Alexion Pharmaceuticals Inc. is offering SEK7.1 billion (US$855 million) to shareholders of Sweden's Wilson Therapeutics AB in a bid to acquire its phase III therapy for Wilson's disease, a rare copper-excess condition. Alexion CEO Ludwig Hantson called the deal "a strong strategic fit" for his company that will play "an important first step in rebuilding our clinical pipeline."

The offer represents a premium of 89 percent over the 90-day volume-weighted average of Wilson's shares (NASDAQStockholm:WTX).

Analysts lauded the move, pointing to Alexion's need to diversify its portfolio to reduce its heavy reliance on sales of Soliris (eculizumab), a megablockbuster complement inhibitor that has generated billions of dollars in revenue for the company but faces both competitive and market challenges. Wilson's lead asset, a copper-protein-binding agent called WTX-101, could play a key part in helping the company capture market share in a new ultra-rare indication, assuming a pivotal phase III study of the orphan drug succeeds.

The trial, called Focus, is expected to read out in the second half of 2019. It's the first-ever randomized controlled trial in the condition, which hasn't had a new therapy in more two decades. (See BioWorld, Oct. 24, 2017.)

Wilson Therapeutics was founded in 2012 by Healthcap, a Stockholm-based venture capital fund. Other funding for the company has come from London-based Abingworth LLP and MVM Life Science Partners LLP, also of London. In 2016, via a successful IPO on Nasdaq Stockholm, Wilson raised gross proceeds of about SEK435.6 million (US$53 million). If successful, its WTX-101 program could meet a potential billion-dollar market opportunity in the U.S., it noted in a prospectus for the offering.

Through a subsidiary created for the purpose of the deal, Alexion Pharma Nordics Holding AB, Alexion is offering Wilson Therapeutics shareholders SEK232 (US$27.86) in cash per share. Healthcap, Abingworth, MVM and Neomed Innovation, which collectively own about 57.4 percent of Wilson's total shares and votes, have accepted the offer, subject to certain conditions. Polar Capital, which holds 7.3 percent of Wilson's shares also intends to accept the offer.

With the money raised in its IPO and SEK244 million more raised in a subsequent direct share issue in December, Wilson's 17-person team was preparing to take WTX-101 to market on its own, Jonas Hansson, CEO of Wilson Therapeutics, told BioWorld. "But, we also said that if we got an offer that would be attractive to the shareholders, we'd evaluate it," he said. Alexion's bid, though still open, fit the bill, offering a good match for WTX-101, which he characterized as "a great asset that can really be a game-changer for these patients."

Wilson's disease is inherited as an autosomal recessive disorder of impaired copper transport and excretion, caused by loss of function of the ATP7B copper-binding protein. It leads to copper overload in the liver, the release of free copper into the blood, and damaging accumulation of copper in the brain and other organs. Left untreated, it's ultimately fatal.

It's estimated to affect about one in every 30,000 live births, though its exact prevalence is subject of ongoing debate, according to Clarivate Analytics' Incidence and Prevalence Database. There are estimated to be about 10,000 patients in the U.S. and about 15,000 patients in the EU presenting a mix of symptoms, in two major groups, impacting the liver and the central nervous system.

Approved therapies for the disease include the chelating agents Cuprimine (penicillamine) and Syprine (trientine hydrochloride), both sold by Valeant Pharmaceuticals International Inc., and Galzin (zinc acetate) from Teva Pharmaceutical Industries Ltd. Though they represent the standard of care, all must typically be taken multiple times daily and on an empty stomach and costs can be high — an issue that came into sharp relief in recent years as some patients, doctors and U.S. senators expressed outrage over ongoing price hikes for Syprine and Cuprimine by Valeant.

To support its own pricing of the drug and competitive case should it gain market approvals, Alexion will be looking "to support differentiated mechanism of actions" vs. available chelators, John Orloff, Alexion's head of R&D said, during and investor call on Wednesday. That argument will draw on liver data as well as neurological testing.

"For the chelators, they are often associated, after initiation of therapy in up to 25 percent of patients, with neurological worsening. Part of that is because of the low affinity to copper. We think that's something we can overcome with WTX-101," Orloff said. The phase III program is designed to capture both noninferiority to other chelators and to test for superiority, in terms of free copper levels.

Though WTX-101 has patent protection through 2023 and additional protections tied to orphan drug status awards in the U.S. and Europe, Wilson has said that patent applications filed regarding the company's clinical approach and production method may, if granted, help it extend patent protection through 2039. With further competition in motion — most notably in the form of a discovery-stage program at Paris-based Vivet Therapeutics SAS, VTX-801, every added advantage is likely to help.

Alexion's purchase of Wilson, if completed, would be the company's biggest deal since moving to buy Synageva Biopharma Corp. for $8.4 billion in cash and stock in 2015, a deal that while successful in getting its chief asset to market, has yet to meet initial expectations around its potential benefit to the company's bottom line. (See BioWorld Today, Aug. 31, 2016.)

Wilson's shares climbed about 69.2 percent on Wednesday. Alexion's shares (NASDAQ:ALXN) lost $2.67, or 2.4 percent, to close at $110.79.