050 Late onset recurrent neutropenia following ocrelizumab therapy in multiple sclerosis

Ocrelizumab, an anti-CD20 monoclonal antibody similar to rituximab, has demonstrated efficacy in relapsing(RR) and primary progressive MS. Late onset neutropenia (LON) is a rare side-effect of rituximab and there only 2 cases reported related to ocrelizumab. We discuss 2 treatment naive patients with active RRMS who developed LON after ocrelizumab treatment.A 31y female presented with neutropenic sepsis 115 days after third ocrelizumab infusion, requiring treatment with intravenous antibiotics and granulocyte colony stimulating factor (G-CSF). Subsequent multiple episodes of recurrent grade 4 neutropenia occurred over the next 6 months, often requiring G-CSF treatment. Bone marrow aspiration demonstrated normocellular granulopoiesis.A 35y male developed neutropenic sepsis 119 days after first ocrelizumab infusion which recovered rapidly with G-CSF. He received the second dose of ocrelizumab 3 months later, and at 5 months follow up after his third infusion had no recurrent neutropenia.The two cases demonstrate the spectrum of late onset neutropeniaof LON with oOcrelizumab. The aetiology of LON is poorly understood but hypothesised to be autoimmune in nature. The cases are important to raise the clinical suspicion of this life threatening complication of disease modifying therapy. Further experience is required to understand risk of recurrence and when to re-challenge with ocrelizumab.maryam.talaei@wales.nhs.uk