** Shares of drugmaker Regeneron Pharmaceuticals REGN.O fall 5.24% to $693.43

** Co says Q1 sales for its eye-disease drug, Eylea, fell 10% to $941 million with the drug's higher dose version, Eylea HD, impacted by lower wholesaler inventory levels

** RBC Capital Markets says the stock is anticipated to be down on softer Eylea HD sales, regulatory complexities for its pre-filled syringe version and an experimental lung cancer drug combo not progressing to late-stage trials

** Co says the U.S. FDA did not act by its April 2026 target date on REGN's application for a second contract manufacturer, tied to the pre-filled syringe version of Eylea HD

** Co posts Q1 adjusted profit of $9.47 per share, above analysts' estimate of $8.94, according to LSEG data

** Including session's move, REGN down 11.1% YTD