Real-World Treatment Patterns in Patients with Mycosis Fungoides or Sézary Syndrome Treated with Mogamulizumab in the United States: A Retrospective Database Analysis

Background: Mycosis fungoides (MF) and Sézary syndrome (SS) are rare and heterogenous non-Hodgkin lymphomas that primarily involve the skin but can also involve blood, lymph nodes, and/or internal organs. Mogamulizumab is a defucosylated humanized anti-CCR4 antibody that was approved in the United States for the treatment of patients with relapsed or refractory MF or SS based on the results of the randomized phase 3 MAVORIC study (NCT06113081). Research into how mogamulizumab is used in the real-world setting can provide insight into optimal treatment patterns for MF and SS patients. The current analysis described real-world patient characteristics and treatment patterns in clinical practice.

Methods: This retrospective cohort study analyzed data from mogamulizumab-treated patients in the ConcertAI Oncology electronic health records database of community and academic practices from across the United States that included patient demographics, clinical characteristics, and treatment patterns. MF or SS patients were included if they received treatment lasting for ≥28 days between October 1, 2018 and August 12, 2022. Use of mogamulizumab was characterized as a single agent or as a combination with other systemic therapies and/or skin-directed therapies (excluding topical steroids). Combination therapy was defined as ≥28-day concomitant treatment with mogamulizumab. Duration of treatment was measured from its initiation until the last dose. If there was a gap in mogamulizumab treatment of >90 days, it was considered retreatment.

Results: 104 mogamulizumab-treated patients were identified and analyzed (50 with MF, 54 with SS). Median (Q1, Q3) age at start of mogamulizumab treatment was 69.0 (60.0, 77.0) years and 56.7% of patients were male. Median (Q1, Q3) duration of follow-up was 20.0 (10.9, 32.3) months. 51 patients (49.0%) were treated in academic centers; 46 (44.2%) treated in community hospitals (data missing for 7 patients [6.7%]). The majority of patients (87 [83.7%]) were treated by hematologists/oncologists; 2 (1.9%) by dermatologists; 15 (14.4%) by other/unknown specialists. 20 patients (19.2%) had stage IA-IIA at initial diagnosis, 44 (42.3%) IIB-IV, 40 (38.5%) missing. Stage at the time of mogamulizumab initiation was missing for 77 (74.0%) patients.

Median (Q1, Q3) time from initial diagnosis to initiation of mogamulizumab was 38.0 (10.9, 84.7) months, with 69 patients (66.3%) having ≥2 systemic therapies prior to mogamulizumab (20 [19.2%] had only 1 prior therapy). 77 patients (74.0%) initiated mogamulizumab due to disease progression or poor response to prior therapy, 9 (8.7%) due to adverse events to prior therapy, 4 (3.8%) due to blood involvement, 3 (2.9%) due to other reasons and 11 (10.6%) were undocumented. 93 patients (89.4%) had continuous treatment and 11 (10.6%) had an interruption in treatment followed by retreatment with mogamulizumab. 75 patients (72.1%) received mogamulizumab as a monotherapy, and 29 (27.9%) receiving a combination. Among those patients on combination therapy (n=29), 14 patients (48.3%) had mogamulizumab added to pre-existing therapy; 7 (24.1%) had mogamulizumab initiated as combination therapy, and 8 (27.6%) had subsequent add-on therapy on Day 61 or later of mogamulizumab initiation. Median (Q1, Q3) duration of therapy in all patients was 5.7 (3.0, 12.3) months. For monotherapy vs combination therapy, it was 5.2 (2.8, 9.9) months vs 10.1 (3.9, 20.4) months (Mann-Whitney U test, 2-sided p-value=0.015). The most common systemic therapy options for combination (n=29) were bexarotene (8 [27.6%]), extracorporeal photopheresis (7 [24.1%]), and methotrexate (6 [20.7%]).

Conclusions: This study showed the duration of mogamulizumab treatment (5.7 months) was similar in the real world compared to the results observed in the MAVORIC clinical trial (5.7 months). The duration of mogamulizumab treatment was longer in patients receiving combination treatment than those on monotherapy and warrants further investigation.