---
schema_version: "secwatch.filing_event.v1"
accession: "0001628280-26-063497"
form_type: "8-K"
ticker: "CCCC"
cik: "0001662579"
company_name: "C4 Therapeutics, Inc."
filed_at: "2026-09-25T11:04:25+00:00"
generated_at: "2026-10-12T13:17:55.031124+00:00"
event_type: "other_material"
sentiment: "positive"
materiality_score: 0.5
calibrated_materiality_score: 0.5
confidence: "high"
source: SEC EDGAR
---

# C4 Therapeutics cemsidomide biomarker data positive; 75 µg elranatamab combo declared safe, Phase 1b advances

## Summary
- Phase 1 cemsidomide + dexamethasone in 62 heavily pre-treated RRMM patients showed coordinated CD8+ T-cell activation and NK-cell reprogramming at the 75 µg and 100 µg doses.
- Phase 1b cemsidomide + elranatamab (ELREXFIO): first two patients showed CD8+ effector memory T-cell expansion (elevated HLA-DR) with no rise in exhaustion markers PD-1, TIM-3, LAG3.
- Safety data review committee declared the 75 µg cemsidomide dose with elranatamab safe after the first six-patient cohort; trial advancing to a 100 µg escalation cohort and a 75 µg expansion cohort.
- Data from all Phase 1b cohorts evaluated are expected in mid-2027; results presented at the 23rd International Myeloma Society Annual Meeting on September 25, 2026.
- CMO Len Reyno said the data reinforce a strategy to establish cemsidomide as a backbone therapy in multiple myeloma for immune-based combinations.

## SEC filing metadata
- accession: 0001628280-26-063497
- form_type: 8-K
- ticker: CCCC
- cik: 0001662579
- company_name: C4 Therapeutics, Inc.
- filed_at: 2026-09-25T11:04:25+00:00
- event_type: other_material
- sentiment: positive
- materiality_score: 0.5
- calibrated_materiality_score: 0.5
- confidence: high
- sec_items: 7.01, 8.01, 9.01
- EDGAR index: https://www.sec.gov/Archives/edgar/data/1662579/000162828026063497/0001628280-26-063497-index.htm
- EDGAR primary document: https://www.sec.gov/Archives/edgar/data/1662579/000162828026063497/cccc-20260925.htm

## Machine-readable alternates
- HTML: https://secwatch.observer/filing/0001628280-26-063497
- JSON: https://secwatch.observer/filing/0001628280-26-063497.json
- Plain text: https://secwatch.observer/filing/0001628280-26-063497.txt

This AI-assisted summary is a reading aid. Review the linked SEC EDGAR filing before relying on any specific claim.