** Drug developer Checkpoint Therapeutics' CKPT.O shares rise 66% to $4.10 premarket
** India's Sun Pharmaceutical Industries SUN.NS will buy Checkpoint Therapeutics for $355 million, the companies said on Sunday
** Upfront cash payment of $4.10 per share, at a 66% premium to stock's last close
** CKPT's controlling arm Fortress Biotech FBIO.O would receive royalty payments based on future sales of co's skin cancer drug Unloxcyt during a specified term
** FBIO shares rise 12.3% to $1.73 before the bell
** The deal expected to be completed in Q2 2025
** CKPT has risen 13.8% in the last 12 months
(Reporting by Siddhi Mahatole)
((siddhi.mahatole@thomsonreuters.com))