C4 Therapeutics, Inc. (Nasdaq: CCCC) filed a Current Report on Form 8-K on September 25, 2026, announcing new biomarker data from clinical trials of its drug candidate cemsidomide in patients with relapsed/refractory multiple myeloma (RRMM). The data was presented at the 23rd International Myeloma Society (IMS) Annual Meeting.
The filing details results from two separate trials. In the Phase 1 trial, cemsidomide was administered in combination with dexamethasone to 62 heavily pre-treated RRMM patients. The data indicates that the drug demonstrated coordinated activation of T cells, including CD8+ T cells, and functional reprogramming of natural killer (NK) cells. Specifically, enhanced immune cell function was observed at the highest dose levels studied (75 micrograms and 100 micrograms).
In the Phase 1b trial, cemsidomide is being tested in combination with elranatamab (ELREXFIO), an FDA-approved bispecific antibody. Biomarker data from the first two patients showed that cemsidomide drives the expansion and activation of CD8+ effector memory T cells, as measured by elevated HLA-DR. Additionally, the data showed a reduction in markers associated with T-cell exhaustion, including PD-1, TIM-3, and LAG3 expression.
Regarding trial progress, the safety data review committee declared the 75 microgram dose level of cemsidomide in combination with elranatamab safe following the evaluation of six patients in the first safety cohort. As a result, the trial is advancing to a dose escalation safety cohort at the 100 microgram dose level and an expansion cohort at the 75 microgram dose level. Data from all cohorts evaluated in the Phase 1b trial are expected in mid-2027.
