Angelini Pharma is buying Catalyst Pharmaceuticals for about $4.1 billion in cash, securing a foothold in the U.S. rare-disease market and expanding its neurology presence. The deal values Catalyst at $31.50 per share, representing a 28% premium to the prior 30-day period before deal talk became public. Catalyst sells three approved medicines, and Angelini said the acquisition strengthens its portfolio and platform in neurology. The transaction also underscores how quickly large pharma and specialty companies are consolidating established rare-disease franchises to build patient access and revenue durability.