More effective rituximab dosing for pemphigus identified

Pemphigus vulgaris, H&E stain. Photo by: Nephron via Wikimedia Commons

Prescribing a ‘lymphoma dose’ of the biologic rituximab for pemphigus vulgaris results
in patients having a much higher chance of achieving complete clearance than a
‘rheumatoid arthritis dose,’ according to new findings.

Published online in JAMA Dermatology (Oct. 23, 2019), the findings come from a cohort
study of 112 patients with pemphigus. The investigators found that pemphigus patients
receiving more frequent infusions of the biologic, adjusted for their bodies, were nearly
three times as likely to achieve complete remission than patients treated with two fixed-
dose infusions.

In a press release from the Perelman School of Medicine at the University of
Pennsylvania in Philadelphia, where the research was conducted, the authors note that
the U.S. FDA has approved a dosing regimen of rituximab for pemphigus that
resembles the dosing used to treat rheumatoid arthritis (RA)—a fixed dose of two 1,000
mg infusions, two weeks apart. In contrast, rituximab dosing for lymphoma is calculated
by patient height and weight, and infusions are given weekly for four weeks.

Because many patients’ insurance only covers the lower dose, and there are concerns
about infection risk with higher doses of immunosuppressants, many doctors favour the
lower dose for pemphigus.

“All these reasons made it logical for physicians to use the medication more
conservatively,” said the study’s senior author Dr. Aimee Payne, director of the Penn
Clinical Autoimmunity Center of Excellence. “However, our findings suggest that the
more aggressive lymphoma approach gives a patient the best chance for complete
remission off oral immune suppressants, and that’s obviously the desired outcome.”

Controlling for age, sex, pemphigus subtype, BMI, and disease duration, patients in the
cohort who received lymphoma vs. rheumatoid arthritis dosing were 2.70-fold more
likely to achieve complete remission that persisted without continuing therapy (called complete remission off therapy or CROT in the paper).

As well, Dr. Payne and her team found that the odds of achieving complete remission in
patients over age 65 was almost 10-fold greater than those under age 45, and patients

with moderate to severe obesity had over 7-fold lower odds of achieving complete
remission compared to non- or mildly obese patients.

Regardless of dosing, the authors say in the release that the evidence supports the use
of rituximab in general for treating pemphigus. Before the medication, the only FDA-
approved treatment option was a course of steroids. Looking at rituximab’s success in
both dosing regimens combined, the study showed 48% of patients achieved complete
remission after just one cycle of the therapy. With repeated cycles, complete remission
jumped to 71%.

Serious infections were seen in 5% of patients in this study over the courses of their
rituximab treatments. That is lower than historical serious infection rates among patients
treated with high-dose steroid regimens.

“Rituximab is not a perfect medication since it does weaken one’s immune system like
steroids do, but it is more effective than steroids in treating this very serious
autoimmune disease,” said Dr. Payne.

“This is the first study to provide evidence for physicians to justify a lymphoma-dose
regimen of rituximab when treating their patients with pemphigus.”