As filed with the Securities and Exchange Commission on December 11, 2025 Registration No. 333-291628 UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM S-1 (Amendment No. 1) REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933 SHUTTLE PHARMACEUTICALS HOLDINGS, INC. (Exact name of registrant as specified in its charter) David E. Danovitch, Esq. Aaron M. Schleicher, Esq. Sullivan & Worcester LLP 1251 Avenue of the Americas, 19 Floor New York, NY 10020 (212) 660-3060 From time to ...

(Exact name of registrant as specified in its charter) FORM S-1 REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933 SHUTTLE PHARMACEUTICALS HOLDINGS, INC. As filed with the Securities and Exchange Commission on November 18, 2025 Registration No. 333- UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 401 Professional Drive, Suite 260 Gaithersburg, MD 20879 (240) 430-4212 (Address, including zip code, and telephone number, including area code, of registrant's principal executive offi ...

As filed with the Securities and Exchange Commission on August 4, 2025 Registration No. 333- UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM S-1 REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933 SHUTTLE PHARMACEUTICALS HOLDINGS, INC. (Exact name of registrant as specified in its charter) If this Form is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, check the following box and list the Securities Act registration statement number of the ...

Core Insights - Shuttle Pharmaceuticals is focused on improving outcomes for cancer patients treated with radiation therapy, with significant progress in its Phase 2 clinical trial for Ropidoxuridine in glioblastoma treatment [1][2] - The company is also advancing its Diagnostics subsidiary through a research agreement with UCSF and has filed a provisional patent for PSMA-targeted therapies [1][2] Phase 2 Clinical Trial Highlights - Nearly 50% of patient enrollment achieved in the initial randomized portion of the trial [2] - 84% of enrolled patients completed all seven cycles of treatment [2] - Ropidoxuridine has been well-tolerated, with reported toxicity no greater than 2 on a scale of 1-5 [2] - Analysis of pharmacokinetic and pharmacodynamic samples has begun to optimize dosing and response [2] - Enrollment continues at recognized cancer centers, with the objective to finalize enrollment later this year and data readouts anticipated in 2026 [2] Diagnostics Subsidiary Developments - A sponsored research agreement with UCSF aims to develop a PSMA-targeted ligand for theranostic applications in prostate cancer [1][2] - A provisional patent application for "PSMA-Targeted PARP Inhibitor Conjugates for Precision Cancer Therapy" has been filed in collaboration with Dr. Alan Kozikowski [1][2] Corporate Governance and Financial Position - Three new board members have been appointed to enhance the company's strategic direction [1][2] - The company has strengthened its balance sheet through a recent public offering, with cash and cash equivalents reported at $4.5 million as of March 31, 2025 [2]

Core Insights - Shuttle Pharmaceuticals is advancing its Phase 2 clinical trial for Ropidoxuridine, targeting glioblastoma patients, with nearly 50% enrollment achieved and positive early results regarding drug tolerance [1][2][3] - The company aims to finalize enrollment by the end of 2025, with data readout expected in 2026 [1][3] Company Overview - Shuttle Pharmaceuticals is a specialty pharmaceutical company founded in 2012, focused on enhancing outcomes for cancer patients undergoing radiation therapy [8] - The company's mission is to develop therapies that maximize the effectiveness of radiation therapy while minimizing side effects [8] Clinical Trial Details - The Phase 2 trial involves randomizing 40 patients into two dosage groups (1,200 mg/day and 960 mg/day) to identify the optimal dose for glioblastoma treatment [3] - Following the identification of the optimal dose, an additional 14 patients will be enrolled to achieve statistical significance in survival outcomes compared to historical controls [3] Market Opportunity - Approximately 800,000 patients in the US receive radiation therapy annually, with 50% treated for curative purposes, representing a significant market for radiation sensitizers [6] - The market for radiation sensitizers is expected to grow by over 22% in the next five years, driven by the 400,000 patients treated for curative purposes [6] Industry Impact - The trial is seen as critical for the radiation therapy industry, aiming to leverage radiation sensitizers to improve cancer cure rates and patient quality of life [5]

Core Insights - Shuttle Pharmaceuticals Holdings, Inc. has appointed Christopher Cooper as interim Co-Chief Executive Officer to enhance capital markets and business capabilities [1][2] - Dr. Anatoly Dritschilo will continue as Co-CEO, focusing on scientific and clinical trial activities [1][2] - The dual CEO structure aims to improve decision-making, support fundraising, and accelerate key milestones [2] Company Overview - Shuttle Pharmaceuticals, founded in 2012, is a specialty pharmaceutical company focused on improving outcomes for cancer patients undergoing radiation therapy [3] - The company's mission is to develop therapies that maximize the effectiveness of radiation therapy while minimizing side effects [3] - Shuttle Pharma aims to increase cancer cure rates, prolong survival, and improve quality of life through the development of radiation sensitizers [3] Leadership Background - Christopher Cooper has over 27 years of experience in management and finance across various industries, including telecommunications and oil and gas [2] - He has held significant positions such as President and CEO of First Towers & Fiber Corp. and Aroway Energy, Inc. [2] - Cooper has a proven track record in overseeing operations, financial reporting, and raising over $100 million in debt and equity for clients [2]

Registration No. As filed with the U.S. Securities and Exchange Commission on April 5, 2024 UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM S-1 REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933 Shuttle Pharmaceuticals Holdings, Inc. (Exact name of registrant as specified in its charter) (State or other jurisdiction of incorporation or organization) Delaware 2834 82-5089826 (Primary Standard Industrial Classification Code Number) (I.R.S. Employer Identification Number) 401 ...

As filed with the Securities and Exchange Commission on January 30, 2023 Registration No. 333-269414 UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 AMENDMENT NO. 1 TO FORM S-1 REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933 SHUTTLE PHARMACEUTICALS HOLDINGS, INC. (Exact name of registrant as specified in its charter) | Delaware | 2834 | 82-5089826 | | --- | --- | --- | | (State or other jurisdiction of | (Primary Standard Industrial | (I.R.S. Employer | | incorporation or org ...

As filed with the Securities and Exchange Commission on January 25, 2023 Registration No. UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM S-1 REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933 SHUTTLE PHARMACEUTICALS HOLDINGS, INC. (Exact name of registrant as specified in its charter) (State or other jurisdiction of incorporation or organization) (Primary Standard Industrial Delaware 2834 82-5089826 (I.R.S. Employer Identification No.) One Research Court, Suite 450 Rockvil ...