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                                                                   Exhibit 3.1


                                    RESTATED

                          CERTIFICATE OF INCORPORATION

                                       OF

                                 HYBRIDON, INC.


     Hybridon, Inc., a corporation organized and existing under and by virtue of
the General Corporation Law of the State of Delaware, does hereby certify as
follows:

     1. The Corporation filed its original Certificate of Incorporation with the
Secretary of State of Delaware on May 25, 1989, which Certificate of
Incorporation was amended by a Certificate of Amendment of Certificate of
Incorporation filed on February 21, 1990, and amended and restated by a Restated
Certificate of Incorporation filed on June 5, 1990. A Restated Certificate of
Incorporation was filed with the Secretary of State of the State of Delaware on
November 20, 1990, which Restated Certificate of Incorporation was amended by a
Certificate of Amendment of Restated Certificate of Incorporation filed on
October 16, 1991, a Certificate of Amendment of Restated Certificate of
Incorporation filed on March 3, 1992, a Certificate of Amendment of Restated
Certificate of Incorporation filed on March 23, 1992, a Certificate of Amendment
of Restated Certificate of Incorporation filed on October 23, 1992, a
Certificate of Amendment of Restated Certificate of Incorporation


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filed on February 12, 1993, a Certificate of Amendment of Restated Certificate
of Incorporation filed on June 17, 1993, a Certificate of Amendment of Restated
Certificate of Incorporation filed on July 13, 1993, a Certificate of Amendment
of Restated Certificate of Incorporation filed on September 9, 1994, a
Certificate of Amendment of Restated Certificate of Incorporation filed on July
7, 1995, a Certificate of Amendment of Restated Certificate of Incorporation
filed on December 19, 1995, and a Certificate of Retirement of Stock filed on
even date herewith.

     2. At a meeting of the Board of Directors of the Corporation, a resolution
was duly adopted, pursuant to Sections 141(f) and 245 of the General Corporation
Law of the State of Delaware, setting forth a Restated Certificate of
Incorporation of the Corporation and declaring said Restated Certificate of
Incorporation advisable. The resolution setting forth the Restated Certificate
of Incorporation is as follows:

     RESOLVED: That the Restated Certificate of Incorporation of the
Corporation, as amended, be and hereby is amended and restated in its entirety
so that the same shall read as follows:

     FIRST. The name of the Corporation is:

               Hybridon, Inc.

     SECOND. The address of its registered office in the State of Delaware is
     Corporation Trust Center, 1209 Orange Street, in the City of Wilmington,
     County of New Castle. The name of its registered agent at such address is
     The Corporation Trust Company.

     THIRD. The nature of the business or purposes to be conducted or promoted
     by the Corporation is as follows:


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     To engage in any lawful act or activity for which corporations may be
     organized under the General Corporation Law of Delaware.

     FOURTH. The total number of shares of all classes of stock which the
Corporation shall have authority to issues is One Hundred Million (100,000,000)
shares of Common Stock, $.001 par value per share ("Common Stock"), and (ii)
Five Million ($5,000,000)shares of Preferred Stock, $.01 par value per share
("Preferred Stock"), which may be issued from time to time in one or more series
as set forth in Part B of this Articles FOURTH.

     The following is a statement of the designations and the powers, privileges
and rights, and the qualifications, limitations or restrictions thereof in
respect of each class of capital stock of the Corporation.

A. COMMON STOCK.

     1. GENERAL. The voting, dividend and liquidation rights of the holders of
the Common Stock are subject to and qualified by the rights of the holders of
the Preferred Stock of any series as may be designated by the Board of Directors
upon any issuance of the Preferred Stock of any series.

     2. VOTING. The holders of the Common Stock are entitled to one vote for
each share held at all meetings of stockholders (and written actions in lieu of
meetings). There shall be no cumulative voting.

     The number of authorized shares of Common Stock may be increased or
decreased (but not below the number of shares thereof then outstanding) by the
affirmative vote of the holders of a majority of the stock of the Corporation
entitled to vote, irrespective of the provisions of Section 242(b)(2) of the
General Corporation Law of Delaware.

     3. DIVIDENDS. Dividends may be declared and paid on the Common Stock from
funds lawfully available therefor as and when determined by the Board of
Directors and subject to any preferential dividend rights of any then
outstanding Preferred Stock.

     4. LIQUIDATION. Upon the dissolution or liquidation of the Corporation,
whether voluntary or involuntary, holders of Common Stock will be entitled to
receive all assets of the Corporation available for distribution to its
stockholders,


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subject to any preferential rights of any then outstanding
Preferred Stock.

B. PREFERRED STOCK.

     Preferred Stock may be issued from time to time in one or more series, each
of such series to have such terms as stated or expressed herein and in the
resolution or resolutions providing for the issue of such series adopted by the
Board of Directors of the Corporation as hereinafter provided. Any shares of
Preferred Stock which may be redeemed, purchased or acquired by the Corporation
may be reissued except as otherwise provided by law. Different series of
Preferred Stock shall not be construed to constitute different classes of shares
for the purposes of voting by classes unless expressly provided.

     Authority is hereby expressly granted to the Board of Direc tors from time
to time to issue the Preferred Stock in one or more series, and in connection
with the creation of any such series, by resolution or resolutions providing for
the issue of the shares thereof, to determine and fix such voting powers, full
or limited, or no voting powers, and such designations, preferences and relative
participating, optional or other special rights, and qualifications, limitations
or restrictions thereof, including without limitation thereof, dividend rights,
conversion rights, redemption privileges and liquidation preferences, as shall
be stated and expressed in such resolutions, all to the full extent now or
hereafter permitted by the General Corporation Law of Delaware. Without limiting
the generality of the foregoing, the resolutions providing for issuance of any
series of Preferred Stock may provide that such series shall be superior or rank
equally or be junior to the Preferred Stock of any other series to the extent
permitted by law. Except as otherwise specifically provided in this Certificate
of Incorporation, no vote of the holders of the Preferred Stock or Common Stock
shall be a prerequisite to the issuance of any shares of any series of the
Preferred Stock authorized by and complying with the conditions of the
Certificate of Incorporation, the right to have such vote being expressly waived
by all present and future holders of the capital stock of the Corporation.

     FIFTH. The name and mailing address of the sole incorporator are as
follows:

             NAME                           MAILING ADDRESS
             ----                           ---------------

         David P. Johst                     60 State Street
                                            Boston, MA  02109


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     SIXTH. In furtherance of and not in limitation of powers conferred by
statute, it is further provided:

          1. Election of directors need not be by written ballot.

          2. The Board of Directors is expressly authorized to adopt, amend or
repeal the By-Laws of the Corporation.

     SEVENTH. Whenever a compromise or arrangement is proposed between this
corporation and its creditors or any class of them and/or between this
corporation and its stockholders or any class of them, any court of equitable
jurisdiction within the State of Delaware may, on the application in a summary
way of this corporation or of any creditor or stockholder thereof, or on the
application of any receiver or receivers appointed for this corporation under
the provisions of section 291 of Title 8 of the Delaware Code or on the
application of trustees in dissolution or of any receiver or receivers appointed
for this corporation under the provisions of section 279 of Title 8 of the
Delaware Code order a meeting of the creditors or class of creditors, and/or of
the stockholders or class of stockholders of this corporation, as the case may
be, to be summoned in such manner as the said court directs. If a majority in
number representing three-fourths in value of the creditors or class of
creditors, and/or of the stockholders or class of stockholders of this
corporation, as the case may be, agree to any compromise or arrangement and to
any promise or arrangement, the said compromise or arrangement and the said
reorganization shall, if sanctioned by the court to which the said application
has been made, be binding on all the creditors or class of creditors, and/or on
all the stockholders or class of stockholders, of this corporation, as the case
may be, and also on this corporation.

     EIGHTH. Except to the extent that the General Corporation Law of the State
of Delaware prohibits the elimination or limitation of liability of directors
for breaches of fiduciary duty, no director of the Corporation shall be
personally liable to the Corporation or its stockholders for monetary damages
for any breach of fiduciary duty as a director, notwithstanding any provision of
law imposing such liability. No amendment to or repeal of this provision shall
apply to or have any effect on the liability or alleged liability of any
director of the Corporation for or with respect to any acts or omissions of such
director occurring prior to such amendment.

     NINTH. 1. ACTION, SUITS AND PROCEEDINGS OTHER THAN BY


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OR IN THE RIGHT OF THE CORPORATION. The Corporation shall indemnify each person
who was or is a party or is threatened to be made a party to any threatened,
pending or completed action, suit or proceeding, whether civil, criminal,
administrative or investigative (other than an action by or in the right of the
Corporation), by reason of the fact that he is or was, or has agreed to become,
a director or officer of the Corporation, or is or was serving, or has agreed to
serve, at the request of the Corporation, as a director, officer or trustee of,
or in a similar capacity with, another corporation, partnership, joint venture,
trust or other enterprise (including any employee benefit plan) (all such
persons being referred to hereafter as an "Indemnitee"), or by reason of any
action alleged to have been taken or omitted in such capacity, against all
expenses (including attorneys' fees) judgment, fines and amounts paid in
settlement actually and reasonably incurred by him or on his behalf in
connection with such action, suit or proceeding and any appeal therefrom, if he
acted in good faith and in a manner he reasonably believed to be in, or not
opposed to, the best interests of the Corporation, and, with respect to any
criminal action or proceeding, had no reasonable cause to believe his conduct
was unlawful. The termination of any action, suit or proceeding by judgment,
order, settlement, conviction or upon a plea of NOLO CONTENDERE or its
equivalent, shall not, of itself, create a presumption that the person did not
act in good faith and in a manner which he reasonably believed to be in, or not
opposed to, the best interests of the Corporation, and, with respect to any
criminal action or proceeding, had reasonable cause to believe that his conduct
was unlawful. Notwithstanding anything to the contrary in this Article, except
as set forth in Section 6 below, the Corporation shall not indemnify an
Indemnitee seeking indemnification in connection with a proceeding (or part
thereof) initiated by the Indemnitee unless the initiation thereof was approved
by the Board of Directors of the Corporation.

     2. ACTIONS OR SUITS BY OR IN THE RIGHT OF THE CORPORATION. The Corporation
shall indemnify any Indemnitee who was or is a party or is threatened to be made
a party to any threatened, pending or completed action or suit by or in the
right of the Corporation to procure a judgment in its favor by reason of the
fact that he is or was, or has agreed to become, a director or officer of the
Corporation, or is or was serving, or has agreed to serve, at the request of the
Corporation, as a director, officer or trustee of, or in a similar capacity
with, another corporation, partnership, joint venture, trust or other enterprise
(including any employee benefit plan), or by reason of any action alleged to
have been taken or omitted in such capacity, against all expenses (including
attorneys' fees) and


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amounts paid in settlement actually and reasonably incurred by him or on his
behalf in connection with such action, suit or proceeding and any appeal
therefrom, if he acted in good faith and in a manner he reasonably believed to
be in, or not opposed to, the best interests of the Corporation, except that no
indemnification shall be made in respect of any claim, issue or matter as to
which such person shall have been adjudged to be liable to the Corporation
unless and only to the extent that the Court of Chancery of Delaware or the
court in which such action or suit was brought shall determine upon application
that, despite the adjudication of such liability but in view of all the
circumstances of the case, such person is fairly and reasonably entitled to
indemnity for such expenses (including attorneys' fees) which the Court of
Chancery of Delaware or such other court shall deem proper.

     3. INDEMNIFICATION FOR EXPENSES OF SUCCESSFUL PARTY. Notwithstanding the
other provisions of this Article, to the extent that an Indemnitee has been
successful, on the merits or otherwise, in defense of any action, suit or
proceeding referred to in Sections 1 and 2 of this Article, or in defense of any
claim, issue or matter therein, or on appeal from any such action, suit or
proceeding, he shall be indemnified against all expenses (including attorneys'
fees) actually and reasonably incurred by him or on his behalf in connection
therewith. Without limiting the foregoing, if any action, suit or proceeding is
disposed of, on the merits or otherwise (including a disposition without
prejudice), without (i) the disposition being adverse to the Indemnitee, (ii) an
adjudication that the Indemnitee was liable to the Corporation, (iii) a plea of
guilty or NOLO CONTENDERE by the Indemnitee, (iv) an adjudication that the
Indemnitee did not act in good faith and in a manner he reasonably believed to
be in or not opposed to the best interests of the Corporation, and (v) with
respect to any criminal proceeding, an adjudication that the Indemnitee had
reasonable cause to believe his conduct was unlawful, the Indemnitee shall be
considered for the purposes hereof to have been wholly successful with respect
thereto.

     4. NOTIFICATION AND DEFENSE OF CLAIM. As a condition precedent to his right
to be indemnified, the Indemnitee must notify the Corporation in writing as soon
as practicable of any action, suit, proceeding or investigation involving him
for which indemnity will or could be sought. With respect to any action, suit,
proceeding or investigation of which the Corporation is so notified, the
Corporation will be entitled to participate therein at its own expense and/or to
assume the defense thereof at its


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own expense, with legal counsel reasonably acceptable to the Indemnitee. After
notice from the Corporation to the Indemnitee of its election so to assume such
defense, the Corporation shall not be liable to the Indemnitee for any legal or
other expenses subsequently incurred by the Indemnitee in connection with such
claim, other than as provided below in this Section 4. The Indemnitee shall have
the right to employ his own counsel in connection with such claim, but the fees
and expenses of such counsel incurred after notice from the Corporation of its
assumption of the defense thereof shall be at the expense of the Indemnitee
unless (i) the employment of counsel by the Indemnitee has been authorized by
the Corporation, (ii) counsel to the Indemnitee shall have reasonably concluded
that there may be a conflict of interest or position on any significant issue
between the Corporation and the Indemnitee in the conduct of the defense of such
action or (iii) the Corporation shall not in fact have employed counsel to
assume the defense of such action, in each of which cases the fees and expenses
of counsel for the Indemnitee shall be at the expense of the Corporation, except
as otherwise expressly provided by this Article. The Corporation shall not be
entitled, without the consent of the Indemnitee, to assume the defense of any
claim brought by or in the right of the Corporation or as to which counsel for
the Indemnitee shall have reasonably made the conclusion provided for in clause
(ii) above.

     5. ADVANCE OF EXPENSES. Subject to the provisions of Section 6 below, in
the event that the Corporation does not assume the defense pursuant to Section 4
of this Article of any action, suit, proceeding or investigation of which the
Corporation receives notice under this Article, any expenses (including
attorneys' fees) incurred by an Indemnitee in defending a civil or criminal
action, suit, proceeding or investigation or any appeal therefrom shall be paid
by the Corporation in advance of the final disposition of such matter, PROVIDED,
HOWEVER, that the payment of such expense incurred by an Indemnitee in advance
of the final disposition of such matter shall be made only upon receipt of an
undertaking by or on behalf of the Indemnitee to repay all amounts so advanced
in the event that it shall ultimately be determined that the Indemnitee is not
entitled to be indemnified by the Corporation as authorized in this Article.
Such undertaking may be accepted without reference to the financial ability of
such person to make such repayment.

     6. PROCEDURE FOR INDEMNIFICATION. In order to obtain indemnification or
advancement of expenses pursuant to Section 1, 2, 3 or 5 of this Article, the
Indemnitee shall submit to the Corporation a written request, including in such
request such documentation and information as is reasonably available to the
Indemnitee and is reasonably necessary to determine whether and


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to what extent the Indemnitee is entitled to indemnification or advancement of
expenses. Any such indemnification or advancement of expenses shall be made
promptly, and in any event within 60 days after receipt by the Corporation of
the written request of the Indemnitee, unless with respect to requests under
Section 1, 2 or 5 the Corporation determines, by clear and convincing evidence,
within such 60-day period that the Indemnitee did not meet the applicable
standard of conduct set forth in Section 1 or 2, as the case may be. Such
determination shall be made in each instance by (a) a majority vote of a quorum
of the directors of the Corporation consisting of persons who are not at that
time parties to the action, suit or proceeding in question ("disinterested
directors'), (b) if no such quorum is obtainable, a majority vote of a committee
of two or more disinterested directors, (c) a majority vote of a quorum of the
outstanding shares of stock of all classes entitled to vote for directors,
voting as a single class, which quorum shall consist of stockholders who are not
at that time parties to the action, suit or proceeding in question, (d)
independent legal counsel (who may be regular legal counsel to the Corporation),
or (e) a court of competent jurisdiction.

     7. REMEDIES. The right to indemnification or advances as granted by this
Article shall be enforceable by the Indemnitee in any court of competent
jurisdiction if the Corporation denies such request, in whole or in part, or if
no disposition thereof is made within the 60-day period referred to above in
Section 6. Unless otherwise provided by law, the burden of proving that the
Indemnitee is not entitled to indemnification or advanced of expenses under this
Article shall be on the Corporation. Neither the failure of the Corporation to
have made a determination prior to the commencement of such action that
indemnification is proper in the circumstances because the Indemnitee has met
the applicable standard of conduct, nor an actual determination by the
Corporation pursuant to Section 6 that the Indemnitee has not met such
applicable standard of conduct, shall be a defense to the action or create a
presumption that the Indemnitee has not met the applicable standard of conduct.
The Indemnitee's expenses (including attorneys' fees) incurred in connection
with successfully establishing his right to indemnification, in whole or in
part, in any such proceeding shall also be indemnified by the Corporation.

     8. SUBSEQUENT AMENDMENT. No amendment, termination or repeal of this
Article or of the relevant provisions of the General Corporation Law of Delaware
or any other applicable laws shall affect or diminish in any way the rights of
any Indemnitee


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to indemnification under the provisions hereof with respect to any action, suit,
proceeding or investigation arising out of or relating to any actions,
transactions or facts occurring prior to the final adoption of such amendment,
termination or repeal.

     9. OTHER RIGHTS. The indemnification and advancement of expenses provided
by this Article shall not be deemed exclusive of any other rights to which an
Indemnitee seeking indemnification or advancement of expenses may be entitled
under any law (common or statutory), agreement or vote of stockholders or
disinterested directors or otherwise, both as to action in his official capacity
and as to action in any other capacity while holding office for the Corporation,
and shall continue as to an Indemnitee who has ceased to be a director or
officer, and shall inure to the benefit of the estate, heirs, executors and
administrators of the Indemnitee. Nothing contained in this Article shall be
deemed to prohibit, and the Corporation is specifically authorized to enter
into, agreements with officers and directors providing indemnification rights
and procedures different from those set forth in this Article. In addition, the
Corporation may, to the extent authorized from time to time by its Board of
Directors, grant indemnification rights to other employees or agents of the
Corporation or other persons serving the Corporation and such rights may be
equivalent to, or greater or less than, those set forth in this Article.

     10. PARTIAL INDEMNIFICATION. If an Indemnitee is entitled under any
provision of this Article to indemnification by the Corporation for some or a
portion of the expenses (including attorneys' fees), judgments, fines or amounts
paid in settlement actually and reasonably incurred by him or on his behalf in
connection with any action, suit, proceeding or investigation and any appeal,
therefrom but not, however, for the total amount thereof, the Corporation shall
nevertheless indemnify the Indemnitee for the portion of such expenses
(including attorneys' fees), judgments, fines or amounts paid in settlement to
which the Indemnitee is entitled.

     11. INSURANCE. The Corporation may purchase and maintain insurance, at its
expense, to protect itself and any director, officer, employee or agent of the
Corporation or another corporation, partnership, joint venture, trust or other
enterprise (including any employee benefit plan) against any expense, liability
or loss incurred by him in any such capacity, or arising out of his status as
such, whether or not the Corporation would have the power to indemnify such
person against such expense, liability or loss under the General Corporation law
of Delaware.


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     12. MERGER OR CONSOLIDATION. If the Corporation is merged into or
consolidated with another corporation and the Corporation is not the surviving
corporation, the surviving corporation shall assume the obligations of the
Corporation under this Article with respect to any action, suit, proceeding or
investigation arising out of or relating to any actions, transactions or facts
occurring prior to the date of such merger or consolidation.

     13. SAVINGS CLAUSE. If this Article or any portion hereof shall be
invalidated on any ground by any court of competent jurisdiction, then the
Corporation shall nevertheless indemnify each Indemnitee as to any expenses
(including attorneys' fees) judgments, fines and amounts paid in settlement in
connection with any action, suit, proceeding or investigation, whether civil,
criminal or administrative, including an action by or in the right of the
Corporation, to the fullest extent permitted by any applicable portion of this
Article that shall not have been invalidated and to the fullest extent permitted
by applicable law.

     14. DEFINITIONS. Terms used herein and defined in Section 145(h) and
Section 145(i) of the General Corporation Law of Delaware shall have the
respective meanings assigned to such terms in such Section 145(h) and Section
145(i).

     15. SUBSEQUENT LEGISLATION. If the General Corporation Law of Delaware is
amended after adoption of this Article to expand further the indemnification
permitted to Indemnitees, then the Corporation shall indemnify such persons to
the fullest extent permitted by the General Corporation Law of Delaware, as so
amended.

     TENTH. The Corporation reserves the right to amend, alter, change or repeal
any provision contained in this Restated Certificate of Incorporation, in the
manner now or hereafter prescribed by statute and this Restated Certificate of
Incorporation, and all rights conferred upon stockholders herein are granted
subject to this reservation.

     ELEVENTH. This Article is inserted for the management of the business and
for the conduct of the affairs of the Corporation and shall not become effective
until the closing of the sale of shares of Common Stock in an underwritten
public offering pursuant to an effective registration statement under the
Securities Act of 1933, as amended, resulting in at least $10,000,000 of gross
proceeds to the Corporation (a "Public Offering").


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     1. NUMBER OF DIRECTORS. The number of directors of the Corporation shall
not be less than three. The exact number of directors within the limitations
specified in the preceding sentence shall be fixed from time to time by, or in
the manner provided in, the Corporation's By-Laws.

     2. CLASSES OF DIRECTORS. The Board of Directors shall be and is divided
into three classes: Class I, Class II and Class III. No one class shall have
more than one director more than any other class. If a fraction is contained in
the quotient arrived at by dividing the designated number of directors by three,
then, if such fraction is one-third, the extra director shall be a member of
Class II, and if such fraction is two-thirds, one of the extra directors shall
be a member of Class I and one of the extra directors shall be a member of Class
II, unless otherwise provided from time to time by resolution adopted by the
Board of Directors.

     3. ELECTION OF DIRECTORS. Elections of directors need not be by written
ballot except as and to the extent provided in the By-Laws of the Corporation.

     4. TERMS OF OFFICE. Each director shall serve for a term ending on the date
of the third annual meeting following the annual meeting at which such director
was elected; PROVIDED, that each initial director in Class I shall serve for a
term ending on the date of the annual meeting in 1996; each initial director in
Class II shall serve for a term ending on the date of the annual meeting in
1997; and each initial director in Class III shall serve for a term ending on
the date of the annual meeting in 1998; and PROVIDED FURTHER, that the term of
each director shall be subject to the election and qualification of his
successor and to his earlier death, resignation or removal.

     5. ALLOCATION OF DIRECTORS AMONG CLASSES IN THE EVENT OF INCREASES OR
DECREASES IN THE NUMBER OF DIRECTORS. In the event of any increase or decrease
in the authorized number of directors, (i) each director then serving as such
shall nevertheless continue as a director of the class of which he is a member
and (ii) the newly created or eliminated directorships resulting from such
increase or decrease shall be apportioned by the Board of Directors among the
three classes of directors so as to ensure that no one class has more than one
director more than any other class. To the extent possible, consistent with the
foregoing rule, any newly created directorships shall be added to those classes
whose terms of office are to expire at the latest dates following such
allocation, and any newly eliminated


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directorships shall be subtracted from those classes whose terms of offices are
to expire at the earliest dates following such allocation, unless otherwise
provided from time to time by resolution adopted by the Board of Directors.

     6. QUORUM; ACTION AT MEETING. A majority of the directors at any time in
office shall constitute a quorum for the transaction of business. In the event
one or more of the directors shall be disqualified to vote at any meeting, then
the required quorum shall be reduced by one for each director so disqualified,
provided that in no case shall less than one-third of the number of directors
fixed pursuant to Section 1 above constitute a quorum. If at any meeting of the
Board of Directors there shall be less than such a quorum, a majority of those
present may adjourn the meeting from time to time. Every act or decision done or
made by a majority of the directors present at a meeting duly held at which a
quorum is present shall be regarded as the act of the Board of Directors unless
a greater number is required by law, by the By-Laws of the Corporation or by
this Restated Certificate of Incorporation.

     7. REMOVAL. Directors of the Corporation may be removed only for cause by
the affirmative vote of the holders of at least two-thirds of the shares of the
capital stock of the Corporation issued and outstanding and entitled to vote.

     8. VACANCIES. Any vacancy in the Board of Directors, however occurring,
including a vacancy resulting from an enlargement of the board, shall be filled
only by a vote of a majority of the directors then in office, although less than
a quorum, or by a sole remaining director. A director elected to fill a vacancy
shall be elected to hold office until the next election of the class for which
such director shall have been chosen, subject to the election and qualification
of his successor and to his earlier death, resignation or removal.

     9. STOCKHOLDER NOMINATIONS AND INTRODUCTION OF BUSINESS, ETC. Advance
notice of stockholder nominations for election of directors and other business
to be brought by stockholders before a meeting of stockholders shall be given in
the manner provided by the By-Laws of the Corporation.

     10. AMENDMENTS TO ARTICLE. Notwithstanding any other provisions of law,
this Restated Certificate of Incorporation or the By-Laws of the Corporation,
and notwithstanding the fact that a lesser percentage may be specified by law,
the affirmative vote


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of the holders of at least seventy-five percent (75%) of the shares of capital
stock of the Corporation issued and outstanding and entitled to vote shall be
required to amend or repeal, or to adopt any provision inconsistent with, this
Article ELEVENTH.

     TWELFTH. Until the closing of a Public Offering, any action which is
required to be taken or which may be taken at any annual or special meeting of
stockholders of the Corporation may be taken without a meeting, without prior
notice and without a vote, if a consent in writing, setting forth the action so
taken, is signed by the holders of outstanding stock having not less than the
minimum number of votes that would be necessary to authorize or take such action
at a meeting at which all shares entitled to vote on such action were present
and voted. Effective upon the closing of a Public Offering, stockholders of the
Corporation may not take any action by written consent in lieu of a meeting.
Notwithstanding any other provisions of law, the Restated Certificate of
Incorporation or the By-Laws of the Corporation, and notwithstanding the fact
that a lesser percentage may be specified by law, the affirmative vote of the
holders of at least seventy-five percent (75%) of the shares of capital stock of
the Corporation issued and outstanding and entitled to vote shall be required to
amend or repeal, or to adopt any provision inconsistent with, this Article
TWELFTH.

     THIRTEENTH. Effective upon the closing of a Public Offering, special
meetings of stockholders may be called at any time by only the Chief Executive
Officer (or if there is no Chief Executive Officer, the President) or the Board
of Directors. Business transacted at any special meeting of stockholders shall
be limited to matters relating to the purpose or purposes stated in the notice
of meeting. Notwithstanding any other provision of law, this Restated
Certificate of Incorporation or the By-Laws of the Corporation, as amended, and
notwithstanding the fact that a lesser percentage may be specified by law, the
affirmative vote of the holders of at least seventy-five percent (75%) of the
shares of capital stock of the Corporation issued and outstanding and entitled
to vote shall be required to amend or repeal, or to adopt any provision
inconsistent with this Article THIRTEENTH.


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     IN WITNESS WHEREOF, the Corporation has caused its corporate seal to be
affixed hereto and this Restated Certificate of Incorporation to be signed by
its Chairman this 28TH March, 1996.


                                        HYBRIDON, INC.



                                        By: /s/ E. Andrews Grinstead, III
                                            ----------------------------------
                                            Chairman


[Corporate Seal]



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                            CERTIFICATE OF AMENDMENT
                                       OF
                                    RESTATED
                          CERTIFICATE OF INCORPORATION
                                OF HYBRIDON, INC.

                     Pursuant to Section 242 of the General
                    Corporation Law of the State of Delaware

         --------------------------------------------------------------

     HYBRIDON, INC. (the "Corporation"), organized and existing under and by
virtue of the General Corporation Law of the State of Delaware, does hereby
certify as follows:

     By written action of the Board of Directors of the Corporation, dated
October 20, 1997, the Board of Directors duly adopted resolutions pursuant to
Sections 141(f) and 242 of the General Corporation Law of the State of Delaware
setting forth an amendment to the Restated Certificate of Incorporation of the
Corporation, as amended, and declaring said amendment to be advisable. The
stockholders of the Corporation duly approved, pursuant to said Section 242,
said proposed amendment at a Special Meeting of Stockholders held on November
18, 1997. The resolution setting forth the amendment to the Restated Certificate
of Incorporation is as follows:



RESOLVED:      That, subject to stockholder approval, the following paragraph be
               inserted prior to the first paragraph of Article FOURTH of the
               Certificate of Incorporation:

                    "That upon the filing date of the Certificate of Amendment
               of Restated Certificate of Incorporation of the Corporation (the
               "Effective Date"), a one-for-five reverse split of the
               Corporation's Common Stock (as defined below) shall become
               effective, such that each five shares of Common Stock outstanding
               and held of record by each stockholder of the Corporation
               (including treasury shares) 


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               immediately prior to the Effective Date shall represent one share
               of Common Stock from and after the Effective Date."

     IN WITNESS WHEREOF, the Corporation has caused this Certificate of
Amendment to be executed by its Chairman of the Board of Directors, President
and Chief Executive Officer this 10th day of December, 1997. 



                                   HYBRIDON, INC.


                                   By: /s/  E. Andrews Grinstead, III
                                       --------------------------------------
                                        E. Andrews Grinstead, III
                                        Chairman of the Board of Directors,
                                        President and Chief Executive Officer







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