By Frances Bishopp

Aronex Pharmaceuticals Inc. and Genzyme Corp. have amended their 1993 agreement relating to the development of Atragen, a liposomal form of all-trans retinoic acid, targeted for acute promyelocytic leukemia (APL) and Kaposi's sarcoma.

Under the revised agreement, Genzyme's rights will be converted to an option to commercialize Atragen. If Genzyme exercises its option, Aronex will receive additional cash payments of $3 million.

Genzyme already has paid $2 million to Aronex, of The Woodlands, Texas, as part of the 1993 agreement between the firms relating to the joint development of Atragen.

Aronex will receive royalties on sales and equal co-promotion rights in the U.S.

If Genzyme, of Cambridge, Mass., does not exercise its option, Aronex will reacquire worldwide rights by paying Genzyme $2 million in cash and capped royalty payments on product sales.

The companies expect to file a new drug application with the FDA for the leukemia indication by the end of 1997, supplementing it later with additional data on Kaposi's sarcoma and other indications to broaden the label.

Preliminary safety data from an ongoing Phase II trial in APL indicate Atragen was well tolerated and reflected results obtained in the Phase I maximum tolerated dose trial. One hundred percent of first-relapse patients (10 out of 10) achieved complete remission with Atragen monotherapy.

The companies also announced preliminary data from a Phase I/II trial of Atragen in AIDS patients with Kaposi's sarcoma that indicate the drug was generally well tolerated, with headache and dry skin being the primary reported adverse advents.

In this study, two dose regimens of Atragen were evaluated: once-a-week vs. three-times-a-week. In addition, dose levels ranging from 60 mg/m2 to 120 mg/m2 were evaluated.

A total of 82 patients were treated. A subset of 13 Kaposi's sarcoma patients treated at a dose of 120 mg/m2 three times a week were evaluated using the AIDS Clinical Trials Group response criteria. In this group, 8 percent achieved a clinical complete response, 46 percent had a partial response or stable disease and 46 percent showed progressive disease. *