AVI BIOPHARMA INC
S-3/A, 2000-02-29
PHARMACEUTICAL PREPARATIONS
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   AS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION ON FEBRUARY 29, 2000


                                                      REGISTRATION NO. 333-93135
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- --------------------------------------------------------------------------------

                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON. D.C. 20549
                            ------------------------


                                AMENDMENT NO. 2
                                       TO
                                    FORM S-3
                             REGISTRATION STATEMENT
                                     UNDER
                           THE SECURITIES ACT OF 1933

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

                              AVI BIOPHARMA, INC.
             (Exact name of registrant as specified in its charter)

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                          OREGON                                                     93-0797222
              (State or other jurisdiction of                           (I.R.S. Employer Identification No.)
              incorporation or organization)
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               ONE S.W. COLUMBIA, SUITE 1105, PORTLAND, OR 97258
                                 (503) 227-0554
              (Address, including zip code, and telephone number,
        including area code of registrant's principal executive offices)

                             DENIS R. BURGER, PH.D.
                      PRESIDENT & CHIEF EXECUTIVE OFFICER
                              AVI BIOPHARMA, INC.
               ONE S.W. COLUMBIA, SUITE 1105, PORTLAND, OR 97258
                                 (503) 227-0554
           (Name, address, including zip code, and telephone number,
                   including area code of agent for service)
                         ------------------------------

                                    COPY TO:

                            BYRON W. MILSTEAD, ESQ.
                                 ATER WYNNE LLP
             222 S.W. COLUMBIA, SUITE 1800, PORTLAND, OR 97201-6618
                         ------------------------------

          APPROXIMATE DATE OF COMMENCEMENT OF PROPOSED SALE TO PUBLIC:
AS SOON AS PRACTICABLE AFTER THE EFFECTIVE DATE OF THIS REGISTRATION STATEMENT.
                         ------------------------------

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

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

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

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

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

                        CALCULATION OF REGISTRATION FEE


<TABLE>
<CAPTION>
                                                                    PROPOSED MAXIMUM     PROPOSED MAXIMUM
            TITLE OF SECURITIES                    AMOUNT TO         OFFERING PRICE          AGGREGATE            AMOUNT OF
              TO BE REGISTERED                   BE REGISTERED        PER SHARE(1)        OFFERING PRICE      REGISTRATION FEE
<S>                                           <C>                  <C>                  <C>                  <C>
(a) Common Stock, $.0001 par value(2).......       2,857,147             $13.63             $38,942,914            $10,282
(b) Common Stock, $.0001 par value(3)(4)....        557,144              $13.63             $7,593,873             $2,005
    TOTAL...................................                                                $46,536,787          $12,286(5)
</TABLE>


(1) The offering price is estimated solely for the purpose of calculating the
    registration fee in accordance with Rule 457(c) using the average of the
    high and low price reported by the Nasdaq National Market for the Common
    Stock on January 20, 2000, which was approximately $13.63 per share.

(2) An indeterminate number of shares of Common Stock are registered under this
    Registration Statement that may be issued, as provided in the Purchase
    Agreement to prevent dilution resulting from stock splits, stock dividends
    or similar transactions. No additional registration fee is included for
    these shares.

(3) Issuable upon the exercise of Common Stock Purchase Warrants held by
    existing shareholders of AVI BioPharma, Inc. who are the selling
    shareholders under this Registration Statement.

(4) An indeterminate number of shares of Common Stock are registered under this
    Registration Statement that may be issued, as provided in the Common Stock
    Purchase Warrants to prevent dilution resulting from stock splits, stock
    dividends or similar transactions. No additional registration fee is
    included for these shares.


(5) Previously paid.

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

    THE REGISTRANT HEREBY AMENDS THIS REGISTRATION STATEMENT ON SUCH DATE OR
DATES AS MAY BE NECESSARY TO DELAY ITS EFFECTIVE DATE UNTIL THE REGISTRANT SHALL
FILE A FURTHER AMENDMENT WHICH SPECIFICALLY STATES THAT THIS REGISTRATION
STATEMENT SHALL THEREAFTER BECOME EFFECTIVE IN ACCORDANCE WITH SECTION 8(a) OF
THE SECURITIES ACT OF 1933 OR UNTIL THE REGISTRATION STATEMENT SHALL BECOME
EFFECTIVE ON SUCH DATE AS THE COMMISSION, ACTING PURSUANT TO SAID SECTION 8(a),
MAY DETERMINE.

- --------------------------------------------------------------------------------
- --------------------------------------------------------------------------------
<PAGE>
THE INFORMATION IN THIS PROSPECTUS IS NOT COMPLETE AND MAY BE CHANGED. THE
SELLING SHAREHOLDERS MAY NOT SELL THEIR COMMON SHARES UNTIL
THE REGISTRATION STATEMENT FILED WITH THE SECURITIES AND EXCHANGE COMMISSION IS
EFFECTIVE. THIS PROSPECTUS IS NOT AN OFFER TO SELL COMMON
SHARES AND IT IS NOT SOLICITING AN OFFER TO BUY COMMON SHARES IN ANY STATE WHERE
THE OFFER OR SALE IS NOT PERMITTED.
<PAGE>
                                                           SELLING SHAREHOLDERS'
                                                                      PROSPECTUS

                              AVI BIOPHARMA, INC.

                            3,414,291 COMMON SHARES

                             NASDAQ NATIONAL MARKET
                                      AVII

    THIS INVESTMENT INVOLVES A HIGH DEGREE OF RISK. YOU SHOULD PURCHASE SHARES
ONLY IF YOU CAN AFFORD A COMPLETE LOSS OF YOUR INVESTMENT. SEE RISK FACTORS
BEGINNING ON PAGE 10.

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

    NEITHER THE SECURITIES AND EXCHANGE COMMISSION NOR ANY STATE SECURITIES
COMMISSION HAS APPROVED OR DISAPPROVED THE COMMON SHARES, OR DETERMINED IF THIS
PROSPECTUS IS TRUTHFUL OR COMPLETE. ANY REPRESENTATION TO THE CONTRARY IS A
CRIMINAL OFFENSE.

    - This is an offering of Common Shares by existing shareholders of AVI
      BioPharma, Inc.

    - The selling shareholders will receive all of the proceeds from the sale of
      the Common Shares, less any commissions or discounts paid to brokers or
      other agents. We will not receive any of the proceeds from the sale of the
      Common Shares.


    - The selling shareholders may offer and sell the Common Shares on the
      Nasdaq National Market at prevailing market prices, or in privately
      negotiated transactions at prices other than the market price. On
      February 28, 2000, the closing sale price for our Common Shares on the
      Nasdaq National Market was $25.00.


    - The Common Shares were obtained by the selling shareholders in
      transactions that were exempt from the registration requirements of the
      Securities Act of 1933, as amended, and represent approximately 21% of the
      Company's outstanding Common Stock.


                               February 29, 2000

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                               TABLE OF CONTENTS

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INCORPORATION OF CERTAIN DOCUMENTS BY REFERENCE.............      3

SUMMARY.....................................................      4

SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS...........      7

RISK FACTORS................................................      9

INFORMATION ABOUT THE COMPANY...............................     15

PRIVATE PLACEMENT TO SELLING SHAREHOLDERS...................     19

OUR SELLING SHAREHOLDERS....................................     20

PLAN OF DISTRIBUTION........................................     21

DESCRIPTION OF CAPITAL SHARES...............................     23

LEGAL MATTERS...............................................     25

EXPERTS.....................................................     25

ADDITIONAL INFORMATION......................................
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                                       2
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                INCORPORATION OF CERTAIN DOCUMENTS BY REFERENCE

    The following documents which we filed with the Securities and Exchange
Commission are incorporated by reference in this Prospectus:


    (1) our Annual Report on Form 10-K for the year ended December 31, 1999,
       which we refer to in the rest of this document as our Annual Report.



    In addition, all documents which we file with the Securities and Exchange
Commission ("Commission") pursuant to Section 13, 14 or 15(d) of the Securities
Exchange Act of 1934, as amended (the "Exchange Act"), after the date of the
Registration Statement and before termination of the offering of Common Shares,
including all annual reports on Form 10-K, and all filings on Forms 10-Q and
8-K, will be deemed to be incorporated by reference in this Prospectus and to be
a part of this Prospectus from the date those documents are filed. Any statement
contained in a document which is incorporated, or deemed to be incorporated, by
reference into this Prospectus, shall be considered modified or superseded for
purposes of this Prospectus to the extent that a statement contained in this
Prospectus or in any other subsequently filed document which also is, or is
deemed to be, incorporated by reference herein modifies or supersedes such
statement. Any such statement so modified or superseded shall not be deemed,
except as so modified or superseded, to constitute a part of this Prospectus.


    You may request a copy of any document incorporated by reference in this
Prospectus at no cost. To receive a copy, write or call us at
AVI BioPharma, Inc., One S.W. Columbia, Suite 1105, Portland, Oregon 97258,
Attention: Mr. Alan P. Timmins, (503) 227-0554.

    We are subject to the informational requirements of the Exchange Act and
file reports and other information with the Commission. Reports and other
information which we file with the Commission, including the Registration
Statement on Form S-3 of which this Prospectus is a part, may be inspected and
copied at the public reference facilities of the Commission at Judiciary Plaza,
450 Fifth Street, N.W., Room 1024, Washington, D.C. 20549, at prescribed rates.
The Commission's telephone number is 1-800-SEC-0330. These materials may be
obtained electronically by visiting the Commission's web site on the Internet at
http://www.sec.gw. Our Common Stock is listed on the Nasdaq National Market.
Reports, proxy statements and other Company materials also can be inspected at
1735 K Street, N.W., Washington, D.C. 20006-1506.

                                       3
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                                    SUMMARY

    MANY OF THE MATTERS SET FORTH IN THIS PROSPECTUS CONTAIN FORWARD-LOOKING
STATEMENTS THAT ARE SUBJECT TO RISKS AND UNCERTAINTIES THAT COULD CAUSE ACTUAL
RESULTS TO DIFFER MATERIALLY FROM THOSE SET FORTH HEREIN. WE REFER YOU TO
CAUTIONARY INFORMATION CONTAINED ELSEWHERE HEREIN AND IN OTHER DOCUMENTS WE FILE
WITH THE SECURITIES AND EXCHANGE COMMISSION FROM TIME TO TIME.

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BUSINESS..................................  AVI BioPharma, Inc. (AVI) is an emerging
                                            biopharmaceutical company developing therapeutic
                                            products using two distinct platform technologies:
</TABLE>

<TABLE>
                                             <S>                            <C>                 <C>
                                             Cancer Immunotherapy.........  Avicine             clinical
                                                                            Xactin              pre-clinical

                                             Gene-targeted drugs
                                               (NEUGENES).................  Resten-NG           IND filed
                                                                            Oncomyc-NG          pre-clinical
</TABLE>

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<S>                                         <C>
                                            Our principal focus is the treatment of life-threatening
                                            diseases, most notably cancer and heart disease.
                                            Currently approved drugs or other therapies often prove
                                            to be ineffective in treating advanced stages of these
                                            diseases or produce numerous unwanted side-effects. Our
                                            two leading platforms, Cancer Immunotherapy and
                                            NEUGENEs, are specifically aimed at solving the
                                            challenges faced by today's pharmaceutical products.
                                            Each of these products represents large market
                                            opportunities. It is estimated that the world-wide
                                            market for therapeutic cancer vaccines exceeds
                                            $2 billion.

CANCER IMMUNOTHERAPY (VACCINES)...........  Avicine, a therapeutic vaccine, represents our most
                                            advanced product opportunity, having completed a
                                            Phase II human clinical trial for colorectal cancer.
                                            Therapeutic cancer vaccines operate under the rationale
                                            that active immunization can stimulate an immune
                                            response that can be effective in fighting an existing
                                            cancer. The therapeutic benefit of the vaccine hinges on
                                            the existence of specific target sites, called tumor
                                            antigens, on cancer cells.

                                            The target for Avicine is human chorionic gonadotropin
                                            (hCG). Not only is hCG responsible for stimulating fetal
                                            development during pregnancy, but it is also a tumor
                                            antigen on cancer cells of all major types including
                                            cancer of the colon, pancreas, prostate, lung and
                                            breast. It is believed that the role of hCG in pregnancy
                                            and cancer is similar. In both cases, it (i) serves as a
                                            growth factor encouraging rapid cell division,
                                            (ii) fosters the formulation of blood vessels,
                                            (iii) stimulates invasion of other tissues, and
                                            (iv) dampens the immune system to allow the fetus, or
                                            the tumor, to avoid rejection. Avicine is based on an
                                            anti-hCG approach to treating cancer.

                                            Avicine has completed five clinical studies in cancer,
                                            in which a total of 172 patients received treatment.
                                            From these studies, we believe that the vaccine is a
                                            safe and essentially non-toxic therapy and capable of
                                            producing a specific immune response in most patients.
                                            Further, the patients who mounted an immune
</TABLE>

                                       4
<PAGE>

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                                            response to hCG lived longer than patients treated with
                                            other conventional therapies. We intend to investigate
                                            further the use of Avicine alone or in conjunction with
                                            other approved therapies in Phase II and Phase III
                                            licensing trials.

CANCER IMMUNOTHERAPY
  (XACTIN MONOCLONAL ANTIBODIES)..........  We are also combating cancer by utilizing antibodies
                                            that have activity against cancer cells that display the
                                            hCG hormone marker. We licensed XenoMouse-TM- technology
                                            from Abgenix Inc. and have produced human monoclonal
                                            antibodies against critical hCG tumor antigen targets.
                                            These high affinity, stable clones recognize the key
                                            epitopes in our cancer vaccine. The Xactin antibodies
                                            are both companion products to Avicine and independent
                                            cancer therapeutics and are now in pre-clinical
                                            development.

GENE-TARGETED DRUGS (NEUGENES)............  We have developed third generation gene-inactivating
                                            compounds that we believe are more stable, specific,
                                            efficacious, and cost effective than other antisense or
                                            ribozyme agents. Our NEUGENE compounds are distinguished
                                            by a novel backbone which replaces the natural or
                                            modified backbones of competing antisense or ribozyme
                                            technologies.

                                            NEUGENE use synthetic polymers to block the function of
                                            certain genetic sequences involved in the disease
                                            process. Targeting specific genetic sequences provides
                                            for greater selectivity than available through
                                            conventional drugs. NEUGENEs have the potential to
                                            provide safe and effective treatment for a wide range of
                                            human diseases.

                                            We have completed pre-clinical studies using our NEUGENE
                                            compounds in the treatment of bone cancer and
                                            restenosis, the blockage of arteries following balloon
                                            angioplasty. We recently filed an IND with the FDA for
                                            Resten-NG for restenosis and expect to begin a
                                            Phase I/II clinical trial by year-end.

STRATEGY..................................  We have the experience and resources to initiate drug
                                            discovery and development, and move drug candidates
                                            through pre-clinical development and into early stage
                                            clinical trials (Phase I and Phase II). Our strategy
                                            for the near-term (2 to 5 years) is to license the
                                            marketing rights for our product candidates to phar-
                                            maceutical partners after Phase II clinical trials or
                                            co-develop product candidates with strategic partners.
                                            In this manner, expensive, late-stage clinical
                                            development and marketing will be the responsibility of
                                            the licensee. With adequate resources we may consider
                                            assuming greater responsibility for the late-stage
                                            clinical development and marketing opportunities of
                                            future product candidates.
</TABLE>

                                       5
<PAGE>
CLINICAL DEVELOPMENT PROGRAM


<TABLE>
<CAPTION>
PRODUCT CANDIDATE                                PRE-CLINICAL   PHASE I    PHASE II    PHASE III
- -----------------                                ------------  ---------  -----------  ---------
<S>                                              <C>           <C>        <C>          <C>
Avicine
  (Colorectal Cancer Vaccine)..................  Completed     Completed  Completed    2000
Avicine
  (Pancreatic Cancer Vaccine)..................  Completed     Completed  In progress
Avicine
  (Prostate Cancer Vaccine)....................  Completed     Completed  2000
Resten-NG
  (Gene-Targeted Drug for Restenosis)..........  Completed     1999       2000
Oncomyc-NG
  (Gene-Targeted Drug for Cancer)..............  Completed     2000
Xactin
  (Human Monoclonal Antibody)..................  In progress   2000
NeuBiotics
  (Gene-Targeted Antibiotics)..................  In progress   2000-1
</TABLE>


                                       6
<PAGE>
               SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

    This Prospectus contains forward-looking statements regarding our plans,
expectations, estimates and beliefs. Our actual results could differ materially
from those discussed in, or implied by, these forward-looking statements.
Forward-looking statements are identified by words such as "believe,"
"anticipate," "expect," "intend," "plan," "will," "may," and other similar
expressions. In addition, any statements that refer to expectations, projections
or other characterizations of future events or circumstances are forward-
looking statements. We have based these forward-looking statements largely on
our expectations. Forward-looking statements in this Prospectus include, but are
not necessarily limited to, those relating to:

    - our intention to introduce new products

    - FDA or other regulatrory approval for our products

    - our expectations about the markets for our products

    - acceptance of our products in the marketplace

    - our future capital needs

    - success of our patent applications

    - the status of Year 2000 compliance efforts

    Forward-looking statements are subject to risks and uncertainties, certain
of which are beyond our control. Actual results could differ materially from
those anticipated as a result of the factors described in the "Risk Factors,"
including among others:

    - delays in obtaining, or our inability to obtain, approval by the FDA or
      other regulatory authorities for our products

    - delays in developing, or the failure to develop, our products

    - the development of competing or more effective products by other parties

    - uncertainty of market acceptance of our products

    - problems that we may face in manufacturing, marketing, and distributing
      our products

    - our inability to raise additional capital when needed

    - delays in the issuance of, or the failure to obtain, patents for certain
      on our products and technologies

    - problems with important suppliers and business partners

    We do not undertake any obligation to update or revise any forward-looking
statements contained in this Prospectus or incorporated by reference, whether as
a result of new information, future events or otherwise. Because of these risks
and uncertainties, the forward-looking events and circumstances discussed in
this Prospectus might not transpire. Factors that cause actual results or
conditions to differ from those anticipated by these and other froward-looking
statements include those more fully described in the "Risk Factors" section and
elsewhere in this Prospectus.

                                       7
<PAGE>
                      NOTES TO READERS OF THIS PROSPECTUS

    We were incorporated in Oregon in 1980. When we refer to "us," "we," "our,"
"the Company" and "AVI" in this Prospectus, we mean AVI BioPharma, Inc., and its
consolidated subsidiaries. Our executive offices are located at One S.W.
Columbia, Suite 1105, Portland, Oregon 97258. Our telephone number at that
location is (503) 227-0554. Information contained on our websites does not
constitute part of this Prospectus.

    We are subject to the informational requirements of the Exchange Act and
file reports and other information with the Commission. Reports and other
information which we file with the Commission, may be inspected and copied at
the public reference facilities of the Commission at Judiciary Plaza, 450 Fifth
Street, N.W., Room 1024, Washington, D.C. 20549, at prescribed rates. The
Commission's telephone number is 1-800-SEC-0330. These materials may be obtained
electronically by visiting the Commission's website on the Internet at
http://www.sec.gov. Reports, proxy statements and other Company materials also
can be inspected at 1735 K Street, N.W., Washington, D.C. 20006-1506 or obtained
directly from the Company at the address and telephone listed above.

    This Prospectus includes our trademarks and registered trademarks, including
Avicine-TM-, NEUGENE-Registered Trademark-and Xactin-TM-. Each other trademark,
trade name or service mark appearing in this Prospectus belongs to its holder.

                                       8
<PAGE>
                                  RISK FACTORS

    The Shares offered by this Prospectus are speculative and involve a high
degree of risk. Before making an investment, you should carefully read this
entire Prospectus and consider the following risk factors.

RISKS RELATING TO OUR BUSINESS

HISTORY OF OPERATING LOSSES AND ANTICIPATED FUTURE LOSSES


    We incurred a net operating loss of $8.5 million in 1999. "Net operating
loss" represents the amount by which our expenses (other than interest expense)
exceed revenues. As of December 31, 1999, our accumulated deficit was
$51.1 million. Our losses have resulted principally from expenses incurred in
research and development of our technology and products and from selling,
general and administrative expenses that we have incurred while building our
business infrastructure. We expect to continue to incur significant operating
losses in the future as we continue our research and development efforts and
seek to obtain regulatory approval of our products. Our ability to achieve
profitability depends on our ability to complete development of our products,
obtain regulatory approvals and market our products. It is uncertain when, if
ever, we will become profitable.


EARLY STAGE OF PRODUCT DEVELOPMENT

    Although we began operations in 1980, except for Avicine, we are only in the
early stages of the development of our pharmaceutical products. We have devoted
almost all of our time to research and development of our technology and
products, protecting our proprietary rights and establishing strategic
alliances. Our proposed products are in the pre-clinical or clinical stages of
development and will require significant further research, development, clinical
testing and regulatory clearances. We have no products available for sale,
except for research reagents, and we do not expect to have any products
available for sale for several years. Our proposed products are subject to
development risks. These risks include the possibilities that any of the
products could be found to be ineffective or toxic, or could fail to receive
necessary regulatory clearances. Although we have obtained favorable results in
Phase II using Avicine to treat colorectal cancer patients, we cannot assure
that we will obtain similar results in the contemplated Phase III protocol. We
have not received any significant revenues from the sale of products and we
cannot assure investors that we will successfully develop marketable products,
that our sales will increase or that we will become profitable. Third parties
may develop superior or equivalent, but less expensive, products.

LACK OF OPERATING EXPERIENCE

    We have engaged solely in the development of pharmaceutical technology.
Although some of our management have experience in biotechnology company
operations, we have limited experience in manufacturing or selling
pharmaceutical products. We also have only limited experience in negotiating and
maintaining strategic relationships, and in conducting clinical trials and other
later-stage phases of the regulatory approval process. We cannot assure
investors that we will successfully engage in any of these activities.

NEED FOR FUTURE CAPITAL AND UNCERTAINTY OF ADDITIONAL FUNDING

    Since we began operations, we have obtained operating funds primarily by
selling shares of our company. Based on our current plans, we believe that
current cash balances including the anticipated proceeds from this Offering will
be sufficient to meet our operating needs for approximately the next eighteen
months. Furthermore, the actual amount of funds that we will need will be
determined by many factors, some of which are beyond our control. These factors
include the success of our research and development efforts, the status of our
pre-clinical and clinical testing, costs relating to securing regulatory
approvals and the costs and timing of obtaining new patent rights, regulatory
changes, competition and technological developments in the market. We may need
funds sooner than currently anticipated.

                                       9
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    We anticipate that we will need to obtain additional funds during or at the
end of this eighteen-month period. If necessary, potential sources of additional
funding include strategic relationships, public or private sales of shares of
our common stock or debt or other arrangements. We do not have any committed
sources of additional financing at this time. It is uncertain whether we can
obtain additional funding when we need it on terms that will be acceptable to us
or at all. If we raise funds by selling additional shares of our common stock or
securities convertible into our common stock, the ownership interest of our
existing shareholders will be diluted. If we are unable to obtain financing when
needed, our business and future prospects would be materially adversely
affected.

DEPENDENCE ON OTHERS FOR CLINICAL TESTING, MANUFACTURING AND MARKETING

    We do not intend to conduct late-stage (Phase III) human clinical trials
ourselves. We anticipate entering into relationships with larger pharmaceutical
companies to conduct later pharmaceutical trials and to market our products and
we also plan to continue to use contract manufacturing for our products. We may
be unable to enter into corporate partnerships that could impede our ability to
bring our products to market. We cannot assure investors that any corporate
partnerships, if entered, will be on favorable terms or will result in the
successful development or marketing of our products. If we are unsuccessful in
establishing advantageous clinical testing, manufacturing and marketing
relationships, we are not likely to generate significant revenues and become
profitable.

LIMITED MANUFACTURING CAPABILITY

    While we believe that we can produce materials for clinical trials at our
existing facilities, we will need to expand our commercial manufacturing
capabilities for products in the future if we elect not to or cannot contract
with others to manufacture our products. This expansion may occur in stages,
each of which would require regulatory approval, and product demand could at
times exceed supply capacity. We have not selected a site for any expanded
facilities and cannot predict the amount we will expend for construction of such
facilities. We cannot assure if or when the FDA will determine that such
facilities comply with Good Manufacturing Practices. The projected location and
construction of any facilities will depend on regulatory approvals, product
development, pharmaceutical partners and capital resources, among other factors.
We have not obtained regulatory approvals for any productions facilities for our
products, nor can we assure investors that we will be able to do so.

GOVERNMENTAL REGULATION; LACK OF ASSURANCE OF REGULATORY APPROVALS

    All of our products are subject to extensive regulation by the United States
Food and Drug Administration and by comparable agencies in other countries. The
FDA and comparable agencies require new pharmaceutical products to undergo
lengthy and detailed clinical testing procedures and other costly and
time-consuming compliance procedures. Except for Avicine, none of our products
have been tested in humans.   We cannot predict when we will initiate and
complete our clinical trials or when we will be able to submit our products for
regulatory review. Even if we submit a new drug application, there may be delays
in obtaining regulatory approvals, if we obtain them at all. Sales of our
products outside the United States will also be subject to regulatory
requirements governing clinical trials and product approval. These requirements
vary from country to country and could delay introduction of our products in
those countries. We cannot assure you that any of our products will receive
marketing approval from the FDA or comparable foreign agencies.

DEPENDENCE ON KEY PERSONNEL

    Our success will depend to a large extent on the abilities and continued
service of several key employees, including Drs. Denis Burger, Patrick Iversen,
and Dwight Weller. The loss of any of these key employees could significantly
delay the achievement of our goals. Competition for qualified personnel in

                                       10
<PAGE>
our industry is intense, and our success will be dependent on our ability to
attract and retain highly skilled personnel.

COMPETITION

    The biotechnology industry is highly competitive. We compete with companies
in the United States and abroad that are engaged in the development of
pharmaceutical technologies and products. They include:

    - biotechnology, pharmaceutical, chemical and other companies;

    - academic and scientific institutions;

    - governmental agencies; and

    - public and private research organizations.

    Many of these companies and many of our other competitors have much greater
financial and technical resources and production and marketing capabilities than
we do. Our industry is characterized by extensive research and development and
rapid technological progress. Competitors may successfully develop and market
superior or less expensive products which render our products less valuable or
unmarketable.

PATENTS AND PROPRIETARY RIGHTS

    Our success will depend on our existing patents and licenses, and our
ability to obtain additional patents in the future. We have filed 46 patent
applications in the United States, Canada, Europe, Australia and Japan and 43
patents have been issued. We license the composition, manufacturing and use of
Avicine in all fields except fertility regulation from The Ohio State
University.

    We cannot assure investors that our pending patent applications will result
in patents being issued in the United States or foreign countries. In addition,
we cannot guarantee that patents which have been or will be issued will afford
meaningful protection for our technology and products. Competitors may develop
products similar to ours which do not conflict with our patents. Others may
challenge our patents and, as a result, our patents could be narrowed or
invalidated. The patent position of biotechnology firms generally is highly
uncertain, involves complex legal and factual questions, and has recently been
the subject of much litigation. No consistent policy has emerged from the United
States Patent and Trademark Office or the courts regarding the breadth of claims
allowed or the degree of protection afforded under biotechnology patents. In
addition, there is a substantial backlog of biotechnology patent applications at
the USPTOs and the approval or rejection of patents may take several years.

    Our success will also depend partly on our ability to operate without
infringing upon the proprietary rights of others, as well as our ability to
prevent others from infringing on our proprietary rights. We may be required at
times to take legal action in order to protect our proprietary rights and,
despite our best efforts, we may be sued for infringing on the patent rights of
others. Patent litigation is costly and, even if we prevail, the cost of such
litigation could adversely affect our financial condition. If we do not prevail,
in addition to any damages we might have to pay, we could be required to stop
the infringing activity or obtain a license. We cannot be certain that any
required license would be available to us on acceptable terms, or at all. If we
fail to obtain a license, our business might be materially adversely affected.

    To help protect our proprietary rights in unpatented trade secrets, we
require our employees, consultants and advisors to execute confidentiality
agreements. However, we cannot guarantee that these agreements will provide us
with adequate protection if confidential information is used or disclosed
improperly. In addition, in some situations, these agreements may conflict with,
or be subject to, the rights of third parties with whom our employees,
consultants or advisors have prior employment or consulting

                                       11
<PAGE>
relationships. Further, others may independently develop substantially
equivalent proprietary information and techniques, or otherwise gain access to
our trade secrets.

POTENTIAL PRODUCT LIABILITY

    The use of our products will expose us to the risk of product liability
claims. Although we intend to obtain product liability insurance coverage, we
cannot guaranty that product liability insurance will continue to be available
to us on acceptable terms or that our coverage will be sufficient to cover all
claims against us. A product liability claim, even one without merit or for
which we have substantial coverage, could result in significant legal defense
costs, thereby increasing our expenses, lowering our earnings and, depending on
revenues, potentially result in additional losses.

UNCERTAINTY OF THIRD-PARTY REIMBURSEMENT

    In addition to obtaining regulatory approval, the successful
commercialization of our products will depend on our ability to obtain
reimbursement for the cost of the product and treatment. Government authorities,
private health insurers and other organizations, such as health maintenance
organizations are increasingly challenging the prices charged for medical
products and services. Also, the trend toward managed health care in the United
States, the growth of healthcare organizations such as HMOs, and legislative
proposals to reform healthcare and government insurance programs could
significantly influence the purchase of healthcare services and products,
resulting in lower prices and reducing demand for our products. The cost
containment measures that healthcare providers are instituting and any
healthcare reform could affect our ability to sell our products and may have a
material adverse effect on our operations. We cannot assure investors that
reimbursement in the United States or foreign countries will be available for
any of our products, that any reimbursement granted will be maintained, or that
limits on reimbursement available from third-party payors will not reduce the
demand for, or the price of, our products. The lack or inadequacy of third-party
reimbursements for our products would have a material adverse affect on our
operations. We cannot forecast what additional legislation or regulation
relating to the healthcare industry or third-party coverage and reimbursement
may be enacted in the future, or what effect the legislation or regulation would
have on our business.

RISKS RELATED TO SHARE OWNERSHIP

OUR PREFERRED SHARES, CLASSIFIED BOARD OF DIRECTORS AND OREGON LAWS COULD
  PROHIBIT TAKEOVERS

    Our authorized capital consists of 50,000,000 shares of common stock and
2,000,000 preferred shares. The Board of Directors, without any further vote by
the shareholders, has the authority to issue preferred shares and to determine
the price, preferences, rights and restrictions, including voting and dividend
rights, of these shares. The rights of the holders of shares of common stock may
be affected by the rights of holders of any preferred shares that the Board of
Directors may issue in the future. For example, the Board of Directors may allow
the issuance of preferred shares with more voting rights, higher dividend
payments or more favorable rights upon dissolution, than the shares of common
stock. If preferred shares are issued in the future, it may also be more
difficult for others to acquire a majority of our outstanding voting shares. See
"Description on Capital Shares."

    In addition, we have a "classified" Board of Directors, which means that
only one-half of our directors are eligible for election each year. Therefore,
if shareholders wish to change the composition of the Board of Directors, it
could take at least two years to remove a majority of the existing directors or
to change all directors. Having a classified Board of Directors may, in some
circumstances, deter or delay mergers, tender offers or other possible
transactions which may be favored by some or a majority of our shareholders.

                                       12
<PAGE>
    The Oregon Control Share Act and Business Combination Act limit parties who
acquire a significant amount of voting shares from exercising control over us.
The Act may lengthen the period for a proxy contest or for a person to vote
their shares to elect the majority of our Board.

VOLATILITY OF STOCK PRICE

    Historically, the market price of our stock has been highly volatile. The
following types of announcements could have a significant impact on the price of
our common stock:

    - positive or negative results of testing and clinical trials

    - delays in entering into corporate partnerships

    - technological innovations or commercial product introductions by ourselves
      or competitors

    - changes in government regulations

    - developments concerning proprietary rights, including patents and
      litigation matters

    - public concern relating to the commercial value or safety of any of our
      products

    - general stock market conditions

    Further, the stock market has in recent months experienced and may continue
to experience significant price and volume fluctuations. These fluctuations have
particularly affected the market prices of equity securities of many
biopharmaceutical companies that are not yet profitable. Often, the effect on
the price of such securities is unrelated or disproportionate to the operating
performance of such companies. These broad market fluctuations may adversely
affect the ability of a shareholder to dispose of his shares at a price equal to
or above the price at which the shares were purchased.

FUTURE SALE OF ELIGIBLE SHARES MAY LOWER THE PRICE OF OUR COMMON STOCK


    We have outstanding 16,236,428 shares of common stock and all such shares
are eligible for sale under Rule 144 or are otherwise freely tradeable. In
addition:



    - Our employees and others hold options to buy a total of 2,195,367 shares
      of common stock. The shares of common stock to be issued upon exercise of
      these options, have been registered, and therefore may be freely sold when
      issued;



    - There are outstanding warrants to buy 5,527,254 shares of common stock.
      The shares issuable upon exercise of 4,416,814 warrants are registered.
      These shares may be freely sold when issued. The holders of warrants
      covering 400,000 shares have incidental registration rights to have the
      shares issuable upon the exercise of their warrants registered. Once
      registered, those shares may be freely sold when issued, for so long as
      the registration statement is effective and current. The remaining
      warrants have no registration rights.



    - We may issue options to purchase up to an additional 118,826 shares of
      common stock under our stock option plans, which also will be fully
      saleable when issued.


    Sales of substantial amounts of shares into the public market could lower
the market price of our common stock.

RIGHTS OF CERTAIN HOLDERS TO ADDITIONAL STOCK OR REDEMPTION OF SHARES

    Holders of 1,857,147 shares of our common stock enjoy the right to receive
additional shares of common stock from the Company without additional payment to
the Company if the Company sells shares of common stock, or engages in similar
financing transactions, at a price of less than $3.50 per share prior to
December 16, 2002, or 33 months have passed since the effective date of the
registration statement

                                       13
<PAGE>
relating to this Prospectus. If additional shares of our common stock are issued
under this obligation, the ownership interest of other existing shareholders
will be diluted.

    Under certain circumstances, the Company may be required to redeem shares to
be issued to the holders who enjoy this right. Specifically, if the holdings of
the Company's stock by any holder who enjoys this right will exceed their pro
rata share of 20 percent of the Company's outstanding common stock due to the
issuance of new shares, the Company must redeem the new shares to be issued at a
price equal to 110 percent of the price originally paid for these shares. This
redemption obligation could materially adversely affect the business and future
prospects of the Company if it arises.

ABSENCE OF DIVIDENDS

    We have never paid dividends on our shares of common stock and do not intend
to pay dividends in the foreseeable future.

YEAR 2000 RISKS

    Many currently installed operating systems and software products are coded
only to accept two digit entries in the date code field. Consequently, they are
unable to distinguish 21st century dates from 20th century dates. As a result,
the computer systems and software used by many companies may need to be upgraded
to prevent problems that would result from misreading the entries in the date
code field. Failure to correct systems to become "Year 2000 compliant" may
result in systems failures or miscalculations causing disruptions of operations,
including, among other things, a temporary inability to process data, send
invoices or engage in similar normal business activities.

    We are currently reviewing the potential impact of Year 2000 issues on our
business and attempting to mitigate or eliminate those issues. The primary risks
to us are those of business continuity. We are determining which equipment we
own needs to be replaced. We have also begun communicating with our significant
suppliers, financial institutions, insurance companies and other parties that
provide us significant services, including clinical trial sites, to determine
whether they anticipate Year 2000 problems in their operations. If we or our
significant vendors or suppliers are unable to become Year 2000 compliant in
time, this could have a material adverse affect on our ability to continue our
operations.

                                       14
<PAGE>
                         INFORMATION ABOUT THE COMPANY

    FOR A DETAILED DESCRIPTION OF OUR BUSINESS AND INFORMATION ABOUT OUR
MANAGEMENT, SEE OUR ANNUAL REPORT WHICH IS INCORPORATED INTO THIS PROSPECTUS BY
REFERENCE. THE FOLLOWING INFORMATION SUPPLEMENTS OR SUPERSEDES, AS MAY BE
APPROPRIATE, THE INFORMATION CONTAINED IN OUR ANNUAL REPORT:

PRODUCT DEVELOPMENT OVERVIEW

I.  CANCER IMMUNOTHERAPY

A.  AVICINE THERAPEUTIC CANCER VACCINE

TECHNICAL OVERVIEW

    The therapeutic vaccine approach is among the newer strategies being
investigated for treating cancer. Historically, vaccines were developed and used
to induce an immune response in order to prevent a disease. This is contrasted
with a therapeutic vaccine where the disease entity is known or suspected to be
present at the time of vaccination. The rationale employed with a therapeutic
approach is that active immunization against a specific pathogenic agent can
stimulate an immune response against the existing disease.

    In order for a therapeutic vaccine to be effective in fighting a disease
such as cancer, it is necessary to identify specific target sites on the tumor
cells, called tumor-associated antigens. The more selective that the antigen is
to the tumor, the greater likelihood of attacking only the cancer cells. The
identification of an appropriate target has been one of the greatest challenges
in the development of a useful cancer vaccine.

    AVI BioPharma's therapeutic cancer vaccine, Avicine, is designed to produce
an immune response against a well-characterized target, human chorionic
gonadotropin (hCG). hCG is a hormone produced during pregnancy that plays a
variety of roles in fostering the development of a fetus. Through extensive
research, scientists found that hCG is also present in most cancers. In fact,
cancer is believed to be the only significant exception to the normal hCG
function during pregnancy. Given the selective production of hCG, we believe it
represents a highly specific target for a therapeutic cancer vaccine.

    The use of hCG as a cancer vaccine target may offer advantages over other
potential tumor associated antigens.

    - It is not usually found on normal cells with the exception of those
      present during a pregnancy. This means that it is highly selective.

    - It is widely expressed by and found on many types of cancer, including
      colon, pancreas, prostate, lung and breast.

    - hCG expression has been correlated with tumor aggressiveness. In other
      words, the higher the level of hCG, the more aggressive the rate of growth
      or spread of the cancer.

    - Antibodies to hCG are believed to block the same hormonal functions that
      hCG plays in pregnancy and cancer, including rapid cell division, the
      formulation of blood vessels, invasion of other tissues, and dampening of
      the immune responses.

    Since hCG is a natural human protein, people will not mount an immune
response to it unless they are actively immunized. Once immunized, the mechanism
of action of an anti-hCG vaccine can be viewed as a two-pronged attack. First,
it directs an immune response against the tumor, and second, it neutralizes the
hormonal benefits provided by hCG.

    The hCG component in Avicine is a small peptide from this hormone. The
peptide is joined to a carrier, diphtheria toxoid, to enhance the immune
response. Diphtheria toxoid was selected since most of the world's population
has been vaccinated against it and there is significant experience with it as a
vaccine

                                       15
<PAGE>
component in man. The combination provides for an existing immune response to
the carrier which is believed to be important in stimulating an immune response
to the hCG peptide.

                     AVICINE DISTINGUISHING CHARACTERISTICS

    - Fully-characterized synthetic vaccine

    - Capable of being produced inexpensively in large quantities

    - Targets a widely-expressed tumor antigen (hCG)

    - Ready for Phase III clinical testing in colorectal patients

    - Applicable to most cancer types in multiple clinical settings

    - Twenty years of research and development and safety data

AVICINE CLINICAL TRIALS

    We have completed three Phase I clinical trials using Avicine in 87 patients
with cancer. Overall, these studies showed Avicine to be safe and essentially
non-toxic. These early clinical trials showed the vaccine to be effective in
stimulating an immune response to hCG in most patients. Moreover, apparent
survival benefits and some tumor regressions were noted.

                     PANCREATIC AND PROSTATE CANCER TRIALS

    We recently completed a pilot Phase II study using Avicine in 10 patients
with advanced pancreatic cancer. For the 10 patients treated, the median
survival was approximately 33 weeks. Patients with advanced pancreatic cancer
are currently treated with chemotherapy and have a median survival of
approximately 18 to 25 weeks. Although we believe these results to be
encouraging, we hesitate to draw conclusions from such a small study other than
to use these results to design additional trials.


    Two additional Phase II trials were scheduled for the fourth quarter of
1999. The first Phase II study of 50 patients with pancreatic cancer was
initiated in October 1999. In addition, we plan to initiate a Phase II clinical
trial in 24 patients with prostate cancer in 2000.


                            COLORECTAL CANCER TRIALS

    A multicenter Phase II study of Avicine was conducted on in 77 patients with
advanced colorectal cancer. The objectives of this trial were to determine
whether administration of Avicine would induce an immune response in patients
with metastatic colorectal cancer and to measure safety and efficacy in these
patients. Overall, 51 of the 77 patients responded to our vaccine by producing
antibodies to hCG. The patients that were antibody responders had a median
survival of 42 weeks. Patients that did not respond immunologically had a median
survival of just 17 weeks.

    Further analysis of the multicenter Phase II data showed that patients who
produced antibodies to two targets on the hCG peptide had a median survival of
66 weeks. Camptosar-Registered Trademark-, the current standard of care for
treating advanced colorectal cancer patients, produces a median survival of
37-40 weeks. Through additional research efforts, we believe we have learned how
to stimulate production of antibodies to the two hCG targets in most patients.

    Overall, these clinical data suggest that the patients that received Avicine
and responded by making hCG antibodies had improved median survival compared to
patients treated with chemotherapeutic drugs. Avicine was found to be safe and
did not exhibit the toxicity associated with cytotoxic drug treatment. Based on
these data, we plan to initiate a Phase III pivotal trial in 500 patients with
metastatic colorectal cancer in 2000. This trial randomizes patients receiving
first-line therapy for metastatic colorectal cancer to

                                       16
<PAGE>
one of two treatment arms: combination chemotherapy or combination chemotherapy
plus Avicine. The end points in the trial are time to disease progression and
median survival.

AVICINE CLINICAL TRIALS


<TABLE>
<CAPTION>
TRIAL                   DESCRIPTION & TYPE                                PATIENTS      STATUS
- -----                   ------------------                               ----------   -----------
<C>                     <S>                                              <C>          <C>
          1             Phase I safety study...........................  43 treated   Completed
          2             Phase I metastatic cancer......................  21 treated   Completed
          3             Phase Ib metastatic cancer.....................  23 treated   Completed
          4             Phase II pancreatic and extension..............  10 treated   Completed
          5             Phase II colorectal............................  77 treated   Completed
          6             Phase II pancreatic............................  50           In progress
          7             Phase II prostate..............................  24           2000
          8             Phase III colorectal licensing trial...........  500          2000
</TABLE>


B.  XACTIN--HUMAN MONOCLONAL ANTIBODY FOR CANCER

    We are also combating cancer by administering antibodies that have activity
against cancer cells that display the hCG hormone marker. We licensed XenoMouse
technology from Abgenix Inc. and have produced human monoclonal antibodies
against critical hCG tumor antigen targets. These high affinity, stable clones
recognize the key epitopes in our cancer vaccine. The Xactin antibodies are both
companion products to Avicine and independent cancer therapeutics and are now in
pre-clinical development.

II. GENE-TARGETED DRUGS--NEUGENE TECHNOLOGY

TECHNICAL OVERVIEW

    Most human diseases arise from the function or dysfunction of genes within
the body, either those of pathogens, such as viruses, or of one's own genes. New
techniques in molecular biology have led to the identification of the genes
associated with most of the major human diseases and to the determination of the
sequence of their genetic codes. Using modern methods of chemical synthesis,
compounds can be prepared that recognize target gene sequences in a pathogen or
pathogenic process. When these compounds bind tightly to the disease-causing
sequence, the genetic process is inhibited, and thus the pathogen or pathogenic
process is disabled. This is called ANTISENSE technology since the SENSE of the
genetic code is blocked.

    Limitations of then-existing antisense technology in the late 1980s led us
to pursue a different approach than many of our competitors. This effort
culminated in our development of a class of third-generation agents, known as
NEUGENE compounds. In pre-clinical studies, our patented compounds display
advantageous pharmaceutical properties over second-generation compounds now in
clinical trials by others. Such improvements include stability, specificity,
potency, low toxicity and effectiveness.

NEAR-TERM PRODUCT DEVELOPMENT--CANCER AND RESTENOSIS


    The first application of our antisense technology is designed to treat
diseases involving abnormal cell division, such as cancer, certain
cardiovascular and inflammatory diseases, psoriasis, polycystic kidney disease
and chronic graft rejection. The NEUGENE target for these diseases is the gene
component named c-myc. We have finished the pre-clinical development of two
NEUGENE compounds, Resten-NG and Oncomyc-NG, and have filed an IND and we
initiated a Phase I clinical trial in 1999 for restenosis and cancer.


                                       17
<PAGE>
    The table below page summarizes our broader development program for NEUGENE:

NEUGENE ANTISENSE DEVELOPMENT PROGRAM

<TABLE>
<CAPTION>
ANTISENSE TARGET                                CLINICAL INDICATION
- ----------------                 -------------------------------------------------
<S>                              <C>
                                 Cancer, restenosis, psoriasis, chronic graft
C-myc..........................  rejection
Telomerase.....................  Cancer
BCL2...........................  Cancer
TNF alpha......................  Arthritis, septic shock, asthma
NF kappa B.....................  Crohn's Disease, chronic inflammation
ICAM-1.........................  Arthritis, chronic graft rejection
Hepatitis C virus..............  Hepatitis
</TABLE>

                                       18
<PAGE>
                   PRIVATE PLACEMENT TO SELLING SHAREHOLDERS

    On December 17, 1999, certain of the Selling Shareholders bought 1,857,147
Shares and warrants to purchase an additional 557,144 Shares.

    The purchase agreements and warrants contain protective provisions for the
Selling Shareholders if we sell any other Shares (with limited exceptions) at a
lower price than what the Selling Shareholders paid. The period during which
this provision is in effect runs until either 36 months from the closing date of
the purchase transaction or 33 months from the effective date of this
registration statement, whichever occurs later.

    Under these protective provisions, the Selling Shareholders receive
additional shares and warrants to acquire additional Shares and a reduced strike
price for all Shares acquired with the warrants if we sell Shares for less than
the $3.50 price paid by Selling Shareholders.

    The number of additional Shares received by a Selling Shareholder is
calculated by the following steps:

    - aggregate purchase price by the Selling Shareholder for all Shares
      purchased under the purchase agreement is divided by the new lower per
      Share sales price causing the adjustment;

    - from this new number of shares is subtracted the number of Shares already
      delivered to the Selling Shareholder; and

    - the difference is the number of additional Shares we will issue to the
      Selling Shareholder.

    The purchase agreements also contain the provision that if the Selling
Shareholder owns at least 250,000 of the Shares bought pursuant to the purchase
agreement, it receives the adjustment based on all the Shares it originally
bought. However, if the Selling Shareholder owns less than 250,000 of the
originally purchased Shares, it only receives an adjustment based on the number
of Shares it still owns.

    Similarly, the warrants provide for an adjustment, both of the exercise
price and number of Shares subject to the warrants.

    The Selling Shareholders received warrants to purchase three Shares for
every seven Shares of stock they purchased. The exercise price of the warrants
was set at 115% of the original per Share purchase price. That calculates to an
exercise price of $4.025, based on a $3.50 Share price.

    If Shares are sold for less than the exercise price (again with certain
exceptions), then

    - warrant price is reduced to 115% of the price of the newly sold Shares;
      and

    - the number of warrants is increased proportionately so that the Selling
      Shareholders will still receive warrants for three Shares for every
      10 Shares they either purchased or received because of the protective
      provision adjustment.

The following chart sets forth an example of how this might work for a
hypothetical Selling Shareholder:

<TABLE>
<S>                                                           <C>
Original aggregate Share purchase price.....................  $1,050,000
Original number of Shares purchased.........................     300,000
Original per Share price....................................  $     3.50
Newly sold Share price......................................  $     3.00

    Original aggregate Share purchase price
      divided by newly sold Share price
                             ($1,050,000  DIVIDED BY $3.00)
      = 350,000 Shares

Original number of Shares minus adjusted number equals new
  Shares we will issue......................................      50,000
</TABLE>

                                       19
<PAGE>
For the options:

<TABLE>
        <S>                                                           <C>
        New Share price times 115% ($3.00 x 1.15) is new strike
          price = $3.45

        Original number of Shares covered by warrant was three for
          ten shares
                                                            (3 X
          30,000) = 90,000

        The after adjustment number of Shares is 350,000 --
          three warrant Shares for ten Shares is                   3
          x 35,000 = 105,000

        That is, the Shares subject to the warrant now total 105,000
          with a strike price of $3.45
</TABLE>

    In addition to the Shares covered by this registration statement, we are
obligated to register any Shares issued pursuant to the adjustment described
above and any Shares issued following exercise of any new options granted
following an adjustment.

    However, the purchase agreements and warrants do contain the restriction
that we may not issue any new Shares or warrants if that would cause a Selling
Shareholder to beneficially own more than 9.90% of the total outstanding Shares
of our common stock. The adjustment must be delayed until it can be done without
exceeding the 9.90% limitation.

                            OUR SELLING SHAREHOLDERS


    The following table provides certain information with respect to the Shares
held by each Selling Shareholder as of February 29, 2000. Except as otherwise
noted, all of the Common Shares owned by each Selling Shareholder are registered
for sale pursuant to this Prospectus. The Selling Shareholders, however, are not
under any obligation to sell all of any portion of their Shares, nor are the
Selling Shareholders obligated to sell any of their Shares immediately under
this Prospectus. We will not receive any proceeds from any sales of Shares by
the Selling Shareholders.


<TABLE>
<CAPTION>
                                                                 NUMBER OF
                                                                  COMMON
                                                                  SHARES                       SHARES OWNED
                                                               BENEFICIALLY                  AFTER OFFERING(1)
                                                               OWNED BEFORE      SHARES     -------------------
SELLING SHAREHOLDER                                             OFFERING(1)      OFFERED     NUMBER    PERCENT
- -------------------                                           ---------------   ---------   --------   --------
<S>                                                           <C>               <C>         <C>        <C>
Castle Creek Healthcare Partners LLC........................       557,141(2)     557,141        --        --
Michael T. Jackson Trust,
  New Technologies Fund.....................................       185,718(3)     185,718        --        --
JALAA Equities LP...........................................       185,718(4)     185,718        --        --
The Tail Wind Fund, Ltd.....................................       928,572(5)     928,572
Resonance, Ltd..............................................       557,142(6)     557,142
SuperGen, Inc...............................................     1,000,000      1,000,000
                                                                 ---------      ---------   -------     -----
                                                                 3,414,291      3,414,291        --        --
</TABLE>

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


(1) Beneficial ownership is determined in accordance with the rules of the
    Securities and Exchange Commission and generally includes voting or
    investment power with respect to securities. Shares of Common Stock subject
    to options and warrants currently exercisable or convertible, or exercisable
    or convertible within 60 days of February 29, 2000, are deemed beneficially
    owned and outstanding for computing the percentage of the person holding
    such securities, but are no considered outstanding for computing the
    percentage of any other person.



(2) Includes 128,571 shares subject to warrants exercisable within 60 days of
    February 29, 2000.



(3) Includes 42,858 shares subject to warrants exercisable within 60 days of
    February 29, 2000.



(4) Includes 42,858 shares subject to warrants exercisable within 60 days of
    February 29, 2000.



(5) Includes 214,286 shares subject to warrants exercisable within 60 days of
    February 29, 2000.



(6) Includes 128,571 shares subject to warrants exercisable within 60 days of
    February 29, 2000.


                                       20
<PAGE>
                              PLAN OF DISTRIBUTION

    The selling stockholders may sell the common stock:

    - through one or more underwriters or dealers for public offering and sale,

    - directly to investors, or

    - through agents.

    The selling stockholders may distribute the common stock from time to time
in one or more transactions at a fixed price or prices, which may be changed
from time to time:

    - at market prices prevailing at the times of sale,

    - at prices related to those prevailing market prices, or

    - at negotiated prices.

    We will not receive any proceeds from the sale of the common stock.

    The distribution of the common stock may be effected in one or more of the
following methods:

    - ordinary brokers' transactions, which may include long or short sales,

    - transactions involving cross or block trades, or otherwise on the Nasdaq
      National Market,

    - purchases by brokers, dealers or underwriters as principal and resale by
      those purchasers for their own accounts pursuant to this prospectus,

    - "at the market" to or through market makers or into an existing market for
      the common stock,

    - in other ways not involving market makers or established trading markets,
      including direct sales to purchasers or sales effected through agents,

    - through transactions in options, swaps or other derivatives (whether
      exchange-listed or otherwise),

    - pursuant to Rule 144 under the Securities Act, or

    - any combination of the foregoing, or by any other legally available means.

    In addition, the selling stockholders or their successors in interest may
enter into hedging transactions with broker-dealers who may engage in short
sales of common stock in the course of hedging the positions they assume with
the selling stockholders. The selling stockholders or their successors in
interest may also enter into option or other transactions with broker-dealers
that require the delivery by those broker-dealers of the common stock, which
common stock may be resold thereafter pursuant to this prospectus. In connection
with any sales, the selling stockholders and any brokers or dealers
participating in such sales may be deemed to be underwriters within the meaning
of the Securities Act.

    Any broker-dealer participating in such transactions as agent may receive
commissions from the Selling stockholders and/or purchasers of the shares
offered hereby (and, if it acts as agent for the purchaser of those shares, from
that purchaser). Usual and customary brokerage fees will be paid by the selling
stockholders. Broker-dealers may agree with the selling stockholders to sell a
specified number of shares at a stipulated price per share, and, to the extent
the broker-dealer is unable to do so acting as agent for a selling stockholders,
to purchase as principal any unsold shares at the price required to fulfill the
broker-dealer commitment to the selling stockholders. Broker-dealers who acquire
shares as principal may thereafter resell the shares from time to time in
transactions (which may involve cross and block transactions and which may
involve sales to and through other broker-dealers, including transactions of the
nature described above) in the over-the-counter market, in negotiated
transactions or otherwise at market

                                       21
<PAGE>
prices prevailing at the time of sale or at negotiated prices, and in connection
with the resales may pay to or receive from the purchasers of those shares
commissions computed as described above.

    We have advised the selling stockholders that Regulation M promulgated under
the Securities Exchange Act, may apply to their sales in the market, have
furnished the selling stockholders with a copy of this regulation and have
informed the selling stockholders of the need for delivery of copies of this
prospectus. The selling stockholders may indemnify any broker-dealer that
participates in transactions involving the sale of the shares against
liabilities, including liabilities arising under the Securities Act. Any
commissions paid or any discounts or concessions allowed to any such
broker-dealers, and any profits received on the resale of those shares, may be
deemed to be underwriting discounts and commissions under the Securities Act if
any such broker-dealers purchase shares as principal. We have agreed to
indemnify the selling stockholders against certain liabilities, including
liabilities under the Securities Act.

    We are required by the Purchase Agreement and Registration Rights Agreement
to register for resale by the selling stockholders and keep registered the
number of shares of common stock they are purchasing or may receive because of a
price adjustment described above under heading "Private Placement to Selling
Shareholders" and 100% of the shares of common stock for which the warrants are
exercisable, including original warrants and warrants received following an
adjustment. We have agreed to and are paying the costs and fees of registering
the common stock. The selling stockholders will pay any brokerage commissions,
discounts or other expenses relating to the sale of the common stock.

    Any securities covered by this prospectus which qualify for sale pursuant to
Rule 144 under the Securities Act may be sold under that rule rather than
pursuant to this prospectus.

    There can be no assurance that the selling stockholders will sell any or all
of the shares of common stock offered by them hereunder.

                                       22
<PAGE>
                         DESCRIPTION OF CAPITAL SHARES

    Our authorized capital consists of 50,000,000 shares of common stock, par
value $0.0001 per share, and 2,000,000 shares of preferred stock, par value
$0.0001 per share.

TRANSFER AGENT

    Our transfer agent and registrar is ChaseMellon Shareholder Services, LLC.

COMMON STOCK


    We are authorized to issue 50,000,000 shares of common stock. As of
February 29, 2000, 16,236,428 shares of common stock were outstanding and were
held of record by approximately 950 shareholders. Holders of common stock are
entitled to one vote for each share at all meetings of our shareholders. Subject
to preferences of Preferred Stockholders, common stockholders are entitled to
receive ratably dividends declared by our Board. Common Stockholders have no
preemptive, subscription, redemption or conversion rights. If we are liquidated
or dissolved, common stockholders would share equally in our assets remaining
after the payment of all our liabilities and the liquidation preference of any
preferred stockholders.


    Holders of 1,857,147 shares of our common stock enjoy the right to receive
additional shares of common stock from the Company without additional payment to
the Company if the Company sells shares of common stock, or engages in similar
financing transactions, at a price of less than $3.50 per share prior to
December 16, 2002, or 33 months have passed since the effective date of the
registration statement relating to this Prospectus. Under certain circumstances,
the Company may be required to redeem shares to be issued to the holders who
enjoy this right. Specifically, if the holdings of the Company's stock by any
holder who enjoys this right will exceed their pro rata share of 20 percent of
the Company's outstanding common stock due to the issuance of new shares, the
Company must redeem the new shares to be issued at a price equal to 110 percent
of the price originally paid for these shares.

PREFERRED STOCK

    Our Board of Directors is authorized to issue up to 2,000,000 shares of
undesignated preferred stock. No shares of preferred stock have been issued. Our
Board has the authority to issue preferred stock in one or more series and to
fix the rights, preferences, privileges and restrictions of the preferred stock,
as well as fix the number of shares, without any further vote or action by the
shareholders. Our Board, without shareholder approval, may issue preferred stock
with voting and conversion rights superior to the voting rights of shares of
common stock. The preferred stock may also decrease the amount of earnings and
assets distributed to Common Stockholders. Issuance of preferred stock may delay
or prevent a change in control.

WARRANTS

    IPO REPRESENTATIVES' WARRANTS.  We issued Representatives' Warrants to the
underwriters of our initial public offering to purchase 400,000 shares of our
common stock. The Representatives' Warrants entitle the holder to acquire up to
200,000 units, each unit consisting of a share of common stock and a Warrant to
purchase a share of common stock for $10.80 per unit and are exercisable until
June 3, 2002. The warrant initially entitles the holder to purchase one share of
common stock at a price of $13.50.

    NASDAQ WARRANTS.  We have outstanding warrants to purchase 2,300,000 shares
of common stock that were issued in our initial public offering and are traded
on the Nasdaq National Market under the symbol AVIIW. These warrants are
exercisable until June 3, 2002. We may redeem them at a price of $0.25 per
warrant if the closing bid price of our common stock has been at least 200% of
the warrant exercise price for twenty (20) consecutive trading days. The initial
exercise price of these warrants is $13.50.

                                       23
<PAGE>
    ITC MERGER WARRANTS.  We have outstanding warrants to purchase 2,116,814
shares of the common stock that were issued in connection with our acquisition
of ImmunoTherapy Corporation. These warrants are exercisable after
September 15, 2000 and until May 15, 2003 at a price of $13.50. We may redeem
them at a price of $0.25 per warrant if the closing bid price of our common
stock has been at least 200% of the exercise price for twenty (20) consecutive
trading days and the warrants have been exercisable. These warrants will be
traded under the symbol AVIIZ.

    OFFERING WARRANTS.  We have issued certain investors 557,144 Warrants. Such
Warrants are exercisable until December 19, 2004 at a price of $4.025 per share
of Common Stock.

    OTHER WARRANTS.  We have also issued warrants to purchase 81,967 shares of
common stock. These warrants are currently exercisable and do not have a
termination date.

    AGENT WARRANTS.  We have issued to a Placement Agent 71,429 Warrants. Such
Agent Warrants have a term of five years and are exercisable at a price of $4.20
per share.

STOCK OPTIONS

    A total of 2,200,000 shares of our common stock are reserved for issuance
under our 1992 Stock Incentive Plan. As of December 31, 1999, we had outstanding
26,941 options to purchase shares under the 1992 Stock Incentive Plan.

    In 1998, we assumed the obligations under the 1997 Stock Option Plan of
ImmunoTherapy Corporation. After the acquisition of ImmunoTherapy Corporation
and as of December 31, 1999, 217,336 options to purchase shares of our common
stock were outstanding under the 1997 plan.

OREGON CONTROL SHARES AND BUSINESS COMBINATION STATUTES

    We are subject to the Oregon Control Share Act (the "Control Share Act").
The Control Share Act generally provides that a person (the "Acquiring Person")
who acquires voting stock of an Oregon corporation in a transaction that results
in the Acquiring Person holding more than 20.0%, 33.3% or 50.0% of the total
voting power of the corporation (a "Control Share Acquisition") cannot vote the
shares it acquires in the Control Share Acquisition ("control shares") unless
voting rights are accorded to the control shares by (i) a majority of each
voting group entitled to vote and (ii) the holders of a majority of the
outstanding voting shares, excluding the control shares held by the Acquiring
Person and shares held by our officers and inside directors. The term "Acquiring
Person" is broadly defined to include persons acting as a group.

    The Acquiring Person may, but is not required to, submit to us a statement
setting forth certain information about the Acquiring Person and its plans with
respect to us. The statement may also request that we call a special meeting of
shareholders to determine whether voting rights will be accorded to the control
shares. If the Acquiring Person does not request a special meeting of
shareholders, the issue of voting rights of control shares will be considered at
the next annual meeting or special meeting of shareholders. If the Acquiring
Person's control shares are accorded voting rights and represent a majority or
more of all voting power, shareholders who do not vote in favor of voting rights
for the control shares will have the right to receive the appraised "fair value"
of their shares which may not be less than the highest price per share by the
Acquiring Person for the control shares.

    We are subject to certain provisions of the Oregon Business Corporation Act
that govern business combinations between corporations and interested
shareholders (the "Business Combination Act"). The Business Combination Act
generally provides that if a person or entity acquires 15% or more of the voting
stock of an Oregon corporation (an "Interested Shareholder"), the corporation
and the Interest Shareholder, or any affiliated entity of the Interested
Shareholder, may not engage in certain business combination transactions for
three years following the date the person became an Interested Shareholder.

                                       24
<PAGE>
Business combination transactions for this purpose include (a) a merger or plan
of share exchange, (b) any sale, lease, mortgage or other disposition of 10% or
more of the assets of the corporation, and (c) certain transactions that result
in the issuance of capital stock of the corporation to the Interested
Shareholder. These restrictions do not apply if (i) the Interested Shareholder,
as a result of the transaction in which such person became an Interested
Shareholder, owns at least 85% of the outstanding voting stock of the
corporation (disregarding shares owned by directors who are officers and certain
employee benefit plans), (ii) the Board of Directors approves the share
acquisition or business combination before the Interested Shareholder acquires
15% or more of the corporation's outstanding voting stock or (iii) the Board of
Directors and the holders of at least two-thirds of the outstanding voting stock
of the corporation (disregarding shares owned by the Interested Shareholder)
approve the transaction after the Interested Shareholder acquires 15% or more of
the corporation's voting stock. See "RISK FACTORS--Anti-Takeover Effects of
Certain Charter Provisions and Oregon Law."

                                 LEGAL MATTERS

    Ater Wynne LLP, 222 S.W. Columbia, Suite 1800, Portland, Oregon 97201, our
attorneys, have opined that the Common Shares are duly and validly issued, fully
paid and nonassessable.

                                    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 included herein in reliance upon the
authority of said firm as experts in accounting and auditing in giving said
report.


                                       25
<PAGE>
                                    PART II
                     INFORMATION NOT REQUIRED IN PROSPECTUS

ITEM 14. OTHER EXPENSES OF ISSUANCE AND DISTRIBUTION.*

<TABLE>
<S>                                                           <C>
SEC Registration Fee........................................  $12,286
Nasdaq Listing Fee..........................................   17,500
Accountant's Fees and Expenses..............................    5,000
Legal Fees and Expense......................................    5,000
Miscellaneous...............................................       --
                                                              -------
Total.......................................................   39,786
                                                              =======
</TABLE>

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

*   Represents expenses related to the distribution by the Selling Shareholders
    pursuant to the Prospectus prepared in accordance with the requirements of
    Form S-3. These expenses will be borne by the Company on behalf of the
    Selling Shareholders. All amounts are estimates except for the SEC
    Registration Fee and the Nasdaq listing fees.

ITEM 15. INDEMNIFICATION OF DIRECTORS AND OFFICERS.

    The Company's Articles of Incorporation provide for indemnification of the
officers and directors of the Company to the fullest extent permitted by law.
The Oregon Business Corporation Act, permits a corporation to limit, under
certain circumstances, a director's liability for monetary damages in actions
brought by the corporation or its stockholders. As an Oregon corporation, the
Company is subject to the OBCA and the exculpation from liability and
indemnification provision contained therein. Pursuant to
Section 60.047(2)(d) of the OBCA, Article II of the Company's Fifth Restated
Articles of Incorporation (the "Articles") eliminates the liability of the
Company's directors to the Company or its stockholders for monetary damages,
except for any liability related to breach of the duty of loyalty, actions not
in good faith and certain other liabilities.

    Section 60.387, ET SEQ., of the OBCA allows corporations to indemnify their
directors and officers against liability where the director or officer has acted
in good faith and with a reasonable belief that actions taken were in the best
interests of the corporation or at least not adverse to the corporation's best
interests and, if in a criminal proceeding, the individual had not reasonable
cause to believe the conduct in question was unlawful. Under the OBCA,
corporations may not indemnify against liability in connection with a claim by
or in the right of the corporation but may indemnity against the reasonable
expenses associated with such claims. Corporations may not indemnify against
breached of the duty of loyalty. The OBCA mandates indemnification against all
reasonable expenses incurred in the successful defense of any claim made or
threatened whether or not such claims was by or in the right of the corporation.
Finally, a court may order indemnification if it determines that the director or
officer is fairly and reasonably entitled to indemnification in view of all the
relevant circumstances whether or not the director or officer met the good faith
and reasonable belief standards or conduct set out in the statute.

    The OBCA also provides that the statutory indemnification provisions are not
deemed exclusive of any other rights to which directors or officers may be
entitled under a corporation's articles of incorporation or bylaws, any
agreement, general or specific action of the board of directors, voce of
stockholders or otherwise.

    The Company's Articles also provide for the elimination of liability of
directors for monetary damages to the full extent permitted by the Oregon
Business Corporations Act.

    The Company has entered into indemnification agreements with its directors
and certain of its officers.

                                       26
<PAGE>
ITEM 16. EXHIBITS.


<TABLE>
<CAPTION>
NUMBER                  EXHIBITS
- ------                  --------
<C>                     <S>
         4.1            Purchase Agreement, dated December 15, 1999, by and between
                        AVI BioPharma, Inc. and certain Investors+

         4.2            Registration Rights Agreement, dated December 15, 1999, by
                        and between AVI BioPharma, Inc. and certain Investors+

         4.3            Form of Common Stock Purchase Warrant+

         4.4            Purchase Agreement, dated December 16, 1999, by and between
                        AVI BioPharma, Inc. and certain Investors+

         4.5            Registration Rights Agreement, dated December 16, 1999, by
                        and between AVI BioPharma, Inc. and certain Investors+

         4.6            Subscription Agreement, dated December 1, 1999, by and
                        between SuperGen, Inc. and AVI BioPharma, Inc.+

         5.1            Opinion of Ater Wynne LLP

        23.1            Consent of Arthur Andersen LLP, independent public
                        accountants

        23.2            Consent of Ater Wynne LLP (included in Exhibit 5.1)

        24.1            Power of Attorney (included on page II-3)
</TABLE>


+   Previously filed.

ITEM 17. UNDERTAKINGS.

    The undersigned registrant hereby undertakes:

    (1) To file, during any period in which offers or sales are being made, a
       post-effective amendment to this registration statement to include any
       material information with respect to the plan of distribution not
       previously disclosed in the registration statement or any material
       changes to such information in this registration statement.

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

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

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

    Insofar as indemnification for liabilities arising under the Securities Act
of 1933 may be permitted to directors, officers and controlling persons of the
registrant pursuant to the foregoing provisions, or otherwise, the registrant
has been advised that in the opinion of the Securities and Exchange Commission
such indemnification is against public policy as expressed in the Act and is,
therefore, unenforceable. In the event that a claim for indemnification is
against public policy as expressed in the Act and is, therefore, unenforceable.
In the event that a claim for indemnification is against such liabilities (other
than the payment by the registrant of expenses incurred or paid by a director,
officer or controlling person of the

                                       27
<PAGE>
registrant in the successful defense of any action, suit or proceeding) is
asserted by such director, officer or controlling person in connection with the
securities being registered, the registrant will, unless in the opinion of its
counsel the matter has been settled by controlling precedent, submit to a court
of appropriate jurisdiction the question of whether such indemnification by it
is against public policy as expressed in the Securities Act and will be governed
by the final adjudication of such issue.

                                       28
<PAGE>
                                   SIGNATURES


    Pursuant to the requirements of the Securities Act of 1933, the registrant
has duly caused this Registration Statement on Form S-3 to be signed on its
behalf by the undersigned, thereunto duly authorized, in the City of Beaverton,
State of Oregon, on February 29, 2000.


<TABLE>
<S>                                                    <C>  <C>
                                                       AVI BIOPHARMA, INC.

                                                       By:             /s/ DENIS R. BURGER
                                                            -----------------------------------------
                                                                      Denis R. Burger, Ph.D.
                                                              PRESIDENT AND CHIEF EXECUTIVE OFFICER
</TABLE>

                               POWER OF ATTORNEY

    KNOW ALL PERSONS BY THESE PRESENTS, that each person whose signature appears
below constitutes and appoints Denis R. Burger and Alan P. Timmins, jointly and
severally, his attorneys-in-fact, each with the power of substitution, for him
in any and all capacities, to sign any amendment to this Registration Statement
on Form S-3 and to file the same, with exhibits thereto and other documents in
connection therewith, with the Securities and Exchange Commission, hereby
ratifying and confirming all that each of said attorneys-in-fact, or his
substitute or substitutes, may do or cause to be done by virtue hereof.

    Pursuant to the requirements of the Securities Act of 1933, this
Registration Statement has been signed by the following persons in the
capacities on the date indicated.


<TABLE>
<CAPTION>
                      SIGNATURE                                   TITLE                    DATE
                      ---------                                   -----                    ----
<C>                                                    <S>                           <C>
                                                       President, Chief Executive
             /s/ DENIS R. BURGER, PH.D.                  Officer and Chairman of
     -------------------------------------------         the Board (Principal        February 29, 2000
               Denis R. Burger, Ph.D.                    Executive Officer)

                                                       Chief Operating Officer,
                 /s/ ALAN P. TIMMINS                     Chief Financial Officer
     -------------------------------------------         and Director (Principal     February 29, 2000
                   Alan P. Timmins                       Financial and Accounting
                                                         Officer)

                                                       Senior Vice President of
             /s/ DWIGHT D. WELLER, PH.D.                 Chemistry and
     -------------------------------------------         Manufacturing And           February 29, 2000
               Dwight D. Weller, Ph.D.                   Development and Director

            /s/ PATRICK L. IVERSON, PH.D.              Senior Vice President of
     -------------------------------------------         Research and Development    February 29, 2000
              Patrick L. Iverson, Ph.D.                  and Director
</TABLE>


                                       29
<PAGE>


<TABLE>
<CAPTION>
                      SIGNATURE                                   TITLE                    DATE
                      ---------                                   -----                    ----
<C>                                                    <S>                           <C>
            /s/ BRUCE L. A. CARTER, PH.D.
     -------------------------------------------       Director                      February 29, 2000
              Bruce L. A. Carter, Ph.D.

                   /s/ NICK BUNICK
     -------------------------------------------       Director                      February 29, 2000
                     Nick Bunick

                /s/ JOSEPH RUBINFELD
     -------------------------------------------       Director                      February 29, 2000
                  Joseph Rubinfeld
</TABLE>


                                       30
<PAGE>
                               INDEX TO EXHIBITS


<TABLE>
<CAPTION>
NUMBER
- ------
<C>                     <S>
         4.1            Purchase Agreement, dated December 15, 1999, by and between
                        AVI BioPharma, Inc. and certain Investors+

         4.2            Registration Rights Agreement, dated December 15, 1999, by
                        and between AVI BioPharma, Inc. and certain Investors+

         4.3            Form of Common Stock Purchase Warrant+

         4.4            Purchase Agreement, dated December 16, 1999, by and between
                        AVI BioPharma, Inc. and certain Investors+

         4.5            Registration Rights Agreement, dated December 16, 1999, by
                        and between AVI BioPharma, Inc. and certain Investors+

         4.6            Subscription Agreement, dated December 1, 1999, by and
                        between SuperGen, Inc. and AVI BioPharma, Inc.+

         5.1            Opinion of Ater Wynne LLP

        23.1            Consent of Arthur Andersen LLP, independent public
                        accountants

        23.2            Consent of Ater Wynne LLP (included in Exhibit 5.1)

        24.1            Power of Attorney (included on page II-3)
</TABLE>


+   Previously filed.

                                       31

<PAGE>

                                                                    EXHIBIT 5.1

                                 ATER WYNNE LLP

                                   LETTERHEAD


                                February 29, 2000


Board of Directors AVI BioPharma, Inc.
One S.W. Columbia Street, Suite 1105
Portland, OR 97258

Gentlemen:

         In connection with the registration of 2,857,147 shares of common
stock, $.0001 par value (the "Common Stock"), and 557,144 shares of common
stock, .0001 par value, underlying certain Warrants (the "Warrant Shares"), of
AVI BioPharma, Inc., an Oregon corporation (the "Company"), under the
Registration Statement on Form S-3 to be filed with the Securities and Exchange
Commission on January 24, 2000, and the proposed offer and sale of the Common
Stock and Warrant Shares pursuant to the Registration Statement, we have
examined such corporate records, certificates of public officials and officers
of the Company and other documents as we have considered necessary or proper for
the purpose of this opinion.

         Based on the foregoing and having regard to legal issues which we deem
relevant, it is our opinion that the shares of Common Stock are validly issued,
fully paid and nonassessable. It is our further opinion that the Warrant Shares,
when such shares have been delivered against payment therefor as contemplated by
the Warrants, will be validly issued, fully paid and nonassessable.

         We hereby consent to the filing of this opinion as an exhibit to the
above-mentioned registration statement.

                                            Very truly yours,

                                            /s/ Ater Wynne LLP

                                            ATER WYNNE LLP

<PAGE>


                                                                    EXHIBIT 23.1

                    CONSENT OF INDEPENDENT PUBLIC ACCOUNTANTS


As independent public accountants, we hereby consent to the incorporation by
reference in Amendment No. 2 to the Registration Statement on Form S-3 of our
report dated January 28, 2000, included in the Company's Form 10-K for the
year ended December 31, 1999 and to all references to our firm included in
this registration statement.


/s/ Arthur Andersen LLP


Portland, Oregon
February 29, 2000




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