Real-world Use of Mogamulizumab Among Patients With Mycosis Fungoides and Sézary Syndrome Before and During COVID-19 in the United States.

Purpose: During the coronavirus disease 2019 (COVID-19) pandemic, professional organizations suggested extending dosing intervals for systemic cancer therapies to limit in-person visits. Mogamulizumab, indicated for adults with relapsed or refractory mycosis fungoides (MF) or Sézary syndrome (SS) after ≥1 prior systemic therapy, should be administered every 7 days of the first 28-day cycle (loading) and every 14 days of each subsequent cycle (maintenance) according to the approved prescribing information in the United States (US). This study examined the real-world use of mogamulizumab before and during the COVID-19 pandemic in the US.

Methods: Using Symphony Health's Integrated Dataverse (IDV) database, adults with ≥1 diagnosis of MF or SS and ≥1 mogamulizumab claim between October 1, 2018 and December 22-, 2022 were identified. Patients in MF and SS cohorts were divided into 3 subgroups based on the date they initiated mogamulizumab treatment: pre-COVID-19 (October 1, 2018-March 31, 2020), COVID-19 Phase 1 (April 1, 2020-July 31, 2021), and COVID- 19 Phase 2 (August 1, 2021-December 22, 2022).

Findings: During the study, 270 patients with MF and 337 patients with SS initiated mogamulizumab. The pre-COVID-19, COVID-19 Phase 1, and COVID-19 Phase 2 subgroups included 95, 81, and 94 patients with MF and 124, 119, and 94 patients with SS, respectively. In the MF cohort, mean loading dosing intervals were 13, 12, and 9 days for the pre-COVID-19, COVID-19 Phase 1, and COVID-19 Phase 2 subgroups, respectively, and mean maintenance dosing intervals were 16, 16, and 16 days, respectively. In the SS cohort, mean loading dosing intervals were 16, 11, and 11 days, and mean maintenance dosing intervals were 19, 18, and 16 days, respectively. For both cohorts, more patients in the COVID-19 Phase 1 and Phase 2 subgroups than in the pre-COVID-19 subgroup had gaps of ≤10 days between loading doses and ≤21 days between maintenance doses.

Implications: In patients with MF and SS, loading dosing intervals in the pre-COVID-19 period were longer than the loading schedule per the approved prescribing information, but there was a trend towards closer concordance in the COVID-19 periods. Maintenance dosing intervals in patients with MF were consistently similar to the approved schedule across treatment periods, and in patients with SS became more closely aligned over time. Thus, dosing intervals for mogamulizumab in both loading and maintenance cycles do not appear to have been extended during the COVID-19 Phase 1 and Phase 2 periods compared with the pre-COVID-19 period, despite recommendations to extend dosing intervals for systemic cancer therapies during COVID-19.