This is a two-part (Phase 2/Phase 3) study of intismeran autogene, an individualized neoantigen therapy (INT), plus pembrolizumab in participants with locally resectable advanced cutaneous squamous cell carcinoma (LA cSCC). Phase 2 has three arms intismeran autogene plus pembrolizumab given as neoadjuvant and adjuvant treatment with standard of care (SOC), standard of care (surgical resection with/without adjuvant radiation therapy (RT) only at investigator’s discretion) and pembrolizumab monotherapy given as neoadjuvant and adjuvant treatment with SOC. This phase will assess the safety and efficacy of intismeran autogene in combination with pembrolizumab as neoadjuvant and adjuvant therapy in participants with resectable LA cSCC as compared to standard of care SOC only. The primary hypothesis is that intismeran autogene plus pembrolizumab with SOC is superior to SOC only with respect to event free survival (EFS) as assessed by the investigator. Phase 3 expansion will be determined by prespecified Go-No-Go decision in which 412 additional participants will be randomized to intismeran autogene plus pembrolizumab with SOC and SOC only, without changing the inclusion/exclusion criteria for the additional enrollment or study endpoints.

As of Amendment 04, enrollment was stopped and there will be no Phase 3 expansion.