To report the frequency of IRRs with alemtuzumab during the first and second cycle in patients with the standard mitigation protocol (SMP) compared with patients with the NMP in a Chilean cohort.

Alemtuzumab is approved as a highly effective therapy in relapsing remitting multiple sclerosis (RRMS) but infusion related reactions (IRRs) have being described from mild to moderate despite regular mitigation protocols (intravenous methylprednisolone and antihistamine medication), even persisting for few days after the infusion.

Ambispective study including patients from july 2015 to march 2022, comparing the frequency of IRRs with alemtuzumab receiving SMP during the infusion (intravenous methylprednisolone 1gr and intravenous chlorphenamine 10mg) compared to patients receiving the NMP added to the regular one (atorvastatin 40mg and 1 pill containing betamethasone 0.25mg plus dexchlorfeniramine 2mg every 8 hours, 2 weeks prior the infusion and 2 weeks after the infusion). Statistical test: Chi-square to compare frequencies with association.

25 patients were included, 52% males and 48% females, mean age was 33.72 + 9.80 years. Regarding comorbidity, only 1 patient had high blood pressure. SMP was used in 13 patients and NMP in 12 patients. We analyzed the data comparing the occurrence of IRRs during the first and second cycle. During the first cycle, 13 patients had IRRs using the SMP compared with 6 patients that experienced IRRs with the NMP (p = 0.003). During the second cycle, 10 patients had IRRs using the SMP compared with 4 patients that experienced IRRs with the NMP (p = 0.013). 

The NMP decreases the occurrence of IRRs during the first and second cycle of alemtuzumab compared to the SMP. Larger cohorts are needed to reduce biases and to analyze the impact of the NMP during third or fourth cycle or the impact in other infusion related reactions that are less frequent.