Definitive Additional Materials





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Proxy Statement Pursuant to Section 14(a) of

the Securities Exchange Act of 1934



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Important CALITHERA Notice of Availability of BIOSCIENCES, Proxy Materials for the Stockholder INC Meeting . of To Be Held On: May 31, 2018 at 10:00 am Pacific Time Hilton Garden Inn San Francisco Airport North 670 Gateway Blvd, South San Francisco, CA 94080 COMPANY NUMBER JOHN SMITH 1234 MAIN STREET ACCOUNT NUMBER APT. 203 NEW YORK, NY 10038 CONTROL NUMBER This communication presents only an overview of the more complete proxy materials that are available to you on the Internet. We encourage you to access and review all of the important information contained in the proxy materials before voting. If you want to receive a paper or e-mail copy of the proxy materials you must request one. There is no charge to you for requesting a copy. To facilitate timely delivery please make the request as instructed below before 5/21/18. Please visit, where the following materials are available for view: ● Notice of Annual Meeting of Stockholders ● Proxy Statement ● Form of Electronic Proxy Card ● Annual Report on Form 10-K TO REQUEST MATERIAL: TELEPHONE: 888-Proxy-NA (888-776-9962) 718-921-8562 (for international callers) E-MAIL: WEBSITE: TO VOTE: ONLINE: To access your online proxy card, please visit and follow the on-screen instructions or scan the QR code with your smartphone. You may enter your voting instructions at up until 11:59 PM Eastern Time the day before the cut-off or meeting date. IN PERSON: You may vote your shares in person by attending the Annual Meeting. MAIL: You may request a card by following the instructions above. 1. To elect the Board’s two nominees for director to serve until the 2021 annual 2. To ratify the selection by the Audit Committee of the Board of Directors of Ernst & Young meeting of stockholders and until their successor is duly elected and LLP as the independent registered public accounting firm of the Company for its fiscal qualified. year ending December 31, 2018. NOMINEES: Sunil Agarwal, M.D. Jean M. Note: To conduct any other business properly brought before the meeting. George These items of business are more fully described in the Proxy Statement accompanying this Notice. The record date for the Annual Meeting is April 4, 2018. Only stockholders of record at the close of business on that date may vote at the meeting or any adjournment thereof. THE BOARD OF DIRECTORS RECOMMENDS A VOTE “FOR” THE ELECTION OF DIRECTOR AND “FOR” PROPOSAL 2. Please note that you cannot use this notice to vote by mail.