Pfizer Inc. (NYSE: PFE) today announced that, based on preliminary results, its previously announced offer to its shareholders to exchange all, some or none of their shares of Pfizer common stock for shares of Zoetis Inc. (NYSE: ZTS) common stock owned by Pfizer was oversubscribed. The exchange offer expired at 12:00 midnight, New York City time, on June 21, 2013. Under the terms of the exchange offer, 0.9898 shares of Zoetis common stock will be exchanged for each share of Pfizer common stock accepted in the exchange offer. According to the exchange agent, Computershare Trust Company, N.A., 1,680,439,287 shares of Pfizer common stock were validly tendered and not validly withdrawn, including 497,530,121 shares that were tendered by notice of guaranteed delivery. Pfizer has accepted 405,117,195 of the tendered shares in exchange for the 400,985,000 shares of Zoetis common stock owned by Pfizer. Because the exchange offer was oversubscribed, Pfizer accepted only a portion of the shares of its common stock that were validly tendered and not validly withdrawn, on a pro rata basis in proportion to the number of shares tendered. Shareholders who owned fewer than 100 shares of Pfizer common stock, or an “odd-lot”, who have validly tendered all of their shares and made the appropriate election, will not be subject to proration, in accordance with the terms of the exchange offer. Based on the total number of shares of Pfizer common stock reported to be tendered prior to the expiration of the exchange offer, it is estimated that approximately 24% of the tendered shares of Pfizer common stock will be exchanged, assuming all shares tendered by guaranteed delivery procedures are delivered under the terms of the exchange offer. This preliminary proration factor is subject to change based on the number of tendered shares that satisfy the guaranteed delivery procedures, as well as the number of “odd-lot” shares that were validly tendered and not subject to proration. Pfizer expects to announce the final proration factor promptly following the expiration of the guaranteed delivery period, which is expected to occur on June 26, 2013. Shares of Pfizer common stock tendered but not accepted for exchange will be returned to the tendering shareholders in book-entry form promptly after the final proration factor is announced.