GSK plc (LSE:GSK) agreed to acquire Efimosfermin alfa drug from Boston Pharmaceuticals Inc. for $2 billion on May 14, 2025. GSK will pay $1.2 billion upfront, with potential for additional success-based milestone payments totaling $800 million. GSK will also be responsible for success-based milestone payments as well as tiered royalties for efimosfermin owed to Novartis Pharma AG.

This transaction is subject to customary conditions, including applicable regulatory agency clearances under the Hart-Scott-Rodino Act in the USA. Evercore Partners International LLP acted as financial advisor and Cleary Gottlieb Steen & Hamilton LLP acted as legal advisor to GSK plc. Centerview Partners LLC acted as financial advisor and Sullivan & Cromwell LLP acted as legal advisor to Boston Pharmaceuticals.