On June 3, 2023 Cogent Biosciences, Inc. (Nasdaq: COGT), a biotechnology company focused on developing precision therapies for genetically defined diseases, reported positive lead-in data from its ongoing Phase 3 PEAK trial evaluating the selective KIT D816V inhibitor bezuclastinib in patients with Gastrointestinal Stromal Tumors (GIST) (Press release, Cogent Biosciences, JUN 3, 2023, View Source [SID1234632417]). The data are being presented today in a poster presentation at the American Society of Clinical Oncology (ASCO) (Free ASCO Whitepaper) Annual Meeting in Chicago, IL.

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"The results presented today from the lead-in portion of the PEAK study are very encouraging, as the data continue to show that the combination of bezuclastinib and sunitinib has impressive clinical activity in highly refractory GIST patients and is well-tolerated," said Andrew Wagner, M.D., Ph.D., Senior Physician, Center for Sarcoma and Bone Oncology, Dana-Farber Cancer Institute, and Associate Professor of Medicine, Harvard Medical School. "These data reinforce the importance of the ongoing Phase 3 PEAK clinical trial, which has the potential to bring a new standard of care to imatinib-resistant GIST patients."

"These data reinforce our belief that the combination of bezuclastinib and sunitinib has the potential to become a new treatment option for second-line GIST patients," said Andrew Robbins, President, and Chief Executive Officer at Cogent Biosciences. "We are pleased to demonstrate in a robust clinical dataset that the addition of bezuclastinib to sunitinib does not appear to change the frequency or severity of adverse events associated with sunitinib monotherapy. In addition, we are encouraged by the performance of this combination in second-line GIST patients, the population we are currently enrolling in the Phase 3 PEAK clinical trial, with a disease control rate of 100% and 4 out of 7 patients now on treatment for more than 10 cycles."

PEAK Study Design
The PEAK study is a randomized, open-label, global, Phase 3 clinical trial evaluating bezuclastinib in combination with sunitinib in GIST patients previously treated with imatinib. As of the data cutoff date of March 29, 2023, 39 patients had been treated in Part 1, with 19 patients in Part 1a and 20 patients in Part 1b. Seven patients had received only imatinib as prior therapy, and 32 patients had received at least 2 prior tyrosine kinase inhibitor (TKI) therapies.

Safety Data
As of the cutoff date of March 29, 2023, the combination of bezuclastinib and sunitinib was generally well-tolerated with an encouraging safety profile. The majority of treatment-emergent adverse events (TEAEs) were low-grade and reversible, with a low rate of Grade 3 or higher events observed. 23% of patients experienced dose reductions of either medication, and only two patients discontinued treatment due to adverse events. Across Part 1a and Part 1b, there were only two patients with serious adverse events reported that were possibly associated with either study medication including one patient with grade 2 neutrophil count decrease and pyrexia and grade 3 platelet count decrease and one patient with grade 2 bacterial peritonitis and grade 3 febrile neutropenia. Overall, the safety and tolerability profile of the combination appears consistent with that of single-agent sunitinib, suggesting that bezuclastinib is not adding to the overall frequency or severity of adverse events associated with single-agent sunitinib.

Clinical Activity Data
As of the cutoff date, 39 patients had been treated for at least one 28-day cycle, with a range of 1-13 cycles, and 25 of the 39 patients continue to receive treatment. Data were immature to estimate median progression free survival. Across the efficacy evaluable patients in Part 1, the disease control rate (CR + PR + durable SD) is currently 55%; including a 100% disease control rate and 17% ORR among the efficacy evaluable 2nd-line patients in Part 1a. Across the study, 21 patients have demonstrated radiographic evidence of reduction in target lesion diameter, including 4 patients who have achieved partial response. Among those responders the time to first response was as long as 8 cycles, suggesting that patients currently early in treatment may achieve responses over time.

As of June 1, 2023 four of the seven 2nd-line patients in Part 1a remain on study with at least 10 cycles of therapy.

Bezuclastinib Clinical Development
Cogent is actively enrolling patients in Part 2 of the Phase 3 registration-enabling PEAK trial, which is expected to include approximately 388 second-line, post imatinib GIST patients. Additionally, Cogent remains on track to present initial clinical data from SUMMIT, a randomized, double-blind, placebo-controlled, global, multicenter, Phase 2 trial of bezuclastinib in patients with nonadvanced systemic mastocytosis in the second half of 2023. Data will include safety/tolerability, pharmacokinetics, and measures of clinical activity. The Company also expects to present clinical data from approximately 30 patients in Part 1 of the Phase 2 APEX trial in patients with advanced systemic mastocytosis at a scientific meeting in the second half of 2023.

Webcast Information and ASCO (Free ASCO Whitepaper) Poster
Cogent will host a webcast on Monday, June 5, 2023 at 8:00 a.m. ET (7:00 a.m. CT) to discuss today’s update, with participation from Andrew Wagner, M.D., Ph.D., Senior Physician, Center for Sarcoma and Bone Oncology, Dana-Farber Cancer Institute, and Associate Professor of Medicine, Harvard Medical School. The live event can be accessed on the Investor page of Cogent’s website at investors.cogentbio.com. A replay of the webcast will be available approximately two hours after the completion of the event and will be archived for up to 30 days.

The ASCO (Free ASCO Whitepaper) poster is available to registered conference attendees and is also in the Posters and Publications section of Cogent’s website at www.cogentbio.com/research.