Condition: High-grade Serous Ovarian Carcinoma

The primary objective is to evaluate in participants with high-grade serous ovarian cancer (HGSOC), whether the reduction from baseline in circulating tumor DNA (ctDNA) at Cycle 3 (ΔctDNA) is larger in participants receiving MK-4830 + pembrolizumab in combination with standard of care (SOC) therapy than in those receiving pembrolizumab + SOC therapy.