IDM PHARMA, INC. DIRECTORS' DEFERRED COMPENSATION PLAN

Exhibit 10.55

IDM PHARMA, INC.

DIRECTORS’ DEFERRED COMPENSATION PLAN

Effective as of March 17, 1995

As Amended through December 31, 2008

TABLE OF CONTENTS

IDM PHARMA, INC.

DIRECTORS’ DEFERRED COMPENSATION PLAN

(As Amended through December 31, 2008)

      IDM Pharma, Inc. , a Delaware corporation (the “Company”), previously adopted effective as of March 17, 1995 the IDM Pharma, Inc. Directors’ Deferred Compensation Plan (the “Plan”) as an amendment and restatement of the Cytel Corporation Directors’ Deferred Compensation Plan for the nonemployee directors of the Company upon the terms and conditions set forth below.

     The Company believes that it is in its best interests to amend and restate this Plan with respect to Post-2004 Deferrals for purposes of compliance with Section 409A of the Internal Revenue Code of 1986, as amended, and its regulations and other guidance thereunder.

     The benefits payable under the Plan are and at all times will be mere unsecured contractual rights against the Company payable from the Company’s general assets. It is intended that the Plan shall constitute an unfunded deferred compensation arrangement for purposes of United States federal income tax laws, and all documents, agreements or instruments made or given pursuant to the Plan shall be interpreted so as to carry out this intent.

1. Purpose of the Plan

     The purpose of this Plan is to provide deferred compensation benefits to nonemployee directors of the Company, payable by the Company. This Plan will provide benefits derived from contributions by the Company hereunder of a nonemployee director’s compensation as to which he or she has elected to defer payment under the Plan.

2. Definitions

     The capitalized terms defined in this Section 2 shall have the meanings set forth below:

     2.1 Account. A separate Plan account, which is a bookkeeping record, established for each Participant to which shall be allocated Compensation Reductions in accordance with Section 4.1.

     2.2 Beneficiary. The beneficiary or beneficiaries designated by a Participant to receive any remaining Benefits due under the Plan after his or her death. If the Participant has not designated a Beneficiary, the Beneficiary shall be the Participant’s surviving spouse or, if none, the Participant’s estate.

     2.3 Benefit. The benefit or benefits provided under this Plan, which for a Participant shall be equal to the account balance of such Participant’s Account.

     2.4 Board. The Board of Directors of the Company.

     2.5 Code. The Internal Revenue Code of 1986, as it may be amended from time to time.

     2.6 Company. IDM Pharma, Inc., a Delaware corporation, or any successor corporation.

     2.7 Compensation. All the non-equity fees (paid in cash or by check) received by a Participant from the Company for a Plan Year for his or her services as a Director, including but not limited to, the retainer fee and meeting attendance fees.

     2.8 Compensation Reductions. The percentage of Compensation which a Participant has elected to defer pursuant to a Deferred Compensation Agreement, and that the Company and the Participant mutually agree shall be deferred in accordance with the Plan. Participants may elect to defer any whole percentage of Compensation up to 100% of Compensation.

     2.9 Deferred Compensation Agreement. An agreement by which a Participant elects to reduce a selected whole percentage of his or her Compensation for a Plan Year in order for the Company to make contributions to the Plan on his or her behalf.

     2.10 Director. A member of the Board.

     2.11 Effective Date. March 17, 1995.

     2.12 Eligible Director. A Director who is not an employee of the Company.

     2.13 Fair Market Value. The fair market value of a share of Common Stock of the Company is the closing sales price for such stock as quoted on a national securities exchange or the NASDAQ National Market System of the National Association of Securities Dealers, Inc. Automated Quotation System on the day of determination, as reported in The Wall Street Journal or such other source as the Company deems reliable.

      2.14 Non-Employee Director. A Director who either (i) is not a current employee or officer of the Company or its parent or subsidiary, does not receive compensation (directly or indirectly) from the Company or its parent or subsidiary for services rendered as a consultant or in any capacity other than as a Director (except for an amount as to which disclosure would not be required under Item 404(a) of Regulation S-K promulgated pursuant to the Securities Act of 1933, as amended (“Regulation S-K”)), does not possess an interest in any other transaction as to which disclosure would be required under Item 404(a) of Regulation S-K, and is not engaged in a business relationship as to which disclosure would be required under Item 404(b) of Regulation S-K; or (ii) is otherwise considered a “non-employee director” for purposes of Rule 16b-3 promulgated under the Exchange Act of 1934, as amended.

     2.15 Participant. Any Eligible Director who has elected to participate in the Plan by entering into a Deferred Compensation Agreement.

     2.16 Plan. This IDM Pharma, Inc. Directors’ Deferred Compensation Plan, as amended from time to time.

     2.17 Plan Year. The calendar year.

     2.18 Post-2004 Deferrals. The portion of the Account other than Pre-2005 Deferrals. The Plan shall maintain separate accounting for Post-2004 Deferrals.

     2.19 Pre-2005 Deferrals. That portion of the Account determined as of December 31, 2004, to which the Participant has a legally binding right to be paid, and the right to which is earned and vested as of December 31, 2004, in accordance with Section 409A and its regulations and other guidance thereunder, plus earnings and losses allocable to such amounts. The Plan shall maintain separate accounting for Pre-2005 Deferrals.

     2.20 Section 409A or Code Section 409A. Section 409A of the Internal Revenue Code of 1986, as it may be amended from time to time, and the regulations and other guidance thereunder.

     2.21 Share. A participating interest under the Plan, which shall be equal to the Fair Market Value of a share of Common Stock of the Company.

     2.22 Termination of Service. A Participant’s termination of directorship for any reason that is a “separation from service” from the Company for purposes of Section 409A of the Code. The determination of whether a Participant has had a Termination of Service shall be made in a manner consistent with Section 409A of the Code and Treas. Reg § 1.409A-(1)(h) or as this definition may later be modified by other regulatory pronouncements.

     2.23 Valuation Date. The last day of each calendar quarter, or such other date as shall be established by the Company.

3. Participation

     3.1 Participation of Eligible Directors.

          (a) Each Eligible Director may begin to participate in the Plan on the Effective Date; provided, however, that such Eligible Director completes and signs a Deferred Compensation Agreement and returns such Deferred Compensation Agreement to the designated representative of the Company prior to the Effective Date or such earlier date established by the Company and announced to the Eligible Director. Such Deferred Compensation Agreement shall be effective for the period beginning on the Effective Date and ending on December 31, 1995.

          (b) Each Director who first becomes an Eligible Director after the Effective Date may begin to participate in the Plan by completing and signing a Deferred Compensation Agreement and returning such Deferred Compensation Agreement to the designated representative of the Company; provided, however, that such completion and return of the Deferred Compensation Agreement to the Company occurs within thirty (30) days after the date that the Director first becomes an Eligible Director. Such Deferred Compensation Agreement shall be effective with respect to the portion of Compensation attributable to services performed by the Director during the period beginning on the date the Eligible Director completes and returns the Deferred Compensation Agreement to the Company and ending on the last day of the

Plan Year within which such participation begins, which will generally include the retainer fees and meeting attendance fees that would otherwise have been paid to the Eligible Director during the remainder of the Plan Year following the return of the Deferred Compensation Agreement. Once the Eligible Director completes and returns the Deferred Compensation Agreement to the Company within the thirty (30) day period after the date that the Director first becomes an Eligible Director, the election is irrevocable. Notwithstanding the foregoing, any Deferred Compensation Agreement completed and returned to the Company on or after December 19, 2005 shall continue to be effective for subsequent Plan Years unless and until the Participant completes and returns a new Deferred Compensation Agreement in accordance with Section 3.1(d) below.

          (c) An Eligible Director who did not become a Participant in accordance with the terms of paragraph (a) or (b) may participate in the Plan effective as of the beginning of any Plan Year following the Plan Year in which he or she becomes an Eligible Director by completing and signing a Deferred Compensation Agreement and returning such Deferred Compensation Agreement to the designated representative of the Company prior to the beginning of the Plan Year (or such earlier date established by the Company and announced to the Eligible Director) for which deferral of Compensation is intended to commence. For deferral elections made for the 2005 Plan Year and any previous Plan Years, such Deferred Compensation Agreement shall be effective only for the Plan Year first following the submission of the Deferred Compensation Agreement. For deferral elections made for the 2006 Plan Year and any subsequent Plan Years, such Deferred Compensation Agreement shall continue to be effective for subsequent Plan Years unless and until the Participant completes and returns a new Deferred Compensation Agreement in accordance with Section 3.1(d) below.

          (d) If a Participant wishes to commence deferrals of Compensation under the terms of the Plan or change his or her elected percentage of deferred Compensation for any Plan Year subsequent to the first Plan Year in which the Participant began to participate in the Plan, such Participant must complete and sign a new Deferred Compensation Agreement and return such Deferred Compensation Agreement to the designated representative of the Company prior to the beginning of the Plan Year (or such earlier date established by the Company and announced to the Participant) for which such election is to be effective. For deferral elections made for the 2005 Plan Year and any previous Plan Years, such Deferred Compensation Agreement shall be effective only for that Plan Year. For deferral elections made for the 2006 Plan Year and any subsequent Plan Years, such Deferred Compensation Agreement shall continue to be effective for subsequent Plan Years unless and until the Participant completes and returns a new Deferred Compensation Agreement.

     3.2 Irrevocability of Participation During the Plan Year. A Participant may not terminate or modify his or her Deferred Compensation Agreement with respect to a Plan Year on or after the first day of such Plan Year.

     3.3 Suspended Participation. If a Participant ceases to be an Eligible Director, but continues to be a Director, he or she shall not be eligible to make future elections to defer Compensation under the Plan for subsequent Plan Years. Distributions shall be made to such Participant as would otherwise be permitted in accordance with the distribution provisions under this Plan. If such Participant again becomes an Eligible Director in a Plan Year following the

last Plan Year for which a Deferred Compensation Agreement was in effect, such Participant may elect to participate in the Plan by following the procedures specified in Section 3.1(c).

     3.4 Termination of Participation. A Participant shall cease to be a Participant as of the date he or she ceases serving as a Director.

4. Plan Accounts

     4.1 Accounts. The Company shall maintain or cause to be maintained for each Participant an Account with respect to which the Company shall allocate amounts equal to the Participant’s Compensation Reductions for each Plan Year, effective as of the date such Compensation Reductions would have been paid to the Participant as Compensation in the absence of a Deferred Compensation Agreement.

     4.2 Investment of Accounts.

           (a) Each Compensation Reduction allocated to a Participant’s Account shall be converted into that number of Shares that equal the amount of such Compensation Reduction divided by the Fair Market Value of the Common Stock of the Company as of the date such Compensation Reduction would have been paid to the Participant as Compensation in the absence of a Deferred Compensation Agreement. The calculation of the number of Shares need not be rounded to the nearest whole Share, so that a fraction of a Share (calculated to the nearest one-hundredth of a Share) may be allocated to a Participant’s Account.

           (b) In the event any dividends or distributions are made with respect to the Common Stock of the Company, the Company shall allocate an amount to the Participant’s Account that is equal to the amount of such dividends or distributions that would have been made with respect to the Shares allocated to a Participant’s Account if they were shares of the Common Stock of the Company. Such dividend/distribution allocations shall be converted into that number of whole and/or fractional Shares that equal the amount of such allocation divided by the Fair Market Value of the Common Stock of the Company as of the date such dividends or distributions are made with respect to the Common Stock of the Company to the Company’s stockholders of record.

     4.3 Value of Accounts. The value of a Participant’s Account as of any Valuation Date shall be equal to the number of Shares allocated to a Participant’s Account multiplied by the Fair Market Value of one share of the Common Stock of the Company.

     4.4 Funds Unsecured. Notwithstanding any other provisions of this Plan, all Benefits payable under the Plan are subject to the claims of the general creditors of the Company. No trust shall be established to hold any assets which may be set aside by the Company to pay the Benefits under the Plan and the Company shall be under no obligation to set aside any amounts to pay Benefits. The maintenance of separate Accounts by the Company as provided herein shall neither require nor be considered a segregation of any funds or property from the Company’s general assets. Participants shall have no preferred claim on or beneficial ownership interest in any assets of the Company prior to the time actual payments of Benefits are received, and all rights of the Participants to Benefits are mere unsecured contractual rights against the Company.

5. Benefits

     5.1 Termination Benefits—Distribution of Deferrals.

          (a) For Pre-2005 Deferrals, when a Participant ceases serving as a Director, the Participant shall be entitled to receive the value of his or her Account determined as of the Valuation Date coinciding with or next preceding the date of the distribution.

          (b) For Post-2004 Deferrals, when a Participant has a Termination of Service, the Participant shall be entitled to receive the value of his or her Account determined as of the Valuation Date coinciding with or next preceding the date of the distribution.

     5.2 Form of Distribution.

          (a) If at the time the Participant is entitled to a distributio