1810
A 40-year-old man with relapsing-remitting multiple sclerosis (MS) developed primary central nervous system lymphoma (PCNSL) after having received 21 doses of natalizumab monotherapy.
 ( adverse event: developed ,  40-year-old man with relapsing-remitting multiple sclerosis (MS): Subject, 40-year-old: Subject.Age, man: Subject.Gender, primary central nervous system lymphoma (PCNSL): Effect, 21 doses of natalizumab monotherapy: Treatment, relapsing-remitting multiple sclerosis (MS): Treatment.Disorder, 21 doses: Treatment.Dosage, natalizumab: Treatment.Drug) 
Locate the role in the text that participated in the event based on the event type and return it in the event list. 
 Option: Event type: adverse event,potential therapeutic event, Arguments type: Treatment.Disorder,Treatment.Time_elapsed,Treatment.Dosage,Subject.Race,Treatment.Drug,Treatment.Route,Subject.Disorder,Treatment.Freq,Treatment,Effect,Subject.Population,Treatment.Duration,Combination.Drug,Subject,Subject.Age,Subject.Gender. 
Text: {0} 
Answer:
 ( adverse event: developed ,  40-year-old man with relapsing-remitting multiple sclerosis (MS): Subject, 40-year-old: Subject.Age, man: Subject.Gender, primary central nervous system lymphoma (PCNSL): Effect, 21 doses of natalizumab monotherapy: Treatment, relapsing-remitting multiple sclerosis (MS): Treatment.Disorder, 21 doses: Treatment.Dosage, natalizumab: Treatment.Drug) 