Biogen has agreed to acquire Nightstar Therapeutics, a clinical-stage gene therapy company based in London, UK. The US drug firm will pay Nightstar shareholders $25.50 for each share they hold, valuing the company at about $877 million.

Nightstar’s entire share capital (both issued and to be issued) will be acquired by Tungsten Bidco, a newly incorporated company and wholly-owned subsidiary of Biogen Switzerland Holdings. The acquisition will be implemented by way of a UK court-sanctioned scheme of arrangement as defined by the UK Companies Act.

Nightstar is focused on developing and commercializing adeno-associated virus (AAV) therapies for inherited eye diseases that would otherwise progress to blindness and for which there are currently no approved treatments.

“With this proposed acquisition, we are continuing to bolster our pipeline and further execute our strategy to develop and expand a multi-franchise neuroscience pipeline across complementary modalities,” commented Biogen CEO Michel Vounatsos. “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,” he said.

Nightstar’s lead candidate NSR-REP1 is currently in Phase 3 trials for treating patients with choroideremia, a rare degenerative, genetic retinal disorder that mostly affects males. Data from Phase 3 is expected to be available in the second half of 2020.

A second candidate, NSR-RPGR, is being evaluated in the Xirius clinical trial for treating patients with X-linked retinitis pigmentosa, an inherited X-linked retinal disease that also primarily affects males. The abnormality results in retinal dysfunction by adolescence and early adulthood, progressing to blindness by the time patients are in their 40s.

Last September, Nightstar announced positive Phase 1/2 data from the dose escalation part of the Xirius trial; the Phase 2/3 dose expansion portion of that trial is ongoing.

Commenting on the acquisition, Nightstar CEO David Fellows said: “Our agreement with Biogen will give us the platform and resources to expand our mission to maintain and restore sight in patients with inherited retinal diseases. Together, with Biogen’s expertise in rare diseases, worldwide reach and extensive resources, we will dramatically improve the lives of patients around the world who currently have no treatment options.”

Biogen, which is funding the purchase through available cash, expects to close the transaction by mid-2019. Completion remains subject to the usual closing conditions, approvals from both Nightstar shareholders and regulators, as well as the issuing of a UK court order.