medwireNews: The selective janus kinase (JAK )1 inhibitor filgotinib has shown efficacy in patients with psoriatic arthritis with no new safety signals, show phase II data from the EQUATOR study.
After 16 weeks of treatment, there was a 47% treatment difference in ACR20 response between the 65 patients randomly allocated to receive filgotinib 200 mg/day and the 66 patients allocated to receive placebo.
The findings, presented at the 2018 ACR/ARHP Annual Meeting in Chicago, Illinois, USA and also published in The Lancet, “support the development of filgotinib for the treatment of psoriatic arthritis in patients with an inadequate response to conventional synthetic DMARDs,” say the study authors, led by Philip Mease, from Swedish-Providence–St Joseph Health Systems in Seattle, Washington, USA.
The study participants were 18 years of age or older and had moderate-to-severe psoriatic arthritis, with at least five swollen joints and at least five tender joints. They had active plaque psoriasis or a history of it, and had failed to respond, or were intolerant to, at least one conventional synthetic DMARD.
The patients continued to take conventional synthetic DMARDs during the study if they had been taking them for at least 12 weeks and at a stable dose for at least 4 weeks.
In all, 52 (80%) patients taking filgotinib met the criteria for an ACR20 response after 16 weeks, compared with 22 (33%) patients taking placebo. And just 8% and 3% of patients in the filgotinib and placebo groups, respectively, discontinued treatment.
“Filgotinib’s onset of action was rapid, with measurable improvements in disease activity after 1 week of treatment,” the study authors note.
The treatment was also associated with significant improvements over placebo in the signs and symptoms of peripheral arthritis, enthesitis, and psoriasis, as well as overall psoriatic arthritis disease control, according to Psoriatic Arthritis Disease Activity Score and fulfilment of minimal disease activity criteria.
On patient-reported outcomes, filgotinib showed significant benefits for physical functioning, fatigue, and pain, significantly improving pain intensity at week 1 and Health Assessment Questionnaire-Disability Index scores at week 2.
The selective JAK1 inhibitor was well tolerated had a safety profile that was in line with previous reports. Adverse events were mainly mild to moderate and could be routinely managed.
The rate of serious treatment-emergent adverse events was similar between the two treatment groups, at 56.9% in patients taking filgotinib and 59.1% in those taking placebo, and led to just one treatment discontinuation in the filgotinib group.
The researchers note and Mease echoed in his presentation that there were no cases of opportunistic infections or active tuberculosis, and no malignancies or major adverse cardiovascular or venous thromboembolic events.
There was a single case of uncomplicated herpes zoster virus in a filgotinib-treated patient and one serious infection (pneumonia).
“Selective inhibition of JAK1 might theoretically provide an improved safety profile compared with less selective JAK inhibitors,” the researchers suggest.
The effects of filgotinib on laboratory parameters were consistent with those previously reported in patients with rheumatoid arthritis.
Mease concluded that this is a “positive proof-of-concept study with filgotinib in patients with active psoriatic arthritis.”
The investigators now call for “[l]arger, global phase 3 trials […] to confirm these findings and to extend observations over a longer period of time.”
They add that “the safety of selective JAK1 inhibition should be explored further to determine whether the theoretical advantage of increased selectivity translates into a better safety profile in clinical practice.”
By Lucy Piper
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