Key Highlights

  • Shares are trading 7.83% higher at $3.46 on Wednesday, October 28, 2026.
  • Short interest was 42,722,018 shares for the settlement date of October 15, 2026, or 34.7% of shares outstanding.
  • Days to cover was 16.95 on average daily volume of 2,520,136 shares.
  • Cash, equivalents and marketable securities were $300.4 million at June 30, 2026.
  • Phase 1 cemsidomide data showed a 53% overall response rate at the 100 microgram dose.

C4 Therapeutics Shares: What Is Behind the 7.83% Rise in a Heavily Shorted Name?

C4 Therapeutics (NASDAQ:CCCC) shares are trading 7.83% higher at $3.46 on Wednesday, October 28, 2026, which puts the implied prior close near $3.21 (calculated from the price and percentage). No company announcement dated today accompanied the move, and the stock features among both the most shorted names and the most active sub-$5 shares.

C4 is a clinical-stage biopharmaceutical company based in Watertown, Massachusetts. It designs medicines that direct the body's own machinery to break down disease-causing proteins. Its main candidate, cemsidomide, targets multiple myeloma, and it also has CFT8919, an EGFR degrader for non-small cell lung cancer.

Partners include Roche, Betta Pharmaceuticals, Merck KGaA and Biogen (NASDAQ:BIIB). With roughly 123.03 million shares outstanding, the market value is about $426 million at the current price (calculated).

Short Interest: How Could 34.7% of Shares Outstanding Sold Short Shape Volatility?

Short-interest data for the settlement date of October 15, 2026, showed 42,722,018 shares sold short, up 2,326,353 from the prior settlement. That equals about 34.7% of shares outstanding, and no separate float figure was published.

Days to cover was 16.95, based on average daily volume of 2,520,136 shares. A figure that high means short positions would take more than three weeks of typical trading to unwind.

High short interest can magnify price swings, since short sellers buying back shares can add to a rally. The measure shows positioning, not the direction of the next move.

Cemsidomide and Cash: Do Data, a Roche Deal and $300.4M Support the Plan?

At the 2026 European hematology congress, C4 reported overall response rates of 40% at 75 micrograms and 53% at 100 micrograms in relapsed or refractory myeloma. Results included one stringent complete response, two complete responses and two MRD-negative patients, with no cemsidomide-related discontinuations. The sample size is small.

The Phase 2 MOMENTUM trial, with about 100 patients at the 100 microgram dose, is expected to complete enrollment in the first quarter of 2027, with initial response data in the second half of 2027. A Phase 1b combination with elranatamab is due for a dose-escalation update in the second half of 2026. In January the company outlined a new drug application for potential accelerated approval by the end of 2028.

Second-quarter results released in August showed revenue of $6.6 million, research and development of $24.5 million and a net loss of $23.6 million, or $0.18 per share, versus $26.0 million, or $0.37. Cash rose to $300.4 million from $268.3 million at March 31, helped by about $33.5 million from its at-the-market program and a $20.0 million upfront payment from Roche under an April 2026 degrader-antibody conjugate collaboration. Management expects cash to fund operations through the end of 2028.

What to Watch Next: Which 2026 Milestones and Data Dates Are Set?

The next short-interest settlement date is October 30, 2026, with publication expected on November 10. C4 also targets the elranatamab dose-escalation update in the second half of 2026 and delivery of at least one development candidate to a collaboration partner by year-end. MOMENTUM enrollment is expected to complete in the first quarter of 2027, followed by data from all elranatamab cohorts in mid-2027.