LONDON (Reuters) – Strong results for an experimental drug that promises to disrupt the rheumatoid arthritis market lifted shares in Belgian-Dutch firm Galapagos to an all-time high on Wednesday, as analysts forecast multibillion-dollar sales.

The stock was 15 percent higher by 0945 GMT, valuing the biotech company at around $6 billion.

The new data from a late-stage clinical trial suggests filgotinib – being developed with Gilead Sciences – will have a competitive profile among rival medicines in the so-called JAK inhibitor drug class, analysts said.

Existing JAK inhibitors include Pfizer’s Xeljanz and Eli Lilly’s Olumiant. Abbvie 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 put peak sales at $4 billion.

(Reporting by Ben Hirschler; Editing by Alexander Smith)