The ALK-2 Inhibitor, TP-0184, Demonstrates High Distribution to the Liver Contributing to Significant Preclinical Efficacy in Mouse Models of Anemia of Chronic Disease

In individuals with chronic inflammatory diseases, such as cancer or rheumatoid arthritis, constitutive signaling through ALK2, a member of the bone morphogenetic protein (TGFβ/BMP) receptor family, leads to debilitating anemia, commonly referred to as anemia of chronic disease (ACD). Activation of ALK2, like other members of the BMP receptor family, leads to the phosphorylation and activation of SMAD family transcription factors via signal transduction and subsequent activation of gene expression. Activation of ALK2 in the liver induces the SMAD-driven transcription of the peptide hormone hepcidin which, by promoting the degradation of the iron transporter ferroportin, leads to reduced serum iron levels and subsequent functional anemia. Lowering constitutively elevated hepcidin levels by inhibiting ALK2 kinase activity is a potentially viable therapeutic strategy for ACD. Current therapeutic approaches for ACD rely on transfusions, intravenous iron and the use of erythropoietin-based therapies, none of which address the underlying pathological deficit of functionally low iron levels. TP-0184 is a small-molecule, selective inhibitor of ALK2 kinase activity (IC₅₀ = 5 nM). TP-0184 has demonstrated profound preclinical activity in three mouse efficacy models for ACD. In model 1, TP-0184 reversed hepcidin induction in mice treated with turpentine oil. In model 2, TP-0184 abrogated reductions in hemoglobin and total red blood cell counts induced by intraperitoneal injection with heat-inactivated Brucella abortus. In model 3, TP-0184 reversed elevated hepcidin levels in TC-1 tumor bearing mice. Plasma and liver pharmacokinetics in mice revealed that TP-0184 has a high volume of distribution (Vd = 30.8) and accumulates at high concentrations in the liver (C_max of 292 mM following a single oral dose of at 20 mg/kg). In rat multi-dose tolerability studies, TP-0184 caused no adverse effects when dosed at 200 mg/kg for 7 days, far exceeding the dose levels required to produce efficacy (25 mg/kg). These data suggest that favorable distribution to the liver may play a significant role in the preclinical efficacy of TP-0184 and provide evidence of a significant therapeutic window. Collectively these studies support the clinical evaluation of TP-0184 as an alternative treatment for ACD.