On January 20, Eli Lilly (LLY.US) announced that the FDA has granted Breakthrough Therapy designation to sofetabart mipitecan (LY4170156). The designation is for the treatment of adult patients with platinum-resistant epithelial ovarian, fallopian tube, or primary peritoneal cancer who have previously received bevacizumab treatment and are eligible for further therapy following treatment with mirvetuximab soravtansine. LY4170156 is an FRα ADC drug originally developed by Mablink Bioscience (which has been acquired by Eli Lilly). It utilizes a proprietary linker technology and carries exatecan as its payload, with a DAR value of 8. The FDA's granting of the Breakthrough Therapy designation is based on positive preliminary data from the Phase Ia/b study of LY4170156. Results from the study indicate that the drug demonstrated efficacy across all dose levels, and its effectiveness was not limited by the patient's FRα expression level. Even patients who had experienced disease progression after prior treatment with mirvetuximab soravtansine were able to benefit from it. Preliminary data also suggests the drug has a favorable tolerability profile, with a low incidence of adverse events such as interstitial lung disease, peripheral neuropathy, and alopecia, and no significant ocular toxicity was observed.