** Shares of drugmaker Madrigal Pharmaceuticals MDGL.O rise 5.3% to $529.08

** Co posts Q1 revenue of $311.3 million, above analysts' estimate of $300.8 million, according to LSEG data

** Rezdiffra - MDGL's only marketed drug for a fatty liver disease called MASH - accounted for all Q1 revenue, with sales up 127% year-over-year

** Co says more than 42,250 patients were on Rezdiffra as of March 31, up about 2.5 times from a year earlier

** "We continue to have conviction in the MASH market size, and see MDGL shares as undervalued relative to other mid cap biotechs," Barclays says

** Including session's move, MDGL down 9.8% YTD