ISA101 and nivolumab for HPV-16 + cancer: Updated clinical efficacy and immune correlates of response

Background The combination of ISA101, a human papilloma virus (HPV) 16 peptide vaccine, and nivolumab showed a promising response rate of 33% in patients with incurable HPV-16 + cancer. Here we report long-term clinical outcomes and immune correlates of response. Methods Patients with advanced HPV-16 + cancer and less than two prior regimens for recurrence were enrolled to receive ISA101 (100 μg/peptide) on days 1, 22, and 50 and nivolumab 3 mg/kg every 2 weeks beginning day 8 for up to 1 year. Baseline tumor samples were stained with multiplex immunofluorescence for programmed death-ligand 1 (PD-L1), programmed cell death protein-1 (PD-1), CD3, CD8, CD68, and pan-cytokeratin in a single panel and scanned with the Vectra 3.0 multispectral microscope. Whole transcriptome analysis of baseline tumors was performed with Affymetrix Clariom D arrays. Differential gene expression analysis was performed on responders versus non-responders. Results Twenty-four patients were followed for a median of 46.5 months (95% CI, 46.0 months to not reached (NR)). The median duration of response was 11.2 months (95% CI, 8.51 months to NR); three out of eight (38%) patients with objective response were without progression at 3 years. The median and 3-year overall survival were 15.3 months (95% CI, 10.6 months to 27.2 months) and 12.5% (95% CI, 4.3% to 36%), respectively. The scores for activated T cells ((CD3 + PD-1 +)+(CD3 + CD8 + PD-1 +)), activated cytotoxic T cells (CD3 + CD8 + PD-1 +), and total macrophage ((CD68 + PD-L1 -)+(CD68 + PD-L1 +)) in tumor were directly correlated with clinical response (p<0.05) and depth of response with the two complete response patients having the highest degree of CD8 + T cells. Gene expression analysis revealed differential regulation of 357 genes (≥1.25 fold) in non-responders versus responders (p<0.05). Higher expression of immune response, inflammatory response and interferon-signaling pathway genes were correlated with clinical response (p<0.05). Conclusions Efficacy of ISA101 and nivolumab remains promising in long-term follow-up. Increased infiltration by PD-1 + T cells and macrophages was predictive of response. Enrichment in gene sets associated with interferon-γresponse and immune infiltration strongly predicted response to therapy. A randomized trial is ongoing to test this strategy and to further explore correlates of immune response with combined nivolumab and ISA101, versus nivolumab alone. Trial registration number NCT02426892.