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                                                                    EXHIBIT 99.1

[HYBRIDON LOGO]          NEWS RELEASE





                           Hybridon, Inc.         Tel: 617.528.7000 Fax: 617.528.7001 
                           620 Memorial Drive     www.hybridon.com                     
                                            
FOR IMMEDIATE RELEASE      Cambridge, MA 02139    
                                        
                                                  Contact: Douglas J. Jensen
                                                  Vice President, Administration and
                                                  Corporate Development
                                                  617.528.7523


                                                  Noonan Russo Communications, Inc.          
                                                  212.695.4455                               
                                                  Stephanie Seiler, PhD. (Investor) ext. 212
                                                  Renee Solano (media) ext.227               
                                                  





           HYBRIDON TO CONTINUE TRADING PENDING NASDAQ APPEAL PROCESS

Cambridge, Mass. - September 23, 1997 - Hybridon, Inc. (Nasdaq: HYBN) today
announced that the Company is moving forward with the appeal process with The
Nasdaq Stock Market Inc. ("NASDAQ"), in response to a notification of delisting
which the Company announced last week. Hybridon received a letter from NASDAQ
indicating that the Company was no longer in compliance with listing
requirements and would be delisted. Hybridon has filed an appeal with NASDAQ,
and the Company's stock will continue to trade on the Nasdaq National Market
until the appeal is resolved.

"We are examining our options for addressing NASDAQ's concerns and moving
forward with our appeal process," said E. Andrews Grinstead, Chief Executive
Officer of Hybridon. "There are a number of possible approaches to resolving our
non-compliance issues, in addition to complying with alternative listing
requirements on the NASDAQ National Market which we are exploring. Hybridon
stock will continue to trade during the appeal process."

Hybridon, headquartered in Cambridge, Massachusetts, is a leader in the
discovery and development of novel genetic medicines for the treatment of
important diseases, based primarily on antisense technology. Antisense
technology involves the use of synthetic segments of DNA and RNA to stop the
production of disease-associated proteins by interacting at the genetic level
with target strands of messenger RNA.

                                     # # #

                    Leadership in Genetic Antisense Medicine