PHILADELPHIA – In the first controlled clinical trial to compare the two drugs, rituximab and cyclophosphamide were similarly effective in improving lung function in patients with interstitial lung disease (ILD) associated with idiopathic inflammatory myositis and mixed connective tissue disease (CTD). The findings also revealed some nuanced findings that could help clarify which drug to use in specific patients.
“We feel that rituximab is a reasonable alternative to cyclophosphamide as a treatment in patients with these diseases,” said Toby Maher, MD, of the University of Southern California, Los Angeles, who presented results of an analysis of three disease subgroups from the RECITAL (Rituximab versus Cyclophosphamide for the Treatment of Connective Tissue Disease Associated Interstitial Lung Disease) study at the annual meeting of the American College of Rheumatology.
Dr. Toby Maher
“We didn’t show it to be better, so I think you can reasonably choose between the two, but rituximab almost certainly has the advantage of being safer and better tolerated than cyclophosphamide,” Dr. Maher said in an interview. The findings were published simultaneously in The Lancet Respiratory Medicine.
Double-blind, double-dummy
RECITAL is a phase 2b, randomized, controlled trial to test the hypothesis that intravenous rituximab would be superior to cyclophosphamide for ILD-associated CTD.
The study included adults with three separate diagnoses: myositis (n = 44), mixed CTD (n = 16), and systemic sclerosis (SSc, n = 37). The study was done in the United Kingdom when Dr. Maher was with Imperial College London.
Patients in the rituximab group received 1,000 mg of IV treatment at baseline and 2 weeks, then placebo treatment every 4 weeks to week 20. Cyclophosphamide patients received 600 mg/m2 of body surface area intravenously every 4 weeks for six doses.
“When we designed this study there was limited evidence for any treatment for any disease associated with ILD,” Dr. Maher said. “But cyclophosphamide brings with it many challenges. It can be poorly tolerated and carries issues like infertility and risk of bladder cancer.”
Improved lung function
While the study failed to meet its primary endpoint – superiority of rituximab versus cyclophosphamide – it did show that both drugs led to improvement in lung function, measured by the rate of change in forced vital capacity (FVC), as well as quality of life measures, Dr. Maher said.
“Overall by week 48, we saw about a 5% improvement in FVC in the cyclophosphamide group and approximately a 4% improvement in FVC from baseline in the rituximab group, suggesting that both drugs almost certainly had a positive benefit in this patient group,” he said.
But secondary outcomes varied somewhat across the different disease groups. Patients with SSc saw a slight deterioration with cyclophosphamide in the modified Rodnan skin score at 24 weeks (1.6 ± 5.7 units) but an improvement with rituximab (–3.4 ± 8.1 units).
“One area where we did see a difference was in the number of adverse events,” Dr. Maher said. “They were fewer in the rituximab arm – namely gastrointestinal disorders [and] nausea, which we saw quite frequently following cyclophosphamide. Also, they had fewer headaches, which we saw quite frequently following cyclophosphamide.”
Rituximab patients also had fewer infusion reactions, but the number of infections was similar between the two treatment groups, he said.
“The patient group that responded best to treatment was the myositis group,” Dr. Maher said in his presentation. “Cyclophosphamide actually appears to be more effective than rituximab in improving their disease. By the end of 48 weeks, the cyclophosphamide group actually gained about 400 mL in FVC, so a close to 20% improvement.”
The rituximab group had “a little bit of a drop-off” in efficacy from weeks 24 to 48, although the trial didn’t repeat dosing at 6 months, “which is what perhaps one might do in clinical practice,” he said.
Oliver Distler, MD, chair of rheumatology at the University Hospital Zürich, raised questions about concurrent corticosteroid use in study patients that may have caused a “spillover” in the study’s efficacy analysis. But Dr. Maher noted that steroid use was balanced in all treatment arms. Patients in the cyclophosphamide arm averaged 42.9 mg of hydrocortisone daily versus 37.6 mg daily in the rituximab arm. That represents a 12.3% reduction in steroid exposure for the latter.
Dr. Distler noted that the myositis population represented the bulk of those study patients on steroids. “So in the myositis subanalysis we do see a combination of high-dose steroid plus cyclophosphamide and rituximab.”
Dr. Maher disclosed relationships with Boehringer Ingelheim, Genentech, GlaxoSmithKline, Bristol-Myers Squibb, AstraZeneca, Trevi, CSL Behring, Pliant and Veracyte. Dr. Distler disclosed relationships with numerous pharmaceutical companies.