Intralesional Cemiplimab: Reported High Pathologic Responses in Early-Stage CSCC

Low-dose intralesional cemiplimab in a Phase 1 pilot expansion cohort of early-stage cutaneous squamous cell carcinoma (CSCC) was reported to produce objective and pathologic responses, with surgical excision planned within the protocol.

The conference-poster summary described visual objective response rates by Week 7 (with responses maintained through Week 13) and pathologic complete response rates assessed after planned excision. With excision built into the protocol, the report presented both visual assessments and post-excision pathology, while also noting that surgery remains the standard of care and discussing intralesional immunotherapy as a potential neoadjuvant or alternative strategy for select patients.

The dataset came from a Phase 1 pilot study expansion cohort with two groups (Cohort A and Cohort B). Response evaluation included visual objective response rates by Week 7 (with responses maintained through Week 13) and pathologic complete response assessed following planned surgical excision. The poster was attributed to Michael Migden, MD, and colleagues and noted it was presented as part of the “Best of the Best at Maui Derm” late breakers session at Maui Derm Hawaii 2026.

In the reported cohorts of early-stage cutaneous squamous cell carcinoma, visual objective response rates were described as ranging from 66.7% to 75.0% by Week 7, with responses reported as maintained through Week 13. After planned surgical excision, pathologic complete response rates were reported as 58.3% in Cohort A and 66.7% in Cohort B. The presentation framed excision pathology as a confirmatory readout alongside the earlier visual assessments.

Early tolerability was described in the same report, including no grade 3 or higher treatment-emergent adverse events, no treatment discontinuations, and no deaths during the observation window presented. The most common adverse events were characterized as mild, with examples including injection-site reactions and transient dermatologic findings.

Interpretation in the report was explicitly attributed to the authors and a quoted expert, who described the findings as “promising clinical activity” with an “acceptable safety profile” in early-stage CSCC. The report relayed commentary positioning intralesional PD-1 blockade as a potential neoadjuvant or alternative strategy in scenarios where nonsurgical approaches are being considered, while still noting that surgery remains the standard of care. Separately, the quoted commentary described responses observed outside the injected lesion as suggestive of broader immune activation, highlighting the potential to harness local immune effects while avoiding systemic exposure.

Overall, the Phase 1 expansion cohort was presented as showing high reported responses alongside a limited early safety signal, as described in the poster summary.

Key Takeaways:

• Visual and pathologic responses were reported after intralesional cemiplimab in early-stage CSCC, with visual assessments reported through Week 13.
• The report described a favorable early tolerability signal, including no grade 3 or higher treatment-emergent adverse events, no discontinuations, and no deaths in the presented dataset.
• Authors and commentators discussed potential relevance to surgical strategy and described observations beyond injected lesions as suggestive of broader immune activation.