Activity And Safety Of Geptanolimab (Gb226) For Patients With Unresectable, Recurrent, Or Metastatic Alveolar Soft Part Sarcoma: A Phase Ii, Single-Arm Study

Purpose: Patients with alveolar soft part sarcoma (ASPS) are rare and have few treatment options. We assessed the activity of geptanolimab (GB226), a fully humanized programmed cell death protein 1 antibody, for patients with unresectable, recurrent, or metastatic ASPS.Patients and Methods: We conducted this multicenter, single-arm, phase II study (Gxplore-005, NCT03623581) in patients aged 18-75 years who had unresectable, recurrent, or metastatic ASPS at 11 sites in China. Patients received intravenous geptanolimab (3 mg/kg) every 2 weeks until disease progression or unacceptable toxicity. The primary endpoint was objective response rate assessed by independent review committee (IRC) per RECIST 1.1 in the full analysis set population.Results: Between September 6, 2018 and March 6, 2019, we enrolled and treated 37 patients with 23 (62.2%) having received prior systemic treatment. Fourteen [37.8%; 95% confidence interval (CI), 22.5-55.2] of 37 patients had an objective response assessed by IRC with a 6-month duration of response rate of 91.7%. Median progression-free survival was 6.9 months (95% CI, 5.0-not reached) and disease control was achieved in 32 (86.5%; 95% CI, 71.2-95.5) patients. Three of 37 patients reported grade 3 treatment-related adverse events (TRAEs), including anemia, hypophysitis, and proteinuria [one each (2.7%)]. No grade 4 TRAEs were observed. Two (5.4%) patients discontinued treatment due to TRAEs (one with hypophysitis and one with Mobitz type I atrioventricular block). The baseline percentage of CD4(+) T cells was adversely associated with patient response (P = 0.031).Conclusions: Geptanolimab has clinically meaningful activity and a manageable safety profile in unresectable, recurrent, or metastatic ASPS.