Trastuzumab deruxtecan (T-DXd; DS-8201) in patients with HER2-mutated metastatic non-small cell lung cancer (NSCLC): Interim results of DESTINY-Lung01.

9504 Background: T-DXd is an antibody-drug conjugate composed of an anti-HER2 antibody, cleavable tetrapeptide-based linker, and topoisomerase I inhibitor payload. In a phase I trial, patients (pts) with HER2-mutated NSCLC who received T-DXd had a confirmed objective response rate (ORR) of 72.7% (8/11) (Tsurutani et al, WCLC 2018). DESTINY-Lung01 (NCT03505710) is an ongoing, multicenter, phase II study of T-DXd in pts with non-squamous NSCLC overexpressing HER2 or containing a HER2-activating mutation. We report data for the cohort with HER2 mutations after a median follow-up of 8.0 mo (range, 1.4-14.2 mo). Methods: Pts were treated with T-DXd 6.4 mg/kg every 3 weeks. The primary endpoint was confirmed ORR (complete response [CR] + partial response [PR]) by ICR. Additional endpoints were disease control rate (DCR; CR + PR + stable disease), duration of response (DOR), progression-free survival (PFS), and safety. Results: At data cutoff (25 Nov 2019), 42 pts (64.3% female) had received T-DXd. Median age was 63.0 years (range, 34-83 years; < 65 y, 59.5%); 45.2% had central nervous system metastases; ECOG performance status was 0 in 23.8% of pts and 1 in 76.2%. HER2 mutations were predominantly in the kinase domain (90.5%). Most pts (90.5%) had prior platinum-based chemotherapy and 54.8% had anti–PD-1 or –PD-L1 treatment; median number of prior treatment lines was 2 (range, 1-6). Median treatment duration was 7.75 mo (range, 0.7-14.3 mo); 45.2% of pts remained on treatment. Confirmed ORR by ICR among the 42 pts was 61.9% (95% CI, 45.6%-76.4%); median DOR was not reached at data cutoff; 16 of 26 responders remained on treatment at data cutoff; DCR was 90.5% (95% CI, 77.4%-97.3%); estimated median PFS was 14.0 mo (95% CI, 6.4-14.0 mo). All pts (42/42) had treatment-emergent adverse events (TEAEs); 64.3% were grade ≥ 3 (52.4% drug-related), including decreased neutrophil count (26.2%) and anemia (16.7%). There were 5 cases (11.9%) of drug-related interstitial lung disease (ILD) as adjudicated by an independent committee (all grade 2, no grade ≥ 3) and 1 case of grade 1 ILD is pending adjudication. TEAEs led to dose interruption in 25 pts (59.5%), dose reduction in 16 pts (38.1%), and treatment discontinuation in 10 pts (23.8%). Conclusions: T-DXd demonstrated promising clinical activity with high ORR and durable responses in pts with HER2-mutated NSCLC. The safety profile was generally consistent with previously reported studies. Clinical trial information: NCT03505710 .