1



                                                                    EXHIBIT 99.1

                          ARONEX PHARMACEUTICALS, INC.
                              FOR IMMEDIATE RELEASE

                          ARONEX PHARMACEUTICALS, INC.
                            ANNOUNCES RIGHTS PROGRAM

         THE WOODLANDS, TEXAS, OCTOBER 7, 1999 --- Aronex Pharmaceuticals, Inc.
("Aronex" or the "Company") (Nasdaq National Market: ARNX), a biopharmaceutical
company focused on proprietary medicines to treat cancer and infectious
diseases, today announced that its Board of Directors has adopted a Rights Plan
designed to protect the Company's stockholders from coercive or unfair takeover
techniques.

         Terms of the Rights Plan provide for a dividend distribution of one
Preferred Stock Purchase Right for each outstanding share of Common Stock to
holders of record at the close of business on October 18, 1999. The Rights Plan
would be triggered if an acquiring party accumulates or initiates a tender offer
to purchase 20% or more of the Company's Common Stock and would entitle holders
of the Rights to purchase either the Company's stock or shares in an acquiring
entity at half of market value. The Company would generally be entitled to
redeem the Rights at $0.001 per Right at any time until the tenth day following
the time the Rights become exercisable. The Rights will expire on October 18,
2009.

         The Rights are not being distributed in response to any specific effort
to acquire the Company. The Rights are designed to assure that all stockholders
of the Company receive fair and equal treatment in the event of any proposed
takeover of the Company and to guard against partial tender offers, open market
accumulations and other tactics designed to gain control of the Company, without
paying all stockholders a fair price. The Rights are not presently exercisable
and are not represented by separate certificates. No action is required to be
taken by the Company's stockholders at the present time.

         Commenting on the Rights Plan, Geoffrey F. Cox, Ph.D. the Company's
Chairman of the Board and Chief Executive Officer, said: "The Board of Directors
believes that the Rights Plan represents a sound and reasonable means of
safeguarding the interests of the Company's stockholders. The Board of Directors
is not aware of any current effort to acquire control of the Company." Dr. Cox
said the Rights Plan is similar to those adopted by over 3,000 other companies,
and that details of the new Rights Plan will be outlined in the Company's Form
8-K filing with the SEC and in a letter to be mailed to stockholders of record
on or about October 18, 1999.

         Aronex Pharmaceuticals, Inc. is a biopharmaceutical company that
develops and commercializes proprietary innovative medicines to treat cancer and
infectious diseases. Aronex Pharmaceuticals currently has five products in
clinical development, two of which (ATRAGEN(R) and NYOTRAN(R)) are in an
advanced stage, as well as a pipeline of additional products.