Abstract CT170: KEYNOTE-629: Phase II study of pembrolizumab for recurrent/metastatic or locally advanced unresectable cutaneous squamous cell carcinoma

Background: Findings from Phase I and II clinical trials suggest that treatment with an anti-programmed death 1 (PD-1) antibody is well tolerated and provides durable antitumor activity in patients with local/regionally advanced or metastatic cutaneous squamous cell carcinoma (cSCC). Encouraging efficacy and safety findings have also been reported from an expansion cohort in the phase 1 KEYNOTE-012 trial with the PD-1 inhibitor pembrolizumab. KEYNOTE-012 demonstrated that pembrolizumab 200 mg administered once every 3 weeks was well tolerated and yielded a clinically meaningful overall response rate with evidence of durable responses in patients with recurrent and/or metastatic head and neck cSCC. To test the clinical activity of pembrolizumab, the open-label, single-arm, phase 2 KEYNOTE-629 trial (NCT03284424) will be carried out in patients with locally advanced, unresectable, and recurrent or metastatic cSCC. Trial design: Patients will receive intravenous pembrolizumab 200 mg every 3 weeks for up to 35 infusions (≤24 months) or until protocol-specified treatment discontinuation. Treatment will not be stratified in this study. Eligibility criteria include age ≥18 years; locally advanced cSCC that is ineligible for surgical resection or radiotherapy (RT) or that previously underwent RT to the index site or systemic therapy for curative intent; presence of measurable disease by Response Evaluation Criteria in Solid Tumors (RECIST) v1.1; and Eastern Cooperative Oncology Group performance status 0 or 1. Treatment will be discontinued for progressive disease, unacceptable toxicity, intercurrent illness preventing study treatment administration, investigator’s decision, patient withdrawal of consent, pregnancy, or cessation for administrative reasons. Response will be assessed by computed tomography or magnetic resonance imaging 6 weeks after treatment initiation, every 6 weeks through year 1, then every 9 weeks thereafter or more frequently if clinically indicted. After a patient experiences disease progression or starts new anticancer therapy, the patient will be followed up and contacted every 12 weeks until death, consent withdrawal, or study end, whichever occurs first. Safety will be monitored throughout the study treatment and for 30 days after treatment end and for 90 days for serious adverse events after the end of treatment. The primary end point is objective response rate (RECIST v1.1). Secondary end points include duration of response, disease con