Loading vs Not Loading, and Its Role in PsA and Other Diseases
“We stopped loading years ago because at 100 mg for 3 days in a row, everyone has GI issues,” Dr. Ruderman said. “It may have made sense from a pharmacokinetic standpoint because [based on the long half-life] you could get to a higher drug level quicker, but not a practical standpoint, because patients would stop the drug — they couldn’t take it.” The first study to examine the necessity of loading leflunomide in a “prospective, careful way” was published in 2013. It randomized 120 patients to 100 mg or 20 mg for 3 days, followed by a 3-month open-label period of 20 mg, and found no clinical benefit with loading but more diarrhea and elevated liver enzymes.
“It tells us something about how we need to think about half-lives,” he said. “Maybe [loading is] not necessary because the biological effects are different than the drug levels.”
In the PsA space, in 2004, researchers reported a double-blind randomized trial in which 190 patients with active PsA and cutaneous psoriasis with at least 3% body surface area involvement were randomized to receive leflunomide (a loading dose followed by 20 mg/day) or placebo for 24 weeks. Almost 60% of leflunomide-treated patients, compared with 30% of placebo-treated patients, were classified as responders by the Psoriatic Arthritis Response criteria (P < .0001), “which is a soft endpoint” but was utilized at the time, Dr. Ruderman said. The researchers noted improvements in ACR20 and skin responses as well, and toxicity was similar to that reported in the RA studies.
However, approval was never sought, and the drug was infrequently prescribed, “because etanercept came out for this disease, and then adalimumab … and then the world changed,” he said.
More recently, a single-center, double-blind, randomized trial that included 78 Dutch patients with PsA tested leflunomide plus methotrexate vs methotrexate monotherapy and was published in The Lancet Rheumatology. After 16 weeks, mean Psoriatic Arthritis Disease Activity Score (PASDAS) had improved for patients in the combination therapy group in comparison with the monotherapy group (3.1 [standard deviation (SD), 1.4] vs 3.7 [SD, 1.3]; treatment difference, -0.6; 90% CI, -1.0 to -0.1; P = .025). The combination therapy group also achieved PASDAS low disease activity at a higher rate (59%) than that of the monotherapy group (34%; P = .019). Three patients in the combination therapy group experienced serious adverse events, two of which were deemed unrelated to leflunomide. The most frequently occurring adverse events were nausea or vomiting, tiredness, and elevated alanine aminotransferase. Mild adverse events were more common in the methotrexate plus leflunomide group.
In an interview after the meeting, Dr. Ruderman explained that in his practice, about 15 years ago, leflunomide was sometimes prescribed as an alternative to a biologic change for patients whose skin disease improved significantly with ustekinumab (Stelara) but who “suddenly had more joint symptoms that they didn’t have before.”
And “we’ve found ourselves a bit recently with the same sort of story, where patients are prescribed IL-23 inhibitors like Skyrizi [risankizumab] and Tremfya [guselkumab] and their skin does really well but now they’re having more joint symptoms than previously,” he said. “Our choices are to switch to a whole different biologic, or to think about adding something as an adjunct — and maybe leflunomide is a reasonable option.”
In the last 5 years, Dr. Ruderman noted, randomized trial data has been published on leflunomide in lupus nephritis induction, and in lupus nephritis maintenance, as well as in IgG4-related disease.
Dr. Ruderman disclosed consulting and/or drug safety monitoring board work for AbbVie, Amgen, Bristol-Myers Squibb, Janssen, Lilly, Merck, Novartis, NS Pharma, and UCB.