By Lisa Seachrist

Washington Editor

Aronex Pharmaceuticals Inc.'s Atragen, a liposomal formulations of all-trans retinoic acid (ATRA), proved positive in a pivotal Phase II study testing the drug as a treatment for patients with acute promyelocytic leukemia (APL) who can't take the oral formulation.

The company presented the results of the study at the American Society of Clinical Oncology meeting in New Orleans on Sunday. The study showed treatment with Atragen produced complete remissions in 87 percent of newly diagnosed patients. The data will be used to bolster Atragen's pending new drug application (NDA).

"We're very pleased Atragen shows strong activity and safety," said Geoffrey Cox, chairman and CEO for The Woodlands, Texas-based Aronex. "We are currently in the process of amending the NDA and expect to file that amendment in the next few weeks."

ATRA is a derivative of vitamin A that battles cancer by inducing tumor cells to differentiate into mature cells that do no proliferate abnormally. Unfortunately, as an oral preparation, the drug can't readily be employed in patients who can't ingest pills, such as those who are intubated or have significant gastrointestinal problems.

Cox pointed out a large number of patients with APL develop brain bleeds as one of the first symptoms of disease activity. As a result, an oral therapy won't work. Atragen could be a viable alternative because is an infused liposomal formulation. It also provides a more stable concentration of the drug in the bloodstream.

The study presented at ASCO included 75 patients who had either been newly diagnosed, or had relapsed. Among those who'd relapsed were patients whose cancer was resistant to ATRA therapy. Patients were treated with 90 milligrams of Atragen per meter squared every other day until complete remission was achieved. Eighty-seven percent of the newly diagnosed patients had complete remissions, 78 percent of the relapsed patients had complete remission, and 23 percent of the patients who were resistant to ATRA had complete remissions with Atragen.

"We are very clearly happy with the strength of this data," Cox said. "That is serving as the basis for moving into other indications."

In addition to investigating the efficacy of Atragen in APL, the company is conducting Phase II clinical trials to evaluate the potential of the product as a treatment for non-Hodgkin's lymphoma, hormone-resistant prostate cancer and acute myelogenous leukemia. Aronex also has a Phase I/II trial of the drug in combination with interferon-alpha as a treatment for renal cell carcinoma.

In December 1998, Aronex submitted an NDA for Atragen. In September 1999, FDA issued a non-approvable letter to the company, raising several issues. Cox said the amendment that the company will file soon should address those concerns. "At least, we believe they do," he said.

Aronex's stock (NASDAQ:ARNX) closed Monday at $2.843, up 7.82 cents.