First-Line Mobocertinib Versus Platinum-Based Chemotherapy in Patients With EGFR Exon 20 Insertion-Positive Metastatic Non-Small Cell Lung Cancer in the Phase III EXCLAIM-2 Trial

PURPOSE Mobocertinib is an oral epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor that targets EGFR exon 20 insertion (ex20ins) mutations in non-small cell lung cancer (NSCLC). This open-label, phase III trial (EXCLAIM-2: ClinicalTrials.gov identifier: NCT04129502) compared mobocertinib versus platinum-based chemotherapy as first-line treatment of EGFR ex20ins+ advanced/metastatic NSCLC. Methods Patients with treatment-naive EGFR ex20ins+ locally advanced/metastatic NSCLC were randomly assigned 1:1 to mobocertinib 160 mg once daily or pemetrexed plus cisplatin or carboplatin every 3 weeks for four cycles followed by maintenance pemetrexed. The primary end point was progression-free survival (PFS) by blinded independent central review (BICR), with planned interim analysis (IA) after approximately 70% of 227 expected PFS events. Results A total of 354 patients were randomly assigned (mobocertinib: n = 179; chemotherapy: n = 175). Baseline characteristics were balanced between arms. At IA (cutoff: April 4, 2023), the median PFS per BICR was 9.6 months in each treatment arm (hazard ratio [HR], 1.04 [95% CI, 0.77 to 1.39]; P =.803). The primary end point crossed the prespecified futility boundary (HR > 1). The confirmed objective response rate (95% CI) per BICR was 32% (26 to 40) with mobocertinib versus 30% (24 to 38) with chemotherapy; the median duration of response was 12.0 versus 8.4 months. Quality-of-life assessments indicated clinically meaningful delays in time to deterioration of lung cancer symptoms, cognitive function, and constipation with mobocertinib versus chemotherapy. Grade ≥3 adverse events in >5% of patients (mobocertinib, chemotherapy) were diarrhea (20%, 1%), anemia (6%, 10%), increased lipase (6%, 0%), and decreased neutrophil count (1%, 7%). CONCLUSION The EXCLAIM-2 trial did not meet its primary end point. The efficacy of mobocertinib was not superior to platinum-based chemotherapy for first-line treatment of patients with EGFR ex20ins+ advanced/metastatic NSCLC.