<PAGE>
                                                                   EXHIBIT 10.15

                           ELITRA PHARMACEUTICALS INC.

                           SECOND AMENDED AND RESTATED
                                VOTING AGREEMENT

     THIS SECOND AMENDED AND RESTATED VOTING AGREEMENT (this "Agreement") is
made and entered into this 18th day of August, 2000 by and among ELITRA
PHARMACEUTICALS INC., a Delaware corporation (the "Company"), those certain
holders of the Company's Common Stock listed on Exhibit A hereto (the "Key
Stockholders") and the persons and entities listed on Exhibit B hereto (the
"Investors").

                                   WITNESSETH:

     WHEREAS, certain of the Investors hold shares of the Company's Series A
Preferred Stock (the "Series A Preferred Stock") and shares of the Company's
Series B Preferred Stock (the "Series B Preferred Stock"), and possess certain
voting rights pursuant to an existing Amended and Restated Voting Agreement
dated as of June 9, 1999 by and among the Company, the Key Stockholders and such
Investors (the "Prior Voting Agreement");

     WHEREAS, the undersigned Investors who hold Series A Preferred Stock and
Series B Preferred Stock hold a majority in interest of the aggregate of the
Series A Preferred Stock and the Series B Preferred Stock held by the Investors,
and such Investors, the Company and such Key Stockholders desire to amend and
restate the Prior Voting Agreement to add the holders of the Company's Series E
Preferred Stock (the "Series E Preferred Stock") as parties thereto;

     WHEREAS, the Key Stockholders are the beneficial owners of an aggregate of
two million five hundred seventy thousand (2,570,000) shares of the Common Stock
of the Company;

     WHEREAS, the Company proposes to sell shares of Series E Preferred Stock
and warrants to purchase shares of Series E Preferred Stock to certain of the
Investors pursuant to the Series E Preferred Stock and Warrant Purchase
Agreement (the "Purchase Agreement") of even date herewith (the "Financing");
and

     WHEREAS, in connection with the consummation of the Financing, the Company,
the Key Stockholders and the Investors have agreed to provide for the future
voting of their shares of the Company's capital stock as set forth below.

     NOW, THEREFORE, in consideration of the premises and for other good and
valuable consideration, the receipt and sufficiency of which are hereby
acknowledged, the parties hereto agree as follows:

1.   VOTING.

     1.1  COMMON SHARES; INVESTOR SHARES.

          (a) The Key Stockholders each agree to hold all shares of voting
capital stock of the Company registered in their respective names or
beneficially owned by them as of the date hereof (and any and all other
securities of the Company legally or beneficially acquired by each

                                       1.
<PAGE>

of the Key Stockholders after the date hereof) (hereinafter collectively
referred to as the "Common Shares") subject to, and to vote the Common Shares in
accordance with, the provisions of this Agreement.

          (b) The Investors each agree to hold all shares of voting capital
stock of the Company now owned or hereinafter acquired by them (including but
not limited to all shares of Common Stock issued upon conversion of the
Company's Series A Preferred Stock, Series B Preferred Stock and Series E
Preferred Stock (including shares of Series E Preferred Stock issued upon
exercise of warrants issued in the Financing)) registered in their respective
names or beneficially owned by them as of the date hereof (and any and all other
securities of the Company legally or beneficially acquired by each of the
Investors after the date hereof) (hereinafter collectively referred to as the
"Investor Shares") subject to, and to vote the Investor Shares in accordance
with, the provisions of this Agreement.

     1.2  ELECTION OF DIRECTORS. On all matters relating to the election of
directors of the Company, the Key Stockholders and the Investors agree to vote
all Common Shares and Investor Shares held by them (or the holders thereof shall
consent pursuant to an action by written consent of the stockholders) so as to
elect members of the Company's Board of Directors as follows:

          (a) Dr. Harry Hixson or such other person serving as Chief Executive
Officer of the Company, or if there is no duly elected Chief Executive Officer,
one (1) individual nominated by the holders of a majority in interest of the
Common Shares;

          (b) Andrew E. Senyei, M.D., or such other person nominated by
Enterprise Partners IV Associates, L.P. and Enterprise Partners IV, L.P. so long
as they hold (combined) not less than one million (1,000,000) Investor Shares
(as adjusted for stock splits, dividends and the like);

          (c) Wende S. Hutton, or such other person nominated by Mayfield
Associates VI and Mayfield VIII so long as they hold (combined) not less than
one million (1,000,000) Investor Shares (as adjusted for stock splits, dividends
and the like);

          (d) Charles Hsu, or such other person nominated by Walden SBIC, L.P.,
WIG-Global Ventures Ptr. Ltd., International Ventures Capital Investment Corp.,
Pacven Walden Ventures IV, L.P. and Pacven Walden Ventures IV so long as they
hold (combined) not less than three million (3,000,000) Investor Shares (as
adjusted for stock splits, dividends and the like); and

          (e) Arnold Oronsky, or such other person nominated by InterWest
Partners VI, L.P. and InterWest Investors VI, L.P. so long as they hold
(combined) not less than three million (3,000,000) Investor Shares (as adjusted
for stock splits, dividends and the like);

          (f) All remaining nominees shall be mutually acceptable to both (i) a
majority in interest of the holders of the Common Shares and (ii) a majority in
interest of the holders of the Investor Shares.

Any vote taken to remove any director elected pursuant to this Section 1.2, or
to fill any vacancy created by the resignation of a director elected pursuant to
this Section 1.2, shall also be subject to the provisions of this Section 1.2.

                                       2.

<PAGE>

     1.3  LEGEND.

          (a) Concurrently with the execution of this Agreement, there shall be
imprinted or otherwise placed, on certificates representing the Common Shares
and the Investor Shares the following restrictive legend (the "Legend"):

                    THE SHARES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO
                    THE TERMS AND CONDITIONS OF AN AMENDED AND RESTATED VOTING
                    AGREEMENT WHICH PLACES CERTAIN RESTRICTIONS ON THE VOTING OF
                    THE SHARES REPRESENTED HEREBY. ANY PERSON ACCEPTING ANY
                    INTEREST IN SUCH SHARES SHALL BE DEEMED TO AGREE TO AND
                    SHALL BECOME BOUND BY ALL THE PROVISIONS OF SUCH AGREEMENT.
                    A COPY OF SUCH VOTING AGREEMENT WILL BE FURNISHED TO THE
                    RECORD HOLDER OF THIS CERTIFICATE WITHOUT CHARGE UPON
                    WRITTEN REQUEST TO THE COMPANY AT ITS PRINCIPAL PLACE OF
                    BUSINESS."

          (b) The Company agrees that, during the term of this Agreement, it
will not remove, and will not permit to be removed (upon registration of
transfer, reissuance of otherwise), the Legend from any such certificate and
will place or cause to be placed the Legend on any new certificate issued to
represent Common Shares or Investor Shares theretofore represented by a
certificate carrying the Legend.

     1.4 SUCCESSORS. The provisions of this Agreement shall be binding upon the
successors in interest to any of the Common Shares or Investor Shares. The
Company shall not permit the transfer of any of the Common Shares or Investor
Shares on its books or issue a new certificate representing any of the Common
Shares or Investor Shares unless and until the person to whom such security is
to be transferred shall have executed a written agreement, substantially in the
form of this Agreement, pursuant to which such person becomes a party to this
Agreement and agrees to be bound by all the provisions hereof as if such person
were a Key Stockholder or Investor, as applicable.

     1.5 OTHER RIGHTS. Except as provided by this Agreement, each Key
Stockholder and Investor shall exercise the full rights of a stockholder with
respect to the Common Shares and the Investor Shares, respectively.

2.   TERMINATION

     2.1 This Agreement shall continue in full force and effect from the date
hereof through the earliest of the following dates, on which it shall terminate
in its entirety:

          (a) the date of the closing of a firmly underwritten public offering
of the Company's Common Stock pursuant to a registration statement filed with,
and declared effective under the Securities Act of 1933, as amended; or

          (b) at such time as the Investors hold less than an aggregate of
2,272,728 shares of Series A Preferred Stock, 10,666,666 shares of Series B
Preferred Stock or 3,076,923

                                       3.
<PAGE>

shares of Series E Preferred Stock (each as adjusted for subsequent stock
splits, stock dividends, recapitalizations and the like); or

          (c) ten (10) years from the date of this Agreement; or

          (d) the date as of which the parties hereto terminate this Agreement
by written consent of a majority in interest of the Investors and a majority in
interest of the Key Stockholders.

3.   MISCELLANEOUS

     3.1 OWNERSHIP. Each Key Stockholder represents and warrants to the
Investors that (a) he now owns the Common Shares, free and clear of liens or
encumbrances (except as provided in the Founders Stock Purchase Agreement to
which such Key Stockholder is a party), and, except for the Prior Voting
Agreement, has not, prior to or on the date of this Agreement, executed or
delivered any proxy or entered into any other voting agreement or similar
arrangement other than one which has expired or terminated prior to the date
hereof, and (b) such Key Stockholder has full power and capacity to execute,
deliver and perform this Agreement, which has been duly executed and delivered
by, and evidences the valid and binding obligation of, such Key Stockholder
enforceable in accordance with its terms.

     3.2 FURTHER ACTION. If and whenever the Common Shares are sold, the Key
Stockholders or the personal representative of the Key Stockholders shall do all
things and execute and deliver all documents and make all transfers, and cause
any transferee of the Common Shares to do all things and execute and deliver all
documents, as may be necessary to consummate such sale consistent with this
Agreement.

     3.3 SPECIFIC PERFORMANCE. The parties hereto hereby declare that it is
impossible to measure in money the damages which will accrue to a party hereto
or to their heirs, personal representatives, or assigns by reason of a failure
to perform any of the obligations under this Agreement and agree that the terms
of this Agreement shall be specifically enforceable. If any party hereto or his
heirs, personal representatives, or assigns institutes any action or proceeding
to specifically enforce the provisions hereof, any person against whom such
action or proceeding is brought hereby waives the claim or defense therein that
such party or such personal representative has an adequate remedy at law, and
such person shall not offer in any such action or proceeding the claim or
defense that such remedy at law exists.

     3.4 GOVERNING LAW. This Agreement, and the rights of the parties hereto,
shall be governed by and construed in accordance with the laws of the State of
California as such laws apply to agreements among California residents made and
to be performed entirely within the State of California.

     3.5 AMENDMENT OR WAIVER. This Agreement may be amended (or provisions of
this Agreement waived) only by an instrument in writing signed by (i) the
Company, (ii) Investors holding a majority in interest of the Investor Shares,
and (iii) Key Stockholders holding a majority in interest of the Common Shares.
Any amendment or waiver so effected shall be binding upon the Company, each of
the parties hereto and any assignee of any such party. Notwithstanding the
foregoing, the consent of a Key Stockholder to any amendment or waiver

                                       4.
<PAGE>

which diminishes such Key Stockholders rights shall not be required if such
person is no longer serving as an employee or director of, or consultant to, the
Company.

     3.6 SEVERABILITY. If any provision of this Agreement is held to be invalid
or unenforceable, the validity and enforceability of the remaining provisions of
this Agreement shall not be affected thereby.

     3.7 SUCCESSORS. This Agreement shall inure to the benefit of and be binding
upon the parties hereto and their respective heirs, successors, assigns,
administrators, executors and other legal representatives.

     3.8 ADDITIONAL SHARES. In the event that subsequent to the date of this
Agreement any shares or other securities (other than any shares or securities of
another corporation issued to the Company's stockholders pursuant to a plan of
merger) are issued on, or in exchange for, any of the Common Shares or Investor
Shares by reason of any stock dividend, stock split, consolidation of shares,
reclassification or consolidation involving the Company, such shares or
securities shall be deemed to be Common Shares or Investor Shares, as the case
may be, for purposes of this Agreement.

     3.9 ADDITIONAL INVESTORS. Notwithstanding anything to the contrary
contained herein, if the Company shall issue additional shares of its Series E
Preferred Stock pursuant to the Purchase Agreement, any purchaser of such shares
of Series E Preferred Stock may become a party to this Agreement by executing
and delivering an additional counterpart signature page to this Agreement and
shall be deemed an "Investor" hereunder.

     3.10 COUNTERPARTS. This Agreement may be executed in one or more
counterparts, each of which will be deemed an original but all of which together
shall constitute one and the same agreement.

     3.11 WAIVER. No waivers of any breach of this Agreement extended by any
party hereto to any other party shall be construed as a waiver of any rights or
remedies of any other party hereto or with respect to any subsequent breach.

     3.12 ATTORNEY'S FEES. In the event that any suit or action is instituted to
enforce any provision in this Agreement, the prevailing party shall be entitled
to all costs and expenses of maintaining such suit or action, including
reasonable attorneys' fees.

     3.13 ENTIRE AGREEMENT. This Agreement and the Exhibits hereto, along with
the Purchase Agreement and each of the Exhibits thereto, constitute the full and
entire understanding and agreement between the parties with regard to the
subjects hereof and thereof and no party shall be liable or bound to any other
in any manner by any representations, warranties, covenants and agreements
except as specifically set forth herein and therein, including those set forth
in the Prior Voting Agreement.

                      [THIS SPACE INTENTIONALLY LEFT BLANK]

                                       5.
<PAGE>

     IN WITNESS WHEREOF, the parties hereto have executed this Second Amended
and Restated Voting Agreement as of the date first above written.

COMPANY:                                 INVESTORS:

ELITRA PHARMACEUTICALS INC.              ENTERPRISE PARTNERS IV, L.P.


/s/ HARRY F. HIXSON, JR.                 /s/ JAMES H. BERGLUND
----------------------------------       ---------------------------------------
By:  Dr. Harry F. Hixson, Jr.            By:  James H. Berglund
Title:  President                        Title:  General Partner


                                         ENTERPRISE PARTNERS IV ASSOCIATES, L.P.


                                         /s/ JAMES H. BERGLUND
                                         ---------------------------------------
                                         By:  James H. Berglund
                                            ------------------------------------
                                         Title:  General Partner
                                               ---------------------------------

                                         MAYFIELD ASSOCIATES FUND III,
                                          a California Limited Partnership

                                         By: MAYFIELD VIII MANAGEMENT, LLC.,
                                              a Delaware Limited Liability
                                              Company, its General Partner


                                         /s/ RUSSELL HIRSCH
                                         ---------------------------------------
                                         By:  Russell Hirsch
                                            ------------------------------------
                                         Title:  General Partner
                                               ---------------------------------

                                         MAYFIELD VIII, a California Limited
                                          Partnership

                                         By: MAYFIELD VIII MANAGEMENT, LLC.,
                                              a Delaware Limited Liability
                                              Company, its General Partner


                                         /s/ RUSSELL HIRSCH
                                         ---------------------------------------
                                         By:  Russell Hirsch
                                             -----------------------------------
                                         Title:  General Partner
                                               ---------------------------------
                                       6.

<PAGE>

                                       WALDEN-SBIC, L.P.

                                       /s/ ARTHUR S. BERLINER
                                       -----------------------------------------
                                       By:  Arthur S. Berliner
                                          --------------------------------------
                                       Title:  General Partner
                                              ----------------------------------


                                       WIG-GLOBAL VENTURES PTE. LTD.

                                       /s/ LIP-BU TAN
                                       -----------------------------------------
                                       By:  Lip-Bu Tan
                                          --------------------------------------
                                       Title:  Director
                                             -----------------------------------

                                       INTERNATIONAL VENTURES CAPITAL INVESTMENT
                                        CORP.

                                       /s/ LIP-BU TAN
                                       -----------------------------------------
                                       By:  Lip-Bu Tan
                                          --------------------------------------
                                       Title:  President
                                             -----------------------------------


                                       PACVEN WALDEN VENTURES IV, L.P.

                                       /s/ LIP-BU TAN
                                       -----------------------------------------
                                       By:  Lip-Bu Tan
                                          --------------------------------------
                                       Title:  Director of Pacven Walden
                                                Management Co., Ltd.
                                                as General Partner of Pacven
                                                Walden Management, II, L.P.
                                                as General Partner of Pacven
                                                Walden Ventures IV, L.P.


                                       PACVEN WALDEN VENTURES IV ASSOCIATES
                                        FUND, L.P.

                                       /s/ LIP-BU TAN
                                       -----------------------------------------
                                       By:  Lip-Bu Tan
                                          --------------------------------------
                                       Title:  Director of Pacven Walden
                                                Management Co., Ltd.
                                                as General Partner of Pacven
                                                Walden Management, II, L.P.
                                                as General Partner of Pacven
                                                Walden Ventures IV Associates
                                                Fund, L.P.


                                       INTERWEST PARTNERS VI, L.P.

                                       By: InterWest Management Partners VI, LLC
                                       Its: General Partner

                                       /s/ ARNOLD ORONSKI
                                       -----------------------------------------
                                       By:  Arnold Oronski
                                          --------------------------------------
                                       Title:   Managing Director
                                             -----------------------------------

                               SIGNATURE PAGE TO
                  SECOND AMENDED AND RESTATED VOTING AGREEMENT


<PAGE>

                                       INTERWEST INVESTORS VI, L.P.
                                       By: InterWest Management Partners VI, LLC
                                       Its: General Partner

                                       /s/ ARNOLD ORONSKI
                                       -----------------------------------------
                                       By: Arnold Oronski
                                          --------------------------------------
                                       Title:   Managing Director
                                              ----------------------------------


                                       GENECHEM TECHNOLOGIES VENTURE FUND, L.P.

                                       /s/ LOUIS LACASSE
                                       -----------------------------------------
                                       By:  Louis Lacasse
                                          --------------------------------------
                                       Title:  President
                                              ----------------------------------


                                       KOFFLER FAMILY, LIMITED PARTNERSHIP

                                       /s/ RICHARD J. BORNSTEIN
                                       -----------------------------------------
                                       By:  Richard J. Bornstein
                                          --------------------------------------
                                       Title:  Manager of G.P.
                                              ----------------------------------


                                       INCYTE GENOMICS, INC.

                                       /s/ ROY A. WHITFIELD
                                       -----------------------------------------
                                       By:  Roy A. Whitfield
                                          --------------------------------------
                                       Title:  Chief Executive Officer
                                              ----------------------------------


                                       /s/ RICHARD J. BORNSTEIN
                                       -----------------------------------------
                                       RICHARD J. BORNSTEIN


                                       /s/ TERRI CHERNICK
                                       -----------------------------------------
                                       TERRI CHERNICK


                                       /s/ DR. HARRY HIXSON
                                       -----------------------------------------
                                       DR. HARRY HIXSON


                                       ALEXANDRIA REAL ESTATE EQUITIES, L.P.
                                       By:  ARE-QRS Corp., a Maryland
                                             corporation, general partner

                                       /s/ LAURIE A. ALLEN
                                       -----------------------------------------
                                       By:  Laurie A. Allen
                                          --------------------------------------
                                       Title:  Senior Vice President, Business
                                                Development and Legal Affairs


                               SIGNATURE PAGE TO
                  SECOND AMENDED AND RESTATED VOTING AGREEMENT

<PAGE>

                                        POLINSKY FAMILY TRUST

                                        /s/ ALEX POLINSKY
                                        ----------------------------------------
                                        By:  Alex Polinsky
                                        Title:  Trustee



                                        DAN VAPNEK LIVING TRUST

                                        /s/ DAN VAPNEK
                                        ----------------------------------------
                                        By:  Dan Vapnek, Trustee


                                        SCHNEIDER TRUST, UTD 1/30/99

                                        /s/ ELAINE B. SCHNEIDER
                                        ----------------------------------------
                                        /s/ JERRY A. SCHNEIDER
                                        ----------------------------------------
                                        By: Elaine B. Schneider and
                                             Jerry A. Schneider
                                           -------------------------------------
                                        Title:  Trustees
                                              ----------------------------------


                                        /s/ MAARTEN CHRISPEELS
                                        ----------------------------------------
                                        MAARTEN CHRISPEELS


                                        BROWN FAMILY TRUST

                                        /s/ MARVIN R. BROWN
                                        ----------------------------------------
                                        By:  Marvin R. Brown
                                           -------------------------------------
                                        Title:   Trustee
                                               ---------------------------------


                                        DENNIS A. MCCONNELL LIVING TRUST


                                        /s/ DENNIS A. McCONNELL
                                        ----------------------------------------
                                        By:  Dennis A. McConnell
                                           -------------------------------------
                                        Title:  Trustee
                                              ----------------------------------


                                        /s/ WILLIAM HUSIC
                                        ----------------------------------------
                                        WILLIAM HUSIC


                                        GOLDBERG FAMILY TRUST UTD 5/8/80


                                        /s/ FRANK M. GOLDBERG
                                        ----------------------------------------
                                        By:  Frank M. Goldberg
                                           -------------------------------------
                                        Title:  Trustee
                                              ----------------------------------

                               SIGNATURE PAGE TO
                  SECOND AMENDED AND RESTATED VOTING AGREEMENT

<PAGE>

                                        PATHO TRUST

                                        /s/ JAMES BECK
                                        ----------------------------------------
                                        By:  James Beck
                                           -------------------------------------
                                        Title:  Administrative Trustee
                                              ----------------------------------


                                        HUTTON LIVING TRUST

                                        /s/ WENDE S. HUTTON
                                        ----------------------------------------
                                        By:  Wende S. Hutton
                                           -------------------------------------
                                        Title:  Trustee
                                              ----------------------------------


                                        BEAR PAW CAPITAL LLC

                                        /s/ ANTHONY J. DELUCA
                                        ----------------------------------------
                                        By:  Anthony J. DeLuca
                                           -------------------------------------
                                        Title:  Manager
                                              ----------------------------------


                                        THE SEARS LIVING TRUST DTD 3/11/91

                                        /s/ LOWELL E. SEARS
                                        ----------------------------------------
                                        By:  Lowell E. Sears
                                           -------------------------------------
                                        Title:  Trustee
                                              ----------------------------------


                                        COMDISCO, INC.

                                        /s/ JILL C. HANSES
                                        ----------------------------------------
                                        By:  Jill C. Hanses
                                           -------------------------------------
                                        Title:  Senior Vice President
                                              ----------------------------------


                                        /s/ STELIOS PAPADOPOULOS
                                        ----------------------------------------
                                        STELIOS PAPADOPOULOS


                                        ----------------------------------------
                                        JUDITH W. ZYSKIND, PH.D.


                                        /s/ R. ALLYN FORSYTH, PH.D.
                                        ----------------------------------------
                                        R. ALLYN FORSYTH, PH.D.


                                        ----------------------------------------
                                        ROGER ALBERT FORSYTH, M.D.


                                        ----------------------------------------
                                        BLAIR LEE HIXSON


                               SIGNATURE PAGE TO
                  SECOND AMENDED AND RESTATED VOTING AGREEMENT


<PAGE>

                                        HARRY F. HIXSON III TRUST

                                        /s/ DENNIS McCONNELL
                                        ----------------------------------------
                                        By:  Dennis McConnell
                                           -------------------------------------
                                        Title:   Trustee
                                               ---------------------------------


                                        CLAIRE-MARIE THERESE HIXSON TRUST

                                        /s/ DENNIS McCONNELL
                                        ----------------------------------------
                                        By:  Dennis McConnell
                                           -------------------------------------
                                        Title:  Trustee
                                               ---------------------------------


                                        ----------------------------------------
                                        ASHLEY HIXSON VEST


                                        ----------------------------------------
                                        MARY HELEN RICHTER


                                        ----------------------------------------
                                        VIRGINIA ANN MCDONALD


                                        GC&H INVESTMENTS

                                        ----------------------------------------
                                        By:
                                           -------------------------------------
                                        Title:
                                              ----------------------------------


                                        VLG INVESTMENTS 1998

                                        ----------------------------------------
                                        By:
                                           -------------------------------------
                                        Title:
                                              ----------------------------------


                                        TECHAMP INTERNATIONAL, L.P.
                                        By:  AMP&A Management, LLC
                                        Its:  General Partner

                                        /s/ illegible signature
                                        ----------------------------------------
                                        By:
                                           -------------------------------------
                                        Title:  Vice President
                                              ----------------------------------

                               SIGNATURE PAGE TO
                  SECOND AMENDED AND RESTATED VOTING AGREEMENT

<PAGE>

                                      U.S. BANCORP PIPER JAFFRAY ECM FUND I, LLC

                                      /s/ JOHN R. JACOBS
                                      ------------------------------------------
                                      By:  John R. Jacobs
                                         ---------------------------------------
                                      Title:  Managing Director
                                            ------------------------------------


                                      YALTA INVESTMENTS, L.P.

                                      /s/ LEV LEYTES
                                      ------------------------------------------
                                      By:  Lev Leytes
                                         ---------------------------------------
                                      Title:  General Partner
                                            ------------------------------------


                                      COOPER HILL PARTNERS, LLC

                                      /s/ ILLEGIBLE SIGNATURE
                                      ------------------------------------------
                                      By:
                                         ---------------------------------------
                                      Title:  CEO
                                            ------------------------------------


                                      PACIFIC VENTURE GROUP II, L.P.
                                      By:  PVG EQUITY PARTNERS II, L.L.C.
                                      Its: General Partner

                                      /s/ RALPH SABIN
                                      ------------------------------------------
                                      By:  Ralph Sabin
                                         ---------------------------------------
                                      Title:  Managing Director
                                            ------------------------------------


                                      PVG ASSOCIATES II, L.P.
                                      By:  PVG EQUITY PARTNERS II, L.L.C.
                                      Its: General Partner

                                      /s/ RALPH SABIN
                                      ------------------------------------------
                                      By:  Ralph Sabin
                                         ---------------------------------------
                                      Title:  Managing Director
                                            ------------------------------------


                                      SENVEST INTERNATIONAL LLC

                                      /s/ RICHARD MASHAAL
                                      ------------------------------------------
                                      By:   Richard Mashaal
                                         ---------------------------------------
                                      Title:  General Partner
                                            ------------------------------------

                               SIGNATURE PAGE TO
                  SECOND AMENDED AND RESTATED VOTING AGREEMENT

<PAGE>

                                      SENVEST MASTER FUND L.P.

                                      /s/ RICHARD MASHAAL
                                      ------------------------------------------
                                      By:   Richard Mashaal
                                         ---------------------------------------
                                      Title:  General Partner
                                            ------------------------------------


                                      /s/ ROBERT MASHAAL
                                      ------------------------------------------
                                      ROBERT MASHAAL





                               SIGNATURE PAGE TO
                  SECOND AMENDED AND RESTATED VOTING AGREEMENT

<PAGE>

                                    EXHIBIT A

                            LIST OF KEY STOCKHOLDERS

Dr. Harry Hixson
Judith W. Zyskind, Ph.D.
R. Allyn Forsyth, Ph.D.
Roger Albert Forsyth, M.D.
Blair Lee Hixson
Harry F. Hixson III Trust
Claire-Marie Therese Hixson Trust
Ashley Hixson Vest
Mary Helen Richter
Virginia Ann McDonald



<PAGE>

                                    EXHIBIT B

                                LIST OF INVESTORS
<TABLE>

<S>                                                                      <C>
Enterprise Partners IV Associates, L.P.                                  PVG Associates II, L.P.
Enterprise Partners IV, L.P.                                             Polinsky Family Trust
Mayfield Associates Fund III                                             Goldberg Family Trust UTD 5/8/80
Mayfield VIII                                                            William Husic
U.S. Bancorp Piper Jaffray ECM Fund I, LLC                               TechAMP International, L.P.
Walden-SBIC, L.P.                                                        Senvest International LLC
WIG-Global Ventures Pte. Ltd.                                            Senvest Master Fund L.P.
International Ventures Capital Investment Corp.                          Robert Mashaal
Pacven Walden Ventures IV, L.P.
Pacven Walden Ventures IV Associates Fund, L.P.
InterWest Partners VI, L.P.
InterWest Investors VI, L.P.
Koffler Family, Limited Partnership
Richard J. Bornstein
Terri Chernick
Dr. Harry Hixson
VLG Investments 1998
GC&H Investments
Incyte Genomics, Inc.
Alexandria Real Estate Equities, L.P.
The Vapnek Living Trust
Schneider Trust, UTD 1/30/99
Maarten Chrispeels
The Brown Family Trust
Dennis A. McConnell Living Trust
Patho Trust
Hutton Living Trust
Bear Paw Capital LLC
The Sears Living Trust Dtd 3/11/91
Comdisco, Inc.
Stelios Papadopoulos
Cooper Hill Partners, LLC
Yalta Investments, L.P.
GeneChem Technologies Venture Fund, L.P.
Pacific Venture Group II, L.P.

</TABLE>