620
Prolonged responses were achieved with low doses of HU (3-10 mg/kg/day) and higher doses were associated with mild reversible hematologic or hepatic toxicity and no further increases in Hb.
 ( adverse event: associated ,  mild reversible hematologic or hepatic toxicity and no further increases in Hb: Effect, HU (3-10 mg/kg/day) and higher doses: Treatment, HU: Treatment.Drug, higher doses: Treatment.Dosage) 
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: associated ,  mild reversible hematologic or hepatic toxicity and no further increases in Hb: Effect, HU (3-10 mg/kg/day) and higher doses: Treatment, HU: Treatment.Drug, higher doses: Treatment.Dosage) 