Development of a gene edited next-generation hematopoietic cell transplant to enable acute myeloid leukemia treatment by solving off-tumor toxicity

• Published in: Molecular therapy. Methods & clinical development Vol. 31; p. 101135
• Main Authors: Lydeard, John R., Lin, Michelle I., Ge, Huanying Gary, Halfond, Amanda, Wang, Shu, Jones, Mark B., Etchin, Julia, Angelini, Gabriella, Xavier-Ferrucio, Juliana, Lisle, Jessica, Salvadore, Kienan, Keschner, Yonina, Mager, Hannah, Scherer, Julian, Hu, Jianxin, Mukherjee, Siddhartha, Chakraborty, Tirtha
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 14.12.2023
• Subjects: acute myeloid leukemia; CD33; CRISPR-Cas9; genome engineering; hematopoietic stem cell; immunotherapy; IND-enabled; pharmacology/toxicology; acute myeloid leukemia; CRISPR-Cas9; immunotherapy; hematopoietic stem cell; IND-enabled; pharmacology/toxicology; CD33; genome engineering
• ISSN: 2329-0501; 2329-0501
• DOI: 10.1016/j.omtm.2023.101135

Immunotherapy of acute myeloid leukemia (AML) has been challenging because the lack of tumor-specific antigens results in “on-target, off-tumor” toxicity. To unlock the full potential of AML therapies, we used CRISPR-Cas9 to genetically ablate the myeloid protein CD33 from healthy donor hematopoietic stem and progenitor cells (HSPCs), creating tremtelectogene empogeditemcel (trem-cel). Trem-cel is a HSPC transplant product designed to provide a reconstituted hematopoietic compartment that is resistant to anti-CD33 drug cytotoxicity. Here, we describe preclinical studies and process development of clinical-scale manufacturing of trem-cel. Preclinical data showed proof-of-concept with loss of CD33 surface protein and no impact on myeloid cell differentiation or function. At clinical scale, trem-cel could be manufactured reproducibly, routinely achieving >70% CD33 editing with no effect on cell viability, differentiation, and function. Trem-cel pharmacology studies using mouse xenograft models showed long-term engraftment, multilineage differentiation, and persistence of gene editing. Toxicology assessment revealed no adverse findings, and no significant or reproducible off-target editing events. Importantly, CD33-knockout myeloid cells were resistant to the CD33-targeted agent gemtuzumab ozogamicin in vitro and in vivo. These studies supported the initiation of the first-in-human, multicenter clinical trial evaluating the safety and efficacy of trem-cel in patients with AML (NCT04849910). [Display omitted] Lydeard and colleagues describe an approach to genetically engineer treatment-resistant hematopoietic stem cells (HSCs) to enable potentially curative targeted therapy post-transplant. Here they present the preclinical assessment and scale-up process that supported the ongoing first-in-human clinical trial of tremtelectogene empogeditemcel (engineered HSCs lacking the CD33 protein) in patients with AML.