Antibody-drug conjugate MORAb-202 exhibits long-lasting antitumor efficacy in TNBC PDx models.

The antibody-drug conjugate (ADC) MORAb-202, consisting of farletuzumab paired with a cathepsin B-cleavable linker and eribulin, targets folate receptor alpha (FRA), which is frequently overexpressed in various tumor types. MORAb-202 was highly cytotoxic to FRA-positive cells in vitro, with limited off-target killing of FRA-negative cells. Furthermore, MORAb-202 showed a clear in vitro bystander cytotoxic effect in coculture with FRA-positive/negative cells. In vivo antitumor efficacy studies of MORAb-202 were conducted with a single administration of MORAb-202 in triple-negative breast cancer (TNBC) patient-derived xenograft (PDx) models expressing low and high levels of FRA. MORAb-202 exhibited durable efficacy proportional to tumor FRA expression. Toxicology studies (Q3Wx2) in nonhuman primates suggested that the major observed toxicity of MORAb-202 is hematologic toxicity. Overall, these findings support the concept that MORAb-202 represents a promising investigational ADC for the treatment of TNBC patients.