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Theseus Pharmaceuticals Receives U.S. FDA Orphan Drug Designation for THE-630 for the Treatment of Advanced Gastrointestinal Stromal Tumors (GIST)

CAMBRIDGE, Mass., Feb. 2, 2022 /PRNewswire/ -- Theseus Pharmaceuticals, Inc. (Theseus) (NASDAQ: THRX), a clinical-stage biopharmaceutical company focused on improving the lives of cancer patients through the discovery, development and commercialization of transformative targeted therapies, today announced that the U.S. Food and Drug Administration (FDA) has granted orphan drug designation (ODD) to the company's lead candidate THE-630, a small-molecule oral pan-variant KIT inhibitor, for the treatment of patients with advanced gastrointestinal stromal tumors (GIST).

"We are pleased to have received ODD for THE-630 so quickly after the initiation of the first-in-human trial. This designation from the FDA emphasizes the need to bring better therapeutic options to patients with advanced GIST," said David Kerstein, M.D., Chief Medical Officer at Theseus. "For patients living with GIST, progression through standard lines of therapy is often associated with the emergence of resistance mutations in KIT. We look forward to evaluating the clinical potential of THE-630 to inhibit these resistance mutations in patients who've exhausted available therapies and when used in earlier lines of therapy."

The FDA's Office of Orphan Products Development grants ODD status to drugs and biologics intended for the safe and effective treatment, diagnosis or prevention of rare diseases or conditions affecting fewer than 200,000 people in the United States. ODD provides benefits to drug developers designed to support the development of drugs and biologics for small patient populations with unmet medical needs. These benefits include assistance in the drug development process, tax credits for qualified clinical costs, exemptions from certain FDA fees and seven years of marketing exclusivity.

About GIST
GIST is the most common sarcoma of the gastrointestinal tract with an estimated 4,000 to 6,000 new cases diagnosed in the United States each year. Approximately eighty percent of GIST cases are driven by mutations that activate the kinase activity of the receptor tyrosine kinase KIT, and up to ninety percent of all cases of progression are driven by secondary resistance mutations in KIT.

About Theseus Pharmaceuticals, Inc.
Theseus is a clinical-stage biopharmaceutical company focused on improving the lives of cancer patients through the discovery, development and commercialization of transformative targeted therapies. Theseus is working to outsmart cancer resistance by developing pan-variant tyrosine kinase inhibitors (TKIs) to target all known classes of cancer-causing and resistance mutations that lead to variants in a particular protein in a given type of cancer. Theseus' lead product candidate, THE-630, is a pan-variant KIT inhibitor for the treatment of patients with advanced gastrointestinal stromal tumors (GIST), whose cancer has developed resistance to earlier lines of kinase inhibitor therapy. Theseus is also developing a fourth-generation, selective epidermal growth factor receptor (EGFR) inhibitor for C797S-mediated resistance to first- or later-line osimertinib treatment in patients with non-small cell lung cancer (NSCLC). For more information, visit www.theseusrx.com.

Cautionary Statement Regarding Forward Looking Statements
Certain statements included in this press release are not historical facts but are forward-looking statements for purposes of the safe harbor provisions under the United States Private Securities Litigation Reform Act of 1995. Forward-looking statements generally are accompanied by words such as "believe," "may," "will," "estimate," "continue," "anticipate," "intend," "expect," "should," "would," "plan," "predict," "potential," "seem," "seek," "future," "outlook," and similar expressions that predict or indicate future events or trends or that are not statements of historical matters, but the absence of these words does not mean that a statement is not forward-looking. These forward-looking statements include, but are not limited to, statements regarding Theseus' strategy, future operations, prospects and plans, the structure and timing of its planned and ongoing clinical trials and future registrational trials, expected milestones, market opportunity and sizing and objectives of management, including in relation to THE-630 and the Phase 1/2 does escalation and expansion clinical trial and its EGFR and other programs.

Actual results may differ materially from those indicated by such forward-looking statements as a result of various important factors, such as those described from time to time in the reports Theseus files with the Securities and Exchange Commission (SEC), including Theseus' Form 10-Q for the quarter ended September 30, 2021 filed with the SEC on November 15, 2021. However, new risk factors and uncertainties may emerge from time to time, and it is not possible to predict all risk factors and uncertainties. Accordingly, readers are cautioned not to place undue reliance on these forward-looking statements. Any forward-looking statements contained in this press release are based on the current expectations of Theseus' management team and speak only as of the date hereof, and Theseus specifically disclaims any obligation to update any forward-looking statement, whether as a result of new information, future events or otherwise.

Media Contact
Amy Jobe, Ph.D.
LifeSci Communications

Investor Contact
Christen Baglaneas
Theseus Pharmaceuticals

SOURCE Theseus Pharmaceuticals