us outweigh the

                                       12
<PAGE>
disadvantages of discouraging those proposals because, among other things,
negotiation of those proposals could result in an improvement of their terms.

BECAUSE CURRENT OFFICERS, DIRECTORS, AND ABBOTT OWN A LARGE PERCENTAGE OF OUR
STOCK, THESE STOCKHOLDERS MAY BE ABLE TO CONTROL US AND ALSO PREVENT POTENTIALLY
BENEFICIAL ACQUISITIONS OF OUR COMPANY BY OTHERS.

    As of January 31, 2000, our officers, directors, Abbott and their affiliates
owned approximately 20% of the outstanding shares of our common stock, not
including stock issuable upon exercise of options or warrants. If these
stockholders were to exercise all of their options and warrants, they would
collectively own a majority of our common stock. These stockholders, if acting
together, may be able to influence the election of our directors and other
matters requiring approval by our stockholders. This concentration of ownership
may also delay or prevent a third party from acquiring us. These stockholders
may have interests that differ from our other stockholders, particularly in the
context of potentially beneficial acquisitions of our company by others. For
example, to the extent that these stockholders are our employees, they may be
less inclined to vote for acquisitions of our company by others involving the
termination of their employment or diminution of their responsibilities or
compensation.

THE TRADING PRICE OF OUR COMMON STOCK HAS BEEN VOLATILE AND MAY FLUCTUATE DUE TO
FACTORS BEYOND OUR CONTROL.

    The trading price of our common stock is subject to significant fluctuations
in response to numerous factors, including:

    - variations in anticipated or actual results of operations;

    - announcements of new products or technological innovations by competitors;

    - FDA approval or rejection of pending applications and regulatory
      enforcement actions;

    - changes in earnings estimates of operational results by analysts; and

    - results of clinical trials.

Moreover, the stock market from time to time has experienced extreme price and
volume fluctuations, which have particularly affected the market prices for
emerging growth companies and which have often been unrelated to the operating
performance of these companies. These broad market fluctuations may adversely
affect the market price of our common stock. During the past two years from the
date of this prospectus, the market price per share of our common stock has
fluctuated between approximately $5.125 and $58.50.

OUR MANAGEMENT WILL HAVE BROAD DISCRETION AS TO THE USE OF PROCEEDS OF THIS
OFFERING.

    Our management will have broad discretion regarding how we use the net
proceeds of the offering. Investors will be relying on the judgment of
management regarding the application of the proceeds of the offering. The result
and effectiveness of our use of the proceeds are uncertain.

                                       13
<PAGE>
                   NOTE REGARDING FORWARD-LOOKING STATEMENTS

    This prospectus contains certain forward-looking statements within the
meaning of Section 27A of the Securities Act of 1933 and Section 21E of the
Securities Exchange Act of 1934. Forward-looking statements deal with our
current plans, intentions, beliefs and expectations and statements of future
economic performance. Statements containing terms such as "believe," "do not
believe," "plan," "expect," "intend," "estimate," "anticipate" and other phrases
of similar meaning are considered to contain uncertainty and are forward-looking
statements.

    Forward looking statements involve known and unknown risks and uncertainties
which may cause our actual results in future periods to differ materially from
what is currently anticipated. We make cautionary statements in certain sections
of this prospectus, including under "Risk Factors." You should read these
cautionary statements as being applicable to all related forward-looking
statements wherever they appear in:

    - this prospectus and materials referred to in this prospectus;

    - the materials incorporated by reference into this prospectus; and

    - our press releases.

No forward-looking statement is a guarantee of future performance and you should
not place undue reliance on any forward-looking statement.

                                       14
<PAGE>
                                USE OF PROCEEDS

    We expect to receive net proceeds of approximately $   million from the sale
of 2,000,000 shares of common stock by us, based on an assumed public offering
price of $    per share and after deducting the underwriting discounts and
estimated offering expenses. We will receive no proceeds from shares sold by the
selling stockholders.

    We will retain broad discretion in the allocation of the net proceeds of
this offering. We currently intend to use the proceeds from this offering:

    - for research and development activities, including expansion of clinical
      trials;

    - to enhance sales and marketing efforts in the advance of the potential
      launch of rubitecan;

    - to finance possible acquisitions of complimentary products, technologies
      or businesses;

    - to improve facilities and potentially enhance manufacturing capabilities;
      and

    - for working capital and other general corporate purposes.

We cannot determine the cost, timing and amount of funds required for such
purposes at this time. The amounts and timing of these expenditures will vary
depending upon a number of factors, including the amount of net cash used in our
operations, competitive and technological developments, and the rate of growth,
if any, of our business. Pending such uses, we intend to invest the net proceeds
of this offering in interest bearing, investment grade securities.

                                       15
<PAGE>
                        PRICE RANGE OF OUR COMMON STOCK

    Our common stock trades on the Nasdaq National Market under the symbol
"SUPG." The following table sets forth the high and low bid information for our
common stock for each quarterly period in the two most recent fiscal years as
reported on the Nasdaq National Market:

<TABLE>
<CAPTION>
                                                                HIGH       LOW
                                                              --------   --------
<S>                                                           <C>        <C>
1998
Quarter ended March 31, 1998................................   $15.13     $11.69
Quarter ended June 30, 1998.................................    17.75       9.63
Quarter ended September 30, 1998............................    12.50       5.13
Quarter ended December 31, 1998.............................     9.31       5.38

1999
Quarter ended March 31, 1999................................   $12.38     $ 8.19
Quarter ended June 30, 1999.................................    19.38      10.25
Quarter ended September 30, 1999............................    24.00      14.81
Quarter ended December 31, 1999.............................    34.75      21.25

2000
Quarter ended March 31, 2000 (through February 8, 2000).....   $58.06     $27.50
</TABLE>

    On February 8, 2000, the last reported sale price for our common stock on
the Nasdaq National Market was $52.38 per share. As of January 31, 2000, there
were 537 holders of record of our common stock.

    We also have one class of warrants trading on the Nasdaq National Market
under the symbol "SUPGW," and one class of warrants trading on the Nasdaq
Smallcap Market under the symbol "SUPGZ." The SUPGW warrants have an exercise
price of $9.00 per share and the SUPGZ warrants have an exercise price of $18.18
per share. We will redeem any outstanding SUPGW warrants on April 16, 2000 and
the SUPGZ warrants will expire on August 12, 2001. On February 8, 2000, the last
reported sale price for the SUPGW warrants was $42.75, and the last sale price
for the SUPGZ warrants was $34.00.

                                DIVIDEND POLICY

    We have never paid cash dividends on our capital stock and do not expect to
pay any dividends in the foreseeable future. We intend to retain future
earnings, if any, for use in our business.

                                       16
<PAGE>
                                 CAPITALIZATION

    The following table sets forth our actual capitalization as of
September 30, 1999. Our capitalization is also presented:

    - on a pro forma basis to reflect the sale of 933,394 shares of common stock
      to Abbott in January 2000 with proceeds of $26.5 million; and

    - on a pro forma as adjusted basis to reflect the sale by us of 2,000,000
      shares of common stock in this offering, at an assumed public offering
      price of $    per share less estimated underwriting discounts and
      estimated offering expenses to be paid by us.

    You should read this information together with the consolidated financial
statements and the notes to these statements appearing elsewhere in this
prospectus.

<TABLE>
<CAPTION>
                                                                       SEPTEMBER 30, 1999
                                                               (IN THOUSANDS, EXCEPT SHARE DATA)
                                                              ------------------------------------
                                                                                      PRO FORMA AS
                                                               ACTUAL     PRO FORMA     ADJUSTED
                                                              ---------   ---------   ------------
<S>                                                           <C>         <C>         <C>
Long-term debt..............................................  $     --    $     --      $     --
Stockholders' equity:
    Preferred stock, $0.001 par value; 2,000,000 shares
      authorized; none outstanding..........................        --          --            --
    Common stock, $0.001 par value; 40,000,000 shares
      authorized; 24,749,736 shares issued and outstanding,
      actual; 25,683,130 shares issued and outstanding, pro
      forma; 27,683,130 shares issued and outstanding, pro
      forma as adjusted.....................................        25          26            28
    Additional paid-in capital..............................   128,777     155,276
    Deferred compensation...................................      (892)       (892)         (892)

    Accumulated other comprehensive loss....................      (106)       (106)         (106)

    Accumulated deficit.....................................   (84,273)    (84,273)      (84,273)
                                                              --------    --------      --------
        Total stockholders' equity (deficit)................    43,531      70,031
                                                              --------    --------      --------
            Total capitalization............................  $ 43,531    $ 70,031      $
                                                              ========    ========      ========
</TABLE>

                                       17
<PAGE>
                                    BUSINESS

OVERVIEW

    We are an emerging pharmaceutical company dedicated to the acquisition,
rapid development and commercialization of oncology therapies for solid tumors
and hematological malignancies. We seek to minimize the time, expense and
technical risk associated with drug commercialization by identifying and
acquiring pharmaceutical compounds in the later stages of development, rather
than committing significant resources to the research phase of drug discovery.

STRATEGY

    Our primary objective is to become a leading supplier of oncology therapies
for solid tumors and hematological malignancies. Key elements of our strategy
include:

    - LICENSING OR BUYING RIGHTS TO LEAD COMPOUNDS RATHER THAN ENGAGING IN PURE
      DISCOVERY RESEARCH. We identify and seek to license or buy rights to
      products or compounds that are typically in human clinical development. We
      then seek to enhance and complete the product development and bring the
      product to market. We believe that our approach minimizes the significant
      financial investment required by pure discovery research and reduces the
      risk of failure in developing a commercially viable product.

    - CAPITALIZING ON OUR EXISTING CLINICAL EXPERTISE TO MAXIMIZE THE COMMERCIAL
      VALUE OF OUR PRODUCTS. We intend to retain significant participation in
      the commercialization of our proprietary products by funding and
      undertaking human clinical development ourselves. We believe this will
      allow us to maximize the commercial value of our products by either
      directly marketing our products or licensing the products on more
      favorable terms than would be available earlier in the development cycle.
      Our management and clinical staff have significant experience in
      developing oncology therapies and bringing products to market.

    - UTILIZING TECHNOLOGIES TO DEVELOP PRODUCTS FOR IMPROVED DELIVERY AND
      ADMINISTRATION OF EXISTING COMPOUNDS. We are focused on the application of
      our technologies to the development of improved formulations of existing
      anticancer agents, which will be marketed as brand name pharmaceuticals.
      We believe that incorporating our technologies with these compounds will
      result in products with improved delivery and/or administration. The
      development of these products is subject to the New Drug Application, or
      NDA, approval process.

    - EXPANDING THE SCOPE OF OUR DEVELOPMENT EFFORTS IN ONCOLOGY. We are
      implementing a strategy to commercialize oncology products in a number of
      therapies, such as immunotherapies and vaccines, photodynamic therapy and
      biotechnology-based drugs, and other areas, such as diagnostic agents and
      prophylaxis.

                                       18
<PAGE>
PRODUCTS AND PRODUCTS IN DEVELOPMENT

    The following table outlines our products and products in development, their
indication or intended use, their therapeutic category and their regulatory
status:

<TABLE>
<CAPTION>
COMPOUND             INDICATION OR INTENDED USE            THERAPEUTIC CATEGORY    REGULATORY STATUS
- --------             --------------------------            --------------------    -----------------
<S>                  <C>                                   <C>                     <C>
Rubitecan            Pancreatic                            Cancer                  Phase III
                     Myelodysplastic syndromes/Chronic     Cancer                  Phase II
                       myelo-monocytic leukemia
                     Various other solid tumor cancers     Cancer                  Phase II

Nipent               Hairy cell leukemia                   Cancer                  Approved
                     Cutaneous T-cell lymphoma/            Cancer                  Phase II
                       Percutaneous T-cell lymphoma
                     Chronic lymphocytic leukemia          Cancer                  Phase II
                     Low grade non-Hodgkins lymphoma       Cancer                  Phase II
                     Graft-versus-host disease             Immunological           Phase I
                     Rheumatoid arthritis                  Immunological           Phase I

Decitabine           Myelodysplastic syndromes             Cancer                  Phase II
                     Acute myeloid leukemia/Chronic        Cancer                  Phase II
                       myeloid leukemia
                     Non-small cell lung                   Cancer                  Phase I/II
                     Sickle cell anemia                    Hematological           Phase I

RF1010               Anemia                                Hematological           Phase II

RF1051               Diabetes/Obesity                      Metabolic               Phase II

PZG                  Diabetes                              Metabolic               Phase II
</TABLE>

ONCOLOGY PRODUCTS AND PRODUCTS IN DEVELOPMENT

    RUBITECAN

    Rubitecan is an oral chemotherapy compound in the camptothecin class which
we licensed from the Stehlin Foundation for Cancer Research in 1997. Rubitecan
is a second-generation topoisomerase I inhibitor that causes single-strand
breaks in the DNA of rapidly dividing tumor cells. We believe that rubitecan may
have significant advantages over many existing anticancer drugs, including oral
dosing and a superior side effect profile. In particular, we believe that the
compound causes significantly less inhibition of bone marrow function, due in
part to its dosing schedule, which provides for a cycle of five days of
administration followed by two days of recovery. In clinical trials, the
observed side effects are mild to moderate hematological toxicities, low-grade
cystitis, infrequent and mild hair loss and gastrointestinal disorders. Finally,
as an oral drug that can be taken at home, rubitecan may provide patients with
additional convenience and improved quality of life, and may reduce healthcare
costs. We believe that rubitecan is a platform drug for leadership in the
treatment of a broad array of solid tumors and hematological malignancies. We
are seeking rapid development of rubitecan and hope to obtain expedited review
by the FDA of the drug for pancreatic cancer, for which there are limited
treatment options. In addition to patent protection, we have orphan drug
designation for this disease which may provide us with seven years of marketing
exclusivity in the United States after FDA approval.

                                       19
<PAGE>
    PANCREATIC CANCER

    Pancreatic cancer is associated with high patient mortality, causing more
than 75,000 deaths annually in the United States and Europe. It is the fourth
leading cause of death by cancer in the United States with an average survival
time of four to five months following diagnosis. The current therapeutic
treatment options most commonly used to treat pancreatic cancer include
5-fluorouracil, or 5-FU, and Gemzar.

    Results of a Phase II clinical trial conducted by the Stehlin Foundation
using rubitecan for treatment of pancreatic cancer indicate a favorable
comparison with historical treatment options in terms of quality of life,
survival data and tumor size reduction. The results of this Phase II trial
suggest that the median survival in the 60 evaluable patients who took at least
the required minimum eight week course of therapy was nearly nine months,
markedly greater than the average survival time of four to five months under
historical treatment methods. Overall, previously untreated patients who used
rubitecan survived much longer than those patients treated with Gemzar.

    We are evaluating rubitecan in three separate stand-alone pivotal Phase III
clinical trials for pancreatic cancer. The trials are randomized, unblinded
studies being conducted in approximately 200 centers and are designed to include
up to 1,800 patients. The primary endpoint of these trials is survival. We
commenced these trials in November 1998 and we have over 700 patients currently
enrolled. If any one of these trials is successful, we anticipate filing an NDA
with the FDA by early 2001. The protocols are outlined as follows:

<TABLE>
<CAPTION>
                         PROTOCOLS                            MAXIMUM PATIENTS
- ------------------------------------------------------------  ----------------
<S>                                                           <C>
Rubitecan or Gemzar in patients who have not undergone
  chemotherapy                                                      1,000
Rubitecan or 5-FU in patients who have failed Gemzar                  400
Rubitecan or other therapies in patients who have failed
  other prior therapies                                               400
</TABLE>

    MYELODYSPLASTIC SYNDROMES

    Myelodysplastic syndromes, or MDS, are a group of conditions that have in
common abnormalities in the blood-producing cells of the bone marrow. The
conditions are fatal, although patients can live for several years after
diagnosis. Treatment of patients with MDS has generally proven disappointing.
The most common current treatment is management by supportive measures, such as
blood transfusion, or the administration of antibiotics to fight infections.
Hematopoietic growth factors also have been used to treat MDS.

    We are conducting a Phase II study at the M.D. Anderson Cancer Center
enrolling patients with a diagnosis of MDS, as well as related conditions such
as chronic myeloid leukemia, or CML, and chronic myelo-monocytic leukemia. We
expect to enroll approximately 100 patients in this trial. Based on preliminary
positive results from this study, we are finalizing the protocol of a randomized
Phase III study comparing rubitecan to best supportive care. We expect to
commence patient enrollment for this study in the second quarter of 2000. The
principal endpoints will be response and clinical benefit. This planned Phase
III trial is designed to secure approval for this indication.

    OTHER POTENTIAL INDICATIONS

    Studies have shown rubitecan to be active in more than 30 human and animal
tumor models in indications such as breast, lung, colorectal, ovarian and
prostate cancers. We are aggressively pursuing additional Phase II trials using
rubitecan both as a single therapeutic agent and in combination with other
anticancer agents in solid tumors and hematological malignancies. We intend to
make available to physicians copies of peer-reviewed medical journal articles
and other validated scientific information related to these trials. We believe
this will provide physicians with more up-to-date product information and will
better enable them to meet their patients' medical needs.

    In addition, we are currently conducting pilot studies using rubitecan in
combination with other chemo-therapeutic agents. In studies to date, rubitecan
has not exhibited any of the cardiac, pulmonary, hepatic or renal toxicities
that limit the acute and/or chronic dosages of several chemotherapeutics. In
addition, some early studies suggest rubitecan could be used to treat cancer on
a chronic rather than acute basis.

                                       20
<PAGE>
    In December 1999, we entered into licensing and research agreements with the
Clayton Foundation for Research and its technology transfer organization,
Research Development Foundation. Under the terms of the agreements, we acquired
worldwide rights to inhaled versions of formulations of camptothecins, including
rubitecan. Phase I clinical studies with inhaled rubitecan for the treatment of
lung cancer and pulmonary metastatic disease are currently underway at the M.D.
Anderson Cancer Center and the Baylor College of Medicine.

    NIPENT

    Nipent, generically known as pentostatin, inhibits a key enzyme in the DNA
synthesis process and results in cytotoxicity, primarily in lymphocytes. The
specific mechanism differs from other chemotherapy agents, therefore making
Nipent novel and unique. Nipent's preferential effect on lymphocytes, with
little effect on other normal tissue, creates an interest in this product for
the treatment of cancers of the lymphoid system and other hematologic cancers.

    HAIRY CELL LEUKEMIA

    We acquired Nipent from the Parke-Davis division of the Warner-Lambert
Company in 1996 and we are selling this drug in the United States for the
treatment of hairy cell leukemia, a type of B-lymphocytic leukemia.
Warner-Lambert retained a worldwide, royalty-free license to sell Nipent but has
agreed not to sell Nipent in North America through September 2006. In 1997,
Warner-Lambert further agreed to buy Nipent from us for all of its sales outside
the United States through at least October 2004. We are permitted to sell Nipent
outside of North America for diseases other than cancer until September 2006, at
which time we may sell the drug worldwide for any disease.

    OTHER INDICATIONS

    We believe that Nipent has a unique mechanism of action and Phase II trials
indicate that it may have activity in a variety of other hematologic cancers. In
oncology, we are pursuing treatments for lymphatic malignancies and disorders,
such as cutaneous T-cell lymphoma, chronic lymphocytic leukemia, low grade
non-Hodgkin's lymphoma and prolymphocytic leukemia. Nipent has received orphan
drug designation by the FDA for use against cutaneous T-cell lymphoma and
chronic lymphocytic leukemia. As with rubitecan, we are pursuing trials that
will lead to peer reviewed articles indicating efficacy of Nipent in various
leukemias.

    In addition, Nipent has shown activity in various autoimmune diseases,
including graft-versus-host disease which is not responsive to standard
therapies, and rheumatoid arthritis. We estimate the United States markets for
both graft-versus-host disease and rheumatoid arthritis are larger than the
market for Nipent's current applications. We are conducting Phase I clinical
trials in both of these indications. If results from ongoing trials are
consistent with previously completed trials, we intend to pursue development of
Nipent for both of these diseases.

    DECITABINE

    Decitabine is an antimetabolite cytotoxic agent that we acquired from a
subsidiary of Teva Pharmaceuticals in September 1999. Decitabine is a pyrimidine
analog that has a mechanism of action that is unique from other chemically
related compounds, such as gemcitabine and cytosine arabinoside. Decitabine's
mechanism is related to DNA hypomethylation. Methylation of DNA is a major
mechanism regulating gene expression. Researchers have determined that an
increase in methylation of DNA results in blocking the activity of several genes
that regulate cell division and differentiation, known as "suppressor genes."
With suppressor genes blocked, cell division becomes unregulated, causing
cancer. In studies researchers have demonstrated that decitabine reduces the
methylation of DNA, leading to reexpression of suppressor genes and a resulting
redifferentiation and maturation of

                                       21
<PAGE>
the cancer cells back to normal. Researchers have also shown that decitabine
treatment restores sensitivity of tumors to treatment by drugs such as cisplatin
and doxorubicin by reversing drug resistance due to excessive methylation of
DNA.

    Researchers have shown decitabine to be effective in multiple Phase II
trials in the United States and Europe for treating MDS, CML and acute myeloid
leukemia. Based on positive results from these studies, we are finalizing the
protocol of a randomized Phase III study comparing decitabine to best supportive
care for MDS. We expect to commence patient enrollment for this study in 2000.
The principal endpoints will be response and clinical benefit. This planned
Phase III trial is designed to secure approval for this indication. Decitabine
has received orphan drug designation from the FDA for MDS.

    In addition to MDS, clinical studies have shown that decitabine is effective
in a variety of other hematological malignancies such as acute myeloid leukemia
and CML. Preliminary results also suggest activity in solid tumors such as
non-small cell lung cancer. Phase I clinical trials with decitabine are underway
for this indication. Scientific data also suggests that decitabine may be
applicable for treatment of non malignant diseases such as sickle cell anemia.
Phase I clinical trials are underway for treatment of sickle cell anemia using
decitabine.

NON-ONCOLOGY PROPRIETARY PRODUCTS

    We are developing certain non-oncology products, including RF 1010, RF 1051
and pyrazinoylguanidine, or PZG. RF 1010 is an analog of a naturally occurring
human non-androgenic hormone. We have conducted Phase II trials using RF 1010 to
treat various forms of anemia and neutropenia. These diseases destroy red and
white blood cells and thereby weaken the immune system, leaving patients
susceptible to infections that could result in serious illness or death.
RF 1051, which is a naturally occurring substance in humans, has applications
for treatment of diabetes and obesity. Our Phase II trials have indicated that
this proprietary oral drug may cause the body to store less fat or use more fat
to produce energy. We have received orphan drug designation for RF 1051 in the
treatment of Prader-Willi Syndrome, a type of genetic obesity. PZG is a product
for treatment of Type II, or adult-onset, diabetes. Animal studies and early
clinical studies of PZG suggest that it may help to control the blood sugar and
lipid abnormalities of diabetes, and may have utility in treating a lipid
disorder unrelated to diabetes called hypertriglyceridemia, obesity,
hypertension and the uremia of renal failure. We recently initiated a small,
well-defined and controlled Phase II study to characterize the hypoglycemic and
lipid-lowering effects of PZG in Type II diabetics.

TECHNOLOGIES

    We are focused on the application of our technologies to the development of
improved formulations of existing anticancer agents, which will be marketed as
brand name pharmaceuticals. We believe that incorporating our technologies with
these compounds will result in products with improved delivery and/or
administration. The development of these products is subject to the NDA approval
process.

EXTRA TECHNOLOGY

    We have developed several applications for our proprietary Extra technology.
We believe this technology significantly improves the safety profile and
handling characteristics of several anticancer drugs currently on the market. In
March 1994, we acquired exclusive worldwide rights to the patented cyclodextrin
technology used in our Extra technology from Janssen Biotech, N.V. and others.

                                       22
<PAGE>
    Many generic anticancer drugs are available only in a powder form that must
be mixed into a solution before injection into a vein. If successful, our Extra
technology will produce a ready-to-inject, stable solution that will ease
administration and save time by eliminating the potentially dangerous mixing
procedure. It could also provide safety benefits for those administering the
dose by reducing their risk of exposure to the drug. Moreover, we believe that
our ready-to-inject stable solutions may have a significantly longer shelf life
at room temperature than the mixed solutions. In addition, many existing
anticancer pharmaceuticals, including those under development by us, are potent
toxins that can cause serious irreversible damage to a patient's muscle or skin
should the drug accidentally leak during injection. We believe that our Extra
technology may increase the safety of these existing anticancer drugs by
shielding the tissue from the drug at the injection site. The drug is released
upon circulation within the bloodstream. We believe that each of these features
will result in our Extra products having a significant competitive advantage
over their counterparts currently on the market.

    EXTRA PRODUCTS UNDER DEVELOPMENT

    We filed an NDA for Mito Extra, our Extra formulation of mitomycin, in
December 1997, which was accepted by the FDA in February 1998. We are in the
process of responding to an FDA request for additional formulation,
manufacturing and clinical information. In addition, we are evaluating our Extra
technology for additional applications of other generic anticancer agents as
well as Nipent.

SPARTAJECT DRUG DELIVERY TECHNOLOGY

    Spartaject drug delivery technology is a drug delivery system that
accommodates poorly water-soluble and water insoluble compounds by encapsulating
them with a fatty layer, known as a phospholipid. The Spartaject technology
involves coating particles of a drug that are of submicron or near micron size
with a membrane-forming phospholipid layer, thereby permitting the creation of a
suspension of the drug rather than a solution, and its intravenous injection
without the use of potentially toxic solubilizing agents. As a result, the
Spartaject technology may reduce toxicity created by other injectable forms of
delivery and potentially increase efficacy by facilitating delivery of compounds
whose prior intravenous delivery was impractical because of solubility-related
formulation difficulties.

    SPARTAJECT PRODUCT UNDER DEVELOPMENT

    Busulfan is currently marketed in an oral dosage form by Glaxo
Wellcome Inc. It is frequently used "off-label" as a bone marrow ablating agent
prior to bone marrow transplants. In 1998 we completed a Phase I clinical trial
of Spartaject busulfan at each of Johns Hopkins Oncology Center and Duke
University Medical Center. Additional Phase I clinical trials in pediatric bone
marrow ablation and neoplastic meningitis were initiated at St. Jude's
Children's Hospital and Duke University Medical Center.

ORAL PRODRUG DELIVERY TECHNOLOGY

    Oral prodrug delivery technology involves administering an inactive
compound, known as a prodrug, which is absorbed in the digestive tract and is
converted to an active agent in the liver by an enzyme located there. Oral
prodrug delivery technology could potentially enable the oral delivery of drugs
that are otherwise only used in an intravenous formulation. The resulting active
compounds may pass through the systemic circulation and act at peripheral sites.
We are applying the Oral prodrug delivery technology to compounds selected for
their potential either to serve as oral delivery agents for systemically active
chemotherapeutic or radiosensitizing drugs previously available only in
intravenous form.

                                       23
<PAGE>
    ORAL PRODRUG DELIVERY PRODUCTS

    5-FP, or 5-fluoro pyrimidinone, is a pyrimidinone based prodrug that is
converted to 5-FU, or 5-fluorouracil, by the liver. 5-FU is currently sold
generically only in an intravenous form. It is widely used in the treatment of
breast, colorectal and other cancers. We have completed a Phase I trial with
5-FP and are evaluating strategies regarding its further clinical development.

    IPdR is a pyrimidinone based prodrug that converts into IUdR, a compound
that has been under investigation by the National Cancer Institute, or NCI, in
animals and humans as a potential agent to sensitize cancer cells to radiation.
We were recently awarded a Phase II Small Business Innovation Research Grant by
the NCI of up to approximately $750,000, which is designated to be used to bring
IPdR into Phase I trials.

GENERIC ANTICANCER DRUGS

    As part of our Extra product development efforts we pursued development of
generic versions of existing anticancer agents. To date we have received
Abbreviated New Drug Application, or ANDA, approval for our generic mitomycin,
which we are selling in the United States. We believe that the total estimated
United States sales for generic anticancer products have decreased over the last
few years due to increased competition. We also believe sales for these generics
may continue to decrease as a result of competitive factors. These factors may
include reductions in the per unit sales price, the introduction of additional
generics as well as other cancer drugs, new formulations for these drugs and the
use of different therapies. Therefore, we currently intend to limit our
development of generic products to those that we feel either require minimal
effort to submit an ANDA and obtain marketing clearance or that offer
significant market opportunities.

STRATEGIC AND COLLABORATIVE RELATIONSHIPS

    We identify and license or buy rights to products or compounds that are
typically in human clinical development. We then seek to enhance and complete
the product development and bring the product to market internally or through
collaborations with others. We have entered into a variety of strategic
relationships and licensing agreements in pursuing our business. Some of our
more significant relationships are as follows:

ABBOTT LABORATORIES

    In December 1999, we entered into agreements with Abbott under which Abbott
will undertake to market and distribute our products and invest in shares of our
common stock. One of the agreements covers the development, marketing and
distribution of rubitecan. Under this agreement, we will co-promote rubitecan
with Abbott within the United States and Abbott has exclusive rights to market
rubitecan outside the United States. In the U.S. market, we will share profits
from product sales equally with Abbott. Outside of the U.S. market, Abbott will
pay us royalties and transfer fees based on product sales. We will remain
responsible for pursuing and funding the clinical development of rubitecan and
to obtain regulatory approval of the product in the United States, Canada and
the member states of the European Union. Abbott is responsible for obtaining
regulatory approval of the product in the other countries in the world. We will
retain responsibility for manufacturing, packaging, sterilization and labeling
of the product and Abbott shall be the exclusive distributor of the product
throughout the world.

    In addition, under the agreements Abbott will purchase shares of our common
stock in an amount of up to $81.5 million in nine tranches over a period of time
and will make certain other cash payments to us which, when aggregated with the
equity investments, amount to approximately $150 million. The purchase price of
the securities will be determined based on the market price of our common stock
at the time of the purchase. Each equity investment and cash payment is tied to
and conditioned upon the

                                       24
<PAGE>
achievement of certain milestones based on, among other things, steps in the
regulatory approval process both in the United States and other countries in the
international territory, the launch of the product in particular territories and
the target sales of the product. In January 2000 Abbott made a $26.5 million
equity investment and a $5 million cash payment under the terms of our
agreements.

    We also granted Abbott an option to purchase up to 49% of the outstanding
shares of our common stock at an exercise price of $85 per share, which expires
in 2003. Abbott's ability to exercise the option is conditioned upon, among
other things, the continued effectiveness of the worldwide distribution
agreement for rubitecan-related products. In addition Abbott has a right of
first discussion with respect to our product portfolio and a right of first
refusal to acquire us.

    Under a separate distribution agreement, Abbott will become the exclusive
U.S. distributor for Nipent. We retain U.S. marketing rights for Nipent.

STEHLIN FOUNDATION FOR CANCER RESEARCH

    In September 1997 we licensed the exclusive worldwide royalty-bearing rights
to rubitecan from the Stehlin Foundation for Cancer Research, a Houston, Texas
based cancer research clinic. The Stehlin Foundation was established in 1969 by
Dr. John S. Stehlin, Jr. M.D., a surgical oncologist, for the express purpose of
conducting basic research that can be applied directly to improving the
treatment of patients with cancer. All research is clinically oriented and
conducted at the Stehlin Foundation's facility in Houston, Texas. In
November 1999 we amended our agreement with the Stehlin Foundation to broaden
the definition of licensed compounds to include certain analogues of rubitecan.
Under these agreements we are required to seek commercial applications for
rubitecan. We are required to pay the Stehlin Foundation approximately
$10 million for research and must make cash royalty payments and cash or stock
milestone payments to the Stehlin Foundation as we develop and commercialize
rubitecan.

NEW DRUG DEVELOPMENT AND APPROVAL PROCESS

    Regulation by governmental authorities in the United States and other
countries is a significant factor in the manufacture and marketing of
pharmaceuticals and in our ongoing research and development activities. All of
our products will require regulatory approval by governmental agencies prior to
commercialization. In particular, human therapeutic products are subject to
rigorous preclinical testing and clinical trials and other pre-marketing
approval requirements by the FDA and regulatory authorities in other countries.
In the United States, various federal, and in some cases state statutes and
regulations also govern or impact upon the manufacturing, safety, labeling,
storage, record-keeping and marketing of such products. The lengthy process of
seeking required approvals and the continuing need for compliance with
applicable statutes and regulations, require the expenditure of substantial
resources. Regulatory approval, when and if obtained, may be limited in scope
which may significantly limit the indicated uses for which a product may be
marketed. Further, approved drugs, as well as their manufacturers, are subject
to ongoing review and discovery of previously unknown problems with such
products may result in restrictions on their manufacture, sale or use or in
their withdrawal from the market.

    The process for new drug approval has many steps, including:

    DRUG DISCOVERY.  In the initial stages of drug discovery before a compound
reaches the laboratory, tens of thousands of potential compounds are randomly
screened for activity against an assay assumed to be predictive for particular
disease targets. This drug discovery process can take several years. Once a
company locates a "screening lead", or starting point for drug development,
isolation and structural determination may begin. The development process
results in numerous chemical modifications to the screening lead in an attempt
to improve the drug properties of the lead. After a compound emerges from this
process, the next steps are to conduct further preliminary studies on the
mechanism of action,

                                       25
<PAGE>
further in vitro, or test tube, screening against particular disease targets and
finally, some in vivo, or animal, screening. If the compound passes these
barriers, the toxic effects of the compound are analyzed by performing
preliminary exploratory animal toxicology. If the results demonstrate acceptable
levels of toxicity, the compound emerges from the basic research mode and moves
into the preclinical phase.

    PRECLINICAL TESTING.  During the preclinical testing stage, laboratory and
animal studies are conducted to show biological activity of the compound against
the targeted disease, and the compound is evaluated for safety. These tests
typically take approximately three and one-half years to complete, and must be
conducted in compliance with Good Laboratory Practice, or GLP, regulations.

    INVESTIGATIONAL NEW DRUG APPLICATION.  During the preclinical testing, an
IND is filed with the FDA to begin human testing of the drug. The IND becomes
effective if not rejected by the FDA within 30 days. The IND must indicate the
results of previous experiments, how, where and by whom the new studies will be
conducted, the chemical structure of the compound, the method by which it is
believed to work in the human body, any toxic effects of the compound found in
the animal studies and how the compound is manufactured. All clinical trials
must be conducted in accordance with Good Clinical Practice, or GCP,
regulations. In addition, an Institutional Review Board, or IRB, comprised of
physicians at the hospital or clinic where the proposed studies will be
conducted, must review and approve the IND. The IRB also continues to monitor
the study. Progress reports detailing the results of the clinical trials must be
submitted at least annually to the FDA. In addition, the FDA may, at any time
during the 30-day period or at any time thereafter, impose a clinical hold on
proposed or ongoing clinical trials. If the FDA imposes a clinical hold,
clinical trials cannot commence or recommence without FDA authorization and then
only under terms authorized by the FDA. In some instances, the IND application
process can result in substantial delay and expense.

    Some limited human clinical testing may be done under a Physician's IND in
support of an IND application and prior to receiving an IND. A Physician's IND
is an IND application that allows a single individual to conduct a clinical
trial. A Physician's IND does not replace the more formal IND process, but can
provide a preliminary indication as to whether further clinical trials are
warranted, and can, on occasion, facilitate the more formal IND process.

    Clinical trials are typically conducted in three sequential phases, but the
phases may overlap.

    PHASE I CLINICAL TRIALS.  After an IND becomes effective, Phase I human
clinical trials can begin. These tests, involving usually between 20 and 80
healthy volunteers or patients, typically take approximately one year to
complete. The tests study a drug's safety profile, and may include the safe
dosage range. The Phase I clinical studies also determine how a drug is
absorbed, distributed, metabolized and excreted by the body, and the duration of
its action. Phase I/II trials are normally conducted for anticancer product
candidates.

    PHASE II CLINICAL TRIALS.  In Phase II clinical trials, controlled studies
are conducted on approximately 100 to 300 volunteer patients with the targeted
disease. The primary purpose of these tests is to evaluate the effectiveness of
the drug on the volunteer patients as well as to determine if there are any side
effects. These studies generally take approximately two years, and may be
conducted concurrently with Phase I clinical trials. In addition, Phase I/II
clinical trials may be conducted to evaluate not only the efficacy of the drug
on the patient population, but also its safety.

    PHASE III CLINICAL TRIALS.  This phase typically lasts about three years and
usually involves 1,000 to 3,000 patients. During the Phase III clinical trials,
physicians monitor the patients to determine efficacy and to observe and report
any reactions that may result from long-term use of the drug.

    NEW DRUG APPLICATION.  After the completion of all three clinical trial
phases, if there is substantial evidence that the drug is safe and effective, an
NDA is filed with the FDA. The NDA must contain all

                                       26
<PAGE>
of the information on the drug gathered to that date, including data from the
clinical trials. NDAs are often over 100,000 pages in length.

    The FDA reviews all NDAs submitted before it accepts them for filing and may
request additional information rather than accepting an NDA for filing. In such
an event, the NDA must be resubmitted with the additional information and,
again, is subject to review before filing. Once the submission is accepted for
filing, the FDA begins an in-depth review of the NDA. Under the Federal Food,
Drug and Cosmetic Act, the FDA has 180 days in which to review the NDA and
respond to the applicant. The review process is often significantly extended by
FDA requests for additional information or clarification regarding information
already provided in the submission. The FDA may refer the application to an
appropriate advisory committee, typically a panel of clinicians, for review,
evaluation and a recommendation as to whether the application should be
approved. The FDA is not bound by the recommendation of an advisory committee.
If FDA evaluations of the NDA and the manufacturing facilities are favorable,
the FDA may issue either an approval letter or an approvable letter, which
usually contains a number of conditions that must be met in order to secure
final approval of the NDA. When and if those conditions have been met to the
FDA's satisfaction, the FDA will issue an approval letter, authorizing
commercial marketing of the drug for certain indications. If the FDA's
evaluation of the NDA submission or manufacturing facilities is not favorable,
the FDA may refuse to approve the NDA or issue a not approvable letter.

    MARKETING APPROVAL.  If the FDA approves the NDA, the drug becomes available
for physicians to prescribe. Periodic reports must be submitted to the FDA,
including descriptions of any adverse reactions reported. The FDA may request
additional studies (Phase IV) to evaluate long-term effects.

    PHASE IV CLINICAL TRIALS AND POST MARKETING STUDIES.  In addition to studies
requested by the FDA after approval, these trials and studies are conducted to
explore new indications. The purpose of these trials and studies and related
publications is to broaden the application and use of the drug and its
acceptance in the medical community.

    ORPHAN DRUG DESIGNATION.  The FDA may grant orphan drug designation to drugs
intended to treat a "rare disease or condition," which is generally a disease or
condition that affects fewer than 200,000 individuals in the United States.
Orphan drug designation must be requested before submitting a NDA. After the FDA
grants orphan drug designation, the generic identity of the therapeutic agent
and its potential orphan use are disclosed publicly by the FDA. Orphan drug
designation does not convey any advantage in, or shorten the duration of, the
regulatory review and approval process. If a product that has orphan drug
designation subsequently receives FDA approval for the indication for which it
has such designation, the product is entitled to orphan exclusivity, which means
the FDA may not approve any other applications to market the same drug for the
same indication, except in very limited circumstances, for seven years.
Rubitecan has received orphan drug designation from the FDA.

    APPROVALS OUTSIDE OF THE UNITED STATES.  Steps similar to those in the
United States must be undertaken in virtually every other country comprising the
market for our products before any such product can be commercialized in those
countries. The approval procedure and the time required for approval vary from
country to country and may involve additional testing. There can be no assurance
that approvals will be granted on a timely basis or at all. In addition,
regulatory approval of prices is required in most countries other than the
United States. There can be no assurance that the resulting prices would be
sufficient to generate an acceptable return to us.

FDA MODERNIZATION ACT OF 1997

    The Food and Drug Administration Modernization Act of 1997, or FDAMA, was
enacted, in part, to ensure the timely availability of safe and effective drugs,
biologics and medical devices by expediting the FDA review process for new
products. FDAMA establishes a statutory program for the approval of

                                       27
<PAGE>
"fast track products." The fast track provisions essentially codifies FDA's
Accelerated Approval regulations for drugs and biologics. A "fast track product"
is defined as a new drug or biologic intended for the treatment of a serious or
life-threatening condition that demonstrates the potential to address unmet
medical needs for such a condition. Under the new fast track program, the
sponsor of a new drug or biologic may request the FDA to designate the drug or
biologic as a "fast track product" at any time during the clinical development
of the product. FDAMA specifies that the FDA must determine if the product
qualifies for fast track designation within 60 days of receipt of the sponsor's
request. Approval of an NDA for a fast track product can be based on an effect
on a clinical endpoint or on a surrogate endpoint that is reasonably likely to
predict clinical benefit. Approval of a fast track product may be subject to
post-approval studies to validate the surrogate endpoint or confirm the effect
on the clinical endpoint, and prior review of copies of all promotional
materials. If a preliminary review of the clinical data suggests efficacy, the
FDA may initiate review of sections of an application for a "fast track product"
before the application is complete. This "rolling review" is available if the
applicant provides a schedule for submission of remaining information and pays
applicable user fees. However, the Prescription Drug User Fees Act time period
does not begin until the complete application is submitted.

    We intend to seek fast track designation to secure expedited review of
appropriate products. It is uncertain if fast track designation will be
obtained. We cannot predict the ultimate impact, if any, of the new fast track
process on the timing or likelihood of FDA approval of rubitecan or any of our
other potential products.

    Physicians may prescribe drugs for uses that are not described in the
product's labeling for uses that differ from those tested by us and approved by
the FDA. Such "off-label" uses are common across medical specialties and may
constitute the best treatment for many patients in varied circumstances. The FDA
does not regulate the behavior of physicians in their choice of treatments. The
FDA does, however, restrict manufacturer's communications on the subject of
off-label use. Companies cannot actively promote FDA-approved drugs for
off-label uses, but a recent court decision now allows them to disseminate to
physicians articles published in peer-reviewed journals, like THE NEW ENGLAND
JOURNAL OF MEDICINE, that discuss off-label uses of approved products. To the
extent allowed by law, we intend to disseminate peer-reviewed articles on our
products to our physician customers.

EXTRA DRUG DEVELOPMENT

    Each Extra product candidate contains an active drug substance which has
already been approved by the FDA and may already also have generic versions
approved by the FDA. The excipient for the Extra technology has also been
approved by the FDA in a non-oncology application. To gain approval to market,
we must provide data to the FDA to support the safety, efficacy and quality of
each Extra product, but these data may be more limited in scope and content than
would be required for a new chemical entity. While extensive clinical trials may
not be required, we will be required to provide clinical data that demonstrate
that the administration of our Extra formulation results in the same presence of
the drug in the body as that of the generic version, within clinically
acceptable statistical guidelines. Overall, the data packages we will submit to
the FDA for Extra product candidates may be smaller than a typical NDA and may
take less time to review.

    We also expect that, after the safety and quality of the Extra technology
have been adequately demonstrated to the FDA, future Extra submissions will be
able to cross-refer to these data, further streamlining our submissions.

GENERIC DRUG DEVELOPMENT

    For certain drugs that are generic versions of previously approved products,
there is an abbreviated FDA approval process. A sponsor may submit an
Abbreviated Application for:

                                       28
<PAGE>
    - a drug product that is the "same" as the drug product listed in the
      approved drug product list published by the FDA (the "listed drug") with
      respect to active ingredient(s), route of administration, dosage form,
      strength and conditions of use recommended in the labeling;

    - a drug product that differs with regard to certain changes from a listed
      drug if the FDA has approved a petition from a prospective applicant
      permitting the submission of an Abbreviated Application for the changed
      product; and

    - a drug that is a duplicate of, or meets the monograph for, an approved
      antibiotic drug.

    An Abbreviated Application need not contain the clinical and preclinical
data supporting the safety and effectiveness of the product. The applicant must
instead demonstrate that the product is bioequivalent to the listed drug. FDA
regulations define bioequivalence as the absence of a significant difference in
the rate and the extent to which the active ingredient moiety becomes available
at the site of drug action when administered at the same molar dose under
similar conditions in an appropriately designed study. If the approved generic
drug is both bioequivalent and pharmaceutically equivalent to the listed drug,
the agency may assign a code to the product in an FDA publication that will
represent a determination by the agency that the product is therapeutically
equivalent to the listed drug. This designation will be considered by third
parties in determining whether the generic drug will be utilized as an
alternative to the listed drug.

SALES AND MARKETING

    We currently have 18 employees focused on sales and marketing of our
products to approximately 1,700 hospitals in the United States. The large
majority of these hospitals are members of hospital buying groups. We have
focused our efforts on selling generic products to these groups since they
control a significant majority of the hospital business in the oncology and
blood disorder pharmaceutical market. We also market our products, including
Nipent, to private practice oncology clinics, oncology distributors and drug
wholesalers. Oncologists/hematologists, oncology nurses and oncology pharmacists
are included in each of these classes of customers.

    Since acceptance of our products from each buying group can be time
consuming, there may be significant delays before we can win bids and generate
sales revenue. However, we have taken significant steps toward product
acceptance. A large number of these buying groups, including Premier Purchasing
Partners, Novation, Kaiser Permanente, and the Department of Veteran Affairs,
have given us approved vendor status. In addition, we have gained recognition as
an approved vendor in each state that requires registration or licensing before
bidding for those customers. We will continue to target these large buying
groups and, as we attain market share, bid with other buying groups while
seeking to minimize any price erosion that may occur.

    There are approximately 5,000 private practice oncologists/hematologists in
the United States. These physicians usually purchase oncology products through
distributors, with whom we have developed relationships. The four major oncology
distributors in the United States are Oncology Therapeutic Network Joint
Venture, L.P., Florida Infusion Services, Inc., National Specialty
Services, Inc. and Priority Healthcare Corporation. These distributors control
approximately 60% of the private practice oncology clinics, which in turn
represent approximately 30% of the oncology-related pharmaceutical market. We
have taken significant steps in building relationships with these distributors,
all of which distribute Nipent. Our sales force will also continue to target the
important private practice oncology clinics within their assigned territories.
We also sell to large drug wholesalers that supply hospitals and hospital buying
groups.

                                       29
<PAGE>
    Our sales group is divided into three regions. Each region is headed by a
manager with extensive industry experience who supervises specialty oncology
sales representatives. We plan to expand our sales force upon receipt of
additional approvals of our products under development. Our sales and marketing
group conducts direct sales, sponsors speakers' programs, works with
distributors, performs market research analysis, develops marketing strategies,
creates and implements educational and promotional programs, establishes pricing
and product advertising and maintains compliance with hospital and other buying
groups.

MANUFACTURING

    We currently outsource manufacturing for all of our products to United
States and foreign suppliers. We expect to continue to outsource manufacturing
in the near term. We believe our current suppliers will be able to efficiently
manufacture our bulk proprietary and generic compounds in sufficient quantities
and on a timely basis, while maintaining product quality. We seek to maintain
quality control over manufacturing through ongoing inspections, rigorous review,
control over documented operating procedures and thorough analytical testing by
outside laboratories. We believe that our current strategy of outsourcing
manufacturing is cost-effective since we avoid the high fixed costs of plant,
equipment and large manufacturing staffs and conserve our resources.

    The FDA must issue marketing clearance and deem a manufacturer acceptable
under current GMP before production of bulk proprietary, finished
pharmaceuticals or generic compounds for commercial sale may begin. Once a bulk
proprietary or generic compound is manufactured on our behalf, it is sent to one
or more domestic manufacturers that process it into the finished proprietary,
Extra or generic dosage forms. We currently follow these procedures for our
marketed products, Nipent and mitomycin. We then ship our finished proprietary
and generic products to an outside vendor for distribution to our customers.

    We have entered agreements with a domestic entity for the future production
of our bulk generics required for both our Extra and generic dosage forms. We
have licensed from this manufacturer, on an exclusive basis, proprietary
fermentation technology for anticancer antibiotic agents. In the future, we may
adapt this proprietary fermentation technology to produce other bulk generics.

    In December 1997, we received approval from the FDA to commercially
manufacture Nipent at our designated vendors' manufacturing site using our
proprietary manufacturing process. We believe we own sufficient bulk inventory
for the manufacture of Nipent to meet our clinical and commercial needs for the
near future. In April 1998, the FDA approved our application for the production
of bulk mitomycin using the fermentation technology described above.

    We intend to continue evaluating our manufacturing requirements and may
establish or acquire our own facilities to manufacture our products for
commercial distribution if we feel doing so would reduce costs or improve
control and flexibility of product supply.

PATENTS AND PROPRIETARY TECHNOLOGY

    We actively pursue a policy of seeking patent protection for our proprietary
products and technologies, whether developed in-house or from outside
acquisition. We have acquired licenses to or assignments of numerous United
States patents covering certain of our proprietary drugs and have received or
licensed patents related to our Extra, Spartaject and Oral Prodrug technologies.

    In addition to pursuing patent protection in appropriate cases, we rely on
trade secret protection for our unpatented proprietary technology. We also
pursue a policy of having our employees and consultants execute proprietary
information agreements upon commencement of employment or consulting
relationships with us. These agreements provide that all confidential
information developed

                                       30
<PAGE>
or made known to the individual during the course of the relationship is
confidential except in specified circumstances.

COMPETITION

    There are many companies, both public and private, including well-known
pharmaceutical companies, that are engaged in the development and sale of
pharmaceutical products for some of the applications that we are pursuing. Our
competitors and probable competitors include Eli Lilly, Ortho-McNeil
Pharmaceutical, Amgen, Bristol-Myers Squibb and Immunex. These companies have
substantially greater financial, research and development, manufacturing and
marketing experience and resources than we do and represent substantial
long-term competition for us. These companies may succeed in developing
pharmaceutical products that are more effective or less costly than any we may
develop or market.

    Factors affecting competition in the pharmaceutical industry vary depending
on the extent to which the competitor is able to achieve a competitive advantage
based on proprietary technology. If we are able to establish and maintain a
significant proprietary position with respect to our proprietary products,
competition will likely depend primarily on the effectiveness of the product and
the number, gravity and severity of its unwanted side effects as compared to
alternative products. Companies compete with respect to generic products
primarily on price and, to a lesser extent, on name recognition and the
reputation of the manufacturer in its target markets. Moreover, the number of
competitors offering a particular generic product could dramatically affect
price and gross margin for that product or an Extra product based on that
generic product. We may be at a disadvantage in competing with more established
companies based on price or market reputation. In addition, increased
competition in a particular generic market would likely lead to significant
price erosion for our generic products and Extra products based on such generic
products. This would have a negative effect on our sales and potential gross
profit margins. For example, we believe that the total estimated United States
sales for our proposed generic products, and generic products upon which we
propose to base our Extra products, have decreased in recent years due to
increased competition. We believe that sales volumes and unit prices of these
generics may continue to decrease as a result of competitive factors. These
factors include the introduction of additional generics and other cancer drugs,
the desire of some companies to increase their market share, new formulations
for those drugs and the use of different therapies.

    Extensive research and development efforts and rapid technological progress
characterize the industry in which we compete. Although we believe that our
proprietary position may give us a competitive advantage with respect to our
proposed nongeneric drugs, we expect development of new products to continue.
Discoveries by others may render our current and potential products
noncompetitive. Our competitive position also depends on our ability to attract
and retain qualified scientific and other personnel, develop effective
proprietary products, implement development and marketing plans, obtain patent
protection and secure adequate capital resources.

EMPLOYEES

    As of January 31, 2000, we had 81 full-time employees, 40 of whom were
involved in research and development, including clinical activities. We use
consultants and temporary employees to complement our staffing. Our employees
are not subject to any collective bargaining agreements, and we regard our
relations with employees to be good.

LEGAL PROCEEDINGS

    We are not currently a party to any material legal proceedings.

                                       31
<PAGE>
                                   MANAGEMENT

    Our executive officers and their ages as of December 31, 1999 are as
follows:

<TABLE>
<CAPTION>
NAME                                          AGE                       POSITION
- ----                                        --------   ------------------------------------------
<S>                                         <C>        <C>
Joseph Rubinfeld, Ph.D....................     67      Chief Executive Officer, President and
                                                         Director

Edward L. Jacobs..........................     53      Executive Vice President, Commercial
                                                         Operations

Luigi Lenaz, M.D..........................     58      Senior Vice President of Clinical Research
                                                       and Medical Affairs

Rajesh C. Shrotriya, M.D..................     55      Executive Vice President and Chief
                                                       Scientific Officer

Ronald H. Spair...........................     44      Senior Vice President, Chief Financial
                                                       Officer and Secretary

Denis Burger, Ph.D........................     56      Director

Lawrence J. Ellison.......................     55      Director

Walter J. Lack............................     51      Director

Julius A. Vida, Ph.D......................     71      Director

Daniel Zurr, Ph.D.........................     54      Director
</TABLE>

    JOSEPH RUBINFELD, PH.D. co-founded the Company in 1991. He has served as
Chief Executive Officer, President, and a director of the Company since our
inception and was Chief Scientific Officer from inception until September 1997.
Dr. Rubinfeld was one of the four initial founders of Amgen in 1980 and served
as Vice President and Chief of Operations until 1983. From 1987 to 1990, he was
a Senior Director at Cetus Corporation. From 1968 to 1980, Dr. Rubinfeld was
employed at Bristol-Myers Company International Division in a variety of
positions, most recently as Vice President and Director of Research and
Development. While at Bristol-Myers, Dr. Rubinfeld was instrumental in licensing
the original anticancer line of products for Bristol-Myers, including Mitomycin
and Bleomycin. Before that time, Dr. Rubinfeld was a research scientist with
several pharmaceutical and consumer product companies including Schering-Plough
Corporation and Colgate-Palmolive Co. He received his B.S. in chemistry from
C.C.N.Y., and his M.A. and Ph.D. in chemistry from Columbia University.
Dr. Rubinfeld has numerous patents and/or publications on a wide range of
inventions and developments, including the 10-second developer for Polaroid
film, manufacture of cephalosporins and the first commercial synthetic
biodegradable detergent. In 1984, Dr. Rubinfeld received the Common Wealth Award
for Invention.

    EDWARD L. JACOBS became our Executive Vice President, Commercial Operations
in March 1999. Prior to joining us Mr. Jacobs served as Senior Vice President,
Commercial Operations at Sequus Pharmaceuticals, Inc. from November 1997 to
March 1999. Between January 1995 and November 1997, Mr. Jacobs served as
President and Chief Executive Officer of Trilex Pharmaceuticals Inc., now Titan
Pharmaceuticals. Prior to his association with Trilex, Mr. Jacobs served in a
variety of senior management positions with pharmaceutical companies, including
Chief Executive at Transplant Therapeutics Inc., Vice President and General
Manager of Syncor International Inc., Vice President at NEORX Corporation,
Business Director of Pharmacia and Upjohn (Adria Labs, Inc.), and Johnson &
Johnson (McNeil). Mr. Jacobs received a B.A. in Political Science/Journalism
from California State University at Northridge.

                                       32
<PAGE>
    LUIGI LENAZ, M.D. has served as our Senior Vice President of Clinical
Research and Medical Affairs since October 1997. Before joining us, he was
Senior Medical Director, Oncology Franchise Management for Bristol-Myers Squibb
from 1990 to 1997 and was Director, Scientific Affairs, Anti-Cancer for
Bristol-Myers Squibb from 1978 to 1990. Dr. Lenaz was a Post Doctoral Fellow at
both the Memorial Sloan-Kettering Cancer Center in New York and the National
Cancer Institute in Milan, Italy. He received his medical training at the
University of Bologna Medical School in Bologna, Italy.

    RAJESH C. SHROTRIYA, M.D. has served as our Executive Vice President and
Chief Scientific Officer since October 1997 and as Senior Vice President and
Special Assistant to the President from January 1997 to September 1997. Before
joining us, Dr. Shrotriya was Vice President and Chief Medical Officer of MGI
Pharma, Inc., an oncology company, from August 1994 to October 1996. Previously
he spent 18 years at Bristol-Myers Squibb in a variety of positions most
recently as Executive Director, Worldwide CNS Clinical Research. Dr. Shrotriya
received his medical training in India at Grant Medical College in Bombay, Delhi
University and the Armed Forces Medical College in Poona.

    RONALD H. SPAIR became our Senior Vice President and Chief Financial Officer
in August 1999. Prior to joining us, Mr. Spair was Chief Financial Officer of
Sparta Pharmaceuticals, Inc., a development stage pharmaceutical company, from
March 1996 until August 1999. He has worked in the biotechnology industry since
1990. From October 1993 until March 1996, Mr. Spair served as Vice President and
Chief Financial Officer of Lexin Pharmaceutical Corporation, a development stage
biopharmaceutical company. Before joining Lexin, Mr. Spair served as Vice
President, Chief Financial Officer and Assistant Secretary of Envirogen, Inc.,
an environmental biotechnology company, from May 1990 to August 1993. Mr. Spair
received a B.S. in Accounting and an M.B.A. from Rider College. He is a licensed
Certified Public Accountant in New Jersey.

    DENIS BURGER, PH.D. has served as a member of our board of directors since
January 1996. Dr. Burger has served as President and Chief Operating Officer of
AVI BioPharma, Inc. (formerly AntiVirals, Inc.) a biotechnology company
specializing in gene-targeted therapeutic products and cancer immunotherapy
since February 1992 and as Chief Executive Officer since February 1996.
Dr. Burger was a co-founder of Epitope, Inc., a biotechnology company, and
served as its Chairman from 1981 until 1990. He has also been the general
partner of Sovereign Ventures, LLC, a biotechnology consulting and merchant
banking venture since 1991. Dr. Burger is a member of the Board of Directors of
AVI BioPharma, Inc. and Trinity Biotech, PLC. He received his B.A. in
Bacteriology and Immunology from the University of California, Berkeley, and his
M.S. and Ph.D. in Microbiology and Immunology from the University of Arizona,
Tucson.

    LAWRENCE J. ELLISON has been a member of our board of directors since
June 1997. Mr. Ellison is Chief Executive Officer and Chairman of the Board of
Directors of Oracle Corporation, a company he founded in May 1977. Mr. Ellison
is co-chairman of California's Council on Information Technology and is a member
of the Board of Directors of Apple Computer, Inc., a computer hardware company,
Liberate Technologies, a computer software company and Spring Group.

    WALTER J. LACK has served as a director of the Company since February 2000.
Mr. Lack is a partner of Engstrom, Lipscomb & Lack, a Los Angeles, California
law firm that he founded in 1974. Mr. Lack has acted as a special arbitrator for
the Superior Court of the State of California since 1976 and for the American
Arbitration Association since 1979. He is a member of the International Academy
of Trial Lawyers and an Advocate of the American Board of Trial Advocates.
Mr. Lack also serves as a director of HCC Insurance Holdings, Inc.,
Microvision Inc. and Spectrum Laboratories, Inc.

    JULIUS A. VIDA, PH.D. has served as a member of our board of directors since
January 1996. Since June 1993, Dr. Vida has served as President of Vida
International Pharmaceutical Consultants. From 1976 to May 1993, Dr. Vida worked
at Bristol-Myers, where he served as Vice President of Business Development,
Licensing and Strategic Planning from 1991 to 1993, as Vice President of
Licensing from 1985 to 1991 and as Director of Licensing from 1982 to 1985.
Dr. Vida is a member of the Board of

                                       33
<PAGE>
Directors of Biomatrix, Inc. and Medarex, Inc., both biotechnology companies.
Dr. Vida received his Ph.D. in Chemistry from Carnegie Mellon University and his
M.B.A. from Columbia University.

    DANIEL ZURR, PH.D. has been a member of our board of directors since
January 1994. Dr. Zurr currently serves as President and Chief Executive Officer
of Quark Biotech, Inc. (formerly Expression Systems, Inc.). Dr. Zurr served as
Scientific Director and Business Development Director of the Pharmaceutical
Division of Israel Chemicals, Ltd., an Israeli limited liability company, from
1984 to 1985. He also served as Director of Licensing at G.D. Searle & Company,
Limited, from 1980 to 1983. He was Chief Executive Officer of Plantex-Ikapharm,
an Israeli pharmaceutical company, from 1975 to 1980. Dr. Zurr received his
M.Sc. at the Hebrew University of Jerusalem and his Ph.D. from the Imperial
College University of London in 1972.

BOARD COMMITTEES

    Our board of directors currently has two standing committees, an Audit
Committee and a Compensation Committee. The Audit Committee is composed of
Mr. Lack, Dr. Vida and Dr. Zurr, and the Compensation Committee is composed of
Mr. Lack, Dr. Burger and Dr. Zurr. We have no nominating committee or committee
performing similar functions.

    AUDIT COMMITTEE. The Audit Committee monitors our corporate financial
reporting and our internal and external audits. This committee reports to the
board the results of its examinations and provides recommendations based on its
findings. The functions of this committee include tracking our progress in
responding to its recommended improvements, evaluating our internal accounting
controls, nominating independent auditors, and apprising the board of any
significant financial matters that require board attention. The Audit Committee
held one meeting during 1999.

    COMPENSATION COMMITTEE. The Compensation Committee reviews our executive
compensation policy, including equity compensation for our senior executive
officers, and makes recommendations to the board regarding such matters. The
Compensation Committee met one time during 1999.

                                       34
<PAGE>
                              SELLING STOCKHOLDERS

    The following table sets forth information for each selling stockholder, as
of January 31, 2000. Beneficial ownership is determined in accordance with SEC
rules and includes securities that the selling stockholder has the right to
acquire within 60 days after January 31, 2000. The information does not
necessarily indicate beneficial ownership for any other purpose. Except as
otherwise indicated, we believe that the selling stockholders have sole voting
and investment power with respect to all shares of the common stock shown as
beneficially owned by them, subject to community property laws where applicable.
Joseph Rubinfeld is our Chief Executive Officer, President and chairman of our
board of directors and Lawrence J. Ellison, the beneficial owner of Tako
Ventures LLC, is one of our directors.

<TABLE>
<CAPTION>
                                          SHARES OF COMMON STOCK                    SHARES OF COMMON STOCK
                                            BENEFICIALLY OWNED                     TO BE BENEFICIALLY OWNED
                                              BEFORE OFFERING                         AFTER OFFERING(1)
                                          -----------------------   SHARES TO BE   ------------------------
NAME                                        NUMBER     PERCENTAGE     OFFERED        NUMBER      PERCENTAGE
- ----                                      ----------   ----------   ------------   -----------   ----------
<S>                                       <C>          <C>          <C>            <C>           <C>
Tako Ventures LLC (2)...................  4,493,683       15.3%       650,000       3,843,683       12.2%
Joseph Rubinfeld (3)....................  2,734,607        9.5%        50,000       2,684,607        8.8%
</TABLE>

- ------------------------

(1) Excludes shares that may be sold pursuant to the underwriters' exercise of
    their over-allotment option.

(2) Includes 1,775,000 shares of common stock issuable upon exercise of
    immediately exercisable warrants. If the underwriters fully exercise their
    over-allotment option, Tako Ventures LLC will sell an additional 305,000
    shares resulting in its beneficial ownership after the offering being
    3,538,683 shares or 11.3% of the shares of our common stock outstanding
    after the offering.

(3) Includes 1,694,500 shares held jointly by Joseph and Loretta Rubinfeld,
    husband and wife, 20,000 shares held individually by Joseph Rubinfeld,
    35,000 shares held by Joseph and Loretta Rubinfeld as custodians under the
    California Uniform Transfers to Minors Act, 976,666 shares issuable upon
    exercise of options to purchase shares of common stock exercisable by Joseph
    Rubinfeld at March 31, 2000, and options to purchase 8,441 shares of common
    stock exercisable by Loretta Rubinfeld at March 31, 2000. If the
    underwriters fully exercise their over-allotment option, Dr. Rubinfeld will
    sell an additional 100,000 shares resulting in his beneficial ownership
    after the offering being 2,584,607 shares or 8.4% of the shares of our
    common stock outstanding after the offering.

                                       35
<PAGE>
                          DESCRIPTION OF CAPITAL STOCK

    Our authorized capital stock consists of 40,000,000 shares of common stock
and 2,000,000 shares of preferred stock. Immediately after the offering, based
on shares outstanding as of January 31, 2000, we estimate there will be
29,654,757 shares of common stock issued and outstanding and no shares of
preferred stock issued and outstanding.

COMMON STOCK

    Holders of our common stock are entitled to one vote per share on all
matters to be voted upon by the stockholders. Stockholders may not cumulate
votes in connection with the election of directors. Our common stock has no
preemptive or conversion rights or other subscription rights. There are no
redemption or sinking fund provisions applicable to our common stock. All
outstanding shares of common stock are fully paid and non-assessable, and the
shares of common stock to be outstanding upon completion of the offering will be
fully paid and non-assessable.

PREFERRED STOCK

    Our board has the authority, subject to limitations prescribed by law, to
issue these shares of preferred stock in one or more series, to fix the rights,
preferences, privileges and restrictions, qualifications and limitations
(including, without limitation, dividend rates, conversion rights, voting
rights, rights and terms of redemption, sinking fund provisions and liquidation
preferences) granted to or imposed upon any unissued and undesignated shares of
preferred stock and to fix the number of shares constituting any series and the
designations of those series, without any further vote or action by the
stockholders (subject to applicable stock exchange rules).

WARRANTS

    At January 31, 2000, warrants to purchase the following shares of our common
stock were outstanding:

<TABLE>
<CAPTION>
                                        NUMBER OF SHARES   EXERCISE PRICE    ISSUE DATE   EXPIRATION DATE
                                        ----------------   ---------------   ----------   ---------------
<S>                                     <C>                <C>               <C>          <C>
PUBLIC................................     3,062,452       $          9.00      1996               2001
                                             211,725                 18.18      1999               2001

PRIVATE...............................        93,050       $          5.00      1995               2000
                                              13,350                  7.20      1996               2001
                                           1,045,000                 13.50      1997               2007
                                             230,000                 10.35      1997               2007
                                             500,000                 11.00      1998               2004
                                           1,143,575        12.00 - 655.31      1999        2001 - 2004

TOTAL.................................     6,299,152
</TABLE>

    In addition, upon exercise, the holders of the warrants to purchase 13,350
shares will receive an additional warrant to acquire 13,350 shares at $9.00 per
share. These additional warrants will expire in 2001.

    On September 20, 1999, we issued a notice of redemption of our publicly
traded $9.00 warrants. As of January 31, 2000, there were 3,062,452 of such
warrants outstanding. We will redeem any of these warrants that are still
outstanding as of April 16, 2000 at a price of $0.25 per share. We expect that
holders of the warrants will choose to exercise these warrants rather than have
them redeemed if the price of our common stock trades above $9.00 per share
during the period immediately preceding April 16, 2000.

                                       36
<PAGE>
    We can redeem the $5.00 warrants for $0.25 each upon 30 days written notice,
if the closing bid price exceeds $10.00 for specified periods of time.

ANTI-TAKEOVER PROVISIONS

    The provisions of Delaware law, our certificate of incorporation and our
bylaws described below may have the effect of delaying, deferring or
discouraging another person from acquiring control of our company.

DELAWARE LAW

    We are subject to the provisions of Section 203 of the Delaware General
Corporation Law regulating corporate takeovers. This section prevents certain
Delaware corporations from engaging, under limited circumstances, in a "business
combination," which includes a merger or sale of more than 10% of the
corporation's assets, with any "interested stockholder," which is defined to
include a stockholder who owns 15% or more of the corporation's outstanding
voting stock, as well as affiliates and associates of such stockholder, for
three years following the date that the stockholder became an "interested
stockholder" unless:

    - the transaction is approved by the board prior to the date the "interested
      stockholder" attained that status;

    - upon the closing of the transaction that resulted in the stockholder's
      becoming an "interested stockholder," the "interested stockholder" owned
      at least 85% of the voting stock of the corporation outstanding at the
      time the transaction commenced; or

    - on or subsequent to the date the "business combination" is approved by the
      board and authorized at an annual or special meeting of stockholders by at
      least two-thirds of the outstanding voting stock that is not owned by the
      "interested stockholder."

    A Delaware corporation may "opt out" of this provision with an express
provision in its original certificate of incorporation or an express provision
in its certificate of incorporation or bylaws resulting from a stockholders'
amendment approved by at least a majority of the outstanding voting shares.
However, we have not "opted out" of this provision. Section 203 could prohibit
or delay mergers or other takeover or change-in-control attempts and,
accordingly, may discourage attempts to acquire us.

BYLAW PROVISIONS

    Our bylaws provide that any action required or permitted to be taken by our
stockholders at an annual meeting or a special meeting of the stockholders may
only be taken if it is properly brought before the meeting. Our stockholders may
not take any action by written consent instead of by a meeting. Our certificate
of incorporation provides that our board of directors may issue preferred stock
with voting or other rights without stockholder action.

    Our bylaws provide that we will indemnify officers and directors against
losses that they may incur in investigations and legal proceedings resulting
from their services to us, which may include services in connection with
takeover defense measures. These provisions may have the effect of preventing
changes in our management.

TRANSFER AGENT AND REGISTRAR

    Chase Mellon Shareholder Services serves our transfer agent and registrar of
our common stock.

LISTING

    Our common stock is quoted on the Nasdaq National Market under the symbol
"SUPG."

                                       37
<PAGE>
                                  UNDERWRITING

    We and the selling stockholders are offering the shares of common stock
described in this prospectus through a number of underwriters. Banc of America
Securities LLC, Lehman Brothers Inc., Prudential Securities Incorporated and
Warburg Dillon Read LLC are the representatives of the underwriters. We and the
selling stockholders have entered into an underwriting agreement with the
representatives. Subject to the terms and conditions of the underwriting
agreement, we and the selling stockholders have agreed to sell to the
underwriters, and each underwriter has separately agreed to purchase, the number
of shares of common stock listed next to its name below at the public offering
price, less the underwriting discounts and commissions described on the cover
page of the prospectus:

<TABLE>
<CAPTION>
UNDERWRITER                                                   NUMBER OF SHARES
- -----------                                                   ----------------
<S>                                                           <C>
Banc of America Securities LLC..............................
Lehman Brothers Inc.........................................
Prudential Securities Incorporated..........................
Warburg Dillon Read LLC.....................................
                                                                 ---------
    Total...................................................     2,700,000
                                                                 =========
</TABLE>

    The underwriting agreement is subject to a number of terms and conditions
and provides that the underwriters must buy all of the shares if they buy any of
them. The underwriters will sell the shares to the public when and if the
underwriters buy the shares from us and the selling stockholders.

    The underwriters initially will offer the shares to the public at the price
specified on the cover page of this prospectus. The underwriters may allow
selected dealers a concession of not more than $               per share. The
underwriters may also allow, and any other dealers may reallow, a concession of
not more than $               per share to some other dealers. If all the shares
are not sold at the public offering price, the underwriters may change the
public offering price and the other selling terms. No change in the public
offering price will vary the proceeds to be received by us as specified on the
cover page of this prospectus. The common stock is offered subject to a number
of conditions, including:

    - the receipt and acceptance of the common stock by the underwriters; and

    - the right on the part of the underwriters to reject orders in whole or in
      part.

    The selling stockholders have granted the underwriters an option to buy up
to 405,000 additional shares of common stock. These additional shares would
cover sales of shares by the underwriters that exceed the number of shares
specified in the table above. The underwriters may exercise this option at any
time within 30 days after the date of the prospectus. If the underwriters
exercise this option, they will each purchase, subject to a number of terms and
conditions, additional shares approximately in proportion to the amounts
specified above. If purchased, the underwriters will offer such additional
shares on the same terms as those on which the 2,700,000 shares are being
offered.

    The following table shows the per share and total underwriting discounts and
commissions to be paid to the underwriters. These amounts are shown assuming no
exercise and full exercise of the underwriters' option to purchase additional
shares:

<TABLE>
<CAPTION>
                                                       NO EXERCISE   FULL EXERCISE
                                                       -----------   -------------
<S>                                                    <C>           <C>
Per share underwriting discounts and commissions.....    $              $
Total underwriting discounts and commissions to be
  paid by us.........................................    $              $
Total underwriting discounts and commissions to be
  paid by the selling stockholders...................    $              $
</TABLE>

                                       38
<PAGE>
    The expenses of this offering, not including the underwriting discounts and
commissions, are estimated to be approximately $                     and will be
paid by us and the selling stockholders. Expenses of this offering, exclusive of
the underwriting discounts and commissions, include the SEC filing fee, the NASD
filing fee, Nasdaq listing fees, printing expenses, transfer agent and
registration and other miscellaneous fees.

    We, our executive officers and directors, certain of our stockholders and
the selling stockholders have entered into lock-up agreements with the
underwriters. Under these agreements, subject to exceptions, we may not issue
any new shares of common stock, and our executive officers and directors,
certain shareholders and the selling stockholders may not offer, sell, contract
to sell or otherwise dispose of or hedge any common stock or securities
convertible into or exchangeable for shares of common stock. These restrictions
will be in effect for a period of 60 days after the date of the prospectus for
us, our executive officers and directors (other than those who are selling
stockholders) and certain of our stockholders, and for a period of 90 days after
the date of the prospectus for the selling stockholders. At any time and without
notice, Banc of America Securities LLC may, in its sole discretion, release all
or some of the securities from these lock-up agreements.

    We and the selling stockholders will indemnify the underwriters against some
liabilities, including some liabilities under the Securities Act. If we or the
selling stockholders are unable to provide this indemnification, we and the
selling stockholders will contribute to payments the underwriters may be
required to make in respect of those liabilities.

    One or more of the underwriters may facilitate the marketing of this
offering online, either directly or through one or more of their affiliates. In
those cases, prospective investors may view offering terms and a prospectus
online and, depending upon the particular underwriter, place orders online or
through their financial advisors.

    In our September 1999 round of private financing, an affiliate of Lehman
Brothers, Inc., one of the underwriters, purchased from us 170,843 shares of
common stock at an effective price of $17.56 per share and warrants to purchase
common stock at exercise prices ranging from $22.50 to $60 per share. The Lehman
Brothers affiliate invested on the same terms as the other investors in that
offering. Lehman Brothers, Inc. was not involved as a placement agent or in any
other capacity in that offering. In addition, our decision to call the initial
public offering warrants for redemption gives the investors in that offering,
including the Lehman Brothers affiliate, the anti-dilution right to receive
additional newly-issued shares of our common stock if the average closing price
of our common stock for the 30 days following redemption falls below $17.56 per
share.

    In connection with the offering, the underwriters may engage in activities
that stabilize, maintain or otherwise affect the price of the common stock.
These transactions may include:

    - short sales;

    - over-allotment;

    - purchases to cover positions created by short sales; and

    - stabilizing transactions.

    Short sales involve the sale by the underwriters of a greater number of
shares than they are required to purchase in the offering. In order to cover a
short position, the underwriters may bid for purchase shares of common stock in
the open market or may exercise their over-allotment option. Stabilizing
transactions consist of bids or purchases made for the purpose of preventing or
retarding a decline in the market price of the common stock while the offering
is in progress.

    The underwriters may also impose a penalty bid. This means that if the
representatives purchase shares in the open market in stabilizing transactions
or to cover short sales, the representatives can

                                       39
<PAGE>
require the underwriters that sold those shares as part of this offering to
repay the underwriting discounts and commissions received by them.

    As a result of these activities, the price of the common stock may be higher
than the price that otherwise might exist in the open market. If the
underwriters commence these activities, they may discontinue them at any time.
The underwriters may carry out these transactions on the Nasdaq National Market,
in the over-the-counter market or otherwise.

    The underwriters do not expect sales to discretionary accounts to exceed 5%
of the total number of shares of common stock offered by the prospectus.

    In connection with the offering, some underwriters and any selling group
members who are qualified market makers on the Nasdaq National Market may engage
in passive market making transactions in the common stock on the Nasdaq National
Market in accordance with Rule 103 of Regulation M. Rule 103 permits passive
market making during the period when Regulation M would otherwise prohibit
market activity by the participants in this offering. Passive market making may
occur during the business day before the pricing of this offering, before the
commencement of offers or sales of the common stock. Passive market makers must
comply with applicable volume and price limitations and must be identified as a
passive market maker. In general, a passive market maker must display its bid at
a price not in excess of the highest independent bid for the security. If all
independent bids are lowered below the passive market maker's bid, however, the
bid must then be lowered when purchase limits are exceeded. Net purchases by a
passive market maker on each day are limited to a specified percentage of the
passive market maker's average daily trading volume in the common stock during a
specified period and must be discontinued when such limit is reached.
Underwriters and dealers are not required to engage in passive market making and
may end passive market making activities at any time.

                                 LEGAL MATTERS

    The validity of the issuance of common stock will be passed upon for us by
Wilson Sonsini Goodrich & Rosati, P.C., Palo Alto, California. Certain legal
matters will be passed upon for the underwriters by O'Melveny & Myers LLP, San
Francisco, California.

                                    EXPERTS

    Ernst & Young LLP, independent auditors, have audited our consolidated
financial statements included in our Annual Report on Form 10-K for the year
ended December 31, 1998, as set forth in their report, which is incorporated by
reference in this prospectus and elsewhere in the registration statement. Our
financial statements are incorporated by reference in reliance on Ernst & Young
LLP's report, given on their authority as experts in accounting and auditing.

    The consolidated financial statements of Sparta Pharmaceuticals, Inc., one
of our wholly-owned subsidiaries, included in our report on Form 8-K dated
August 26, 1999, have been audited by Arthur Andersen LLP, independent public
accountants, as indicated in their report with respect thereto, and are
incorporated herein by reference in reliance upon the authority of said firm as
experts in giving said reports. Reference is made to said report, which includes
an explanatory paragraph with respect to the uncertainty regarding Sparta's
ability to continue as a going concern as discussed in Note 1 to the financial
statements.

                                       40
<PAGE>
                      WHERE YOU CAN FIND MORE INFORMATION

    We file annual, quarterly and special reports, proxy statements and other
information with the SEC. Our filings are available to the public over the
internet at the SEC's web site at http://www.sec.gov. You may also read and copy
any document we file at the SEC's Public Reference Rooms in Washington, D.C.,
New York, New York and Chicago, Illinois. The Public Reference Room in
Washington D.C. is located at 450 Fifth Street, N.W. Please call the SEC at
1-800-SEC-0330 for further information on the Public Reference Rooms.
Information concerning us is also available for inspection at the offices of the
Nasdaq National Market, Reports Section, 1735 K Street, N.W., Washington, D.C.
20006.

    The SEC allows us to "incorporate by reference" the information we file with
it, which means that we can disclose important information to you by referring
you to those documents. The information incorporated by reference is an
important part of this prospectus, and information that we file later with the
SEC will automatically update and supersede this information. We incorporate by
reference the documents listed below and any future filings made with the SEC
under Sections 13(a), 13(c), 14, or 15(d) of the Securities Exchange Act of 1934
after the date of this prospectus until the termination of the offering:

    - Our Annual Report on Form 10-K for the fiscal year ended December 31,
      1998;

    - Amendment No. 1 to our Annual Report on Form 10-K for the fiscal year
      ended December 31, 1998;

    - Our Quarterly Report on Form 10-Q for the quarter ended March 31, 1999;

    - Quarterly Report on Form 10-Q for the quarter ended June 30, 1999;

    - Quarterly Report on Form 10-Q for the quarter ended September 30, 1999;

    - Proxy Statement for our 1999 Annual Meeting of Stockholders;

    - The description of our common stock contained in our registration
      statement on Form 8-A, filed on January 18, 1996, including any amendment
      or report filed for the purpose of updating the description;

    - The description of our acquisition of Sparta Pharmaceuticals, Inc. on
      August 12, 1999, contained in our Current Report on Form 8-K filed on
      August 26, 1999, and Form 8 K/A filed on October 13, 1999;

    - The description of our warant redemption call contained in our Current
      Report on Form 8-K filed on October 4, 1999;

    - The description of our agreements entered into with Abbott Laboratories on
      December 21, 1999 contained in our current report on Form 8-K filed on
      December 23, 1999, and Form 8K/A filed on January 7, 2000; and

    - All other reports filed in accordance with Section 13(a) or 15(d) of the
      Securities Exchange Act of 1934 since December 31, 1998.

    This prospectus is part of a registration statement on Form S-3 filed with
the SEC under the Securities Act of 1933. This prospectus does not contain all
of the information set forth in the

                                       41
<PAGE>
registration statement. You should read the registration statement for further
information about us and our common stock. You may request a copy of these
filings at no cost. Please direct your requests to:

    SuperGen, Inc.
    Two Annabel Lane, Suite 220
    San Ramon, California 94583
    Attn: Investor Relations
    (925) 327-0200

    You should rely only on the information incorporated by reference or
provided in this prospectus or any prospectus supplement. We have not authorized
anyone else to provide you with different information. You should not assume
that the information in this prospectus or any prospectus supplement is accurate
as of any date other than the date on the front page of those documents.

                                       42
<PAGE>
- ------------------------------------------------------------
- ------------------------------------------------------------

                                2,700,000 SHARES

                                     [LOGO]
                                ----------------

                                   PROSPECTUS

                                         , 2000

                            ------------------------

                         BANC OF AMERICA SECURITIES LLC
                                LEHMAN BROTHERS
                          PRUDENTIAL VECTOR HEALTHCARE
                        A UNIT OF PRUDENTIAL SECURITIES
                            WARBURG DILLON READ LLC
                                ----------------

    Until             , 2000, all dealers that buy, sell or trade the common
stock may be required to deliver a prospectus, regardless or whether they are
participating in the offering. This is in addition to the dealers' obligation to
deliver a prospectus when acting as underwriters and with respect to their
unsold allotments or subscriptions.

- ------------------------------------------------------------
- ------------------------------------------------------------
<PAGE>
                                    PART II

                     INFORMATION NOT REQUIRED IN PROSPECTUS

ITEM 14. OTHER EXPENSES OF ISSUANCE AND DISTRIBUTION.

    The registrant will pay all reasonable expenses incident to the registration
of the shares other than any commissions and discounts of underwriters, dealers
or agents. Such expenses are set forth in the following table. All of the
amounts shown are estimates except the SEC registration fee and NASD filing fee.

<TABLE>
<CAPTION>
                                                              AMOUNT TO BE PAID
                                                              -----------------
<S>                                                           <C>
SEC registration fee........................................      $ 38,732
NASD filing fee.............................................      $ 15,171
Nasdaq National Market listing fee..........................      $ 17,500
Legal fees and expenses.....................................      $250,000
Accounting fees and expense.................................      $ 50,000
Printing and engraving......................................      $175,000
Transfer agent fees.........................................      $  5,000
Miscellaneous expenses......................................      $108,597
                                                                  --------
Total.......................................................      $660,000
                                                                  ========
</TABLE>

ITEM 15. INDEMNIFICATION OF DIRECTORS AND OFFICERS.

    As permitted by Section 145 of the Delaware General Corporation Law, the
registrant's amended and restated certificate of incorporation includes a
provision that eliminates the personal liability of its directors for monetary
damages for breach or alleged breach of their duty of care. In addition, as
permitted by Section 145 of the Delaware General Corporation Law, the bylaws of
the registrant provide that: (1) the registrant is required to indemnify its
directors and executive officers and persons serving in such capacities in other
business enterprises at the registrant's request, to the fullest extent
permitted by Delaware law, including in those circumstances in which
indemnification would otherwise be discretionary; (2) the registrant may, in its
discretion, indemnify employees and agents in those circumstances where
indemnification is not required by law; (3) the registrant is required to
advance expenses, as incurred, to its directors and executive officers in
connection with defending a proceeding, except that it is not required to
advance expenses to a person against whom the registrant brings a claim for
breach of the duty of loyalty, failure to act in good faith, intentional
misconduct, knowing violation of law or deriving an improper personal benefit;
(4) the rights conferred in the bylaws are not exclusive, and the registrant is
authorized to enter into indemnification agreements with its directors,
executive officers and employees; and (5) the registrant may not retroactively
amend the bylaw provisions in a way that it adverse to such directors, executive
officers and employees in these matters.

    The registrant's policy is to enter into indemnification agreements with
each of its directors and executive officers that provide the maximum indemnity
allowed to directors and executive officers by Section 145 of the Delaware
General Corporation Law and the bylaws, as well as certain additional procedural
protections. In addition, such indemnification agreements provide that the
registrant's directors and executive officers will be indemnified to the fullest
possible extent not prohibited by law against all expenses, including attorney's
fees, and settlement amounts paid or incurred by them in any action or
proceeding, including any derivative action by or in the right of the
registrant, on account of their services as directors or executive officers of
the registrant or as directors or officers of any other company or enterprise
when they are serving in such capacities at the request of the registrant. The
registrant will not be obligated pursuant to the indemnification agreements to
indemnify or advance expenses to an indemnified party with respect to
proceedings or claims initiated by the indemnified

                                      II-1
<PAGE>
party and not by way of defense, except with respect to proceedings specifically
authorized by the registrant's board of directors or brought to enforce a right
to indemnification under the indemnification agreement, the registrant's bylaws
or any statute or law. Under the agreements, the registrant is not obligated to
indemnify the indemnified party (1) for any expenses incurred by the indemnified
party with respect to any proceeding instituted by the indemnified party to
enforce or interpret the agreement, if a court of competent jurisdiction
determines that each of the material assertions made by the indemnified party in
such proceeding was not made in good faith or was frivolous; (2) for any amounts
paid in settlement of a proceeding unless the registrant consents to such
settlement; (3) with respect to any proceeding brought by the registrant against
the indemnified party for willful misconduct, unless a court determines that
each of such claims was not made in good faith or was frivolous; (4) on account
of any suit in which judgment is rendered against the indemnified party for an
accounting of profits made from the purchase or sale by the indemnified party of
securities of the registrant pursuant to the provisions of Section16(b) of the
Securities Exchange Act of 1934, and related laws; (5) on account of the
indemnified party's conduct which is finally adjudged to have been knowingly
fraudulent or deliberately dishonest, or to constitute willful misconduct or a
knowing violation of the law; (6) an account of any conduct from which the
indemnified party derived an improper personal benefit; (7) on account of
conduct the indemnified party believed to be contrary to the best interests of
the registrant or its stockholders; (8) on account of conduct that constituted a
breach of the indemnified party's duty of loyalty to the registrant or its
stockholders; or (9) if a final decision by a court having jurisdiction in the
matter shall determine that such indemnification is not lawful.

    The indemnification provision in the bylaws and the indemnification
agreements entered into between the registrant and its directors and executive
officers may be sufficiently broad to permit indemnification of the registrant's
officers and directors for liabilities arising under the Securities Act of 1933.

ITEM 16. EXHIBITS.

<TABLE>
<CAPTION>
EXHIBIT
NUMBER    DESCRIPTION OF DOCUMENT
- -------   -----------------------
<C>       <S>
    1.1*  Form of Underwriting Agreement

   4.1+   Specimen Common Stock Certificate

    5.1   Opinion of Wilson Sonsini Goodrich & Rosati, P.C.

   23.1   Consent of Ernst & Young LLP, Independent Auditors

   23.2   Consent of Arthur Andersen LLP

   23.3   Consent of Ernst & Young LLP, Independent Auditors

   23.4   Consent of Counsel (included in Exhibit 5.1)

   24.1   Power of Attorney (included on page II-4)
</TABLE>

- ------------------------

*   To be filed by amendment.

+   Incorporated by reference from the registrant's Report on Form 10-K filed
    with the Securities and Exchange Commission on March 19, 1998.

                                      II-2
<PAGE>
ITEM 17. UNDERTAKINGS.

    Inference hereby undertakes:

    1.  To file, during any period in which offers or sales are being made, a
post-effective amendment to this registration statement:

        (a) To include any prospectus required by Section 10(a)(3) of the
    Securities Act;

        (b) To reflect in the prospectus any facts or events arising after the
    effective date of the registration statement (or the most recent
    post-effective amendment thereof) which, individually or in the aggregate,
    represent a fundamental change in the information set forth in the
    registration statement;

        (c) To include any material information with respect to the plan of
    distribution not previously disclosed in the registration statement or any
    material change to such information in the registration statement; provided,
    however, that paragraphs (a) and (b) above do not apply if the information
    required to be included in a post-effective amendment by those paragraphs is
    contained in periodic reports filed by Inference pursuant to Section 13 or
    Section 15(d) of the Exchange Act that are incorporated by reference in the
    registration statement.

    2.  That, for the purpose of determining any liability under the Securities
Act, each such post-effective amendment shall be deemed to be a new registration
statement relating to the securities offered therein, and the offering of such
securities at that time shall be deemed to be the initial bona fide offering
thereof.

    3.  To remove from registration by means of a post-effective amendment any
of the securities being registered which remain unsold at the termination of the
offering.

    4.  That, for the purpose of determining any liability under the Securities
Act, each filing of Inference's annual report pursuant to Section 13(a) or
Section 15(d) of the Exchange Act, (and, where applicable, each filing of an
employee benefit plan's annual report pursuant to Section 15(d) of the Exchange
Act) that is incorporated by reference in the registration statement shall be
deemed to be a new registration statement relating to the securities offered
therein, and the offering of such securities at that time shall be deemed to be
the initial bona fide offering thereof.

    5.  To deliver or cause to be delivered with the prospectus, to each person
to whom the prospectus is sent or given, the latest annual report to security
holders that is incorporated by reference in the prospectus and furnished
pursuant to and meeting the requirements of Rule 14a-3 or Rule 14c-3 under the
Exchange Act; and, where interim financial information required to be presented
by Article 3 of Regulation S-X are not set forth in the prospectus, to deliver,
or cause to be delivered to each person to whom the prospectus is sent or given,
the latest quarterly report that is specifically incorporated by reference in
the prospectus to provide such interim financial information.

    6.  Insofar as indemnification for liabilities arising under the Securities
Act may be permitted to directors, officers and controlling persons of Inference
pursuant to the foregoing provisions, or otherwise, Inference has been advised
that in the opinion of the SEC such indemnification is against public policy as
expressed in the Securities Act and is, therefore, unenforceable. In the event
that a claim for indemnification against such liabilities (other than the
payment by Inference of expenses incurred or paid by a director, officer, or
controlling person of Inference in the successful defense of any action, suit,
or proceeding) is asserted by such director, officer, or controlling person in
connection with the securities being registered, Inference will, unless in the
opinion of its counsel the matter has been settled by controlling precedent,
submit to a court of appropriate jurisdiction the question whether such
indemnification by it is against public policy as expressed in the Securities
Act and will be governed by the final adjudication of such issue.

                                      II-3
<PAGE>
                                   SIGNATURES

    Pursuant to the requirements of the Securities Act of 1933, the Registrant
certifies that it has reasonable grounds to believe that it meets all of the
requirements for filing on Form S-3 and has duly caused this Registration
Statement to be signed on its behalf by the undersigned, thereunto duly
authorized, in the city of San Ramon, state of California, on February 14, 2000.

<TABLE>
<S>                                                    <C>  <C>
                                                       SUPERGEN, INC.

                                                       By:             /s/ JOSEPH RUBINFELD
                                                            -----------------------------------------
                                                                         Joseph Rubinfeld
                                                              CHIEF EXECUTIVE OFFICER, PRESIDENT AND
                                                                             DIRECTOR
</TABLE>

                               POWER OF ATTORNEY

    We, the undersigned officers and directors of SuperGen, Inc. hereby
constitute and appoint Joseph Rubinfeld and Ronald H. Spair, and each of them
individually, our true and lawful attorney-in-fact, with full power of
substitution, to sign for us and in our names in the capacities indicated below
the Registration Statement filed herewith and any and all amendments to said
Registration Statement, and generally to do all such things in our name and
behalf in our capacities as officers and directors to enable SuperGen, Inc. to
comply with the provisions of the Securities Act of 1933, as amended, and all
requirements of the Securities and Exchange Commission, hereby ratifying and
confirming our signatures as they may be signed by our said attorney to said
Registration Statement and any and all amendments thereto.

    Pursuant to the requirements of the Securities Act of 1933, this
Registration Statement and Power of Attorney has been signed below by the
following persons in the capacities and on the dates indicated.

<TABLE>
<CAPTION>
                   SIGNATURE                                    TITLE                      DATE
                   ---------                                    -----                      ----
<C>                                               <S>                                <C>
              /s/ JOSEPH RUBINFELD                Chief Executive Officer,
     --------------------------------------         President and Director           February 14, 2000
                Joseph Rubinfeld                    (Principal Executive Officer)

              /s/ RONALD H. SPAIR                 Chief Financial Officer
     --------------------------------------         (Principal Financial and         February 14, 2000
                Ronald H. Spair                     Accounting Officer)

            /s/ LAWRENCE J. ELLISON
     --------------------------------------       Director                           February 14, 2000
              Lawrence J. Ellison

                /s/ DANIEL ZURR
     --------------------------------------       Director                           February 14, 2000
                  Daniel Zurr

                /s/ DENIS BURGER
     --------------------------------------       Director                           February 14, 2000
                  Denis Burger

                /s/ JULIUS VIDA
     --------------------------------------       Director                           February 14, 2000
                  Julius Vida

               /s/ WALTER J. LACK
     --------------------------------------       Director                           February 14, 2000
                 Walter J. Lack
</TABLE>

                                      II-4
<PAGE>
                                 EXHIBIT INDEX

<TABLE>
<CAPTION>
EXHIBIT
 NUMBER    DESCRIPTION OF DOCUMENT
- --------   -----------------------
<C>        <S>
    1.1*   Form of Underwriting Agreement

    4.1+   Specimen Common Stock Certificate

    5.1    Opinion of Wilson Sonsini Goodrich & Rosati, P.C.

   23.1    Consent of Ernst & Young LLP, Independent Auditors

   23.2    Consent of Arthur Andersen LLP

   23.3    Consent of Ernst & Young LLP, Independent Auditors

   23.4    Consent of Counsel (included in Exhibit 5.1)

   24.1    Power of Attorney (included on page II-4)
</TABLE>

- ------------------------

*   To be filed by amendment.

+   Incorporated by reference from the registrant's Report on Form 10-K filed
    with the Securities and Exchange Commission on March 19, 1998.

<PAGE>
                                                                     EXHIBIT 5.1

                               February 14, 2000

SuperGen, Inc.
Two Annabel Lane, Suite 220
San Ramon, California 94583

    RE: REGISTRATION STATEMENT ON FORM S-3

Ladies and Gentlemen:

    We have examined the Registration Statement on Form S-3 to be filed by
SuperGen, Inc. (the "Company") with the Securities and Exchange Commission on
the date hereof (the "Registration Statement") in connection with the
registration under the Securities Act of 1933, as amended, of a total of
3,105,000 shares of your Common Stock, $0.001 par value per share (the
"Shares"), including 405,000 shares subject to an over-allotment option. The
Shares are being sold by the Company and certain selling stockholders identified
as such in the Registration Statement (the "Selling Stockholders").

    As counsel for the Company, we have examined originals or copies, certified
or otherwise identified to our satisfaction, of such documents, corporate
records, certificates of public officials and other instruments as we have
deemed necessary for the purposes of rendering this opinion.

    Based upon the foregoing, we are of the opinion that the Shares to be
registered for sale by the Company and the Selling Stockholders have been duly
authorized by the Company, and the Shares to be registered for sale by the
Selling Stockholders are, and the Shares to be registered for sale by the
Company, when issued, delivered and paid for in accordance with the terms of the
underwriting agreement referred to in the Registration Statement and in
accordance with the resolutions adopted by the Board of Directors of the
Company, will be, validly issued, fully paid and nonassessable.

    We consent to the use of this opinion as an exhibit to the Registration
Statement and further consent to the use of our name under the caption "Legal
Matters" in the Registration Statement and the prospectus forming a part
thereof, and any amendments thereto.

                                          Very truly yours,

                                          WILSON SONSINI GOODRICH & ROSATI
                                          Professional Corporation

                                          /s/ WILSON SONSINI GOODRICH & ROSATI
                                          P.C.

<PAGE>
                                                                    EXHIBIT 23.1

               CONSENT OF ERNST & YOUNG LLP, INDEPENDENT AUDITORS

    We consent to the reference to our firm under the caption "Experts" in the
Registration Statement (Form S-3) and related prospectus of SuperGen, Inc. for
the registration of 3,105,000 shares of its common stock and to the
incorporation by reference therein of our report dated March 25, 1999, with
respect to the consolidated financial statements of SuperGen, Inc. included in
its Annual Report (Form 10-K) for the year ended December 31, 1998, filed with
the Securities and Exchange Commission.

                                          /s/ ERNST & YOUNG LLP

Palo Alto, California
February 9, 2000

<PAGE>
                                                                    EXHIBIT 23.2

                   CONSENT OF INDEPENDENT PUBLIC ACCOUNTANTS

    As independent public accountants, we hereby consent to the incorporation by
reference in this Form S-3 of our report dated February 11, 1999 included in
SuperGen, Inc.'s Form 8-K dated August 26, 1999, and to all references to our
firm included in this Registration Statement.

                                          /s/ ARTHUR ANDERSEN LLP

Philadelphia, PA
February 11, 2000

<PAGE>
                                                                    EXHIBIT 23.3

               CONSENT OF ERNST & YOUNG LLP, INDEPENDENT AUDITORS

    We consent to the incorporation by reference of our report in the
Registration Statement (Form S-3) and related prospectus of SuperGen, Inc. for
the registration of 3,105,000 shares of its common stock and to the
incorporation by reference therein of our report dated January 31, 1996 with
respect to the financial statements of Sparta Pharmaceuticals, Inc. included in
SuperGen's Form 8-K dated August 26, 1999.

                                          /s/ ERNST & YOUNG LLP

Raleigh, North Carolina
February 9, 2000


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