U.S. stocks were higher, with the Nasdaq Composite gaining around 1% on Monday.Shares of Janus Henderson Group plc (NYSE:JHG) rose sharply during Monday's session after the company confirmed receiving a non-binding takeover proposal from Trian Fund Management for $46 per share.Janus Henderson Group shares surged 16.2$48.36 on Monday.Here are some other big stocks recording gains in today’s session.Avidity Biosciences, Inc. (NASDAQ:RNA) shares jumped 43% to $70.22 after Novartis announced it will acquir ...