Document:

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                                                                  Exhibit 10.12

                        ADMINISTRATIVE SERVICES AGREEMENT

                                      DATED

                                DECEMBER 9, 1997

                                     BETWEEN

                                  SEPRACOR INC.

                                       AND

                                  VERSICOR INC.

<PAGE>

                        ADMINISTRATIVE SERVICES AGREEMENT

         THIS ADMINISTRATIVE SERVICES AGREEMENT, (this "Agreement") is dated as
of December 9, 1997 between SEPRACOR INC., a Delaware corporation ("SEPRACOR"),
and VERSICOR INC., a Delaware corporation (the "COMPANY").

                                    RECITALS

         A. Sepracor heretofore has provided the Company with information
services, payroll, human resources, employee benefits administration and other
services; and

         B. Sepracor is willing to continue to provide to the Company such
services and the Company desires to obtain such services and assistance from
Sepracor, in each case on the terms and conditions set forth herein.

         NOW, THEREFORE, the parties hereto, intending to be legally bound,
hereby agree as follows:

         1.       SERVICES SUPPLIED.

                  (a) Sepracor hereby agrees to provide or make available the
support and related services that are listed and briefly described in Attachment
A hereto (the "Services"), to the Company in accordance with the terms of this
Agreement. In order to provide for the furnishing of additional services not
listed on Attachment A at the time of execution of this Agreement, Attachment A
may be amended from time to time with the consent of each of Sepracor and the
Company. All Services shall be performed in the manner, to the extent and at a
time substantially consistent with the manner in which Sepracor performs
administrative or other services for its own benefit. Without limiting the
foregoing, Sepracor agrees to consult with representatives of the Company prior
to taking any action material to the provision of Services pursuant to this
Agreement that would constitute a material departure from past practice.

                  (b) In addition, Sepracor will provide such reasonable
assistance to the Company as the Company shall request to efficiently and
expeditiously develop the ability to operate the Company and to perform the
Services provided for hereunder itself.

                  (c) Notwithstanding anything to the contrary in this
Agreement, Company may, at any time, upon thirty (30) days prior written notice
to Sepracor, elect to discontinue receiving one or more of the Services provided
hereunder. Thirty (30) days following receipt of such notice, Sepracor shall
cease to provide such Services to the Company, and the Company's right to
receive such Services under this Agreement shall terminate.

                                       1.
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         2.       TERM.

                  The term of this Agreement shall continue for the period
beginning as of November 1, 1997 and continuing through the earlier to occur of
(i) the close of business on June 30, 1998 or (ii) the close of business of such
date as this Agreement is terminated pursuant to Section 3 hereof.

         3.       TERMINATION.

                  (a) Sepracor may terminate this Agreement if the Company shall
fail to satisfy its payment obligations under this Agreement within thirty (30)
days after receipt of written notice from Sepracor specifying the amount
previously invoiced and remaining due and unpaid and stating its intent to
terminate this Agreement if such amount is not paid within thirty (30) days of
receipt of such notice.

                  (b) The Company may terminate this Agreement at any time upon
thirty (30) days prior written notice to Sepracor.

                  (c) The parties hereto will provide each other mutual
assistance to ensure a smooth transition of each Service upon termination.

         4.       COMPENSATION.

                  The Company shall pay Sepracor for the services set forth in
Attachment A as of the date hereof an amount equal to $6,500 per month plus
direct out of pocket expenses incurred by Sepracor in the performance of this
Agreement. Such amount per month shall be adjusted upon mutual agreement of the
Company and Sepracor upon modifications to Attachment A.

         5.       INVOICING AND PAYMENT.

                  Sepracor shall invoice the Company monthly for services
supplied hereunder and payment shall be due in advance on the first day of such
month.

         6.       RIGHT TO AUDIT.

                  For purposes of verifying the proper performance of services
by Sepracor and its agents hereunder, the Company shall be entitled, on
reasonable notice and during normal business hours to inspect and copy the
records of Sepracor and its agents providing services hereunder as may be
reasonably necessary for such purpose. All such records shall be retained by
Sepracor and made available to the Company for three years following the date to
which such records relate and shall remain the property of Sepracor.
Notwithstanding the foregoing, the Company shall not have access to personnel
records of Sepracor relating to individual performance or evaluation records or
medical histories.

                                       2.
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         7.       INDEPENDENT CONTRACTOR STATUS.

                  Sepracor and its agents shall be independent contractors with
respect to services they provide to the Company hereunder. Sepracor and its
agents shall not hold themselves out to third parties as having the power to
contractually bind the Company with respect to any matter, and shall be
responsible for their own employees, and such employees shall not be deemed to
have an employment relationship with the Company. Notwithstanding the above, the
Company hereby appoints Robert Scumaci, or his replacement mutually acceptable
to the Company and Sepracor, as agent for the Company with respect to issuing
accounts payable checks, filing tax returns, authorizing payroll, and
authorizing the investment of the Company's proceeds in accounts or instruments
maintained by Fleet National Bank, and authorizing the disbursement of funds
related thereto.

         8.       BOOKS AND RECORDS.

                  Sepracor's books and records with respect to the Services
("Books and Records") shall be kept at Sepracor's offices located at 111 Locke
Drive, Marlborough, MA 01752. The Books and Records shall be made available for
the Company or the Company's representatives' inspection and copying at all
times during regular office hours. Sepracor shall not be required to maintain
the Books and Records for more than six years after termination of this
Agreement.

         9.       TRANSFER OF RECORDS.

                  Sepracor shall deliver to the Company, within a reasonably
prompt time following the date of this Agreement, all of the Company's corporate
records and files held by Sepracor.

         10.      COMPLIANCE WITH LAWS.

         Each of the Company and Sepracor shall comply with any and all
applicable statutes, rules, regulations, orders or restrictions of any domestic
or foreign government, or instrumentality or agency thereof, in respect of the
conduct of their activities in the fulfillment of their obligations under this
Agreement.

         11.      CONFIDENTIALITY, RECORDS.

                  (a) PROPRIETARY INFORMATION. All information furnished or
disclosed by one party (a "Disclosing Party") to the other party (a "Receiving
Party") in connection with the negotiation or performance of this Agreement,
including but not limited to trade secrets, cost and pricing information,
computer program, technique, design, drawing, prototype, formula or test data,
relating to any research project, work in process, future development,
engineering, manufacturing, marketing, servicing, financing or personnel matter
shall be deemed "Proprietary Information;" PROVIDED, HOWEVER, that the term
"Proprietary Information" shall not be deemed to include information which the
Receiving Party can demonstrate by competent written proof:

                                       3.
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(a) is now, or hereafter becomes, through no act or failure to act on the part
of the receiving party, generally known or available; (b) is known by the
Receiving Party at the time of receiving such information, as evidenced by its
records; (c) is hereafter furnished to the receiving party by a third party, as
a matter of right and without restriction on disclosure; or (d) is the subject
of a written permission to disclose by the Disclosing Party.

                  (b) USE AND HANDLING OF PROPRIETARY INFORMATION. The Receiving
Party shall maintain all Proprietary Information in trust and confidence and
shall use at least the same degree of care regarding this information as it uses
with respect to its own Proprietary Information to prevent it unauthorized
disclosure, use or publication. The Receiving Party may use such Proprietary
Information only to the extent required to accomplish the intent of this
Agreement. The Receiving Party shall not use the Proprietary Information for any
purpose or in any manner which would constitute a violation of any laws or
regulations.

                  (c) OWNERSHIP OF PROPRIETARY INFORMATION. All Proprietary
Information (including all copies thereof) of a party hereto shall at all times
remain the property of such Disclosing Party. No rights or licenses to
trademarks, inventions, copyrights or patents are implied or granted under this
Agreement.

                  (d) PERMITTED DISCLOSURE. A party may disclose Proprietary
Information to its professional advisors, and may disclose such information if
such disclosure is in response to a valid order of a court or other governmental
body of the United States or any political subdivision thereof, provided,
however, that the Receiving Party shall first have given notice to the
Disclosing Party and shall have made a reasonable effort to obtain a protective
order requiring that the Proprietary Information so disclosed be used only for
the purposes for which the order was issued; or is otherwise required by law.

                  (e) INJUNCTIVE RELIEF. Each party hereby acknowledges and
agrees that in the event of any breach of this Agreement by a Receiving Party,
including, without limitation, the actual or threatened disclosure of
Proprietary Information without the prior express written consent of the
Disclosing Party, the Disclosing Party will suffer an irreparable injury, such
that no remedy at law will afford it adequate protection against, or appropriate
compensation for, such injury. Accordingly, in the event of any breach or
threatened breach by a Receiving Party of any provisions of this Section 11, the
Disclosing Party shall, in addition to all other remedies available to it, be
entitled to specific performance of the Receiving Party's obligations under this
Agreement.

         12.      NONASSIGNMENT; PARTIES IN INTEREST.

                  No party hereto may assign its rights or its duties hereunder
without the prior written consent of the other party hereto; PROVIDED, HOWEVER,
that Sepracor may delegate its duties hereunder to any of its agents or
affiliates. This Agreement shall inure to the benefit of and be binding upon
Sepracor, the Company and their successors and assigns.

                                       4.
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         13.      SURVIVAL.

                  The provisions of Sections 4, 5, 6, 8 and 11 shall survive
the any termination of this Agreement.

         14.      GOVERNING LAW.

         This Agreement shall be governed in all respects by the laws of the
State of Delaware, without giving effect to conflicts of law principles.

         15.      FORCE MAJEURE.

                  In the event that a party's performance under this Agreement,
other than the Company's obligations to make payments, shall be interrupted or
delayed by the occurrence of any event beyond the reasonable control of such
party, then such party shall be excused from performance during the period of
time when the interruption occurred.

         16.      NOTICES.

                  All notices, requests, and other communications to any party
hereunder shall be in writing (including telecopy or similar writing) and shall
be given,

                  IF TO SEPRACOR:

                           Sepracor Inc.
                           111 Locke Drive
                           Marlborough, MA 01752
                           Attn: President
                           Fax: (508) 357-7494

                  IF TO THE COMPANY:

                           Versicor Inc.
                           34790 Ardentech Court
                           Fremont, CA 94555
                           Attn: Chief Executive Officer
                           Fax: (510) 739-3050

                           with a copy (not constituting notice) to:

                           Andrei M. Manoliu
                           Cooley Godward LLP
                           Five Palo Alto Square

                                       5.

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                           3000 El Camino Real
                           Palo Alto, CA 94306-2155
                           Fax: (650) 857-0663

         Unless otherwise provided, any notice required or permitted under this
Agreement shall be given in writing and shall be deemed effective (i) if
personally delivered, at the time delivered by hand, (ii) if delivered by
facsimile transmission, upon confirmation of transmission, (iii) if by courier,
on the business day such courier guarantees delivery, and (iv) if delivered by
U.S. Mail, seven business days after deposit in the U.S. Mail, postage prepaid.

         17. INTEGRATION

                  This Agreement supersedes all prior negotiations, commitments
and rights pertaining to the subject matter hereof.

         18. AMENDMENTS

             This Agreement may not be modified or amended except by a written
agreement signed by the parties hereto.

         19. LIMITATION OF LIABILITY. The liability of Sepracor to the Company
for any loss or damage, whether direct or indirect, arising in connection with
providing the Services to the Company shall not exceed the total amount billed
or billable to the Company for the particular Service, or part thereof, which
gave rise to the loss or damage. In no event will either party be liable to the
other hereunder for indirect, consequential or incidental damages, including
without limitation loss of profits.

         20. COUNTERPARTS

             This Agreement may be executed in two or more counterparts, each of
which shall be an original, with the same effect as if the signatures thereto
were upon the same instrument. This Agreement shall become effective when each
party hereto shall have received a counterpart hereof signed by their other
parties hereto.

                                       6.
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         IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be
executed by their respective authorized officers as of the date first above
written.

                                  SEPRACOR INC.

                                  By:      /s/ Timothy J. Barberich
                                           ---------------------------------
                                           Name:    Timothy J. Barberich
                                           Title:   President & CEO

                                  VERSICOR INC.

                                  By:       /s/ George F. Horner III
                                           ---------------------------------
                                           Name: George F. Horner III
                                           Title: President and CEO

                        ADMINISTRATIVE SERVICES AGREEMENT

<PAGE>

<TABLE>
<CAPTION>
                                  ATTACHMENT A

                                 HUMAN RESOURCES
================================================================================
FUNCTION/LOCATION               DESCRIPTION OF SERVICES TO BE PROVIDED
--------------------------------------------------------------------------------
<S>                             <C>
COMPENSATION                    BASE SALARY COMPONENTS:
                                -job listings; titles; codes
                                -salary & job analysis
                                -maintenance of systems
BENEFITS                        401(k) PLAN ADMINISTERED BY FIDELITY
                                -administration
                                -recordkeeping
                                -analysis
                                -reporting
                                OPTION PLAN:
                                -administration
                                -recordkeeping
                                -analysis
                                -reporting
                                ALL OTHER PLANS: MEDICAL, DENTAL, STD,
                                LTD, FLEXIBLE SPENDING, LIFE, AD & D, EAP
                                -administration
                                -cost of benefits
                                -recordkeeping
                                -analysis
                                -reporting

HR OPERATIONS                   EMPLOYEE RECORD KEEPING AND SERVICES:
                                -data entry
                                -processes
                                -employee data
--------------------------------------------------------------------------------

                                      A-1
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================================================================================
FUNCTION/LOCATION                    DESCRIPTION OF SERVICES TO BE PROVIDED
--------------------------------------------------------------------------------
                                     -employee verification
                                     -employee records and files
                                     -payroll system interface
                                     -stock administration system interface
                                     -policies and procedures as currently
                                      exist

INSURANCE                            -general liability to be administered
                                      and billed by William Gallagher
                                     -key management
</TABLE>

                                      A-2
<PAGE>

<TABLE>
<CAPTION>
                                                 FINANCIAL
================================================================================
FUNCTION/LOCATION               DESCRIPTION OF SERVICES TO BE PROVIDED
--------------------------------------------------------------------------------
<S>                             <C>
ACCOUNTING CENTERS
                                -Accounting
                                -General Ledger
                                -Accounts Receivable
                                -Employee Receivables
                                -Accounts Payable
                                -Employee Expense Reimbursement
                                -fixed Assets
                                -BSA Support
                                -Payroll
                                -Accounting Policy and Procedures as
                                 currently exist
TAX                              Performed by Coopers & Lybrand and
                                 administered by Sepracor
                                -Tax Preparation & Filings
                                -Tax Consultation
--------------------------------------------------------------------------------

                                      A-3
<PAGE>

                                               FACILITIES
================================================================================
FUNCTION/LOCATION                DESCRIPTION OF SERVICES TO BE PROVIDED
--------------------------------------------------------------------------------
MANAGEMENT INFORMATION
SYSTEMS                          General Consulting (only)
--------------------------------------------------------------------------------
</TABLE>

                                      A-4<PAGE>
                                                                  Exhibit 10.17

                              [SEPRACOR LETTERHEAD]

                                 PROMISSORY NOTE

$200,000.00                                                        May 15, 1997

     FOR VALUE RECEIVED, the undersigned Richard J. White, Ph.D., with an
address of 7750 Country Lane, Pleasanton, CA 94588 (hereinafter referred to as
the "Borrower"), promises to pay to the order of Versicor Inc. (together with
any subsequent holders of this Note, the "Lender"), at its office at 111 Locke
Drive, Marlborough, Massachusetts 01752, or at such other place as the Lender
may from time to time designate in writing, the principal sum of:

                          Two Hundred Thousand DOLLARS

     This note is non interest bearing and employee is responsible for imputed
taxes both federal and state tax.

     If not sooner paid, all outstanding principal and accumulated interest
shall be paid to the Lender on the earlier of (a) May 15, 2002 (b) voluntary
termination of employment (c) involuntary termination for cause (d) sale
conveyance, alienation or other transfer of residence at 7750 Country Lane,
Pleasanton, CA 94588 (e) the refinancing of any loan secured by Deed of Trust on
the principal residence senior to Deed of Trust securing borrower's obligation
pursuant to this Note.

     This Note may be prepaid, in whole or from time to time in part, at
anytime, without premium or penalty.

     This Note will be forgiven, including interest, if Richard J. White, Ph.D.,
is involuntarily terminated without cause within the first three years of start
date.

     All payments hereunder shall be payable in lawful money of the United
States which shall be legal tender for public and private debts at the time of
payment.

     It is expressly agreed that the occurrence of any one or more of the
following shall constitute an "Event of Default" hereunder: (a) failure to pay
upon termination of employment (b) failure to pay note on expiration. If any
such Event of Default hereunder shall occur, the Lender may, at its option,
declare to be immediately due and payable the then outstanding principal balance
under this Note, and all other amounts payable to the Lender hereunder, shall
become and be due and payable immediately. The failure of the Lender to exercise
said option to accelerate shall not constitute a waiver of the right to exercise
the same at any other time.

     The Borrower will pay on demand all costs and expenses, including
reasonable attorneys' fees, incurred or paid by the Lender in enforcing or
collecting any of the obligations of the Borrower hereunder. The Borrower agrees
that all such costs and expenses and all other expenditures by the Lender on
account hereof, other than advances of principal, which are not reimbursed by
the Borrower immediately upon demand, all amounts due under this Note after
maturity, and any amounts due hereunder if an Event of Default shall occur
hereunder, shall bear interest at a fluctuating per annum rate equal to the sum
of the Prime Rate from time to time in effect plus five percent, but in no event
more than the maximum rate of interest then permitted by law (the "Default
Rate"), until such expenditures are repaid or this Note and such amounts as are
due are paid to the Lender.

<PAGE>

     This Note is secured by Borrowers stock options in Versicor Inc., and by
Deed of Trust Exhibit A on the property owned at 7750 Country Lane, Pleasanton,
CA 94588 (as from time to time amended and in effect, the "Security") No sale
transfer or assignment of said stock options can be made without the express
written consent of the President and CEO of Sepracor or Versicor.

     All notices required or permitted to be given hereunder shall be in writing
and shall be effective when mailed, postage prepaid, by registered or certified
mail, addressed in the case of the Borrower and the Lender to them at the
address set forth above, or to such other address as either the Borrower or the
Lender may from time to time specify by like notice.

     All of the provisions of this Note shall be binding upon and inure to the
benefit of the Borrower and the Lender and their respective successors and
assigns. If there is more than one undersigned Borrower, the obligations of each
Borrower shall be joint and several. This Note shall be governed by and
construed in accordance with the laws of The Commonwealth of Massachusetts.

     The Borrower hereby consents to any extension of time of payment hereof,
release of all or any part of the security for the payment hereof, or release of
any party liable for this obligation, and waives presentment for payment,
demand, protest and notice of dishonor. Any such extension or release may be
made without notice to the Borrower and without discharging its liability.

IN WITNESS WHEREOF, the Borrower has executed and delivered this Note, on May
15, 1997.

/s/ GEORGE F. HORNER, III              /s/ RICHARD J. WHITE, PH.D.
------------------------------         ---------------------------------------
George F. Horner, III                  Richard J. White, Ph.D.
CEO                                    Senior Vice President Discovery Biology

                                       /s/ ANGELA R. WHITE
                                       ---------------------------------------
                                       Angela R. White

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