A phase Ib study of the combination of naporafenib with rineterkib or trametinib in patients with advanced and metastatic KRAS- or BRAF-mutant non-small cell lung cancer

Background: Genetic alterations activating the MAPK pathway are common in non-small cell lung cancer (NSCLC). Patients with NSCLC may benefit from treatment with the pan-RAF inhibitor naporafenib (LXH254) plus the ERK1/2 inhibitor rineterkib (LTT462) or MEK1/2 inhibitor trametinib. Methods: This first-in-human phase 1b dose-escalation/dose-expansion study investigated the combinations of naporafenib (50–350 mg once daily [QD] or 300–600 mg twice daily [BID]) with rineterkib (100–300 mg QD) in patients with KRAS-/BRAF-mutant NSCLC and naporafenib (200 mg BID or 400 mg BID) with trametinib (0.5 mg QD, 1 mg QD or 1 mg QD 2 weeks on/2 weeks off) in patients with KRAS-/BRAF-mutant NSCLC and NRAS-mutant melanoma. The primary objectives were to identify the recommended dose for expansion (RDE) and evaluate tolerability and safety. Secondary objectives included antitumor activity and pharmacodynamics. Results: Overall, 216 patients were treated with naporafenib plus rineterkib (NSCLC: n = 101) or naporafenib plus trametinib (NSCLC: n = 79; melanoma: n = 36). In total, 10 of 62 (16%) patients experienced at least one dose-limiting toxicity. The RDEs were established as naporafenib 400 mg BID plus rineterkib 200 mg QD, naporafenib 200 mg BID plus trametinib 1 mg QD and naporafenib 400 mg BID plus trametinib 0.5 mg QD. The most frequent grade ≥ 3 treatment-related adverse event was increased lipase (8/101 [7.9%] patients) for naporafenib plus rineterkib and rash (22/115 [19.1%] patients) for naporafenib plus trametinib. Among patients with NSCLC, partial response was observed in three patients (one with KRAS-mutant, two with BRAF^non-V600-mutant NSCLC) treated with naporafenib plus rineterkib and two patients (both with KRAS-mutant NSCLC) treated with naporafenib plus trametinib. On-treatment median reductions in DUSP6 mRNA levels from baseline were 45.5% and 76.1% with naporafenib plus rineterkib or trametinib, respectively. Conclusions: Both naporafenib combinations had acceptable safety profiles. Antitumor activity was limited in patients with NSCLC, despite the observed on-target pharmacodynamic effect. ClinicalTrials.gov identifier: NCT02974725.