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                                                                 Exhibit 10.1(d)


                              TAX SHARING AGREEMENT

         This TAX SHARING AGREEMENT (this "Agreement") is entered into effective
as of the Closing Date (as hereinafter defined), by and between Athena
Neurosciences, Inc., a Delaware corporation ("Parent") and Athena Diagnostics,
Inc., a Delaware corporation ("Diagnostics").

                                    RECITALS
                                    --------

         WHEREAS, Parent and Diagnostics have been members of an affiliated
group of corporations of which Parent is the common parent within the meaning of
Section 1504(a) of the Code (the "Athena Group"), and the members of the Athena
Group have filed United States federal income tax returns on a consolidated
basis pursuant to Section 1501 of the Code;

         WHEREAS, Diagnostics and certain of its Affiliates have joined in the
filing of certain combined, consolidated, unitary, or other similar United
States state, local, or other income tax returns (the "Combined Income Tax
Returns"), and each group filing such a return that includes Diagnostics and at
least one of Parent or an Affiliate of Parent other than Diagnostics is
hereinafter referred to as "Combined Group";

         WHEREAS, following the closing of an initial public offering of the
common stock of Diagnostics, Diagnostics will not be a member of the Athena
Group; and

         WHEREAS, Parent and Diagnostics wish to provide for the allocation of
responsibilities, liabilities and benefits relating to or affecting Taxes (as
hereinafter defined) paid or payable by members of the Athena Group for all
taxable periods beginning on or before the Closing Date and to provide for
certain other matters.

         NOW, THEREFORE, in consideration of the premises, and of the covenants
and agreements set forth herein, the parties hereto hereby agree as follows:

                                    ARTICLE I

                                   DEFINITIONS

         Section 1.01. General.
                       -------

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

         "Affiliate" shall mean, with respect to any specified person, any other
person directly or indirectly controlling or controlled by, or under direct or
indirect common control with, such specified person. For purposes of this
definition, "control," when used with respect to

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any person, means the power to direct the management and policies of such
person, directly or indirectly, whether through the ownership of voting
securities, by contract or otherwise; and the terms "controlling" and
"controlled" shall have meanings correlative to the foregoing.

         "Agreement" shall have the meaning set forth in the Preamble.

         "Closing Date" shall mean the date on which the closing of the initial
public offering of the common stock of Diagnostics occurs.

         "Code" shall mean the U.S. Internal Revenue Code of 1986, as amended,
and shall include corresponding provisions of any subsequently enacted federal
tax laws.

         "Combined Group" shall have the meaning set forth in the Recitals.

         "Combined Income Tax Return" shall have the meaning set forth in the
Recitals.

         "Combined Income Taxes" shall have the meaning set forth in the Section
3.01(b) hereof.

         "Final Determination" shall mean the final resolution of liability for
any Tax for a taxable period, (i) by IRS Form 870 or 870-AD (or any successor
form thereto), on the date of the final acceptance by or on behalf of a party
thereto, or by a comparable form under the laws of another jurisdiction; except
that a Form 870 or 870-AD or comparable form that reserves (whether by its terms
or by operation of law) the right of the taxpayer to file a claim for refund
and/or the right of taxing authority to assert a further deficiency shall not
constitute a Final Determination; (ii) by a decision, judgment, decree, or other
order by a court of competent jurisdiction, which has become final and
unappealable; (iii) by a closing agreement or accepted offer in compromise under
Section 7121 or 7122 of the Code, or comparable agreement under the laws of
another jurisdiction; (iv) by any allowance of a refund or credit in respect of
an overpayment of Tax, but only after the expiration of all periods during which
such refund may be recovered (including by way of offset) by the Tax imposing
jurisdiction; or (v) by any other final disposition, including by reason of the
expiration of the applicable statute of limitations or by mutual agreement of
the parties.

         "Forwarding Responsibilities" shall have the meaning set forth in
Section 4.03 hereof.

         "Governmental Entity" shall mean the United States, any State, the
District of Columbia, or any local government entity, any court, agency,
authority, board, bureau, commission, department, possession, regulatory or
administrative body, office or instrumentality of any nature whatsoever of any
governmental unit, whether federal, state, parish, county, district,
municipality, city, political subdivision or otherwise, domestic or foreign.



                                       2

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         "Income Tax" shall mean a Tax imposed on gross or net income or any
franchise Tax.

         "Income Tax Return" shall mean a Tax Return required to be filed in
respect of any Income Tax.

         "Indemnified Amount" shall have the meaning set forth in Section
4.03(a) hereof.

         "Indemnitee" shall have the meaning set forth in Section 4.02 hereof.

         "Indemnitor" shall have the meaning set forth in Section 4.02 hereof.

         "Other U.S. Tax Return" shall have the meaning set forth in Section
2.02(c) hereof.

         "Post-Closing Taxable Period" shall mean any taxable period beginning
after the Closing Date.

         "Pre-Closing Taxable Period" shall have the meaning set forth in
Section 2.02(a) hereof.

         "Proceeding" shall have the meaning set forth in Section 4.04(a)
hereof.

          "Tax" shall mean any tax, impost, duty, levy or other governmental
charge imposed by any Governmental Entity, and without limiting the generality
of the foregoing, shall include income, sales, use, ad valorem, gross receipts,
license, value added, franchise, transfer, recording, withholding, payroll,
employment, excise, occupation, unemployment insurance, social security,
business license, business organization, stamp, environmental, premium tax,
property tax, and commercial rent and occupancy tax, together with any related
interest, penalties and additions to any such tax, or additional amounts imposed
by any taxing authority.

         "Tax Benefit" shall mean the amounts by which Taxes of a person are
reduced as a result of a deduction or other tax item.

         "Tax Deficiency" shall mean an assessment of Tax as a result of a Final
Determination.

         "Tax Return" shall mean any return, filing, questionnaire, information
return or other document required to be filed, including requests for extensions
of time, filings made with estimated tax payments, claims for refund and amended
returns that may be filed, for any period with any taxing authority in
connection with any Tax or Taxes (whether or not a payment is required to be
made with respect to such filing).

         Section 1.02. Interpretation. The descriptive headings herein are
                       --------------
inserted for convenience or reference only and are not intended to be part of or
to affect the meaning or


                                       3

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interpretation of this Agreement. For all purposes of this Agreement, except as
otherwise expressly provided, (i) the enumeration of one or more items following
the term "including" shall not be interpreted as excluding any items not so
enumerated, (ii) defined terms shall include the plural as well as the singular,
(iii) all references to "Articles," "Sections" or other subdivisions are to
designated Articles, Sections and other subdivisions of the body of this
Agreement, (iv) pronouns of either gender or neuter shall include, as
appropriate, the other pronoun forms, and (v) the words "herein," "hereof" and
"hereunder" and other words of similar import refer to this Agreement as a whole
and not to any particular Article, Section or other subdivision.

                                   ARTICLE II

                              FILING OF TAX RETURNS

         Section 2.01. Manner of Filing. Subject to the provisions of this
                       ----------------
Agreement, all decisions relating to the preparation of Tax Returns shall be
made by the party responsible under this Agreement for such preparation. Each
party to this Agreement will provide a copy of each Tax Return (or appropriate
portions thereof) filed after the Closing Date to any other party to this
Agreement to the extent such return relates to a Tax liability or related
indemnification liability of the other party.

         Section 2.02. Pre-Closing Taxable Period Tax Returns.
                       --------------------------------------

         (a) U.S. Consolidated Federal Income Tax Returns. The U.S. consolidated
             --------------------------------------------
federal income Tax Returns for the Athena Group required to be filed for all
taxable periods beginning on or before the Closing Date (each, a "Pre-Closing
Taxable Period") shall be prepared and filed by Parent.

         (b) Combined U.S. State and Local Tax Returns. All Combined Income Tax
             -----------------------------------------
Returns with respect to a Combined Group required to be filed for a Pre-Closing
Taxable Period shall be prepared and filed by Parent.

         (c) Other U.S. Tax Returns. Any other U.S. federal, state or local Tax
             ----------------------
Return (each, an "Other U.S. Tax Return") not referred to in paragraphs (a) or
(b) of this Section 2.02, including but not limited to Tax Returns in respect of
sales and use Tax, commercial rent and occupancy Tax, state and local property
Tax, federal excise Tax, state premium Tax, payroll Tax and withholding Tax,
required to be filed for a Pre-Closing Taxable Period, that has not been filed
prior to the Closing Date, shall be prepared and filed by the party responsible
under the law of the taxing jurisdiction.


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                                   ARTICLE III

                               LIABILITY FOR TAXES

         Section 3.01. Pre-Closing Taxable Period Tax Liabilities.
                       ------------------------------------------

         (a) Pre-Closing Taxable Period Consolidated U.S. Federal Income Tax
             -------------------------------------------------------------------
Liabilities. Parent shall pay to the U.S. Internal Revenue Service all Taxes due
-----------
in respect of the consolidated U.S. federal income tax liability of the Athena
Group for all Pre-Closing Taxable Periods. Notwithstanding the foregoing,
Diagnostics will pay to Parent, and will indemnify and hold harmless Parent and
its Affiliates from, any and all liability in respect of the federal Tax
liability of Diagnostics for any Pre-Closing Taxable Period and shall deliver to
Parent a bank check payable to Parent for the amount of the federal Tax
liability of Diagnostics not less than five (5) business days prior to each due
date for a payment by Parent of consolidated U.S. federal income Tax for any
such period.

         (b) Pre-Closing Combined U.S. State and Local Income Tax Liabilities.
             ----------------------------------------------------------------
Parent shall pay to the appropriate taxing authority all Taxes due with respect
to any Combined Income Tax Return ("Combined Income Taxes") for any Pre-Closing
Taxable Period. Notwithstanding the foregoing, Diagnostics will pay to Parent,
and will indemnify and hold Parent and its Affiliates harmless from, any Tax
liability of Diagnostics in respect of any Pre-Closing Taxable Period, and
within five (5) days prior to each due date for a payment by Parent of such Tax,
shall deliver to Parent a bank check made out to Parent for such amount.

         (c) Other Taxes for Pre-Closing Taxable Periods. The liability for the
             -------------------------------------------
payment of all other Taxes that fall due in respect of all Pre-Closing Taxable
Periods shall be allocated to the party liable for such Taxes under the law of
the taxing jurisdiction.

         (d) Determination of Tax Liabilities of Diagnostics. Except as provided
             -----------------------------------------------
in Section 3.04, for purposes of subsections (a) and (b) of this Section 3.01,
the amounts treated as due to Parent with respect to Tax liabilities of
Diagnostics shall be the amounts of Taxes that would have been due from
Diagnostics had Diagnostics been a separate stand-alone taxpayer for the
relevant taxable period and not a member of the Athena Group or Combined Group.

         Section 3.02. Sharing of Material Information. Whenever any party
                       -------------------------------
hereto is required to make any of the calculations or determinations referred to
in this Article III, such party shall provide the other party with (i) a copy of
any material calculations or determinations as soon as is practicable after such
calculations or determinations have been made, and prior to the applicable Tax
Return being filed, sufficient to enable the other party to verify mathematical
accuracy and (ii) if requested by the other party, access during reasonable
business hours to copies of any Tax Return, report or other statement sufficient
to enable the other party to verify reasonably consistent treatment with prior
years.


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         Section 3.03. Redetermined Tax Liabilities.
                       ----------------------------

         (a) Pre-Closing Taxable Period Federal Consolidated Tax Returns. In the
             -----------------------------------------------------------
case of any Final Determination regarding a Pre-Closing Taxable Period
consolidated federal income Tax Return of the Athena Group, any Tax Deficiency
shall be paid to the U.S. Internal Revenue Service by Parent. Diagnostics shall
pay to Parent as its allocable share of Tax respecting any Final Determination
the excess of (x) Diagnostics' allocable share of Tax, determined under the
principles of Section 3.01(d), recomputed to take into account the Final
Determination, over (y) Diagnostics' allocable share of Tax as determined using
the most recent prior computation (either the original computation or a
re-computation generated in respect of a prior Final Determination). Whenever
there is an adjustment or recomputation, whether or not there is a Tax
Deficiency or Tax refund or whether or not a payment is required to or from the
appropriate taxing authority, Diagnostics shall make payments to Parent or
receive payments from Parent based upon the principles of Section 3.01(d).

         (b) State and Local Tax Returns and Other Tax Returns. In the case of
             -------------------------------------------------
any Final Determination or other adjustment or recomputation regarding a
Combined Income Tax Return for a Pre-Closing Taxable Period, any Tax Deficiency
shall be paid to the appropriate taxing authority by Parent, and Diagnostics
shall remit to Parent its allocable share of any such Tax Deficiency according
to the principles of Section 3.03(a) above. In the case of any Final
Determination regarding an Other U.S. Tax for a Pre-Closing Taxable Period, any
Tax Deficiency shall be paid to the appropriate taxing authority by the party
that is liable for the payment of such tax pursuant to this Agreement.

         Section 3.04. Tax Benefit of Elan Options. Diagnostics agrees to pay to
                       ---------------------------
Parent the amounts of any Tax Benefits that Diagnostics receives with respect to
any Pre-Closing Taxable Period or Post-Closing Taxable Period as a result of
Elan Corporation, plc stock options held or exercised by employees of
Diagnostics (the "Elan Option Tax Benefits") and any additional amounts that may
be necessary such that after subtraction of all Taxes imposed on Parent with
respect to payments received from Diagnostics pursuant to this Section 3.04
(including payments of additional amounts) Parent shall retain an amount equal
to the Elan Option Tax Benefits.

                                   ARTICLE IV

           INDEMNITY, TAX NOTICES, AUDITS AND EXCHANGE OF INFORMATION

         Section 4.01. Indemnity for Breach. Parent shall be liable for and
                       --------------------
shall indemnify, defend and hold harmless Diagnostics from and against any
payment required to be made as a result of the breach by Parent of any covenant
or agreement under this Agreement. Diagnostics shall be liable for and shall
indemnify, defend and hold harmless Parent and its


                                       6

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Affiliates from and against any payment required to be made as a result of the
breach by Diagnostics of any covenant or agreement under this Agreement.

         Section 4.02. Notice of Indemnity Issue. Whenever Parent or Diagnostics
                       -------------------------
becomes aware of the existence of an issue that could give rise to a claim by it
for indemnification under this Agreement (the party being entitled to such
indemnity being referred to as an "Indemnitee"), such party shall in good faith
promptly give notice of such issue to such other party (hereinafter the
"Indemnitor") and forward to such other member the relevant extract or extracts
of any deficiency notice or similar document regarding such issue. The failure
of any Indemnitee to give such notice shall not relieve any Indemnitor of its
obligations under this Agreement except to the extent such Indemnitor or its
Affiliate is prejudiced by such failure to give notice.

         Section 4.03. Forwarding Responsibilities. If Parent or Diagnostics
                       ---------------------------
fails to comply in any respect whatsoever with any of its responsibilities under
the Agreement relating to promptly forwarding any communications with any taxing
authority ("Forwarding Responsibilities"), then:

         (a) The party failing to fulfill the Forwarding Responsibilities shall
be liable for and shall indemnify and hold the other party harmless from and
against any costs or expenses (including Taxes and lawyers' and accountants'
fees) ("Indemnified Amount") incurred by or imposed upon the party to receive
such communication as a result of such delay with respect to such communication.

         (b) Whenever an Indemnitee receives any written communication by any
means from any Governmental Entity that relates to or could have an effect on
Taxes for any Pre-Closing Taxable Period, the Indemnitee shall immediately
thereupon forward a copy of such communication to the Indemnitor at the address
provided in Section 5.03. The failure of any Indemnitee to give such notice
shall not relieve any Indemnitor of its obligations under this Agreement except
to the extent such Indemnitor or its Affiliate is prejudiced by such failure to
give notice.

         (c) All communications forwarded pursuant to Section 4.03 hereunder
shall be delivered by hand including overnight business courier or mailed by
registered or certified mail (return receipt requested) to the parties at the
addresses set forth in Section 5.03.

         Section 4.04. Audit Matters.
                       -------------

         (a) In the case of any audit, hearing, litigation or other proceeding
(each, a "Proceeding") with respect to any U.S. consolidated federal income Tax
Return of the Athena Group or any Combined Income Tax Return of a Combined
Group, Parent shall control the defense or prosecution of the Proceeding
including settlement.


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         (b) In the case of any other Tax, the company having liability for the
Tax under this Agreement shall have exclusive control over the Proceeding,
including exclusive authority with respect to any settlement of such Tax
liability.

         Section 4.05. Cooperation and Exchange of Information.
                       ---------------------------------------

         (a) Preparation of Returns. Diagnostics shall prepare and submit to
             ----------------------
Parent (i) in accordance with past practice, but in no event later than June 15,
2002, all information that Parent shall request to enable Parent to file the
Athena Group consolidated federal income tax return for the 2001 taxable year,
including a pro forma tax return for Diagnostics, and (ii) in accordance with
past practice, but in no event later than sixty (60) days prior to the due date
for such return all information as Parent shall reasonably request to enable
Parent to file any Combined Group's state or local combined, consolidated or
unitary Income Tax Returns.

         (b) Cooperation. Diagnostics agrees to provide the Athena Group with
             -----------
such cooperation, information and other assistance as Parent or any member of
the Athena Group shall reasonably request in connection with the preparation or
filing of any Tax Return or claim for refund not inconsistent with this
Agreement or in conducting any Proceeding in respect of Taxes. Without
limitation, Diagnostics agrees that it will respond to any information document
request from any taxing authority forwarded by any member of the Athena Group in
respect of the activities of Diagnostics as soon as practicable but not later
than thirty (30) days after its receipt thereof.

         (c) Record Retention. Parent and Diagnostics agree to retain all Tax
             ----------------
Returns, related schedules and workpapers, and all material records and other
documents required under Section 6001 of the Code and the regulations
promulgated thereunder relating thereto, existing on the date hereof or created
through the Closing Date, until the expiration of the statute of limitations
(including extensions) of the taxable years to which such Tax Returns and other
documents relate and until the Final Determination of any payments which may be
required in respect of such years under this Agreement. Parent and Diagnostics
agree to advise each other promptly of any such Final Determination. Any
information obtained under this Section 4.05 shall be kept confidential, except
as may be otherwise necessary in connection with the filing of Tax Returns or
claims for refund or in conducting any audit or other proceeding.

                                    ARTICLE V

                                  MISCELLANEOUS

         Section 5.01. Expenses. Except as otherwise expressly provided in this
                       --------
Agreement, each party shall bear any and all expenses that arise from its
obligations under this Agreement.


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         Section 5.02. Amendment. This Agreement may not be amended except by an
                       ---------
agreement in writing, signed by the parties hereto.

         Section 5.03. Notices. All notices and other communications hereunder
                       -------
shall be in writing and shall be delivered by hand including overnight business
courier or mailed by registered or certified mail (return receipt requested) to
the parties at the following addresses (or at such other addresses for a party
as shall be specified by like notice) and shall be deemed given on the date on
which such notice is received:

         To Parent:

         Athena Neurosciences, Inc.
         800 Gateway Boulevard
         South San Francisco, CA  94080
         Attn:  Director, U.S. Taxation

         To Diagnostics:

         Athena Diagnostics, Inc.
         Four Biotech Park
         377 Plantation Street
         Worcester, MA  06105
         Attn: Chief Financial Officer

         Section 5.04. Term. This Agreement shall commence on the date of
                       ----
execution indicated below and shall continue in effect until otherwise agreed to
in writing by Parent and Diagnostics, or their successors.

         Section 5.05. Legal Enforceability. Any provision of this Agreement
                       --------------------
which is prohibited or unenforceable in any jurisdiction shall, as to such
jurisdiction, be ineffective to the extent of such prohibition or
unenforceability without invalidating the remaining provisions hereof. Any such
prohibition or unenforceability in any jurisdiction shall not invalidate or
render unenforceable such provision in any other jurisdiction. Without prejudice
to any rights or remedies otherwise available to any party hereto, each party
hereto acknowledges that damages would be an inadequate remedy for any breach of
the provisions of this Agreement and agrees that the obligations of the parties
hereunder shall be specifically enforceable.

         Section 5.06. Governing Law. This Agreement shall be governed by the
                       -------------
laws of the State of New York, without regard to principles of conflicts of
laws.

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



                                      ATHENA NEUROSCIENCES, INC.


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


                                      ATHENA DIAGNOSTICS, INC.


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