C4 Therapeutics Presents New Data on Cemsidomide in Multiple Myeloma Trials

WATERTOWN, Mass., Sept. 25, 2026 /CourierPR/ -- C4 Therapeutics, Inc. (C4T) presented new biomarker data from its Phase 1 clinical trial of cemsidomide in combination with dexamethasone at the 23rd International Myeloma Society (IMS) Annual Meeting. The data demonstrated robust T-cell activation, a key component of cemsidomide’s dual mechanism of action, in patients with relapsed/refractory multiple myeloma (RRMM).

In the Phase 1 trial, cemsidomide, an investigational oral cereblon-modulating protein degrader of IKZF1/3, showed coordinated activation of T cells, including CD8+ T cells, and functional reprogramming of natural killer (NK) cells. Notably, the highest dose levels (75 µg and 100 µg) achieved compelling overall response rates. The trial involved 62 heavily pre-treated RRMM patients, with the once-daily dose levels showing enhanced immune cell function.

Additionally, C4 Therapeutics shared preliminary biomarker data from the first two patients in the ongoing Phase 1b trial of cemsidomide in combination with elranatamab (ELREXFIO®). The data indicated that cemsidomide drives the expansion and activation of CD8+ effector memory T cells, as measured by elevated HLA-DR, and prevents T-cell exhaustion, as measured by PD-1, TIM-3, and LAG3 expression. These findings provide positive translational and mechanistic support for cemsidomide as a potential combination partner for immune-based therapies.

Following the completion of the first safety cohort, the safety data review committee declared the 75 µg cemsidomide dose level in combination with elranatamab safe. The Phase 1b trial is now advancing into a dose escalation safety cohort at the 100 µg cemsidomide dose level and an expansion cohort at the 75 µg cemsidomide dose level. Data from all cohorts evaluated in the Phase 1b trial are expected in mid-2027.

Cemsidomide is an investigational oral cereblon-modulating protein degrader of IKZF1/3, foundational to multiple myeloma biology. The fully enrolled Phase 1 trial showed cemsidomide’s differentiated safety and tolerability profile and potentially class-leading anti-myeloma activity, supporting the potential for durable outcomes. The Phase 1b trial is designed to evaluate the safety, tolerability, and preliminary efficacy of cemsidomide and dexamethasone in combination with elranatamab, an FDA-approved B-cell maturation antigen CD3 targeted bispecific antibody. The study will explore different cemsidomide dose levels, beginning with 75 µg, with the opportunity to simultaneously explore 50 µg and 100 µg, in patients who have received one to four prior lines of therapy, which must have included at least one IKZF1/3 degrader.

Multiple myeloma is a blood cancer that affects plasma cells in the bone marrow, with approximately 36,000 people in the United States diagnosed each year. It is characterized by cycles of remission and relapse, leading to patients needing multiple lines of therapy to manage the persistent disease. More than 175,000 patients in the United States are estimated to be living with or in remission from myeloma. Despite treatment advances, approximately 40% of patients do not survive beyond five years.