Duration of spleen size reduction measured by palpable spleen length, or MRI/CT-imaged volume for patients enrolled at MDACC in study INCB18424-251. (A) The duration of a ≥ 50% reduction in palpable spleen length was estimated using the Kaplan-Meier method based on the 61 patients who exhibited a confirmed ≥ 50% reduction in palpable spleen length. The horizontal axis represents the time from onset of response. Patients could begin responding at any time; therefore, “weeks from onset” does not correspond to weeks in the study. Twenty-eight of 61 patients lost the response (date of first observation of spleen length reduction < 25% from baseline) before the analysis date. The median duration of response was estimated to be 166 weeks. (B) The duration of a ≥ 35% reduction in spleen volume was estimated using the Kaplan-Meier method based on the 17 patients who had a ≥ 35% reduction from baseline. The horizontal axis represents the time from onset of response. Patients could begin responding at any time; therefore, “weeks from onset” does not correspond to weeks in the study. Seven of 17 patients lost the response (defined by the first date with < 10% reduction from baseline) before the analysis date. The median duration of response was estimated to be 93 weeks, but note this estimate was based on few events in a small population.