Dr. Kingsley: “Methotrexate might have worked in a longer study, but we were limited to six months because it was felt the use of placebo for a longer period might not be ethical. Methotrexate might (also) have worked at a higher dose than we used.” However, Dr. Kingsley notes the 15 milligrams a week used in this study is comparable to the effective dose used for rheumatoid arthritis in other clinical trials – and is an effective dose for skin psoriasis.

AT: Were specific subtypes of psoriatic arthritis targeted in the study?

Dr. Kingsley: “A study which was powered to recruit enough patients with each different subtype of psoriatic arthritis would have been enormous and impractical. We did not intend to differentiate among the different subtypes as the paper makes clear.” But, she notes, a simple analysis between polyarticular and oligoarticular diseases showed no difference in drug response.

AT: Did the study look at methotrexate in combination therapy with, for example, a biologic agent, which is sometimes used when monotherapy fails?

Dr. Kingsley: “We didn’t look at methotrexate in combination therapy, which the TICOPA study is doing. There is already a combination study, RESPOND, which compares MTX plus infliximab against MTX alone, but that is really a study of infliximab, since both groups had MTX.”

AT:  How clinically relevant do you think the results of this study are?

Dr. Kingsley: “The patients recruited to the study were very similar in all clinical and disease activity measures to those psoriatic arthritis patients recruited to the NOR-DMARD study, a large Norwegian observational study of patients with various sorts of inflammatory arthritis who were starting methotrexate. Therefore the study seems generalizable to routine patients.” Dr. Kingsley adds that the only other randomized controlled trial of methotrexate in PsA, though a small one, showed similar results – that is, no significant effect on synovitis vs. placebo – and that there are no randomized controlled trials that show an effect on synovitis for low-dose oral methotrexate in PsA.