Dose optimization and exposure-response analyses to support optimal dose of ABBV-400, a novel C-met–targeting antibody drug conjugate, in patients with metastatic colorectal cancer (mCRC).

3030 Background: ABBV-400 is an antibody drug conjugate (ADC) consisting of a c-Met targeting antibody conjugated to a potent inhibitor of topoisomerase 1 (Top1) payload. ABBV-400 has shown encouraging activity and demonstrated tolerability of dosages up to 3.0 mg/kg Q3W as monotherapy in patients with advanced solid tumors in an ongoing phase 1 study (1). Dosage optimization is a critical aspect of oncology drug development and FDA Project Optimus has focused on reformulating the dosage selection paradigm for oncology products. The phase 1 study included a dose optimization phase in mCRC patients in which 3 doses were evaluated (1.6, 2.4 and 3.0 mg/kg Q3W) to determine the optimal dose for further development. Herein, exposure-response analyses are reported to determine optimal monotherapy dose in mCRC patients. Methods: Data across a range of doses (1.6 – 6.0 mg/kg Q3W) from the phase 1 study (NCT05029882) were used. Population pharmacokinetics (PK) and exposure-response (E-R) analyses were conducted to characterize ABBV-400 conjugate and unconjugated payload PK and the relationship between exposures and efficacy (objective response rate [ORR]) and safety (Grade (Gr) ≥ 3 neutropenia, anemia and thrombocytopenia) endpoints. Relative dose intensity (RDI) analysis was performed. Results: ABBV-400 conjugate and payload PK were adequately described by a combined multi-analyte population PK model with first order kinetics (n=204). ABBV-400 conjugate average concentration was a better predictor of response and showed that higher exposure correlated with higher probability of response (n=122 CRC, ORR, p < 0.05) and safety events (n=204, Gr ≥ 3 neutropenia, anemia and thrombocytopenia, p < 0.001). Dose intensity analyses showed greater number of dose reductions for 3 mg/kg Q3W with effective (actual) dose received of 2.6 mg/kg Q3W in mCRC patients. E-R analyses for safety and efficacy and dose intensity analyses in mCRC 3L+ patients indicate that both 2.4 and 3.0 mg/kg doses provided meaningful efficacy (ORR); while the 3.0 mg/kg dose may provide higher response rates, the 2.4 mg/kg Q3W dosing regimen provides an optimal balance of safety and efficacy compared to 3.0 mg/kg Q3W. Conclusions: Population PK, E-R for efficacy and safety and RDI analyses and totality of clinical data supported the selection of 2.4 mg/kg Q3W as optimal ABBV-400 monotherapy dose for further study in mCRC patients. 1. Sharma M, et al. ASCO 2023. Abstract 3015. Clinical trial information: NCT05029882 .