** Shares of drug developer Celcuity CELC.O fall 7.5% to $102.7 premarket

** The U.S. FDA late on Tuesday approved CELC's drug for an advanced form of breast cancer, making it the company's first product to gain market entry

** The drug, branded as Revtorpyk, intends to treat patients with advanced breast cancer whose tumors have low levels of a protein called HER2 and no mutation in a gene called PIK3CA

** CELC expects to begin marketing the drug in the third quarter

** "Approval was largely expected, but the company delayed the launch until late 3Q26, which we did not anticipate given prior commentary on launch readiness," Leerink Partners says

** "We expect shares to be volatile, especially following the announcement that a large shareholder sold positions" - Leerink

** As of last close, CELC up 11.3% YTD