New age HCT conditioning regimens: what works and why?

Conditioning regimens play an essential role in allogeneic transplantation by facilitating engraftment and eradicating malignancies. The landscape of conditioning regimens has undergone an evolution in the concept of intensity. Novel conditioning strategies aim to provide highly efficacious regimens with improved toxicity profiles. Integrating disease- specific chemotherapy and targeted agents into conditioning regimens provides enhanced disease elimination and relapse prevention. Agents like treosulfan provide safer conditioning with a favorable toxicity profile for patients with older age or medical comorbidities and can lower the incidence of long-term complications for younger patients. Additionally, methodologies for precise and targeted radiation delivery with minimal off-target effects are emerging. A promising development is radioimmunotherapy-based regimens that preferentially deplete hematopoietic cells and spare nonhematopoietic tissues. These advancements necessitate reexamination and harmonization of conditioning intensity stratification schemes for a more personalized and selective approach.