With its launch barely three years in the rearview mirror, Remix Therapeutics Inc. has inked its second potential $1 billion pharma collaboration, drawing Roche Holding AG to the table with the promise of its RNA processing platform and the potential to develop small-molecule therapeutics targeting the underlying drivers of disease. At the same time, the Watertown, Mass.-based firm added $60 million in a venture round, bringing its total financing to date to $201 million.