Anti-PD-1 therapy yields objective clinical responses in 30–40% of advanced melanoma patients. Since most patients do not respond, predictive biomarkers to guide treatment selection are needed. We hypothesize that MHC-I/II expression is required for tumour antigen presentation and may predict anti-PD-1 therapy response. In this study, across 60 melanoma cell lines, we find bimodal expression patterns of MHC-II, while MHC-I expression was ubiquitous. A unique subset of melanomas are capable of expressing MHC-II under basal or IFNγ-stimulated conditions. Using pathway analysis, we show that MHC-II(+) cell lines demonstrate signatures of ‘PD-1 signalling', ‘allograft rejection' and ‘T-cell receptor signalling', among others. In two independent cohorts of anti-PD-1-treated melanoma patients, MHC-II positivity on tumour cells is associated with therapeutic response, progression-free and overall survival, as well as CD4+ and CD8+ tumour infiltrate. MHC-II+ tumours can be identified by melanoma-specific immunohistochemistry using commercially available antibodies for HLA-DR to improve anti-PD-1 patient selection.

EGFR-mutated NSCLC is a genetically heterogeneous disease that includes more than 200 distinct mutations. The implications of mutational subtype for both prognostic and predictive value are being increasingly understood. Although the most common EGFR mutations-exon 19 deletions or L858R mutations-predict sensitivity to EGFR tyrosine kinase inhibitors (TKIs), it is now being recognized that outcomes may be improved in patients with exon 19 deletions. Additionally, 10% of patients will have an uncommon EGFR mutation, and response to EGFR TKI therapy is highly variable depending on the mutation. Given the growing recognition of the genetic and clinical variation seen in this disease, the development of comprehensive bioinformatics-driven tools to both analyze response in uncommon mutation subtypes and inform clinical decision making will be increasingly important. Clinical trials of novel EGFR TKIs should prospectively account for the presence of uncommon mutation subtypes in study design.

Novel agents targeting immune checkpoint molecules or mutated BRAF are active therapeutic options for patients with BRAF-mutant melanoma. However, the most effective first-line treatment and the optimal sequencing of these agents have not been well characterized. To explore this, we retrospectively assessed 114 patients from 4 centers with advanced, BRAF-mutant melanoma who received anti-programmed cell death-1 (PD-1)/PD-L1 antibodies. We evaluated clinical outcomes, including objective response rate (ORR), overall survival (OS), and progression-free survival (PFS) to initial and subsequent therapies in patients that received anti-PD-1 first (n=56) versus those that received BRAF±MEK inhibitors (BRAFi) first (n=58). Median OS was similar between these groups (27.5 vs. 40.3 mo, P=0.71). Patients who progressed on anti-PD-1 during the study timeframe had worse outcomes after starting subsequent BRAFi than those who had not received prior anti-PD-1 (median PFS 5 vs. 7.4 mo, median OS 10.6 vs. 40.3 mo). Similarly, patients who previously progressed on BRAFi had seemingly inferior outcomes after starting anti-PD-1 compared with those without prior BRAFi, including ORR (25% vs. 41%), median PFS (2.8 vs. 10.6 mo) and median OS (8.2 vs. 27.6 mo). Notably, patients who benefited >6 months from BRAFi had superior ORR to subsequent anti-PD-1 compared with those with more rapid progression (<6 mo) on BRAFi (34% vs. 15%, P=0.04). We conclude that either BRAFi or anti-PD-1 may be effective regardless of treatment sequence in patients with BRAF-mutant melanoma, but clinical outcomes to front-line therapy are superior. In addition, we suggest a shared "responder phenotype" between BRAFi and anti-PD-1.

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