The features and management of acquired resistance to PD1-based therapy in metastatic melanoma.

BACKGROUND: Anti-PD-1 therapy (PD1) either alone or with anti-CTLA-4 (CTLA4), has high initial response rates, however 20% of patients (pts) with complete response (CR) and 30% with partial response (PR) within 12 months of treatment experience subsequent disease progression by 6 years. The nature and optimal management of this acquired resistance (AR) remains unknown. METHODS: Pts from 16 centres who responded to PD1-based therapy and who later progressed were examined. Demographics, disease characteristics and subsequent treatments were evaluated. RESULTS: 299 melanoma pts were identified, median age 64y, 44% BRAFV600m. 172 (58%) received PD1 alone, 114 (38%) PD1/CTLA4 and 13 (4%) PD1 and an investigational drug. 90 (30%) pts had CR, 209 (70%) PR. Median time to AR was 12.6 mo (95% CI, 11.3, 14.2). Most (N = 193, 65%) progressed in a single organ site, and in a solitary lesion (N = 151, 51%). The most frequent sites were lymph nodes (38%) and brain (25%). Management at AR included systemic therapy (ST, 45%), local therapy (LT) +ST (31%), LT alone (21%), or observation (3%). There was no statistical difference in PFS2 or OS based on management, however, PFS2 was numerically superior for pts treated with ST alone who progressed off PD1 therapy than those who progressed on PD1 (2-year PFS2 42% versus 25%, p = 0.249). mOS from AR was 38.0 months (95% CI, 29.5-NR); longer in single-site versus multi-site progression (2-year OS 70% vs 54%, p < 0·001). CONCLUSIONS: Acquired resistance to PD1 therapy in melanoma is largely oligometastatic, and pts may have a favorable survival outcome following salvage treatment.

Re-induction ipilimumab following acquired resistance to combination ipilimumab and anti-PD-1 therapy.

PURPOSE: Combination immunotherapy with nivolumab and ipilimumab has a high initial response rate in advanced melanoma; however, up to 55% of patients later progress. The efficacy and safety of ipilimumab re-induction in the setting of acquired resistance (AR) to combination immunotherapy is unknown. METHODS: Patients with advanced melanoma who initially achieved a complete response, partial response or sustained stable disease to induction combination immunotherapy then progressed and were reinduced with ipilimumab (alone or in combination with anti-PD-1) and were analysed retrospectively. Demographics, disease characteristics, efficacy and toxicity were examined. RESULTS: Forty-seven patients were identified from 12 centres. The response rate to reinduction therapy was 12/47 (26%), and disease control rate was 21/47 (45%). Responses appeared more frequent in patients who developed AR after ceasing induction immunotherapy (30% vs. 18%, P = 0.655). Time to AR was 11 months (95% confidence interval [CI], 8-15 months). After a median follow-up of 16 months (95% CI, 10-25 months), responders to reinduction had a median progression-free survival of 14 months (95% CI, 13, NR months), and in the whole cohort, the median overall survival from reinduction was 17 months (95% CI, 12-NR months). Twenty-seven (58%) immune-related adverse events (irAEs) were reported; 18 (38%) were grade 3/4, and in 11 of 27 (40%), the same irAE observed during induction therapy recurred. CONCLUSIONS: Reinduction with ipilimumab ± anti-PD-1 has modest clinical activity. Clinicians should be attentive to the risk of irAEs, including recurrence of irAEs that occurred during induction therapy. Future studies are necessary to determine best management after resistance to combination immunotherapy.