MedImmune Inc. received from the FDA a complete response letter concerning the biologics license application for the influenza product FluMist that again asked for more information but did not stipulate new trials must be conducted.

While the request for new information could potentially mean a delay in the launch of FluMist, Gaithersburg, Md.-based MedImmune's stock (NASDAQ:MEDI) rose $3.36 Thursday, or 15.9 percent, to close at $24.46.

"There were 68 questions in the letter," David Mott, MedImmune's CEO, said in a conference call after the market closed Thursday. "Twenty-four are related to the manufacturing of the product. Forty-four are related to clinical information.

"To us, the majority of them seem to be relatively minor," he added.

MedImmune took over the regulatory path of FluMist in January following its merger, estimated at $1.5 billion at the time, with Aviron Inc. Aviron originally filed its BLA for FluMist in October 2000. An FDA advisory panel voted not to recommend approval for FluMist in July 2001, asking for more safety data on the product, and an FDA complete response letter followed the panel's recommendation. MedImmune submitted answers to the FDA's questions in January, but the FDA was not yet satisfied. (See BioWorld Today, July 30, 2001, and Dec. 4, 2001.)

This time around, the FDA again is interested in safety.

"On the clinical side [of the letter], the areas that we think are the most significant have been previously discussed in the advisory committee [panel in July 2001]," Mott said. "Specifically, an elevated rate of asthma and wheezing episodes in certain subgroups of young children [aged 18 months to 35 months]."

In the conference call, Mott acknowledged the company had the letter for about 24 hours, and he had spent that time "holed up" with his technical staff. That done, he said MedImmune feels "pretty good about the questions we have received," and is "working feverishly [to provide a] complete and thorough response in the next 30 to 45 days."

Whether MedImmune's response will appease the FDA remains to be seen.

"Your guess is as good as mine," said Yaron Werber, vice president, biotechnology, equity research at SG Cowen Securities Corp. He added that the FDA could give a Class I response to MedImmune's reply, meaning a two-month review, or a Class II response, allowing for six months of review time.

FluMist is designed to prevent influenza in both children and adults. The product is a live, attenuated vaccine delivered nasally as a mist that would provide a needle-free method of flu vaccination. If approved, the product would do its heavy sales in the fourth and first quarters, so missing the 2002-03 flu season would mean a year of lost revenue.

Whether FluMist can be launched in time for that season is still up in the air, although MedImmune likes its chances.

Werber's firm models FluMist's price at $30 per administration. Based on that, and a full season in 2002-03, he sees the product generating $112 million worldwide for the upcoming flu season. That figure increases attractively over time: $341 million for the 2003-04 season, $573 million for the following season, and $881 million for the season after that. FluMist is partnered worldwide with Wyeth, of Madison, N.J., meaning MedImmune would receive $57 million in the 2002-03 season and $174 million, $292 million and $403 million in the following seasons, by SG Cowen's model.

MedImmune is scheduled to release its second-quarter earnings on July 25. Although Werber said he estimates MedImmune seeing $61 million in revenues for the second quarter, the figures for that time of year don't carry a lot of weight, as MedImmune's product, Synagis, marketed for the prevention of serious lower respiratory tract disease caused by respiratory syncytial virus (RSV) in pediatric patients at high risk of RSV disease, sells lightly in the spring and summer months.

"[The second] quarter is not an important quarter for them," he told BioWorld Today. "No one is going to care what its earnings are, really."

For now, MedImmune will do its part, digest the letter and address its concerns. When that is done, the matter is once again in the FDA's hands.

"We view this as a significant step forward," Mott said, adding that although the "timelines for potential launch this year are tight" the company "still expects a launch in either the 2002 or 2003 flu season."