Washington Editor

Citing insufficient product characterization data, the FDA placed a partial clinical hold on two Phase III trials of Oncophage, Antigenics Inc.'s personalized cancer vaccine.

The move likely will delay development of Oncophage in metastatic melanoma by three to six months, Mark Monane, principal, equity research, with Needham & Co. in New York, told BioWorld Today.

But analysts believe product development in renal cancer will not be terribly impacted by FDA demands. The partial hold allows Antigenics to continue treating enrolled patients or patients who have signed the consent form.

The renal trial is fully enrolled at 650 patients while the melanoma trial is halfway enrolled at 325.

In a conference call with analysts, reporters and investors, Garo Armen, Antigenics' CEO, refused to release a development timeline beyond the six- to eight-week period needed to respond to the FDA's request.

Armen said the FDA seeks additional information on product potency, purity and identity. The agency has not asked for additional clinical trials, nor has it suggested that safety is at issue.

"The simple way of putting it: The FDA wants to make sure our product is what we say it is," Armen said.

The company has the information sought by the FDA, but needs a little time to pull it together and submit it, he said.

Monane characterized the partial hold as a normal step in the development process.

"Biotechnology is not certain to begin with, now you have the FDA adding more uncertainty, so the stock is hurt in the near term," Monane said. "But, if you sit down and actually go beyond the news headlines, we think Antigenics is still on track for its lead product in kidney cancer, but they may have to do a little more homework before they file."

Antigenics' stock (NASDAQ:AGEN) closed Wednesday at $13.03, down $1.02.

Needham & Co. expects interim data on the kidney trial in December, and final data in the first half of 2004.

Derived from each individual's tumor, Oncophage (HSPPC-96) 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 debilitating side effects associated with traditional cancer treatments such as chemotherapy and radiation therapy, the company said.

The partial hold is specific to the renal and metastatic melanoma trials, having no impact on other Oncophage trials or other products in development at Antigenics, Armen told conference call listeners.

Other clinical research evaluating Oncophage includes studies in cancers such as lymphoma, and pancreatic and gastric cancers. The company in late August released data on a 29-patient Phase II trial of Oncophage in metastatic colorectal cancer.

Patients who responded immunologically to the vaccine (52 percent of participants) had a statistically significant survival advantage compared with patients who did not respond immunologically. Responders had a two-year overall survival rate of 100 percent, compared with 50 percent for nonresponders, and a disease-free survival rate of 51 percent compared with 8 percent among nonresponders, the company said.