European regulators can now approve drugs on a conditional basis, meaning companies can market their products while simultaneously conducting additional follow-up of patients or further clinical studies.
If at the end of the trial period the regulatory agency were not satisfied, it could pull the drug from the market.
"Filing in Europe won't be a slam dunk, and will probably be more difficult than in Russia," said Armen, who added that the European review process would likely take 12 to 18 months.
The Russian approval caps years of dogged determination to bring the vaccine to the market despite multiple setbacks and investor skepticism of cancer vaccines in general.
Oncophage is designed to reprogram a patient's immune system to target cancer cells from a specific tumor.
The company takes tissue from a tumor following surgery, extracts proteins it says activate the immune system and then injects the enriched proteins back into the body through the skin.
Unlike a vaccine such as Merck & Co's Gardasil, which is designed to ward off a virus that is believed to cause some 70 percent of cervical cancer cases, Oncophage is designed to target the cancer directly and delay or prevent it from spreading once it has developed.
There are about 16,000 new cases of kidney cancer a year in Russia, according to Armen, of which about a quarter fit the profile of patients most likely to benefit from Oncophage - a market theoretically worth about $200 million to Antigenics.
The Russian pharmaceuticals market is one of the fastest growing in the world. It will grow by nearly 60 percent to $19.4 billion in 2009 from about $12.3 billion in 2006, the research group DSM estimates.
Armen said he expects the initial sales growth for Oncophage to be "modest."
"We would have to price this probably at the low- to mid-range of other new-generation cancer drugs," Armen said.
Such drugs can cost as much as $60,000 per patient per year, he said.
"How much of that market we achieve depends on how well we iron out reimbursement issues and how effectively we can reach every single patient," Armen said.
Shares of Antigenics were up 62 cents or 25 percent to $3.09 in late afternoon trading on Nasdaq after touching $3.90 earlier in the day, an increase of about 58 percent.
