First-in-human study of ABBV-400, a novel c-Met–targeting antibody-drug conjugate, in advanced solid tumors: Results in colorectal cancer.

3515 Background: c-Met (MET protein) is frequently overexpressed in several advanced solid tumors including colorectal cancer (CRC). There are no approved therapies specific for c-Met–overexpressing tumors in CRC. The antibody-drug conjugate ABBV-400 comprises c-Met–targeting antibody telisotuzumab conjugated to a novel topoisomerase 1 inhibitor payload. A phase 1 study of ABBV-400 was initiated for adults with advanced solid tumors and progression on standard therapies (NCT05029882); results from dose escalation (ESC) at doses 1.6–6.0 mg/kg once every 3 weeks (Q3W) were previously presented and showed preliminary efficacy (Sharma et al. ASCO 2023. Abstract 3015). We present data from dose ESC and expansion (EXP) cohorts in CRC. Methods: During EXP, patients (pts) with CRC were randomized to receive ABBV-400 at 1.6, 2.4, or 3.0 mg/kg Q3W. Primary objectives were to evaluate the safety, tolerability, pharmacokinetics, preliminary efficacy, and the recommended phase 2 dose of ABBV-400. Results: As of Oct 2023, 122 pts (ESC: 29; EXP: 93) were included. Median age: 56 years; 65 (53%) males. Median prior treatments was 4. Follow-up was longer in ESC vs EXP (14.8 vs 3.8 months). Seventy-eight (64%) pts had a grade (G)≥3 treatment-emergent adverse event (TEAE); 41% had a serious TEAE. Most frequent hematologic TEAEs were anemia (52%; G≥3: 30%), neutropenia (37%; G≥3: 25%), leukopenia (25%; G≥3: 12%), and thrombocytopenia (23%; G≥3: 12%); nonhematologic TEAEs were nausea (57%, G≥3: 3%), fatigue (43%; G≥3: 2%), and vomiting (39%, G≥3: 4%). G≥3 diarrhea was 30% was observed at efficacious doses (≥2.4 mg/kg). Activity was also seen at lower c-Met expression levels (10–15% ORR). Conclusions: ABBV-400 at 2.4 and 3.0 mg/kg Q3W has a tolerable and manageable safety profile, with promising antitumor activity. Long-term tolerability appears improved at 2.4 relative to 3.0 mg/kg, with higher relative dose intensity and generally lower TEAEs. The study is also evaluating ABBV-400 with bevacizumab in pts with CRC. Clinical trial information: NCT05029882 . Table: see text