EXHIBIT 10.13



              FIRST AMENDED AND RESTATED INVESTOR RIGHTS AGREEMENT
              ----------------------------------------------------


         THIS FIRST AMENDED AND RESTATED  INVESTOR  RIGHTS  AGREEMENT is entered
into as of the date  provided  below among  Jenner  Technologies,  a  California
corporation (the "Company"),  the purchasers of the Company's Series A Preferred
Stock  under  that  certain  Series A  Preferred  Stock  Subscription  Agreement
confirmed and accepted as of May 28, 1993 (the "Series A Investors")  and Hayden
Leason (the "Series B  Investor").  Both the Series A Investors and the Series B
Investor are  collectively  referred to herein as the "Investors" and are listed
on the Schedule of Investors attached to this Agreement as Exhibit A.

                                    RECITALS

         WHEREAS,  the Company  and the Series A  Investors  are parties to that
certain Investor Rights Agreement dated May 7, 1993 (the "Prior Agreement"); and

         WHEREAS,  the Series A Investors have certain  registration rights upon
conversion of their Series A Preferred Stock under the Prior Agreement; and

         WHEREAS, the Company and Series A Investors wish to induce the Series B
Investor to purchase Series B Preferred Stock pursuant to the Series B Preferred
Stock and Warrant Purchase Agreement dated as of July 25, 1995; and

         WHEREAS,  the sale of the  Series  B  Preferred  Stock to the  Series B
Investor is  conditioned  upon the  registration  rights  being  extended to the
Series B Investor; and

         WHEREAS,  the Prior  Agreement  may be amended as set forth in Sections
1.15 and 3.6 thereof; and

         WHEREAS,  the Series A  Investors  wish to amend and  restate the Prior
Agreement to include the Series B Investor;

         NOW THEREFORE, in consideration of the foregoing,  the parties agree as
follows:


         NOW THEREFORE, the parties hereby agree as follows:

         1. Registration Rights. The Company covenants and agrees as follows:

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

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

                       "Company"  shall mean Jenner  Technologies,  a California
corporation.









                       "Holder"  shall  mean  any  person  holding   Registrable
Securities (or  securities  convertible  into or  exchangeable  for  Registrable
Securities)  to whom the rights under this Section 1 were granted  directly from
the  Company  and any  person  holding  Registrable  Securities  (or  securities
convertible into or exchangeable for Registrable  Securities) to whom the rights
under this  Section 1 have been  transferred  in  accordance  with  Section 1.13
hereof.

                       "Initiating  Holders"  shall mean any  Holders who in the
aggregate  possess at least 80% of the  Registrable  Securities  (or  securities
convertible or exchangeable for Registrable Securities).

                       "Registerable  Securities"  means  (i) the  Common  Stock
issued or  issuable  upon  conversion  of the Series A  Preferred  Stock  issued
pursuant to the Series A Preferred  Stock  Subscription  Agreements  between the
Company and  certain  Series A Investors  confirmed  and  accepted as of May 28,
1993,  (ii) the Common Stock issued or issuable upon  conversion of the Series B
Preferred  Stock  issued  pursuant to the Series B  Preferred  Stock and Warrant
Purchase  Agreement  dated July 25,  1995  between  the Company and the Series B
Investor, (iii) the Common Stock issued or issuable upon exercise of the Warrant
dated July 25, 1995 issued by the Company to the Series B Investor, and (iv) any
Common Stock of the Company issued or issuable in respect of the above described
securities upon any stock split,  stock dividend,  recapitalization,  or similar
event,  or any Common  Stock  otherwise  issued or issuable  with respect to the
above described  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,  or (B) sold or are
available  for  immediate  sale in the  opinion of  counsel to the  Company in a
transaction exempt from the registration and prospectus delivery requirements of
the Act so that all transfer restric tions 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 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 the Company in complying  with Sections
1.5,  1.6 and 1.7  hereof,  including,  without  limitation,  all  registration,
qualification  and  filing  fees,  printing  expenses,  escrow  fees,  fees  and
disbursements  of  counsel  for the  Company,  blue sky fees and  expenses,  the
expense of any special audits  incident to or required by any such  registration
(but excluding the compensation of regular  employees of the Company which shall
be paid in any event by the Company).

                       "Restricted  Securities" shall mean the securities of the
Company required to bear the legend set forth in Section 1.3 hereof.

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

                       "Selling Expenses" shall mean all underwriting discounts,
selling  commissions  and stock  transfer  taxes  applicable  to the  securities
registered by the Holders.


                                       -2-








                  1.2 Restrictions on Transferability. The Restricted Securities
shall not be sold,  assigned,  transferred or pledged except upon the conditions
specified in this Section 1, which conditions are intended to ensure  compliance
with the provisions of the Act. Each Investor will cause any proposed purchaser,
assignee,  transferee, or pledgee of the Securities held by an Investor to agree
to take  and  hold  such  securities  subject  to the  provisions  and  upon the
conditions specified in this Section 1.

                  1.3  Restrictive   Legend.   Each  certificate  or  instrument
representing   Registrable   Securities,   or   securities   convertible   into,
exchangeable  for  or  exercisable  for  Registrable  Securities  shall  (unless
otherwise  permitted  by the  provisions  of  Section  1.4  below) be stamped or
otherwise  imprinted  with a legend in the  following  form (in  addition to any
legend required under applicable state securities laws):

                  THE SECURITIES REPRESENTED BY THIS CERTIFICATE HAVE
                  BEEN  ACQUIRED  FOR  INVESTMENT  AND  HAVE NOT BEEN
                  REGISTERED  UNDER THE SECURITIES ACT OF 1933.  SUCH
                  SECURITIES  MAY NOT BE SOLD OR  TRANSFERRED  IN THE
                  ABSENCE OF SUCH  REGISTRATION OR UNLESS THE COMPANY
                  RECEIVES   AN   OPINION   OF   COUNSEL   REASONABLY
                  ACCEPTABLE TO IT STATING THAT SUCH SALE OR TRANSFER
                  IS  EXEMPT  FROM THE  REGISTRATION  AND  PROSPECTUS
                  DELIVERY REQUIREMENTS OF SAID ACT.

         Each Investor and Holder  consents to the Company  making a notation on
its records and giving  instructions  to any transfer agent of the securities in
order to implement the restrictions on transfer established in this Section 1.

                  1.4  Notice  of  Proposed   Transfers.   The  holder  of  each
certificate  representing  Restricted Securities by acceptance thereof agrees to
comply in all respects  with the  provisions  of this Section 1.4.  Prior to any
proposed  sale,  assignment,  transfer  or pledge of any  Restricted  Securities
(other than (i) a transfer not involving a change in beneficial  ownership  (ii)
in transactions  involving the distribution without  consideration of Restricted
Securities by any of the Investors to any of its partners,  or retired partners,
or to the estate of any of its partners or retired partners in a transaction not
involving a change in beneficial ownership,  (iii) a transfer in compliance with
Rule 144,  so long as the Company is  furnished  with  satisfactory  evidence of
compliance  with such Rule, (iv) transfers by any holder who is an individual to
a trust for the benefit of such holder or his family, and (v) transfers by gift,
will or intestate  succession to the spouse,  lineal descendants or ancestors of
any  holder or spouse of a  holder),  unless  there is in effect a  registration
statement under the Act covering the proposed transfer, the holder thereof shall
give  written  notice to the Company of such  holder's  intention to effect such
transfer, sale, assignment or pledge. Each such notice shall describe the manner
and  circumstances  of the  proposed  transfer,  sale,  assignment  or pledge in
sufficient detail, and shall be accompanied,  at such holder's expense by either
(i) an unqualified  written opinion of legal counsel who shall,  and whose legal
opinion  shall be,  reasonably  satisfactory  to the  Company  addressed  to the
Company,  to the effect that the proposed transfer of the Restricted  Securities
may be effected without registration under the Act, or (ii) a "no


                                       -3-








action"  letter  from the  Commission  to the effect  that the  transfer of such
securities without registration will not result in a recommendation by the staff
of the  Commission  that action be taken with  respect  thereto,  whereupon  the
holder  of such  Restricted  Securities  shall  be  entitled  to  transfer  such
Restricted  Securities in accordance  with the terms of the notice  delivered by
the holder to the Company. Each certificate evidencing the Restricted Securities
transferred  as above  provided  shall  bear,  except if such  transfer  is made
pursuant to Rule 144, the  appropriate  restrictive  legend set forth in Section
1.3 above,  except that such certificate shall not bear such restrictive  legend
if in the opinion of counsel for such holder and the Company  such legend is not
required in order to establish compliance with any provision of the Act.

                  1.5      Requested Registration.

                           (a) In case the Company shall receive from Initiating
Holders  a  written   request   that  the  Company   effect  any   registration,
qualification  or  compliance  with  respect  to at least 80% of such  shares of
Registrable Securities the Company will:

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

                               (ii) as soon as practicable, use its best 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 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 the Registrable Securities of any Holder or
Holders joining in such request as are specified in a written  request  received
by the  Company  within 20 days after  receipt of such  written  notice from the
Company;

                  Provided,  however, that the Company shall not be obligated to
take any action to effect any such  registration,  qualification  or  compliance
pursuant to this Section 1.5:

                                       (A) In  any  particular  jurisdiction  in
which the Company  would be required to execute a general  consent to service of
process in effecting such  registration,  qualification or compliance unless the
Company is already subject to service in such  jurisdiction and except as may be
required by the Act;

                                       (B) Prior to the earlier of (i)  February
15,  1999 or (ii)  within six  months of the  effective  date of any  registered
public offering of the Company's stock;

                                       (C) During the period  starting  with the
date  sixty (60) days prior to the  Company's  estimated  date of filing of, and
ending on the date six (6) months  immediately  following the effective date of,
any registration statement pertaining to securities of the Company (other than a
registration  of  securities  in a Rule 145  transaction  or with  respect to an
employee benefit plan), provided


                                       -4-







that the Company is actively  employing in good faith all reasonable  efforts to
cause such registration statement to become effective;

                                       (D) If the  aggregate  offering  price to
the public from the proposed sale of such  Registrable  Securities would be less
than $7,500,000;

                                       (E) After the  Company has  effected  one
such  registrations  pursuant to this Section 1.5(a),  and such registration has
been declared or ordered effective;

                                       (F) If the Company  shall furnish to such
Holders a certificate signed by the President of the Company stating that in the
good faith judgment of the Board of Directors it would be seriously  detrimental
to the Company or its shareholders  for a registration  statement to be filed at
such time,  then the  Company's  obligation to use its best efforts to register,
qualify or comply  under this  Section 1.5 shall be deferred for a period not to
exceed 180 days from the date of receipt of written  request from the Initiating
Holders.

                  Subject to the foregoing  clauses (A) through (F), the Company
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 Initiating Holders.

                           (b) In the  event  that a  registration  pursuant  to
Section 1.5 is for a registered public offering  involving an underwriting,  the
Company  shall so advise the  Holders as part of the notice  given  pursuant  to
Section  1.5(a)(i).  In such  event,  the right of any  Holder  to  registration
pursuant to Section 1.5 shall be conditioned upon such Holder's participation in
the underwriting arrangements required by this Section 1.5, and the inclusion of
such Holder's Registrable Securities in the underwriting to the extent requested
shall be limited to the extent provided herein.

                  The Company  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 Initiating  Holders,  but
subject  to  the  Company's  reasonable  approval.   Notwithstanding  any  other
provision  of  this  Section  1.5,  if  the  managing  underwriter  advises  the
Initiating Holders in writing that marketing factors require a limitation of the
number  of shares  to be  underwritten,  then the  Company  shall so advise  all
holders  of  Registrable  Securities  and the  number of  shares of  Registrable
Securities that may be included in the registration  and  underwriting  shall be
allocated  among all Holders thereof (except those Holders who have indicated to
the Company their decision not to distribute any of their Registrable Securities
through such  underwriting)  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,  the Company or the underwriters may round
the number of shares allocated to any Holder to the nearest 100 shares.



                                       -5-







                  If any Holder of  Registrable  Securities  disapproves  of the
terms of the  underwriting,  such  person  may elect to  withdraw  therefrom  by
written  notice to the Company,  the  managing  underwriter  and the  Initiating
Holders.  The Registrable  Securities and/or other securities so withdrawn shall
also be withdrawn from registration,  and such Registrable  Securities shall not
be  transferred  in a public  distribution  prior to 90 days after the effective
date  of  such  registration,  or  such  other  shorter  period  of  time as the
underwriters may require.

                  1.6      Company Registration.

                           (a) If at any time or from  time to time the  Company
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, the Company will:

                                    (i)  promptly  give to each  Holder  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 20 days after receipt of such written
notice from the Company, by any Holder.

                           (b) If the  registration  of which the Company  gives
notice is for a  registered  public  offering  involving  an  underwriting,  the
Company  shall so advise  the  Holders  as a part of the  written  notice  given
pursuant  to  Section  1.6(a)(i).  In such  event  the  right of any  Holder  to
registration  pursuant to Section 1.6 shall be  conditioned  upon such  Holder's
participation in such  underwriting and the inclusion of Registrable  Securities
in the  underwriting to the extent  provided  herein.  All Holders  proposing to
distribute their securities  through such underwriting  shall (together with the
Company  and the  other  holders  distributing  their  securities  through  such
underwriting)  enter into an  underwriting  agreement in customary form with the
managing   underwriter   selected   for  such   underwriting   by  the  Company.
Notwithstanding  any  other  provision  of this  Section  1.6,  if the  managing
underwriter determines that marketing factors require a limitation of the number
of shares to be underwritten, the managing underwriter may limit the Registrable
Securities or other  securities to be included in such  registration,  provided,
however,  that after the Company's initial firm commitment  underwritten  public
offering no such  limitation  shall reduce the  percentage of such  registration
consisting of Registrable  Securities below 15%. The Company shall so advise all
Holders  and  other  holders   distributing   their  secu  rities  through  such
underwriting  and the  number  of  shares of  Registrable  Securities  and other
securities that may be included in the registration  and  underwriting  shall be
allocated  among all Holders and such other holders in proportion,  as nearly as
practicable,  to the  respective  amounts of  Registrable  Securities  and other
securities  contractually  entitled to registration in the offering held by such
Holders and such other holders at the time of filing the registration statement.
To facilitate the allocation of shares in accordance with the above  provisions,
the Company 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,  he may elect to withdraw therefrom by written notice to the
Company and the managing


                                       -6-







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 90 days  after  the  effective  date of the  registration
statement  relating  thereto,  or  such  other  shorter  period  of  time as the
underwriters may require.

                           (c) The Company  shall have the right to terminate or
withdraw  any  registration  initiated by it under this Section 1.6 prior to the
effectiveness  of such  registration  whether or not any  Holder has  elected to
include securities in such registration.

                  1.7      Registration on Form S-3.

                           (a) If any Holder or Holders request that the Company
file a  registration  statement on Form S-3 (or any successor  form to Form S-3)
for a public  offering of shares of the Regis trable  Securities  the reasonably
anticipated  aggregate  price  to the  public  of  which,  net  of  underwriting
discounts  and  commissions,  would  exceed  $1,000,000,  and the  Company  is a
registrant  entitled to use Form S-3 to register the Registrable  Securities for
such an  offering,  the  Company  shall  use its  best  efforts  to  cause  such
Registrable  Securities  to be  registered  for the offering on such form and to
cause such Registrable  Securities to be qualified in such  jurisdictions as the
Holder or Holders may reasonably request;  provided,  however,  that the Company
shall not be  required to effect  more than two  registrations  pursuant to this
Section 1.7. The substantive provisions of Section 1.5(b) shall be applicable to
a registration initiated under this Section 1.7.

                           (b) Notwithstanding the foregoing,  the Company shall
not be  obligated  to take any action  pursuant to this  Section 1.7: (i) in any
particular  jurisdiction  in which the  Company  would be  required to execute a
general   consent  to  service  of  process  in  effecting  such   registration,
qualification or compliance  unless the Company is already subject to service in
such jurisdiction and except as may be required by the Act; (ii) if the Company,
within ten (10) days of the  receipt of the request of the  initiating  Holders,
gives notice of its bona fide  intention to effect the filing of a  registration
statement with the Commission within ninety (90) days of receipt of such request
(other  than with  respect to a  registration  statement  relating to a Rule 145
transaction,  an offering solely to employees or any other registration which is
not appropriate for the  registration of Registrable  Securities)  provided that
the Company is actively  employing in good faith all reasonable efforts to cause
such  registration  statement  to become  effective;  (iii)  during  the  period
starting with the date sixty (60) days prior to the Company's  estimated date of
filing  of, and ending on the date six (6)  months  immediately  following,  the
effective  date of any  registration  statement  pertaining to securities of the
Company  (other than a registration  of securities in a Rule 145  transaction or
with respect to an employee benefit plan), provided that the Company is actively
employing  in good  faith all  reasonable  efforts  to cause  such  registration
statement  to become  effective;  or (iv) if the Company  shall  furnish to such
Holder a certificate  signed by the President of the Company stating that in the
good faith judgment of the Board of Directors it would be seriously  detrimental
to the Company or its shareholders  for  registration  statements to be filed at
such  time,  then the  Company's  obligation  to use its best  efforts to file a
registration statement shall be deferred for a period not to exceed 90 days from
the receipt of the request to file such registration by such Holder.



                                       -7-







                  1.8  Expenses  of  Registration.   All  Registration  Expenses
incurred in connection  with one  registration  pursuant to Section 1.5 shall be
borne by the Company. All Selling Expenses relating to securities  registered on
behalf of the Holders and all other Registration  Expenses shall be borne by the
Holders  of such  securities  pro rata on the  basis of the  number of shares so
registered.

                  1.9 Registration Procedures. In the case of each registration,
qualification or compliance  effected by the Company pursuant to this Section 1,
the Company  will keep each Holder  advised in writing as to the  initiation  of
each  registration,  qualification  and  compliance  and  as to  the  completion
thereof. At its expense the Company 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 effective for at least
ninety  (90)  days or  until  the  distribution  described  in the  Registration
Statement has been completed;

                           (b) Prepare and file with the SEC such amendments and
supplements to such registration statement and the prospectus used in connection
with  such  registration  statement  as may be  necessary  to  comply  with  the
provisions  of the 1933 Act with respect to the  disposition  of all  securities
covered by such registration statement.

                           (c) Furnish to the Holders  such numbers of copies of
a  prospectus,  including  a  preliminary  prospectus,  in  conformity  with the
requirements of the Act, and such other documents as they may reasonably request
in order to facilitate the disposition of Registrable Securities owned by them.

                           (d) Use its best  efforts to register and qualify the
securities covered by such registration statement under such other securities or
Blue Sky laws of such  jurisdictions  as shall be  reasonably  requested  by the
Holders, provided that the Company 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 states or jurisdictions.

                           (e) In the event of any underwritten public offering,
enter into and perform its obligations under an underwriting agreement, in usual
and customary form, with the managing under writer of such offering. Each Holder
participating  in such  underwriting  shall  also  enter  into and  perform  its
obligations under such an agreement.

                           (f)  Notify  each  Holder of  Registrable  Securities
covered by such  registration  statement at any time when a prospectus  relating
thereto is required to be delivered  under the Act of 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.



                                       -8-







                           (g) Furnish,  at the request of any Holder requesting
registration of Registrable  Securities  pursuant to this Section 1, on the date
that such  Registrable  Securities are delivered to the underwriters for sale in
connection with a registration pursuant to this Section 1, (i) an opinion, dated
such date,  of the counsel  representing  the  Company for the  purposes of such
registration,  in form and substance as is customarily  given to underwriters in
an underwritten public offering,  addressed to the underwriters,  if any, and to
the Holders requesting  registration of Registrable Securities and (ii) a letter
dated such date,  from the independent  accountants of the Company,  in form and
substance as is customarily given by independent  accountants to underwriters in
an underwritten public offering,  addressed to the underwriters,  if any, and to
the Holders requesting registration of Registrable Securities.

                  1.10     Indemnification.

                           (a) The Company will indemnify  each Holder,  each of
its officers and directors and partners, and each person controlling such Holder
within the meaning of Section 15 of the Act, with respect to which registration,
qualification  or compliance  has been effected  pursuant to this Section 1, and
each  underwriter,  if any, and each person who controls any underwriter  within
the meaning of Section 15 of the 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 the Company of any
federal,  state or common law rule or  regulation  applicable  to the Company in
connection  with any such  registration,  qualification  or compliance,  and the
Company will reimburse each such 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 the Company 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 the Company by an instrument
duly executed by such Holder, controlling person or underwriter and stated to be
specifically for use therein.

                           (b) Each Holder will, if Registrable  Securities held
by such Holder are  included in the  securities  as to which such  registration,
qualification  or compliance is being effected,  indemnify the Company,  each of
its  directors  and  officers,  each  underwriter,  if  any,  of  the  Company's
securities  covered by such a registration  statement,  each person who controls
the Company or such underwriter within the meaning of Section 15 of the Act, and
each other such  Holder,  each of its  officers  and  directors  and each person
controlling such Holder within the meaning of Section 15 of the 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


                                       -9-








required to be stated  therein or necessary to make the  statements  therein not
misleading,  and will  reimburse  the Company,  such  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 the Company 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 public  offering price
of the shares sold by such  Holder,  unless such  liability  arises out of or is
based on willful conduct by such Holder.  A Holder will not be required to enter
into any agreement or undertaking in connection with any registration under this
Section 6 providing for any  indemnification or contribution on the part of such
Holder greater than the Holder's obligations under this Section 1.10(b).

                           (c) Each party entitled to indemnification under this
Section 1.10 (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, provided,  however, that the Indemnifying Party
shall bear the expense of independent  counsel for the Indemnified  Party if the
Indemnified Party reasonably  determines that  representation of both parties by
the same counsel would be inappropriate due to actual or potential  conflicts of
interest, 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  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.

                  1.11   Information  by  Holder.   The  Holder  or  Holders  of
Registrable Securities included in any registration shall furnish to the Company
such information  regarding such Holder or Holders,  the Registrable  Securities
held by them and the  distribution  proposed  by such  Holder or  Holders as the
Company may request in writing and as shall be required in  connection  with any
registration, qualification or compliance referred to in this Section 1.

                  1.12 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,  after such time as a public market exists for the Common Stock of
the Company, the Company agrees to use its best efforts to:


                                      -10-








                           (a) Make and keep public  information  available,  as
those terms are  understood  and defined in Rule 144 under the Act, at all times
after the  effective  date that the  Company  becomes  subject to the  reporting
requirements of the Act or the Securities Exchange Act of 1934, as amended.

                           (b) Use its best efforts to file with the  Commission
in a timely manner all reports and other documents required of the Company under
the Act and the  Securities  Exchange Act of 1934, as amended (at any time after
it has become subject to such reporting requirements);

                           (c)  So  long  as a  Purchaser  owns  any  Restricted
Securities  to  furnish  to the  Purchaser  forthwith  upon  request  a  written
statement by the Company as to its compliance with the reporting requirements of
said Rule 144 (at any time after 90 days after the  effective  date of the first
registration statement filed by the Company for an offering of its securities to
the general public),  and of the Act and the Securities Exchange Act of 1934 (at
any time after it has become subject to such reporting requirements),  a copy of
the most  recent  annual or  quarterly  report of the  Company,  and such  other
reports and documents of the Company and other  information in the possession of
or reasonably obtainable by the Company as a Purchaser may reasonably request in
availing itself of any rule or regulation of the Commission allowing a Purchaser
to sell any such securities without registration.

                  1.13 Transfer of Registration  Rights. The rights to cause the
Company to register  securities granted Investor under Sections 1.5, 1.6 and 1.7
may be assigned to a transferee or assignee in  connection  with any transfer or
assignment of  Registrable  Securities by an Investor  provided  that:  (i) such
transfer may  otherwise be effected in  accordance  with  applicable  securities
laws,  and (ii) such assignee or  transferee  acquires at least 80,000 shares of
Registrable  Securities  or the  securities  into  which  they are  convertible.
Notwithstanding  the  foregoing,  the rights to cause the  Company  to  register
securities may be assigned,  in connection with a distribution by such Investor,
to any  partner,  former  partner,  affiliate  or the estate of any such partner
without  compliance  with item (ii) above,  provided  written  notice thereof is
promptly given to the Company.

                  1.14 Standoff  Agreement.  Each Holder agrees, so long as such
Holder  holds at least one  percent  (1%) of the  Company's  outstanding  voting
equity  securities,  in connection with the Company's initial public offering of
the Company's  securities  that, upon request of the Company or the underwriters
managing any  underwritten  offering of the Company's  securities,  not to sell,
make any short sale of, loan, grant any option for the purchase of, or otherwise
dispose of any Common  Stock of the Company  (other  than those  included in the
registration)  without  the  prior  written  consent  of  the  Company  or  such
underwriters,  as the case may be,  for such  period of time (not to exceed  one
hundred eighty (180) days) from the effective date of such  registration  as may
be requested by the underwriters;  provided,  that all other Holders of at least
one percent (1%) of the Company's  outstanding  voting equity securities and all
of the officers  and  directors of the Company who own stock of the Company also
agree to such restrictions.

                  1.15  Amendment  of  Registration  Rights.  With  the  written
consent  of the  holders  of more than 50% of the then  outstanding  Registrable
Securities (including the securities  convertible into Registrable  Securities),
the Company may amend this Section 1, or enter into any agreement with any


                                      -11-










holder or prospective  holder of any securities of the Company which would allow
such holder or  prospective  holder to include such  securities  as  Registrable
Securities under the provisions hereof.

                  1.16  Termination  of  Registration   Rights.   No  Holder  of
Registrable  Securities shall be entitled to exercise any right provided in this
Section  1 after  five  (5)  years  following  the  consummation  of the sale of
securities  pursuant to a registration  statement filed by the Company under the
Act in connection with the initial firm commitment  underwritten public offering
of its securities to the general public.

         2.       Financial Covenants.

                  2.1  Financial  Statements.   For  so  long  as  the  Investor
(including any affiliated entities of the Investor) owns at least 250,000 shares
of Preferred Stock (or Common Stock issued upon conversion thereof) or until the
closing of a public  offering  pursuant to an effective  registration  statement
under the Act, whichever first occurs, the Company shall furnish to the Investor
the following financial statements and reports,  such financial statements to be
prepared  in  accordance  with then  generally  accepted  accounting  principles
consistently applied:

                           (a) as soon as available,  and in any event within 30
days after the end of each month,  an unaudited  balance sheet of the Company as
of the end of such month and an unaudited statement of operations of the Company
for the  portion  of such  fiscal  year  ended  with the last day of such  month
prepared in accordance with generally  accepted  accounting  principles  (except
that no footnotes need be provided) and certified by the chief financial officer
of the Company, subject, however, to normal year-end audit adjustments;

                           (b) as soon as available,  and in any event within 90
days after the end of each fiscal year of the  Company,  a balance  sheet of the
Company as of the end of such fiscal  year,  a statement  of  operations  of the
Company for such fiscal  year,  and a statement of cash flows of the Company for
such fiscal year, all in reasonable  detail and stating in comparative  form the
figures as of the end of such fiscal year and for the  previous  fiscal year and
accompanied by an opinion  addressed to the Company from  independent  certified
public accountants;

                  In the event that the Company at any time  hereafter  shall be
required,  by  law  or by  then  generally  accepted  accounting  principles  to
consolidate its financial statements with those of a subsidiary corporation, the
Company  shall  thereafter  furnish the  financial  statements  required by this
Section  2.1 on a  consolidated  basis,  and the  monthly  and annual  financial
statements  specified  above shall be  furnished  with  consolidating  financial
statements.

                  2.2  Additional  Information.  For so long as the  Investor is
entitled to receive  information under Section 2.1 hereof, the Company shall (i)
furnish to the Investor such information con cerning the Company as the Investor
may from time to time reasonably  request;  (ii) offer the Investor the right to
visit the  properties  of the Company at  reasonable  times,  to  interview  key
employees of the Company at their places of employment  at reasonable  times and
to examine the books of account of the


                                      -12-









Company and to make copies  therefrom;  and (iii)  furnish  the  Investor,  upon
request,  with a complete and correct copy of the minutes of  proceedings of the
shareholders or Board of Directors.

                  2.3 Assignment of Certain  Rights.  The Investor may assign to
any transferee,  other than a competitor of the Company, and after giving notice
to the  Company,  the rights  granted  pursuant to Sections 2.1 and 2.2 provided
such  transferee  acquires at least 250,000 shares of Preferred Stock (or Common
Stock issued upon conversion thereof);  provided,  further that any Investor may
assign to its  constituent  partners,  former partners or the estate of any such
partners, other than a competitor of the Company, the rights granted pursuant to
Sections 2.1 and 2.2.  The total number of shares of Preferred  Stock (or Common
Stock issued upon  conversion) held by the Investor shall be aggregated with any
affil iated entities in order to determine the Investor's eligibility to receive
rights under this Section 2.

         3.       Miscellaneous.

                  3.1 Successors  and Assigns.  The terms and conditions of this
Agreement  shall  inure to the  benefit  of and be binding  upon the  respective
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,  remedies,  obligations,  or
liabilities under or by reason of this Agreement,  except as expressly  provided
in this Agreement.

                  3.2  Governing  Law. This  Agreement  shall be governed by and
construed  under the laws of the State of  California  as applied to  agreements
among  California  residents  entered into and to be performed  entirely  within
California.

                  3.3  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.

                  3.4 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.

                  3.5 Notices. Unless otherwise provided, any notice required or
permitted  under this  Agreement  shall be given in writing  and shall be deemed
effectively  given upon  personal  delivery  to the party to be notified or upon
deposit with the United States Post Office,  by  registered  or certified  mail,
postage  prepaid  and  addressed  to the  party to be  notified  at the  address
indicated for such party on Attachment A, or at such other address as such party
may designate by ten (10) days' advance written notice to the other parties.

                  3.6 Amendment and Waivers. Except as may be otherwise provided
in  Section  1.15,  any  provision  of this  Agreement  may be  amended  and the
observance  thereof may be waived (either generally or in a particular  instance
and either  retroactively  or  prospectively),  with the written  consent of the
Company  and  the  Investors  holding  a  majority  of the  shares  held  by all
Investors.  Any  amendment or waiver  effected in  accordance  with this Section
shall be binding upon all present and future Investors.


                                      -13-















                                      -14-








                  3.7 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 the  Agreement  shall  be
interpreted  as if such  provision  were so excluded and shall be enforceable in
accordance with its terms.

                                                JENNER TECHNOLOGIES


Date:____________________                       By: /s/ ANTHONY E. MAIDA
                                                   -----------------------------
                                                Title: CEO
                                                      --------------------------

                                                HAYDEN LEASON:


Date:____________________                       /s/ HAYDEN LEASON
                                                -----------------
                                                Signature


                                                SERIES A INVESTORS:


Date:____________________                       ________________________________
                                                Name


                                                --------------------------------
                                                Signature





                                      -15-









      Attachment A to First Amended and Restated Investor Rights Agreement
      --------------------------------------------------------------------




Name & Address of Investor                                         List of Registrable Securities
- --------------------------                                         ------------------------------

                                                                      
Hayden Leason                                                 Series A Preferred Stock - 8,000,000 shares
10 Monte Sol
Palmas Del Mar
Puerto Rico


William B. McClatchy 1982 Trust                               Series A Preferred Stock -   150,000 shares
William K. Coblentz and Carl Hoag, Co-Trustees
c/o  Julie Bouchard
Coblenz, Cahen, McCabe & Breyer
222 Kearney Street, 7th Floor
San Francisco, CA  94108


William B. and Susan McClatchy                                Series A Preferred Stock -   150,000 shares
1885 Mountain View Drive
Tiburon, CA  94920


Nancy Donnell Stefansky                                       Series A Preferred Stock -   250,000 shares
27255 Arnold Drive
Sonoma, CA  95476