C4 Therapeutics Presents Cemsidomide Phase 1 Multiple Myeloma Data Supporting Potential Best-in-Class Profile at the International Myeloma Society Annual Meeting

Cemsidomide in Combination With Dexamethasone Achieved a 50% Overall Response Rate (ORR) at the Highest Dose Level (100 µg) and a 40% ORR at the 75 µg Dose Level in a Heavily Pre-Treated Relapsed/Refractory Multiple Myeloma Patient Population

Responses Across Dose Levels With Median Duration of Response of 9.3 Months as of the Data Cut-off Date; Median Duration of Response Not Yet Reached at Two Highest Doses

No Discontinuations Related to Cemsidomide and Few Dose Reductions Support a Safety Profile That May Be Ideal for Combination Regimens

C4T to Pursue Differentiated Development Strategy With Two Distinct Opportunities for Accelerated Approval in Second Line and Later

C4T to Host Webcast Today at 3 pm ET; Webcast Link Available Here

Excerpt from the Press Release:

WATERTOWN, Mass., Sept. 20, 2025 (GLOBE NEWSWIRE) — C4 Therapeutics, Inc. (C4T) (Nasdaq: CCCC), a clinical-stage biopharmaceutical company dedicated to advancing targeted protein degradation science, today presented data from the Phase 1 clinical trial of cemsidomide, an orally bioavailable IKZF1/3 degrader, in combination with dexamethasone for the treatment of relapsed/refractory multiple myeloma (RRMM). With enrollment in the Phase 1 trial complete, data continue to show cemsidomide’s differentiated safety and tolerability profile and potentially class-leading anti-myeloma activity, supporting clear development paths for second line and later patient populations.

“Cemsidomide’s clinical trial results to date have shown compelling anti-myeloma activity, a differentiated safety and tolerability profile and immunomodulatory effects across all dose levels, which have allowed us to create a derisked development plan that we are prepared to rapidly execute to potentially bring cemsidomide to patients, caregivers and hematologist-oncologists,” said Len Reyno, M.D., chief medical officer of C4 Therapeutics. “As we prepare to initiate the Phase 2 study in Q1 2026 to evaluate cemsidomide in combination with dexamethasone and the Phase 1b study in Q2 2026 to evaluate cemsidomide and dexamethasone in combination with a BCMA BiTE—both development pathways that have the potential for accelerated approval—we are excited to further differentiate cemsidomide as the IKZF1/3 degrader of choice among approved medicines in this class, which are used across lines of therapy and in various combination regimens. We look forward to generating data in the future that further demonstrates cemsidomide’s potential to become a class-leading IKZF1/3 degrader across the growing populations of relapsed/refractory multiple myeloma patients.”

Approved IKZF1/3 degraders remain backbone therapy across lines of multiple myeloma treatment, even as novel therapeutic approaches enter the treatment landscape. Recent advances in treatment, including immune-directed therapies, are not cures and the majority of patients ultimately relapse, creating a need for new medicines targeted at these heavily pretreated patients.

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