Zhao, Shilin

Abstract Anti–PD-1 therapy has improved clinical outcomes in advanced melanoma, but most patients experience intrinsic resistance. Responding patients can develop acquired resistance to anti–PD-1. We retrospectively reviewed 488 patients treated with anti–PD-1 from three academic centers and identified 36 patients with acquired resistance, defined as disease progression following objective response. The incidence, timing, disease sites, post-progression survival (PPS), and outcomes were evaluated descriptively. The acquired resistance cohort consisted of 67% with more than 1 feature of poor prognosis (stage M1c, elevated LDH, or brain metastasis), and 67% had previously received ipilimumab. Partial and complete responses were achieved in 89% (n = 32) and 11% (n = 4) of patients, respectively, and median time to resistance (progression-free survival; PFS) was 11.1 months (range 4.3–32.8 months). Most progression was isolated (78% of patients, n = 28) and occurred while receiving therapy (78%, n = 28). The median PPS was 12.8 months (range 0.1–51.8 months), and the median overall survival was 33.7 months. Among isolated progressors, 15 received localized therapy (12 with surgery, 3 with radiation). Patients with isolated versus systemic progression exhibited a trend for improved PPS (P = 0.081), and patients with an initial PFS ≥ 15 months showed significant PPS improvement (P = 0.036). Two patients experienced subsequent responses to anti–PD-1 resumption. In conclusion, acquired resistance to anti–PD-1 was frequently associated with excellent clinical outcomes and often presented as isolated progression amenable to localized therapy (surgery or radiation) or systemic progression sensitive to therapy resumption. Cancer Immunol Res; 5(5); 357–62. ©2017 AACR.

Abstract Patients with metastatic melanoma whose disease progresses on ipilimumab can clearly derive benefit from subsequent anti–programmed death-1 (PD-1). However, patients experience heterogeneous outcomes with ipilimumab, including rapid or delayed progression, and it is unclear whether patterns of ipilimumab progression influence subsequent clinical responses to anti–PD-1. We retrospectively reviewed data from 116 patients with metastatic melanoma who progressed on ipilimumab and were subsequently treated with pembrolizumab. The study objectives were to determine whether progression-free survival (PFS) with ipilimumab was associated with PFS, objective response rate (ORR), and clinical benefit rate (CBR; ORR + stable disease) with pembrolizumab. Patients with PFS ≥90 days after treatment with ipilimumab generally had superior outcomes with subsequent pembrolizumab treatment compared with patients with PFS <90 days (ORR, 49% vs. 35%, P = 0.12; CBR, 66% vs. 46%, P = 0.03). Patients with prolonged ipilimumab benefit (PFS ≥ 180 days) had excellent outcomes with pembrolizumab compared with rapid progressors (PFS < 45 days; ORR, 55% vs. 25%; CBR, 80% vs. 25%; median PFS, 249 vs. 50 days). Using logistic regression models, PFS with ipilimumab was independently correlated with response to pembrolizumab (odds ratio, 1.22; 95% CI, 1.02–1.51). This study shows that prolonged PFS with ipilimumab predicts excellent outcomes with subsequent pembrolizumab treatment, offering valuable prognostic information for clinicians. Cancer Immunol Res; 4(7); 569–73. ©2016 AACR.