AMSTERDAM, The Netherlands – Investigators who are monitoring the continuing IMPACT (Infliximab Multinational Psoriatic Arthritis Controlled Trial) of infliximab (Remicade®) in psoriatic arthritis (PsA) patients are now so bullish about the success of the treatment that they plan to publish the first-ever guidelines on what constitutes remission in the formerly incurable disease.

"No such criteria have ever been established," Arthur Kavanaugh, MD, of the Center for Innovative Therapy in the division of rheumatology, allergy, and immunology at the University of California, San Diego, told participants at the EULAR meeting.¹ "But we can say for sure that all parameters will be included and that remission will mean an absence of peripheral arthritis, skin and nail disease, enthesitis, and axial dactylitis."

The lead investigator in the study, Dr. Kavanaugh said that in controlled clinical trials over 2 years, "a significant proportion of PsA patients treated with infliximab have been able to attain a very high degree of sustained clinical improvement in arthritis." In both the IMPACT 1 and IMPACT 2 trials, patients were assessed using a measure borrowed from rheumatoid arthritis (RA)trials: "major clinical response," defined as maintenance of a 70% improvement in arthritic symptoms over 6 continuous months.

"Now we need to get the research done to define major clinical response specific for PsA," Dr. Kavanaugh said. "Low disease activity is, of course, desirable, but it should be seen as distinct from the truly effective therapeutic intervention, which is what we want and believe we can achieve for our patients." According to Dr. Kavanaugh, remission in PsA would be defined as "sustained high-degree improvements in the arthritic and dermatological components of the disease."

However, the recommended dose of 5 mg/kg of infliximab would mean that treatment of PsA to achieve full remission would be "expensive," Dr. Kavanaugh admitted. "It may be that there is wiggle room that might enable us to cut down on therapy in order to reduce the cost," he said. "There is also the possibility that by intervening very early on, we can back off on the level of treatment that is needed—and further research is needed to establish whether this is the case."

Meeting participants were also given details of the impact of infliximab during the IMPACT 2 trial,² in which 200 PsA patients were given either infliximab or placebo for 16 weeks, after which placebo patients were offered early release so they could receive active treatment for the remaining period of the trial.

Lead investigator Dr. Desiree Van der Heijde, of the department of rheumatology at University Hospital in Maastricht, said that the therapy had been shown to inhibit radiographic progression in PsA patients as early as 24 weeks. "Radiographic improvement continued through 1 year," she said, adding that "improvement in radiographic scores was observed in placebo patients who initiated infliximab after a 16- to 24-week delay, but it was less than that observed in patients who initiated infliximab at the start of the study."

She said the impact of the drug on PsA was at least as fast as the impact on RA, but that it was impossible to say whether the effect was the result of reducing inflammation or whether the impact was directly on bone.

Reference

1. Kavanaugh A, et al. Treatment with infliximab is associated with "major clinical response" in psoriatic arthritis patients treated with infliximab: analysis of two double-blind placebo-controlled trials. Presented at: EULAR 2006; June 21–24, 2006; Amsterdam, the Netherlands. Abstract OP0104.
2. Van der Heijde D, et al. Infliximab inhibits progression of radiographic damage in patients with active psoriatic arthritis: 54-week results from IMPACT 2. Presented at: EULAR 2006; June 21–24, 2006; Amsterdam, the Netherlands. Abstract OP0105.