A Phase 1a/1b Multicenter, Open-label Dose Escalation/Expansion Study to Evaluate the Safety, Tolerability, Pharmacokinetics, and Preliminary Evidence of Antitumor Activity of PLN-101095 as Monotherapy and in Combination With Pembrolizumab in Adult Participants With Advanced or Metastatic Solid Tumors Who Have Disease Progression While on Pembrolizumab

This is a Phase 1a/1b, dose-escalation/expansion, consecutive-cohort, open-label study to evaluate the safety, tolerability, PK, PD, and preliminary evidence of antitumor activity of PLN-101095 in combination with pembrolizumab (the study treatment regimen) in adult participants with advanced or metastatic solid tumors for which pembrolizumab is indicated but have documented disease progression (refractory [primary resistance]) or relapsed [secondary resistance]) after at least 3 months from the start of treatment with pembrolizumab.

The study will consist of 2 main parts:

• Part 1: Consecutive dose-escalation cohorts using a Bayesian optimal interval (BOIN) dose escalation design
• Part 2: Dose-expansion cohorts using Simon's 2-stage design