Cemiplimab Approved for Adjuvant Treatment of High-Risk CSCC
Expert Perspectives · Lyn Brook · 2025-10-13
The FDA has approved cemiplimab‑rwlc (Libtayo®, Regeneron Pharmaceuticals Inc.) for the adjuvant treatment of adults with cutaneous squamous cell carcinoma (CSCC) at high risk of recurrence following surgery and radiation.
Why This Approval Matters
This approval establishes the first adjuvant indication of cemiplimab for patients with high‑risk CSCC after definitive local therapy, addressing a population with substantial relapse risk. Adjuvant cemiplimab significantly prolonged disease‑free survival (DFS) versus placebo, supporting its use to reduce recurrence following surgery and radiation.
Breaking Down the C‑POST Trial
Efficacy was evaluated in C‑POST (NCT03969004), a phase 3, double‑blind, multicenter, placebo‑controlled trial enrolling adult patients with CSCC at high risk of recurrence after surgery and radiation. Prior to randomization, patients completed two to 10 weeks of adjuvant radiation. The trial randomized 415 patients 1:1 to cemiplimab‑rwlc or placebo. Key exclusionary criteria included active autoimmune disease requiring systemic immunosuppression within five years, history of solid organ transplant, prior allogeneic/autologous stem cell transplant, ECOG ≥2, or uncontrolled HIV, HBV, or HCV infection.
The primary end point was DFS, defined as time from randomization to investigator‑assessed recurrence or death from any cause. Results demonstrated a marked benefit with cemiplimab:
- Median DFS: Not reached with cemiplimab versus 49.4 months with placebo
- Hazard ratio: 0.32
Managing Adverse Events
The prescribing information carries warnings and precautions for immune‑mediated adverse reactions, infusion‑related reactions, complications of allogeneic hematopoietic stem cell transplantation, and embryo‑fetal toxicity. Safety considerations align with the known PD‑1 inhibitor class profile.
Dosing and Administration
Recommended dosing options:
- 350 mg IV every 3 weeks for 12 weeks, then 700 mg IV every 6 weeks, or
- 350 mg IV every 3 weeks
Treatment should be continued until disease recurrence or unacceptable toxicity, or for up to 48 weeks.