INCB018424, a Selective JAK1/2 Inhibitor, Significantly Improves the Compromised Nutritional Status and Frank Cachexia in Patients with Myelofibrosis (MF).

BACKGROUND: MF is a progressive illness associated with cachexia and weight loss (Mesa et al, Cancer2007;109: 68). These clinical signs, resulting from both hypercatabolism (secondary to increased pro-inflammatory cytokines) and MF associated splenomegaly, are associated with decreased survival (Dupriez et al., Blood1996;88:1013). Currently, there is no therapy that decreases the progressive cachexia of MF. INCB018424 is a selective JAK1/2 inhibitor which has the potential to improve both the aberrant myeloproliferation in MF through decreasing constitutively active JAK-STAT signaling, and nutritional status by decreasing both splenomegaly and the pathologically increased cytokines. METHODS: Symptomatic patients with MF enrolled in a phase I/II trial (www.ClinicalTrials.gov, NCT00509899) with INCB018424, were analyzed for the impact of therapy on nutritional status and cachexia. Specifically, in addition to traditional endpoints of IWG-MRT response (reported elsewhere) patients were assessed for changes in body mass index (BMI), serum cholesterol values, spleen size, and patient reports of early satiety and anorexia. Additionally, leptin, an adipose-derived protein hormone that plays a key role in regulating energy balance and circulates at levels proportional to body fat in health and disease (Mantovani et al, J Mol Med2001; 79:406), was assessed serially. RESULTS: Patients: Thirty four MF patients, treated for at least 2 months with 25 mg twice daily of INCB018424, were included in this analysis. Among this group 85% demonstrated splenomegaly (median 20 cm below left costal margin, range 4 cm to 32 cm; 2 patients had prior splenectomy) and had a median BMI of 24.8 (range 17.9 to 49.7). Although the median BMI at baseline would be considered in the “normal range” (18.5–24.9), loss of lean body mass at enrollment would be underestimated by the contribution of splenomegaly or edema. Appetite: At enrollment, a clearly positive correlation between the presence of anorexia and early satiety (by patient’s report) and significant splenomegaly was observed. Treatment with INCB018424 led to resolution of the symptoms of poor appetite and early satiety, along with the reduction in splenomegaly. Weight: MF patients on therapy initially lost weight, which reflects resolution of excess extravascular water (based on investigators reported decreases in peripheral edema, ascites, or splenomegaly). As the trial progressed MF patients on INCB018424 treatment progressively gained weight (mean increase of 0.40 kg @ 1 month, 2.93 kg @ 2 mo, 3.70 @ 3 mo), and exhibited improved appetite. Importantly, weight gain was more consistent, of greater magnitude and more durable in patients who entered the study in the lowest quartile for BMI. Cholesterol: We previously reported that hypocholesterolemia (total cholesterol <150 or 100 mg/dL; HDL < 60mg/dL) is associated with decreased survival in MF patients (Mesa et al, Blood2007; 2007;110:a2548), potentially from hypercatabolism and splenic consumption of lipids. At enrollment, median total cholesterol was 95 mg/dl (range), with 94% and 55% below 150 mg/dl and 100 mg/dl, respectively. Following treatment with INCB018424, median total cholesterol increased to 145 mg/dl (range 72–289 mg/dL) with 73% increasing to an improved range above their baseline (either to the >100mg/dl or >150 mg/dl range). Leptin: At enrollment, MF patients had very low leptin levels (mean = 2.55 ng/mL with 50% below 1 ng/mL vs. a range of 6–12 ng/mL for normal volunteers). Low plasma levels are associated with shortened survival in cancer patients. The plasma leptin levels increased 176% on average after one month of treatment with INCB018424, and continued to increase to levels matching healthy volunteers with time on study (mean = 7.04 ng/mL (range 0.25 – 35 ng/mL) after 2 months on INCB018424) and correlated to weight increases. CONCLUSIONS: Therapy with INCB018424 improves the nutritional status of MF patients, including improving pathologic weight loss, hypercatabolism associated hypocholesterolemia, and pathologically decreased serum leptin. The improved nutritional status of MF patients treated with INCB018424 may reflect the ability of JAK inhibition to target the underlying pathophysiology of MF cachexia by reducing the organomegaly, levels of pro-inflammatory cytokines, and pro-inflammatory cytokine signaling.