Intralesional Cemiplimab Shows High Pathologic Response in Early-Stage CSCC

Low-dose intralesional cemiplimab produced high objective and pathologic response rates without treatment-limiting toxicity in patients with early-stage cutaneous squamous cell carcinoma (CSCC), according to “Intralesional Cemiplimab for Patients With Early-Stage Cutaneous Squamous Cell Carcinoma: Results From a Phase 1 Pilot Study Expansion Cohort,” a poster by Michael Migden, MD, et al presented as part of the “Best of the Best at Maui Derm” late breakers session at Maui Derm Hawaii 2026.

In the Phase 1 expansion cohorts, visual objective response rates ranged from 66.7% to 75.0% by Week 7, with responses maintained through Week 13. Importantly, pathologic complete response (pCR) rates reached 58.3% in Cohort A and 66.7% in Cohort B following planned surgical excision.

Safety outcomes were favorable, with no grade 3 or higher treatment-emergent adverse events, no treatment discontinuations, and no deaths. The most common adverse events were mild and included injection-site reactions and transient dermatologic findings.

“Low-dose intralesional cemiplimab demonstrated promising clinical activity with an acceptable safety profile in patients with early-stage CSCC,” the authors stated, noting the unmet need for nonsurgical approaches in select patients.

While surgery remains the standard of care, the findings suggest intralesional immunotherapy may offer a potential neoadjuvant or alternative strategy for patients who decline or are not candidates for surgical intervention.

“This study is important because it asks whether we can harness the immune system locally and avoid systemic exposure,” said Jason E. Hawkes, MD. “By injecting anti–PD-1 directly into the tumor, you are seeing high pathologic complete response rates without many of the systemic adverse events we associate with intravenous therapy.”

Dr. Hawkes added that intralesional responses observed outside the injected lesion suggest broader immune activation.

“That opens the door to future studies asking whether we can delay or even avoid surgery in select patients,” he said.