Cogent Biosciences Announces Final Results from PLX9486 Phase 1/2 Study in Advanced GIST Patients at CTOS 2020

CAMBRIDGE, Mass., Nov. 18, 2020 /PRNewswire/ -- Cogent Biosciences, Inc. (Nasdaq: COGT), a biotechnology company focused on developing precision therapies for genetically defined diseases, today announced the final results from its PLX9486 + sunitinib Phase 1/2 study in patients with advanced gastrointestinal stromal tumors (GIST). The data will be presented, summarized and discussed in a live oral session on Friday, November 20^th from 11:30 a.m. to 12:30 p.m. ET at the Connective Tissue Oncology Society (CTOS) 2020 virtual meeting.

PLX9486 is a selective tyrosine kinase inhibitor designed to potently inhibit KIT exon 17 mutations, including D816V. Most patients with imatinib-resistant GIST have both primary and secondary KIT mutations, often including secondary mutations on exon 17 and exon 13, making it difficult to achieve broad therapeutic KIT inhibition. These data suggest that treatment with a combination of PLX9486, a type 1 KIT inhibitor with activity against exon 17 mutations, and sunitinib, a type 2 KIT inhibitor with activity against exon 13 mutations, may provide substantial clinical benefit over treatment with type I or type II inhibitors alone.

"We are pleased to share final results from our Phase 1/2 trial of PLX9486 + sunitinib and are excited to advance this combination into a Phase 3 GIST trial in the second half of 2021," said Andrew Robbins, President and CEO of Cogent Biosciences. "With a median progression free survival (PFS) of 12 months in a heavily pre-treated population of advanced GIST patients, this combination holds significant promise for these patients with unmet medical need."

Oral Presentation:

Abstract: 3458521

Title: The potent and selective kit inhibitor PLX9486 dosed in combination with sunitinib demonstrates promising progression free survival (PFS) in patients with advanced gastrointestinal stromal tumor (GIST): final results of a phase 1/2 study.

Date: November 20, 2020

Time: Session 8: 11:30 a.m. - 12:30 p.m. ET

"The final results from this Phase 1/2 trial are highly encouraging for GIST patients who have limited treatment options due to secondary resistance KIT mutations," said Jonathan Trent, M.D., Ph.D., Associate Director for Clinical Research, Sylvester Comprehensive Cancer Center, University of Miami Health System. "I look forward to participating in the upcoming trial of this promising combination for imatinib-resistant GIST patients."

Results:

Out of the 18 patients with advanced GIST enrolled in the trial, all patients had received prior treatment, including 67% of patients with at least three prior lines of therapy. Doses for this study included 3 levels:

• Level 1: PLX9486 500mg + sunitinib 25mg (3 patients)
• Level 2: PLX9486 1000mg + sunitinib 25mg (5 patients)
• Level 3: PLX9486 1000mg + sunitinib 37.5mg (10 patients)

Among the 15 patients who had not previously received PLX9486 as a single agent, the median progression free survival (PFS) was 12 months, the confirmed ORR was 20% and the clinical benefit rate (CR+PR+SD) was 80%, with 27% of patients remaining on therapy out 27-34 months. Importantly, there were no dose limiting toxicities in the three dose levels tested, and the most common adverse events were anemia, hypophosphatemia, diarrhea, and lymphopenia.

About Cogent Biosciences, Inc. 

Cogent Biosciences is a biotechnology company focused on developing precision therapies for genetically defined diseases. The most advanced clinical program, PLX9486, is a selective tyrosine kinase inhibitor that is designed to potently inhibit the KIT D816V mutation as well as other mutations in KIT exon 17. KIT D816V is responsible for driving systemic mastocytosis, a serious disease caused by unchecked proliferation of mast cells. Exon 17 mutations are also found in patients with advanced gastrointestinal stromal tumors (GIST), a type of cancer with strong dependence on oncogenic KIT signaling. Cogent Biosciences is headquartered in Cambridge, MA. Visit our website for more information at www.cogentbio.com. Follow Cogent Biosciences on social media: Twitter and LinkedIn.

Forward Looking Statements

This press release contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995, including, but not limited to, statements regarding: projected cash runways; future product development plans; upcoming results from clinical trials including from its lead program, PLX9486. The use of words such as, but not limited to, "anticipate," "believe," "continue," "could," "estimate," "expect," "intend," "may," "might," "plan," "potential," "predict," "project," "should," "target," "will," or "would" and similar words expressions are intended to identify forward-looking statements. Forward-looking statements are neither historical facts nor assurances of future performance. Instead, they are based on our current beliefs, expectations and assumptions regarding the future of our business, future plans and strategies, our clinical results and other future conditions. New risks and uncertainties may emerge from time to time, and it is not possible to predict all risks and uncertainties. No representations or warranties (expressed or implied) are made about the accuracy of any such forward-looking statements. We may not actually achieve the forecasts disclosed in our forward-looking statements, and you should not place undue reliance on our forward-looking statements. Such forward-looking statements are subject to a number of material risks and uncertainties including but not limited to those set forth under the caption "Risk Factors" in Cogent's most recent Annual Report on Form 10-K filed with the SEC, as well as discussions of potential risks, uncertainties, and other important factors in our subsequent filings with the SEC. Any forward-looking statement speaks only as of the date on which it was made. Neither we, nor our affiliates, advisors or representatives, undertake any obligation to publicly update or revise any forward-looking statement, whether as result of new information, future events or otherwise, except as required by law. These forward-looking statements should not be relied upon as representing our views as of any date subsequent to the date hereof.

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SOURCE Cogent Biosciences, Inc.