Gilead and Galapagos close in on filing for Xeljanz rival

Galapagos and Gilead Sciences have a pair of positive phase 3 trials for their JAK inhibitor filgotinib in rheumatoid arthritis that they say make it a contender in the market.

The two studies – FINCH 1 and FINCH 3 – show that the drug is effective at reducing the symptoms of RA, including joint tenderness and swelling, but also suggest it won’t be plagued by the side effect problems that have held back some other drugs in the JAK inhibitor class.

The safety of JAK inhibitors has once again come under the spotlight after regulators announced investigations into reports of life-threatening blood clots in patients taking a higher dose of Pfizer's Xeljanz.

If approved, filgotinib would likely be the fourth JAK inhibitor for RA after Pfizer’s $1.8bn seller Xeljanz (tofacitinib), Eli Lilly’s Olumiant (baricitinib), and AbbVie’s upadacitinib which has already been submitted for approval with a verdict expected in the third quarter.

It would be Belgian biotech Galapagos’ first approved drug, and an important new product for Gilead which is trying to diversify its product portfolio in the face of slumping sales of its hepatitis C drugs into new areas like cancer, liver disease and immunology.

In FINCH 1, selective JAK1 inhibitor filgotinib was compared to AbbVie’s $18bn-a-year TNF antibody Humira (adalimumab) or placebo – given on top of generic disease-modifying antirheumatic drug (DMARD) methotrexate – in patients with moderate-to-severe RA who weren’t responding to methotrexate alone.

Daily oral dosing with filgotinib was significantly better than placebo at achieving a 20% improvement in symptoms (an ACR 20 response), the primary endpoint in the study, and matched the efficacy of Humira which is given by injection.

Dr Walid Abi-Saab, chief medical officer at Galapagos said the company was excited by the strong efficacy and tolerability results. "We are particularly pleased with the results filgotinib shows on clinically meaningful endpoints such as clinical remission, ACR70 and radiographic progression, as well as with the encouraging safety profile."

FINCH 3 compared Galapagos and Gilead’s drug alone or in combination with methotrexate as a front-line therapy for patients with moderate-to-severe RA, and found that the combination was significantly better than methotrexate alone at helping patients achieve an ACR20 response.

Filgotinib monotherapy was as effective as methotrexate on the ACR20 measure, but was significantly better on the tougher 50% improvement (ACR50) and 70% improvement (ACR70) scales.

In both studies there was a low incidence of venous thrombosis, a side effect that held up the approval of Olumiant by the FDA and resulted eventually in a green light for only a lower dose of the drug that analysts have suggested will struggle to compete in the marketplace.

The data suggest that filgotinib can mount a serious challenge in the JAK inhibitor market for RA, including upadacitinib which generated similar results in phase 3 testing and has been billed as a possible best-in-class candidate by some analysts.

AbbVie itself has predicted sales of upadacitinib could reach $3bn by 2025, and it remains to be seen whether a likely lead in the marketplace of around a year will peg back filgotinib’s momentum – assuming both are approved.

A lot will depend on the labelling that wins through the FDA review process, particularly with regards to safety.

Analysts at Jefferies have suggested that filgotinib does seem to have a superior safety profile, and that could drive sales to $6bn at peak, with around half of that coming from RA and the rest from other diseases such as psoriatic arthritis, Crohn's disease, ulcerative colitis, ankylosing spondylitis and atopic dermatitis.

Gilead licensed rights to filgotinib in a $2bn deal signed in 2015, after AbbVie ducked out of a partnership on the drug in order to concentrate on in-house candidate upadacitinib.