Washington Editor

The FDA gave Antigenics Inc. the go-ahead to resume enrollment of two Phase III trials for the personalized cancer vaccine Oncophage, following a 13-week partial clinical hold.

Wall Street responded favorably, giving the New York-based company's stock (NASDAQ:AGEN) an extra $2.02 Monday, or 21 percent, to close at $11.64.

Garo Armen, company chairman and CEO, told BioWorld Today enrollment will begin immediately. Under the temporary hold, the FDA allowed enrolled patients to continue receiving doses. The trials impacted were a fully enrolled 650-patient renal cancer study and a partially enrolled 350-patient metastatic melanoma cancer study.

FDA officials issued the hold in early September, so the agency could review Oncophage's characterization data. Armen described "characterization" as a broad category that includes information about a product's classification, potency, description and purity. He said the questions had nothing to do with Oncophage's safety.

"I think our ability to be able to deliver [the data] in such a quick period of time speaks to the fact that what we said then was exactly what the landscape was, meaning that we were confident we had most of the information needed," he said. "We had to do a few more things, but we felt confident that we would be able to work with the agency to get the hold resolved, and I believe the speed was unprecedented."

Indeed, the hold lasted about 13 weeks. When it was announced, Armen held a conference call but declined to release an estimated development timeline beyond the six to eight weeks needed to respond to FDA questions. (See BioWorld Today, Sept. 4, 2003.)

Mark Monane, principal, equity research, with Needham & Co. in New York, released a research note calling the decision to resume enrollment an "important step forward for Antigenics, as it not only facilitates the progress of two Phase III trials, but also decreases the regulatory risk for the company's vaccine approach going forward."

Oncophage (HSPPC-96), Antigenics' flagship product, is based on proprietary heat-shock protein technology. Derived from an individual's tumor, Oncophage contains the "antigenic fingerprint" of the patient's particular cancer and is designed to reprogram the body's immune system to target and destroy only cancer cells bearing that fingerprint. Oncophage is intended to leave healthy tissue unaffected and limit the side effects associated with traditional cancer treatments such as chemotherapy and radiation therapy, the company said.

While the renal study is fully enrolled, Armen said the company might add another 40 or so patients to the trial. About half the patients needed for the melanoma study are enrolled. Both trials should be complete by the end of 2004.

Oncophage is in earlier studies in several cancers, including breast, pancreatic, colon, lung and lymphoma. Armen said those Phase I and II studies were not impacted by the partial hold.

Oncophage was discovered by Antigenics and likely will be commercialized in the U.S. without a partner. The company might seek a partner overseas.