LBA60 ZENITH20, a multinational, multi-cohort phase II study of poziotinib in NSCLC patients with EGFR or HER2 exon 20 insertion mutations

Abstract

Treatment of non-small cell lung cancer (NSCLC) with EGFR or HER2 exon 20 mutations is a serious unmet medical need. We are evaluating the efficacy and safety of poziotinib, a potent EGFR and HER2 exon 20 tyrosine kinase inhibitor (TKI), in a large, prospective multi-cohort study (N=603). Here, we report results from a cohort of previously treated patients with advanced NSCLC exon 20 insertion mutations (ZENITH20-2 N=90). Patients enrolled in ZENITH20-2 had HER2 exon 20 insertion mutations per a CLIA certified (or equivalent) sequencing test. Poziotinib (16 mg) was administered orally QD, allowing dose interruptions/reductions for toxicity if needed. The primary endpoint was objective response rate (ORR), evaluated centrally by an independent image review committee using RECIST 1.1 with a 95% CI pre-specified lower bound of 17%. Secondary endpoints included disease control rate, duration of response, progression-free survival, and safety. In ZENITH20-2, 90 patients were enrolled with a median age of 60 years; 64% females, 66% non-smokers, 78% Caucasians, and 16% had concurrent clinically stable brain metastases at entry. Median number of prior therapies was 2 (range: 1-6), with 98% of patients having prior chemo/platinum-based therapy; 67% immunotherapy, including checkpoint inhibitors; and 28% HER2 therapy. The most common treatment-related Grade ≥3 AEs were rash (30%), diarrhea (26%), and mucosal inflammation (14%). ORR in 74 evaluable patients was 35.1% (95% CI: 24.4 – 47.1%) and 27.8% (95% CI: 18.9 – 38.2%) in all 90 patients (As-Treated Population). The 95% CI lower bound exceeded the protocol-specified threshold of 17%. Median DoR was 5.1 months (range: 1-12.3+ months) with 3 patients continuing on treatment. DCR was 70% and median PFS was 5.5 months (range: 0.03-13.1+ months). Responses were observed in most subgroups. Specifically, ORR was 38.7% in 31 patients with 3+ lines of therapy and 28.6% in 14 patients with CNS metastasis. ZENITH20-2 met its ORR primary efficacy endpoint with durable responses and presented a manageable safety profile, typical of 2nd generation TKIs. Additional cohorts are enrolling to explore alternative dose levels and BID dosing.