Multi-parameter optimization of a novel anti-TROP2 MMAE antibody-drug-conjugate for solid tumor therapy

TROP2 is expressed in many epithelial tumors including breast and lung cancers. It is a clinically validated ADC target based on approvals of sacituzumab govitecan for triple-negative breast cancer and datopotamab deruxtecan for HR-positive, HER2-negative breast cancer. An alternative cytotoxic approach was previously tested with PF-06664178/RN927C, an anti-TROP2 ADC with an auristatin payload, which entered clinical studies but could not be dosed efficaciously due to dose-limiting toxicities including skin rash, mucosal inflammation, and neutropenia. TroptimAb-SL-MMAE was engineered using an optimized anti-TROP2 sacituzumab antibody sequence (TroptimAb) to address issues related to hydrophobicity, non-specific uptake, and ADC developability. Sacituzumab was re_-humanized and modified to enhance FcRn-mediated salvage which extended systemic half-life and potentially improving tumor distribution. Its affinity was avidity-tuned to preferentially bind cells with higher TROP2 expression to reduce on-target/off-tumor toxicity. An engineered cysteine in the Fc domain enabled generation of a homogeneous DAR2 ADC and shielded the linker-payload to reduce hydrophobicity and improve biophysical properties. Linker conjugation chemistry was also optimized to improve stability versus earlier cysteine-conjugated ADCs. We describe the preclinical profile of TroptimAb-SL-MMAE including its design, mechanism of action, anti-tumor activity, and pharmacokinetics.