Buparlisib and Paclitaxel in Patients with Head and Neck Squamous Cell Carcinoma: Immunogenomic Biomarkers of Efficacy from the BERIL-1 Study

Abstract

Background: BERIL-1 was a randomized phase 2 study that studied paclitaxel with either buparlisib, a pan-class I PIK3 inhibitor, or placebo in patients with recurrent or metastatic (R/M) head and neck squamous cell cancer (HNSCC). Considering the therapeutic paradigm shift with immune checkpoint inhibitors (ICIs) now approved in the first-line setting, we present an updated immunogenomic analysis of patients enrolled in BERIL-1, including patients with immune-infiltrated tumors.

Objective: The objective of this study was to identify biomarkers predictive of treatment efficacy in the context of the post-ICI therapeutic landscape.

Patients and methods: Genomic analyses were performed at baseline on tumor and/or plasma circulating DNA (ctDNA) samples, and immunohistochemistry (IHC) studies, including immune infiltration [tumor-infiltrating lymphocytes (TILs) and CD8 expression], were performed on tumor samples. Immunogenomic biomarkers were correlated to overall survival (OS).

Results: Among 158 patients enrolled in BERIL-1, either tumor (53.2%; n = 84) or ctDNA samples (70.8%; n = 112) were available in 85.4% (n = 135). The most commonly mutated genes were TP53 (57.0%), NOTCH1 (23.7%), and PIK3CA (22.2%). In the IHC studies, 98.6% (n = 68/69) of patients were TILs positive in the buparlisib arm versus 94.4% (n = 68/72) in the placebo arm. In patients with TILs-positive tumors, enrichment for clinical benefit on the buparlisib arm was seen in those with PIK3 pathway activation [25.0% (n = 17/68)] with a hazard ratio (HR) for death of 0.43 [95% confidence interval (CI) 0.21-0.87, p = 0.016]. Similarly, improved OS was seen in patients on the buparlisib arm and NOTCH pathway activation [20.5% (n = 14/68)] with a HR for death of 0.40 (95% CI 0.18-0.90, p = 0.022). Both associations were absent in the placebo group. TP53 and tumor mutational burden (TMB) did not correlate with OS in the buparlisib or placebo arms.

Conclusions: In this immunogenomic analysis of BERIL-1, improved HRs for OS were seen in patients with tumor immune infiltration and selected oncogenic alterations, including PIK3 and NOTCH pathway activation (NCT01852292).