Study to Assess the Safety, Tolerability, and Blood Concentration of PMC-309

PMC-309 will be administered intravenously.

Both PMC-309 and pembrolizumab will be administered intravenously. At the time of the combination therapy (Week 1/Day 1 of each cycle), participants will be dosed with pembrolizumab first, administered over 0.5 hours (± 10 minutes). Following an interval of 1 hour (± 15 minutes), participants will be dosed with PMC-309 administered over 1 hour (± 0.5 hours), after which participants will be observed for a period of 1.5 hours post administration.

"Phase 1b will enroll participants with advanced or metastatic tumor types into 1 of 2 cohorts:~* Cohort A: PMC-309 monotherapy therapy~ \- PMC-309 dosing will be at the preliminary RP2D, as identified in Phase 1a: Part A~* Cohort B: PMC-309 plus pembrolizumab combination therapy - PMC-309 dosing will be as identified in Phase 1a: Part B in combination with 200 mg pembrolizumab"