A phase-2 trial of low-dose pomalidomide in myelofibrosis.

In a previous study, we reported on the safety and efficacy of low-dose (0.5 mg) pomalidomide and prednisone and pomalidomide alone (2 mg/day), for the treatment of anemia associated with myelofibrosis (MF). The current study examined the value of low-dose pomalidomide alone. The main eligibility criterion was transfusion-dependency or hemoglobin <10 gm per 100 ml. Anemia response was assessed by International Working Group criteria. Pomalidomide (0.5 mg/day) was given to 58 patients (median age 68 years); 46 (79%) were transfusion-dependent and 42 were JAK2V617F positive. Anemia response was documented only in the presence of JAK2V617F (24 vs 0%; P=0.03) but was not further affected by mutant allele burden (P=0.39); 9 of the 10 anemia responders became transfusion independent. Anemia response in JAK2V617F-positive patients was predicted by the presence of pomalidomide-induced basophilia in the first month of therapy (38 vs 6%; P=0.02) or absence of marked splenomegaly (38 vs 11%; P=0.05). A total of 14 (58%) of 24 patients with a platelet count of ≤ 100 × 10(9) cells/l experienced a >50% increment in platelet count. There were no spleen responses. Grade 3 or 4 thrombocytopenia/neutropenia occurred in 2%/0% of patients. Low-dose pomalidomide is effective in the treatment of anemia associated with JAK2V617F-positive MF; response is predicted by early drug-induced basophilia.