Officials at Immune Response Corp. said they will rely primarily on data from a small human trial as it is getting ready to file for regulatory approval in Europe and the United States for its experimental vaccine drug Remune.
Two analysts, however, raised concerns whether Immune Response will be able to convince regulators of the merits of its drug based on the result of a Phase II trial. The FDA typically requires positive data from Phase III trials to approve a drug.
"I think it's going to be very difficult to get Remune approved," said Sushant Kumar, an analyst with Mehta Partners in New York City.
"This is a very tricky area," added John McCamant, editor of the Medical Technology Stock Letter published in Berkeley. "It's hard to get drugs approved with a Phase II trial. Most HIV drugs have to have other data (to get approved)."
Immune Response said Aug. 30 it will not pursue a large study of Remune, because the drug wasn't likely to meet its end-point , that is to stimulate patients' immune system.
The decision was based on data from Pfizer Inc., the major drug maker that agreed to develop Remune but in July withdrew its support.Results Analyzed
Now all hopes are pinned on Immune Response's own analysis of a subset of 243 patients from Spain who participated in a larger study comprising 2,527 patients.
Dr. Ronald Moss, Immune Response's vice president of medical and scientific affairs, said the Spanish trial clearly demonstrated that Remune can reduce the amount of HIV in the bloodstream.
That is contrary to the primary findings of the larger trial which was halted in 1999 after an independent group of experts concluded Remune didn't help patients live longer.
Generally, the FDA requires at least three successfully completed Phase III trials before considering approval of a drug.
Remune has failed to show "statistical significance" in two Phase III trials.
Dennis Carlo, president and CEO of Immune Response, however, said given the complexity of HIV, it is unlikely that the FDA will require data from a large last-stage trial.
"Phase III trials are very hard to do (in HIV patients)," Carlo said. " (the FDA) will look more at the quality of the data and (treatment) options for the disease."
McCamant contended the FDA has become more stringent in their drug approval process and is likely to demand more data from companies.
"There has been a significant slowdown and extra concern for safety," McCamant said.Additional Trials Possible
Carlo said Immune Response is already preparing for the event that the FDA will require additional trials.
He said Immune Response does not intend to raise more money from investors, but, if needed, wants to rely on a partner for funding instead.
"We have a number of companies that are interested in partnering with us," Carlo said without offering any details.
But Kumar said given the firm's history, it will be hard to find a collaborator.
Immune Response has lost 54 percent of its value since July 6, when Pfizer announced it would no longer develop Remune.
McCamant said Pfizer's withdrawal doesn't necessarily mean Remune isn't working.
A new partner , provided Immune Response can find one , would add more credibility to the firm, McCamant said.
Immune Response no longer has strong backing by investors, McCamant said.
The stock has hovered around $2 for weeks.
News of the positive analysis of the Spanish trial sent Immune Response's stock up 58 percent to close at $2.58 on April 23, but the excitement was short-lived.Suits Filed
Independent researchers at the UC San Francisco claimed Immune Response tried to block it from publishing negative data on the larger Remune trial and tried to force it to include the firm's own subset analysis.
Carlo said the firm has since reached a agreement with UCSF and the scientist involved.
"We felt that based on the Spanish data there was no point in going ahead with the arbitration," Carlo said.
That contradicts what UCSF spokeswoman Jennifer O'Brien said.
"Nothing has been finalized. We've reached an agreement under which the company has provided us with the final data set from the study, as we requested. Once it has been verified that it is complete, both sides will dismiss their arbitration," O'Brien said.
Meanwhile, investors unhappy with the firm's lagging stock performance have filed suit against Immune Response.
Carlo had no comment on the lawsuit.
As of July, Immune Response had $13 million in cash, which will last through year's end, Carlo said.
He also projected it would cost $5 million to run another Phase II trial, provided the FDA wanted to see more data. He and Moss said it would be nearly impossible to run a Phase III trial given the complexity of HIV.