MONETTE: A Randomized Phase II Study of Ceralasertib plus Durvalumab or Ceralasertib Monotherapy in Patients with Advanced Melanoma Resistant to PD-(L)1 Inhibition

PURPOSE: Data suggest that ceralasertib, a potent and selective oral inhibitor of the ataxia-telangiectasia and Rad3-related (ATR) DNA damage response kinase, may overcome resistance to prior immunotherapy. PATIENTS AND METHODS: In this phase II study, patients with unresectable or metastatic melanoma of cutaneous, acral, or mucosal subtype and confirmed progression during anti-PD-(L)1 therapy with or without anti-CTLA-4 were randomized 2:1 to ceralasertib 240 mg twice daily on days 1 to 7 and then durvalumab 1,500 mg intravenously on day 8, every 28 days or ceralasertib 240 mg twice daily on days 1 to 7, every 28 days. The primary endpoint was objective response rate (ORR). Key secondary endpoints included progression-free survival (PFS), overall survival (OS), and safety. Exploratory analyses of baseline (tumor and circulating) and on-treatment (circulating only) biomarkers were conducted. RESULTS: ORR was 9.3% [95% confidence interval (CI), 4.3-16.9] for ceralasertib plus durvalumab (below the prespecified minimum threshold) and 5.8% (95% CI, 1.2-15.9) for ceralasertib monotherapy; median PFS was 2.0 months (95% CI, 1.9-3.5) versus 1.9 months [95% CI, 1.9-3.1; hazard ratio (HR), 0.80; 95% CI, 0.54-1.18]; and median OS was 16.0 months [95% CI, 10.5-not calculated (NC)] versus 12.3 months (95% CI, 9.5-NC; HR, 0.81; 95% CI, 0.49-1.37). Both regimens were well tolerated. Exploratory analyses indicated a possible link between higher baseline pretreatment tumor CD8+ T-cell counts and improved OS across both arms and suggested that ceralasertib treatment may induce transient, cyclical changes in circulating CD14+ monocytes and GDF-15 plasma levels. CONCLUSIONS: Both ceralasertib plus durvalumab and ceralasertib monotherapy demonstrated low response rates in anti-PD-(L)1-resistant advanced melanoma.