An ongoing open-label single arm study (6201) has characterised the incidence and severity of diarrhoea on neratinib plus intensive loperamide prophylaxis, in a similar population to study 3004 (n=137). The incidence of diarrhoea (any severity) was reduced for the loperamide cohort compared to the neratinib arm pivotal study (3004): 77.4% vs 95.4%, respectively. Regarding grade 3 or higher diarrhoea, the respective incidences are 30.7% and 39.9% for studies 6201 and 3004. The use of prophylactic loperamide also appears to reduce the cumulative duration of diarrhoea. The incidence of constipation is significantly increased for the loperamide cohort compared to the neratinib arm of study 3004: 56% versus 8%. In the loperamide cohort, 28 patients (20.4%) discontinued due to diarrhoea