Shares of Checkpoint Therapeutics Inc. dropped 44.8% Dec. 18 on news that the U.S. FDA issued a complete response letter (CRL), delaying potential approval of PD-L1 antibody cosibelimab in metastatic or locally advanced cutaneous squamous cell carcinoma. The FDA had accepted in March the BLA, seeking use for treating patients who are not candidates for curative surgery or radiation, setting a Jan. 3, 2024, PDUFA date.