Shuttle Pharmaceuticals Holdings, Inc.

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

(Rule 14a - 101)

Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934

Filed by the Registrant ☒

Filed by a Party other than the Registrant ☐

Check the appropriate box:

SHUTTLE PHARMACEUTICALS HOLDINGS, INC.

(Name of Registrant as Specified in Its Charter)

(Name of Person(s) Filing Proxy Statement, if other than the Registrant)

Payment of Filing Fee (Check all boxes that apply):

SHUTTLE PHARMACEUTICALS HOLdIngS, InC.

2026 Annual Meeting of Stockholders

April 20, 2026

Dear Shareholders,

You are cordially invited to attend an Annual Meeting of Stockholders (the “Annual Meeting”) of Shuttle Pharmaceuticals Holdings, Inc. (“Shuttle Pharma,” the “Company,” “we” or “us”) to be held at12:00 p.m.,**** Eastern Time, onMay 21, 2026.

We are very pleased that the Annual Meeting will be a completely virtual meeting of stockholders, which will be conducted via live webcast. The Annual Meeting will be held in a virtual format only, via the Internet, with no physical in-person meeting. You will be able to attend the Annual Meeting online and submit your questions during the meeting by visiting www.virtualshareholdermeeting.com/SHPH2026. You will also be able to vote your shares electronically at the Annual Meeting.

We are pleased to use the latest technology to increase access, to improve communication and to obtain cost savings for our stockholders and the Company. Use of a virtual meeting will enable increased stockholder attendance and participation as stockholders can participate from any location.

At the meeting, you will be asked to:

Only the Company’s stockholders of record at the close of business on March 25, 2026, the record date for the Annual Meeting, are entitled to notice of, and to vote at, the Annual Meeting or any adjournment or postponement of the Annual Meeting.

You can find more information on each of the matters to be voted on at the Annual Meeting, including information regarding the nominees for election to the Company’s board of directors, in the accompanying Proxy Statement. The board of directors recommends a vote “FOR” the election of each of the director nominees, “FOR” the ratification of the appointment of the Company’s independent registered public accounting firm for the fiscal year ending December 31, 2026, “FOR” the approval of the Company’s executive compensation (on an advisory basis), “FOR” the proposal authorizing the Board of Directors to amend the Company’s Certificate of Incorporation, as amended, to effect one or more reverse stock splits of the Company’s outstanding and treasury shares of common stock, at a cumulative ratio in the range from 1-for-2 to 1-for-150, with such specific ratio to be determined by the Company’s Board of Directors following the Annual Meeting, while leaving the number of authorized shares of common stock unchanged, to be effectuated at the Board’s discretion when and as needed, and “FOR” the approval of an adjournment of the Annual Meeting if necessary or appropriate, to permit further solicitation and vote of proxies in the event that there are insufficient votes for, or otherwise in connection with, one or more of the other proposals to be voted on at the Annual Meeting.

We have elected to use the full set delivery option available pursuant to Rule 14a-16(n) under the Securities Exchange Act of 1934, as amended (the “Exchange Act”). Under the full set delivery option, we will deliver the proxy statement, the proxy card and the Annual Report on Form 10-K for the fiscal year ended December 31, 2025 (the “2025 Annual Report”, together with the proxy statement and the proxy card, the “Proxy Materials”), to stockholders by mail. In addition to delivery of the Proxy Materials to stockholders, we will post all Proxy Materials on a publicly-accessible website and provide information to stockholders about how to access the website. The Proxy Statement is dated April 20, 2026 and is first being mailed to stockholders on or about April 20, 2026.

Thank you for your ongoing support of Shuttle Pharma.

Sincerely yours,

/s/ Christopher Cooper

Christopher Cooper

Interim Chief Executive Officer and Director

Shuttle Pharmaceuticals Holdings, Inc.

Notice of Annual Meeting of Stockholders of Shuttle Pharmaceuticals Holdings, Inc.

This notice, proxy statement and voting instructions are being mailed to stockholders beginning on or about April 20, 2026.

Your vote is important

Regardless of whether you plan to attend the live meeting, we encourage you to vote as soon as possible in one of the following ways:

Important Notice Regarding the Availability of Proxy Materials for the Stockholder Meeting to Be Held on Thursday, May 21, 2026. A printed copy of the Proxy Statement, proxy card and the Annual Report on Form 10-K for the fiscal year ended December 31, 2025 (the “2025 Annual Report”, together with the proxy statement and the proxy card, the “Proxy Materials”) (collectively, the “Proxy Materials”) are first being mailed to stockholders of record entitled to receive notice of the Annual Meeting on or about April 20, 2026.

Our Proxy Statement is available on our website at https://shuttlepharma.com/. For further information about the Company, including copies of our audited financial statements for the fiscal year ended December 31, 2025, please see our 2025 Annual Report, as well as other filings made with the Securities and Exchange Commission, or the SEC, since that date.

If your shares are held in the name of a third-party brokerage firm, nominee, or other institution, only that third party may vote your shares. In that case, please promptly contact the third party responsible for your account and give instructions on how your shares should be voted.

In accordance with rules and regulations adopted by the Securities and Exchange Commission, it is important that your shares be represented and voted, whether or not you plan to attend the Annual Meeting. If you are the registered holder of your shares and are receiving a paper copy of the Proxy Materials, you may vote by completing and mailing the proxy card enclosed with the proxy statement. If your shares are held in “street name,” which means your shares are held of record by a broker, bank or other nominee, you should review the Proxy Materials used by that firm to determine whether and how you will be able to submit your proxy. Mailing a proxy card will ensure your shares are represented at the Annual Meeting. A list of stockholders entitled to vote at the Annual Meeting will be available for examination by any stockholder for any purpose germane to the Annual Meeting for a period of 10 days ending on the day before the Annual Meeting during ordinary business hours at our principal place of business at 401 Professional Drive, Suite 260, Gaithersburg, MD 20879, or on a reasonably accessible electronic network as provided by the Company. During the Annual Meeting, such list will also be available for examination by clicking the “Resources” button on the screen during the Annual Meeting.

BY ORDER OF THE BOARD OF DIRECTORS,

/s/ Christopher Cooper

Christopher Cooper

Interim Chief Executive Officer

Dated April 20, 2026

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