<PAGE>

                                                                     EXHIBIT 4.3

                  FIRST AMENDED REGISTRATION RIGHTS AGREEMENT
                  -------------------------------------------


          THIS REGISTRATION RIGHTS AGREEMENT (this "Agreement") is entered into
                                                    ---------
as of June 1, 1998 by and among American Pharmaceutical Partners, Inc., a
California corporation (the "Company"), Premier Purchasing Partners, L.P., a
                             -------
California limited partnership ("Premier"), American BioScience Inc., a
                                 -------
California corporation (formerly known as VivoRx Pharmaceutical, Inc.)

("ABS") and the Series A Investors (as defined below).
  ---

                                 R E C I T A L S
                                 - - - - - - - -


          A.  Pursuant to the Stock Purchase Agreement dated October 3, 1996
between the Company and Premier (as amended through the date hereof, the

"Premier Stock Purchase Agreement"), the Company, Premier and ABS entered into a
---------------------------------
Registration Rights Agreement dated as of October 10, 1996 (the "Prior
                                                                 -----
Registration Rights Agreement").
-----------------------------

          B.  The Company and the Series A Investors have entered into a Series
A Preferred Stock Purchase Agreement dated as of January 23, 1998 (the "Series A
                                                                        --------
Stock Purchase Agreement"); the obligation of the Series A Investors to
------------------------
consummate the acquisition of the Series A Preferred Stock under the Series A
Stock Purchase Agreement is conditioned upon ABS entering into this Agreement.

          B.  The Company and ABS have entered into a Series B/D Preferred Stock
Purchase Agreement dated as of May 29, 1998 (the "Series B/D Stock Purchase
                                                  -------------------------
Agreement"); the obligation of ABS to consummate the acquisition of the Series B
---------
and Series D  Preferred Stock under the Series B/D Stock Purchase Agreement is
conditioned upon ABS entering into this Agreement.

          D.  The Company, ABS and Premier desire to amend and restate the Prior
Registration Rights Agreement in the manner set forth herein to induce the
Series A Investors to enter into and consummate the transactions contemplated by
the Series A Stock Purchase Agreement.

                                 AGREEMENT
                                 ---------

          NOW, THEREFORE, in consideration of the foregoing recitals and of the
mutual promises herein contained, the parties hereby agree (and the Company, ABS
and Premier agree to amend and restate the Prior Registration Rights Agreement)
as follows:

          1.  Definitions.  Unless the context otherwise requires, the terms
              -----------
defined in this Section 1 shall have the meanings herein specified for all
purposes of this Agreement, applicable to both the singular and plural forms of
any of the terms herein defined.

          "ABS New Securities" shall mean the ABS Series B Securities and the
           ------------------
ABS Series D Securities, collectively.

          "ABS Prior Securities" means (i) the shares of Common Stock owned by
           --------------------
ABS as
<PAGE>

of the date hereof and (ii) any Common Stock issued or issuable with respect to
the Common Stock referred to in clause (i) above by way of a stock dividend or
stock split or in connection with a combination of shares, reclassification,
merger or consolidation or reorganization, collectively; provided, however, that
such shares of Common Stock shall only be treated as ABS Prior Securities if and
so long as they have not been (x) sold to or through a broker or dealer or
underwriter in a public distribution or a public securities transaction, or (y)
sold in a transaction exempt from the registration and prospectus delivery
requirements of the Securities Act under Section 4(1) thereof so that all
transfer restrictions and restrictive legends with respect to such Common Stock
are removed upon the consummation of such sale and the seller and purchaser of
such Common Stock receive an opinion of counsel for the Company, which shall be
in form and content reasonably satisfactory to the seller and purchaser and
their respective counsel, to the effect that such Common Stock in the hands of
the purchaser is freely transferable without restriction or registration under
the Securities Act in any public or private transaction.

          "ABS Series B Securities" means (i) the Common Stock issued or
           -----------------------
issuable upon conversion of the Series B Preferred Stock issued and sold to ABS
pursuant to the Series B/D Stock Purchase Agreement and (ii) any Common Stock
issued or issuable with respect to the Common Stock referred to in clause (i)
above by way of a stock dividend or stock split or in connection with a
combination of shares, reclassification, merger or consolidation or
reorganization, collectively; provided, however, that such shares of Common
Stock shall only be treated as ABS Series B Securities if and so long as they
have not been (x) sold to or through a broker or dealer or underwriter in a
public distribution or a public securities transaction, or (y) sold in a
transaction exempt from the registration and prospectus delivery requirements of
the Securities Act under Section 4(1) thereof so that all transfer restrictions
and restrictive legends with respect to such Common Stock are removed upon the
consummation of such sale and the seller and purchaser of such Common Stock
receive an opinion of counsel for the Company, which shall be in form and
content reasonably satisfactory to the seller and purchaser and their respective
counsel, to the effect that such Common Stock in the hands of the purchaser is
freely transferable without restriction or registration under the Securities Act
in any public or private transaction.

          "ABS Series D Securities" means (i) the Common Stock issued or
           -----------------------
issuable upon conversion of the Series D Preferred Stock issued and sold to ABS
pursuant to the Series B/D Stock Purchase Agreement and (ii) any Common Stock
issued or issuable with respect to the Common Stock referred to in clause (i)
above by way of a stock dividend or stock split or in connection with a
combination of shares, reclassification, merger or consolidation or
reorganization, collectively; provided, however, that such shares of Common
Stock shall only be treated as ABS Series D Securities if and so long as they
have not been (x) sold to or through a broker or dealer or underwriter in a
public distribution or a public securities transaction, or (y) sold in a
transaction exempt from the registration and prospectus delivery requirements of
the Securities Act under Section 4(1) thereof so that all transfer restrictions
and restrictive legends with respect to such Common Stock are removed upon the
consummation of such sale and the seller and purchaser of such Common Stock
receive an opinion of counsel for the Company, which shall be in form and
content reasonably satisfactory to the seller and purchaser and their respective
counsel, to the effect that such Common Stock in the hands of the purchaser is
freely transferable without restriction or registration under the Securities Act
in any public or private transaction.
<PAGE>

          "ABS Securities" means the ABS Prior Securities and the ABS New
           --------------
Securities, collectively."Agreement" means this Registration Rights Agreement.
                          ---------

          "Board" means the Board of Directors of the Company.
           -----

          "Common Stock" means the common stock of the Company.
           ------------

          "Commission" means the Securities and Exchange Commission.
           ----------

          "Exchange Act" means the Securities Exchange Act of 1934, as amended.
           ------------

          "Demand Securities" shall mean the ABS Securities, the Premier
           -----------------
Securities and the Series A Investor Securities, collectively.

          "Future Registrable Securities" shall mean all Common Stock owned now
           -----------------------------
or in the future by any employees of, consultant to, or holders of equity
securities, of the Company to whom the Board determines to expressly extend the
benefits of this Agreement; provided, that such Person executes a written
                            --------
agreement to be bound by the terms hereof as if such Person were an original
party hereto; provided, further that such shares of Common Stock shall only be
treated as Future Registrable Securities if and so long as they have not been
(x) sold to or through a broker or dealer or underwriter in a public
distribution or a public securities transaction, or (y) sold in a transaction
exempt from the registration and prospectus delivery requirements of the
Securities Act under Section 4(1) thereof so that all transfer restrictions and
restrictive legends with respect to such Common Stock are removed upon the
consummation of such sale and the seller and purchaser of such Common Stock
receive an opinion of counsel for the Company, which shall be in form and
content reasonably satisfactory to the seller and purchaser and their respective
counsel, to the effect that such Common Stock in the hands of the purchaser is
freely transferable without restriction or registration under the Securities Act
in any public or private transaction.

          "Holder" of any security means the record or beneficial owner of such
           ------
security. A Holder of Preferred Stock shall be deemed for purposes of this
Agreement to be the Holder of the Common Stock then issuable upon conversion of
the Preferred Stock then held thereby.

          "Holders of a Majority of Demand Securities" means the Person or
           ------------------------------------------
Persons who are the Holders of greater than 50% of the shares of Demand
Securities then outstanding.

          "Holders of a Majority of Registrable Securities" means the Person or
           -----------------------------------------------
Persons who are the Holders of greater than 50% of the shares of Registrable
Securities then outstanding.

          "Holders of a Majority of Series A Investor Securities" means the
           -----------------------------------------------------
Person or Persons who are the Holders of greater than 50% of the shares of the
Series A Investor Securities then outstanding.

          "Initiating Holder" means (i) with respect to any registration
           -----------------
effected pursuant to Section 2 hereof, other than a registration on Form S-3,
the Holders of Demand Securities having an anticipated public offering price of
at least $7,500,000 (before deducting underwriting
<PAGE>

discount and commission) and (ii) with respect to any registration effected
pursuant to Section 2 hereof on Form S-3, the Holders of Demand Securities
having an anticipated public offering price of at least $1,000,000 (before
deducting underwriting discount and commission).

          "Investor" has the meaning assigned to it in the introductory
           --------
paragraph of this Agreement.

          "IPO" shall mean the closing of an underwritten public offering of
           ---
Common Stock pursuant to an effective registration statement under the
Securities Act.

          "Person" means any natural person, corporation, trust, association,
           ------
company, partnership, limited liability company, joint venture and other entity
and any government, governmental agency, instrumentality or political
subdivision.

          The terms "register," "registered" and "registration" refer to a
                     ---------   ----------       ------------
registration effected by preparing and filing a registration statement in
substantial compliance with the Securities Act, and the declaration or ordering
of the effectiveness of such registration statement.

          "Premier Securities" means (i) the Common Stock issued to Premier
           ------------------
pursuant to the Premier Stock Purchase Agreement and (ii) any Common Stock
issued or issuable with respect to the Common Stock referred to in clause (i)
above by way of a stock dividend or stock split or in connection with a
combination of shares, reclassification, recapitalization, merger or
consolidation or reorganization; provided, however, that such shares of Common
Stock shall only be treated as Registrable Securities if and so long as they
have not been (x) sold to or through a broker or dealer or underwriter in a
public distribution or a public securities transaction, or (y) sold in a
transaction exempt from the registration and prospectus delivery requirements of
the Securities Act under Section 4(1) thereof so that all transfer restrictions
and restrictive legends with respect to such Common Stock are removed upon the
consummation of such sale and the seller and purchaser of such Common Stock
receive an opinion of counsel for the Company, which shall be in form and
content reasonably satisfactory to the seller and purchaser and their respective
counsel, to the effect that such Common Stock in the hands of the purchaser is
freely transferable without restriction or registration under the Securities Act
in any public or private transaction.

          "Premier Stock Purchase Agreement" shall have the meaning assigned to
           --------------------------------
such term in Recital A above.

          "Registrable Securities" shall mean the ABS Securities, the Premier
           ----------------------
Securities, the Series A Investor Securities and the Future Registrable
Securities, collectively.

          "Securities Act" means the Securities Act of 1933, as amended.
           --------------

          "Series A Stock Purchase Agreement" shall have the meaning assigned to
           ---------------------------------
such term in Recital B above.

          "Series A Investors" shall mean the "investors" named in the Series A
           ------------------
Stock Purchase Agreement.
<PAGE>

          "Series A Investor Securities" means (i) the Common Stock issued or
           ----------------------------
issuable upon conversion of the Series A Preferred Stock issued and sold to the
Series A Investors pursuant to the Series A  Stock Purchase Agreement and (ii)
any Common Stock issued or issuable with respect to the Common Stock referred to
in clause (i) above by way of a stock dividend or stock split or in connection
with a combination of shares, reclassification, recapitalization, merger or
consolidation or reorganization; provided, however, that such shares of Common
Stock shall only be treated as Registrable Securities if and so long as they
have not been (x) sold to or through a broker or dealer or underwriter in a
public distribution or a public securities transaction, or (y) sold in a
transaction exempt from the registration and prospectus delivery requirements of
the Securities Act under Section 4(1) thereof so that all transfer restrictions
and restrictive legends with respect to such Common Stock are removed upon the
consummation of such sale and the seller and purchaser of such Common Stock
receive an opinion of counsel for the Company, which shall be in form and
content reasonably satisfactory to the seller and purchaser and their respective
counsel, to the effect that such Common Stock in the hands of the purchaser is
freely transferable without restriction or registration under the Securities Act
in any public or private transaction.

          "Series B/D Stock Purchase Agreement" shall have the meaning assigned
           -----------------------------------
to such term in Recital C above.

          2.  Demand Registration.
              -------------------

          (a) Commencing on the earlier to occur of (i) the third anniversary of
the date hereof or (ii) six months after the IPO, if and whenever the Company
shall receive a written request therefor from an Initiating Holder, the Company
agrees to prepare and file promptly a registration statement under the
Securities Act covering the shares of Demand Securities which are the subject of
such request and agrees to use its best efforts to cause such registration
statement to become effective as expeditiously as possible.  Upon the receipt of
such request, the Company agrees to give promptly written notice to all Holders
of Demand Securities that such registration is to be effected.  The Company
agrees to include in such registration statement such shares of Demand
Securities for which it has received written requests to register such shares by
the Holders thereof within thirty (30) days after the receipt of written notice
from the Company.  Any registration under this Section 2 shall be on a form
designated by the Company (or, if a managing underwriter is designated pursuant
to subsection (e) below, by such managing underwriter).

          (b) Notwithstanding the foregoing, if the Company is required to
effect a registration pursuant to this Section 2 and the Company furnishes to
the Initiating Holder requesting such registration a certificate signed by the
President of the Company stating that in the good faith judgment of the Board it
would be detrimental to the Company and its shareholders for a registration
statement to be filed on or before the date such filing would otherwise be
required hereunder, the Company shall have the right to defer such filing for an
additional period of not more than 90 days after the expiration of the 30-day
period referred to in subsection (a) above; provided, that the Company may not
                                            --------
exercise its right under this subsection (b) more than once in any 12-month
period.

          (c) Notwithstanding the foregoing, if at the time the Company receives
a request for registration under this Section 2, the Company shall then be in
the process of taking
<PAGE>

action to effect a registered public offering of its securities (other than a
registration statement covering primarily stock issued under an employee benefit
plan) pertaining to an underwritten public offering of securities for the
account of the Company, and files such registration statement within 60 days
after receipt of such request, the Company shall not be obligated to effect a
registration pursuant to this Section 2 within 180 days following the effective
date of such registration statement.

          (d) The Company shall be obligated to prepare, file and cause to
become effective only (i) one registration statement pursuant to this Section 2
(other than on Form S-3, as to which there shall be no limit) if the Initiating
Holder is ABS,(ii) one registration statement pursuant to this Section 2 (other
than on Form S-3, as to which there shall be no limit) if the Initiating Holder
is Premier and (iii) one registration statement pursuant to this Section 2
(other than on Form S-3, as to which there shall be no limit) if the Initiating
Holder is the Series A Investors.

          (e) If the Initiating Holder intends to distribute the Demand
Securities covered by their request by means of an underwriting, they agree to
provide the Company with the name of the managing underwriter or underwriters
(the "managing underwriter") that the Initiating Holder requesting such
registration propose to employ, as a part of their request made pursuant to this
Section 2, and the Company agrees to include such information in its written
notice referred to in Section 2(a); provided, that the selection of the managing
underwriter by the Initiating Holder shall be subject to the reasonable approval
of the Board.  In such event the right of any Holder to registration pursuant to
this Section 2 shall be conditioned upon such Holder's participation in such
underwriting and the inclusion of such Holder's Registrable Securities in the
underwriting to the extent requested (unless otherwise mutually agreed by the
Holders of a Majority of the Registrable Securities initiating such request for
registration and such Holder).  All Holders proposing to distribute their
securities through such underwriting agree to enter into (together with the
Company) an underwriting agreement with the underwriter or underwriters selected
for such underwriting, in the manner set forth above, provided that such
underwriting agreement is in customary form and is reasonably acceptable to the
Holders of a majority of the shares of Registrable Securities to be included in
such registration.

          (f) Notwithstanding the foregoing, if the managing underwriter of an
underwritten distribution advises the Company and the Holders of Registrable
Securities participating in such registration in writing that in its good faith
judgment the number of shares of Registrable Securities requested to be included
in such registration exceeds the number of shares of Registrable Securities
which can be sold in such offering, then (i) the number of shares of Registrable
Securities so requested to be included in such registration shall be reduced to
that number of shares which in the good faith judgment of the managing
underwriter can be sold in such offering and (ii) this reduced number of shares
shall be allocated:

               (A) first, among all Holders of Demand Securities in proportion,
as nearly as practicable, to the respective number of shares of Demand
Securities (other than the ABS Prior Securities and ABS Series D Securities)
held by such Holders at the time of filing the registration statement,

               (B) second, to ABS with respect to any ABS Prior Securities and
ABS Series D Securities requested to be included in such registration, and
<PAGE>

               (C) third, among all Holders of other Registrable Securities in
proportion, as nearly as practicable, to the respective number of shares of
other Registrable held by such Holders at the time of the registration
statement.

Those Demand and other Registrable Securities which are excluded from the
underwriting by reason of the managing underwriter's marketing limitation and
all other Registrable Securities not originally requested to be so included
shall not be included in such registration and shall be withheld from the market
by the Holders thereof for a period (not to exceed 180 days) which the managing
underwriter reasonably determines is necessary to effect the underwritten public
offering.

          (g) If the managing underwriter has not limited the number of
Registrable Securities to be underwritten, the Company and, subject to the
requirements of Section 7 hereof, other holders of the Company's securities may
include securities for its (or their) own account in such registration if the
managing underwriter so agrees and if the number of Registrable Securities which
would otherwise have been included in such registration and underwriting will
not thereby be limited.

          3.  Piggyback Registration.
              ----------------------

          (a) Each time the Company shall determine to file a registration
statement under the Securities Act (other than on Form S-4, S-8 or a
registration statement on Form S-1 covering solely an employee benefit plan) in
connection with the proposed offer and sale of any of its securities either for
its own account or on behalf of any other security holder, the Company agrees to
give promptly written notice of its determination to all Holders of Registrable
Securities.  Upon the written request of a Holder of any shares of Registrable
Securities given within thirty (30) days after the receipt of such written
notice from the Company, the Company agrees to cause all such Registrable
Securities, the Holders of which have so requested registration thereof, to be
included in such registration statement and registered under the Securities Act,
all to the extent requisite to permit the sale or other disposition by the
prospective seller or sellers of the Registrable Securities to be so registered.

          (b) If the registration of which the Company gives written notice
pursuant to Section 3(a) is for a public offering involving an underwriting, the
Company shall so advise the Holders as a part of its written notice.  In such
event the right of any Holder to registration pursuant to this Section 3 shall
be conditioned upon such Holder's participation in such underwriting and the
inclusion of such Holder's Registrable Securities in the underwriting to the
extent provided herein.  All Holders proposing to distribute their Registrable
Securities through such underwriting agree to enter into (together with the
Company and the other holders distributing their securities through such
underwriting) an underwriting agreement with the underwriter or underwriters
selected for such underwriting by the Company.

          (c) Notwithstanding any other provision of this Section 3, if the
managing underwriter of an underwritten distribution advises the Company and the
Holders of the Registrable Securities participating in such registration in
writing that in its good faith judgment the number of shares of Registrable
Securities and the other securities requested to be registered exceeds the
number of shares of Registrable Securities and other securities which can be
sold in such offering, then (i) the number of shares of Registrable Securities
and other
<PAGE>

securities so requested to be included in the offering shall be reduced to that
number of shares which in the good faith judgment of the managing underwriter
can be sold in such offering (except for shares to be included pursuant to a
demand registration under Section 2 hereof, in an offering initiated upon the
exercise of such rights, and except for shares to be issued by the Company in an
offering initiated by the Company, which shall have priority over the shares of
Registrable Securities), and (ii) such reduced number of shares shall be
allocated:

               (A) first, among all Holders of Demand Securities in proportion,
as nearly as practicable, to the respective number of shares of Demand
Securities (other than the ABS Prior Securities and ABS Series D Securities)
held by such Holders at the time of filing the registration statement,

               (B) second, to ABS with respect to any ABS Prior Securities and
ABS Series D Securities requested to be included in such registration,

               (C) third, among all Holders of other Registrable Securities in
proportion, as nearly as practicable, to the respective number of shares of
other Registrable held by such Holders at the time of the registration
statement, and

               (D) fourth, among all participating Holders of other securities
in proportion, as nearly as practicable, to the respective number of shares of
other securities held by such Holders at the time of filing the registration
statement.

     Any Registrable Securities excluded or withdrawn from such underwriting
shall be excluded and withdrawn from the registration.

          (d) The Company shall not be obligated, with respect to any Holder of
Registrable Securities, to include any of such Holder=s Registrable Securities
in a registration statement pursuant to this Section 3 more than four times.
Subject to the foregoing sentence, if a Holder decides not to include any of its
Registrable Securities in any registration statement filed by the Company, such
Holder shall nevertheless continue to have the right to include any Registrable
Securities in any subsequent registration statement or statements that may be
filed by the Company with respect to offerings of its securities.

          4.  Registration Procedures.  If and whenever the Company is required
              -----------------------
by the provisions of Section 2 or 3 hereof to effect the registration of
Registrable Securities under the Securities Act, the Company, at its expense and
as expeditiously as possible, agrees to:

          (a) In accordance with the Securities Act and all applicable rules and
regulations, 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 effective until the securities covered by such
registration statement have been sold, and prepare and file with the Commission
such amendments and supplements to such registration statement and the
prospectus contained therein as may be necessary to keep such registration
statement effective and such registration statement and prospectus accurate and
complete for a period of 90 days from the effective date or until the securities
covered by such registration statement have been sold, whichever occurs first;
<PAGE>

          (b) If the offering is to be underwritten in whole or in part, enter
into a written underwriting agreement in form and substance reasonably
satisfactory to the managing underwriter of the public offering and the Holders
of a majority of Registrable Securities participating in such offering;

          (c) Furnish to the Holders of securities participating in such
registration and to the underwriters of the securities being registered such
number of copies of the registration statement and each amendment and supplement
thereto, preliminary prospectus, final prospectus and such other documents as
such underwriters and Holders may reasonably request;

          (d) Use its best efforts to register or qualify the securities covered
by such registration statement under such state securities or blue sky laws of
such jurisdictions as such participating Holders of Registrable Securities and
underwriters may reasonably request at least ten (10) days prior to the original
filing of such registration statement, except that the Company shall not for any
purpose be required to execute a general consent to service of process or to
qualify to do business as a foreign corporation in any jurisdiction where it is
not so qualified;

          (e) Notify the Holders of Registrable Securities participating in such
registration, promptly after it shall receive notice thereof, of the date and
time when such 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;

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

          (g) Prepare and file promptly with the Commission, and promptly notify
such Holders of Registrable Securities of the filing of, such amendments or
supplements to such registration statement or prospectus as may be necessary to
correct any statements or omissions if, at the time when a prospectus relating
to such securities is required to be delivered under the Securities Act, any
event has occurred as the result of which any such prospectus or any other
prospectus as then in effect would include an untrue statement of a material
fact or omit to state any material fact required to be stated therein or
necessary to make the statements therein not misleading;

          (h) In case any of such Holders of Registrable Securities or any
underwriter for any such Holders is required to deliver a prospectus at a time
when the prospectus then in circulation is not in compliance with the Securities
Act or the rules and regulations of the Commission, prepare promptly upon
request such amendments or supplements to such registration statement and such
prospectus as may be necessary in order for such prospectus to comply with the
requirements of the Securities Act and such rules and regulations;

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

          (j) At the request of any Holder of Registrable Securities covered by
such registration statement, (i) furnish to such Holder on the effective date of
the registration statement or, if such registration includes an underwritten
public offering, at the closing provided for in the underwriting agreement, an
opinion dated such date of the counsel representing the Company for the purposes
of such registration, addressed to the underwriters, if any, and to the Holder
or Holders making such request, covering such matters with respect to the
registration statement, the prospectus and each amendment or supplement thereto,
proceedings under state, federal and other securities laws, other matters
relating to the Company, the securities being registered and the offer and sale
of such securities as are customarily the subject of opinions of issuer's
counsel provided to underwriters in underwritten public offerings, and such
opinion of counsel shall additionally cover such legal matters with respect to
the registration as such requesting Holder or Holders may reasonably request,
and (ii) use its best efforts to furnish to such Holders letters dated each of
such effective date and such closing date, from the independent certified public
accountants of the Company, addressed to the underwriters, if any, and to the
Holder or Holders making such request, stating that they are independent
certified public accountants within the meaning of the Securities Act and
dealing with such matters as the underwriters may request, or if the offering is
not underwritten that in the opinion of such accountants the financial
statements and other financial data of the Company included in the registration
statement or the prospectus or any amendment or supplement thereto comply in all
material respects with the applicable accounting requirements of the Securities
Act, and additionally covering such other accounting and financial matters,
including information as to the period ending not more than five (5) business
days prior to the date of such letter with respect to the registration statement
and prospectus, as such requesting Holder or Holders may reasonably request.

          (k) Apply for listing and use its best efforts to list the Registrable
Securities, if any, being registered on any national securities exchange on
which a class of the Company's equity securities is listed (and to maintain such
listing during the pendency of the relevant registration period) or, if the
Company does not have a class of equity securities listed on a national
securities exchange, apply for qualification and use its reasonable best efforts
to qualify the Registrable Securities, if any, being registered for inclusion on
the automated quotation system of the NASD (and to maintain such qualification
during the pendency of the relevant registration period).

          (l) Make senior executives of the Company available to assist the
underwriters with respect to, and to accompany the underwriters on the so-called
"road show" in connection with, marketing efforts for the distribution and sale
of Registrable Securities pursuant to a Registration Statement.

     5.   Expenses.
          --------

          (a) With respect to each inclusion of shares of Registrable Securities
in a registration statement pursuant to Section 2 hereof, the Company agrees to
bear all fees, costs and expenses of such registration and the public offering
in connection therewith; provided, however, that Holders participating in any
                         --------  -------
such registration agree to bear their pro rata share of the underwriting
discount and commissions.

          (b) The fees, costs and expenses of registration to be borne as
provided
<PAGE>

in paragraph (a) above, shall consist of all registration, filing and NASD fees,
printing expenses, fees and disbursements of counsel and accountants for the
Company, fees and disbursements of counsel for the underwriter or underwriters
of such securities (if the Company and/or selling security holders are otherwise
required to bear such fees and disbursements), all legal fees and disbursements
and other expenses of complying with state securities or blue sky laws of any
jurisdictions in which the securities to be offered are to be registered or
qualified, reasonable fees and disbursements of one firm of counsel for the
selling security holders designated by the Holders of a majority of the
Registrable Securities included in such registration.

          (c) Notwithstanding the foregoing:

              (i)  in the event that a registration pursuant to Section 2 is
requested by an Initiating Holder and such request is withdrawn prior to the
filing of a registration statement by the Company, or the Holders of Demand
Securities cause the Company to withdraw a registration statement prior to its
effectiveness, then either (at the election of the Initiating Holder), then
either (A) the Initiating Holder and other Holders of Demand Securities
requesting inclusion of their shares in such registration shall bear pro rata
all fees, costs and expenses of the registration and preparation of the
registration statement or (B) such requested registration shall be deemed to be
one of the registrations the Company is required to effect pursuant to Section 2
hereof; provided, however, that if at the time of such withdrawal, the Holders
        --------  -------
have learned of a material adverse change in the condition, business, or
prospects of the Company as of the date of their request for such registration
not known to the Holders at the time of their request and have withdrawn their
request for registration with reasonable promptness after learning of such
material adverse change, then the Holders shall not be required to pay any of
such expenses and shall retain their rights pursuant to this Section 2;
and

              (ii) the Company shall pay the expenses of an registration on Form
S-3 requested pursuant to Section 2 hereof only with respect to the first two
Forms S-3 so filed.

     6.   Indemnification.
          ---------------

          (a) The Company hereby agrees to indemnify and hold harmless each
Holder of Registrable Securities which are included in a registration statement
pursuant to the provisions of this Agreement and each of such Holder's officers,
directors, partners, members, legal counsel and accountants, and each Person who
controls such Holder within the meaning of the Securities Act and any
underwriter (as defined in the Securities Act) for such Holder, and any Person
who controls such underwriter within the meaning of the Securities Act, from and
against, and agrees to reimburse such Holder, its officers, directors, partners,
members, legal counsel, accountants and controlling Persons and each such
underwriter and controlling Person of such underwriter with respect to, any and
all claims, actions (actual or threatened), demands, losses, damages,
liabilities, costs and expenses to which such Holder, its officers, directors,
partners, members, legal counsel, accountants or controlling Persons, or any
such underwriter or controlling Person of such underwriter may become subject
under the Securities Act or otherwise, insofar as such claims, actions, demands,
losses, damages, liabilities, costs or expenses arise out of or are based upon
(i) any untrue statement or alleged untrue statement of any material fact
contained in such registration statement, any prospectus contained therein, or
<PAGE>

any amendment or supplement thereto, (ii) the omission or alleged omission to
state therein a material fact necessary to make the statements therein, in light
of the circumstances under which they were made, not misleading or (iii)any
violation or alleged violation by the Company of the Securities Act, the
Exchange Act, any federal or state securities law or any rule or regulation
promulgated under the Securities Act, the Exchange Act or any federal or state
securities law in connection with the offering covered by such registration
statement; provided, however, that the Company will not be liable to any such
Person to the extent that any such claim, action, demand, loss, damage,
liability, cost or expense is caused by an untrue statement or alleged untrue
statement or omission or alleged omission so made in strict conformity with
written information furnished by such Holder, such underwriter or such
controlling Person specifically for use in the preparation thereof; provided,
further, that with respect to an untrue statement or alleged untrue statement or
omission or alleged omission made in a preliminary prospectus but eliminated or
remedied in the amended prospectus on file with the Commission at the time the
registration statement becomes effective (or an amended prospectus filed with
the Commission pursuant to Rule 424(b)) (the "Final Prospectus"), this indemnity
                                              ----------------
shall not inure to the benefit of any underwriter or Holder or controlling
person of any such underwriter or Holder if, having previously been furnished by
or on behalf of, the Company with copies of the Final Prospectus, the
underwriter in an underwritten offering, or the Holder in a nonunderwritten
offering, thereafter fails to deliver, prior to or concurrently with the sale of
securities to such person, a copy of the Final Prospectus to the person
asserting the claim, action, demand, loss, damage, liability, cost or expense.

          (b) Each Holder of shares of Registrable Securities which are included
in a registration statement pursuant to the provisions of this Agreement hereby
agrees (severally and not jointly) to indemnify and hold harmless the Company,
its officers, directors, legal counsel and accountants and each Person who
controls the Company within the meaning of the Securities Act, from and against,
and agrees to reimburse the Company, its officers, directors, legal counsel,
accountants and controlling Persons with respect to, any and all claims,
actions, demands, losses, damages, liabilities, costs or expenses to which the
Company, its officers, directors, legal counsel, accountants or such controlling
Persons may become subject under the Securities Act or otherwise, insofar as
such claims, actions, demands, losses, damages, liabilities, costs or expenses
are caused by any untrue or alleged untrue statement of any material fact
contained in such registration statement, any prospectus contained therein or
any amendment or supplement thereto, or are caused by the omission or the
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, in each case to the extent, but only to
the extent, that such untrue statement or alleged untrue statement or omission
or alleged omission was so made in reliance upon and in strict conformity with
written information furnished by such Holder specifically for use in the
preparation thereof; provided, however, that the indemnity agreement contained
                     --------  -------
in this subsection 6(b) shall not apply to amounts paid in settlement of any
such loss, claim, damage, liability or action if such settlement is effected
without the consent of the Holder, which consent shall not be unreasonably
withheld or delayed; provided, further, that the total amounts payable in
                     --------  -------
indemnity by a Holder under this subsection 6(b) shall not exceed the net
proceeds received by such Holder in the registered offering out of which such
claim, action, demand, loss, damage, liability, cost, or expense arises.

          (c) Promptly after receipt by a party indemnified pursuant to the
provisions of subsection (a) or (b) of this Section 6 of notice of the
commencement of any action
<PAGE>

involving the subject matter of the foregoing indemnity provisions, such
indemnified party will, if a claim therefor is to be made against the
indemnifying party pursuant to the provisions of subsection (a) or (b), notify
the indemnifying party of the commencement thereof; but the omission so to
notify the indemnifying party will not relieve it from any liability which it
may have to an indemnified party otherwise than under this Section 6 and shall
not relieve the indemnifying party from liability under this Section 6 unless
such indemnifying party is prejudiced by such omission. In case any such action
is brought against any indemnified party, and it notifies the indemnifying party
of the commencement thereof, the indemnifying party will be entitled to
participate therein and, to the extent that it may wish, jointly with any other
indemnifying parties similarly notified, to assume the defense thereof, with
counsel reasonably satisfactory to such indemnified party; provided, however,
that if the defendants in any such action include both the indemnified party and
the indemnifying party and the indemnified party shall have reasonably concluded
that there may be legal defenses available to it and/or other indemnified
parties which are different from or additional to those available to the
indemnifying party, the indemnified party or parties shall have the right to
select separate counsel (in which case the indemnifying party shall not have the
right to direct the defense of such action on behalf of the indemnified party or
parties). Upon the permitted assumption by the indemnifying party of the defense
of such action, and approval by the indemnified party of counsel, the
indemnifying party shall not be liable to such indemnified party under
subsection (a) or (b) for any legal or other expenses subsequently incurred by
such indemnified party in connection with the defense thereof (other than
reasonable costs of investigation) unless (i) the indemnified party shall have
employed separate counsel in connection with the assertion of legal defenses in
accordance with the proviso to the next preceding sentence, (ii) the
indemnifying party shall not have employed counsel reasonably satisfactory to
the indemnified party to represent the indemnified party within a reasonable
time, (iii) the indemnifying party and its counsel do not actively and
vigorously pursue the defense of such action, or (iv) the indemnifying party has
authorized the employment of counsel for the indemnified party at the expense of
the indemnifying party. No indemnifying party shall be liable to an indemnified
party for any settlement of any action or claim without the consent of the
indemnifying party and no indemnifying party may unreasonably withhold its
consent to any such settlement. No indemnifying party will 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 with respect to such claim or
litigation.

          (d) If the indemnification provided for in subsection (a) or (b) of
this Section 6 is held by a court of competent jurisdiction to be unavailable to
a party to be indemnified with respect to any claims, actions, demands, losses,
damages, liabilities, costs or expenses referred to therein, then each
indemnifying party under any such subsection, in lieu of indemnifying such
indemnified party thereunder, hereby agrees to contribute to the amount paid or
payable by such indemnified party as a result of such claims, actions, demands,
losses, damages, liabilities, costs or expenses in such proportion as is
appropriate to reflect the relative fault of the indemnifying party on the one
hand and of the indemnified party on the other in connection with the statements
or omissions which resulted in such claims, actions, demands, losses, damages,
liabilities, costs or expenses, as well as any other relevant equitable
considerations.  The relative fault of the indemnifying party and of the
indemnified party shall be determined by reference to, among other things,
whether the untrue or alleged untrue statement of a material fact or the
omission or alleged omission to state a material fact relates to information
supplied by the indemnifying party or by the indemnified party and the parties'
relative intent,
<PAGE>

knowledge, access to information and opportunity to correct or prevent such
statement or omission. Notwithstanding the foregoing, the amount any Holder of
Registrable Securities shall be obligated to contribute pursuant to this
subsection (d) shall be limited to an amount equal to the per share public
offering price (less any underwriting discount and commissions) multiplied by
the number of shares of Registrable Securities sold by such Holder pursuant to
the registration statement which gives rise to such obligation to contribute
(less the aggregate amount of any damages which such Holder has otherwise been
required to pay in respect of such claim, action, demand, loss, damage,
liability, cost or expense or any substantially similar claim, action, demand,
loss, damage, liability, cost or expense arising from the sale of such
Registrable Securities).

          (e) No person guilty of fraudulent misrepresentation (within the
meaning of Section 11(f) of the Securities Act) shall be entitled to
contribution hereunder from any person who was not guilty of such fraudulent
misrepresentation.

          (f) The obligations of the Company and Holders under this Section 6
shall survive the completion of any offering of Registrable Securities in a
registration statement and termination of this Agreement.

     7.   Future Registration Rights.
          --------------------------

          (a) The Company, if and to the extent expressly approved by the Board,
may subsequently grant the benefits afforded hereunder (with respect to the
Holders of Future Registrable Securities) to any employee of or consultant to,
or holder of equity securities of, the Company; provided, that such Person
                                                --------
executes a written agreement to be bound by the terms hereof as if he or she
were an original party hereto.

          (b) Without the prior written consent of the Holders of a Majority of
the Demand Securities and of the Holders of a Majority of the Series A Investor
Securities and except as expressly permitted by this Agreement and except for an
underwriting agreement between the Company and one or more professional
underwriters of securities, the Company shall not enter into any agreement with
any Holder or prospective Holder of  any securities of the Company which would
allow such Holder or prospective Holder to (i) include such securities in any
registration filed under Section 2 or 3 hereof unless, under the terms of such
agreement, such holder or prospective holder may include such securities in any
such registration only to the extent that the inclusion of such securities will
not reduce the amount of Registrable securities of the Holders which are
included or (b) to make a demand registration.

     8.   Shareholder Information.  The Company may request each Holder of
          -----------------------
Registrable Securities as to which any registration is to be effected pursuant
to this Agreement to furnish the Company with such information with respect to
such Holder and the distribution of such Registrable Securities as the Company
may from time to time reasonably request in writing and as shall be required by
law or by the Commission in connection therewith, and each Holder of Registrable
Securities as to which any registration is to be effected pursuant to this
Agreement agrees to furnish the Company with such information.
<PAGE>

     9.    Forms.  All references in this Agreement to particular forms of
           -----
registration statements are intended to include, and shall be deemed to include,
references to all successor forms which are intended to replace, or to apply to
similar transactions as, the forms herein referenced.

     10.   Lockup Agreement.  In consideration for the Company agreeing to its
           ----------------
obligations under this Agreement, each Investor and each Founder agrees in
connection with any registration of the Company's securities that, upon the
request the managing underwriter of any underwritten offering of the Company's
securities (or, if there is no managing underwriter, the Company), it or he
shall not sell, make any short sale of, loan, grant any option for the purchase
of, or otherwise dispose of any capital stock of the Company (other than those
that included in such registration) without the prior written consent of such
managing underwriter (or, if there is no managing underwriter, the Company) for
such period of time as such managing underwriter (or, if there is no managing
underwriter, the Company) may specify (not to exceed 180 days); provided that
all directors, executive officers and the Holders of 5% or more of the Common
Stock are similarly restricted; provided further that such agreement shall apply
only to the IPO and shall not apply to the Registrable securities, if any, sold
in the IPO.

     11.   Termination of Registration Rights. The registration rights granted
           ----------------------------------
pursuant to this Agreement will terminate five years after the IPO.

     12.   Transfer of Registration Rights.  The rights to cause the Company to
           -------------------------------
register securities granted to the Holders of Registrable Securities pursuant to
this Agreement may be transferred or assigned only (i) with respect to ABS, to
an immediate or remote transferee of ABS who after such transfer is the Holder
of not less than 10% of the number of shares of ABS Securities that ABS is the
Holder of as of the date hereof, (ii) with respect to a Series A Investor, to an
immediate or remote transferee of such Series A Investor who after such transfer
is the Holder of not less than 10% of the number of shares of Series A Investor
Securities outstanding as of the date hereof or (iii) with respect to the
Premier, to a Designated Affiliate (as defined in the Premier Stock Purchase
Agreement). Any purported assignment or transfer of such rights made in
contravention of this Section 12 shall be null and void.

     13.   Miscellaneous.
           -------------

           13.1  Waivers and Amendments.
                 ----------------------

                 (a) With the written consent of the Holders of a Majority of
the Registrable Securities, the obligations of the Company and the rights of the
Holders of Registrable Securities under this Agreement may be waived (either
generally or in a particular instance, either retroactively or prospectively and
either for a specified period of time or indefinitely), and with the same
consent the Company, when authorized by resolution of its Board, may enter into
a supplementary agreement for the purpose of adding any provisions to or
changing in any manner or eliminating any of the provisions of this Agreement or
of any supplemental agreement or modifying in any manner the rights and
obligations hereunder of the Holders of Registrable Securities and the Company;
provided, however, that no such waiver or supplemental agreement shall reduce
the aforesaid proportion of Registrable Securities, the Holders of which are
required to consent to any waiver or supplemental agreement, without the consent
of the Holders of all of the Registrable Securities.
<PAGE>

                 (b) Notwithstanding subsection (a) above:

                     (i)   without the consent of ABS, the obligations of the
Company to ABS and the rights of ABS hereunder may not be waived, modified or
amended in such manner as to adversely affect the rights of ABS;

                     (ii)  without the consent of the Holders of a Majority of
the Series A Investors, the obligations of the Company to the Series A Investors
and the rights of the Series A Investors hereunder may not be waived, modified
or amended in such manner as to adversely affect the rights of the Series A
Investors; and

                     (iii) without the consent of Premier, the obligations of
the Company to Premier and the rights of Premier hereunder may not be waived,
modified or amended in such manner as to adversely affect the rights of Premier.

                 (c) Upon the effectuation of each such waiver, consent or
agreement of amendment or modification, the Company agrees to give promptly
written notice thereof to the Holders of the Registrable Securities who have not
previously consented thereto in writing.

                 (d) Neither this Agreement nor any provision hereof may be
changed, waived, discharged or terminated orally or by course of dealing, but
only by a statement in writing signed by the party against which enforcement of
the change, waiver, discharge or termination is sought, except to the extent
provided in this Section 13.1. Specifically, but without limiting the generality
of the foregoing, the failure of any party hereunder at any time or times to
require performance of any provision hereof by the Company shall in no manner
affect the right of such party at a later time to enforce the same. No waiver by
any party of the breach of any term or provision contained in this Agreement, in
any one or more instances, shall be deemed to be, or construed as, a further or
continuing waiver of any such breach, or a waiver of the breach of any other
term or covenant contained in this Agreement.

           13.2  Effect of Waiver or Amendment.
                 -----------------------------

                 (a) Each Holder of Registrable Securities acknowledges that by
operation of Section 13.1 hereof the Holders of a Majority of the Registrable
Securities will, subject to the limitations contained in Section 13.1(b), have
the right and power to diminish or eliminate certain rights of such Holder under
this Agreement.

                 (b) Each Holder of Series A Investor Securities acknowledges
that by operation of Section 13.1 hereof the Holders of a Majority of the Series
A Investor Securities will, have the right and power to diminish or eliminate
certain rights of such Holders under this Agreement

           13.3  Rights of Holders Inter Se.  Each Holder of Registrable
                 --------------------------
Securities shall have the absolute right to exercise or refrain from exercising
any right or rights which such Holder may have by reason of this Agreement or
any Registrable Security, including, without limitation, the right to consent to
the waiver of any obligation of the Company under this Agreement and to enter
into an agreement with the Company for the purpose of modifying this
<PAGE>

Agreement or any agreement effecting any such modification, and such Holder
shall not incur any liability to any other Holder with respect to exercising or
refraining from exercising any such right or rights.

           13.4  Notices.  All notices, requests or consents required or
                 -------
permitted under this Agreement shall be made in writing and shall be given to
the other parties by personal delivery, registered or certified mail (with
return receipt), overnight air courier (with receipt signature) or facsimile
transmission (with "answerback" confirmation of transmission), sent to such
party's addresses or telecopy numbers as are set forth below such party's
signatures to this Agreement, or such other addresses or telecopy numbers of
which the parties have given notice pursuant to this Section 12.4.  Each such
notice, request or consent shall be deemed effective upon the date of actual
receipt, receipt signature or confirmation of transmission, as applicable (or if
given by registered or certified mail, upon the earlier of (i) actual receipt or
(ii) three days after deposit thereof in the United States mail (with respect to
addresses within the United States) or  ten days after deposit thereof in the
United States mail (with respect to addresses outside of the United States).

           13.5  Severability.  Should any one or more of the provisions of this
                 ------------
Agreement or of any agreement entered into pursuant to this Agreement be
determined to be illegal or unenforceable, all other provisions of this
Agreement and of each other agreement entered into pursuant to this Agreement,
shall be given effect separately from the provision or provisions determined to
be illegal or unenforceable and shall not be affected thereby.

           13.6  No Third Parties.  Subject to Section 6 hereof, this Agreement
                 ----------------
shall not run to the benefit of or be enforceable by any Person other than a
party to this Agreement or, with respect to the Company, any successor thereto.

           13.7  Headings.  The headings of the sections, subsections and
                 --------
paragraphs of this Agreement have been inserted for convenience of reference
only and do not constitute a part of this Agreement.

           13.8  Choice of Law.  It is the intention of the parties that the
                 -------------
internal substantive laws, and not the laws of conflicts, of the State of
California should govern the enforceability and validity of this Agreement, the
construction of its terms and the interpretation of the rights and duties of the
parties.

           13.9  Counterparts.  This Agreement may be executed in any number of
                 ------------
counterparts and by different parties hereto in separate counterparts, with the
same effect as if all parties had signed the same document. All such
counterparts shall be deemed an original, shall be construed together and shall
constitute one and the same instrument.

           13.10 Arbitration.
                 -----------

                 (a) Any and all disputes or controversies, whether of law or
fact and of any nature whatsoever arising from or respecting this Agreement,
shall be decided by binding arbitration in accordance with Title 9 of the United
States Code and the Commercial Arbitration Rules of the American Arbitration
Association (the "Association"). If the parties are unable to agree upon a
                  -----------
single arbitrator, the arbitrator shall be a single, independent arbitrator

<PAGE>

selected by the Association.

          (b) Arbitration shall take place at Los Angeles, California, or any
other location mutually agreeable to the parties.  The decision of the
arbitrator shall be final and binding upon all parties hereto and all persons
claiming under and through them and judgment thereon may be entered by any court
of competent jurisdiction. The fees and expenses of the arbitrator shall be paid
equally by the parties to such arbitration.
<PAGE>

          13.11 Rule 144.  To the extent that the Company is subject to the
                --------
filing and reporting requirements of the Securities Act and the Exchange Act,
and so long as there are Demand Securities outstanding, the Company will file
the reports required to be filed by it under the Securities Act and the Exchange
Act and the rules and regulations adopted by the SEC thereunder, make and keep
public information available, as those terms are understood and defined in Rule
144 under the Securities Act, at all times after the IPO, and will take such
further action as any holder of Demand Securities may reasonably request, all to
the extent required from time to time to enable such Holder to sell Demand
Securities without registration under the Securities Act within the limitation
of the exemptions provided by (i) Rule 144 or Rule 144A under the Securities
Act, as such Rule may be amended from time to time, or (ii) any similar rule or
regulation hereafter adopted by the SEC.  Upon the request of any holder of
Demand Securities, the Company will deliver to such holder a written statement
as to whether it has complied with such information and requirements and with a
copy of the most recent annual or quarterly report of the Company, and such
other reports and documents of the Company as a Holder may reasonably request in
availing itself of any rule or regulation of the Commission allowing a Holder to
sell any such securities without registration (at any time after the Company has
become subject to the reporting requirements of the Exchange Act).

          13.12 Mergers, etc.  The Company shall not, directly or indirectly,
                -------------
enter into any merger, consolidation or reorganization in which the Company
shall not be the surviving corporation unless the surviving corporation shall,
prior to such merger, consolidation or reorganization, agree in writing to
assume the obligations of the Company under this Agreement, and for that purpose
references hereunder to "Registrable Securities" shall be deemed to include the
securities which the Holders would be entitled to receive in exchange for Common
Stock under any such merger, consolidation or reorganization, provided that to
the extent such securities to be received are convertible into shares of common
stock of the issuer thereof, then any such shares of common stock or other
securities as are issued or issuable upon conversion of said convertible
securities shall also be included within the definition of "Registrable
Securities".

          13.13 Entire Agreement.  This Agreement contains the entire
                ----------------
understanding of the parties hereto in respect of its subject matter and
supersedes all prior and contemporaneous agreements and understandings, oral and
written, between the parties with respect to such subject matter (except that
the Investors= obligations under any confidentiality agreement with the Company
shall continue in full force and effect).

          13.14 Termination of Prior Agreement.  The Company, ABS and Premier
                ------------------------------
hereby agree that:

                (a) Subject to subsection (b) below, the Prior Agreement is
hereby terminated and of no further force and effect.

                (b) If, pursuant to Section 2 of the Series A Preferred Stock
Purchase Agreement, the Company is required to return to the Series A Investors
the amounts paid thereby for the Series A preferred Stock, then thereupon and
thereby (i) this Agreement will be terminated and (ii) the Prior Agreement shall
be reinstated and shall thereafter continue in full force and effect.
<PAGE>

                [REGISTRATION RIGHTS AGREEMENT SIGNATURE PAGE]


          IN WITNESS WHEREOF, the parties hereto have caused this Registration
Rights Agreement to be duly executed as of the date first above written.


                                   AMERICAN PHARMACEUTICAL PARTNERS, INC.



                                   By:
                                      -----------------------------------
                                        PATRICK SOON-SHIONG, President

                                   Address for Notices:
                                   3212 Nebraska Avenue
                                   Santa Monica, CA  90404
                                   Telecopy Number: (310) 264-7775


                                   PREMIER PURCHASING PARTNERS, L.P.
                                   By:  Premier Plans, Inc.
                                        Its General Partner



                                        By:
                                           ------------------------------

                                        Title:
                                              ---------------------------

                                   Address for Notices:
                                   12730 High Bluff Drive, Suite 300
                                   San Diego, CA 92130-2099
                                   Telecopy Number: (619) 481-9914


                                   VIVORX PHARMACEUTICAL, INC.


                                   By:
                                      -----------------------------------
                                        PATRICK SOON-SHIONG, President

                                   Address for Notices:
                                   3212 Nebraska Avenue
                                   Santa Monica, CA 90404
                                   Telecopy Number: (310) 264-7775
<PAGE>

                                   [SIGNATURE BLOCKS FOR INVESTORS]