Cubist Issues Common Stock to Lilly

March 23, 2005

Cubist Pharmaceuticals announced that it has completed the issuance of $20 million worth of Cubist common stock to Eli Lilly and Company in connection with the previously announced royalty buy down transaction. The price of the shares, $10.66 per share, is based on the average closing price of the stock over ten consecutive trading days ended March 2, 2005. The number of shares issued was 1,876,173. Cubist's global royalty obligation to Lilly on CUBICIN sales will be reduced by two percentage points, once the issued shares are registered by Cubist or sold by Lilly, whichever comes first.

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