Background

As the number of available therapies in MS increases, knowledge about how to safely switch between therapies is increasingly important. Real world data can provide safety and efficacy data on switching that is not likely to be provided through randomised controlled trials.

Both ocrelizumab, an anti B cell therapy, and cladribine, a selective lymphocyte depleting agent, are highly effective therapies and have recently been licenced around the world for treatment of RRMS. There is no previously published data on the safety and tolerability of the switching between these two therapies.

Objectives

To characterise lymphocyte profile and immunoglobulin levels following initiation of cladribine oral tablets in patients switched from ocrelizumab and to evaluate short term safety profiles in this cohort.

Methods

A cohort of 20 patients with MS from a single centre in Australia were identified who had been switched from ocrelizumab to cladribine. Patients received a cumulative dose of 1.75 mg/kg over 2 treatment weeks. Absolute lymphocyte count (ALC) was recorded at a number of time points. Safety and tolerability data were reviewed.

Results

TThe average ALC at baseline, Month 2, 4, 7 and 12 were 1.6, 1.0, 0.75, 1.1 and 1.0 x10⁶ respectively. No cases of grade 4 lymphopenia were recorded. All ALCs were greater or equal to 0.6 x10⁶ at month 7. The average IgG level at the end of ocrelizumab was 8.56 g/L and 12 months after starting cladribine was 9.19 g/L which was statistically higher (p=0.007). No serious adverse effects were recorded.

Conclusions

Data from this cohort has not revealed any safety concerns switching from ocrelizumab to cladribine. Seven months after starting cladribine the average ALC had returned to the lower limit of normal. Twelve months after switching from ocrelizumab to cladribine the average IgG level had increased.