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                                                            Exhibit No. 10.68

AGREEMENT AND MUTUAL RELEASE AND DISCHARGE dated as of the day of
______________, 2001.


BY AND BETWEEN:             METHYLGENE INC.

                           (hereinafter referred to as the "METHYLGENE")




AND:                       HYBRIDON, INC.

                           (hereinafter referred to as "HYBRIDON")






WHEREAS Hybridon is currently a shareholder of Methylgene;


WHEREAS Hybridon wishes to sell shares it owns in the share capital of
Methylgene pursuant to an offer (the "OFFER") dated February 12, 2001 from Paul
Capital Partners (Paul Capital Partners and any affiliates thereof hereinafter
referred to as "PAUL CAPITAL") and accepted by Hybridon on February 14, 2001;


WHEREAS Hybridon may sell other shares it owns in the share capital of
Methylgene to certain existing shareholders or to others; and


WHEREAS Methylgene has agreed to cooperate and assist Hybridon in effecting
these transactions;


THEREFORE, FOR GOOD AND VALUABLE CONSIDERATION RECEIVED, THE PARTIES
HERETO AGREE AS FOLLOWS:


1.       COMPLIANCE - METHYLGENE


         1.1      Methylgene hereby certifies that it is and, to its knowledge,
                  Hybridon is in compliance with and not in default of any and
                  all agreements between Hybridon and Methylgene existing as at
                  the date hereof including, for greater certainty but not
                  limited to, the agreements listed in Schedule A attached
                  hereto;
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2.       COMPLIANCE - HYBRIDON


         2.1      Hybridon hereby certifies that it is and, to its knowledge,
                  Methylgene is in compliance with and not in default of any and
                  all agreements between Hybridon and Methylgene existing as at
                  the date hereof including, for greater certainty but not
                  limited to, the agreements listed in Schedule A attached
                  hereto;


3.       NON-COMPETITION


         3.1      The introductory paragraph of Section 13.1 of the Shareholders
                  Agreement (as defined in Schedule A) is amended by deleting
                  same and replacing it with the following:


                  "13.1    Hybridon undertakes in favour of Methylgene, whether
                           directly or indirectly, alone or in partnership,
                           association, joint venture or other collaboration
                           with any other person, company, partnership, business
                           or entity, as a principal, agent, shareholder,
                           employee, partner, consultant, subcontractor, unless
                           for the benefit of Methylgene, at the request of
                           Methylgene or with the consent of Methylgene, not
                           to:"


         3.2      Section 13.1.1 of the Shareholders Agreement is amended by
                  deleting same and replacing it with the following:


                  "13.1(A) from the date of the Agreement and Mutual Release and
                           Discharge entered into between Methylgene and
                           Hybridon until the expiry of a thirty (30) month
                           period starting the later of (a) May 31, 2001, (b)
                           the closing of the transaction contemplated by the
                           Offer and (c) Hybridon no longer having a nominee on
                           Methylgene's Board of Directors (the "COMMENCEMENT
                           DATE"), research, develop or market anywhere in the
                           world (i) any antisense compounds to inhibit DNA
                           Methyltransferases ("DNA METASES"), or (ii) any
                           method of inhibiting DNA MeTases for the treatment of
                           any indication;


                  13.1(B)  from the date of the Agreement and Mutual Release and
                           Discharge entered into between Methylgene and
                           Hybridon until the expiry of an eighteen (18) month
                           period starting on the Commencement Date (the
                           "RESTRICTIVE TERM"), not to engage in research or
                           development or marketing anywhere in the world
                           relating to the fields of histone deacetylases and
                           beta-lactamases. If prior to the expiration of the
                           Restrictive Term, Methylgene gives Hybridon written
                           notice designating a target gene or genes within
                           either histone deacetylases or beta-lactamases or
                           both, as the case may be, as the Second Molecular
                           Target and Third Molecular Target, respectively,
                           under the License Agreement dated January 4, 1996 as
                           amended and restated
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                           between the parties as of September 21, 2000 (the
                           "LICENSE AGREEMENT"), then Hybridon, for an
                           additional period of 18 months from the expiration of
                           the Restrictive Term, shall refrain from research or
                           development or marketing anywhere in the world
                           relating to either histone deacetylases or beta
                           lactamases, or both, depending upon which is the
                           location of the target gene or genes so designated by
                           Methylgene, and the designation of such target gene
                           or genes shall be deemed to have exhausted
                           Methylgene's rights under the License Agreement, to
                           specify a Second Molecular Target, if one designation
                           is made and a Third Molecular Target if two
                           designations are made;"


3.3      Sections 13.1.3 and 13.1.4 of the Shareholders Agreement are amended by
         deleting same and replacing them with the following:


         "13.1.3  from the date of the Agreement and Mutual Release and
                  Discharge entered into between Methylgene and Hybridon until
                  the expiry of a two (2) year period starting on the
                  Commencement Date, solicit entities which are customers or
                  suppliers of Methylgene on the relevant date with respect to
                  compounds or methods of the type described in 13.1(A) and
                  13.1(B); or


         13.1.4   from the date of the Agreement and Mutual Release and
                  Discharge entered into between Methylgene and Hybridon until
                  the expiry of a two (2) year period starting on the
                  Commencement Date, encourage any person employed by Methylgene
                  to leave Methylgene or solicit for employment any person who
                  is at the time of solicitation employed by Methylgene."


3.4      Section 13.1 of the Shareholders Agreement is amended by adding the
         following:


         "13.1.5  Nothing in the foregoing shall restrict the right of Hybridon
                  to own up to 5% of the outstanding capital stock of companies
                  whose shares are traded on a recognized stock exchange."


3.5      In the event of a merger or acquisition involving Hybridon and a
         non-affiliate third party (as the term "affiliate" is defined in the
         License Agreement), the provisions of Section 13 of the Shareholders'
         Agreement (until their expiration pursuant to the provisions of such
         Section 13), as hereinabove amended, and the provisions of Section
         4 below shall continue to apply to the surviving entity
         but shall not be construed in any way which would prejudice and shall
         not prejudice the right and ability of the surviving entity to continue
         to do any research and development activities which the non-affiliate
         third party was undertaking prior to the time of the merger.
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3.6      All other provisions of Section 13 of the Shareholders Agreement shall
         continue to apply mutatis mutandis. To the extent Hybridon is still a
         party to the Shareholders Agreement at the time of the initial public
         offering of the shares of Methylgene (the "IPO"), Hybridon undertakes
         that, pursuant to such IPO, it will agree to the termination of the
         Shareholders Agreement, save and except for the provisions of its
         Section 13, as amended hereby, which shall continue to apply for the
         relevant period.


4.       CONFIDENTIALITY


         4.1      Hybridon agrees, as long as such information or knowledge is
                  not part of the public domain or required to be disclosed in
                  accordance with applicable law, not to disclose, publish or
                  reveal in any manner whatsoever and to whomever, any
                  information or knowledge of a confidential nature concerning
                  the business operated by Methylgene, including, without
                  limiting the generality of the foregoing, trade secrets,
                  biological targets, chemical structures, inventions, software,
                  computer programs, patents, licences, manufacturing processes,
                  know-how, customer lists or contracts of Methylgene, whether
                  acquired by it in its capacity as a shareholder or through any
                  nominee on the Board of Directors, its representatives on the
                  scientific advisory board of Methylgene or from any other
                  means, Hybridon hereby expressly acknowledging that such trade
                  secrets, biological targets, chemical structures, inventions,
                  software, computer programs, patents, licences, manufacturing
                  processes, know-how, customer lists or contract and all other
                  information of a confidential nature concerning the business
                  operated by Methylgene has been disclosed to it at any time on
                  a confidential basis.


5.       UNDERTAKING - LOCK-UP AGREEMENT


         5.1      Hybridon shall, if it is a shareholder of Methylgene, at the
                  request of the underwriters engaged by Methylgene in
                  connection with its IPO, sign a lock-up agreement in their
                  favour in customary form under which Hybridon shall agree not
                  to sell or otherwise dispose of in any way any of its shares
                  in the share capital of Methylgene for the period applicable
                  to other significant shareholders of Methylgene following the
                  IPO, the whole as required by the underwriters. Furthermore,
                  Hybridon recognizes that it may be subject to certain escrow
                  requirements imposed by regulators in connection with an IPO
                  and agrees to comply therewith.


6.       RELEASE AND DISCHARGE - HYBRIDON


         6.1      Except for obligations of the parties set forth in any
                  agreement between them which are intended to survive the
                  execution of this agreement, Hybridon hereby releases and
                  discharges Methylgene from any claims, liabilities, actions or
                  demands of any kind which Hybridon now has or hereafter can,
                  shall or may
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                  have against Methylgene for or by reason of or in any way
                  arising out of any cause, matter or thing whatsoever existing
                  up to the present time.


7.       RELEASE AND DISCHARGE - METHYLGENE


         7.1      Except for obligations of the parties set forth in any
                  agreement between them which are intended to survive the
                  execution of this agreement, Methylgene hereby releases and
                  discharges Hybridon from any claims, liabilities, actions or
                  demands of any kind which Methylgene now has or hereafter can,
                  shall or may have against Hybridon for or by reason of or in
                  any way arising out of any cause, matter or thing whatsoever
                  existing up to the present time.


8.       HYBRIDON REPRESENTATIVE - BOARD OF DIRECTORS


         8.1      Notwithstanding any provision of the Shareholders' Agreement,
                  Hybridon agrees that, in the event it should own less than
                  350,000 shares in the share capital of Methylgene, Hybridon
                  shall no longer be entitled to appoint or elect a nominee on
                  Methylgene's Board of Directors and shall cause its nominee at
                  that time to resign and execute a full release and discharge
                  in customary form upon written notice by Methylgene to
                  Hybridon.


9.       EXPENSES


         9.1      Hybridon hereby agrees to pay any and all out-of-pocket
                  expenses (including, without limitation, the fees and
                  disbursements of Methylgene's legal and patents counsel)
                  incurred by Methylgene in connection with the proposed sale by
                  Hybridon of its shares in the share capital of Methylgene to
                  Paul Capital, to any other shareholder of Methylgene or to any
                  other person.


10.      OBLIGATIONS OF METHYLGENE


         10.1     Methylgene agrees to use its commercially reasonable efforts
                  to approve such measures as are necessary to combine its
                  presently outstanding class A and class B common shares into a
                  single class so as to eliminate any preference between them in
                  the distribution of assets as dividends or distributions upon
                  liquidation and in furtherance of this Methylgene shall
                  recommend that the holders of its class A and class B common
                  shares approve and agree to any action required of them to
                  implement the combination of the two classes of stock. Upon
                  such approval, Methylgene will see to the implementation of
                  these actions.


         10.2     Methylgene agrees to use its commercially reasonable efforts
                  to obtain the approval and consent of the other shareholders
                  of Methylgene to the amendment to the Shareholders Agreement
                  contemplated by Section 3 herein.
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                  Notwithstanding the foregoing however, Hybridon undertakes and
                  agrees to abide by the provisions of Section 3 of this
                  agreement, whether or not the other shareholders of Methylgene
                  give their approval and consent to the amendments to the
                  Shareholders Agreement contemplated thereby.


         10.3     Methylgene shall and shall cause its counsel promptly to
                  review and comment upon the forms of waiver and waiver request
                  letter proposed by Hybridon for the purpose of Hybridon
                  soliciting the waiver by the holders of shares of Methylgene
                  capital stock of rights in the nature of preemption or first
                  refusal which are a precondition of Hybridon's selling its
                  shares to Paul Capital and to recommend such waivers to its
                  shareholders. Furthermore, and subject to compliance with the
                  terms of the Shareholders Agreement, Hybridon agrees, if one
                  or more offers are made to it prior to the later of May 31,
                  2001 and the closing of the transaction contemplated by the
                  Offer, to sell any other shares it owns in the capital of
                  Methylgene to the other shareholders, to Methylgene or to a
                  third party arranged by Methylgene at the same price and on
                  substantially the same commercial terms as set forth in the
                  Offer.


11.      This agreement shall terminate on April 30, 2001 if the transaction
         contemplated in the Offer does not close on or prior to April 30, 2001
         and, save and except for Section 9, no provision of this agreement
         shall survive such termination,.


12.      This mutual release and discharge may be executed in one or more
         counterparts, each of which shall be deemed an original, but all of
         which together shall constitute one and the same instrument. The
         agreements herein are in addition to any other agreements or
         understandings between the parties, which other agreements and
         understandings are not terminated hereby and continue to apply.


13.      The mutual release and discharge is governed by the laws of the
         Province of Quebec.


14.      The present release and discharge is being drafted in English language
         at the request of the parties hereto. La presente quittance a ete
         redigee en langue anglaise a la demande des parties aux presentes.



                                        METHYLGENE INC.


                                        Per:
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                                        HYBRIDON, INC.
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                                        Per:
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                                   SCHEDULE A


   -  Unanimous Shareholders' Agreement dated January 4, 1996, as amended from
      time to time;


   -  Shareholders Agreement dated January 4, 1996, as amended from time to time
      as restated on September 21, 2000 (the "SHAREHOLDERS' AGREEMENT");


   -  License Agreement dated January 4, 1996, as amended from time to time;


   -  License Agreement dated March 12, 1999 between Hybridon and Integrated DNA
      Technologies Inc. ("IDT"), and the letter agreement dated July 26, 1999
      between Methylgene and IDT;


   -  License Agreement dated October 13, 1994 between McGill University and
      Hybridon, as amended from time to time;


   -  License Agreement dated December 15, 1995 between McGill University and
      Hybridon;


   -  License Agreement dated February 1, 1990 between the Worcester Foundation
      for Experimental Biology Inc. and Hybridon and restated September 8, 1993;


   -  Letter Agreement dated February 27, 1998 between Methylgene and McGill
      University;


   -  Letter Agreement dated July 1, 1999 between Methylgene and the University
      of Massachussetts (UMASS); and


   -  All licensed and sublicensed patents.


   -  Letter Agreement dated December 18, 1995 among Hybridon and Worcester
      Foundation for Biomedical Research, Inc. and into which Methylgene
      intervened.


   -  Various confidentiality agreements executed from time to time between
      Methylgene and Hybridon.