About one-third of all patients with psoriasis will develop psoriatic arthritis (PsA), a condition that comes with a host of vague symptoms and no definitive blood test for diagnosis. Prevention trials could help to identify higher-risk groups for PsA, with a goal to catch disease early and improve outcomes. The challenge is finding enough participants in a disease that lacks a clear clinical profile, then tracking them for long periods of time to generate any significant data.
Researchers have been taking several approaches to improve outcomes in PsA, Christopher Ritchlin, MD, MPH, chief of the allergy/immunology and rheumatology division at the University of Rochester (N.Y.), said in an interview. “We are in the process of identifying biomarkers and imaging findings that characterize psoriasis patients at high risk to develop PsA.”
The next step would be to design an interventional trial to treat high-risk patients before they develop musculoskeletal inflammation, with a goal to delay onset, attenuate severity, or completely prevent arthritis. The issue now is “we don’t know which agents would be most effective in this prevention effort,” Dr. Ritchlin said. Biologics that target specific pathways significant in PsA pathogenesis are an appealing prospect. However, “it may be that alternative therapies such as methotrexate or ultraviolet A radiation therapy, for example, may help arrest the development of joint inflammation.”
Underdiagnosis impedes research
Several factors may undermine this important research.
For one, psoriasis patients are often unaware that they have PsA. “Many times they are diagnosed incorrectly by nonspecialists. As a consequence, they do not get access to appropriate medications,” said Lihi Eder, MD, PhD, staff rheumatologist and director of the psoriatic arthritis research program at the University of Toronto’s Women’s College Research Institute.
The condition also lacks a good diagnostic tool, Dr. Eder said. There’s no blood test that identifies this condition in the same manner as RA and lupus, for example. For these conditions, a general practitioner such as a family physician may conduct a blood test, and if positive, refer them to a rheumatologist. Such a system doesn’t exist for PsA. “Instead, nonspecialists are ordering tests and when they’re negative, they assume wrongly that these patients don’t have a rheumatic condition,” she explained.
Many clinicians aren’t that well versed in PsA, although dermatology has taken steps to become better educated. As a result, more dermatologists are referring patients to rheumatologists for PsA. Despite this small step forward, the heterogeneous clinical presentation of this condition makes diagnosis especially difficult. Unlike RA, which presents with inflammation in the joints, PsA can present as back or joint pain, “which makes our life as rheumatologists much more complex,” Dr. Eder said.
Defining a risk group
Most experts agree that the presence of psoriasis isn’t sufficient to conduct a prevention trial. Ideally, the goal of a prevention study would be to identify a critical subgroup of psoriasis patients at high risk of developing PsA.
However, this presents a challenging task, Dr. Eder said. Psoriasis is a risk factor for PsA, but most patients with psoriasis won’t actually develop it. Given that there’s an incidence rate of 2.7% a year, “you would need to recruit many hundreds of psoriasis patients and follow them for a long period of time until you have enough events.”
Moving forward with prevention studies calls for a better definition of the PsA risk group, according to Georg Schett, MD, chair of internal medicine in the department of internal medicine, rheumatology, and immunology at Friedrich‐Alexander University, Erlangen, Germany. “That’s very important, because you need to define such a group to make a prevention trial feasible. The whole benefit of such an approach is to catch the disease early, to say that psoriasis is a biomarker that’s linked to psoriatic arthritis.”
Indicators of risk other than psoriasis, such as pain, inflammation seen in ultrasound or MRI, and other specificities of psoriasis, could be used to define a population where interception can take place, Dr. Schett added. Although it’s not always clinically recognized, the combination of pain and structural lesions can be an indicator for developing PsA.
One prospective study he and his colleagues conducted in 114 psoriasis patients cited structural entheseal lesions and low cortical volumetric bone mineral density as risk factors in developing PsA. Keeping these factors in mind, Dr. Schett expects to see more studies in biointervention in these populations, “with the idea to prevent the onset of PsA and also decrease pain and subcutaneous inflammation.”
Researchers are currently working to identify those high-risk patients to include in an interventional trial, Dr. Ritchlin said.
That said, there’s been a great deal of “clinical trial angst” among investigators, Dr. Ritchlin noted. Outcomes in clinical trials for a wide range of biologic agents have not demonstrated significant advances in outcomes, compared with initial studies with anti–tumor necrosis factor–alpha (TNF-alpha) agents 20 years ago.
One approach that’s generated some interest is the use of combination biologics medications. Sequential inhibition of cytokines such as interleukin-17A and TNF-alpha is of interest given their central contribution in joint inflammation and damage. “The challenge here of course is toxicity,” Dr. Ritchlin said. Trials that combined blockade of IL-1 and TNF-alpha in a RA trial years ago resulted in significant adverse events without improving outcomes.
Comparatively, a recent study in The Lancet Rheumatology reported success in using the IL-17A inhibitor secukinumab (Cosentyx) to reduce PsA symptoms. Tested on patients in the FUTURE 2 trial, investigators demonstrated that secukinumab in 300- and 150-mg doses safely reduced PsA signs and symptoms over a period of 5 years. Secukinumab also outperformed the TNF-alpha inhibitor adalimumab in 853 PsA patients in the 52-week, randomized, head-to-head, phase 3b EXCEED study, which was recently reported in The Lancet. Articular outcomes were similar between the two therapies, yet the secukinumab group did markedly better in Psoriasis Area and Severity Index scores, compared with the adalimumab group.
Based on these findings, “I suspect that studies examining the efficacy of combination biologics for treatment of PsA will surface in the near future,” Dr. Ritchlin said.
Yet another approach encompasses the spirit of personalized medicine. Clinicians often treat PsA patients empirically because they lack biomarkers that indicate which drug may be most effective for an individual patient, Dr. Ritchlin said. However, the technologies for investigating specific cell subsets in both the blood and tissues have advanced greatly over the last decade. “I am confident that a more precision medicine–based approach to the diagnosis and treatment of PsA is on the near horizon.”