** Shares of Regulus Therapeutics RGLS.O more than double to $7.79 premarket
** Novartis offers to buy Regulus for $7/shr cash upfront and another $7/shr on hitting certain regulatory milestones for kidney disease drug farabursen
** Offer worth $800 mln on upfront price
** RGLS shares have already more than doubled this year through last close
(Reporting by Christy Santhosh)
((Christy.Santhosh@thomsonreuters.com))