This has been shown to be true for both weight-based and fix-dosed treatment.
"So it’s not just that fat people aren’t getting enough of the drug, compared to the skinny people. It’s that obesity – as we’ve learned from our dermatology colleagues – is inflammatory and it’s something to be reckoned with," he said.
Weight loss really needs to be stressed to overweight patients in the clinic, he said.
• Important questions are being asked.
"Unlike for rheumatoid arthritis, we still don’t know if methotrexate and TNF inhibitors are synergistic. ... That’s a gap I would love to see filled in our psoriatic arthritis understanding," he said.
Another important idea that is being addressed involves thinking of how different means of attacking the immune system have disparate results in various immune diseases, thus showing that the diseases may be similar but are not the same.
Dr. Kavanaugh called this a "bedside-to-bench" phenomenon, in which treatment outcomes provide improved understanding of the disease processes.
Targeting interleukin (IL)-6, for example, works very well in RA, juvenile idiopathic arthritis (JIA), and systemic JIA, but it doesn’t work so well in ankylosing spondylitis, and it doesn’t appear that it will work well in several other conditions, based on anecdotal reports.
Similarly, drugs that target IL-17 – a very exciting prospect in psoriasis – don’t seem to work so well in RA. IL-17 inhibition theoretically should work well in inflammatory bowel disease, but it actually appears to make Crohn’s disease worse, he noted.
"We now have newer therapeutic approaches, and it’s very exciting, because we’re going to think of these diseases a little bit differently and almost define the diseases by how they respond to different focal immunomodulatory interventions," he said.
• New treatment targets and approaches are emerging.
There has been some question as to whether IL-23, which is known to be an important driver of IL-17, will be the mechanism by which IL-17 works.
Three IL-17 inhibitors are currently in development. Results in skin psoriasis have been remarkable, and there is a great deal of excitement about them, but data are just beginning to emerge for psoriatic arthritis, Dr. Kavanaugh said.
In an extension study reported at the 2013 annual meeting of the American College of Rheumatology (ACR), for example, the anti-IL-17 receptor A monoclonal antibody brodalumab demonstrated possible increased efficacy through 24 weeks of treatment.
"It’s very exciting to see new data. These drugs will come almost certainly to the clinic first for psoriasis, but I think if they are shown to have good effects in psoriatic arthritis, they will be available to us as another option in our patients," he said.
As for new treatment strategies, psoriatic arthritis is catching up with rheumatoid arthritis with respect to attention to tight control.
"The idea is to evaluate patients, and if they are not reaching a goal, you change treatment. That is the basis for TICOPA – tight control of early psoriatic arthritis," he said.
Joint and skin outcomes were significantly improved in patients in the 48-week, open-label, randomized controlled trial who were treated using a treat-to-target approach, compared with those treated with usual care, according to findings presented at ACR 2013.
However, more serious adverse events occurred in the tight control group (14 vs. 6 in the usual care group), Dr. Kavanaugh noted.
"So I think it’s a thought exercise. I think it shows us that tight control works in psoriatic arthritis. If you follow people very regularly, if you demand that they achieve a good goal like minimal disease activity, they are going to do better," he said.
The downside of increased adverse events raises interesting issues of value and pharmacoeconomics, he noted.
Another "superhot issue in psoriatic arthritis" is whether therapy – and particularly biologic therapy – can be stopped or tapered in patients who are doing very well. A number of studies are looking at this, and it’s an important issue that payers are interested in considering, but data are currently limited.
Based on data that are available, it appears that discontinuing therapy abruptly is not a good idea. In one small study, 77% of patients who discontinued therapy had a disease flare, with greater risk among those with longer treatment duration. Restart of treatment was effective in all cases.
"Certainly there is going to be a lot more interest in this in rheumatoid arthritis, and I think it’s going to spill over and we’ll see more studies in this in psoriatic arthritis as well," he said.
Dr. Kavanaugh reported having no financial disclosures.