By Matthew Willett

Aviron Inc. amended its shelf registration in a move to publicly offer 3 million shares of common stock and $150 million aggregate principal convertible subordinated notes.

Aviron's stock (NASDAQ:AVIR) opened Friday at $53.75. At that assumed price, the offering would gross the company $161.25 million in addition to the $150 million in convertible notes. The shares closed at $52.875, down 87.5 cents.

Underwriters for the offering, managed by Morgan Stanley Dean Witter, J.P. Morgan Chase and SG Cowen Securities Corp., all of New York, were granted an option to purchase an additional 450,000 shares - 250,000 from the company and 200,000 from selling shareholders - and an additional $22.5 million in convertible notes to cover overallotments.

If the underwriters exercise their option, the offering would total about $347.18 million. Mountain View, Calif.-based Aviron officials declined comment, citing Securities and Exchange Commission-imposed quiet period restrictions.

The shares and notes are being sold pursuant to a $400 million shelf registration filed in December and amended last week. (See BioWorld Today, Dec. 19, 2000.)

Funding from the offering could be applied to the launch of FluMist, the company's influenza vaccine. Aviron filed a biologics license application for FluMist in October, and the FDA accepted it for filing in December.

If approved, Aviron would market FluMist with Wyeth Lederle Vaccines, a business unit of the pharmaceutical division of American Home Products Corp. The company plans to launch FluMist for the 2001-02 flu season.

In addition to FluMist, Aviron is developing a parinfluenza virus type III vaccine to prevent the most common cause of croup. It completed a Phase II trial in 1998.

An Epstein-Barr virus vaccine to prevent infectious mononucleosis partnered with GlaxoSmithKline plc, of Brentford, UK, completed enrollment in a Phase II trial in November, and a Phase I trial for the company's vaccine for cytomegalovirus is under way.

In preclinical study, Aviron is developing vaccine candidates for herpes simplex virus type-2 and respiratory syncytial virus.

As of Sept. 30, 2000, the company had about $121 million in cash and cash equivalents. As of the same date it had about 22.22 million shares outstanding.