Acute myeloid leukemia: therapeutic targeting of stem cells

Introduction: Despite advances in the treatment of acute myeloid leukemia (AML), long-term survival remains low. In 1994, it was proposed that leukemic stem cells (LSCs) played a key role in relapsed and refractory disease. LSCs are capable of self-renewal, proliferation, differentiation, immune evasion, and drug resistance through several unique mechanisms. More recent leukemia drug development initiatives have included efforts to target LSCs. With LSCs, the challenge with such drug design is finding a way to selectively target LSCs while sparing normal hematopoietic stem cells (HSCs). Areas covered: In this review, we explore the evolving knowledge of the unique LSC biology and physiology in the scientific literature, while noting the several agents that have been designed throughout the years to target this subgroup of leukemic cells. Our review includes discussion on chimeric antigen receptor T cells, monoclonal antibodies, antibody-drug conjugates against cell surface markers, signaling pathway targets, pro-apoptotic agents, epigenetic regulators, and more. Expert opinion: As our understanding of the intricate pathophysiology of LSCs continues to grow, it is clear that targeting such heterogenous cells successfully will require a thoughtful and multi-modal approach.