Characterization and Outcomes in Patients with Mogamulizumab-Associated Skin Reactions in the MAVORIC Trial

Background

MAVORIC was a phase 3, open-label, multi-center, randomized controlled trial that evaluated the safety and efficacy of mogamulizumab compared with vorinostat in patients with relapsed/refractory mycosis fungoides (MF) or Sézary syndrome (SS) (NCT01728805). Mogamulizumab-associated rash was the second most common TEAE of any cause or grade in the mogamulizumab treatment arm and the most common TEAE leading to treatment discontinuation, resulting in a discontinuation rate of 7% (13/184). Grade 1-2 and 3 drug rashes occurred in 20% (36/184) and 4% (8/184) of mogamulizumab-treated patients, respectively. The objectives of this analysis were to describe histopathological and other characteristics of drug rash in patients who received mogamulizumab in MAVORIC.

Methods

In MAVORIC, 372 patients were randomized 1:1 to receive either intravenous mogamulizumab at 1.0 mg/kg once weekly for Cycle 1 (28 days) and then on days 1 and 15 of subsequent cycles or oral vorinostat at 400 mg daily. Confirmed overall response rate (ORR; complete response + partial response) was based on a global composite response involving all four disease compartments and verified at two consecutive visits. Guidance to investigators was provided in the protocol for evaluation and management of new drug rash on mogamulizumab treatment. Patients with an initial Grade 1 drug rash were allowed to continue treatment with use of topical steroids as needed. For patients with Grade ≥2 drug rash, mogamulizumab was temporarily stopped, and treatment of the drug rash with topical steroids was advised. Use of systemic steroids was prohibited during the study. Treatment could resume if the drug rash resolved to Grade ≤1 within 2 weeks. Biopsies were evaluated by an on-site pathologist, and a central blinded review was also conducted.

Results

This analysis included 44 patients who were treated with mogamulizumab and experienced drug rash during MAVORIC. Pathologically, central review assessed rashes as granulomatous, histiocytic spongiotic, lichenoid, eosinophilic, psoriasiform, or a combination of these patterns with no clear predominant histological pattern. Among the 44 patients with drug rash, 59.1% (26/44) were ≥65 years of age, and more patients with SS [56.8 (25/44)] than MF [43.2% (19/44]) experienced drug rash. Median (Q1, Q3) exposure among patients with drug rash was 344 days (162, 652) in patients with SS and 185 days (85, 463) in patients with MF. Mogamulizumab did not result in any cases of anaphylaxis or SJS/toxic epidermal necrolysis (TEN). Concomitant or immediate prior CTCL therapies that may make patients prone to drug rash were examined, and no trend toward increased incidence of drug rash was observed with any particular agent or class. The proportion of SS responders with drug rash was significantly higher than responders without rash (P=0.02; Figure 1); the proportion of MF responders with drug rash did not differ from responders without rash (P=0.21). Overall, the median (Q1, Q3) time to onset of drug rash was 106 days (36, 254). Initial drug rash occurred after response to mogamulizumab in 70% (14/20) of patients who experienced both. Thirty-five patients (80%) in the drug rash cohort resumed treatment with mogamulizumab upon resolution of initial drug rash per-protocol. After these patients resumed treatment, the median (Q1, Q3) duration of exposure to mogamulizumab was 183 days (58, 332).

Conclusions

Mogamulizumab-associated rashes displayed heterogeneous histopathology without one predominant feature; therefore, close correlation of suspected drug rash with clinical features is advised to differentiate it from disease progression. A trend toward higher rate of drug rash was observed in patients with SS, the group more likely to respond to mogamulizumab. Therefore, drug rash may be attributable to increased exposure, but rash may also involve underlying disease characteristics or treatment-induced immune alterations; further investigations are warranted. Nevertheless, the observation that 80% of patients on trial were able to continue mogamulizumab for >6 months following resolution of their initial rash suggests that appropriate evaluation, identification, and management of these reactions may prevent premature discontinuation.