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                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549
                                        
                                  FORM 12b-25
                                        
                          NOTIFICATION OF LATE FILING
                                        
                         Commission File Number 0-27352



(Check one)

[ ]  Form 10-K      [ ]  Form 11-K
[ ]  Form 20-F      [X]  Form 10-Q      [ ]  Form N-SAR

     For Period Ended:        September 30, 1997

[ ]  Transition Report on Form 10-K
[ ]  Transition Report on Form 20-F

[ ]  Transition Report on Form 11-K
[ ]  Transition Report on Form 10-Q
[ ]  Transition Report on Form N-SAR

     For the Transition Period Ended: __________________

     Read attached instruction sheet before preparing form. Please print or
type.

     Nothing in this form shall be construed to imply that the Commission has
verified any information contained herein.

     If the notification relates to a portion of the filing checked above,
identify the item(s) to which the notification relates:_________________________
________________________________________________________________________________
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                                     PART I
                             REGISTRANT INFORMATION


Full name of registrant       Hybridon, Inc.

Address of principal executive office (Street and number)  620 Memorial Drive

City, state and zip code      Cambridge, MA 02139


                                    PART II
                             RULE 12b-25(b) AND (c)


     If the subject report could not be filed without unreasonable effort or
expense and the registrant seeks relief pursuant to Rule 12b-25(b), the
following should be completed. (Check box if appropriate.)

     [X]  (a) The reasons described in reasonable detail in Part III of this
form could not be eliminated without unreasonable effort or expense;

     [X]  (b) The subject annual report, semi-annual report, transition report
on Forms 10-K, 20-F, 11-K or Form N-SAR, or portion thereof will be filed on or
before the 15th calendar day following the prescribed due date; or the subject
quarterly report or transition report on Form 10-Q or portion thereof will be
filed on or before the fifth calendar day following the prescribed due date; and

     [ ]  (c) The accountant's statement or other exhibit required by Rule
12b-25(c) has been attached if applicable.


                                    PART III
                                    NARRATIVE

     State below in reasonable detail the reasons why Form 10-K, 11-K, 20-F,
10-Q, N-SAR or the transition report portion thereof could not be filed within
the prescribed time period. (Attach extra sheets if needed.)

     The Registrant's Quarterly Report on Form 10-Q for the quarter ended
September 30, 1997 could not be filed within the prescribed time period
because certain information and data relating to and necessary for the
completion of the Registrant's financial statements and management's discussion
and analysis of financial condition and results of operations could not be
obtained by the Registrant within such time period without unreasonable effort
or expense.
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                                    PART IV
                               OTHER INFORMATION

     (1)  Name and telephone number of person to contact in regard to this
notification.

          E. Andrews Grinstead, III               (617) 528-7000
                   (Name)                 (Area Code) (Telephone Number)

     (2)  Have all other periodic reports required under Section 13 or 15(d) or
the Securities Exchange Act of 1934 or Section 30 of the Investment Company Act
of 1940 during the preceding 12 months or for such shorter period that the
registrant was required to file such report(s) been filed? If the answer is no,
identify report(s).

                                        [X] Yes        [ ] No

     (3)  Is it anticipated that any significant change in results of
operations from the corresponding period for the last fiscal year will be
reflected by the earnings statements to be included in the subject report or
portion thereof?

                                        [X] Yes        [ ] No

     If so: attach an explanation of the anticipated change, both narratively
and quantitatively, and, if appropriate, state the reasons why a reasonable
estimate of the results cannot be made.

     The Registrant reported net losses for the three months and nine months
ended September 30, 1996 of $11,496,000 and $32,458,000, respectively. As
reported in the Company's 10-Q for the quarter ended June 30, 1997, the Company
incurred a net loss for the six months ended June 30, 1997 of $31,543,000. It
is anticipated that the Company will experience significantly greater net
losses for the nine months ended September 30, 1997 than for the nine months
ended September 30, 1996.
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                                 HYBRIDON, INC.
                  (Name of Registrant as Specified in Charter)


Has caused this notification to be signed on its behalf by the undersigned
thereunto duly authorized.


Date: November 17, 1997                   By: /s/ E. Andrews Grinstead, III
                                              --------------------------------- 
                                              E. Andrews Grinstead, III
                                              Chairman, President and 
                                              Chief Executive Officer

          INSTRUCTION. The form may be signed by an executive officer of the
     registrant or by any other duly authorized representative. The name and
     title of the person signing the form shall be typed or printed beneath the
     signature. If the statement is signed on behalf of the registrant by an
     authorized representative (other than an executive officer), evidence of
     the representative's authority to sign on behalf of the registrant shall be
     filed with the form.


                                   ATTENTION


     Intentional misstatements or omissions of fact constitute Federal criminal
violations (SEE 18 U.S.C. 1001).

                              GENERAL INSTRUCTIONS

     1.   This form is required by Rule 12b-25 of the General Rules and
Regulations under the Securities Exchange Act of 1934.

     2.   One signed original and four conformed copies of this form and
amendments thereto must be completed and filed with the Securities and Exchange
Commission, Washington, DC 20549, in accordance with Rule 0-3 of the General
Rules and Regulations under the Act. The information contained in or filed with
the form will be made a matter of the public record in the Commission files.

     3.   A manually signed copy of the form and amendments thereto shall be
filed with each national securities exchange on which any class of securities
of the registrant is registered.

     4.   Amendments to the notifications must also be filed on Form 12b-25 but
need not restate information that has been correctly furnished. The form shall
be clearly identified as an amended notification.

     5.   ELECTRONIC FILERS. This form shall not be used by electronic filers
unable to timely file a report solely due to electronic difficulties. Filers
unable to submit a report within the time period prescribed due to difficulties
in electronic filing should comply with either Rule 201 or Rule 202 or
Regulation S-T or apply for an adjustment in filing date pursuant to Rule
13(b) of Regulation S-T.