Exhibit 99.1



               LETTER TO COMMISSION PURSUANT TO TEMPORARY NOTE 3T




HYBRIDON, INC.
345 Vassar Street
Cambridge, MA 02139
April 01, 2002


Securities and Exchange Commission
450 Fifth Street, N.W.
Washington, D.C.  20549-0408

Ladies and Gentlemen:

Pursuant to Temporary Note 3T to Article 3 of Regulation S-X, Hybridon, Inc. has
obtained a letter of representation from Arthur Andersen LLP ("Andersen")
stating that the December 31, 2001 audit was subject to their quality control
system for the U.S. accounting and auditing practice to provide reasonable
assurance that the engagement was conducted in compliance with professional
standards, that there was appropriate continuity of Andersen personnel working
on the audit and availability of national office consultation. Availability of
personnel at foreign affiliates of Andersen is not relevant to this audit.

Very truly yours,

Hybridon, Inc.

/s/ Robert G. Andersen

Robert G. Andersen
Chief Financial Officer