Table 1.

Criteria for ruxolitinib (RUX) failure used in recently reported clinical trials.

A. Criteria used for the re-analysis of JAKARTA-2[38] and in PAC203.[48]
Relapsed	RUX for ≥ 3 mos with regrowth (defined as < 10% SVR or < 30% decrease in spleen size by palpation from baseline following an initial response)
Refractory	RUX for ≥ 3 mos with < 10% SVR or < 30% decrease in spleen size by palpation from baseline
Intolerant	RUX for ≥ 28 days complicated by development of RBC transfusion requirement (≥ 2 units/mo for 2 mos); or grade ≥ 3 thrombocytopenia, anemia, hematoma/hemorrhage while on RUX

B. JAK inhibitor failure as defined in the IMBARK™ trial of imetelstat.[72]

➢Worsening of splenomegaly-related abdominal pain at any time after the start of JAK inhibitor therapy and EITHER:      ✤No reduction in spleen volume or size after 12 weeks of JAKi therapy, OR      ✤Worsening splenomegaly at any time after the start of JAKi therapy documented by:       • Increase in spleen volume from nadir by 25% measured by MRI or CT, or       • Increase in spleen size by palpation

Abbreviations: RUX, ruxolitinib; SVR, spleen volume reduction; mo, month; JAKi, Janus kinase inhibitor; MRI, magnetic resonance imaging; CT, computed tomography.