Document:

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                                                                   EXHIBIT 4.1

                                 SUPERGEN, INC.
                           TWO ANNABEL LANE, SUITE 220
                           SAN RAMON, CALIFORNIA 94583

                               AVI BIOPHARMA, INC.
                           ONE SW COLUMBIA, SUITE 1105
                               PORTLAND, OR 97258

                          REGISTRATION RIGHTS AGREEMENT

                                  APRIL 4, 2000

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                          REGISTRATION RIGHTS AGREEMENT

         This Registration Rights Agreement (the "Agreement") is made as of
April 4, 2000 between SuperGen, Inc., a Delaware corporation ("SuperGen") and
AVI BioPharma, Inc., an Oregon corporation ("AVI") pursuant to the terms of a
Common Stock and Warrant Purchase Agreement between the parties dated as of
April 4, 2000 (the "Purchase Agreement").

                                   SECTION 1

                                   DEFINITIONS

         1.1       DEFINITIONS. As used in this Agreement, the following terms
shall have the following respective meanings:

         "ADDITIONAL SUPERGEN SHARES" shall mean the shares of SuperGen Common
Stock AVI receives from SuperGen pursuant to Section 1.3 of the Purchase
Agreement.

         "AVI COMMON STOCK" shall mean AVI's common stock, par value $0.0001 per
share.

         "AVI SHARES" shall mean the shares of AVI Common Stock that SuperGen
purchases from AVI pursuant to Section 1.2 of the Purchase Agreement.

         "CLOSING DATE" shall mean the Closing Date as defined in Section 2 of
the Purchase Agreement.

         "COMMISSION" shall mean the Securities and Exchange Commission or any
other federal agency at the time administering the Securities Act.

         "MATERIAL EVENT" shall mean the happening of any event during the
period that the registration statement described in Sections 2.1 and 3.1 hereof
is required to be effective as a result of which, in the reasonable judgment of
AVI or SuperGen, as the case may be, such registration statement or the related
prospectus contains or may contain any untrue statement of a material fact or
omits or may omit to state any material fact required to be stated therein or
necessary to make the statements therein not misleading.

         "FORM S-3" means such form under the Securities Act as in effect on the
date hereof or any registration form under the Securities Act subsequently
adopted by the SEC which similarly permits inclusion or incorporation of
substantial information by reference to other documents filed by either AVI or
SuperGen with the Commission.

         "HOLDER" shall mean, for purposes of Section 2, SuperGen or any person
holding Registrable Securities to whom SuperGen's rights under Section 2 of this
Agreement have been transferred in accordance with Section 2.9, and for purposes
of Section 3, AVI or any person holding Registrable Securities to whom AVI's
rights under Section 3 of this Agreement have been transferred in accordance
with Section 3.8.

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         "INITIAL HOLDERS" shall mean SuperGen or any Holders who in aggregate
hold greater than 20% of the Registrable Securities for purposes of Section 2.

         "REGISTRABLE SECURITIES" shall mean, for purposes of Section 2, AVI
Shares and Warrant Shares, and for purposes of Section 3, SuperGen Shares or
Additional SuperGen Shares, as the case may be, until such time that such
securities have been (i) sold to or through a broker or dealer or underwriter in
a public distribution or a public securities transaction, or (ii) sold or are,
in the opinion of counsel for AVI in the case of AVI Shares and Warrant Shares,
and SuperGen in the case of SuperGen Shares and Additional SuperGen Shares,
available for sale in a single transaction exempt from the registration and
prospectus delivery requirements of the Securities Act so that all transfer
restrictions and restrictive legends with respect thereto are removed upon the
consummation of such sale.

         The terms "REGISTER," "REGISTERED" and "REGISTRATION" refer to a
registration effected by preparing and filing a registration statement in
compliance with the Securities Act, and the declaration or ordering of the
effectiveness of such registration statement.

         "REGISTRATION EXPENSES" shall mean all expenses, except as otherwise
stated below, incurred by AVI or SuperGen, as the registering company, in
complying with Sections 2.1, 2.2 and 2.3 (applicable to AVI) or Sections 3.1 and
3.2 (applicable to SuperGen) hereof, including, without limitation, all
registration, qualification and filing fees, printing expenses, escrow fees,
fees and disbursements of counsel for such registering company, blue sky fees
and expenses, the expense of any special audits incident to or required by any
such registration (but excluding the compensation of regular employees of AVI or
SuperGen as the registering company which shall be paid in any event by the
registering company).

         "RESTRICTED SECURITIES" shall mean any AVI Shares, Warrant Shares,
SuperGen Shares or Additional SuperGen Shares required to bear the legend set
forth in Section 5.6 of the Purchase Agreement.

         "SECURITIES ACT" shall mean the Securities Act of 1933, as amended, or
any similar federal statute and the rules and regulations of the Commission
thereunder, all as the same shall be in effect at the time.

         "SELLING EXPENSES" shall mean all underwriting discounts, selling
commissions and stock transfer taxes applicable to the securities registered by
AVI (related to Sections 2.1, 2.2 and 2.3 ) or SuperGen (related to Sections 3.1
and 3.2, except as set forth above, all reasonable fees and disbursements of
counsel for SuperGen or AVI.

         "SUPERGEN COMMON STOCK" shall mean the common stock of SuperGen, par
value $0.001.

         "SUPERGEN SHARES" shall mean the shares of SuperGen Common Stock issued
to AVI pursuant to Section 1.2 of the Purchase Agreement.

         "WARRANT" shall mean the warrant AVI shall issue to SuperGen pursuant
to Section 1.4 of the Purchase Agreement.

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         "WARRANT SHARES" shall mean the shares of AVI Common Stock issued or
issuable upon exercise of the Warrant.

                                   SECTION 2

                  REGISTRATION OF AVI SHARES AND WARRANT SHARES

         2.1       REGISTRATION OF AVI SHARES.

                   (a)  REGISTRATION. AVI shall use commercially reasonable
efforts to cause the AVI Shares which are Registrable Securities to be
registered under the Securities Act no later than 90 days after the Closing
Date, so as to permit the resale thereof, and in connection therewith shall
prepare and file with the SEC and shall use commercially reasonable efforts to
cause to become effective, a Form S-3 covering the AVI Shares; PROVIDED,
HOWEVER, that the Holders, if any, shall provide all such information and
materials relating to the Holders, as applicable, and take all such action as
may be required in order to permit AVI to comply with all the applicable
requirements of the Commisson and to obtain any desired acceleration of the
effective date of such Form S-3, such provision of information and materials to
be a condition precedent to the obligations of AVI pursuant to this Agreement
and the Purchase Agreement. The offerings made pursuant to such registrations
shall not be underwritten.

                   (b)  POSTPONEMENT OF REGISTRATION.

                        (i)   REGISTRATION. Notwithstanding Section 2.1(a)
above, AVI shall be entitled to postpone the declaration of effectiveness of any
Form S-3 prepared and filed pursuant to this Section 2.1 for a reasonable period
of time, but not in excess of 60 calendar days after the applicable deadline, if
the Board of Directors of AVI, acting in good faith, determines that there
exists material non-public information about AVI.

                        (ii)  MATERIAL EVENT. The Holders agree that, upon
receipt of any notice from AVI of the happening of a Material Event, they will
forthwith discontinue disposition of the AVI Shares which are Registrable
Securities pursuant to any Form S-3 until the receipt of copies of supplemented
or amended prospectuses prepared by AVI (which AVI will use its commercially
reasonable efforts to prepare and file promptly), and, if so directed by AVI,
the Holders will deliver to AVI all copies in their possession, other than
permanent file copies then in the Holders' possession, of the prospectus
covering such AVI Shares current at the time of receipt of such notice. In no
event shall AVI delay causing to be effective a supplement or post-effective
amendment to any Form S-3 pursuant to Section 2.1 or the related prospectus, for
more than 90 consecutive days or 120 days during any 365 consecutive calendar
day period.

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         2.2       REGISTRATION OF WARRANT SHARES; REQUESTED REGISTRATION.

                   (a)  REQUEST FOR REGISTRATION. If, at any time after the date
SuperGen exercises its Warrant, in whole or in part, AVI shall receive from the
Initial Holders a written request that AVI effect any registration,
qualification or compliance with respect to the Warrant Shares which are
Registrable Securities, AVI will,

                        (i)   promptly give written notice of the proposed
registration, qualification or compliance to any other Holders; and

                        (ii)  as soon as practicable, use its diligent efforts
to effect such registration, qualification or compliance (including, without
limitation, appropriate qualification under applicable blue sky or other state
securities laws and appropriate compliance with applicable regulations issued
under the Securities Act and any other governmental requirements or regulations)
as may be so requested and as would permit or facilitate the sale and
distribution of all or such portion of such Registrable Securities as are
specified in such request, together with all or such portion of Registrable
Securities of other Holders, if any, joining in such request as are specified in
a written request received by AVI within 20 days after receipt of such written
notice from AVI; PROVIDED, HOWEVER, that AVI shall not be obligated to take any
action to effect any such registration, qualification or compliance pursuant to
this Section 2.2:

                              (A)  During the period starting with the date 60
days prior to AVI's estimated date of filing of, and ending on the date 3 months
immediately following the effective date of, any registration statement
pertaining to securities of AVI (other than a registration of securities in a
Rule 145 transaction or with respect to an employee benefit plan), provided that
AVI is actively employing in good faith all reasonable efforts to cause such
registration statement to become effective;

                              (B)  Unless the Registrable Securities sought to
be registered by the Initial Holders and other Holders pursuant to this Section
2.2 comprise at least 100,000 Warrant Shares;

                              (C)  After the Company has effected two such
registration pursuant to this Section 2.2(a), and such registration has been
declared or ordered effective and the securities offered pursuant to such
registrations have been sold; or

                              (D)  If AVI shall furnish to the Holders a
certificate signed by the President of AVI stating that in the good faith
judgment of the Board of Directors it would be seriously detrimental to AVI or
its shareholders for a registration statement to be filed in the near future,
then AVI's obligation to use its best efforts to register, qualify or comply
under this Section 2.2 shall be deferred for a period not to exceed 60 days from
the date of receipt of written request from the Initiating Holders, PROVIDED,
HOWEVER, that AVI shall not exercise the right to defer registration granted
pursuant to this paragraph (D) more than one time in any twelve month period.

         Subject to the foregoing clauses (A) through (D), AVI shall file a
registration statement covering the Registrable Securities so requested to be
registered as soon as practicable after receipt of the request or requests of
the Holders, but in any event within 120 days of such request or requests.

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                   (b)  UNDERWRITING. In the event that a registration pursuant
to Section 2.2(a) is for a registered public offering involving an underwriting,
AVI shall so advise the Holders (as part of the notice given pursuant to Section
2.2 (a)(i). In such event, the right of the Holders to registration pursuant to
Section 2.2(a) shall be conditioned upon such Holders' participation in the
underwriting arrangements required by this Section 2.2(b), and the inclusion of
such Holders' Warrant Shares which are Registrable Securities in the
underwriting to the extent requested shall be limited to the extent provided
herein.

         AVI shall (together with all Holders proposing to distribute their
securities through such underwriting) enter into an underwriting agreement in
customary form with the managing underwriter selected for such underwriting by a
majority in interest of the Holders, but subject to AVI's reasonable approval.
Notwithstanding any other provision of this Section 2.2, if the managing
underwriter advises the Holders in writing that marketing factors require a
limitation of the number of shares to be underwritten, then AVI shall so advise
all Holders of Warrant Shares which are Registrable Securities and the number of
Registrable Securities that may be included in the registration and underwriting
shall be allocated among all Holders thereof in proportion, as nearly as
practicable, to the respective amounts of Registrable Securities held by such
Holders at the time of filing the registration statement. No Registrable
Securities excluded from the underwriting by reason of the underwriter's
marketing limitation shall be included in such registration. To facilitate the
allocation of shares in accordance with the above provisions, AVI or the
underwriters may round the number of shares allocated to any Holder to the
nearest 100 shares.

                   (c)  If any Holder of Registrable Securities disapproves of
the terms of the underwriting, such person may elect to withdraw therefrom by
written notice to AVI, the managing underwriter and the Initial Holders. The
Registrable Securities and/or other securities so withdrawn shall also be
withdrawn from registration, and shall not be transferred in a public
distribution prior to 180 days after the effective date of the registration
statement relating thereto, or such other shorter period of time as the
underwriters may require.

         2.3       AVI REGISTRATION

                   (a)  NOTICE OF REGISTRATION. If at any time or from time
to time, but in no event earlier than SuperGen's exercise of the Warrant, AVI
shall determine to register any of its securities, either for its own account
or the account of a security holder or holders, other than (i) a registration
relating solely to employee benefit plans, or (ii) a registration relating
solely to a Commission Rule 145 transaction, AVI will:

                        (i)  promptly give to all Holders of Warrant Shares
which are Registrable Securities written notice thereof; and

                       (ii)  include in such registration (and any related
qualification under blue sky laws or other compliance), and in any
underwriting involved therein, all the Registrable Securities specified in a
written request or requests, made within twenty (20) days after receipt of
such written notice from AVI, by all Holders.

                   (b)  UNDERWRITING. If the registration of which AVI gives
notice is for a registered public offering involving an underwriting, AVI shall
so advise the Holders as a part of the

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written notice given pursuant to Section 2.3(a)(i). In such event the right of
and the Holders to registration pursuant to this Section 2.3 shall be
conditioned upon the Holders' participation in such underwriting and the
inclusion of the Registrable Securities in the underwriting shall be limited to
the extent provided herein. All Holders proposing to distribute their securities
through such underwriting shall, together with AVI, enter into an underwriting
agreement in customary form with the managing underwriter selected for such
underwriting by AVI. Notwithstanding any other provision of this Section 2.3, if
the managing underwriter determines that marketing factors require a limitation
of the number of shares to be underwritten, the managing underwriter and AVI may
reduce the securities to be included in such registration to the extent the
underwriters deem necessary (to zero if necessary). AVI shall so advise the
Holders and all holders of securities distributing their securities through such
underwriting and the number of shares of Registrable Securities that may be
included in the registration and underwriting shall be allocated among all such
holders in proportion, as nearly as practicable, to the respective amounts of
Registrable Securities held by the Holders at the time of filing the
registration statement. To facilitate the allocation of shares in accordance
with the above provisions, AVI may round the number of shares allocated to any
Holder or holder to the nearest 100 shares. If any Holder or holder disapproves
of the terms of any such underwriting, it may elect to withdraw therefrom by
written notice to AVI and the managing underwriter. Any securities excluded or
withdrawn from such underwriting shall be withdrawn from such registration, and
shall not be transferred in a public distribution prior to 180 days after the
effective date of the registration statement relating thereto, or such other
shorter period of time as the underwriters may require.

                   (c)  RIGHT TO TERMINATE REGISTRATION. AVI shall have the
right to terminate or withdraw any registration initiated by it under this
Section 2.4 prior to the effectiveness of such registration whether or not any
holder has elected to include securities in such registration.

         2.4       REGISTRATION PROCEDURES. In the case of each registration,
qualification or compliance effected by AVI pursuant to this Section 2
(including the registration on Form S-3), AVI will keep the Holders advised in
writing as to the initiation of each registration, qualification and compliance
and as to the completion thereof. At its expense AVI will:

                   (a)  Prepare and file with the Commission a registration
statement with respect to such securities and use its best efforts to cause such
registration statement to become and remain continuously effective for at least
one year or until the sale of all Registrable Securities described in the
Registration Statement has been completed;

                   (b)  Furnish to the Holders such reasonable number of copies
of the registration statement, preliminary prospectus, final prospectus and such
other documents as the Holders or such underwriters may reasonably request in
order to effect the offering and sale of the shares to be offered and sold, but
only while AVI shall be required under the provisions hereof to cause such
registration statement to remain current;

                   (c)  Use its commercially reasonable efforts to register or
qualify the shares of the Registrable Securities covered by such registration
under the securities or blue sky laws of such jurisdictions as the Holders shall
reasonably request (provided that AVI shall not be required in connection
therewith or as a condition thereto to qualify to do business or to file a
general consent to service of process in any such jurisdiction where it has not
been qualified), and do any and all other

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acts or things which may be reasonably necessary or advisable to enable the
Holders to consummate the public sale or other disposition of the Registrable
Securities in such jurisdictions;

                   (d)  Cause all such Registrable Securities to be listed on
the Nasdaq National Market ("NNM") on which similar securities issued by AVI are
then listed;

                   (e)  Notify the Holders upon the happening of any event as a
result of which the prospectus included in such registration statement, as then
in effect, includes an untrue statement of a material fact or omits to state a
material fact required to be stated therein or necessary to make the statements
therein not misleading in the light of the circumstances then existing;

                   (f)  So long as the registration statement remains effective,
promptly prepare, file and furnish to the Holders a reasonable number of copies
of a supplement to or an amendment of such prospectus as may be necessary so
that, as thereafter delivered to the purchasers of the Registrable Securities,
such prospectus shall not include an untrue statement of a material fact or omit
to state a material fact required to be stated therein or necessary to make the
statements therein not misleading in the light of the circumstances then
existing;

                   (g)  Notify the Holders promptly after it shall receive
notice thereof, of the date and time any registration statement and each
post-effective amendment thereto has become effective or a supplement to any
prospectus forming a part of such registration statement has been filed;

                   (h)  Notify the Holders promptly of any request by the
Commission for the amending or supplementing of such registration statement or
prospectus or for additional information; and

                   (i)  Advise the Holders promptly after it shall receive
notice or obtain knowledge thereof, of the issuance of any stop order by the
Commission suspending the effectiveness of any registration statement or the
initiation or threatening of any proceeding for that purpose and promptly use
commercially reasonable efforts to prevent the issuance of any stop order or to
obtain its withdrawal if such stop order should be issued.

         2.5       EXPENSES OF REGISTRATION. All Registration Expenses incurred
in connection with all registrations pursuant to this Section 2 shall be borne
by AVI. Unless otherwise stated, all Selling Expenses relating to securities
registered on behalf of any holders of securities participating in the
distribution and all other Registration Expenses shall be borne by such holders
pro rata on the basis of the number of shares so registered.

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         2.6       INDEMNIFICATION.

                   (a)  AVI will indemnify each Holder, each of its officers and
directors, and each person controlling such Holder within the meaning of Section
15 of the Securities Act, with respect to which registration, qualification or
compliance has been effected pursuant to this Section 2, and each underwriter,
if any, and each person who controls any underwriter within the meaning of
Section 15 of the Securities Act, against all expenses, claims, losses, damages
or liabilities (or actions in respect thereof), including any of the foregoing
incurred in settlement of any litigation, commenced or threatened, arising out
of or based on any untrue statement (or alleged untrue statement) of a material
fact contained in any registration statement, prospectus, offering circular or
other document, or any amendment or supplement thereto, incident to any such
registration, qualification or compliance, or based on any omission (or alleged
omission) to state therein a material fact required to be stated therein or
necessary to make the statements therein, in light of the circumstances in which
they were made, not misleading, or any violation by AVI of the Securities Act,
the Exchange Act, state securities law or any rule or regulation promulgated
under such laws applicable to AVI in connection with any such registration,
qualification or compliance, and within a reasonable period AVI will reimburse
each Holder, each of its officers and directors, and each person controlling
such Holder, each such underwriter and each person who controls any such
underwriter, for any legal and any other expenses reasonably incurred in
connection with investigating, preparing or defending any such claim, loss,
damage, liability or action; provided that AVI will not be liable in any such
case to the extent that any such claim, loss, damage, liability or expense
arises out of or is based on any untrue statement or omission or alleged untrue
statement or omission, made in reliance upon and in conformity with written
information furnished to AVI by an instrument duly executed by any Holder, such
controlling person or underwriter and stated to be specifically for use therein.

                   (b)  Each Holder will indemnify AVI, each of its directors
and officers, each underwriter, if any, of AVI's securities covered by such a
registration statement, each person who controls AVI or such underwriter within
the meaning of Section 15 of the Securities Act, and each other Holder
participating in the distribution, each of its officers and directors and each
person controlling such other Holder within the meaning of Section 15 of the
Securities Act, against all claims, losses, damages and liabilities (or actions
in respect thereof) arising out of or based on any untrue statement (or alleged
untrue statement) of a material fact contained in any such registration
statement, prospectus, offering circular or other document, or any omission (or
alleged omission) to state therein a material fact required to be stated therein
or necessary to make the statements therein not misleading, and within a
reasonable period will reimburse AVI, such other Holders, such directors,
officers, persons, underwriters or control persons for any legal or any other
expenses reasonably incurred in connection with investigating or defending any
such claim, loss, damage, liability or action, in each case to the extent, but
only to the extent, that such untrue statement (or alleged untrue statement) or
omission (or alleged omission) is made in such registration statement,
prospectus, offering circular or other document in reliance upon and in
conformity with written information furnished to AVI by an instrument duly
executed by the Holder and stated to be specifically for use therein.
Notwithstanding the foregoing, the liability of each Holder under this
subsection (b) shall be limited in an amount equal to the gross proceeds before
expenses and commissions to each Holder received for the shares sold by such
Holder, unless such liability arises out of or is based on willful misconduct by
such Holder.

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                   (c)  Each party entitled to indemnification under this
Section 2.6 (the "Indemnified Party") shall give notice to the party required to
provide indemnification (the "Indemnifying Party") promptly after such
Indemnified Party has actual knowledge of any claim as to which indemnity may be
sought, and shall permit the Indemnifying Party to assume the defense of any
such claim or any litigation resulting therefrom, provided that counsel for the
Indemnifying Party, who shall conduct the defense of such claim or litigation,
shall be approved by the Indemnified Party (whose approval shall not
unreasonably be withheld), and the Indemnified Party may participate in such
defense at such party's expense, and provided further that the failure of any
Indemnified Party to give notice as provided herein shall not relieve the
Indemnifying Party of its obligations under this Section 2.7 unless the failure
to give such notice is materially prejudicial to an Indemnifying Party's ability
to defend such action and provided further, that the Indemnifying Party shall
not assume the defense for matters as to which there is a conflict of interest
or separate and different defenses. No Indemnifying Party, in the defense of any
such claim or litigation, shall, except with the consent of each Indemnified
Party, consent to entry of any judgment or enter into any settlement which does
not include as an unconditional term thereof the giving by the claimant or
plaintiff to such Indemnified Party of a release from all liability in respect
to such claim or litigation.

         2.7       INFORMATION BY HOLDER. Each Holder shall furnish to AVI such
information regarding such Holder, the Registrable Securities held by it and the
distribution proposed by such Holder as AVI may request in writing and as shall
be required in connection with any registration, qualification or compliance
referred to in this Section 2.

         2.8       RULE 144 REPORTING. With a view to making available the
benefits of certain rules and regulations of the Commission which may at any
time permit the sale of Restricted Securities to the public without
registration, AVI agrees to use its best efforts to:

                   (a)  Make and keep public information available, as those
terms are understood and defined in Rule 144 under the Securities Act, at all
times;

                   (b)  Use its best efforts to file with the Commission in a
timely manner all reports and other documents required of AVI under the
Securities Act and the Exchange Act; and

                   (c)  So long as a Holder owns any Restricted Securities,
furnish to the Holder forthwith upon request a written statement by AVI as to
its compliance with the reporting requirements of said Rule 144 and of the
Securities Act and the Exchange Act, a copy of the most recent annual or
quarterly report of AVI, and such other reports and documents of AVI and
other information in the possession of or reasonably obtainable by AVI as the
Holder may reasonably request in availing itself of any rule or regulation of
the Commission allowing the Holder to sell any such securities without
registration.

         2.9       TRANSFER OF REGISTRATION RIGHTS. The rights to cause AVI to
register securities granted a Holder under Sections 2.1, 2.2 and 2.3 may be
assigned to a transferee or assignee reasonably acceptable to AVI which acquires
at least 250,000 AVI Shares or Warrant Shares in connection with any transfer or
assignment of AVI Shares or Warrant Shares by the Holder.

         2.10      STANDOFF AGREEMENT. In connection with any public offering of
AVI's securities, each Holder agrees, upon request of AVI or the underwriters
managing any underwritten offering of

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AVI's securities, not to sell, make any short sale of, loan, grant any option
for the purchase of, or otherwise dispose of any AVI Shares or Warrant Shares
(other than those included in the registration) without the prior written
consent of AVI or such underwriters, as the case may be, for such period of time
(not to exceed ninety (90) days) from the effective date of such registration as
may be requested by the underwriters, provided that the officers and directors
of AVI who own stock of AVI and each holder representing at least 1% ownership
of AVI's outstanding Common Stock also agrees to such restrictions.

         2.11      TERMINATION OF REGISTRATION RIGHTS. The registration rights
granted pursuant to this Section 2 shall terminate as to each Holder at such
time as all AVI Shares or Warrant Shares held by such Holder may, in the opinion
of counsel to AVI (which opinion shall be addressed and rendered to the Holder),
be sold in a single three month period pursuant to Rule 144.

                                   SECTION 3

         REGISTRATION OF SUPERGEN SHARES AND ADDITIONAL SUPERGEN SHARES

         3.1       REGISTRATION OF SUPERGEN SHARES.

                   (a)  REGISTRATION STATEMENT. SuperGen shall use commercially
reasonable efforts to cause the SuperGen Shares which are Registrable Securities
to be registered under the Securities Act no later than 90 days after the
Closing Date, so as to permit the resale thereof, and in connection therewith
shall prepare and file with the SEC and shall use commercially reasonable
efforts to cause to become effective, a Form S-3 covering the SuperGen Shares;
PROVIDED, HOWEVER, that the Holders, if any, shall provide all such information
and materials relating to the Holders, as applicable, and take all such action
as may be required in order to permit SuperGen to comply with all the applicable
requirements of the SEC and to obtain any desired acceleration of the effective
date of such Form S-3, such provision of information and materials to be a
condition precedent to the obligations of SuperGen pursuant to this Agreement
and the Purchase Agreement. The offerings made pursuant to such registrations
shall not be underwritten.

                   (b)  POSTPONEMENT OF REGISTRATION

                        (i)   REGISTRATION. Notwithstanding Section 3.1(a)
above, SuperGen shall be entitled to postpone the declaration of effectiveness
of any Form S-3 prepared and filed pursuant to this Section 3.1 for a reasonable
period of time, but not in excess of 60 calendar days after the applicable
deadline, if the Board of Directors of SuperGen, acting in good faith,
determines that there exists material non-public information about SuperGen.

                        (ii)  MATERIAL EVENT. The Holders agree that, upon
receipt of any notice from SuperGen of the happening of a Material Event, they
will forthwith discontinue disposition of the SuperGen Shares which are
Registrable Securities pursuant to any Form S-3 until the receipt of copies of
supplemented or amended prospectuses prepared by SuperGen (which SuperGen will
use its commercially reasonable efforts to prepare and file promptly), and, if
so directed by SuperGen, the Holders will deliver to SuperGen all copies in
their possession, other than permanent file copies then in the Holders'
possession, of the prospectus covering such SuperGen Shares current at the time
of receipt of such notice. In no event shall SuperGen delay causing to be
effective a supplement or

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post-effective amendment to any Form S-3 pursuant to this Section 3.1 or the
related prospectus, for more than 90 consecutive days or 120 days during any 365
consecutive calendar day period.

         3.2       SUPERGEN REGISTRATION

                   (a)  NOTICE OF REGISTRATION. If at any time or from time to
time, but in no event earlier than the issuance of any SuperGen Additional
Shares, SuperGen shall determine to register any of its securities, either for
its own account or the account of a security holder or holders, other than (i) a
registration relating solely to employee benefit plans, or (ii) a registration
relating solely to a Commission Rule 145 transaction, SuperGen will:

                        (i)   promptly give to all Holders of SuperGen
Additional Shares which are Registrable Securities, if any, written notice
thereof; and

                        (ii)  include in such registration (and any related
qualification under blue sky laws or other compliance), and in any underwriting
involved therein, all the Registrable Securities specified in a written request
or requests, made within twenty (20) days after receipt of such written notice
from SuperGen, by all Holders.

                   (b)  UNDERWRITING. If the registration of which SuperGen
gives notice is for a registered public offering involving an underwriting,
SuperGen shall so advise the Holders as a part of the written notice given
pursuant to Section 3.2(a)(i). In such event the right of the Holders to
registration pursuant to this Section 3.2 shall be conditioned upon the Holders'
participation in such underwriting and the inclusion of the Registrable
Securities in the underwriting shall be limited to the extent provided herein.
All Holders proposing to distribute their securities through such underwriting
shall, together with SuperGen, enter into an underwriting agreement in customary
form with the managing underwriter selected for such underwriting by SuperGen.
Notwithstanding any other provision of this Section 3.2, if the managing
underwriter determines that marketing factors require a limitation of the number
of shares to be underwritten, the managing underwriter and SuperGen may reduce
the securities to be included in such registration to the extent the
underwriters deem necessary (to zero if necessary). SuperGen shall so advise all
Holders and other holders distributing their securities through such
underwriting and the number of shares of Registrable Securities that may be
included in the registration and underwriting shall be allocated among all such
Holders and holders in proportion, as nearly as practicable, to the respective
amounts of Registrable Securities held by such Holders at the time of filing the
Registration Statement. To facilitate the allocation of shares in accordance
with the above provisions, SuperGen may round the number of shares allocated to
any Holder or holder to the nearest 100 shares. If any Holder or holder
disapproves of the terms of any such underwriting, it may elect to withdraw
therefrom by written notice to SuperGen and the managing underwriter. Any
securities excluded or withdrawn from such underwriting shall be withdrawn from
such registration, and shall not be transferred in a public distribution prior
to 180 days after the effective date of the registration statement relating
thereto, or such other shorter period of time as the underwriters may require.

                   (c)  RIGHT TO TERMINATE REGISTRATION. SuperGen shall have the
right to terminate or withdraw any registration initiated by it under this
Section 3.2 prior to the effectiveness of such registration whether or not any
holder has elected to include securities in such registration.

                                      -12-
<PAGE>

         3.3       REGISTRATION PROCEDURES. In the case of each registration,
qualification or compliance effected by SuperGen pursuant to this Section 3
(including the registration Form S-3), SuperGen will keep advised in writing as
to the initiation of each registration, qualification and compliance and as to
the completion thereof. At its expense SuperGen will:

                   (a)  Prepare and file with the Commission a registration
statement with respect to such securities and use its best efforts to cause such
registration statement to become and remain continuously effective for at least
one year or until the sale of all Registrable Securities described in the
Registration Statement has been completed;

                   (b)  Furnish to the Holders such reasonable number of copies
of the registration statement, preliminary prospectus, final prospectus and such
other documents as the Holders or such underwriters may reasonably request in
order to effect the offering and sale of the shares to be offered and sold, but
only while SuperGen shall be required under the provisions hereof to cause such
registration statement to remain current;

                   (c)  Use its commercially reasonable efforts to register or
qualify the shares of the Registrable Securities covered by such registration
under the securities or blue sky laws of such jurisdictions as the Holders shall
reasonably request (provided that SuperGen shall not be required in connection
therewith or as a condition thereto to qualify to do business or to file a
general consent to service of process in any such jurisdiction where it has not
been qualified), and do any and all other acts or things which may be reasonably
necessary or advisable to enable the Holders to consummate the public sale or
other disposition of the Registrable Securities in such jurisdictions;

                   (d)  Cause all such Registrable Securities to be listed on
the NNM on which similar securities issued by AVI are then listed;

                   (e)  Notify the Holders upon the happening of any event as a
result of which the prospectus included in such registration statement, as then
in effect, includes an untrue statement of a material fact or omits to state a
material fact required to be stated therein or necessary to make the statements
therein not misleading in the light of the circumstances then existing;

                   (f)  So long as the registration statement remains effective,
promptly prepare, file and furnish to the Holders a reasonable number of copies
of a supplement to or an amendment of such prospectus as may be necessary so
that, as thereafter delivered to the purchasers of the Registrable Securities,
such prospectus shall not include an untrue statement of a material fact or omit
to state a material fact required to be stated therein or necessary to make the
statements therein not misleading in the light of the circumstances then
existing;

                   (g)  Notify the Holders promptly after it shall receive
notice thereof, of the date and time any registration statement and each
post-effective amendment thereto has become effective or a supplement to any
prospectus forming a part of such registration statement has been filed;

                   (h)  Notify the Holders promptly of any request by the
Commission for the amending or supplementing of such registration statement or
prospectus or for additional information; and

                                      -13-
<PAGE>

                   (i)  Advise the Holders promptly after it shall receive
notice or obtain knowledge thereof, of the issuance of any stop order by the
Commisson suspending the effectiveness of any registration statement or the
initiation or threatening of any proceeding for that purpose and promptly use
commercially reasonable efforts to prevent the issuance of any stop order or to
obtain its withdrawal if such stop order should be issued.

         3.4       EXPENSES OF REGISTRATION. All Registration Expenses incurred
in connection with all registrations pursuant to this Section 3 shall be borne
by SuperGen. Unless otherwise stated, all Selling Expenses relating to
securities registered on behalf of any holders of securities participating in
the distribution and all other Registration Expenses shall be borne by such
holders pro rata on the basis of the number of shares so registered.

         3.5       INDEMNIFICATION.

                   (a)  SuperGen will indemnify each Holder, each of its
officers and directors, and each person controlling such Holder within the
meaning of Section 15 of the Securities Act, with respect to which registration,
qualification or compliance has been effected pursuant to this Section 3, and
each underwriter, if any, and each person who controls any underwriter within
the meaning of Section 15 of the Securities Act, against all expenses, claims,
losses, damages or liabilities (or actions in respect thereof), including any of
the foregoing incurred in settlement of any litigation, commenced or threatened,
arising out of or based on any untrue statement (or alleged untrue statement) of
a material fact contained in any registration statement, prospectus, offering
circular or other document, or any amendment or supplement thereto, incident to
any such registration, qualification or compliance, or based on any omission (or
alleged omission) to state therein a material fact required to be stated therein
or necessary to make the statements therein, in light of the circumstances in
which they were made, not misleading, or any violation by SuperGen of the
Securities Act, the Exchange Act, state securities law or any rule or regulation
promulgated under such laws applicable to SuperGen in connection with any such
registration, qualification or compliance, and within a reasonable period
SuperGen will reimburse each Holder, each of its officers and directors, and
each person controlling such Holder, each such underwriter and each person who
controls any such underwriter, for any legal and any other expenses reasonably
incurred in connection with investigating, preparing or defending any such
claim, loss, damage, liability or action; provided that SuperGen will not be
liable in any such case to the extent that any such claim, loss, damage,
liability or expense arises out of or is based on any untrue statement or
omission or alleged untrue statement or omission, made in reliance upon and in
conformity with written information furnished to SuperGen by an instrument duly
executed by such Holder, such controlling person or underwriter and stated to be
specifically for use therein.

                   (b)  Each Holder will indemnify SuperGen, each of its
directors and officers, each underwriter, if any, of SuperGen's securities
covered by such a registration statement, each person who controls SuperGen or
such underwriter within the meaning of Section 15 of the Securities Act, and
each other Holder of securities participating in the distribution, each of its
officers and directors and each person controlling such other Holder within the
meaning of Section 15 of the Securities Act, against all claims, losses, damages
and liabilities (or actions in respect thereof) arising out of or based on any
untrue statement (or alleged untrue statement) of a material fact contained in
any such registration statement, prospectus, offering circular or other
document, or any omission (or alleged

                                      -14-
<PAGE>

omission) to state therein a material fact required to be stated therein or
necessary to make the statements therein not misleading, and within a reasonable
period will reimburse SuperGen, such other Holders, such directors, officers,
persons, underwriters or control persons for any legal or any other expenses
reasonably incurred in connection with investigating or defending any such
claim, loss, damage, liability or action, in each case to the extent, but only
to the extent, that such untrue statement (or alleged untrue statement) or
omission (or alleged omission) is made in such registration statement,
prospectus, offering circular or other document in reliance upon and in
conformity with written information furnished to SuperGen by an instrument duly
executed by such Holder and stated to be specifically for use therein.
Notwithstanding the foregoing, the liability of each Holder under this
subsection (b) shall be limited in an amount equal to the gross proceeds before
expenses and commissions to each Holder received for the shares sold by such
Holder, unless such liability arises out of or is based on willful misconduct by
such Holder.

                   (c)  Each party entitled to indemnification under this
Section 3.5 (the "Indemnified Party") shall give notice to the party required to
provide indemnification (the "Indemnifying Party") promptly after such
Indemnified Party has actual knowledge of any claim as to which indemnity may be
sought, and shall permit the Indemnifying Party to assume the defense of any
such claim or any litigation resulting therefrom, provided that counsel for the
Indemnifying Party, who shall conduct the defense of such claim or litigation,
shall be approved by the Indemnified Party (whose approval shall not
unreasonably be withheld), and the Indemnified Party may participate in such
defense at such party's expense, and provided further that the failure of any
Indemnified Party to give notice as provided herein shall not relieve the
Indemnifying Party of its obligations under this Section 3.5 unless the failure
to give such notice is materially prejudicial to an Indemnifying Party's ability
to defend such action and provided further, that the Indemnifying Party shall
not assume the defense for matters as to which there is a conflict of interest
or separate and different defenses. No Indemnifying Party, in the defense of any
such claim or litigation, shall, except with the consent of each Indemnified
Party, consent to entry of any judgment or enter into any settlement which does
not include as an unconditional term thereof the giving by the claimant or
plaintiff to such Indemnified Party of a release from all liability in respect
to such claim or litigation.

         3.6       INFORMATION BY THE HOLDER. Each Holder shall furnish to
SuperGen such information regarding such Holder, the Registrable Securities held
by it and the distribution proposed by such Holder as SuperGen may request in
writing and as shall be required in connection with any registration,
qualification or compliance referred to in this Section 3.

         3.7       RULE 144 REPORTING. With a view to making available the
benefits of certain rules and regulations of the Commission which may at any
time permit the sale of the Restricted Securities to the public without
registration, SuperGen agrees to use its best efforts to:

                   (a)  Make and keep public information available, as those
terms are understood and defined in Rule 144 under the Securities Act, at all
times;

                   (b)  Use its best efforts to file with the Commission in a
timely manner all reports and other documents required of SuperGen under the
Securities Act and the Exchange Act; and

                   (c)  So long as a Holder owns any SuperGen Shares or
Additional SuperGen Shares which are Restricted Securities furnish to such
Holder forthwith upon request a written

                                      -15-
<PAGE>

statement by SuperGen as to its compliance with the reporting requirements of
said Rule 144 and of the Securities Act and the Exchange Act, a copy of the most
recent annual or quarterly report of SuperGen, and such other reports and
documents of SuperGen and other information in the possession of or reasonably
obtainable by SuperGen as the Holder may reasonably request in availing itself
of any rule or regulation of the Commission allowing such Holder to sell any
such securities without registration.

         3.8       TRANSFER OF REGISTRATION RIGHTS. The rights to cause SuperGen
to register securities granted to a Holder under Sections 3.1 and 3.2 may be
assigned to a transferee or assignee reasonably acceptable to SuperGen which
acquires at least 100,000 shares of SuperGen Shares or Additional SuperGen
Shares in connection with any transfer or assignment of SuperGen Shares or
Additional SuperGen Shares by the Holder.

         3.9       STANDOFF AGREEMENT. In connection with any public offering of
SuperGen's securities, each Holder agrees, upon request of SuperGen or the
underwriters managing any underwritten offering of SuperGen's securities, not to
sell, make any short sale of, loan, grant any option for the purchase of, or
otherwise dispose of any SuperGen Shares or Additional SuperGen Shares (other
than those included in the registration) without the prior written consent of
SuperGen or such underwriters, as the case may be, for such period of time (not
to exceed ninety (90) days) from the effective date of such registration as may
be requested by the underwriters, provided that the officers and directors of
SuperGen who own stock of SuperGen and each holder representing at least 1%
ownership of SuperGen's outstanding Common Stock also agrees to such
restrictions.

         3.10      TERMINATION OF REGISTRATION RIGHTS. The registration rights
granted pursuant to Section 3 shall terminate as to each Holder at such time as
all SuperGen Shares or Additional SuperGen Shares held by such Holder may, in
the opinion of counsel to SuperGen (which opinion shall be addressed and
rendered to the Holder), be sold in a single three month period pursuant to Rule
144.

                                      -16-
<PAGE>

                                    SECTION 4

                                  MISCELLANEOUS

         4.1       GOVERNING LAW. This Agreement shall be governed in all
respects by the internal laws of the State of Delaware.

         4.2       SURVIVAL. The covenants and agreements made herein shall
survive the closing of the transactions contemplated hereby.

         4.3       SUCCESSORS AND ASSIGNS. Except as otherwise provided herein,
the provisions hereof shall inure to the benefit of, and be binding upon, the
successors, assigns, heirs, executors and administrators of the parties hereto.

         4.4       ENTIRE AGREEMENT; AMENDMENT. This Agreement, the Purchase
Agreement, the United States of America Sales, Distribution and Development
Agreement and all exhibits hereto and thereto constitute the full and entire
understanding and agreement between the parties with regard to the subjects
hereof and thereof, and no party shall be liable or bound to any other party in
any manner by any warranties, representations or covenants except as
specifically set forth herein or therein. Except as expressly provided herein,
neither this Agreement nor any term hereof may be amended, waived, discharged or
terminated other than by a written instrument signed by the party against whom
enforcement of any such amendment, waiver, discharge or termination is sought.

         4.5       NOTICES, ETC. All notices and other communications required
or permitted hereunder shall be in writing and shall be mailed by registered or
certified mail, postage prepaid, or otherwise delivered by hand or by messenger,
addressed (a) if to AVI, at AVI BioPharma, Inc., One SW Columbia, Portland, OR
97258, Attn: President, Alan P. Timmins, with a copy to Alter Wynne LLC, 222 SW
Columbia, #1700, Portland, Oregon 97201, Attn: Byron Milstead, or to such other
address (including electronic mail address) as AVI shall have furnished to
SuperGen in writing or by electronic mail, or (b) if to SuperGen, at SuperGen,
Inc., Two Annabel Lane, Suite 220, San Ramon, CA 94583, Attn: President and CEO,
Dr. Joseph Rubinfeld, with a copy of any said notice to Wilson Sonsini Goodrich
& Rosati, 650 Page Mill Road, Palo Alto, CA 94304-1050, Attn: Page Mailliard,
Esq., or to such other address (including electronic mail address) as SuperGen
shall have furnished to AVI in writing or by electronic mail.

         Each such notice or other communication shall for all purposes of this
Agreement be treated as effective or having been given when delivered if
delivered personally, or, if sent by mail, at the earlier of its receipt or 72
hours after the same has been deposited in a regularly maintained receptacle for
the deposit of the United States mail, addressed and mailed as aforesaid.

         4.6       DELAYS OR OMISSIONS. Except as expressly provided herein, no
delay or omission to exercise any right, power or remedy accruing to any party
to this Agreement upon any breach or default of any other party under this
Agreement, shall impair any such right, power or remedy of such nondefaulting
party nor shall it be construed to be a waiver of any such breach or default, or
an acquiescence therein, or of or in any similar breach or default thereafter
occurring; nor shall any waiver of any single breach or default be deemed a
waiver of any other breach or default theretofore or thereafter occurring. Any
waiver, permit, consent or approval of any kind or character on the part

                                      -17-
<PAGE>

of any party of any breach or default under this Agreement, or any waiver on the
part of any holder of any provisions or conditions of this Agreement, must be in
writing and shall be effective only to the extent specifically set forth in such
writing. All remedies, either under this Agreement or by law or otherwise
afforded to any party to this Agreement, shall be cumulative and not
alternative.

         4.7       COUNTERPARTS. This Agreement may be executed in any number of
counterparts, each of which shall be enforceable against the parties actually
executing such counterparts, and all of which together shall constitute one
instrument.

         4.8       SEVERABILITY. In the event that any provision of this
Agreement becomes or is declared by a court of competent jurisdiction to be
illegal, unenforceable or void, this Agreement shall continue in full force and
effect without said provision; provided that no such severability shall be
effective if it materially changes the economic benefit of this Agreement to any
party.

         4.9       TITLES AND SUBTITLES. The titles and subtitles used in this
Agreement are used for convenience only and are not considered in construing or
interpreting this Agreement.

                          [SIGNATURE PAGE(S) FOLLOW(S)]

                                      -18-
<PAGE>

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

                                      SUPERGEN, INC.
                                      a Delaware Corporation

                                      By: /s/ Joseph Rubinfeld
                                          ---------------------------
                                          Joseph Rubinfeld
                                          Chief Executive Officer and President

                                      AVI BIOPHARMA, INC.
                                      an Oregon Corporation

                                      By: /s/ Alan P. Timmins
                                          ---------------------------
                                          Alan P. Timmins
                                          President & Chief Operating Officer

                [SIGNATURE PAGE TO REGISTRATION RIGHTS AGREEMENT]

                                      -19-<PAGE>

                                                                  EXHIBIT 4.6

                          REGISTRATION RIGHTS AGREEMENT

                  This Registration Rights Agreement (the "Agreement") is made
and entered into as of this 27th day of September, 2000 by and between Supergen,
Inc., a Delaware corporation (the "Company"), and the "Seller" named in that
ASSET PURCHASE AGREEMENT of February 18, 2000 by and between the Company and the
Seller (the "Purchase Agreement").

                  The parties hereby agree as follows:

                  1.   CERTAIN DEFINITIONS.

                  As used in this Agreement, the following terms shall have the
following meanings:

                  "COMMON STOCK" shall mean the Company's Common Stock, par
value $0.001 per share.

                  "SELLER" shall mean AMUR Pharmaceuticals, Inc. and any
affiliate or transferee of Seller who is a subsequent holder of any Warrants or
Registrable Securities [pursuant to the terms of the Purchase Agreement and the
Warrants ("permitted transferee")].

                  "PROSPECTUS" shall mean the prospectus included in any
Registration Statement, as amended or supplemented by any prospectus supplement,
with respect to the terms of the offering of any portion of the Registrable
Securities covered by such Registration Statement and by all other amendments
and supplements to the prospectus, including post-effective amendments and all
material incorporated by reference in such prospectus.

                  "REGISTER," "REGISTERED" and "REGISTRATION" refer to a
registration made by preparing and filing a registration statement or similar
document in compliance with the 1933 Act (as defined below), and the declaration
or ordering of effectiveness of such registration statement or document.

                  "REGISTRABLE SECURITIES" shall mean the shares of Common Stock
issued to the Seller and issuable to the Seller upon exercise of the Warrants,
all pursuant to the Purchase Agreement, and any other securities issued or
issuable with respect to or in exchange for Registrable Securities, provided,
however, that shares of Common Stock, or other securities shall only be treated
as Registrable Securities if and so long as they have not been (A) sold to or
through a broker or dealer or underwriter in a public distribution or a public
securities transaction, whether in a registered offering, Rule 144 or otherwise,
or (B) sold or are, in the opinion of counsel for the Company, available for
sale in a single transaction exempt from the registration and prospectus
delivery requirements of the 1933 Act pursuant to Rule 144(k) so that all
transfer restrictions and restrictive legends with respect thereto are removed
upon the consummation of such sale.

<PAGE>

                  "REGISTRATION STATEMENT" shall mean any registration statement
filed under the 1933 Act of the Company that covers the resale of any of the
Registrable Securities pursuant to the provisions of this Agreement, amendments
and supplements to such Registration Statement, including post-effective
amendments, all exhibits and all material incorporated by reference in such
Registration Statement.

                  "SEC" means the U.S. Securities and Exchange Commission.

                  "1933 ACT" means the Securities Act of 1933, as amended, and
the rules and regulations promulgated thereunder.

                  "1934 ACT" means the Securities Exchange Act of 1934, as
amended, and the rules and regulations promulgated thereunder.

                  "WARRANTS" mean the warrants to purchase shares of Common
Stock issued to the Seller pursuant to the Purchase Agreement, the form of which
is attached to the Purchase Agreement as Exhibit 2.2.

                  2.   REGISTRATION.

                       (a)   REGISTRATION STATEMENTS.

                             (i)   REGISTRABLE SECURITIES. Promptly following
the closing of the purchase and sale of Common Stock and issuance of Warrants
contemplated by the Purchase Agreement (the "Closing Date") (but no later than
forty-five (45) days after the Closing Date), the Company shall prepare and file
with the SEC one Registration Statement on Form S-3 (or, if Form S-3 is not then
available to the Company, on such form of registration statement as is then
available to effect a registration for resale of the Registrable Securities,
subject to the Seller's consent) covering the resale of the Registrable
Securities in an amount equal to the number of shares of Common Stock issued to
the Seller on the Closing Date plus the number of shares of Common Stock
necessary to permit the exercise in full of the Warrants. Such Registration
Statement also shall cover, to the extent allowable under the 1933 Act and the
Rules promulgated thereunder (including Rule 416), such indeterminate number of
additional shares of Common Stock resulting from stock splits, stock dividends
or similar transactions with respect to the Registrable Securities. The
Registration Statement (and each amendment or supplement thereto, and each
request for acceleration of effectiveness thereof) shall be provided in
accordance with Section 3(c) to the Seller prior to its filing or other
submission.

                       (b)   EXPENSES. The Company will pay all expenses
associated with each registration, including the Seller's reasonable expenses in
connection with the registration but excluding discounts, commissions, fees of
underwriters, selling brokers, dealer managers or similar securities industry
professionals.

                       (c)   EFFECTIVENESS.

                                       2
<PAGE>

                             (i)   The Company shall use its best efforts to
have each Registration Statement declared effective as soon as practicable.

                             (ii)  For not more than twenty-five (25)
consecutive trading days or for a total of not more than thirty-five (35)
trading days in any twelve (12) month period, the Company may delay the
disclosure of material non-public information concerning the Company, by
terminating or suspending effectiveness of any registration contemplated by this
Section containing such information, the disclosure of which at the time is not,
in the good faith opinion of the Company, in the best interests of the Company
(an "Allowed Delay"); provided, that the Company shall promptly (a) notify the
Seller in writing of the existence of (but in no event, without the prior
written consent of the Seller, shall the Company disclose to such Seller any of
the facts or circumstances regarding) material non-public information giving
rise to an Allowed Delay, and (b) advise the Seller in writing to cease all
sales under the Registration Statement until the end of the Allowed Delay.

                        (d)   UNDERWRITTEN OFFERING. If any offering by the
Seller pursuant to a Registration Statement pursuant to Section 2(a) hereof
involves a firm commitment underwritten offering, the Company shall have the
right to select an investment banker and manager to administer the offering,
which investment banker or manager shall be reasonably satisfactory to the
Seller.

                  3.    COMPANY OBLIGATIONS. The Company will use its best
efforts to effect the registration of the Registrable Securities in accordance
with the terms hereof, and pursuant thereto the Company will, as expeditiously
as possible:

                        (a)   use its best efforts to cause such Registration
Statement to become effective and to remain continuously effective for a period
that will terminate upon the earlier of the date on which all Registrable
Securities covered by such Registration Statement, as amended from time to time,
have been sold (the "Registration Period");

                        (b)   prepare and file with the SEC such amendments and
post-effective amendments to the Registration Statement and the Prospectus as
may be necessary to keep the Registration Statement effective for the period
specified in Section 3(a) and to comply with the provisions of the 1933 Act and
the 1934 Act with respect to the distribution of all Registrable Securities;
provided that, at least five (5) business days prior to the filing of a
Registration Statement or Prospectus, or any amendments or supplements thereto,
the Company will furnish to the Seller copies of all documents proposed to be
filed, which documents will be subject to the comments of the Seller;

                        (c)   furnish to the Seller and their legal counsel (i)
promptly after the same is prepared and publicly distributed, filed with the
SEC, or received by the Company, one copy of any Registration Statement and any
amendment thereto, each preliminary prospectus and Prospectus and each amendment
or supplement thereto, and each letter written by or on behalf of the Company to
the SEC or the staff of the SEC, and each item of correspondence from the SEC or
the staff of the SEC, in each case relating to such Registration Statement
(other than any portion of any thereof which contains information for which the
Company has sought

                                       3
<PAGE>

confidential treatment), and (ii) such number of copies of a Prospectus,
including a preliminary prospectus, and all amendments and supplements thereto
and such other documents as each Seller may reasonably request in order to
facilitate the disposition of the Registrable Securities owned by such Seller;

                        (d)   in the event the Company selects an underwriter
for the offering, the Company shall enter into and perform its reasonable
obligations under an underwriting agreement, in usual and customary form,
including, without limitation, customary indemnification and contribution
obligations, with the underwriter of such offering;

                        (e)   if required by the underwriter, or if any Seller
is described in the Registration Statement as an underwriter, the Company shall
furnish, on the effective date of the Registration Statement, on the date that
Registrable Securities are delivered to an underwriter for sale in connection
with the Registration Statement and at periodic intervals thereafter from time
to time on request, (i) an opinion, dated as of such date, from independent
legal counsel representing the Company for purposes of such Registration
Statement, in form, scope and substance as is customarily given in an
underwritten public offering, addressed to the underwriter and the Seller and
(ii) a letter, dated such date, from the Company's independent certified public
accountants in form and substance as is customarily given by independent
certified public accountants to underwriters in an underwritten public offering,
addressed to the underwriter and the Seller;

                        (f)   make effort to prevent the issuance of any stop
order or other suspension of effectiveness and, if such order is issued, obtain
the withdrawal of any such order at the earliest possible moment;

                        (g)   furnish to each Seller at least five (5) copies of
the Registration Statement and any post-effective amendment thereto, including
financial statements and schedules;

                        (h)   prior to any public offering of Registrable
Securities, use its reasonable best efforts to register or qualify or cooperate
with the Seller and their counsel in connection with the registration or
qualification of such Registrable Securities for offer and sale under the
securities or blue sky laws of all United States jurisdictions and do any and
all other reasonable acts or things necessary or advisable to enable the
distribution in such jurisdictions of the Registrable Securities covered by the
Registration Statement;

                        (i)   use its reasonable best efforts to maintain its
listing on each securities exchange, interdealer quotation system or other
market on which similar securities issued by the Company are then listed;

                        (j)   immediately notify the Seller, at any time when a
Prospectus relating to the Registrable Securities is required to be delivered
under the Securities Act, upon discovery that, or upon the happening of any
event as a result of which, the Prospectus included in such Registration
Statement, as then in effect, includes an untrue statement of a material fact or
omits to state any material fact required to be stated therein or necessary to
make the

                                       4
<PAGE>

statements therein not misleading in the light of the circumstances then
existing, and at the request of any such holder, promptly prepare and furnish to
such holder a reasonable number of copies of a supplement to or an amendment of
such Prospectus as may be necessary so that, as thereafter delivered to the
purchasers of such Registrable Securities such Prospectus shall not include an
untrue statement of a material fact or omit to state a material fact required to
be stated therein or necessary to make the statements therein not misleading in
the light of the circumstances then existing; and

                        (k)   otherwise use its best efforts to comply with all
applicable rules and regulations of the SEC under the 1933 Act and the 1934 Act,
take such other actions as may be reasonably necessary to facilitate the
registration of the Registrable Securities.

                   4.   DUE DILIGENCE REVIEW. The Company shall make available,
during normal business hours, for inspection and review by the Seller, advisors
to and representatives of the Seller (who may or may not be affiliated with the
Seller and who are reasonably acceptable to the Company), any underwriter
participating in any disposition of Common Stock on behalf of the Seller
pursuant to the Registration Statement or amendments or supplements thereto or
any blue sky, NASD or other filing, all SEC Documents and other filings with the
SEC as may be reasonably necessary for the purpose of such review, and cause the
Company's officers, directors and employees, within a reasonable time period, to
supply all such information reasonably requested by the Seller or any such
representative, advisor or underwriter in connection with such Registration
Statement (including, without limitation, in response to all questions and other
inquiries reasonably made or submitted by any of them), prior to and from time
to time after the filing and effectiveness of the Registration Statement for the
sole purpose of enabling the Seller and such representatives, advisors and
underwriters and their respective accountants and attorneys to conduct initial
and ongoing due diligence with respect to the Company and the accuracy of the
Registration Statement.

                  The Company shall not disclose nonpublic information to the
Seller, advisors to or representatives of the Seller unless prior to disclosure
of such information the Company identifies such information as being nonpublic
information and provides the Seller, such advisors and representatives with the
opportunity to accept or refuse to accept such nonpublic information for review.
The Company may, as a condition to disclosing any nonpublic information
hereunder, require the Seller, their advisors and representatives to enter into
a confidentiality agreement (including an agreement with such advisors and
representatives prohibiting them from trading in Common Stock during such period
of time as they are in possession of nonpublic information) in form reasonably
satisfactory to the Company and the Seller.

                  Nothing herein shall require the Company to disclose nonpublic
information to the Seller or their advisors or representatives, and the Company
represents that it does not disseminate nonpublic information to any Seller who
purchase stock in the Company in a public offering, to money managers or to
securities analysts, provided, however, that notwithstanding anything herein to
the contrary, the Company will, as hereinabove provided, immediately notify the
advisors and representatives of the Seller and underwriters, of any event or the
existence of any circumstance (without any obligation to disclose the specific
event or circumstance) of

                                       5
<PAGE>

which it becomes aware, constituting nonpublic information (whether or not
requested of the Company specifically or generally during the course of due
diligence by and such persons or entities), which, if not disclosed in the
Prospectus included in the Registration Statement, would cause such Prospectus
to include a material misstatement or to omit a material fact required to be
stated therein in order to make the statements therein, in light of the
circumstances in which they were made, not misleading. Nothing contained in this
Section 4 shall be construed to mean that such persons or entities other than
the Seller (without the written consent of the Seller prior to disclosure of
such information) may not obtain nonpublic information in the course of
conducting due diligence in accordance with the terms of this Agreement and the
Purchase Agreement; provided, however, that in no event shall the Seller's
advisors or representatives disclose to the Seller the nature of the specific
event or circumstances constituting any nonpublic information discovered by such
advisors or representatives in the course of their due diligence without the
written consent of the Seller prior to disclosure of such information. The
Seller' advisors or representatives shall make complete disclosure to the
Seller' independent counsel of all events or circumstances constituting
nonpublic information discovered by such advisors or representatives in the
course of their due diligence upon which such advisors or representatives form
the opinion that the Registration Statement contains an untrue statement of a
material fact or omits a material fact required to be stated in the Registration
Statement or necessary to make the statements contained therein, in the light of
the circumstances in which they were made, not misleading. Upon receipt of such
disclosure, the Seller's independent counsel shall consult with the Company's
independent counsel in order to address the concern raised as to the existence
of a material misstatement or omission and to discuss appropriate disclosure
with respect thereto; provided, however, that such consultation shall not
constitute the advice of the Company's independent counsel to the Seller as to
the accuracy of the Registration Statement and related Prospectus. In the event
after such consultation the Seller' independent counsel reasonably believes that
the Registration Statement contains an untrue statement or a material fact or
omits a material fact required to be stated in the Registration Statement or
necessary to make the statements contained therein, in light of the
circumstances in which they were made, not misleading, (a) the Company shall
file with the SEC an amendment to the Registration Statement responsive to such
alleged untrue statement or omission and provide the Seller, as promptly as
practicable, with copies of the Registration Statement and related Prospectus,
as so amended, or (b) if the Company disputes the existence of any such material
misstatement or omission, (i) the Company's independent counsel shall provide
the Seller's independent counsel with an opinion stating that nothing has come
to their attention that would lead them to believe that the Registration
Statement or the related Prospectus, as of the date of such opinion, contains an
untrue statement of a material fact or omits a material fact required to be
stated in the Registration Statement or the related Prospectus or necessary to
make the statements contained therein, in light of the circumstances in which
they were made, not misleading and (ii) in the event the dispute relates to the
adequacy of financial disclosure and the Seller shall reasonably request, the
Company's independent auditors shall provide to the Company a letter outlining
the performance of such "agreed upon procedures" as shall be reasonably
requested by the Seller and the Company shall provide the Seller with a copy of
such letter.

                                       6
<PAGE>

                   5.   OBLIGATIONS OF THE SELLER.

                        (a)   Each Seller shall furnish in writing to the
Company such information regarding itself, the Registrable Securities held by it
and the intended method of disposition of the Registrable Securities held by it,
as shall be reasonably required to effect the registration of such Registrable
Securities and shall execute such documents in connection with such registration
as the Company may reasonably request. At least fifteen (15) business days prior
to the first anticipated filing date of any Registration Statement, the Company
shall notify each Seller of the information the Company requires from such
Seller if such Seller elects to have any of the Registrable Securities included
in the Registration Statement. A Seller shall provide such information to the
Company at least seven (7) business days prior to the first anticipated filing
date of such Registration Statement if such Seller elects to have any of the
Registrable Securities included in the Registration Statement.

                        (b)   Each Seller, by its acceptance of the Registrable
Securities agrees to cooperate with the Company as reasonably requested by the
Company in connection with the preparation and filing of a Registration
Statement hereunder, unless such Seller has notified the Company in writing of
its election to exclude all of its Registrable Securities from the Registration
Statement, in which case the Seller shall be deemed to have waived its rights to
have Registrable Securities registered under this Agreement.

                        (c)   In the event the Company at an Seller's request,
determines to engage the services of an underwriter, such Seller agrees to enter
into and perform its obligations under an underwriting agreement, in usual and
customary form, including, without limitation, customary indemnification and
contribution obligations, with the managing underwriter of such offering and
take such other actions as are reasonably required in order to expedite or
facilitate the dispositions of the Registrable Securities.

                        (d)   Each Seller agrees that, upon receipt of any
notice from the Company of the happening of any event rendering a Registration
Statement no longer effective, such Seller will immediately discontinue
disposition of Registrable Securities pursuant to the Registration Statement
covering such Registrable Securities until the Seller's receipt of the copies of
the supplemented or amended prospectus filed with the SEC and declared effective
and, if so directed by the Company, the Seller shall deliver to the Company (at
the expense of the Company) or destroy (and deliver to the Company a certificate
of destruction) all copies in the Seller's possession of the prospectus covering
the Registrable Securities current at the time of receipt of such notice.

                        (e)   No Seller may participate in any third party
underwritten registration hereunder unless it (i) agrees to sell the Registrable
Securities on the basis provided in any underwriting arrangements in usual and
customary form entered into by the Company, (ii) completes and executes all
questionnaires, powers of attorney, indemnities, underwriting agreements and
other documents reasonably required under the terms of such underwriting
arrangements, and (iii) agrees to pay its pro rata share of all underwriting
discounts and commissions and any expenses in excess of those payable by the
Company pursuant to the terms of this Agreement.

                                       7
<PAGE>

                   6.   INDEMNIFICATION.

                        (a)   INDEMNIFICATION BY COMPANY. The Company agrees to
indemnify and hold harmless, to the fullest extent permitted by law the Seller,
each of its officers, directors, partners and employees and each person who
controls the Seller (within the meaning of the 1933 Act) against all losses,
claims, damages, liabilities, costs (including, without limitation, reasonable
attorney's fees) and expenses imposed on such person caused by (i) any untrue or
alleged untrue statement of a material fact contained in any Registration
Statement, Prospectus or any preliminary prospectus or any amendment or
supplement thereto or any omission or alleged omission to state therein a
material fact required to be stated therein or necessary to make the statements
therein not misleading, except insofar as the same are based upon any
information furnished in writing to the Company by such Seller, expressly for
use therein, or (ii) any violation by the Company of any federal, state or
common law, rule or regulation applicable to the Company in connection with any
Registration Statement, Prospectus or any preliminary prospectus, or any
amendment or supplement thereto, and shall reimburse in accordance with
subparagraph (c) below, each of the foregoing persons for any legal and any
other expenses reasonably incurred in connection with investigating or defending
any such claims. The foregoing is subject to the condition that, insofar as the
foregoing indemnities relate to any untrue statement, alleged untrue statement,
omission or alleged omission made in any preliminary prospectus or Prospectus
that is eliminated or remedied in any Prospectus or amendment or supplement
thereto, the above indemnity obligations of the Company shall not inure to the
benefit of any indemnified party if a copy of such corrected Prospectus or
amendment or supplement thereto had been made available to such indemnified
party and was not sent or given by such indemnified party at or prior to the
time such action was required of such indemnified party by the 1933 Act and if
delivery of such Prospectus or amendment or supplement thereto would have
eliminated (or been a sufficient defense to) any liability of such indemnified
party with respect to such statement or omission. Indemnity under this Section
6(a) shall remain in full force and effect regardless of any investigation made
by or on behalf of any indemnified party and shall survive the permitted
transfer of the Registrable Securities.

                        (b)   INDEMNIFICATION BY HOLDER. In connection with any
registration pursuant to the terms of this Agreement, each Seller will furnish
to the Company in writing such information as the Company reasonably requests
concerning the holders of Registrable Securities or the proposed manner of
distribution for use in connection with any Registration Statement or Prospectus
and agrees, severally but not jointly, to indemnify and hold harmless, to the
fullest extent permitted by law, the Company, its directors, officers,
employees, stockholders and each person who controls the Company (within the
meaning of the 1933 Act) against any losses, claims, damages, liabilities and
expense (including reasonable attorney's fees) resulting from any untrue
statement or alleged untrue statement of a material fact or any omission or
alleged omission of a material fact required to be stated in the Registration
Statement or Prospectus or preliminary prospectus or amendment or supplement
thereto or necessary to make the statements therein not misleading, to the
extent, but only to the extent that such untrue statement or omission is
contained in any information furnished in writing by such Seller to the Company
specifically for inclusion in such Registration Statement or Prospectus or
amendment or supplement thereto and that such information was substantially
relied upon by the Company in

                                       8
<PAGE>

preparation of the Registration Statement or Prospectus or any amendment or
supplement thereto. In no event shall the liability of an Seller be greater in
amount than the dollar amount of the proceeds (net of all the amount of any
damages such holder has otherwise been required to pay by reason of such untrue
statement or omission) received by such Seller upon the sale of the Registrable
Securities included in the Registration Statement giving rise to such
indemnification obligation.

                        (c)   CONDUCT OF INDEMNIFICATION PROCEEDINGS. Any person
entitled to indemnification hereunder shall (i) give prompt notice to the
indemnifying party of any claim with respect to which it seeks indemnification
and (ii) permit such indemnifying party to assume the defense of such claim with
counsel reasonably satisfactory to the indemnified party; PROVIDED that any
person entitled to indemnification hereunder shall have the right to employ
separate counsel and to participate in the defense of such claim, but the fees
and expenses of such counsel shall be at the expense of such person unless (a)
the indemnifying party has agreed to pay such fees or expenses, or (b) the
indemnifying party shall have failed to assume the defense of such claim and
employ counsel reasonably satisfactory to such person or (c) in the reasonable
judgment of any such person, based upon written advice of its counsel, a
conflict of interest exists between such person and the indemnifying party with
respect to such claims (in which case, if the person notifies the indemnifying
party in writing that such person elects to employ separate counsel at the
expense of the indemnifying party, the indemnifying party shall not have the
right to assume the defense of such claim on behalf of such person); and
PROVIDED, FURTHER, that the failure of any indemnified party to give notice as
provided herein shall not relieve the indemnifying party of its obligations
hereunder, except to the extent that such failure to give notice shall
materially adversely affect the indemnifying party in the defense of any such
claim or litigation. It is understood that the indemnifying party shall not, in
connection with any proceeding in the same jurisdiction, be liable for fees or
expenses of more than one separate firm of attorneys at any time for all such
indemnified parties. No indemnifying party will, except with the consent of the
indemnified party, consent to entry of any judgment or enter into any settlement
that does not include as an unconditional term thereof the giving by the
claimant or plaintiff to such indemnified party of a release from all liability
in respect of such claim or litigation.

                        (d)   CONTRIBUTION. If for any reason the
indemnification provided for in the preceding paragraphs (a) and (b) is
unavailable to an indemnified party or insufficient to hold it harmless, other
than as expressly specified therein, then the indemnifying party shall
contribute to the amount paid or payable by the indemnified party as a result of
such loss, claim, damage or liability in such proportion as is appropriate to
reflect the relative fault of the indemnified party and the indemnifying party,
as well as any other relevant equitable considerations. No person guilty of
fraudulent misrepresentation within the meaning of Section 11(f) of the 1933 Act
shall be entitled to contribution from any person not guilty of such fraudulent
misrepresentation. In no event shall the contribution obligation of a holder of
Registrable Securities be greater in amount than the dollar amount of the
proceeds (net of the amount of any damages such holder has otherwise been
required to pay by reason of such untrue or alleged untrue statement or omission
or alleged omission) received by it upon the sale of the Registrable Securities
giving rise to such contribution obligation.

                                       9
<PAGE>

                   7.   MISCELLANEOUS.

                        (a)   AMENDMENTS AND WAIVERS. This Agreement may be
amended only by a writing signed by the Company and the holders of a majority of
the Registrable Securities. The Company may take any action herein prohibited,
or omit to perform any act herein required to be performed by it, only if the
Company shall have obtained the written consent to such amendment, action or
omission to act, of each Seller.

                        (b)   NOTICES. All notices and other communications
provided for or permitted hereunder shall be made as set forth below:

                        To the Seller:
                        Ms. Sandi Yurichuk
                        President
                        AMUR Pharmaceuticals, Inc.
                        227 Lyndhurst Ave.
                        Belmont, CA   94002

                        To the Company:
                        Dr. Joseph Rubinfeld
                        President
                        SuperGen, Inc.
                        Two Annabel Lane
                        Suite 220
                        San Ramon, CA  94583

                        (c)   ASSIGNMENTS AND TRANSFERS BY SELLER. This
Agreement and all the rights and obligations of the Seller hereunder may not be
assigned or transferred to any transferee or assignee except to an affiliate or
permitted transferee of a Seller who is a subsequent holder of any Registrable
Securities, provided that such affiliate or permitted transferee holds at least
25,000 Registrable Securities upon completion of such assignment or transfer.

                        (d)   ASSIGNMENTS AND TRANSFERS BY THE COMPANY. This
Agreement may not be assigned by the Company without the prior written consent
of each Seller, except that without the prior written consent of the Seller, but
after notice duly given, the Company shall assign its rights and delegate its
duties hereunder to any successor-in-interest corporation, and such
successor-in-interest shall assume such rights and duties, in the event of a
merger or consolidation of the Company with or into another corporation or the
sale of all or substantially all of the Company's assets.

                        (e)   BENEFITS OF THE AGREEMENT. The terms and
conditions of this Agreement shall inure to the benefit of and be binding upon
the respective permitted successors and assigns of the parties. Nothing in this
Agreement, express or implied, is intended to confer upon any party other than
the parties hereto or their respective successors and assigns any rights,

                                       10
<PAGE>

remedies, obligations, or liabilities under or by reason of this Agreement,
except as expressly provided in this Agreement.

                        (f)   COUNTERPARTS. This Agreement may be executed in
two or more counterparts, each of which shall be deemed an original, but all of
which together shall constitute one and the same instrument.

                        (g)   TITLES AND SUBTITLES. The titles and subtitles
used in this Agreement are used for convenience only and are not to be
considered in construing or interpreting this Agreement.

                        (h)   SEVERABILITY. If one or more provisions of this
Agreement are held to be unenforceable under applicable law, such provision
shall be excluded from this Agreement and the balance of this Agreement shall be
interpreted as if such provision were so excluded and shall be enforceable in
accordance with its terms to the fullest extent permitted by law.

                        (i)   FURTHER ASSURANCES. The parties shall execute and
deliver all such further instruments and documents and take all such other
actions as may reasonably be required to carry out the transactions contemplated
hereby and to evidence the fulfillment of the agreements herein contained.

                        (j)   ENTIRE AGREEMENT. This Agreement is intended by
the parties as a final expression of their agreement and intended to be a
complete and exclusive statement of the agreement and understanding of the
parties hereto in respect of the subject matter contained herein. This Agreement
supersedes all prior agreements and understandings between the parties with
respect to such subject matter.

                        (k)   APPLICABLE LAW. This Agreement shall be governed
by, and construed in accordance with, the laws of the State of Delaware without
regard to principles of conflicts of law.

                                       11
<PAGE>

                  IN WITNESS WHEREOF, the parties have executed this Agreement
as of the date first written above.

The Company:                                   SUPERGEN, INC.

                                               By: /s/ Joseph Rubinfeld
                                                   --------------------
                                               Name: Joseph Rubinfeld, Ph.D.
                                               Title: President and CEO

The Seller:                                    AMUR PHARMACEUTICALS, INC.

                                               By: /s/ Sandi Yurichuk
                                                   --------------------
                                               Name: Sandi Yurichuk
                                               Title: President

                                       12

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