Biogen, an American multinational biotechnology company based in Cambridge, completed the acquisition of Nightstar Therapeutics, a clinical-stage gene therapy company based in London, United Kingdom, which is focused on adeno-associated virus (AAV) treatments for inherited retinal disorders, for c.$877m. Biogen’s offer of $25.50 per share, represents a premium of 68% to Nightstar’s last close of $15.16. "Ophthalmology is an emerging growth area for Biogen, and we are excited about the opportunity to work with the talented employees at Nightstar to advance potentially transformative gene therapy programs for rare retinal diseases. With this proposed acquisition, we are continuing to bolster our pipeline and further execute on our strategy to develop and expand a multi-franchise neuroscience pipeline across complementary modalities. Nightstar would accelerate our entry into ophthalmology by contributing two mid- to late-stage gene therapy assets, with the potential to create long-term shareholder value," Michel Vounatsos, Biogen Chief Executive Officer.