By Jim Shrine

Aronex Pharmaceuticals Inc. is expanding its Phase II study of Atragen in relapsed or refractory non-Hodgkin's lymphoma patients, after seeing responses in early stages of the trial.

The company is not disclosing details on the responses, nor details from the one-year trial or its expansion. But it said the data are strong enough to warrant further study.

"We're very encouraged by the results to date, and feel they are important from the perspective of actually seeing responses in relapsed patients in something like B-cell lymphoma," said Geoffrey Cox, chairman and CEO of Aronex. "This is unexpected both from the point of view of previous clinical results [from other agents], and that it has not been seen with other retinoids."

Atragen, a vitamin-A derivative, is an injectable liposomal formulation of all-trans retinoic acid. The Woodlands, Texas-based company filed a new drug application in December seeking approval of Atragen for treating acute promyelocytic leukemia (APL) in patients requiring intravenous administration. (See BioWorld Today, Dec. 8, 1999, p. 1.)

The APL submission was based on Phase II data, and Aronex has an ongoing study of the drug in patients with hormone-refractory prostate cancer. Cox said a regulatory strategy in non-Hodgkin's lymphoma has not been developed.

"It's a study in progress," he said. "The purpose was an investigatory Phase II study. The first requirement was to show clinical efficacy. We have seen sufficient clinical efficacy from the early stages of this Phase II study to encourage us to expand it to a greater number of patients."

The study was started at M.D. Anderson Cancer Center, in Houston, in June 1998. It is being administered intravenously three times a week in patients with B-cell, T-cell or T-cell cutaneous lymphomas. Cox said details would be released in an appropriate scientific forum. Specifics from the APL trials have not been disclosed yet, either.

The non-Hodgkin's lymphoma indication was developed following work at M.D. Anderson by Richard Ford, who showed in vitro that Atragen was substantially more potent than other retinoids in inhibiting growth of B-cell non-Hodgkin's lymphoma. Atragen also induced apoptosis.

"That was the data which encouraged us," Cox said. "We're looking to see if we could get some of the in vitro studies to translate into clinical efficacy. We believe that by putting [all-trans retinoic acid] into a liposome we significantly change the pharmacology, giving us a real opportunity to show a clinical benefit."

Aronex cited American Cancer Society figures estimating that 55,000 cases of non-Hodgkin's lymphoma are diagnosed each year. That is a much larger potential market than the lead, APL indication.

"This significantly expands the opportunity for this particular drug as we go forward," Cox said. "This is a very much more substantial indication, which is important for commercialization."

Atragen also is being studied in Phase I/II trials in bladder and prostate cancers, and a Phase I study in combination with alpha interferon in renal cell carcinoma.

Aronex's stock (NADAQ:ARNX) gained 12 cents per share Monday to close at $4.187.