News Releases
Theseus Pharmaceuticals to Present Preclinical Data Characterizing Next-Generation Epidermal Growth Factor Receptor (EGFR) Inhibitors at the 2022 American Association for Cancer Research (AACR) Annual Meeting

CAMBRIDGE, Mass., March 8, 2022 /PRNewswire/ -- Theseus Pharmaceuticals, Inc. (NASDAQ: THRX) (Theseus or the Company), 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 Company will present a poster highlighting the characterization of potent and selective next-generation EGFR inhibitors at the American Association for Cancer Research (AACR) 2022 Annual Meeting, being held April 8-13, 2022 in New Orleans, Louisiana.

Presentation details:
Abstract Title: Discovery of potent and selective next-generation EGFR inhibitors with activity against single, double, and triple mutant EGFR variants including T790M and C797S 
Abstract Number: 3342
Presenter: Wei-Sheng Huang, Ph.D., Vice President of Chemistry
Session Date and Time: Tuesday, April 12th, 1:30pm-5pm CT

The presentation will detail the characterization of compounds that potently inhibit the kinase activity, both in vitro and in vivo, of single, double, and triple mutant EGFR variants including T790M and C797S, with selectivity over wild-type EGFR and the ability to penetrate the central nervous system. These variants comprise all major classes of EGFR activating and resistance mutations that contribute to later-line clonal heterogeneity in patients who have been failed by current approved therapies.

EGFR activating mutations are observed in 10-50 percent of non-small cell lung cancer (NSCLC) patients and are initially sensitive to first, second, and third generation EGFR inhibitors. However, on-target resistance is observed in a substantial percentage of patients, with T790M and C797S mutations observed most frequently.

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