Puxitatug samrotecan, a B7-H4-directed antibody-drug conjugate, produced high response rates in B7-H4-expressing recurrent or progressive endometrial cancer in the BLUESTAR phase 1/2a trial. At the 2.4 mg/kg dose level, investigators reported a confirmed objective response rate of 47.1% and a median progression-free survival of 7.2 months. In the subgroup of patients previously treated with platinum-based chemotherapy and anti-PD-1/PD-L1 therapy, B7-H4 samrotecan achieved a confirmed ORR of 60.6% with a median PFS of 7.1 months. BTD support was cited by the company as aligning with these data in a targeted population. The ADC also showed activity in heavily pretreated ovarian cancer cohorts, with a confirmed ORR of 24.4% reported at the same dose, reinforcing the broader development intent of the B7-H4 ADC platform.