Melanoma brain metastases that progress on BRAF-MEK inhibitors demonstrate resistance to ipilimumab-nivolumab that is associated with the Innate PD-1 Resistance Signature (IPRES).

Background: Melanoma brain metastases (MBMs) are a challenging clinical problem with high morbidity and mortality. Although first-line dabrafenib-trametinib and ipilimumab-nivolumab have similar intracranial response rates (50%-55%), central nervous system (CNS) resistance to BRAF-MEK inhibitors (BRAF-MEKi) usually occurs around 6 months, and durable responses are only seen with combination immunotherapy. We sought to investigate the utility of ipilimumab-nivolumab after MBM progression on BRAF-MEKi and identify mechanisms of resistance.
Methods: Patients who received first-line ipilimumab-nivolumab for MBMs or second/third line ipilimumab-nivolumab for intracranial metastases with BRAF ^V600 mutations with prior progression on BRAF-MEKi and MRI brain staging from March 1, 2015 to June 30, 2018 were included. Modified intracranial RECIST was used to assess response. Formalin-fixed paraffin-embedded samples of BRAF ^V600 mutant MBMs that were naïve to systemic treatment (n=18) or excised after progression on BRAF-MEKi (n=14) underwent whole transcriptome sequencing. Comparative analyses of MBMs naïve to systemic treatment versus BRAF-MEKi progression were performed.
Results: Twenty-five and 30 patients who received first and second/third line ipilimumab-nivolumab, were included respectively. Median sum of MBM diameters was 13 and 20.5 mm for the first and second/third line ipilimumab-nivolumab groups, respectively. Intracranial response rate was 75.0% (12/16), and median progression-free survival (PFS) was 41.6 months for first-line ipilimumab-nivolumab. Efficacy of second/third line ipilimumab-nivolumab after BRAF-MEKi progression was poor with an intracranial response rate of 4.8% (1/21) and median PFS of 1.3 months. Given the poor activity of ipilimumab-nivolumab after BRAF-MEKi MBM progression, we performed whole transcriptome sequencing to identify mechanisms of drug resistance. We identified a set of 178 differentially expressed genes (DEGs) between naïve and MBMs with progression on BRAF-MEKi treatment (p value <0.05, false discovery rate (FDR) <0.1). No distinct pathways were identified from gene set enrichment analyses using Kyoto Encyclopedia of Genes and Genomes, Gene Ontogeny or Hallmark libraries; however, enrichment of DEG from the Innate Anti-PD1 Resistance Signature (IPRES) was identified (p value=0.007, FDR=0.03).
Conclusions: Second-line ipilimumab-nivolumab for MBMs after BRAF-MEKi progression has poor activity. MBMs that are resistant to BRAF-MEKi that also conferred resistance to second-line ipilimumab-nivolumab showed enrichment of the IPRES gene signature.
Competing Interests: Competing interests: PKHL has received honoraria (Bristol-Myers Squibb, Pfizer) and support for meeting attendance (Merck Sharp and Dohme). DKe has received honoraria (Merck Sharp and Dohme, and Bristol Myers Squibb), support for meeting attendance (MSD) and fees for advisory board (Novartis and Merck). PB has received honoraria (Novartis) and received support for meeting attendance (Merck Sharp and Dohme). DKo has received support for meeting attendance (Merck and Pfizer). PS has received grants (Bristol-Myers Squibb, Roche/Genentech, Allergan, Compugen, Beigene and Crispr Therapeutics), support for meeting attendance (Bristol-Myers Squibb, Roche/Genentech and Astra Zeneca) and advisory board (Bristol-Myers Squibb). BS has received honoraria and fees for advisory board (Bristol-Myers Squibb, Merck Sharp and Dohme, AstraZeneca, Pfizer, Roche/Genentech, Amgen, Lilly, Amgen and Sanofi/Regeneron) SS has received grants (Novartis, Advanced Accelerator Applications, AstraZeneca, Merck Sharp and Dohme, Amgen and Genentech) and personal fees donated to the institution (AstraZeneca, Merck Sharp and Dohme, Bristol Myers Squibb and AstraZeneca) outside the submitted work. GAM has been a consultant or advisor (Provectus), received research funding from (Pfizer, Celgene, and Ventana) and has had travel accommodation and expenses paid (Roche and Novartis). No stated competing interests: BF, LS, AL, RM, KS, AW, CA, BL, RJY, AI, HAY, IAV, KD, KES and TP.
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