SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                               AMENDMENT NO. 1 TO
                                    FORM 8-A

                FOR REGISTRATION OF CERTAIN CLASSES OF SECURITIES
                     PURSUANT TO SECTION 12(b) OR (g) OF THE
                         SECURITIES EXCHANGE ACT OF 1934


                                 Hybridon, Inc.
             (Exact Name of Registrant as Specified in its Charter)


          Delaware                                                04-3072298
(State or Other Jurisdiction                                    (IRS Employer
      of Incorporation)                                      Identification No.)


                345 Vassar Street, Cambridge, Massachusetts 02139
               (Address of Principal Executive Offices) (Zip Code)

If this form relates to the registration of a class of securities pursuant to
Section 12(b) of the Exchange Act and is effective pursuant to General
Instruction A.(c), please check the following box. [ ]

If this form relates to the registration of a class of securities pursuant to
Section 12(g) of the Exchange Act and is effective pursuant to General
Instruction A.(d), please check the following box. [X]

Securities Act registration statement file number
to which this form relates:                             Not applicable
                                                        --------------
                                                        (If applicable)

Securities to be registered pursuant to Section 12(b) of the Act:



          Title of Each Class            Name of Each Exchange on Which
          to be so Registered            Each Class is to be Registered
          -------------------            ------------------------------
                                      
             Not applicable                      Not applicable


Securities to be registered pursuant to Section 12(g) of the Act:

              Common Stock (and associated Series C Stock Purchase
                       Rights), $.001 par value per share
                       ----------------------------------
                                (Title of Class)

ITEM 1. DESCRIPTION OF REGISTRANT'S SECURITIES TO BE REGISTERED.


GENERAL

      Our restated certificate of incorporation, as amended (the "Certificate of
Incorporation") authorizes the issuance of up to 100,000,000 shares of common
stock, par value $0.001 per share, and 5,000,000 shares of preferred stock, par
value $0.01 per share, of which 1,500,000 are designated Series A convertible
preferred stock and 100,000 shares are designated Series C junior participating
preferred stock. The rights and preferences of the remaining authorized
preferred stock may be established from time to time by our board of directors.
As of December 10, 2001, 45,373,616 shares of common stock were outstanding. As
of December 10, 2001, 640,166 shares of Series A convertible preferred stock
were outstanding. Additional shares of Series A convertible preferred stock may
be issued from time to time as dividends on the outstanding Series A convertible
preferred stock. The Series C junior participating preferred stock was
designated on December 10, 2001 in connection with the Rights Plan described
below. No shares of Series C junior participating preferred stock are
outstanding as of the date of this filing.

      The following description of our capital stock is qualified in its
entirety by reference to our Certificate of Incorporation, and amended and
restated bylaws (the "Bylaws"), copies of which have been filed with the
Securities and Exchange Commission.

COMMON STOCK

      Holders of common stock are entitled to one vote for each share held on
all matters submitted to a vote of stockholders and do not have cumulative
voting rights. Accordingly, holders of a majority of the shares of common stock
entitled to vote in any election of directors may elect all of the directors
standing for election. Holders of common stock are entitled to receive
proportionately any dividends as may be declared by our board of directors out
of funds legally available therefor, subject to any preferential dividend rights
of outstanding preferred stock. Upon our liquidation, dissolution or winding up,
the holders of common stock are entitled to receive proportionately our net
assets available after the payment of all debts and other liabilities, including
without limitation liabilities under the unit purchase agreement described
below, and subject to the prior rights of any outstanding preferred stock.
Holders of common stock have no preemptive, subscription, redemption or
conversion rights. The rights, preferences and privileges of holders of common
stock are subject to, and may be adversely affected by, the rights of the
holders of shares of any series of preferred stock which we may designate and
issue in the future.

      Pursuant to the terms of a unit purchase agreement dated as of May 5,
1998, we issued and sold a total of 9,597,476 shares of common stock (the "Put
Shares") at a price of $2.00 per share. Under the terms of the unit purchase
agreement, the initial purchasers (the "Put Holders") of the Put Shares have the
right (the "Put Right") to require us to repurchase the Put Shares. The Put
Right may not be exercised by any Put Holder unless:

      -     we liquidate, dissolve or wind up our affairs pursuant to applicable
            bankruptcy law, whether voluntarily or involuntarily;

      -     all of our indebtedness and obligations, including without
            limitation the indebtedness under our outstanding notes, has been
            paid in full; and


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      -     all rights of the holders of any series or class of capital stock
            ranking prior and senior to the common stock with respect to
            liquidation, including without limitation the Series A convertible
            preferred stock, have been satisfied in full.

      We may terminate the Put Right upon written notice to the Put Holders if
the closing sales price of our common stock exceeds $4.00 per share for the
twenty consecutive trading days prior to the date of notice of termination.
Because the Put Right is not transferable, in the event that a Put Holder has
transferred Put Shares since May 5, 1998, a Put Right with respect to those
shares have terminated. As a consequence of the Put Right, in the event we are
liquidated, holders of shares of common stock that do not have Put Rights with
respect to such shares may receive smaller distributions per share upon our
liquidation than if there were no Put Rights outstanding.

PREFERRED STOCK

      Under the terms of our Certificate of Incorporation, our board of
directors is authorized to issue shares of preferred stock in one or more series
without stockholder approval. Our board of directors has the discretion to
determine the rights, preferences, privileges and restrictions, including voting
rights, dividend rights, conversion rights, redemption privileges and
liquidation preferences, of each series of preferred stock.

      The purpose of authorizing our board of directors to issue preferred stock
and determine its rights and preferences is to eliminate delays associated with
a stockholder vote on specific issuances. The issuance of preferred stock may
provide desirable flexibility in connection with possible acquisitions and other
corporate purposes, but could have the effect of making it more difficult for a
third party to acquire, or could discourage a third party from acquiring, a
majority of our outstanding voting stock.


SHAREHOLDER RIGHTS PLAN

      On December 10, 2001, our Board of Directors, declared a dividend of one
Right for each outstanding share of our common stock to stockholders of record
at the close of business on January 7, 2002 (the "Record Date"). Each Right
entitles the registered holder to purchase from us one one-thousandth of a share
of Series C Junior Participating Preferred Stock, $.01 par value per share (the
"Series C Preferred Stock"), at a Purchase Price of $13.00 in cash, subject to
adjustment. The description and terms of the Rights are set forth in a Rights
Agreement dated December 10, 2001 (the "Rights Agreement") between us and Mellon
Investor Services LLC, as Rights Agent.

      Initially, the Rights are not exercisable and will be attached to all
certificates representing outstanding shares of common stock, and no separate
Rights Certificates will be distributed. The Rights will separate from the
common stock, and the Distribution Date will occur, upon the earlier of (i) 10
business days following the first date of a public announcement that a person or
group of affiliated or associated persons (an "Acquiring Person") has acquired,
or obtained the right to acquire, beneficial ownership of 15% or more of the
outstanding shares of common stock or (ii) 10 business days following the
commencement of a tender offer or exchange offer that would result in a person
or group beneficially owning 15% or more of the outstanding shares of common
stock. The Distribution Date may be deferred in circumstances determined by the
Board of Directors. In addition, certain inadvertent acquisitions and certain
acquisitions of additional shares of Series A Preferred Stock as payment-in-kind
dividends will not trigger the occurrence of the Distribution Date. Until the
Distribution Date (or earlier redemption or expiration of the Rights), (i) the
Rights will be evidenced by the common stock certificates outstanding on the
Record Date, together with the Summary of Rights, or by new common stock
certificates issued after the Record Date which contain a notation incorporating
the Rights Agreement by reference, (ii) the Rights


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will be transferred with and only with such common stock certificates; and (iii)
the surrender for transfer of any certificates for common stock outstanding
(with or without a copy of the Summary of Rights or such notation) will also
constitute the transfer of the Rights associated with the common stock
represented by such certificate.

      The Rights are not exercisable until the Distribution Date and will expire
upon the close of business on December 10, 2011 (the "Final Expiration Date")
unless earlier redeemed or exchanged as described below. As soon as practicable
after the Distribution Date, separate Rights Certificates will be mailed to
holders of record of the common stock as of the close of business on the
Distribution Date and, thereafter, the separate Rights Certificates alone will
represent the Rights. Except as otherwise determined by the Board of Directors,
and except for shares of common stock issued upon exercise, conversion or
exchange of then outstanding options, convertible or exchangeable securities or
other contingent obligations to issue shares or pursuant to any employee benefit
plan or arrangement, only shares of common stock issued prior to the
Distribution Date will be issued with Rights.

      In the event that any Person becomes an Acquiring Person, unless the event
causing the 15% threshold to be crossed is a Permitted Offer (as defined in the
Rights Agreement), then, promptly following the first occurrence of such event,
each holder of a Right (except as provided below and in Section 7(e) of the
Rights Agreement) shall thereafter have the right to receive, upon exercise,
that number of shares of our common stock (or, in certain circumstances, cash,
property or other securities of the Company) which equals the exercise price of
the Right divided by 50% of the current market price (as defined in the Rights
Agreement) per share of common stock at the date of the occurrence of such
event. However, Rights are not exercisable following such event until such time
as the Rights are no longer redeemable by us as described below. Notwithstanding
any of the foregoing, following the occurrence of such event, all Rights that
are, or (under certain circumstances specified in the Rights Agreement) were,
beneficially owned by any Acquiring Person will be null and void. The event
summarized in this paragraph is referred to as a "Section 11(a)(ii) Event."

      For example, at an exercise price of $13.00 per Right, each Right not
owned by an Acquiring Person (or by certain related parties) following a Section
11(a)(ii) Event would entitle its holder to purchase for $13.00 such number of
shares of common stock (or other consideration, as noted above) as equals $13.00
divided by one-half of the current market price (as defined in the Rights
Agreement) of the common stock. Assuming that the common stock had a market
price of $6.50 per share at such time, the holder of each valid Right would be
entitled to purchase four shares of common stock, having a market value of 4 x
$6.50, or $26.00, for $13.00.

      In the event that, at any time after any Person becomes an Acquiring
Person, (i) we are consolidated with, or merged with and into, another entity
and we are not the surviving entity of such consolidation or merger (other than
a consolidation or merger which follows a Permitted Offer) or if we are the
surviving entity, but shares of its outstanding common stock are changed or
exchanged for stock or securities (of any other person) or cash or any other
property, or (ii) more than 50% of our assets or earning power is sold or
transferred, each holder of a Right (except Rights which previously have been
voided as set forth above) shall thereafter have the right to receive, upon
exercise, that number of shares of common stock of the acquiring company which
equals the exercise price of the Right divided by 50% of the current market
price (as defined in the Rights Agreement) of such common stock at the date of
the occurrence of the event. The events summarized in this paragraph are
referred to as "Section 13 Events." A Section 11(a)(ii) Event and Section 13
Events are collectively referred to as "Triggering Events."

      For example, at an exercise price of $13.00 per Right, each valid Right
following a Section 13 Event would entitle its holder to purchase for $13.00
such number of shares of common stock of the acquiring company as equals $13.00
divided by one-half of the current market price (as defined in the Rights


                                      -4-

Agreement) of such common stock. Assuming that such common stock had a market
price of $6.50 per share at such time, the holder of each valid Right would be
entitled to purchase four shares of common stock of the acquiring company,
having a market value of 4 x $6.50, or $26.00, for $13.00.

      At any time after the occurrence of a Section 11(a)(ii) Event, when no
person owns a majority of the common stock, our Board of Directors may exchange
the Rights (other than Rights owned by such Acquiring Person which have become
void), in whole or in part, at an exchange ratio of one share of common stock,
or one one-thousandth of a share of Series C Preferred Stock (or of a share of a
class or series of the Company's preferred stock having equivalent rights,
preferences and privileges), per Right (subject to adjustment).

      The Purchase Price payable, and the number of units of Series C Preferred
Stock or other securities or property issuable, upon exercise of the Rights are
subject to adjustment from time to time to prevent dilution (i) in the event of
a stock dividend on, or a subdivision, combination or reclassification of, the
Series C Preferred Stock, (ii) if holders of the Series C Preferred Stock are
granted certain rights or warrants to subscribe for Series C Preferred Stock or
convertible securities at less than the then-current market price (as defined in
the Rights Agreement) of the Series C Preferred Stock, or (iii) upon the
distribution to holders of the Series C Preferred Stock of evidences of
indebtedness or assets (excluding regular periodic cash dividends paid out of
earnings or retained earnings) or of subscription rights or warrants (other than
those referred to above). The number of Rights associated with each share of
common stock is also subject to adjustment in the event of a stock split of the
common stock or a stock dividend on the common stock payable in common stock or
subdivisions, consolidations or combinations of the common stock occurring, in
any such case, prior to the Distribution Date.

      With certain exceptions, no adjustment in the Purchase Price will be
required until cumulative adjustments amount to at least 1% of the Purchase
Price. No fractional shares of Series C Preferred Stock (other than fractions
which are integral multiples of one one-thousandth of a share of Series C
Preferred Stock) will be issued and, in lieu thereof, an adjustment in cash will
be made based on the market price of the Series C Preferred Stock on the last
trading date prior to the date of exercise.

      Series C Preferred Stock purchasable upon exercise of the Rights will not
be redeemable. Each share of Series C Preferred Stock will be entitled to
receive, when, as and if declared by the Board of Directors, a minimum
preferential quarterly dividend payment of $10 per share or, if greater, an
aggregate dividend of 1,000 times the dividend declared per share of common
stock. In the event of liquidation, the holders of the Series C Preferred Stock
will be entitled to a minimum preferential liquidation payment of $1,000 per
share, plus an amount equal to accrued and unpaid dividends, and will be
entitled to an aggregate payment of 1,000 times the payment made per share of
common stock. Each share of Series C Preferred Stock will have 1,000 votes,
voting together with the common stock. In the event of any merger, consolidation
or other transaction in which common stock is changed or exchanged, each share
of Series C Preferred Stock will be entitled to receive 1,000 times the amount
received per share of common stock. These rights are protected by customary
antidilution provisions. Because of the nature of the Series C Preferred Stock's
dividend, liquidation and voting rights, the value of one one-thousandth of a
share of Series C Preferred Stock purchasable upon exercise of each Right should
approximate the value of one share of common stock.

      At any time prior to the earlier of the tenth Business Day (or such later
date as may be determined by our Board of Directors) after the Stock Acquisition
Date, the we may redeem the Rights in whole, but not in part, at a price of
$0.001 per Right (the "Redemption Price"), payable in cash or stock. Immediately
upon the redemption of the Rights or such earlier time as established by the
Board in the resolution ordering the redemption of the Rights, the Rights will
terminate and the only right of the holders of Rights


                                      -5-

will be to receive the Redemption Price. The Rights may also be redeemable
following certain other circumstances specified in the Rights Agreement.

      Until a Right is exercised, the holder thereof, as such, will have no
rights as a stockholder, including, without limitation, the right to vote or to
receive dividends. Although the distribution of the Rights should not be taxable
to our stockholders or us, stockholders may, depending upon the circumstances,
recognize taxable income in the event that the Rights become exercisable for our
common stock (or other consideration) or for common stock of the acquiring
company as set forth above.

      Any provision of the Rights Agreement, other than the redemption price,
may be amended by the Board prior to such time as the Rights are no longer
redeemable. Once the Rights are no longer redeemable, the Board's authority to
amend the Rights is limited to correcting ambiguities or defective or
inconsistent provisions in a manner that does not adversely affect the interest
of holders of Rights.

      The Rights are intended to protect the our stockholders in the event of an
unfair or coercive offer to acquire us and to provide the Board with adequate
time to evaluate unsolicited offers. The Rights may have anti-takeover effects.
The Rights will cause substantial dilution to a person or group that attempts to
acquire us without conditioning the offer on a substantial number of Rights
being acquired. The Rights, however, should not affect any prospective offeror
willing to make an offer at a fair price and otherwise in the best interests of
the Company and its stockholders, as determined by a majority of the Board. The
Rights should not interfere with any merger or other business combination
approved by the Board.

      This summary description of the Rights does not purport to be complete and
is qualified in its entirety by reference to the Rights Agreement, which is
incorporated herein by reference.

DELAWARE LAW AND OUR CHARTER AND BY-LAWS PROVISIONS

      Our Certificate of Incorporation divides our board of directors into three
classes as nearly equal in size as possible with staggered three-year terms. In
addition, our Certificate of Incorporation provides that directors may be
removed only for cause and only by the affirmative vote of the holders of
two-thirds of our shares of capital stock entitled to vote. Under our
Certificate of Incorporation, any vacancy on our board of directors, including a
vacancy resulting from an enlargement of our board of directors, may only be
filled by vote of a majority of our directors then in office. The classification
of our board of directors and the limitations on the removal of directors and
filling of vacancies could make it more difficult for a third party to acquire,
or discourage a third party from acquiring, control of Hybridon.

      Our Certificate of Incorporation also provides that any action required or
permitted to be taken by our stockholders at an annual meeting or special
meeting of stockholders may only be taken if it is properly brought before the
meeting and may not be taken by written action in lieu of a meeting. Our
Certificate of Incorporation further provides that special meetings of the
stockholders may only be called by our Chief Executive Officer or, if the office
of Chief Executive Officer is vacant, our President, or by the Board of
Directors. Under our Bylaws, in order for any matter to be considered properly
brought before a meeting, a stockholder must comply with the advance notice
requirements set forth in the Bylaws. These provisions could have the effect of
delaying until the next stockholders' meeting stockholder actions which are
favored by the holders of a majority of our outstanding voting securities. These
provisions may also discourage a third party from making a tender offer for our
common stock, because even if third party acquired a majority of our outstanding
voting securities, the third party would be able to take action as a stockholder
(such as electing new directors or approving a merger) only at a duly called
stockholders' meeting, and not by written consent.


                                      -6-

      The General Corporation Law of Delaware provides generally that the
affirmative vote of a majority of the shares entitled to vote on any matter is
required to amend a corporation's certificate of incorporation or by-laws,
unless a corporation's Certificate of Incorporation or Bylaws, as the case may
be, requires a greater percentage. Our Certificate of Incorporation and Bylaws
require the affirmative vote of the holders of at least 75% of the shares of our
capital stock issued and outstanding and entitled to vote to amend or repeal any
of the provisions described in the prior two paragraphs.

      Our Certificate of Incorporation contains provisions permitted under the
General Corporation Law of Delaware relating to the liability of directors. The
provisions eliminate a director's liability for monetary damages for a breach of
fiduciary duty, except in circumstances involving wrongful acts, such as the
breach of a director's duty of loyalty or acts or omissions that involve
intentional misconduct or a knowing violation of law by the director. Further,
our Certificate of Incorporation contains provisions to indemnify our directors
and officers to the fullest extent permitted by the General Corporation Law of
Delaware.

TRANSFER AGENT AND REGISTRAR

      The transfer agent and registrar for our common stock is Mellon Investor
Services LLC.


                                      -7-

ITEM 2. EXHIBITS.



 Exhibit Number         Description
 --------------         -----------
                     
            4.1         Restated Certificate of Incorporation of the Registrant,
                        as amended to date.

            4.2         Amended and Restated By-Laws of the Registrant
                        (incorporated by reference to Exhibits to the
                        Registrant's Registration Statement on Form S-1 (File
                        No. 33-99024)).

            4.3         Rights Agreement dated December 10, 2001 between
                        Hybridon, Inc. and Mellon Investor Services LLC, as
                        rights agent, which includes as Exhibit A the Form of
                        Certificate of Designations of Series C Junior
                        Participating Preferred Stock, as Exhibit B the Form of
                        Rights Certificate and as Exhibit C the Summary of
                        Rights to Purchase Common Stock (incorporated by
                        reference to Exhibit 4.1 of the Company's Current Report
                        on Form 8-K, File No. 0-27352 filed on December 21,
                        2001).



                                    SIGNATURE


Pursuant to the requirements of Section 12 of the Securities Exchange Act of
1934, the Registrant has duly caused this registration statement to be signed on
its behalf by the undersigned, thereto duly authorized.

December 21, 2001                       HYBRIDON, INC.


                                        By:    /s/ Stephen Seiler
                                        Name:  Stephen Seiler
                                        Title: Chief Executive Officer


                                      -8-

                                  Exhibit Index





 Exhibit Number         Description
 --------------         -----------
                     
            4.1         Restated Certificate of Incorporation of the Registrant,
                        as amended to date.

            4.2         Amended and Restated By-Laws of the Registrant
                        (incorporated by reference to Exhibits to the
                        Registrant's Registration Statement on Form S-1 (File
                        No. 33-99024)).

            4.3         Rights Agreement dated December 10, 2001 between
                        Hybridon, Inc. and Mellon Investor Services LLC, as
                        rights agent, which includes as Exhibit A the Form of
                        Certificate of Designations of Series C Junior
                        Participating Preferred Stock, as Exhibit B the Form of
                        Rights Certificate and as Exhibit C the Summary of
                        Rights to Purchase Common Stock (incorporated by
                        reference to Exhibit 4.1 of the Company's Current Report
                        on Form 8-K, File No. 0-27352, filed on December 21,
                        2001).



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