Phase 1/2 Study of Oral TP-0184 for the Treatment of Anemia in Adults with Low- or Intermediate-Risk Myelodysplastic Syndromes

Patients with anemia due to lower-risk myelodysplastic syndromes (MDS) have limited treatment options. The transforming growth factor β (TGF-β) pathway has been implicated in contributing to ineffective hematopoiesis in patients with MDS. Members of the TGF-β superfamily include activin receptor-like kinase 2 (ALK2) and ALK5. ALK2 signaling plays a key role in modulating hepcidin, an important regulator of iron homeostasis (and thus erythropoiesis). Increased levels of hepcidin have been linked to anemia in patients with chronic inflammation and cancer, including multiple myeloma (Maes K, et al. Blood. 2010;116:3635-44). The role of hepcidin in MDS-related anemia is unknown and needs to be explored. ALK5 signaling through SMAD2/3 phosphorylation is constitutively active in bone marrow precursor cells from patients with MDS (Zhou L, et al. Blood. 2008;112:3434-43). Inhibition of ALK5 suppresses phosphorylation of SMAD2 in MDS hematopoietic progenitor cells and stimulates hematopoiesis in cells derived from patients with MDS. Collectively, these data suggest that blockade of the TGF-β-SMAD2/3 signaling pathway with an ALK5 inhibitor has the potential to benefit patients with anemia due to MDS.

TP-0184 is a small-molecule, dual inhibitor of ALK2 and ALK5. In vitro, TP-0184 inhibits downstream signaling from ALK2 by reducing the phosphorylation of SMAD1/5/8 and blocks hepcidin expression (Peterson PW, et al. Blood. 2017;130 [suppl_1]: 937). Ex vivo, TP-0184 inhibits downstream signaling from ALK5 by reducing SMAD2/3 phosphorylation (data on file). By inhibiting both the ALK2 and ALK5 signaling pathways, TP-0184 may reduce ineffective erythropoiesis in patients with MDS.

An open-label, single-arm, phase 1/2 study (NCT04623996) is being undertaken to evaluate the preliminary safety and efficacy of TP-0184 in treating anemia in adults (aged ≥18 years) with MDS. To be eligible, patients must have low- or intermediate-risk MDS (de novo or secondary) per the Revised International Prognostic Scoring System and have relapsed, exhibited an inadequate response to, or been refractory, resistant, or intolerant to treatment with an erythropoiesis-stimulating agent. Patients may have low or high red blood cell transfusion burden, must exhibit adequate major organ function, and must have an Eastern Cooperative Oncology Group performance status of 0-2. Key exclusion criteria include the presence of concomitant severe cardiovascular disease, such as congestive heart failure, myocardial infarction, angina, and/or uncontrolled cardiac arrhythmia; history of stroke, deep venous thrombosis, or pulmonary or arterial embolism; presence of clinically significant anemia due to iron, vitamin B12, or folate deficiencies, autoimmune or hereditary hemolytic anemia, or gastrointestinal bleeding; and prior allogeneic or autologous stem cell transplant.

In this study, TP-0184 will be administered orally once daily for 24 weeks. The primary and secondary endpoints of each study phase are summarized in the table. Recruitment is ongoing, with approximately 30 patients targeted for enrollment in phase 1 and 10-60 patients targeted for enrollment in phase 2. In phase 1, increasing dose levels of TP-0184 ranging from 20 to 270 mg will be evaluated, with 1-6 patients dosed at each level. Dose escalation will be performed using a two-parameter Bayesian logistic regression model. Determination of the recommended phase 2 dose (RP2D) will be informed by the maximum tolerated or maximum administered dose in phase 1. In phase 2, the efficacy of TP-0184 at the RP2D will be monitored using Bayesian posterior probability to optimize enrollment with Bayesian stopping rules. Bayesian monitoring of responses will be started after the first 10 enrolled patients are evaluable for efficacy.

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