Avelumab plus axitinib in patients with advanced gastrointestinal stromal tumor

Treatment options for patients with advanced gastrointestinal stromal tumor (GIST) after failure of standard therapies with tyrosine kinase inhibitor (TKI) remain very limited. As vascular endothelial growth factor (VEGF) inhibitors are considered to have immunomodulatory effects, we hypothesized that the combination of VEGF and PD-L1 inhibitors may have a synergistic effect and enhance the efficacy of both therapies.

AXAGIST was a phase II trial evaluating the efficacy and safety of avelumab 10 mg/kg iv Q2W in combination with axitinib 5 mg po BID in patients with unresectable/metastatic GIST after failure of standard therapy. The primary endpoint was progression-free survival (PFS) at 3 months based on RECIST 1.1 criteria. Secondary endpoints included PFS, overall survival (OS), overall response rate, and safety.

Of the 58 patients enrolled, 56 patients were evaluable for safety and efficacy. Median age was 60 years (range 18-80), and 30 patients (53.4 %) had received three prior lines of TKIs. Median follow-up was 27.4 months. The best response was partial response in 5 patients (8.9 %), stable disease in 34 patients (60.7 %), and progressive disease in 17 patients (30.4 %). Among patients with partial response, the median duration of response was 18.5 months (95 %CI, 18.3-NA). The PFS rate at 3 months was 57.1 %. Median PFS and OS were 4.6 months (95 %CI, 2.9-6.4) and 14.2 months (95 %CI, 9.2-26.3), respectively. Adverse events occurred in 94.6 % of patients, while 30.4 % experienced grade 3 or higher adverse events.

The results of the largest trial on the combination of targeted therapy and immunotherapy in pretreated GIST show the promising efficacy of this novel therapeutic approach in a subset of patients.