Phase 2 trial of avelumab in combination with gemcitabine in advanced leiomyosarcoma as a second-line treatment (EAGLES, Korean Cancer Study Group UN18-09).

Background: In this single-arm, multicenter, phase 2 trial, the authors evaluated the efficacy and safety of avelumab plus gemcitabine in patients with leiomyosarcoma (LMS) who failed on first-line chemotherapy.

Methods: Patients with advanced LMS received avelumab 10 mg/kg on days 1 and 15 (for up to 24 months) plus gemcitabine 1000 mg/m² on days 1, 8, and 15 of a 28-day cycle until they developed disease progression or intolerable toxicity. The primary end point was the objective response rate (ORR).

Results: In total, 38 patients were enrolled. Of these, 35 patients were evaluable, and the ORR was 20% (95% confidence interval; [CI], 8%-37%). The disease control rate was 71%, and the median duration of response was 21.8 months (range, 7.6 to ≥43.3 months). The median progression free-survival was 5.6 months (95% CI, 4.5-6.8 months), and the median overall survival was 27.5 months (95% CI, 20.4-34.6 months). Grade 3-4 adverse events occurred in 70% of patients, of which neutropenia was the most common (54%). Immune-mediated adverse events occurred in five patients (14%; hypothyroidism, n = 3; hepatitis, n = 2). Patients who had a higher density of tumor-infiltrating lymphocytes (greater than the median) exhibited better ORR (35% vs. 8%; p = .104), progression-free survival (median, 7.3 vs. 3.3 months; p = .024), and overall survival (median, not reached vs. 21.5 months; p = .027).

Conclusions: The combination of avelumab and gemcitabine demonstrated promising efficacy and manageable safety in patients with advanced LMS who progressed on first-line therapy. Tumor-infiltrating lymphocyte density may be an important factor in predicting the response to combining immunotherapy with chemotherapy.