Effective imaging and treatment of Acute Myeloid Leukemia with radiotheranostics targeting the activated conformation of integrin-βeta2

Abstract

There remains an unmet clinical need for improved treatment strategies in Acute Myeloid Leukemia (AML). Although radiopharmaceutical therapies targeting non-cancer-selective antigens have shown promise in AML, their clinical utility is often limited by prolonged bone marrow suppression. Using a unique proteomics-based strategy, we recently identified the active conformation of integrin-β2 (aITGB2) as a novel, tumor-selective target for AML. Importantly, this conformational epitope is expressed widely on AML cells but minimally on normal marrow progenitors/healthy tissues. Here we first confirmed widespread aITGB2 expression on AML tumors that was largely independent of tumor genotype or prior therapeutic regimen. We developed diagnostic and therapeutic radiopharmaceuticals targeting aITGB2 utilizing a conformation-specific antibody (clone 7065). PET/CT imaging with ⁸⁹ Zr and ¹³⁴ Ce-labeled 7065 in AML models revealed high target-mediated uptake, greater than that compared to standard of care [ ¹⁸ F]-FDG. PET/CT imaging with [ ⁸⁹ Zr]DFO*-7065 showed reduced binding to normal bone marrow and immune cells in humanized immune system mice compared to [ ⁸⁹ Zr]DFO*-anti-CD33. For therapy, we developed [ ²²⁵ Ac]Macropa-PEG ₄ -7065 using an optimized chelator-linker combination. Treatment with [ ²²⁵ Ac]Macropa-PEG ₄ -7065 in Nomo-1 and PDX AML disseminated models delayed tumor growth and improved overall survival compared to controls, including [ ²²⁵ Ac]DOTA-anti-CD33, a clinical stage-radioimmunotherapy under evaluation in AML. Relapsed tumors demonstrated persistent aITGB2 expression, supporting continued development of fractionated dosing schemes, and proteomics analysis indicated activation of TCA cycle and carbon metabolism pathways, consistent with therapy-induced stress responses. These findings highlight [ ⁸⁹ Zr]DFO*-7065 and [ ²²⁵ Ac]Macropa-7065 as a promising aITGB2-targeted theranostic pair with potential for imaging and treatment in future clinical translation.

One sentence summary: This study demonstrates promising preclinical efficacy of aITGB2-targeted radiotheranostics for selective imaging and therapy in AML.