NEORX CORP
8-A12G, 1995-08-04
IN VITRO & IN VIVO DIAGNOSTIC SUBSTANCES
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<PAGE>   1





                       SECURITIES AND EXCHANGE COMMISSION
                            WASHINGTON, D.C.  20549

                                    FORM 8-A

               FOR REGISTRATION OF CERTAIN CLASSES OF SECURITIES
                    PURSUANT TO SECTION 12(B) OR (G) OF THE
                        SECURITIES EXCHANGE ACT OF 1934

                               NeoRx Corporation
             ------------------------------------------------------
             (Exact name of Registrant as specified in its charter)

<TABLE>
<S>                                                <C>
               Washington                                       91-1261311
- ----------------------------------------           ------------------------------------
(State of incorporation or organization)           (I.R.S. Employer Identification No.)

        410 West Harrison Street
           Seattle, Washington                                     98119
- ----------------------------------------                        ----------
(Address of principal executive offices)                        (Zip Code)
</TABLE>

Securities to be registered pursuant to Section 12(b) of the Act:

                                      None

Securities to be registered pursuant to Section 12(g) of the Act:

Warrants to purchase shares of Common Stock, $.02 par value 
  per share, of NeoRx Corporation

<PAGE>   2
                                    FORM 8-A
                       SECURITIES AND EXCHANGE COMMISSION
                            WASHINGTON, D.C.  20549

                               NEORX CORPORATION

ITEM 1.          DESCRIPTION OF REGISTRANT'S SECURITIES TO BE REGISTERED

         For a description of the Warrants being registered, reference is made
to the section entitled "Description of the Warrants" contained in the
Registrant's Registration Statement on Form S-3, File No. 33-60029, filed with
the Securities and Exchange Commission on June 7, 1995 and incorporated herein
by reference.  A copy of pages 10 through 12 of the Registration Statement is
attached as Exhibit 3 to this filing pursuant to Rule 12b-23 under the
Securities Exchange Act of 1934, as amended.

ITEM 2.          EXHIBITS

         The following exhibits are filed as a part of this Registration
Statement:
<TABLE>
<CAPTION>
 Exhibit No.        Description
 -----------        -----------
    <S>             <C>
    1.1             Specimen Warrant Certificate.

    1.2             Form of Purchase Agreement.

    2.1(a)          Restated Articles of Incorporation of the Registrant.  (Filed as an exhibit to
                    the Company's Registration Statement on Form S-1 (Registration No. 33-20694)
                    effective August 11, 1988 and incorporated herein by reference).

    2.1(b)          Amendment to Restated Articles of Incorporation filed with the Washington
                    Secretary of State on March 15, 1990.  (Filed as an exhibit to the Company's
                    Registration Statement on Form S-4 (Registration No. 33-33153) effective March
                    27, 1990 and incorporated herein by reference).

    2.1(c)          Articles of Amendment, dated November 6, 1991, to Articles of Incorporation.
                    (Filed as an exhibit to the Company's Form 10-K for the fiscal year ended
                    September 30, 1990 and incorporated herein by reference).

    2.2             Bylaws, as amended, of the Registrant.  (Filed as an exhibit to the Company's
                    Registration Statement on Form S-4 (Registration No. 33-33153) effective March
                    27, 1990 and incorporated herein by reference).

    3               Pages 10 through 12 of the Prospectus.
</TABLE>
<PAGE>   3
         Pursuant to the requirements of Section 12 of the Securities Exchange
Act of 1934, as amended, the Registrant has duly caused this Registration
Statement to be signed on its behalf by the undersigned, thereunto duly
authorized.

                        NEORX CORPORATION.

                            /s/  Paul G. Abrams                
                        --------------------------------------
                                 Paul G. Abrams, President

Dated:  August 4, 1995
<PAGE>   4
                                 EXHIBIT INDEX

<TABLE>
<CAPTION>
                                                                                          Sequential
Exhibit No.      Description                                                               Page No.
- -----------      -----------                                                               --------
<S>              <C>
1.1              Specimen Warrant Certificate. . . . . . . . . . . . . . . . . . . . . . .

1.2              Form of Purchase Agreement. . . . . . . . . . . . . . . . . . . . . . . .

2.1(a)           Restated Articles of Incorporation of the Registrant.  (Filed as an
                 exhibit to the Company's Registration Statement on Form S-1 (Registration
                 No. 33-20694) effective August 11, 1988 and incorporated herein by
                 reference). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.1(b)           Amendment to Restated Articles of Incorporation filed with the Washington
                 Secretary of State on March 15, 1990.  (Filed as an exhibit to the
                 Company's Registration Statement on Form S-4 (Registration No. 33-33153)
                 effective March 27, 1990 and incorporated herein by reference). . . . .  .

2.1(c)           Articles of Amendment, dated November 6, 1991, to Articles of
                 Incorporation.  (Filed as an exhibit to the Company's Form 10-K for the
                 fiscal year ended September 30, 1990 and incorporated herein by
                 reference). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.2              Bylaws, as amended, of the Registrant.  (Filed as an exhibit to the
                 Company's Registration Statement on Form S-4 (Registration No. 33-33153)
                 effective March 27, 1990 and incorporated herein by reference). . . . . .

3                Pages 10 through 12 of the Prospectus.  . . . . . . . . . . . . . . . . .
</TABLE>

<PAGE>   1

THE SECURITIES REPRESENTED HEREBY HAVE BEEN ACQUIRED FOR INVESTMENT PURPOSES
ONLY AND HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED.
THE SECURITIES MAY NOT BE SOLD OR TRANSFERRED IN THE ABSENCE OF SUCH
REGISTRATION OR AN EXEMPTION THEREFROM.

ADDITIONALLY, THE TRANSFER OF THE SECURITIES REPRESENTED HEREBY IS SUBJECT 
TO CERTAIN RESTRICTIONS SPECIFIED IN THE PURCHASE AGREEMENT DATED AS OF
APRIL 18, 1995 BETWEEN THE COMPANY AND THE ORIGINAL PURCHASER, AND NO TRANSFER
OF THE SECURITIES SHALL BE VALID OR EFFECTIVE ABSENT COMPLIANCE WITH SUCH
RESTRICTIONS.  ALL SUBSEQUENT HOLDERS OF THESE SECURITIES WILL HAVE AGREED TO
BE BOUND BY CERTAIN OF THE TERMS OF THE PURCHASE AGREEMENT, INCLUDING SECTIONS
7.1 AND 8.3.  COPIES OF THE PURCHASE AGREEMENT MAY BE OBTAINED AT NO COST BY
WRITTEN REQUEST MADE BY THE REGISTERED HOLDER OF THIS CERTIFICATE TO THE
SECRETARY OF THE COMPANY. 

             VOID AFTER 5 P.M. (SEATTLE TIME) ON APRIL 25, 1998.


W-Warrant_No                           Warrants
                                       
                                       Denomination
                                       CUSIP No. 640520 11 0



                               NEORX CORPORATION
              ORGANIZED UNDER THE LAWS OF THE STATE OF WASHINGTON
                   WARRANT TO PURCHASE SHARES OF COMMON STOCK

         This certifies that CERTIFICATE_NAMES~ ("Holder") is the registered
holder of the number of Warrants to purchase shares of common stock (the
"Warrants") set forth above.  Each Warrant entitles the holder thereof, subject
to the terms set forth below and in the Purchase Agreement (as hereinafter
defined), to purchase from NEORX CORPORATION, a Washington corporation (the
"Company"), one quarter of one fully paid and nonassessable share of the
Company's $.02 par value Common Stock (the "Stock") at a price of $5.3125 per
share (the

 
<PAGE>   2

"Stock Purchase Price") commencing six months from the Closing Date (as defined
in the Purchase Agreement) (October 25, 1995), but not later than 5 p.m.
(Seattle time) on the Expiration Date (as defined below), upon surrender of
this Warrant Certificate to the Company at the principal office of First
Interstate Bank of Washington, N.A. (the "Warrant Agent") in Seattle,
Washington or at the principal office of the Company in Seattle, Washington (or
at such other location as the Company may advise Holder in writing), with the
form of election to exercise appearing on this Warrant Certificate duly
completed and signed, and upon payment to the Warrant Agent for the account of
the Company in cash or cashier's check (or by bank wire transfer of
immediately available funds) of the aggregate Stock Purchase Price in lawful
money of the United States of America for the number of shares for which the
Warrants are being exercised determined in accordance with the provisions
hereof.  The Stock Purchase Price and, in some cases, the number of shares
purchasable hereunder are subject to adjustment as provided in Paragraph 3
hereof.  This Warrant and all rights hereunder, to the extent not exercised in
the manner set forth herein, shall terminate and become null and void on the
Expiration Date.  "Expiration Date" means April 25, 1998, which is the third
anniversary of the Closing pursuant to the Purchase Agreement.  If such date
shall in the state of Washington be a holiday or a day on which banks are
authorized to close, then the Expiration Date shall be 5 p.m. (Seattle time)
the next following day which in the state of Washington is not a holiday or a
day on which banks are authorized to close.  This Warrant is issued pursuant to
and is subject in all respects to the terms and conditions set forth in the
Purchase Agreement dated as of April 18, 1995 between the Company and the
original purchaser (the "Purchase Agreement").

         This Warrant is subject to the following terms and conditions:

         1.      Exercise; Issuance of Certificates; Payment for Shares.  This
Warrant is exercisable at the option of Holder commencing six months from the
Closing Date, but not later than 5 p.m. (Seattle time) on the Expiration Date,
for all or a portion of the shares of Stock which may be purchased hereunder.
The Company agrees that the shares of Stock purchased under this Warrant shall
be and are deemed to be issued to Holder as the record owner of such shares as
of the close of business on the date on which this Warrant shall have been
surrendered and payment made for such shares.  Certificates for the shares of
Stock so purchased, together with any other securities or property to which
Holder is entitled upon such exercise, shall be delivered to Holder by the
Company's transfer agent at the Company's expense within a reasonable time
after the rights represented by this Warrant have been exercised.  Each stock
certificate so delivered shall be in such denominations of Stock as may be
requested


                                     -2-
<PAGE>   3

by Holder and shall be registered in the name of Holder or such other name as
shall be designated by Holder.  If, upon exercise, fewer than all of the shares
of Stock evidenced by this Warrant are purchased prior to the Expiration Date
of this Warrant, one or more new warrants substantially in the form of, and on
the terms in, this Warrant will be issued for the remaining number of shares of
Stock not purchased upon exercise of this Warrant.

         2.      Shares to Be Fully Paid; Reservation of Shares.  The Company
covenants and agrees that all shares of Stock which may be issued upon the
exercise of the rights represented by this Warrant will, upon issuance, be duly
authorized, validly issued, fully paid and nonassessable and free from all
preemptive rights of any shareholder and free of all taxes, liens and charges
with respect to the issue thereof.

         3.      Adjustment of Stock Purchase Price and Number of Shares.  The
Stock Purchase Price and the number of shares purchasable upon the exercise of
this Warrant shall be subject to adjustment from time to time upon the
occurrence of certain events described in this Paragraph 3.

                 3.1      Distributions of Stock and Other Rights.  In case the
Company shall at any time after the date of this Warrant (a) declare a dividend
on the outstanding Stock in shares of its capital stock, (b) subdivide the
outstanding Stock, (c) combine the outstanding Stock into a smaller number of
shares, or (d) issue any shares of its capital stock by reclassification of the
Stock (including any such reclassification in connection with a consolidation
or merger in which the Company is the continuing corporation), then, in each
case, the Stock Purchase Price, and the number and kind of shares receivable
upon exercise of this Warrant, in effect at the time of the record date for
such dividend or of the effective date of such subdivision, combination or
reclassification, shall be proportionately adjusted so that Holder after such
time shall be entitled to receive the aggregate number and kind of shares
which, if such Warrant had been exercised immediately prior to such time, it
would have owned upon such exercise and been entitled to receive by virtue of
such dividend, subdivision, combination or reclassification.

                 3.2      Changes in Stock

                          (a)     In case of any consolidation with or merger
of the Company into another corporation (other than a merger in which the
Company is the surviving or continuing corporation), or in case of any sale,
lease or conveyance to another corporation of the property of the Company as an
entirety or substantially as an entirety, such successor, leasing or purchasing
corporation, as the case may be,





                                      -3-
<PAGE>   4

shall (i) execute with Holder an agreement providing that Holder shall have the
right thereafter to receive upon exercise of this Warrant solely the kind and
amount of shares of stock and/or other securities, property, cash or any
combination thereof receivable upon such consolidation, merger, sale, lease or
conveyance by a holder of the number of shares of Stock for which this Warrant
might have been exercised immediately prior to such consolidation, merger,
sale, lease or conveyance, and (ii) make effective provision in its certificate
of incorporation or otherwise, if necessary, in order to effect such agreement.
Such agreement shall provide for adjustments which shall be as nearly
equivalent as practicable to the adjustments in Paragraph 3.1 hereof.

                          (b)     In case of any reclassification or change of
the shares of Stock issuable upon exercise of this Warrant (other than a change
in par value or from no par value to a specified par value, or as a result of a
subdivision or combination, but including any change in the shares into two or
more classes or series of shares), or in case of any consolidation or merger of
another corporation into the Company in which the Company is the continuing
corporation and in which there is a reclassification or change (including a
change to the right to receive cash or other property) of the shares of Stock
(other than a change in par value, or from no par value to a specified par
value, or as a result of a subdivision or combination, but including any change
in the shares into two or more classes or series of shares), Holder shall have
the right thereafter to receive upon exercise of this Warrant solely the kind
and amount of shares of stock and/or other securities, property, cash or any
combination thereof receivable upon such reclassification, change,
consolidation or merger by Holder of the number of shares of Stock for which
this Warrant might have been exercised immediately prior to such
reclassification, change, consolidation or merger.  Thereafter, appropriate
provision shall be made for adjustments which shall be as nearly equivalent as
practicable to the adjustments in Paragraph 3.1 hereof.

                          (c)     The above provisions of this Paragraph 3.2
shall similarly apply to successive reclassifications and changes of shares of
Stock and to successive consolidations, mergers, sales, leases or conveyances.

                 3.3      Notice.  In case at any time the Company shall
propose to effect (a) any of the actions described in Paragraph 3.1 or 3.2
hereof, (b) any liquidation, dissolution or winding-up of the Company, or (c)
any other action which would cause an adjustment to the Stock Purchase Price,
then, and in any one or more of such cases, the Company shall give written
notice thereof, by registered mail, postage prepaid, to Holder at Holder's
address as it shall appear in the Warrant Register, mailed at least





                                     -4-
<PAGE>   5

15 days prior to (i) the date as of which the holders of record of shares of
Stock to be entitled to receive any such dividend, distribution, rights,
warrants or other securities are to be determined, (ii) the date on which any
such reclassification, change of outstanding shares of Stock, consolidation,
merger, sale, lease, conveyance of property, liquidation, dissolution or
winding-up is expected to become effective, and the date as of which it is
expected that holders of record of shares of Stock shall be entitled to
exchange their shares for securities or other property, if any, deliverable
upon such reclassification, change of outstanding shares, consolidation,
merger, sale, lease, conveyance of property, liquidation, dissolution or
winding-up, or (iii) the date of such action which would require an adjustment
to the Stock Purchase Price.

         4.      Issue Tax.  The issuance of certificates for shares of Stock
upon the exercise of this Warrant shall be made without charge to Holder for
any issue tax in respect thereof; provided, however, that the Company shall not
be required to pay any tax which may be payable in respect of any transfer
involved in the issuance and delivery of any certificate in a name other than
that of the then holder of the Warrant being exercised.

         5.      No Voting or Dividend Rights; Limitation of Liability.
Nothing contained in this Warrant shall be construed as conferring upon Holder
the right to vote or to consent or to receive notice as a shareholder in
respect of meetings of shareholders for the election of directors of the
Company or any other matters or any rights whatsoever as a shareholder of the
Company.  Except for the adjustment to the Stock Purchase Price pursuant to
Paragraph 3 hereof, no dividends or interest shall be payable or accrued in
respect of this Warrant or the interest represented hereby or the shares
purchasable hereunder until, and only to the extent that, this Warrant shall
have been exercised.  No provisions hereof, in the absence of affirmative
action by Holder to purchase shares of Stock, and no mere enumeration herein of
the rights or privileges of Holder, shall give rise to any liability of Holder
for the Stock Purchase Price or as a shareholder of the Company, whether such
liability is asserted by the Company or by its creditors.

         6.      Restrictions on Transferability of Securities; Compliance With
Securities Act.

                 6.1      Restrictions on Transferability.  This Warrant and
the Stock issuable upon exercise hereof (collectively, the "Securities") shall
not be transferable except in compliance with the Purchase Agreement.





                                      -5-
<PAGE>   6

                 6.2      Restrictive Legend.  Each certificate representing
the Securities or any other securities issued in respect of the Securities upon
any stock split, stock dividend, recapitalization, merger, consolidation or
similar event shall (unless otherwise permitted by the provisions of the
Purchase Agreement) be stamped or otherwise imprinted with a legend
substantially in the form (in addition to any legend required under applicable
state securities laws) set forth on the reverse of this Warrant.

         7.      Modification and Waiver.  This Warrant and any provision
hereof may be changed, waived, discharged or terminated only by an instrument
in writing signed by the party against which enforcement of the same is sought.

         8.      Notices.  Any notice, request or other document required or
permitted to be given or delivered to Holder or the Company shall be delivered
or shall be sent by certified or registered mail, postage prepaid, to Holder at
its address as shown on the books of the Company or to the Company at the
address indicated therefor in the first paragraph of this Warrant.

         9.      Descriptive Headings and Governing Law.  The descriptive
headings of the several sections and paragraphs of this Warrant are inserted
for convenience only and do not constitute a part of this Warrant.  This
Warrant shall be construed and enforced in accordance with, and the rights of
the parties shall be governed by, the laws of the State of Washington.

         10.     Lost Warrants or Stock Certificates.  The Company represents
and warrants to Holder that upon receipt of evidence reasonably satisfactory to
the Company of the loss, theft, destruction or mutilation of any Warrant or
stock certificate and, in the case of any such loss, theft or destruction, upon
receipt of an indemnity and, if requested, bond reasonably satisfactory to the
Company (the costs of which are to be borne solely by Holder), or, in the case
of any such mutilation, upon surrender and cancellation of such Warrant or
stock certificate, the Company at its expense will make and deliver a new
Warrant or stock certificate, of like tenor, in lieu of the lost, stolen,
destroyed or mutilated Warrant or stock certificate.

         11.     Fractional Shares.  No fractional shares shall be issued upon
exercise of this Warrant.  The Company shall, in lieu of issuing any fractional
share, pay Holder a sum in cash equal to the fair market value of any such
fractional interest as it shall appear on the public market, or if there is no
public market for such shares, then as shall be reasonably determined by the
Company.





                                      -6-
<PAGE>   7

         IN WITNESS WHEREOF, the Company has caused this Warrant to be executed
by its duly authorized officers.

Dated:  April 25, 1995
                                       NEORX CORPORATION
                                  Attest:


                                       Secretary                President

Countersigned:
First Interstate Bank of Washington, N.A.
   as Warrant Agent

By:
               Authorized Signature





                                       -7-
<PAGE>   8

                              ELECTION TO EXERCISE

                    TO BE EXECUTED BY THE REGISTERED HOLDER
                         IN ORDER TO EXERCISE WARRANTS

         The undersigned hereby irrevocably elects to exercise the right,
represented by this Warrant Certificate, to purchase the Stock and herewith
tenders in payment for such Stock $________ in lawful money of the United
States of America, in accordance with the terms hereof.  The undersigned
requests that a certificate representing the Warrant Shares be registered and
delivered as follows:

                 Name:                     ______________________________

                 Address:                  ______________________________

                                           ______________________________

                 Delivery Address:         ______________________________
                    (if different)         ______________________________

         If such amount of Stock is less than that of the aggregate amount of
Stock purchasable hereunder, the undersigned requests that a new Warrant
Certificate representing the balance of such Stock be registered and delivered
as follows:

                 Name:                     ______________________________

                 Address:                  ______________________________

                                           ______________________________

                 Delivery Address:         ______________________________
                    (if different)         ______________________________

         If the exercise of the Warrants is not covered by a Registration
Statement effective under the Securities Act of 1933, as amended (the
"Securities Act"), the undersigned represents that

                  (i)     the undersigned has sufficient funds available to
purchase the Stock,

                 (ii)     the undersigned understands that the offering and
sale of the Stock is intended to be exempt from registration under the
Securities Act and that the Company is relying upon its representations herein
for purposes of determining whether such exemption is available,

                (iii)     the undersigned is purchasing the Stock for its own
account and not with a view to, or for sale in connection with, any public
distribution thereof,






<PAGE>   9

                  (iv)    the undersigned understands and is familiar with 
the provisions of Regulation D under the Securities Act ("Regulation D") and 
is an "accredited investor" as such term is defined in Regulation D,

                  (v)     the undersigned understands and agrees that (A) it
may be unable to readily liquidate its investment in the shares of Stock and
that the shares must be held indefinitely unless a subsequent disposition
thereof is registered or qualified under the Securities Act and applicable
state securities or Blue Sky laws or is exempt from such registration or
qualification, and that the Company is not required to register the same or to
take any action or make such an exemption available except to the extent
provided in the Purchase Agreement dated as of April 18, 1995 and (B) the
exemption from registration under the Securities Act afforded by Rule 144
promulgated by the Securities and Exchange Commission ("Rule 144") depends on
the satisfaction of various conditions by the undersigned and the Company and
that, if applicable, Rule 144 affords the basis for sales under certain
circumstances in limited amounts, and that if such exemption is utilized by the
undersigned, such conditions must be fully complied with by the undersigned and
the Company, as required by Rule 144, and

                 (vi)     the address set forth below is the true and correct
address of the undersigned's residence.

Dated:______________

<TABLE>
             <S>                                                   <C>
             _________________________________                     Signature:_________________________
                 (Insert social security or                                NOTE:  The above signature must correspond
             other identifying number of holder)                           with the name as written upon the face of
                                                                           this Warrant Certificate in every
                                                                           particular, without alteration or
                                                                           enlargement or any change whatsoever.  The
                                                                           signature of the registered holder hereof
                                                                           must be guaranteed.
</TABLE>

Signature Guaranteed:



_________________________________





                                        -2-
<PAGE>   10

                                   ASSIGNMENT

                    TO BE EXECUTED BY THE REGISTERED HOLDER
                         IN ORDER TO TRANSFER WARRANTS

         FOR VALUE RECEIVED, the undersigned registered holder hereby sells,
assigns and transfers unto

_______________________________________________________________

_______________________________________________________________

                  (Please print name and address of assignee)

this Warrant Certificate, together with all right, title and interest therein,
and does irrevocably constitute and appoint __________________ attorney, to
transfer this Warrant Certificate on the books of the Warrant Agent, with full
power of substitution.

Dated: ___________________________                    

<TABLE>
<S>                                                   <C>
________________________________                      Signature: _________________________
   (Insert social security or                                NOTE:  The above signature must correspond
 other identifying number of holder)                         with the name as written upon the face of
                                                             this Warrant Certificate in every
                                                             particular, without alteration or
                                                             enlargement or any change whatsoever.  The
                                                             signature of the registered holder hereof
                                                             must be guaranteed.
</TABLE>

Signature Guaranteed:


_________________________________





                                          -3-

<PAGE>   1


                               NEORX CORPORATION

                               PURCHASE AGREEMENT

         This Purchase Agreement (the "Agreement") is made as of April 18,
1995, by and between NeoRx Corporation, a Washington corporation (the
"Company") with its principal office at 410 West Harrison Street, Seattle,
Washington 98119, and the undersigned purchaser (the "Purchaser").

                                   SECTION 1



                           PURCHASE AND SALE OF UNITS

         1.1     PURCHASE AND SALE OF UNITS

         The Purchaser agrees to purchase from the Company, and the Company
agrees to issue and sell to the Purchaser, the number of Units set forth on
Schedule 1 annexed hereto upon the terms and conditions set forth herein and in
the Private Placement Memorandum dated April 3, 1995 (such Private Placement
Memorandum, including all exhibits and appendices thereto, being hereinafter
collectively referred to as the "Placement Memorandum").  Each Unit consists of
one share of Common Stock, $.02 par value per share (the "Shares") and one
warrant to purchase one-quarter of one share of Common Stock (the "Warrants")
of the Company.  Each Warrant, a copy of which is attached hereto as Exhibit A,
entitles the registered holder thereof to purchase one share of Common Stock at
a price of $5.3125, subject to adjustment in certain circumstances, commencing
on the date the Warrant becomes separately transferable until three years from
the Closing (as defined below).  The securities comprising the Units will not
be separable or separately transferable prior to six months from the Closing.
The Units, the Shares, the Warrants and the shares of Common Stock issuable
upon exercise of the Warrants are herein collectively referred to as the
"Securities."

                                   SECTION 2



                             CLOSING DATE; DELIVERY

         2.1     CLOSING DATE

         The completion of the purchase and sale of the Units will be held at
the offices of Perkins Coie, 1201 Third Avenue, Seattle, Washington 98101 at 9
a.m., Seattle


<PAGE>   2

Time, on Tuesday, April 25, 1995 (the "Closing").  The date of the Closing is
hereinafter referred to as the "Closing Date."

         2.2     DELIVERY

         At the Closing, the Company will deliver to the Purchaser the
certificates evidencing the securities comprising the Units purchased by the
Purchaser as shown on Schedule 1.  Such delivery shall be against payment of
the purchase price therefor by wire transfer to the Company's bank account or
by delivery of a cashier's check for immediately available funds in the amount
set forth on Schedule 1.

                                   SECTION 3


                 REPRESENTATIONS AND WARRANTIES OF THE COMPANY

         The Company represents and warrants to the Purchaser as follows:

         3.1     ORGANIZATION AND STANDING

         The Company is a corporation duly organized and validly existing
under, and by virtue of, the laws of the State of Washington and is in good
standing as a domestic corporation under the laws of said state.

         3.2     CORPORATE POWER; AUTHORIZATION

         The Company has all requisite legal and corporate power and has taken
all requisite corporate action to execute and deliver this Agreement, to sell
and issue the Units and to carry out and perform all of its obligations under
this Agreement.  This Agreement constitutes the legal, valid and binding
obligation of the Company, enforceable in accordance with its terms, except (i)
as limited by applicable bankruptcy, insolvency, reorganization or similar laws
relating to or affecting the enforcement of creditors' rights generally and
(ii) as limited by equitable principles generally.  The execution and delivery
of this Agreement does not, and the performance of this Agreement and the
compliance with the provisions hereof and the issuance, sale and delivery of
the Units by the Company will not, materially conflict with, or result in a
material breach or violation of the terms, conditions or provisions of, or
constitute a material default under, or result in the creation or imposition of
any material lien pursuant to the terms of, the Articles of Incorporation or
Bylaws of the Company or any statute, law, rule or regulation or any state or
federal order, judgment or decree or any indenture, mortgage, lease or other
material agreement or instrument to which the Company or any of its properties
is subject.

                                       -2-

<PAGE>   3

         3.3     ISSUANCE AND DELIVERY

         The Units, the Shares and the Warrants have been duly authorized, and,
when issued and delivered in compliance with this Agreement, will be duly
issued and delivered; and the Units, the Shares and the Warrants will conform
to the descriptions thereof in the Placement Memorandum in all material
respects.  The Warrants will be exercisable for shares of Common Stock of the
Company in accordance with the terms of the Warrants and at the prices therein
provided for; the shares of Common Stock issuable upon exercise of the Warrants
have been duly authorized and reserved for issuance upon such exercise, and
such shares, when issued upon such exercise in accordance with the terms of the
Company's Articles of Incorporation and the Warrants, respectively, and when
the price is paid upon exercise of the Warrants, shall be fully paid and
nonassessable.

         3.4     PRIVATE PLACEMENT OFFERING MEMORANDUM; SEC DOCUMENTS; FINANCIAL
                 STATEMENTS

         Each complete or partial statement, report or proxy statement included
as an Exhibit to the Placement Memorandum is a true and complete copy of or
excerpt from such document as filed by the Company with the Securities and
Exchange Commission (the "SEC").  The Company has filed in a timely manner all
documents that the Company was required to file with the SEC under Sections 13,
14(a) and 15(d) of the Securities Exchange Act of 1934, as amended (the
"Exchange Act"), during the twelve (12) months preceding the date of this
Agreement.  As of their respective filing dates, all documents filed by the
Company with the SEC (the "SEC Documents") complied in all material respects
with the requirements of the Exchange Act or the Securities Act of 1933, as
amended (the "Securities Act"), as applicable.  Neither the Placement
Memorandum nor any of the SEC Documents as of their respective dates contained
any untrue statement of a material fact or omitted to state a material fact
required to be stated therein or necessary to make the statements made therein,
in light of the circumstances under which they were made, not misleading.  The
financial statements of the Company included in the SEC Documents or the
Placement Memorandum (the "Financial Statements") comply as to form in all
material respects with applicable accounting requirements and with the
published rules and regulations of the SEC with respect thereto.  The Financial
Statements have been prepared in accordance with generally accepted accounting
principles consistently applied and fairly present the financial position of
the Company and any subsidiaries at the dates thereof and the results of their
operations and cash flows for the periods then ended (subject, in the case of
unaudited statements, to normal, recurring adjustments).





                                      -3-
<PAGE>   4

         3.5     GOVERNMENTAL CONSENTS

         No consent, approval, order or authorization of, or registration,
qualification, designation, declaration or filing with, any federal, state or
local governmental authority on the part of the Company is required in
connection with the consummation of the transactions contemplated by this
Agreement except for (a) compliance with the securities and blue sky laws in
the states in which Units are offered and/or sold, which compliance has been or
will be effected in accordance with such laws, (b) the filing of a Form D with
respect to the issuance of the Securities and all amendments thereto with the
SEC, and (c) the filing of the Nasdaq National Market Notification Form
(pursuant to Rule 10b-17 promulgated under the Exchange Act) with the Nasdaq
National Market and Form 10-C with the SEC.

         3.6     EXEMPT TRANSACTIONS

         Subject to the accuracy of the Purchaser's representations and
warranties in Section 4 of this Agreement and to compliance of the Placement
Agents with their obligations with respect to the manner of the offering, the
offer, sale and issuance of the Securities in conformity with the terms of this
Agreement and the Placement Memorandum constitute transactions exempt from the
registration requirements of Section 5 of the Securities Act.

         3.7     NO MATERIAL ADVERSE CHANGE

         Except as otherwise disclosed herein, since December 31, 1994, there
have not been any changes in the assets, liabilities, financial condition,
business prospects or operations of the Company from those reflected in the
Financial Statements, except (a) changes in the ordinary course of business
that have not been, either individually or in the aggregate, materially adverse
and (b) the Company's continued incurrence of operating losses and negative
cash flow.

         3.8     INTELLECTUAL PROPERTY

         To the Company's knowledge, the Company owns or possesses adequate
rights to use all material patents, patent rights, inventions, trade secrets
and know-how described or referred to in the Placement Memorandum as owned or
used by it or that are necessary for the conduct of its business as described
in the Placement Memorandum; neither the Company nor any of its subsidiaries
has received any notice of, or has any knowledge of, any infringement of or
conflict with asserted rights of others with respect to any patent, patent
right, invention, trade secret or know-how that, individually or in the
aggregate, if the subject of an unfavorable decision, ruling or finding, would
have a material adverse effect on the condition





                                      -4-
<PAGE>   5

(financial or otherwise), earnings, operations, business or business prospects
of the Company and its subsidiaries considered as one enterprise.

         3.9     AUTHORIZED CAPITAL STOCK

         The authorized capital stock of the Company conforms, as of the dates
for which such information is given, in all material respects to the statements
relating thereto contained in the Placement Memorandum.  The shares of issued
and outstanding capital stock of the Company set forth thereunder have been
duly authorized, validly issued and are fully paid and nonassessable; except as
set forth or contemplated in the Placement Memorandum or the documents
incorporated therein by reference, no warrants, options or other rights to
purchase, agreements or other obligations to issue, or agreements or other
rights to convert any obligation into, any shares of capital stock of the
Company have been granted or entered into by the Company.

         3.10    LITIGATION

         There are no actions, suits, proceedings or investigations pending or,
to the best of the Company's knowledge, threatened against the Company or any
of its properties before or by any court or arbitrator or any governmental
body, agency or official in which there is a reasonable likelihood (in the
judgment of the Company) of an adverse decision that (a) would have a material
adverse effect on the Company's properties or assets or the business of the
Company as presently conducted or proposed to be conducted or (b) would impair
the ability of the Company to perform in any material respect its obligations
under this Agreement.

         3.11    USE OF PROCEEDS

         The Company will apply the net proceeds from the sales of the Units in
the manner set forth under the caption "Use of Proceeds" in the Placement
Memorandum.

         3.12    PREEMPTIVE AND REGISTRATION RIGHTS

         There are no preemptive rights, rights of first refusal, repurchase
rights or any other right of the Company or any third party as to the
Securities that have not been satisfied or waived and, except as provided in
this Agreement and the Placement Memorandum, the Company has not granted or
agreed to grant any registration rights that would be applicable to the
registration for resale of the Securities pursuant to the Registration
Statement, as defined in and contemplated by Section 7.1 hereof, to any person
or entity that have not been satisfied or waived.





                                      -5-
<PAGE>   6

                                   SECTION 4



           REPRESENTATIONS, WARRANTIES AND COVENANTS OF THE PURCHASER

         The Purchaser hereby represents and warrants to the Company as follows:

         4.1     AUTHORIZATION

         The Purchaser represents and warrants to the Company that:  (a) the
Purchaser has all requisite legal and corporate or other power and capacity and
has taken all requisite corporate or other action to execute and deliver this
Agreement, to purchase the Units to be purchased by it and to carry out and
perform all of its obligations under this Agreement; and (b) this Agreement
constitutes the legal, valid and binding obligation of the Purchaser,
enforceable in accordance with its terms, except (i) as limited by applicable
bankruptcy, insolvency, reorganization or similar laws relating to or affecting
the enforcement of creditors' rights generally and (ii) as limited by equitable
principles generally.

         4.2     INVESTMENT EXPERIENCE

         The Purchaser is an "accredited investor" as defined in Rule 501(a)
under the Securities Act.  The Purchaser is aware of the Company's business
affairs and financial condition and has had access to and has acquired
sufficient information about the Company to reach an informed and knowledgeable
decision to acquire the Units.  The Purchaser has such business and financial
experience as is required to give it the capacity to protect its own interests
in connection with the purchase of the Units.

         4.3     INVESTMENT INTENT

         The Purchaser is purchasing the Units for its own account as
principal, for investment purposes only, and not with a present view to, or
for, resale, distribution or fractionalization thereof, in whole or in part,
within the meaning of the Securities Act.  The Purchaser understands that its
acquisition of the Units has not been registered under the Securities Act or
registered or qualified under any state securities law in reliance on specific
exemptions therefrom, which exemptions may depend upon, among other things, the
bona fide nature of the Purchaser's investment intent as expressed herein.  The
Purchaser has completed or caused to be completed the Purchaser Questionnaire
attached hereto as Appendix I for use in preparation of the Registration
Statement (as defined below), and the responses provided therein shall be true
and correct as of the Closing Date and will be true and correct as of the
effective date of the Registration Statement.  The Purchaser has, in connection
with its decision





                                      -6-
<PAGE>   7

to purchase the number of Units set forth in Schedule 1 hereto, relied solely
upon the Placement Memorandum and the representations and warranties of the
Company contained herein.  The Purchaser will not, directly or indirectly,
offer, sell, pledge, transfer or otherwise dispose of (or solicit any offers to
buy, purchase or otherwise acquire or take a pledge of) any of the Units, the
Shares, the Warrants and the shares of Common Stock underlying the Warrants,
except in compliance with the Securities Act and the rules and regulations
promulgated thereunder.

         4.4     REGISTRATION OR EXEMPTION REQUIREMENTS

         The Purchaser further acknowledges and understands that the Securities
may not be resold or otherwise transferred except in a transaction registered
under the Securities Act or unless an exemption from such registration is
available.  The Purchaser understands that the certificate(s) evidencing the
Securities will be imprinted with a legend that prohibits the transfer of such
securities unless (a) they are registered or such registration is not required
and (b) if the transfer is pursuant to an exemption from registration other
than Rule 144 under the Securities Act and, if the Company shall so request in
writing, an opinion of counsel reasonably satisfactory to the Company is
obtained to the effect that the transaction is so exempt.

         4.5     RESTRICTION ON SHORT SALES

         The Purchaser represents and warrants to and covenants with the
Company that the Purchaser has not engaged and will not engage in any short
sales of the Company's Common Stock prior to the effectiveness of the
Registration Statement, except to the extent that any such short sale is fully
covered by shares of Common Stock of the Company owned by such Purchaser other
than the Shares, the Units or the shares of Common Stock underlying the
Warrants.

         4.6     NO LEGAL, TAX OR INVESTMENT ADVICE

         The Purchaser understands that nothing in the Placement Memorandum,
this Agreement or any other materials presented to the Purchaser in connection
with the purchase and sale of the Units constitutes legal, tax or investment
advice.  The Purchaser has consulted such legal, tax and investment advisors as
it, in its sole discretion, has deemed necessary or appropriate in connection
with its purchase of the Units and understands that each of UBS Securities Inc.
and Vector Securities International, Inc. (collectively, the "Placement
Agents") have acted as placement agents for the Company and not in any of the
foregoing capacities on behalf of the Purchaser.





                                      -7-
<PAGE>   8

                                   SECTION 5

                       CONDITIONS TO CLOSING OF PURCHASER

         The Purchaser's obligation to purchase the Units at the Closing is, at
the option of the  Purchaser, subject to the fulfillment or waiver as of the
Closing Date of the following conditions:

         5.1     REPRESENTATIONS AND WARRANTIES

         The representations and warranties made by the Company in Section 3
hereof shall be true and correct in all material respects when made, and shall
be true and correct in all material respects on the Closing Date with the same
force and effect as if they had been made on and as of said date.

         5.2     COVENANTS

         All covenants, agreements and conditions contained in this Agreement
to be performed by the Company on or prior to the Closing Date shall have been
performed or complied with in all material respects.

         5.3     COMPLIANCE CERTIFICATE

         The President and Chief Financial Officer of the Company shall have
delivered to the Purchaser and the Placement Agents a certificate, dated as of
the Closing Date, certifying that the conditions specified in Sections 5.1 and
5.2 have been fulfilled and stating that there shall have been no material
adverse change in the assets, liabilities, financial condition, business
prospects or operations of the Company from that reflected in the Financial
Statements except (a) changes in the ordinary course of business that have not
been, either individually or in the aggregate, materially adverse and (b) the
Company's continued incurrence of operating losses and negative cash flow.

         5.4     BLUE SKY

         The Company shall have obtained all necessary blue sky law permits and
qualifications, or secured exemptions therefrom, required by any state or
foreign or other jurisdiction for the offer and sale of the Securities.





                                      -8-

<PAGE>   9

         5.5     NASDAQ LISTING

         The Units and the Warrants shall have been approved for listing on the
Nasdaq National Market under the symbols "NERXU" and "NERXW," respectively,
upon notice of issuance.

         5.6     LEGAL OPINION OF PERKINS COIE

         The receipt by the Purchaser of a legal opinion from Perkins Coie,
counsel to the Company, to the effect that:

                 (a)      the Company is a corporation duly incorporated,
validly existing and in good standing under the laws of the jurisdiction of its
incorporation;

                 (b)      the Company has corporate power and authority to
enter into this Agreement and to issue, sell and deliver to the Purchaser the
Units to be issued and sold by it hereunder.  This Agreement has been duly
authorized by all necessary corporate action on the part of the Company and has
been duly executed and delivered by the Company.  The performance by the
Company of this Agreement and the consummation by the Company of the
transactions hereunder contemplated (other than performance of the Company's
indemnification and contribution obligations hereunder, concerning which no
opinion need be expressed) will not (i) contravene any provisions of the
Company's Articles of Incorporation or Bylaws or of any applicable statute,
rule or regulation or (ii) to such counsel's knowledge, result in the breach or
default under any material agreement or instrument to which the Company is a
party or by which it is bound where such breach or default would materially
adversely affect the Company, or, to such counsel's knowledge, any order, writ
or decree of any court or governmental agency or body having jurisdiction over
the Company, or over any of its properties; provided, however, that no opinion
need be rendered concerning state or foreign securities or Blue Sky laws.  This
Agreement constitutes legal, valid and binding obligations of the Company,
enforceable against the Company according to its terms; provided that (x)
enforceability of the indemnification and contribution provisions hereunder may
be limited by applicable law, equitable principles or public policy, (y) such
counsel gives no opinion as to the specific enforceability of any of the
remedies, covenants or other provisions of this Agreement, or upon the
availability of injunctive relief or other equitable remedies, regardless of
whether enforcement of any such agreement is considered a proceeding in equity
or at law, and (z) enforceability may be limited by bankruptcy, insolvency,
reorganization, moratorium or similar laws affecting creditors' rights
generally or by general equitable principles;





                                      -9-
<PAGE>   10

                 (c)      the authorized capital stock of the Company conforms
in all material respects to the statements relating thereto contained in the
Placement Memorandum.  Except as set forth or contemplated in the Placement
Memorandum or the documents incorporated therein by reference, to such
counsel's knowledge, no warrants, options or other rights to purchase,
agreements or other obligations to issue, or agreements or other rights to
convert any obligation into, any shares of capital stock of the Company have
been granted or entered into by the Company.

                 (d)      the Units, the Shares and the Warrants have been duly
authorized, and duly issued and delivered; and the Units, the Shares and the
Warrants conform to the descriptions thereof in the Placement Memorandum; the
certificates evidencing the Securities are in valid and proper legal form; the
Warrants will be exercisable for shares of Common Stock of the Company in
accordance with the terms of the Warrants and at the price therein provided
for; the shares of Common Stock issuable upon exercise of the Warrants have
been duly authorized and reserved for issuance upon such exercise and such
shares, when issued upon such exercise in accordance with the terms of the
Company's Articles of Incorporation and the Warrants, respectively, and when
the price is paid upon exercise of the Warrants, shall be fully paid and
nonassessable;

                 (e)      subject to the accuracy of the Purchaser's
representations and warranties in Section 4 of this Agreement and to compliance
of the Placement Agents with their obligations with respect to the manner of
the offering, the offer, sale and issuance of the Securities in conformity with
the terms of this Agreement and the Placement Memorandum constitute
transactions exempt from the registration requirements of Section 5 of the
Securities Act;

                 (f)      the Units and the Warrants have been approved for
listing on the Nasdaq National Market under the symbols "NERXU" and "NERXW,"
respectively, upon notice of issuance;

                 (g)      to such counsel's knowledge, there are no actions,
suits, proceedings or investigations pending or threatened against the Company
or any of its properties before or by any court or arbitrator or any
governmental body, agency or official in which there is a reasonable likelihood
(in the judgment of counsel) of an adverse decision that (i) would have a
material adverse effect on the Company's properties or assets or the business
of the Company as presently conducted or proposed to be conducted or (ii) would
impair the ability of the Company to perform in any material respect its
obligations under this Agreement; and

                 (h)      there are no preemptive rights, rights of first
refusal, repurchase rights or any other right of the Company or any third party
as to the Securities that





                                      -10-
<PAGE>   11

have not been satisfied or waived, and except as provided in this Agreement and
the Placement Memorandum, the Company has not granted or agreed to grant any
registration rights that would be applicable to the registration for resale of
the Securities pursuant to the Registration Statement, as defined in and
contemplated by Section 7.1 hereof, to any person or entity that have not been
satisfied or waived.

         In addition, such counsel shall also include a statement to the effect
that nothing has come to such counsel's attention that would lead such counsel
to believe that the Placement Memorandum as of the date of the Placement
Memorandum or the date hereof contained or contains any untrue statement of a
material fact or omitted or omits to state a material fact required to be
stated therein or necessary to make the statements made therein, in light of
the circumstances under which they were made, not misleading (except, in each
case, for financial statements and schedules and financial data).

         5.7     LEGAL OPINION OF OFFICER OF THE COMPANY

         The receipt by the Purchaser of a legal opinion from Jeffrey J.
Miller, Senior Vice President, Business Development and Legal Affairs, and
Secretary of the Company, to the effect that:

                 (a)      the shares of issued and outstanding capital stock of
the Company set forth in the Placement Memorandum have been duly authorized,
validly issued and are fully paid and nonassessable; and

                 (b)      except as provided in this Agreement and the
Placement Memorandum, the Company has not granted or agreed to grant any
registration rights that would be applicable to the registration for resale of
the Securities pursuant to the Registration Statement, as defined in and
contemplated by Section 7.1 hereof, to any person or entity that have not been
satisfied or waived.

         5.8     LEGAL OPINION OF BURNS, DOANE, SWECKER & MATHIS

         The receipt by the Purchaser of a legal opinion from Burns, Doane,
Swecker & Mathis, special patent counsel for the Company, regarding certain
patent matters pertaining to the Company's pretargeting technology, and, in
particular, the Company's Avicidin product under development.

         5.9     LEGAL OPINION OF SCHWEGMAN, LUNDBERG & WOESSNER, P.A.

         The receipt by the Purchaser of a legal opinion from Schwegman,
Lundberg & Woessner, P.A., special patent counsel for the Company, regarding
certain patent





                                      -11-
<PAGE>   12

matters pertaining to the Company's antirestenosis products, and, in
particular, the Company's Biostent and Preverex products under development.

                                   SECTION 6

                        CONDITIONS TO CLOSING OF COMPANY

         The Company's obligation to sell and issue the Units at the Closing
is, at the option of the Company, subject to the fulfillment or waiver of the
following conditions:

         6.1     REPRESENTATIONS AND WARRANTIES

         The representations and warranties made by the Purchaser in Section 4
hereof shall be true and correct in all material respects when made, and shall
be true and correct in all material respects on the Closing Date with the same
force and effect as if they had been made on and as of such date.

         6.2     COVENANTS

         All covenants, agreements and conditions contained in this Agreement
to be performed by the Purchaser on or prior to the Closing Date shall have
been performed or complied with in all material respects.

         6.3     BLUE SKY

         The Company shall have obtained all necessary blue sky law permits and
qualifications, or secured exemptions therefrom, required by any state for the
offer and sale of the Securities.

                                   SECTION 7

                      AFFIRMATIVE COVENANTS OF THE COMPANY

         The Company hereby covenants and agrees as follows:

         7.1     REGISTRATION REQUIREMENTS

                 (a)      The Company shall use its best efforts, subject to
receipt of necessary information from the Purchaser, to prepare and file a
registration statement with the SEC under the Securities Act as soon as
reasonably practicable after the Closing to register the resale of the
Securities by the Purchaser (such registration statement, including the
prospectus which is a part thereof, along with amendments





                                      -12-
<PAGE>   13

and supplements thereto, being hereinafter referred to as the "Registration
Statement").

                 (b)      The Company shall pay all Registration Expenses (as
defined below) in connection with any registration, qualification or compliance
hereunder, and the Purchaser shall pay all Selling Expenses (as defined below)
and other expenses that are not Registration Expenses relating to the
Securities resold by the Purchaser.  "Registration Expenses" shall mean all
expenses, except for Selling Expenses, incurred by the Company in complying
with the registration provisions herein described, including, without
limitation, all registration, qualification and filing fees, printing expenses,
escrow fees, fees and disbursements of counsel for the Company, blue sky fees
and expenses and the expense of any special audits incident to or required by
any such registration.  "Selling Expenses" shall mean all selling commissions,
underwriting fees and stock transfer taxes applicable to the Securities and all
fees and disbursements of counsel for the Purchaser.

                 (c)      In the case of the registration effected by the
Company pursuant to these registration provisions, the Company will use its
best efforts to:  (i) keep such registration effective until the earlier of (A)
the third anniversary of the Closing Date, (B) such date as all of the
Securities have been resold, or (C) such time as all of the Securities held by
the Purchaser can be sold within a given three-month period without compliance
with the registration requirements of the Securities Act pursuant to Rule 144;
(ii) prepare and file with the SEC such amendments and post-effective
amendments to the Registration Statement as may be necessary to keep the
Registration Statement effective for the applicable period specified in this
Section 7.1(c); (iii) cause the related prospectus to be supplemented by any
required prospectus supplement, and as so supplemented to be filed pursuant to
Rule 424 (or any similar provisions then in force) under the Securities Act;
(iv)  comply with the provisions of the Securities Act with respect to the
disposition of all securities covered by the Registration Statement during the
applicable period in accordance with the intended methods of disposition by the
sellers thereof set forth in the Registration Statement as so amended or such
prospectus as so supplemented; (v) furnish such number of prospectuses and
other documents incident thereto, including any amendment of or supplement to
the prospectus, as the Purchaser from time to time may reasonably request, and
the Company hereby consents to the use of such prospectus or each amendment and
supplement thereto by each of the selling holders of Securities and the
underwriters, if any, in connection with the offering and sale of the
Securities covered by such prospectus or any amendment or supplement thereto;
(vi) cause all Securities registered as described herein to be listed on each
securities exchange and quoted on each quotation service on which similar
securities issued by the Company are then listed or quoted; (vii) provide a
transfer agent and registrar for





                                      -13-
<PAGE>   14

all Securities registered pursuant to the Registration Statement and a CUSIP
number for all such Securities; (viii) otherwise use its best efforts to comply
with all applicable rules and regulations of the SEC; and (ix) file the
documents required of the Company and otherwise use its best efforts to
maintain requisite blue sky clearance in (A) all jurisdictions in which any of
the Securities are originally sold and (B) all other states specified in
writing by a Purchaser, provided as to clause (B), however, that the Company
shall not be required to qualify to do business or consent to service of
process in any state in which it is not now so qualified or has not so
consented.

                 (d)      The Company shall furnish to the Purchaser upon
request a reasonable number of copies of a supplement to or an amendment of
such prospectus as may be necessary in order to facilitate the public sale or
other disposition of all or any of the Securities held by the Purchaser.

                 (e)      With a view to making available to the Purchaser the
benefits of Rule 144 promulgated under the Securities Act ("Rule 144") and any
other rule or regulation of the SEC that may at any time permit the Purchaser
to sell Securities to the public without registration or pursuant to a
registration on Form S-3, the Company covenants and agrees to:  (i) make and
keep public information available, as those terms are understood and defined in
Rule 144, until the earlier of (A) the third anniversary of the effective date
of the Registration Statement and (B) such date as all of the Securities shall
have been resold; (ii) file with the SEC in a timely manner all reports and
other documents required of the Company under the Securities Act and Exchange
Act; and (iii) furnish to the Purchaser upon request, as long as the Purchaser
owns any Securities, (A) a written statement by the Company that it has
complied with the reporting requirements of the Securities Act and the Exchange
Act, (B) a copy of the most recent annual or quarterly report of the Company,
and (C) such other information as may be reasonably requested in order to avail
the Purchaser of any rule or regulation of the SEC that permits the selling of
any such Securities without registration or pursuant to such Form S-3.

                 (f)      The Company shall notify the Purchaser, if the
Purchaser has registered shares in the Registration Statement which remain
unsold, and (if requested by such Purchaser) confirm such notice in writing,
(i) when a prospectus or any prospectus supplement or post-effective amendment
has been filed, and, with respect to the Registration Statement or any
post-effective amendment, when the same has become effective, (ii) of any
request by the SEC or any other federal or state governmental authority during
the period of effectiveness of the Registration Statement for amendments or
supplements to the Registration Statement or related prospectus or for
additional information relating to the Registration Statement, (iii) of





                                      -14-
<PAGE>   15

the issuance by the SEC or any other federal or state governmental authority of
any stop order suspending the effectiveness of the Registration Statement or
the initiation of any proceedings for that purpose, (iv) of the receipt by the
Company of any notification with respect to the suspension of the qualification
or exemption from qualification of any of the Securities for sale in any
jurisdiction or the initiation or threatening of any proceeding for such
purpose, (v) of the happening of any event which makes any statement made in
the Registration Statement or related prospectus or any document incorporated
or deemed to be incorporated therein by reference untrue in any material
respect or which requires the making of any changes in the Registration
Statement or prospectus so that, in the case of the Registration Statement, it
will not contain any untrue statement of a material fact or omit to state any
material fact required to be stated therein or necessary to make the statements
therein not misleading, and that in the case of the prospectus, it will not
contain any untrue statement of a material fact or omit to state any material
fact or omit to state any material fact required to be stated therein or
necessary to make the statements therein, in the light of the circumstances
under which they were made, not misleading, and (vi) of the Company's
reasonable determination that a post-effective amendment to the Registration
Statement would be appropriate.

                 (g)      The Company may, upon written notice to the Purchaser
of (i) the happening of any event of the kind described in Section 7.1(f)(ii),
7.1(f)(iii), 7.1(f)(iv), 7.1(f)(v) or 7.1(f)(vi) hereof or (ii) that, in the
judgment of the Company's Board of Directors, it is advisable to suspend use of
the prospectus for a discrete period of time due to pending corporate
developments, public filings with the SEC or similar events, discontinue
disposition of Securities covered by the Registration Statement or prospectus
until copies of the supplemented or amended prospectus contemplated by Section
7.1(i) hereof are distributed to the Purchaser, or until the Purchaser is
advised in writing by the Company that the use of the applicable prospectus may
be resumed, and the Purchaser has received copies of any additional or
supplemental filings that are incorporated or deemed incorporated by reference
in such prospectus.  The Company shall use its reasonable efforts to ensure
that the use of the prospectus may be resumed as soon as practicable.

                 (h)      The Company shall use every reasonable effort to
obtain the withdrawal of any order suspending the effectiveness of the
Registration Statement, or the lifting of any suspension of the qualification
(or exemption from qualification) of any of the Securities for sale in any
jurisdiction, at the earliest possible moment.

                 (i)      The Company shall, upon the occurrence of any event
contemplated by Section 7.1(f)(v) or 7.1(f)(vi) above, prepare a supplement or
post-effective amendment to the Registration Statement or a supplement to the
related





                                      -15-
<PAGE>   16

prospectus or any document incorporated therein by reference or file any other
required document so that, as thereafter delivered to the purchasers of the
Securities being sold thereunder, such prospectus will not contain an untrue
statement of a material fact or omit to state a material fact required to be
stated therein or necessary to make the statements therein, in light of the
circumstances under which they were made, not misleading.

                 (j)      Without the prior written consent of the Placement
Agents, for a period of 90 days following the Closing, the Company shall not
issue, sell or register with the SEC or otherwise dispose of, directly or
indirectly, any equity securities of the Company (or any securities convertible
into or exercisable or exchangeable for equity securities of the Company),
except for the Securities upon the terms and conditions set forth herein and in
the Placement Memorandum, the conversion or exercise of existing stock options
or currently outstanding warrants, debt or other equity securities of the
Company, and the issuance of securities under the Company's stock benefit
plans.

                 (k)      The Company shall use its best efforts to cause each
of its directors and executive officers to agree with the Placement Agents that
each of such persons will not, directly or indirectly, offer to sell, sell,
contract to sell, grant any option to purchase, make any short sale or
otherwise dispose of any equity securities of the Company, or any options,
warrants or other rights to purchase equity securities of the Company for a
period of 90 days following the Closing; provided that, it is understood that
40,000 shares of such equity securities owned by Paul Abrams are subject to
margin accounts with Key Bank and Seafirst Bank.  The Company shall also use
its best efforts to cause Boehringer Ingelheim International GmbH to likewise
agree to such limitations for 90 days following the Closing.

         7.2     INDEMNIFICATION AND CONTRIBUTION

                 (a)      The Company agrees to indemnify and hold harmless the
Purchaser from and against any losses, claims, damages or liabilities (or
actions or proceedings in respect thereof) to which the Purchaser may become
subject (under the Securities Act or otherwise) insofar as such losses, claims,
damages or liabilities (or actions or proceedings in respect thereof) arise out
of, or are based upon, any untrue statement or alleged untrue statement of any
material fact contained in the Registration Statement or arise out of or are
based upon the omission or alleged omission to state therein a material fact
required to be stated therein or necessary to make the statements therein not
misleading, or arise out of any failure by the Company to fulfill any
undertaking included in the Registration Statement, and the Company will, as
incurred, reimburse the Purchaser for any legal or other expenses reasonably
incurred in investigating, defending or preparing to defend any such





                                      -16-
<PAGE>   17

action, proceeding or claim; provided, however, that the Company shall not be
liable in any such case to the extent that such loss, claim, damage or
liability arises out of, or is based upon (i) an untrue statement or alleged
untrue statement or an omission or alleged omission made in such Registration
Statement in reliance upon and in conformity with written information furnished
to the Company by or on behalf of the Purchaser specifically for use in
preparation of the Registration Statement, (ii) the failure of the Purchaser to
comply with the covenants and agreements contained in Section 8.3 hereof, or
(iii) any untrue statement or alleged untrue statement of a material fact or
the omission or alleged omission of a material fact in any prospectus that is
corrected in any subsequent prospectus that was delivered to the Purchaser
prior to the pertinent sale or sales by the Purchaser.

                 (b)      Purchaser agrees to indemnify and hold harmless the
Company from and against any losses, claims, damages or liabilities (or actions
or proceedings in respect thereof) to which the Company may become subject
(under the Securities Act or otherwise) insofar as such losses, claims, damages
or liabilities (or actions or proceedings in respect thereof) arise out of, or
are based upon (i) an untrue statement or an alleged untrue statement of a
material fact made in such Registration Statement or the omission or alleged
omission to state therein a material fact required to be stated therein or
necessary to make the statements therein not misleading, in reliance upon and
in conformity with written information furnished to the Company by or on behalf
of the Purchaser specifically for use in preparation of the Registration
Statement, provided, however, that the Purchaser shall not be liable in any
such case for any untrue statement or alleged untrue statement or the omission
or alleged omission that has been corrected, in writing, by the Purchaser,
delivered to the Company at least two (2) business days before the sale from
which such loss occurred, (ii) the failure of the Purchaser to comply with the
covenants and agreements contained in Section 8.3 hereof, or (iii) any untrue
statement or alleged untrue statement or the omission or alleged omission in
any prospectus that is corrected in any subsequent prospectus that was
delivered to the Purchaser prior to the pertinent sale or sales by the
Purchaser, and the Purchaser will, as incurred, reimburse the Company for any
legal or other expenses reasonably incurred in investigating, defending or
preparing to defend any such action, proceeding or claim.

                 (c)      Promptly after receipt by any indemnified person of a
notice of a claim or the beginning of any action in respect of which indemnity
is to be sought against an indemnifying person pursuant to this Section 7.2,
such indemnified person shall notify the indemnifying person in writing of such
claim or of the commencement of such action, and, subject to the provisions
hereinafter stated, in case any such action shall be brought against an
indemnified person and the indemnifying person shall have been notified
thereof, the indemnifying person shall be entitled to





                                      -17-
<PAGE>   18

participate therein, and, to the extent that it shall wish, to assume the
defense thereof, with counsel reasonably satisfactory to the indemnified
person.  After notice from the indemnifying person to such indemnified person
of the indemnifying person's election to assume the defense thereof, the
indemnifying person shall not be liable to such indemnified person for any
legal expenses subsequently incurred by such indemnified person in connection
with the defense thereof; provided, however, that if there exists or shall
exist a conflict of interest that would make it inappropriate in the reasonable
judgment of the indemnified person for the same counsel to represent both the
indemnified person and such indemnifying person or any affiliate or associate
thereof, the indemnified person shall be entitled to retain its own counsel at
the expense of such indemnifying person.

                 (d)      If the indemnification provided for in this Section
7.2 is unavailable to or insufficient to hold harmless an indemnified party
under subsection (a) or (b) above in respect of any losses, claims, damages or
liabilities (or actions or proceedings in respect thereof) referred to therein,
then each indemnifying party shall contribute to the amount paid or payable by
such indemnified party as result of such losses, claims, damages or liabilities
(or actions in respect thereof) in such proportion as is appropriate to reflect
the relative fault of the Company on the one hand and the Purchaser on the
other in connection with the statements or omissions which resulted in such
losses, claims, damages or liabilities (or actions in respect thereof), as well
as any other relevant equitable considerations.  The relative fault shall be
determined by reference to, among other things, whether the untrue or alleged
untrue statement of a material fact or the omission or alleged omission to
state a material fact relates to information supplied by the Company on the one
hand or the Purchaser on the other and the parties' relative intent, knowledge,
access to information and opportunity to correct or prevent such statement or
omission.  The Company and the Purchaser agree that it would not be just and
equitable if contribution pursuant to this subsection (d) were determined by
pro rata allocation (even if the Purchaser were treated as one entity for such
purpose) or by any other method of allocation which does not take account of
the equitable considerations referred to above in this subsection (d).  The
amount paid or payable by an indemnified party as a result of the losses,
claims, damages, or liabilities (or actions in respect thereof) referred to
above in this subsection (d) shall be deemed to include any legal or other
expenses reasonably incurred by such indemnified party in connection with
investigating or defending any such action or claim.  Notwithstanding the
provisions of this subsection (d), the Purchaser shall not be required to
contribute any amount in excess of the amount by which the net amount received
by the Purchaser from the sale of the Securities to which such loss relates
exceeds the amount of any damages that the Purchaser has otherwise been
required to pay by reason of such untrue or alleged untrue statement or
omission or alleged omission.  No person guilty





                                      -18-
<PAGE>   19

of fraudulent misrepresentation (within the meaning of Section 11(f) of the
Securities Act) shall be entitled to contribution from any person who was not
guilty of such fraudulent misrepresentation.  The Purchaser's obligations in
this subsection (d) to contribute is several in proportion to its sale of
Securities to which such loss relates, not joint.

                 (e)      The obligations of the Company and the Purchaser
under this Section 7.2 shall be in addition to any liability that the Company
and the Purchaser may otherwise have and shall extend, upon the same terms and
conditions, to each person, if any, who controls the Company or the Purchaser
within the meaning of the Securities Act.

                                   SECTION 8


                 RESTRICTIONS ON TRANSFERABILITY OF SECURITIES:
                         COMPLIANCE WITH SECURITIES ACT

         8.1     RESTRICTIONS ON TRANSFERABILITY

         The Units, the Shares, the Warrants and the shares of Common Stock
issuable upon exercise of the Warrants shall not be transferable in the absence
of a registration under the Securities Act or an exemption therefrom or in the
absence of compliance with any term of this Agreement.  The Company shall be
entitled to give stop transfer instructions to its transfer agent with respect
to the foregoing securities in order to enforce the foregoing restrictions.

         8.2     RESTRICTIVE LEGEND

         Each certificate representing the Securities shall bear substantially
the following legends (in addition to any legends required under applicable
securities laws):

         THE SECURITIES REPRESENTED HEREBY HAVE BEEN ACQUIRED FOR INVESTMENT
         PURPOSES ONLY AND HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF
         1933, AS AMENDED.  THE SECURITIES MAY NOT BE SOLD OR TRANSFERRED IN
         THE ABSENCE OF SUCH REGISTRATION OR AN EXEMPTION THEREFROM.

         ADDITIONALLY, THE TRANSFER OF THE SECURITIES REPRESENTED HEREBY IS
         SUBJECT TO CERTAIN RESTRICTIONS SPECIFIED IN THE PURCHASE AGREEMENT
         DATED AS OF





                                      -19-
<PAGE>   20

         APRIL 18, 1995 BETWEEN THE COMPANY AND THE ORIGINAL PURCHASER, AND NO
         TRANSFER OF THE SECURITIES SHALL BE VALID OR EFFECTIVE ABSENT
         COMPLIANCE WITH SUCH RESTRICTIONS.  ALL SUBSEQUENT HOLDERS OF THESE
         SECURITIES WILL HAVE AGREED TO BE BOUND BY CERTAIN OF THE TERMS OF THE
         AGREEMENT, INCLUDING SECTIONS 7.1 AND 8.3.  COPIES OF THE PURCHASE
         AGREEMENT MAY BE OBTAINED AT NO COST BY WRITTEN REQUEST MADE BY THE
         REGISTERED HOLDER OF THIS CERTIFICATE TO THE SECRETARY OF THE COMPANY.

         The legend contained in this Section 8.2 may be removed from a
certificate immediately upon receipt by the Company's transfer agent of a
certificate substantially in the form annexed hereto as Appendix II.

         8.3     TRANSFER OF SECURITIES AFTER REGISTRATION

         The Purchaser hereby covenants with the Company not to make any sale
of the Units, the Shares, the Warrants or the shares of Common Stock issuable
upon exercise of the Warrants except either (a) in accordance with the
Registration Statement, in which case the  Purchaser covenants to comply with
the requirement of delivering a current prospectus, or (b) in accordance with
Rule 144, in which case the Purchaser covenants to comply with Rule 144.  The
Purchaser further acknowledges and agrees that such securities are not
transferable on the books of the Company unless the certificate submitted to
the Company's transfer agent evidencing such securities is accompanied by a
separate certificate executed by an officer of, or other person duly authorized
by, the Purchaser in the form annexed hereto as Appendix III.

         8.4     PURCHASER INFORMATION

         The Purchaser covenants that it will promptly notify the Company of
any changes in the information set forth in the Registration Statement
regarding the Purchaser, under the heading "Selling Security Holders" or
elsewhere, or the Purchaser's "Plan of Distribution."

                                   SECTION 9

                                 MISCELLANEOUS

         9.1     WAIVERS AND AMENDMENTS

         Neither this Agreement nor any provisions hereof shall be waived,
modified, changed or discharged or terminated except by an instrument in
writing signed by the





                                      -20-
<PAGE>   21

party against whom any waiver, modification, change, discharge or termination
is sought.

         9.2     BROKER'S FEE

         The Purchaser acknowledges that the Company intends to pay a fee to
UBS Securities Inc. and Vector Securities International, Inc. in respect of the
sale of the Units to the Purchaser.  Each of the parties hereto hereby
represents that, on the basis of any actions and agreements by it, there are no
other brokers or finders entitled to compensation in connection with the sale
of the Units to the Purchaser.

         9.3     GOVERNING LAW

         This Agreement shall be governed in all respects by and construed in
accordance with the laws of the state of Washington without any regard to
conflicts of laws principles.

         9.4     SURVIVAL

         The representations, warranties, covenants and agreements made in this
Agreement shall survive any investigation made by the Company or the Purchaser
and the Closing.

         9.5     SUCCESSORS AND ASSIGNS

         The provisions hereof shall inure to the benefit of, and be binding
upon, the successors, assigns, heirs, executors and administrators of the
parties to this Agreement.  Notwithstanding the foregoing, the Purchaser shall
not assign this Agreement without the prior written consent of the Company.

         9.6     ENTIRE AGREEMENT

         This Agreement, including all exhibits, schedules and appendices
hereto, constitutes the full and entire understanding and agreement between the
parties with regard to the subjects thereof.

         9.7     NOTICES, ETC.

         All notices and other communications required or permitted under this
Agreement shall be effective upon receipt and shall be in writing and may be
delivered in person, by telecopy, overnight delivery service or registered or
certified United States mail, addressed to the Company or the Purchaser, as the
case may be, at their respective addresses set forth at the beginning of this
Agreement or on





                                      -21-
<PAGE>   22

Schedule 1, or at such other address as the Company or the Purchaser shall have
furnished to the other party in writing.  All notices and other communications
shall be effective upon the earlier of actual receipt thereof by the person to
whom notice is directed or (a) in the case of notices and communications sent
by personal delivery or telecopy, one business day after such notice or
communication arrives at the applicable address or was successfully sent to the
applicable telecopy number, (b) in the case of notices and communications sent
by overnight delivery service, at noon (local time) on the second business day
following the day such notice or communication was sent, and (c) in the case of
notices and communications sent by United States mail, seven days after such
notice or communication shall have been deposited in the United States mail.

         9.8     SEVERABILITY OF THIS AGREEMENT

         If any provision of this Agreement shall be judicially determined to
be invalid, illegal or unenforceable, the validity, legality and enforceability
of the remaining provisions shall not in any way be affected or impaired
thereby.

         9.9     COUNTERPARTS

         This Agreement may be executed in any number of counterparts, each of
which shall be an original, but all of which together shall constitute one
instrument.

         9.10    FURTHER ASSURANCES

         Each party to this Agreement shall do and perform or cause to be done
and performed all such further acts and things and shall execute and deliver
all such other agreements, certificates, instruments and documents as the other
party hereto may reasonably request in order to carry out the intent and
accomplish the purposes of this Agreement and the consummation of the
transactions contemplated hereby.

         9.11    TERMINATION

         In the event that the Closing shall not have occurred on or before 90
days from the date hereof, this Agreement shall terminate at the close of
business on such date.

         9.12    EXPENSES

         The Company and the Purchaser shall bear its own expenses incurred on
its behalf with respect to this Agreement and the transactions contemplated
hereby, including fees of legal counsel.





                                      -22-
<PAGE>   23

         9.13    CURRENCY

         All references to "dollars" or "$" in this Agreement shall be deemed
to refer to United States dollars.

         The foregoing agreement is hereby executed as of the date first above
written.

                                                   "COMPANY"

                                                   NEORX CORPORATION
                                                   a Washington corporation



                                                   By: ______________________
                                                       
                                                        Title: ______________ 



                                                   "PURCHASER"

                                                   Name: ____________________


                                                   By: ______________________

                                                        Title: ______________





                                      -23-
<PAGE>   24
                                   EXHIBIT A

                                    WARRANT





                                      -24-
<PAGE>   25
                                   SCHEDULE 1
                                     TO THE
                               PURCHASE AGREEMENT



1.       NO. OF UNITS TO BE PURCHASED:

2.       PURCHASE PRICE PER UNIT:            US$5.3125

3.       TOTAL PURCHASE PRICE:                     US$

4.       NAME, ADDRESS AND FACSIMILE NUMBER OF PURCHASER:





5.       NUMBER OF CERTIFICATES:

6.       NUMBER OF WARRANTS:

7.       DENOMINATION OF INDIVIDUAL CERTIFICATE(S) AND EXACT NAME(S) IN WHICH
         STOCK CERTIFICATE(S) AND WARRANTS SHOULD BE REGISTERED:



<TABLE>
                    <S>                       <C>                       <C>
                    CERTIFICATE NO.           DENOMINATION              NAME TO APPEAR ON CERTIFICATE
                    ---------------           ------------              -----------------------------
</TABLE>





                                      -25-
<PAGE>   26
                                   SCHEDULE 1
                                     TO THE
                               PURCHASE AGREEMENT



<TABLE>
                    <S>                       <C>                       <C>
                    WARRANT NO.               DENOMINATION              NAME TO APPEAR ON WARRANT
                    -----------               ------------              -------------------------
</TABLE>


8.       DELIVER CERTIFICATES AND WARRANTS TO:





                                      -26-
<PAGE>   27
                                   APPENDIX I
                                     TO THE
                               PURCHASE AGREEMENT

                               NEORX CORPORATION
                            PURCHASER QUESTIONNAIRE

         In connection with the preparation of the Registration Statement,
please provide us with the following information regarding the Purchaser:

1.       Please state your organization's name exactly as it should appear in
         the Registration Statement:

________________________________________________________________________________

2.       Have you or your organization had any position, office or other
material relationship within the past three years with the Company or its
affiliates other than as disclosed in the Prospectus included in the
Registration Statement?

__________  Yes           __________  No

If yes, please indicate the nature of any such relationship below:

________________________________________________________________________________

________________________________________________________________________________

3.       Do you own any securities of the Company, other than those shares of
Common Stock, Units or Warrants to be sold pursuant to the Registration
Statement?

__________  Yes           __________  No

If yes, please indicate class of security and number of shares owned below:

________________________________________________________________________________

________________________________________________________________________________






                                      -27-
<PAGE>   28

                                  APPENDIX II
                                     TO THE
                               PURCHASE AGREEMENT

                               NEORX CORPORATION
                     PURCHASER'S LEGEND REMOVAL CERTIFICATE

To:      First Interstate Bank of Washington, N.A.

         Attention:

        The undersigned, the Purchaser or an officer of, or other person duly
authorized by the Purchaser, hereby certifies that ___________________________
                                                   [fill in name of Purchaser]
was the Purchaser of the shares evidenced by the attached certificate, and in
order to induce the Company to remove the legends contained on the certificates
representing the Common Stock purchased by such Purchaser, Purchaser will sell
such shares (i) in accordance with the registration statement, file number
_______, in which case the Purchaser will satisfy the requirement of delivering
a current prospectus in connection with such sale, or (ii) in accordance with
Rule 144 under the Securities Act of 1933, as amended ("Rule 144"), in which
case the Purchaser certifies that it has complied with or will comply with the
requirements of Rule 144.

Print or type:

         Name of Purchaser:            ____________________________
                                       
         Name of Individual                                        
           representing                
           Purchaser (if an
           Institution):               ____________________________

         Title of Individual
           representing
           Purchaser (if an
           Institution):               ____________________________


Signature by:

         Purchaser or 
           Individual representing 
           Purchaser:                  ____________________________






                                      -28-
<PAGE>   29
                                  APPENDIX III
                                     TO THE
                               PURCHASE AGREEMENT

                               NEORX CORPORATION
                   PURCHASER'S CERTIFICATE OF SUBSEQUENT SALE

Attention:

        The undersigned, the Purchaser or an officer of, or other person duly
authorized by the Purchaser, hereby certifies that ___________________________
                                                   [fill in name of Purchaser]
was the Purchaser of the shares evidenced by the attached certificate and, as
such, proposes to transfer such shares on or about __________ either (i) in
                                                     [date] 
accordance with the registration statement, file number _______, in which case
the Purchaser certifies that the requirement of delivering a current prospectus
has been complied with or will be complied with in connection with such sale,
or (ii) in accordance with Rule 144 under the Securities Act of 1933, as
amended ("Rule 144"), in which case the Purchaser certifies that it has
complied with or will comply with the requirements of Rule 144.

Print or type:

         Name of Purchaser:            ____________________________


         Name of Individual
           representing
           Purchaser (if an
           Institution):               ____________________________






                                      -29-
<PAGE>   30

         Title of Individual
           representing
           Purchaser (if an
           Institution):               ____________________________


Signature by:

         Purchaser or
         Individual representing
         Purchaser:                    ____________________________






                                      -30-

<PAGE>   1

deem appropriate, the Company has filed with the Commission under the
Securities Act the Registration Statement with respect to the resale of the
Securities from time to time in transactions in the over-the-counter market
through Nasdaq, in privately negotiated transactions, through the writing of
options on the Securities, or through a combination of such methods of sale and
has agreed to prepare and file such amendments and supplements to the
Registration Statement as may be necessary to keep the Registration Statement
effective for three years from its effective date.

                              PLAN OF DISTRIBUTION

         The resale of the Securities by the Selling Security Holders may be
effected from time to time in transactions in the over-the-counter market
through Nasdaq, in privately negotiated transactions, through the writing of
options on the Securities, or through a combination of such methods of sale, at
fixed prices that may be changed, at market prices prevailing at the time of
sale, at prices relating to such prevailing market prices or at negotiated
prices.   The Selling Security Holders may effect such transactions by selling
the Securities to or through broker-dealers, and such broker-dealers may
receive compensation in the form of discounts, concessions or commissions from
the Selling Security Holders and/or the purchasers of the Securities for whom
such broker-dealers may act as agents or to whom they may sell as principals,
or both (which compensation as to a particular broker-dealer may be in excess
of customary commissions).  Any broker-dealer may act as a broker-dealer on
behalf of one or more of the Selling Security Holders in connection with the
offering of certain of the Securities by the Selling Security Holders.  None of
the proceeds from the sale of the Securities by the Selling Security Holders
will be received by the Company.  In addition, any of the Securities that
qualify for sale pursuant to Rule 144 promulgated under the Securities Act may
be sold in transactions complying with such Rule, rather than pursuant to this
prospectus.

         The Selling Security Holders and any broker-dealers who act in
connection with the sale of the Securities hereunder may be deemed to be
"underwriters" within the meaning of Section 2(11) of the Securities Act, and
any commissions received by them and profit on any resale of the Securities as
principal might be deemed to be underwriting discounts and commissions under
the Securities Act.  The Company has agreed to bear all expenses (other than
selling commissions and fees and expenses of counsel and other advisers to the
Selling Security Holders) in connection with the registration and sale of the
Securities being offered by the Selling Security Holders.  The Company has
agreed to indemnify the Selling Security Holders against certain liabilities,
including liabilities under the Securities Act.

         There can be no assurance that the Selling Security Holders will sell
any or all of the Securities offered by them hereunder.

                          DESCRIPTION OF THE WARRANTS

         The Company sold 1,323,471 Units, each Unit consisting of one share of
Common Stock and one Warrant to purchase one-quarter of one share of Common
Stock, to the Selling Security Holders in private transactions in April 1995.
Every four Warrants entitle the registered holder thereof to purchase one share
of Common Stock at a price of $5.3125 (the "Stock Purchase Price").  The
Warrants will be exercisable from October 25, 1995 through April 25, 1998.

         The Stock Purchase Price and, in some cases, the number of shares of
Common Stock issuable upon exercise of the Warrants will be appropriately
adjusted in the event of stock splits, stock combinations, rights offerings or
stock or other dividends involving the Common Stock.  Fractional shares will
not be issued upon exercise of the Warrants and, in lieu thereof, a cash
adjustment based on the fair market value of the Common Stock as reported on
the Nasdaq National Market (or as reported on a national securities exchange,
if applicable) on the date of exercise will be made.

         In case of any reclassification or capital reorganization, or in case
of any consolidation or merger of NeoRx with or into another corporation or any
sale, lease or transfer to another corporation of all or substantially





                                          -10-
<PAGE>   2

all the assets of NeoRx, the holder of each of the outstanding Warrants will
have the right, upon subsequent exercise of a Warrant, to purchase the kind and
amount of shares of stock or other securities and property receivable upon such
reclassification, capital reorganization, consolidation, merger, sale, lease or
transfer by a holder of the number of shares of Common Stock that might have
been received upon the exercise of such Warrant immediately prior thereto, and
the Stock Purchase Price will be appropriately adjusted.  The Warrants do not
confer on the holder any voting or preemptive rights, or any other rights as a
stockholder of NeoRx.

         The Warrants may be exercised in whole or in part by the surrender of
the Warrants to the Company at the principal office of First Interstate Bank of
Washington, N.A. in Seattle, Washington or at the principal office of the
Company in Seattle, Washington, with the form of election to exercise set forth
on the back of the Warrant certificate duly completed and signed, and
accompanied by cash or a cashier's check (or by bank wire transfer of
immediately available funds) in the amount of the Stock Purchase Price
multiplied by the number of shares of Common Stock to be acquired pursuant to
such exercise.

                          DESCRIPTION OF CAPITAL STOCK

         The Company is authorized to issue 60,000,000 shares of Common Stock,
$.02 par value per share, and 3,000,000 shares of Series Preferred Stock, $.02
par value per share.
COMMON STOCK

         The holders of Common Stock are entitled to one vote per share for
each share held of record on all matters submitted to a vote of Security
Holders, except that in elections of directors shareholders are entitled to
cumulate votes by multiplying the number of votes they are entitled to cast by
the number of directors for whom they are entitled to vote and cast the product
for a single candidate or distribute the product among two or more candidates.
The holders of Common Stock are entitled to receive ratably such dividends as
are declared by the Company's Board of Directors out of funds legally available
therefor.  In the event of a liquidation, dissolution or winding up of the
Company, holders of Common Stock have the right to a ratable portion of assets
remaining after payment of liabilities and the liquidation preferences of any
outstanding shares of Series Preferred Stock.  The holders of Common Stock have
no preemptive rights or rights to convert their Common Stock into any other
securities and are not subject to future calls or assessments by the Company.
All outstanding shares of Common Stock are, and the shares issuable upon
conversion of the Series Preferred Stock or upon the conversion of debentures
upon issuance and exchange will be, fully paid and nonassessable.  At March 31,
1994, there were approximately 11.9 million shares of Common Stock outstanding
held of record by approximately 1,100 holders.

TRANSFER AGENT

         The transfer agent and registrar for the Common Stock is First
Interstate Bank of Washington, N.A.

SERIES PREFERRED STOCK

         The Company is authorized to issue 3,000,000 shares of Series
Preferred Stock, par value $.02 per share, of which 298,000 shares of its
$2.4375 Convertible Exchangeable Preferred Stock, Series 1 (the "Preferred
Stock"), is outstanding.  If declared by the Company's Board of Directors,
holders of Preferred Stock are entitled to receive an annual cash dividend of
$2.4375 per share, payable on June 1 and December 1.  Dividends are cumulative.
Each share of Preferred Stock is convertible into approximately 1.14 shares of
Common Stock, subject to adjustment in certain events.  The Preferred Stock is
redeemable at the Company's option at certain redemption prices, initially
$27.44 per share, reducing to $25.00 per share by 1999.  The holders of
Preferred Stock have no voting rights, except in limited circumstances.  The
Board of Directors may, without further action by the Company's shareholders,
issue additional Series Preferred Stock in one or more series and fix all the
rights and preferences thereof, including dividend rights, dividend rates,
conversion rights, voting rights, terms of redemption, redemption price or
prices, liquidation preferences and the number of shares constituting any
series or the designations of such series.





                                          -11-
<PAGE>   3

ANTITAKEOVER PROVISIONS

         Certain provisions of the Company's Restated Articles of Incorporation
and Restated Bylaws, as well as the Washington Business Corporation Act, could
discourage a third party from attempting to acquire, or make it more difficult
for a third party to acquire, control of the Company without approval of the
Company's Board of Directors.  Such provisions could also limit the price that
certain investors might be willing to pay in the future for shares of Common
Stock.  Certain of such provisions allow the Board of Directors to authorize
the issuance of preferred stock with rights superior to those of the Common
Stock.  The rights of the holders of Common Stock will be subject to, and may
be adversely affected by, the rights of holders of any Series Preferred Stock
issued in the future.  The issuance of additional Series Preferred Stock, while
providing desirable flexibility in connection with possible acquisitions and
other corporate purposes, could make it more difficult for a party to acquire,
or discourage a party from acquiring, a majority of the outstanding voting
stock of the Company.  The Company is also subject to the provisions of Chapter
23B.19 of the Washington Business Corporation Act, which generally prohibits
any "significant business transactions" within five years of the date a person
acquires 10% or more of the outstanding voting shares of a Washington
corporation unless the transaction or the acquisition is approved prior to the
acquisition date by a majority of a corporation's then board of directors.  In
addition, the Company is subject to the "fair price" provisions of Chapter
23B.17 of the Washington Business Corporation Act, which generally prohibits
"interested shareholder transactions" (such as a merger, sale of assets or
liquidation) with a person who beneficially owns 20% or more of a corporation's
outstanding voting securities, unless approved by a majority vote of
disinterested directors or a two-thirds vote of disinterested shareholders.

                                 LEGAL MATTERS

         The validity of the Securities being offered hereby has been passed
upon for the Company by Perkins Coie, 1201 Third Avenue, 40th Floor, Seattle,
Washington.

                                    EXPERTS
 
         The audited financial statements incorporated by reference in this
Prospectus and elsewhere in the Registration Statement have been audited by
Arthur Andersen LLP, independent public accountants, as indicated in their
report with respect thereto, and are incorporated by reference herein in
reliance upon the authority of said firm as experts in giving said reports.





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