By Ben Hirschler
LONDON (Reuters) - Strong results for an experimental drug that promises to disrupt the rheumatoid arthritis market lifted shares in Belgian-Dutch firm Galapagos <GLPG.AS> to an all-time high on Wednesday, as analysts forecast multibillion-dollar sales.
The stock was 18 percent higher by 1540 GMT, valuing the biotech company at around $6.2 billion (4.76 billion pounds), while shares in Gilead Sciences <GILD.O> - its development and marketing partner - rose by more than 3 percent.
The new data from a late-stage clinical trial suggests filgotinib will have a competitive profile among rival medicines in the so-called JAK inhibitor drug class, analysts said.
Existing JAK inhibitors include Pfizer's <PFE.N> Xeljanz and Eli Lilly's <LLY.N> Olumiant. Abbvie <ABBV.N> also has an experimental product called upadacitinib that may be approved next year.
Jefferies analyst Peter Welford said filgotinib's efficacy was on a par or above rivals and it also offered a potentially superior safety profile, which should drive uptake despite the medicine likely being fourth to market.
He forecasts worldwide peak annual sales for filgotinib of $6 billion - half from rheumatoid arthritis and the rest for treating other diseases.
Berenberg analysts, who put peak sales at $4 billion, said filgotinib was increasingly looking like a "best-in-class" medicine.
Gilead signed a deal https://www.reuters.com/article/galapagos-gilead-idUSL8N14611Q20151217 potentially worth more than $2 billion with Galapagos in December 2015, which included a $725 million upfront payment for the development of filgotinib, as well as an equity stake in the European firm.
Under the agreement, Gilead will market the drug and pay a royalty and milestones to Galapagos.
Results from further Phase III clinical trials of filgotinib in rheumatoid arthritis are expected next year. It is also being tested for treating Crohn’s disease and ulcerative colitis.
(Reporting by Ben Hirschler; Editing by Alexander Smith)