Novel Thyrointegrin αvβ3 Antagonist for the Treatment of Acute Myeloid Leukemia

Acute myeloid leukemia accounts for up to one-third of the more than 60,000 leukemias diagnosed annually in the U.S. Primary AML cells express membrane αvβ3 integrin, which is associated with adverse prognosis and resistance to chemotherapies used in AML. A macromolecule Polyethylene glycol-conjugated bi-TriAzole Tetraiodothyroacetic acid (P-bi-TAT) acts with high affinity (Ki 3.1 nM) and specificity for the thyrointegrin αvβ3 receptors, without nuclear translocation and has demonstrated effective suppression of cancer cell proliferation, NF-kB expression and invasion in leukemic cells.

We evaluated P-bi-TAT in two different AML models against two forms of acute leukemia (monocytic and myelocytic) that are largely resistant to existing therapy, by grafting human leukemia cells in immunocompromised male and female mice. IVIS imaging scans revealed that leukemic colonies were extensively established in bone marrow throughout the control (untreated) grafted animals, as well in liver, lung and kidney. Smears of bone marrow aspirates from untreated animals were found to contain multinucleate myeloblast and monoblast leukemic cells, and peripheral blood smears contained blast cells, multinucleated megakaryocytes, giant platelets and platelet aggregates, which are hallmarks of acute leukemia. IVIS imaging scans revealed 95% reduction in bone marrow colonies and resolution of liver, kidney and lung colonies in animals treated with P-bi-TAT at daily doses ranging from 1-10 mg/kg, subcutaneously for 2-3 weeks. Peripheral blood smears from treated animals were normal. Normal myeloblasts, which are the source of functional white blood cells, were found in the marrow smears, but leukemic cells were not detected in P-bi-TAT treated animals. Thus, against two forms of leukemia models, P-bi-TAT was extraordinarily effective, with the potential in treating most AML sub-types because αvβ3 receptors are expressed in the majority of AML. Among genes targeted by multiple laboratories for pharmacological downregulation of expression in AML are BCL2, VEGF, AKT1, KIT, IDH2, CDK4/6, TIMP1, VEGF, EGFR, and PD-L1. In that regard, P-bi-TAT has been shown in various tumor cell models to downregulate transcription of each of the genes listed, which are relevant to AML disease progression. Additionally, the pro-apoptotic P53 gene transcription is enhanced by P-bi-TAT.

In conclusion, P-bi-TAT is a promising lead clinical candidate that warrants clinical trials in AML patients.