A wash-out duration lasting >1–2 months between the majority of sequential disease-modifying therapies (DMTs) is associated with an increased risk of disease reactivation in Multiple Sclerosis (MS) patients.
Fingolimod (FTY) induces sequestration of lymphocytes in secondary lymphoid organs and the average lymphocyte recovery following discontinuation takes 1-2 months. It has been hypothesized that the therapeutic effects of subsequent cell-depleting agents may be compromised if lymphocyte recovery is still incomplete and that shorter wash-out periods do not affect the disease reactivation risk.
To assess the risk of relapses following FTY discontinuation and the initiation of a B/T cell-depleting agent initiation in relation to the duration of wash-out between the drugs using data from the Italian MS Registry.
Patients who initiated alemtuzumab, rituximab, ocrelizumab or cladribine within six months of FTY discontinuation, and with a follow-up of at least six months, or until a relapse occurred, were included in the study. The risk of relapses was assessed in relation to different wash-out durations (<6, 6-11, 12-17 and >/=18 weeks) using a Poisson regression analysis (and reported as incidence rate ratio - IRR) and a Cox proportional hazards model including age, disease duration, relapses during FTY treatment, EDSS and reason for FTY discontinuation as covariates.
Inclusion criteria were met by 329 patients (226F, 103M; mean age 41±10 years). Following a median wash-out period of 11 weeks [IQR: 6-16], 175 patients started alemtuzumab, 69 rituximab, 68 ocrelizumab and 17 cladribine. Ninety patients relapsed during the wash-out period and 72 during the subsequent cell-depleting therapy. During the cell-depleting treatment, IRR for a relapse was significantly greater in patients with a washout-period of 12-17 (IRR (95%CI): 2.4 (1,1-5,5); p=0.037) and >/=18 weeks (6.0 (2.8-12.7); p<0.001) compared to the reference period (<6 weeks).
The multivariable Cox analysis showed that the time to a relapse was significantly influenced by the occurrence of relapses during FTY treatment (HR (95%CI): 1.4 (1.2-1.7); p<0.001). Moreover, wash-out durations of 6-11, 12-17 and >/=18 weeks were associated with a higher risk of a relapse in comparison to wash-out durations shorter than 6 weeks (3.8 (1.1-13.2); p=0.037; 6.0 (1.7-21.9); p=0.006; 16.3 (4.8-56.3); p<0.001, respectively).
The risk of relapses during a cell-depleting therapy following a sequestering agent, namely FTY, increases progressively with the duration of wash-out, underlining the need of a short wash-out period also in this type of treatment sequence.