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                                  UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

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                                    FORM 8-K

                                 CURRENT REPORT

                     PURSUANT TO SECTION 13 OR 15(d) OF THE
                         SECURITIES EXCHANGE ACT OF 1934

        Date of Report (Date of earliest event reported): May 5, 1998


                                     0-27352
                            (Commission File Number)

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                                 HYBRIDON, INC.
             (Exact name of registrant as specified in its charter)

        Delaware                                            3072298
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  (State of Incorporation)                               (IRS Employer
                                                      Identification Number)

               620 Memorial Drive, Cambridge, Massachusetts 02139
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              (Address of registrant's principal executive office)

                                 (617) 528-7000
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                         (Registrant's telephone number)

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ITEM 5. OTHER EVENTS

         On May 6, 1998 Hybridon,  Inc. (the "Company") issued the press release
attached hereto as Exhibit 99.1.

ITEM 7. FINANCIAL STATEMENTS AND EXHIBITS


        Exhibit No.                       Title
        -----------                       -----

        99.1                       Press Release Dated May 6, 1998


ITEM 9. SALES OF EQUITY SECURITIES PURSUANT TO REGULATION S

        On May 5, 1998,  (the  "Closing  Date"),  the  Company  closed a private
placement (the "Offering") of approximately  3.2 million shares of common stock,
par value $.001 per share,  of the Company (the "Common  Stock"),  sold at $2.00
per share,  and warrants (the "Equity  Warrants") to purchase Common Stock,  for
aggregate gross proceeds of approximately  $6.3 miliion.  The securities sold in
the Offering (the "Offering  Securities")  were issued in offshore  transactions
pursuant to  Regulation  S  promulgated  under the  Securities  Act of 1933,  as
amended (the "Securities  Act"). The purchasers of the Offering  Securities were
"accredited  investors"  (as  defined  in  Regulation  D  promulgated  under the
Securities Act).

        The Equity Warrants are convertible  into the amount of shares of Common
Stock  equal to 25% of the  number of shares of Common  Stock  purchased  in the
Offering,  and are  exercisable  at $2.40 per  share for a period of five  years
commencing  on the Closing Date.  The Equity  Warrants are not subject to a call
provision.

        In addition,  on May 5, 1998, the Company closed a private  placement of
(i)  approximately  3.6 million  shares of Common Stock and warrants to purchase
Common  Stock and (ii)  approximately  114,300  shares  of Series A  Convertible
Preferred Stock, par value $.01 per share (the "Series A Preferred Stock"), sold
at $70 per share, and warrants to purchase Common Stock, to accredited investors
pursuant to Section 4(2) of the Securities  Act.  Furthermore,  by press release
dated May 6, 1998,  the  Company  announced  that  approximately  $48.6  million
principal  amount  of its 9%  Convertible  Subordinated  Notes due 2004 (the "9%
Notes") had been  tendered to the Company to be exchanged for shares of Series A
Preferred  Stock and warrants to purchase Common Stock pursuant to the Company's
exchange offer,  leaving only  approximately $1.4 million principal amount of 9%
Notes  outstanding.  Finally,  by press release  dated May 6, 1998,  the Company
announced  that  all  of  the  recent  purchasers  of its  Units  (the  "Units")
consisting  of 14%  Notes  due 2007 and  Common  Stock  warrants  had  agreed to
exchange such Units for Common Stock (priced at $2.00 per share) and warrants to
purchase Common Stock.




                                   SIGNATURES


         Pursuant to the  requirements  of the Securities  Exchange Act of 1934,
the  registrant  has duly  caused  this report to be signed on its behalf by the
undersigned, thereunto duly authorized.


                                 HYBRIDON, INC.

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

                                 Date:  May 8, 1998




HYBRIDON,  INC.  SUCCESSFULLY  EXCHANGES  $48.6  MILLION  OF DEBT FOR EQUITY AND
REACHES $27.3 MILLION IN 1998 PRIVATE PLACEMENT PROCEEDS

CAMBRIDGE,  Mass.,  May 6, 1998 -- Hybridon,  Inc.  (OTC-Bulletin  Board:  HYBN)
announced  today that it has closed a private  placement  of  approximately  6.6
million  shares of  Common  Stock  (sold at $2.00 per  share)  and  warrants  to
purchase common stock and  approximately  114,300 shares of Series A Convertible
Preferred  Stock (sold at $70 per share) and warrants to purchase  common stock.
Gross proceeds were  approximately  $21 million,  including  approximately  $6.7
million  which was applied to reduce  existing  payables  and satisfy  lease and
other obligations.  In addition,  Hybridon  announced that  approximately  $48.6
million principal amount of its 9% Notes have been tendered to the Company to be
exchanged  for shares of Series A  Convertible  Preferred  Stock and warrants to
purchase  common stock pursuant to the Company's  exchange  offer,  leaving only
approximately $1.4 million principal amount of 9% Notes  outstanding.  Moreover,
Hybridon  announced that all of the recent purchasers of its Units consisting of
14% Notes due 2007 and common stock  warrants have agreed to exchange such Units
for Common Stock  (priced at $2.00 per share) and  warrants,  bringing the total
proceeds of the offering to date to approximately $27.3 million.

Funding came from  investors in the United  States,  Europe and the Middle East,
and included the renewed participation of several large existing shareholders of
the Company, as well as significant holders of 9% Notes,  Hybridon creditors and
new  institutional  investors.  The private  placements  and exchange offer were
undertaken as part of Hybridon's new business plan contemplating a restructuring
of its capital  structure  to reduce debt  service  obligations,  a  significant
reduction in its burn rate and an infusion of additional equity capital.

The securities  offered in the private placements have not been registered under
the Securities Act of 1933, or applicable  state securities laws, and may not be
offered  or sold  absent  registration  under  the  Securities  Act of 1933  and
applicable state laws or available exemptions from registration.

The  statements  made in this  press  release  contain  certain  forward-looking
statements, including statements relating to the future financial performance of
the Company, within the meaning of Section 21E of the Securities Exchange Act of
1934, that involve a number of risks and uncertainties,  including the risk that
the Company will be unable to complete future  securities sales. Such statements
are only  predictions  and actual  events or results may differ  materially.  In
addition to the matters described in this press release,  risk factors as stated
from time to time in Hybridon's  SEC reports,  including but not limited to, its
Annual Report on Form 10-K, may affect the results achieved by Hybridon.

Hybridon, headquartered in Cambridge, Massachusetts, is engaged in the discovery
and  development  of novel  genetic  medicines for the treatment of diseases for
which there are currently limited or no effective treatments, based primarily on
antisense  technology.  The Company  also has a custom  manufacturing  division,
Hybridon Specialty Products.  Antisense technology involves the use of synthetic
segments  of DNA to stop  the  production  of  disease  associated  proteins  by
interacting at the genetic level with target strands of messenger RNA.

SOURCE Hybridon, Inc.