Acadia Pharmaceuticals has partnered with Stoke Therapeutics to develop RNA-based therapies addressing severe and rare genetic neurodevelopmental diseases of the central nervous system (CNS) — in a deal potentially valued at close to $1 billion.

Under the deal, Stoke will receive $60 million upfront and is eligible to receive a further $907 million in milestones-based payments as well as royalties on future sales. Acadia and Stoke will share development costs and share profits equally.

Among other diseases, the companies said they plan to develop therapies for SYNGAP1 syndrome, a neurological disorder marked by moderate-to-severe intellectual disability that presents in early childhood, Rett syndrome, a neurological disorder occurring mainly in girls, and an undisclosed third clinical target.