Shuttle Pharmaceuticals Holdings, Inc.

About Us—Business Overview

Founded by Georgetown University Medical School faculty members, Shuttle Pharmaceuticals Holdings, Inc. is a discovery and development stage pharmaceutical company leveraging our proprietary technology to develop novel therapies that are designed to cure cancer. Originally formed as Shuttle Pharmaceuticals, LLC in 2012, our goal is to extend the benefits of cancer treatments by leveraging insights into cancer therapy with surgery, radiation therapy, chemotherapy and immunotherapy. While there are several therapies being developed with the goal of curing cancer, one of the most effective and proven approaches to this is radiation therapy (“RT”). We are developing a pipeline of products designed to address the limitations of the current standard of cancer therapies. We believe that our product candidates will enable us to deliver cancer treatments that are safer, more reliable and at a greater scale than that of the current standard of care.

Our operations to date have focused on continuing our research and development efforts to advance Ropidoxuridine clinical testing and improved drug formulation, to advance HDAC6 inhibitor (SP-2-225) preclinical development and explore the application of the PC-RAD Test, predictive biomarkers of radiation response. The clinical development of Ropidoxuridine has included completion of a Phase I clinical trial to establish drug bioavailability and a maximum tolerated dose for use in Phase II clinical trials. TCG GreenChem, with whom we have contracted for process research, development and cGMP compliant manufacture of IPdR, has manufactured the API of Ropidoxuridine and the University of Iowa Pharmaceuticals has formulated the drug product for use in our current Phase II clinical trial in brain cancer patients undergoing radiation therapy. The drug product (capsules) were shipped to CRO Theradex Oncology and distributed to clinical trial sites that are fully approved to enroll patients in the trial. Shuttle Pharma received approval from the FDA to begin the clinical trial. The FDA thereafter made recommendations to expand the clinical trial to include a randomized dose “optimization” step and we agreed with the recommendation. Meetings with engaged clinical sites to review the protocol documents have occurred and FDA required IRB approvals have been received. With FDA recommended changes incorporated into the revised protocol and the completion of site initiation visits, we commenced our Phase II clinical study in October 2024. The Company’s radiation biomarker project and the health disparities project have been completed and we are proceeding with plans for clinical validation and potential for commercialization of Ropidoxuridine as a radiation sensitizer.

Corporate Information

The Company was formed as a limited liability company in the state of Maryland in December 2012 and was converted to a C corporation in August 2016. In June 2018, we completed a share exchange with Shuttle Pharma Acquisition Corp. Inc. (“Acquisition Corp.”), pursuant to which Shuttle Pharmaceuticals, Inc. became a subsidiary of Acquisition Corp. and we subsequently changed the name of Acquisition Corp. to Shuttle Pharmaceuticals Holdings, Inc.

Our executive offices are located at 401 Professional Drive, Suite 260, Gaithersburg, MD 20879 and our telephone number is (240) 430-4212. Our corporate website is www.shuttlepharma.com. Our Annual Reports on Form 10-K, Quarterly Reports on Form 10-Q, Current Reports on Form 8-K, and all amendments to those reports, if any, are available to you free of charge through the “Investor Relations” section of our website as soon as reasonably practicable after such materials have been electronically filed with or furnished to the SEC. Information contained on our website does not form a part of this prospectus.

Private Placement

On November 3, 2025, we entered into a securities purchase agreement (the “Purchase Agreement”) with an accredited investor, for the sale by the Company to the investor, in a private placement, of a pre-funded warrant to purchase up to 625,156 shares of common stock for aggregate gross proceeds of approximately $2.5 million. The private placement closed on November 4, 2025.

The pre-funded warrant is immediately exercisable, at a nominal exercise price of $0.001, and may be exercised at any time until the pre-funded warrant is exercised in full. The pre-funded warrant may not be exercised to the extent such exercise would result in the holder beneficially owning more than 4.99% of the Company’s outstanding common stock.

Pursuant to the Purchase Agreement, the Company agreed to file a registration statement with the SEC to register for resale the shares of the shares issuable upon exercise of the pre-funded warrant issued under the Purchase Agreement within 15 days of the date of the Purchase Agreement, and to have such registration statement declared effective within 45 days of the date of the Purchase Agreement (or 75 days if the registration statement is reviewed by the SEC).

WestPark Capital, Inc. (“WestPark”) acted as the placement agent in connection with the private placement pursuant to a placement agency agreement between the Company and WestPark (as amended, the “Placement Agency Agreement”). Pursuant to the Placement Agency Agreement, the Company paid WestPark a cash fee of 4% of the gross proceeds received by the Company in the private placement. The Company also reimbursed certain expenses of WestPark.

This prospectus covers the resale of the 625,156 shares of common stock issuable upon exercise of the pre-funded warrant issued under the Purchase Agreement.