MADRID – Pascal Joly, MD, PhD, reported at the annual congress of the European Academy of Dermatology and Venereology.
Not only did rituximab prove superior in terms of efficacy in the PEMPHIX trial, with a five times greater likelihood of achieving a complete remission lasting for at least 16 weeks while off oral corticosteroids than with mycophenolate mofetil in the 52-week study, but the total number of disease flares in the mycophenolate mofetil group was five times higher. Moreover, rituximab-treated patients received a markedly lower cumulative dose of prednisone as well.
“Rituximab has a superior overall benefit-risk profile, compared to mycophenolate mofetil, in patients with moderate to severe pemphigus vulgaris,” concluded, professor of dermatology at the University of Rouen (France) and president of the French Society of Dermatology.
The study was undertaken because mycophenolate mofetil is commonly used as a corticosteroid-sparing drug in patients with pemphigus vulgaris, even though its efficacy for the treatment of this rare, severe autoimmune blistering disease is unproven, he explained.
In contrast, rituximab was approved by the Food and Drug Administration and European regulators for treatment of pemphigus vulgaris on the strength of the pivotal phase 3trial – also led by Dr. Joly – which demonstrated the superiority of this intravenously administered anti-CD20 monoclonal antibody plus short-term prednisone over high-dose corticosteroid monotherapy, which for decades had been the standard treatment despite its considerable toxicity burden ( ).
An independently conducted analysis of Ritux 3 recently concluded that rituximab plus short-term prednisone was more effective than prednisone alone, with a lower risk of life-threatening, corticosteroid-related adverse events and less cumulative corticosteroid exposure ().
Also, an international panel of 93 pemphigus experts has declared that rituximab should be considered an evidence-based first-line therapy for moderate to-severe pemphigus ().
The phase 3, placebo-controlled PEMPHIX trial randomized 135 patients with moderate or severe pemphigus at 49 academic medical centers in the United States and nine other countries to double-blind rituximab or mycophenolate mofetil on top of background oral prednisone at 1.0-1.5 mg/kg per day, with the steroid to be tapered and discontinued within 4-6 months.
The primary endpoint of the study was the proportion of patients in each study arm at week 52 who had achieved a sustained complete remission lasting for at least 16 weeks while off prednisone. The rate was 40.3% in the rituximab group and 9.5% with mycophenolate mofetil, for a 383% increased likelihood of sustained complete remission in the rituximab group.
In addition, all of the study’s secondary endpoints significantly favored rituximab. The median cumulative dose of corticosteroid was 2.7 g through 52 weeks in the rituximab arm, compared with 4 g with mycophenolate mofetil. The total number of disease flares over 52 weeks was 6 in the rituximab group and 44 in the mycophenolate arm. Five rituximab-treated patients experienced disease flares, as did 26 on mycophenolate. Thus, the likelihood of a flare was seven times lower with rituximab.
Scores on the Dermatology Life Quality Index improved by an average of 8.87 points from baseline to week 52 in the rituximab group versus 6 points with mycophenolate. And 62.7% of rituximab-treated patients had a week-52 Dermatology Life Quality Index score of 0, meaning no impact of the disease on their quality of life, compared with 25% of the mycophenolate group.
Dr. Joly characterized the safety profile of rituximab as “manageable, with acceptable tolerability.” About 9% of the rituximab group and 7.4% of mycophenolate-treated patients had one or more treatment-related adverse events, a nonsignificant difference. The rate of treatment-related serious infections was 3.0% with rituximab and 2.9% with mycophenolate. Serious infusion reactions leading to study withdrawal occurred in three patients on rituximab and one on mycophenolate. The rate of grade 3 or worse corticosteroid-related adverse events was 1.5% with rituximab and significantly greater at 7.4% with mycophenolate.
An additional 48-week safety assessment beyond the 52-week primary outcome is ongoing.
Asked what future role he sees for mycophenolate in pemphigus vulgaris, Dr. Joly replied that the only study in the literature that shows the drug outperforms placebo was seriously flawed. “In the future, it’s very likely that the indications for use of mycophenolate in pemphigus vulgaris will be fewer and fewer,” the dermatologist added.
In reply to a question about the merits of routine antibiotic prophylaxis against pneumocystis carinii pneumonia in patients taking rituximab for pemphigus vulgaris, Dr. Joly said the incidence isn’t sufficiently high to justify such practice. After all, he noted, there were no cases of pneumocystis carinii pneumonia in rituximab-treated patients in PEMPHIX and only one in Ritux 3.
EADV Scientific Programming Committee Chair, professor and head of dermatology at University Hospital in Nantes, France, inquired as to whether there’s a role for maintenance therapy in a potent rituximab-based treatment strategy such as utilized in PEMPHIX.
Definitely, Dr. Joly replied. However, further study is required to work out the best maintenance program.
“There are many arguments for maintenance therapy in these patients. For one, the frequency of relapses increases with the length of follow-up. Also, anti–desmoglein-specific T cells can still be detected after rituximab therapy, even in patients in complete remission. So there is a need for maintenance therapy, perhaps at months 6, 12, and 18, but the optimal regimen isn’t determined yet,” according to Dr. Joly.
PEMPHIX was sponsored by F. Hoffmann-La Roche. Dr. Joly reported serving as a consultant to Roche, Amgen, Principia Biopharma, and Argenx.