Exhibit 10.28

***Text Omitted and Filed Separately
Confidential Treatment Requested
Under 17 C.F.R. §§ 200.80(b)(4)
and 240.24B-2

LETTER AGREEMENT

THIS LETTER AGREEMENT(this "Agreement") is entered into as of
January 9, 2004 (the"Effective Date") by and amongFOREST LABORATORIES IRELAND LIMITED, an Irish
corporation ("Forest"), having offices at Clonshaugh Industrial Estate, Clonshaugh, Dublin 17, Republic of Ireland,CYPRESS
BIOSCIENCE, INC., a Delaware corporation ("Cypress"), having offices at 4350 Executive Drive, Suite 325, San Diego, CA
92121 andPIERRE FABRE MÉDICAMENT, organized under the laws of France ("Pierre Fabre"),
having offices at 45, place Abel-Gance, 92654 Boulogne Cedex, France.

RECITALS

WHEREAS,Cypress and Pierre Fabre have entered into the Third Restated License Agreement as of the date hereof, as
may be amended (the"License Agreement"), the First Restated Trademark License Agreement dated as of the date hereof, as may be amended (the "Trademark
Agreement"), and the Purchase and Supply Agreement as of the date hereof, as may be amended (the"Supply
Agreement"), a copy of each of which has been provided to Forest, pursuant to which Pierre Fabre has granted to Cypress an exclusive license to develop and commercialize
Licensed Product (as defined in the License Agreement, except as otherwise noted herein) and Pierre Fabre will supply to Cypress and its sub-licensees, and Cypress and its
sub-licensees will purchase from Pierre Fabre, Bulk API (as defined in the Supply Agreement);

WHEREAS,Forest and Cypress are entering into a License and Collaboration Agreement as of the date hereof, as may be amended, modified or
restated from time to time (the"Collaboration Agreement"),
pursuant to which, among other things, Cypress is granting to Forest an exclusive sub-license under the rights granted to Cypress by Pierre Fabre under the License Agreement and the
Trademark Agreement in the Licensed Territory (as defined in the Collaboration Agreement), all on the terms and conditions set forth in the Collaboration Agreement; and

WHEREAS,Forest, Cypress and Pierre Fabre are entering into this Agreement in order to govern the relationship among Forest, Cypress and
Pierre Fabre under certain provisions of the Supply Agreement, the License Agreement and the Trademark Agreement.

AGREEMENT

NOW, THEREFORE,in consideration of the foregoing premises and the mutual covenants and agreements contained
herein and other good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, the parties hereto agree as follows:

1.SUPPLY; FORECASTS

1.1    Supply of Bulk API.The parties agree that, until Pierre Fabre is otherwise notified in writing by Cypress
in connection with a termination of Forest's rights under the Collaboration Agreement, Pierre Fabre will manufacture and supply directly to Forest, and Forest will purchase directly from Pierre Fabre,
Bulk API for the Licensed Territory on the terms set forth in the Supply Agreement, including, without limitation, Sections 2.1, 2.2, 6 and 7.4.

1.2    Forecasts.Forest will provide directly to Pierre Fabre, with a copy to Cypress, (a) Sales Forecasts
(as defined in the License Agreement) for the Licensed Territory on the terms set forth in the License Agreement, and (b) Delivery Forecasts and Purchase Orders (both as defined in the Supply
Agreement) for the Licensed Territory on the terms set forth in the Supply Agreement, including,

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without
limitation, Section 4.1;provided thatsuch Sales Forecasts, Delivery Forecasts and Purchase Orders have first been reviewed and agreed
to between Cypress and Forest to the extent such Sales Forecasts, Delivery Forecasts and Purchaser Orders impose obligations on Cypress.

1.3    Independence of Supply Commitment.Pierre Fabre agrees that the terms and conditions of the Supply Agreement
with respect to Delivery Forecasts, Purchase Orders, Pierre Fabre's supply commitment and otherwise shall be determined and applied separately with respect to each of Forest and Cypress (including any
other sub-licensee of Cypress under the License Agreement) if and to the extent Cypress (including any other sub-licensee of Cypress under the License Agreement) purchases Bulk
API for use in Canada.

2.SUB-LICENSE RIGHTS

2.1    Licensed Technology and Trademarks.Forest may further sub-license the rights in the Licensed
Technology (as defined in the License Agreement) and the Trademarks (as defined in the Trademark Agreement) and the rights under the Supply Agreement granted to it by Cypress under the Collaboration
Agreement as follows.



3.PAYMENTS

3.1    Transfer Price.Forest will pay directly to Pierre Fabre the Transfer Price (as defined in the Supply
Agreement) for all Bulk API purchased under the Supply Agreement with respect to the Licensed Territory in accordance with the terms of Section 5 of the Supply Agreement, except that the
obligation of Cypress to make payment to Pierre Fabre under Section 5.1(a)(ii)(2) will apply only to Cypress and not to Forest. Forest will notify Cypress of such payments made by Forest to
Pierre Fabre.

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3.2    Royalties.Forest will pay directly to Pierre Fabre the royalty payments required under Sections 6.4(a),
(b) and (c) of the License Agreement and Section 1.10 of the Trademark Agreement with respect to the Licensed Territory in accordance with the respective terms of the License
Agreement and the Trademark Agreement; provided thatno royalty shall be due from Forest to Pierre Fabre under Section 6.4(a) of the License
Agreement by Forest with respect to the SR Formulation Patent, Ref: 09/254 014 included in the Pierre Fabre Patents (as defined in the License Agreement). Forest agrees that it shall notify Cypress of
such payments to Pierre Fabre.

3.3    Payment for Canada.Pursuant to Sections 3.1 and 5.2 of the License Agreement, and Section 2.5 of the
Collaboration Agreement, Pierre Fabre acknowledges that the decision whether or not to develop, register and launch Licensed Product in Canada, and the timing of any such decision, shall be subject to
the good faith business judgment of Forest; provided however,if Forest does not exercise its right to extend the Licensed Territory under
Section 2.5 of the Collaboration Agreement to include Canada prior to the expiration of[...***...](i) Forest
shall have no further rights with respect to Canada under this Letter Agreement, the Collaboration Agreement or the License Agreement and (ii) Cypress' obligations under Section 5.2 of
the License Agreement shall remain in full force and effect. In the event Forest does exercise its right to extend the Licensed Territory under Section 2.5 of the Collaboration Agreement to
include Canada and subsequently determines not to launch Licensed Product in Canada, promptly following such determination, (a) Forest shall pay to Pierre Fabre [...***...](the"Canadian Payment") and (b) Cypress shall pay to Pierre
Fabre the[...***...]Promptly following such determination by Forest, Forest will make a good faith calculation of the Canadian
Payment and will provide such calculation to Pierre Fabre, with a copy to Cypress. Pierre Fabre will review such calculation and will notify Forest in writing, with a copy to Cypress, within
30 days of the date Forest provided such calculation if Pierre Fabre has any questions regarding, or objects to, the Forest calculation. If Pierre Fabre does not provide such written notice
within such 30-day period, Forest shall[...***...]If Pierre Fabre provides such written notice to Forest within
such 30-day period, then Forest and Pierre shall negotiate in good faith regarding[...***...]If such negotiation
requires that Pierre Fabre[...***...]then Forest and Pierre Fabre shall select one expert with relevant industry experience to
review such information in connection with[...***...]provided that,if the parties cannot agree on one
expert, then a panel of three experts with relevant industry experience shall be formed for such purpose, with one expert being chosen by Forest, one expert being chosen by Pierre Fabre and one expert
being chosen by the two experts chosen by Forest and Pierre Fabre. The expert or the panel of experts, as applicable, must be chosen within 30 days from notice by either Forest or Pierre Fabre
regarding the need to appoint such expert or panel of experts. Any such expert or panel of experts shall enter into a confidential disclosure agreement with Forest and Pierre Fabre containing
commercially reasonable terms for protection of proprietary information provided by Forest and Pierre Fabre. Pierre Fabre shall provide such expert or panel of experts information regarding Pierre
Fabre's[...***...]Forest shall provide such expert or panel of experts such additional information used by Forest in [...***...]as is necessary to use
the information regarding [...***...]The expert or panel of experts shall review such information provided by Forest and Pierre Fabre, use such
information in[...***...]and provide the parties with the result of such calculation for use in the Canadian Payment within
30 days from the selection of the expert or the last expert on the panel, as applicable. The parties acknowledge that in no event shall the panel share any information regarding Pierre Fabre's [...***...]with Forest and Cypress. Forest and Pierre Fabre shall each pay 50% of the costs of engaging the expert or panel of
experts under this Section 3.3. Forest may, at its option upon written notice to Pierre Fabre, pay the Canadian Payment either in a lump sum payment based on the net present value of the
Canadian Payment as of the date of such payment (calculated at the applicable LIBOR rate of interest as reported inThe Wall Street Journal(absent any
error) on the date of the determination of the Canadian Payment pursuant to this Section 3.3) or in payments made on a quarterly basis over no more than five years, as designated by Forest.
Forest will notify Cypress of such payments made by Forest to Pierre Fabre.

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3.4    Royalty from Forest to Pierre Fabre; Sharing of Royalty with Cypress.



3.5    Royalty to Pierre Fabre on New Product; Right of First Negotiation to Supply Bulk API for New Product.



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3.6    Sharing with Forest of Payments Made by Pierre Fabre to Cypress.Cypress will pay to Forest a share of the
amount of any royalty paid to Cypress by Pierre Fabre on certain products for FMS in the Licensed Territory (as defined in the Collaboration Agreement) pursuant to Section 5.4(b) of the License
Agreement, based on[...***...]In addition, Cypress will pay to Forest [...***...]

3.7    SNRI Products.During the period from the Effective Date until the earlier of (i) the Date of First
Commercial Sale of the first Generic Product (each as defined in the License Agreement) or (ii) the last day of the License Term (as defined in the License Agreement), if any of Pierre Fabre,
Cypress or Forest (or any Affiliate, licensee or sub-licensee of such party with respect to an SNRI product) wishes to develop any SNRI product (as defined in the License Agreement),
including, without limitation, the[...***...]Milnacipran [...***...](the"Pierre Fabre[...***...]") and any New

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Product
(subject to Section 3.7(d)), but excluding Licensed Product (as defined in the License Agreement), for use in the Licensed Territory, such party shall be subject to the following:



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4.FORMULATIONS

4.1    Grant to Pierre Fabre of License to Forest Formulations.Cypress and Pierre Fabre agree that the
sub-licensegranted to Forest under Section 2.1 of the Collaboration Agreement provides Forest with the right to develop and commercialize its own new formulations of Licensed
Product. In the event Forest decides to develop and commercialize any new formulation of Licensed Product ("Forest Formulation"), rather than the IR
Formulation or SR Formulation (as defined the Licensed Agreement), Forest will then notify Pierre Fabre and Cypress of such Forest Formulation and Forest will grant to Pierre Fabre a perpetual,
royalty-free, exclusive license, with the right to sub-license, under the applicable patents and patent applications owned by Forest or its Affiliates (as defined in the
Collaboration Agreement) claiming such Forest Formulation, to develop, register, manufacture, use, distribute, sell, offer for sale, have sold and import such Forest Formulation in the Rest of the
World (as defined in the License Agreement). The parties acknowledge and agree that Forest Formulation expressly excludes any Cypress Formulation (as defined in the Collaboration Agreement).

5.FOREST AND CYPRESS OBLIGATIONS

5.1    Promotion, Marketing and Sales Effort.



5.2    Forest Negotiation with Cypress and Pierre Fabre.Forest shall negotiate in good faith with Cypress and
Pierre Fabre with regard to the matters described in Section 5.4(c) of the Collaboration Agreement and Section 5.4(c) of the License Agreement.

6.TERM.The term of this Agreement shall commence on the
Effective Date and continue until the earlier of (i) the termination of the Supply Agreement and the License Agreement;provided, however,that
if, upon termination of the Supply Agreement and the License Agreement, such agreements remain in place between Pierre Fabre and Forest, this Agreement shall terminate only as to Cypress, or
(ii) upon receipt by Pierre Fabre of written notification from Cypress and Forest of the termination of the Collaboration Agreement (the"Term").

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7.RECOGNITION

7.1    Acknowledgement.Pierre Fabre hereby acknowledges the execution of the Collaboration Agreement and
acknowledges that as of the Effective Date, all rights of Pierre Fabre under Section 2.1(b) the License Agreement to negotiate for rights to develop, register, market or sell Licensed Product
in the Licensed Territory have either been satisfied or waived.

7.2    Representation.Pierre Fabre hereby represents and warrants, as of the Effective Date, that each of the
License Agreement, Supply Agreement and Trademark Agreement constitute legal and validly binding obligations of Pierre Fabre, and are in full force and effect and enforceable in accordance with their
respective terms, and that, to its knowledge, no event has occurred which would give Pierre Fabre the right to terminate or limit any of such agreements or to seek damages or other legal or equitable
remedies with respect thereto.

7.3    Recognition.



7.4    Amendments.



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7.5    Survival of Agreements.Any rights granted by Pierre Fabre to Forest hereunder or under the License
Agreement, Supply Agreement or Trademark Agreement by reason of the Collaboration Agreement shall survive any termination of such agreements for any reason, excepting only a termination as a result of
which Forest no longer possess rights to manufacture, market and distribute Licensed Product for distribution in the Licensed Territory, and shall become direct rights and obligations between Forest
and Pierre Fabre, subject to the respective terms of such agreements, including, without limitation, the conditions for establishing a direct contractual relationship between Pierre Fabre and Forest.

7.6    Appointment of Forest Laboratories, Inc.Forest shall designate and appoint Forest Parent to perform
all development, registration, distribution and marketing obligations of Forest in the Licensed Territory arising under the Collaboration Agreement (and, if Forest becomes a direct party thereto or a
licensee thereunder, under the License Agreement, Supply Agreement or Trademark Agreement) and agrees to cause representatives of Forest Parent to participate as representatives in all committees or
working
groups which may be established from time to time under any of such agreements to the extent of Forest's rights to participate in any such committees or working groups.

8.GENERAL PROVISIONS.

8.1    Dispute Resolution.If the parties are unable to decide or resolve any issue arising under this Agreement,
except as expressly contemplated in Section 3.3, the issue shall be referred to the Chief Executive Officers of Pierre Fabre, Cypress and Forest (or any Affiliate of Forest that is primarily
responsible for the activities of Forest under the Collaboration Agreement, as directed by Forest). Such officers of the parties shall meet promptly thereafter and shall negotiate in good faith to
resolve such issue. If they cannot resolve the issue within 30 days of commencing such negotiations, the matter shall be resolved by arbitration as provided in Section 8.2.

8.2    Arbitration.



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8.3    Governing Law.This Agreement shall be governed by, and construed and enforced in accordance with, the laws
of the State of New York excluding its conflicts of laws principles.

8.4    Modification.This Agreement may only be modified or supplemented in a writing expressly stated for such
purpose and signed by all the parties to this Agreement. To the extent a party has no interest in any such modification or supplement, such party shall act in good faith in agreeing to such
modification or supplement.

8.5    Relationship Among the Parties.The parties' relationship, as established by this Agreement, is solely that
of independent contractors. This Agreement does not create any partnership, joint venture or similar business relationship among the parties. No party is a legal representative of any other party, and
no party can assume or create any obligation, representation, warranty or guarantee, express or implied, on behalf of any other party for any purpose whatsoever.

8.6    Non-Waiver.The failure of a party to insist upon strict performance of any provision of this
Agreement or to exercise any right arising out of this Agreement shall neither impair that provision or

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right
nor constitute a waiver of that provision or right, in whole or in part, in that instance or in any other instance. Any waiver by a party of a particular provision or right shall be in writing,
shall be as to a particular matter and, if applicable, for a particular period of time and shall be signed by such party.

8.7    Assignment.The parties may assign this Agreement under the same circumstances as permitted for assignment
of the License Agreement, the Trademark Agreement, the Supply Agreement and the Collaboration Agreement.

8.8    No Third Party Beneficiaries.This Agreement is neither expressly nor impliedly made for the benefit of any
party other than those executing it.

8.9    Severability.If, for any reason, any part of this Agreement is adjudicated invalid, unenforceable or
illegal by a court of competent jurisdiction, such adjudication shall not affect or impair, in whole or in
part, the validity, enforceability or legality of any remaining portions of this Agreement. All remaining portions shall remain in full force and effect as if the original Agreement had been executed
without the invalidated, unenforceable or illegal part.

8.10    Notices.Any notice to be given under this Agreement must be in writing and delivered as described in the
License Agreement if to Cypress or Pierre Fabre and as described in the Collaboration Agreement if to Forest.

8.11    Legal Fees.If any party to this Agreement resorts to any legal action or arbitration in connection with
this Agreement, subject to Section 8.2(e), the prevailing party shall be entitled to recover reasonable fees of attorneys and other professionals in addition to all court costs and arbitrator's
fees which that party may incur as a result.

8.12    Interpretation.



8.13    Counterparts.This Agreement may be executed in one or more counterparts, each of which shall be deemed an
original document, and all of which, together with this writing, shall be deemed one instrument.

8.14    Letter Agreement Control.In the event of a conflict between any terms and conditions of this Agreement, on
one hand, and the License Agreement, Supply Agreement, Trademark Agreement

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and
Collaboration Agreement on the other hand, this Agreement shall control with respect to any and the applicable terms and conditions contained herein.

8.15    Affirmation.The parties acknowledge and agree that Section 2.1(e) of the License Agreement remains
in full force and effect, and, accordingly, nothing contained in this Agreement is intended to limit the rights and obligations of Cypress and Pierre Fabre under the License Agreement, Trademark
Agreement and the Supply Agreement.

8.16    Certain Matters Regarding the Collaboration Agreement.Cypress and Forest hereby represent and warrant to
Pierre Fabre that a true, accurate and complete copy of the Collaboration Agreement has been delivered to Pierre Fabre. Cypress and Forest agree to promptly provide to Pierre Fabre copies of any and
all amendments, waivers, default notices and restatements executed and delivered in connection with the Collaboration Agreement. In addition, Cypress and Forest agree that the rights and authority of
the Joint Development Committee under the Collaboration Agreement do not supercede the rights and authority of the Steering Committee under the License Agreement.

[Remainder of Page Intentionally Left Blank]

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IN WITNESS WHEREOF,the parties hereto have duly executed this Agreement.

|FOREST LABORATORIES IRELAND LIMITED |  | CYPRESS BIOSCIENCE, INC.
|----------------------------------- |  | ------------------------
|By:                                 |  | /s/RAYMOND STAFFORD     
|Name:                               |  | Raymond Stafford        
|Title:                              |  | Chief Executive Officer 
|PIERRE FABRE MÉDICAMENT             |  |                         
|By:                                 |  | /s/JEAN PIERRE COUZINIER
|Name:                               |  | Jean Pierre Couzinier   
|Title:                              |  | Chief Operating Officer 

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