Linavonkibart and pembrolizumab in immune checkpoint blockade-resistant advanced solid tumors: a phase 1 trial

Although immune checkpoint inhibitor therapies have revolutionized oncology, many cancers are unresponsive or develop resistance that involves transforming growth factor-β1 (TGFβ1). This multicenter, open-label, phase 1 study (DRAGON trial, SRK-181-001) evaluated safety, pharmacokinetics, pharmacodynamics, predictive biomarkers and efficacy of linavonkibart, a first-in-class fully human selective anti-latent TGFβ1 antibody with anti-programmed cell death protein 1 (PD-1) therapy. The DRAGON trial was divided into three treatment parts: part A1 (dose-escalation cohorts with single-agent linavonkibart), part A2 (dose-escalation cohorts with the combination treatment of linavonkibart and pembrolizumab) and part B (dose-expansion cohorts with the combination treatment). The primary objective of the study was to determine the safety and tolerability of linavonkibart alone and in combination with pembrolizumab. Secondary objectives included evaluation of linavonkibart pharmacokinetics for each treatment paradigm, assessment of anti-linavonkibart antibody development (parts A and B) and measurement of antitumor activity (part B) after treatment. All primary and secondary objectives were met in the study. Overall, linavonkibart had a manageable safety profile, and combined therapy with pembrolizumab was generally consistent with that of pembrolizumab monotherapy. Dermatological reactions were the only additional risk identified. Neither cytokine release syndrome nor infusion interruption was observed in any patient enrolled in DRAGON. In part A (n = 34), no dose-limiting toxicities or grade 4 or 5 treatment-related adverse events occurred (linavonkibart; ≤3,000 mg once every 3 weeks (Q3W) and 2,000 mg once every 2 weeks (Q2W)). In part B (n = 78), patients progressing on prior anti-PD-1 therapy received linavonkibart (1,500 mg Q3W/1,000 mg Q2W) with pembrolizumab (200 mg Q3W). This combination demonstrated confirmed objective response rates of 20.0%, 18.2%, 9.1% and 9.1% in anti-PD-1-resistant patients with clear cell renal cell cancer (ccRCC), melanoma, head and neck squamous cell cancer and urothelial cancer, respectively. Biomarker data provide proof of mechanism and a potential ccRCC patient selection strategy. ClinicalTrials.gov identifier: NCT04291079 .