Pemphigus relapse linked with PDAI score, anti-DSG antibody values

Initial score on the Pemphigus Disease Area Index and evolution of anti-desmoglein antibody values 3 months after an initial cycle of rituximab are associated with short-term pemphigus relapse, according to a post hoc analysis of a randomized clinical trial published in JAMA Dermatology.

“The presence of at least one of the two factors associated with relapse of pemphigus may help identify a group of patients with high risk for relapse who may benefit from a maintenance infusion of rituximab at month 6,” Claire Mignard, MD, of the department of dermatology at Rouen University Hospital, Normandie University, in Rouen, France, and colleagues wrote.

Data were obtained from 44 patients in the rituximab group of the RITUX 3 trial and from three patients with newly diagnosed pemphigus who underwent first-line treatment with rituximab. Those with newly diagnosed pemphigus received one infusion of 1,000 mg of intravenous rituximab on days 0 and 14 with one infusion of 500 mg rituximab combined with prednisone (0.5 mg/kg daily for moderate pemphigus and 1 mg/kg daily for severe pemphigus) at months 12 and 18.

Clinical data and pemphigus severity were recorded from patient case report forms and medical files. Pemphigus Disease Area Index (PDAI) score was used to assess baseline disease severity, and anti-desmoglein (DSG) antibody values were measured through a DSG enzyme-linked immunosorbent assay.

Eleven patients (23%), two with pemphigus foliaceus and nine with pemphigus vulgaris, experienced relapse in the 12 months after the initial infusion of 2 g rituximab.

More severe disease occurred in patients with relapse compared with those who did not relapse (P = .03). Severe pemphigus occurred in six of the 11 patients with disease relapse (55%) compared with five of the 36 patients who did not relapse (14%; P = .01).

A baseline PDAI score of 45 or higher had a positive predictive value of 55% for relapse occurrence during the 12 months after the initial rituximab treatment. A baseline PDAI score less than 45 had a high negative predictive value (86%) for the absence of a relapse.

At baseline, mean anti-DSG1 values were 257 IU/mL, then decreased to 20 IU/mL at 3 months 3 and 7 IU/mL at 6 months, according to the researchers. Similarly, mean anti-DSG3 values decreased from baseline to month 3 (850 IU/mL vs. 88 IU/mL) and month 6 (850 IU/mL vs. 38 IU/mL).

“Assuming that a maintenance infusion of rituximab at month 6 would be consistently effective, our results suggest the possibility of treating two patients with a maintenance infusion of rituximab at month 6 to avoid relapse in one patient,” the researchers wrote. “Conversely, the 94% negative predictive value indicates that a maintenance infusion of rituximab could be avoided in approximately half of the patients treated with first-line therapy.” – by Erin T. Welsh

Disclosures: Mignard reports no relevant financial disclosures. Please see the study for all other authors’ relevant financial disclosures.