Merck & Co., Inc. (MRK.US) announced today that the U.S. FDA has granted breakthrough therapy designation to the investigational antibody-drug conjugate (ADC) sacituzumab tirutecan (Sac-TMT) for the treatment of advanced or metastatic non-squamous non-small cell lung cancer (NSCLC) patients with epidermal growth factor receptor (EGFR) mutations whose disease has progressed after receiving tyrosine kinase inhibitors (TKIs) and platinum-containing chemotherapy. Sac-TMT is an investigational ADC targeting TROP2 developed in collaboration with Merck and Coronovex (06990). The press release noted that this is the first time this therapy has received FDA breakthrough therapy designation.