The original investors in MedImmune Inc., beneficiaries of amore than 400 percent increase in the company's stock pricesince May, will sell 2 million of their shares as part of a 2.5million-share offering of common stock filed by the company.

In its announcement late Thursday, the Gaithersburg, Md.,developer of therapeutics and vaccines said it will offer theremaining 500,000 shares.

MedImmune shares (NASDAQ:MEDI) closed Thursday at $50.50,up 75 cents. In May, the company raised $23.1 million in aninitial public offering of 2.5 million shares priced at $9.25.

Wayne T. Hockmeyer, president and chief executive officer,said the offering will allow the company to raise cash andenable the original investors "to reduce a portion of theirholdings through an orderly public sale."

If the offering is completed, the percentage of common stockoutstanding held by the company's early investors andmanagement would be reduced from 82 percent to 67 percent.As of Sept. 30, MedImmune had 16.4 million shares of commonstock outstanding on a fully diluted basis.

MedImmune has Food and Drug Administration marketingapproval for its CMVIg therapeutic for cytomegalovirusinfections.

Morgan Stanley & Co. Inc. and Smith Barney, Harris Upham &Co. will co-manage the underwriting group.

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