Novartis AG just added muscle to its siRNA development effort by buying Dtx Pharma Inc. in an M&A deal that could total $1 billion. Novartis is getting a preclinical asset, DTx-1252, which just received the U.S. FDA’s orphan drug designation on June 8. Dtx is developing the siRNA candidate for treating the neuromuscular disease Charcot-Marie-Tooth disease type 1A (CMT1A). Basel, Switzerland-based Novartis will pay Dtx $500 million up front and make payments of up to $500 million in milestones completions.