Filed by Bristol-Myers Squibb Company

Pursuant to Rule 425 of the Securities Act of 1933

and deemed filed pursuant to Rule 14a-12

of the Securities Exchange Act of 1934

Form S-4 File No.: 333-229464

Subject Company: Celgene Corporation

SEC File No.: 001-34912

Explanatory Note: The following letter was distributed to employees of Bristol-Myers Squibb Company on February 22, 2019

February 22, 2019

Dear Colleagues,

We continue to make good progress on our proposed acquisition of Celgene. Today we reached an important milestone and filed our definitive joint proxy statement / prospectus with the U.S. Securities and Exchange Commission. With this action, we are now able to begin soliciting votes in favor of the transaction. The date of the special meeting to vote on the proposed acquisition is scheduled for April 12, 2019.

If you are a BMS stockholder, your vote is important no matter how many shares you own. As detailed in the proxy materials, the entire BMS Board of Directors unanimously believes this acquisition is in the best interests of the company’s stockholders and recommends that stockholders vote “FOR” the proposal to approve theissuance of shares of Bristol-Myers Squibb common stock in the merger with Celgene, as well as all other proposals included on the WHITE proxy card. Given the large number of shares held by individuals, including employees, every vote counts! If you are a BMS stockholder, you will soon be receiving information in the mail about how to vote. Be on the lookout for that information.

We are now an important step closer to completing the transaction, which we continue to expect will close in the third quarter of 2019. We are pleased with the support we have received from investors and regulators and are confident that we are on track to build the leading biopharma company.

Thank you again for your continued hard work and dedication to Bristol-Myers Squibb and for all you do for the patients we serve.

Sincerely,

Giovanni

Bristol-Myers Squibb stockholders who need assistance in completing the proxy card or voting instruction form or have questions regarding the Bristol-Myers Squibb special meeting may contact BMS’ proxy solicitors:

MacKenzie Partners, Inc.

Phone: (800) 322-2885 or at (212) 929-5500

Email: proxy@mackenziepartners.com

Important Information For Investors And Stockholders

This communication does not constitute an offer to sell or the solicitation of an offer to buy any securities or a solicitation of any vote or approval. It does not constitute a prospectus or prospectus equivalent document. No offering of securities shall be made except by means of a prospectus meeting the requirements of Section 10 of the U.S. Securities Act of 1933, as amended.

In connection with the proposed transaction between Bristol-Myers Squibb Company (“Bristol-Myers Squibb”) and Celgene Corporation (“Celgene”), on February 1, 2019, Bristol-Myers Squibb filed with the Securities and Exchange Commission (the “SEC”) a registration statement on Form S-4, as amended on February 1, 2019 and February 20, 2019, containing a joint proxy statement of Bristol-Myers Squibb and Celgene that also constitutes a prospectus of Bristol-Myers Squibb. The registration statement was declared effective by the SEC on February 22, 2019, and Bristol-Myers Squibb and Celgene commenced mailing the definitive joint proxy statement/prospectus to the stockholders of Bristol-Myers Squibb and Celgene on or about February 22, 2019. INVESTORS AND SECURITY HOLDERS OF BRISTOL-MYERS SQUIBB AND CELGENE ARE URGED TO READ THE DEFINITIVE JOINT PROXY STATEMENT/PROSPECTUS AND OTHER DOCUMENTS FILED OR THAT WILL BE FILED WITH THE SEC CAREFULLY AND IN THEIR ENTIRETY BECAUSE THEY CONTAIN OR WILL CONTAIN IMPORTANT INFORMATION.  Investors and security holders will be able to obtain free copies of the registration statement and the definitive joint proxy statement/prospectus and other documents filed with the SEC by Bristol-Myers Squibb or Celgene through the website maintained by the SEC at http://www.sec.gov. Copies of the documents filed with the SEC by Bristol-Myers Squibb are available free of charge on Bristol-Myers Squibb’s internet website at http://www.bms.com under the tab, “Investors” and under the heading “Financial Reporting” and subheading “SEC Filings” or by contacting Bristol-Myers Squibb’s Investor Relations Department through https://www.bms.com/investors/investor-contacts.html.  Copies of the documents filed with the SEC by Celgene are available free of charge on Celgene’s internet website at http://www.celgene.com under the tab “Investors” and under the heading “Financial Information” and subheading “SEC Filings” or by contacting Celgene’s Investor Relations Department at ir@celgene.com.

Certain Information Regarding Participants

Bristol-Myers Squibb, Celgene, and their respective directors and executive officers may be considered participants in the solicitation of proxies in connection with the proposed transaction. Information about the directors and executive officers of Bristol-Myers Squibb is set forth in its Annual Report on Form 10-K for the year ended December 31, 2017, which was filed with the SEC on February 13, 2018, its proxy statement for its 2018 annual meeting of stockholders, which was filed with the SEC on March 22, 2018, and its Current Report on Form 8-K, which was filed with the SEC on August 28, 2018. Information about the directors and executive officers of Celgene is set forth in its Annual Report on Form 10-K for the year ended December 31, 2017, which was filed with the SEC on February 7, 2018 its proxy statement for its 2018 annual meeting of stockholders, which was filed with the SEC on April 30, 2018, and its Current Reports on Form 8-K, which were filed with the SEC on June 1, 2018, June 19, 2018 and November 2, 2018. Other information regarding the participants in the proxy solicitations and a description of their direct and indirect interests, by security holdings or otherwise, are contained in the definitive joint proxy statement/prospectus of Bristol-Myers Squibb and Celgene filed with the SEC and other relevant materials to be filed with the SEC regarding the proposed transaction when they become available. You may obtain these documents (when they become available) free of charge through the website maintained by the SEC at http://www.sec.gov and from Investor Relations at Bristol-Myers Squibb or Celgene as described above.

Cautionary Statement Regarding Forward-Looking Statements

This communication contains forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended.  You can generally identify forward-looking statements by the use of forward-looking terminology such as “anticipate,” “believe,” “continue,” “could,” “estimate,” “expect,” “explore,” “evaluate,” “intend,” “may,” “might,” “plan,” “potential,” “predict,” “project,” “seek,” “should,” or “will,” or the negative thereof or other variations thereon or comparable terminology.  These forward-looking statements are only predictions and involve known and unknown risks and uncertainties, many of which are beyond Bristol-Myers Squibb’s and Celgene’s control. You are cautioned not to rely on Bristol-Myers Squibb’s and Celgene’s forward-looking statements. These forward-looking statements are and will be based upon management’s then-current views and assumptions regarding future events and operating performance, and are applicable only as of the dates of such statements. You also should understand that it is not possible to predict or identify all such factors and that this list should not be considered a complete statement of all potential risks and uncertainties. Investors also should realize that if underlying assumptions prove inaccurate or if unknown risks or uncertainties materialize, actual results could vary materially from Bristol-Myers Squibb’s or Celgene’s projections. Except as otherwise required by law, neither Bristol-Myers Squibb nor Celgene is under any obligation, and each expressly disclaim any obligation, to update, alter, or otherwise revise any forward-looking statements included in this communication or elsewhere, whether written or oral, that may be made from time to time relating to any of the matters discussed in this communication, whether as a result of new information, future events or otherwise, as of any future date.