A Study of SNS-101 (Anti VISTA) Monotherapy and in Combination With Cemiplimab in Patients With Advanced Solid Tumors

This is a first-in-human, Phase 1/2 open-label, multi-center, dose escalation and expansion study to evaluate the safety, tolerability, pharmacokinetics, pharmacodynamics, and efficacy of SNS-101, a novel anti VISTA IgG1 monoclonal antibody as monotherapy or in combination with cemiplimab in patients with advanced solid tumors. The Phase 1 portion is conducted in two parts; A and B: Phase 2 is planned in Part C. * Part A: Phase 1 Monotherapy Dose Escalation and Dose Expansion (SNS-101 alone) * Part B: Phase 1 Combination Dose Escalation and Dose Expansion (SNS-101 in combination with cemiplimab) Once the dose escalation portion was complete, enrollment expanded to targeted tumor types: * Approximately 10 patients with colorectal cancer (CRC) will be enrolled in the Monotherapy Dose Expansion. o Additional tumor types and doses may be considered upon consultation with the Sponsor. * Approximately 50 patients with CRC, head and neck cancer (H\&N), melanoma, and non-small cell lung cancer (NSCLC) will be enrolled in the Combination Dose Expansion. * A minimum of 8 and a maximum of 10 CRC patients will be enrolled in the Combination Dose Expansion. * Additional tumor types and doses may be considered upon consultation with the Sponsor. The Phase 2, Part C Cohort Expansion will further evaluate efficacy at the selected dose(s.). Following completion of the Phase 1 portions of the study, the sponsor decided not to initiate the Phase 2 portion. No participants were enrolled in the planned Phase 2 Part C.