C4 Therapeutics presents cemsidomide biomarker data at IMS Annual Meeting

C4 Therapeutics announced on September 25, 2026 that it presented new biomarker data from its cemsidomide program in relapsed/refractory multiple myeloma at the 23rd International Myeloma Society Annual Meeting, covering both a Phase 1 trial of cemsidomide with dexamethasone and a Phase 1b trial combining cemsidomide with elranatamab, sold as ELREXFIO.

In the Phase 1 trial, 62 heavily pre-treated RRMM patients across once-daily dose levels showed coordinated activation of T cells, including CD8+ T cells, and functional reprogramming of natural killer cells.¹ The company said immune cell function was strongest at the two highest dose levels tested, 75 µg and 100 µg, and those same dose levels also produced the best overall response rates in the trial.¹

For the Phase 1b combination trial with elranatamab, data came from the first two patients. The company reported that these patients showed increased activity and growth of a specific type of T cell, along with markers suggesting reduced T-cell exhaustion, based on biomarker data available as of June 22, 2026, from the first two patients to complete Cycle 1.¹

On the safety side, after six patients completed the first safety cohort, the trial's safety data review committee declared the 75 µg cemsidomide dose safe, and the study is now moving into a 100 µg dose escalation cohort and a 75 µg expansion cohort.¹ Data from all cohorts in the Phase 1b trial are expected in mid-2027.¹

The Phase 1b study design allows testing of multiple starting doses in patients who received one to four prior treatment lines, with the requirement that at least one prior line included an IKZF1/3 degrader.¹ Patients previously treated with a BCMA-directed T-cell engager or CAR-T therapy are excluded, according to the release.