** Shares of Roivant Sciences ROIV.O gain 2.5% to $12.35 premarket
** Healthcare company Organon OGN.N says it has agreed to buy skin therapy developer Dermavant, a unit of Roivant, for up to $1.2 billion
** The deal gives OGN access to Dermavant's psoriasis cream, VTAMA, approved by the U.S. FDA in May 2022
** OGN to make an upfront payment of $175 million, as well as milestone payments of up to $950 million as part of the deal
** OGN expects to close the transaction in Q4 this year
** Up to last close, ROIV shares up 7.3% YTD
(Reporting by Mariam Sunny in Bengaluru)