Background: Osi (third-generation tyrosine kinase inhibitor) is a standard frontline treatment (Tx) for advanced/metastatic EGFR-mutated NSCLC. However, tumors invariably progress after an initial response, with c-Met protein overexpression (OE) often associated with acquired resistance. Second- and third-line Tx options are limited to chemotherapy-based regimens with limited efficacy and significant toxicities. Teliso-V (ABBV-399), an anti–c-Met antibody-drug conjugate, delivers a cytotoxic payload (monomethyl auristatin E) into c-Met OE tumor cells. In a phase 1/1b study (NCT02099058) in patients (pts) with c-Met OE NSCLC, Teliso-V alone or in combination with erlotinib demonstrated an acceptable safety profile and antitumor activity. Interim safety and efficacy data from the Teliso-V + Osi cohort (arm E) of this trial are presented. Methods: Pts (≥18 yr) with metastatic EGFR-mutated, c-Met OE (by central immunohistochemistry) NSCLC who had progressed on a prior Osi regimen were eligible. Pts received Teliso-V (IV Q2W) + Osi (oral; 80 mg QD). Teliso-V was evaluated at 1.6 mg/kg and, after review of safety data, escalated to 1.9 mg/kg (safety evaluation). An expansion cohort was opened at 1.9 mg/kg for pts who had received ≤2 prior lines of systemic therapy. Pharmacokinetics (PK) were assessed throughout the study. Pts received study Tx until disease progression, unacceptable toxicity, or for up to 24 months. Results: As of 20 Dec 2021, 25 pts received Teliso-V (1.6 mg/kg, n = 7; 1.9 mg/kg, n = 18) + Osi. Median age was 60.0 yr; 14 (58%) pts were on prior Tx with Osi for > 12 mo. No dose-limiting toxicities (grade [Gr] ≥3 non-hematologic or Gr 4 hematologic Tx-related adverse events [AEs]) were reported during the safety lead-in or evaluation phases. All-Gr AEs considered possibly related to Teliso-V occurred in 22/25 (88%) pts: the most common (≥20%) were peripheral sensory neuropathy (36%), nausea, and peripheral edema (20% each); Gr ≥3 AEs (> 5%) were anemia (12%) and peripheral motor neuropathy (8%). No Gr 5 events related to Tx were reported. PK of Teliso-V + Osi was similar to single-agent Teliso-V. Efficacy data (19/25 pts) are in the table. The overall objective response rate (ORR) was 58% (67% at 1.9 mg/kg). Conclusions: Teliso-V + Osi is well tolerated with an ORR of 58% (67% at 1.9 mg/kg) in pts with c-Met OE NSCLC who progressed on prior Osi. Clinical trial information: NCT02099058.

*RECIST v1.1; data not mature for duration of response and progression-free survival. ^†c-Met IHC score < 25% 3+, n = 1. ^‡G719S mutation, n = 1.