MedImmune

(MEDI)

said Thursday that it must supply U.S. drug regulators with more data on its experimental flu vaccine, FluMist. The biotech firm said nothing about the chances of the inhaled vaccine's readiness for this winter's flu season.

But MedImmune's fuzzy comments on FluMist -- following the receipt of a Complete Response Letter from the Food and Drug Administration -- did not seem to bother investors, at least so far. Shares of MedImmune were trading around $23 in premarket activity after closing Wednesday at $21.65.

While few biotech observers expected the FDA to approve FluMist outright Thursday, there was considerable hope that outstanding issues would be minimal, allowing MedImmune to declare with confidence that the vaccine could be approved and on pharmacy shelves by this fall, in time for the 2002-2003 flu season.

But in its press release, MedImmune was either unable or unwilling to go that far. The company didn't disclose specific contents of the FDA complete response letter, nor did it stray from previous guidance: FluMist has a 50% shot at getting approval in time for the upcoming flu season. The company did say that no new clinical trials for FluMist were necessary.

"As expected, we received a Complete Response Letter from the FDA requesting additional information relating to our FluMist application," said David Mott, MedImmune's CEO, in a statement. "We intend to respond promptly to the FDA's request and look forward to continuing to work with the agency toward the potential approval of FluMist."

MedImmune gained control of FluMist as part of last year's $1.5 billion acquisition of

Aviron

.

MedImmune is holding a conference call to discuss the FDA decision after the close of trading Thursday. The company is expected to earn 63 cents per share this year, which includes profits from 2002 FluMist sales and royalty payments from partner Wyeth. If FluMist's launch is delayed, of course, revenue and profit estimates will have to come down.

Lazard Freres biotech analyst Joel Sendek has taken a very cautious stance on FluMist, excluding the drug from his 2002 earnings estimate of 45 cents per share. If FluMist does get approved this year, his earnings estimates would increase by 12 cents. Sendek rates MedImmune a hold and his firm doesn't have a banking relationship with the company.

On the other end of the spectrum, UBS Warburg biotech analyst Meirav Chovav has factored in $120 million in 2002 FluMist sales to her financial model, arriving at a 2002 earnings estimate of 70 cents per share. Chovav rates MedImmune a strong buy and her firm doesn't have a banking relationship with the company.

Salomon Smith Barney analyst Elise Wang said Thursday she'd be erasing 25 cents per share and 10 cents to 12 cents per share from her 2002 and 2003 earnings estimates, respectively, if FluMist was delayed. She rates the company outperform and her firm doesn't do banking for the company.

MedImmune shares have lost more than 50% of their value this year, in line with the slumping biotech sector. But selling has accelerated recently because biotech investors -- burned to a crisp already by the slumping sector -- have been in no mood to shoulder any additional risk.

In July 2001, an FDA advisory panel found FluMist to be effective as a new, easy-to-use flu-prevention treatment, but nonetheless gave the vaccine a thumbs down because of some safety concerns, including the risk of pneumonia. A month later, the FDA asked MedImmune to provide additional safety data. The company responded in January, which led to Thursday's decision.