Vor Bio Announces Positive Clinical Data From Trial of Trem-cel Followed by Mylotarg in Acute Myeloid Leukaemia

Trem-cel is Vor Bio’s most advanced engineered haematopoeitic stem cell (eHSC) product candidate and is developed from healthy donor haematopoietic stem and progenitor cells (HSPCs). These cells are CRISPR-Cas9-edited to delete the CD33 gene. CD33 is a cell surface antigen that is abundantly expressed in the vast majority of AML cases, and it is one of the main validated target antigens in AML to date.

Several programmes are ongoing to target CD33 in AML, but so far gemtuzumab ozogamicin (Mylotarg™) is the only CD33-directed antibody-drug conjugate to be approved by the FDA and European Medicines Agency (EMA) for the treatment of AML. Transplant with trem-cel is anticipated to replace standard of care transplants for AML and potentially other blood cancers.

Trem-cel candidate is currently being investigated as a therapy for CD33+ AML patients at high risk of relapse after allogeneic haematopoietic cell transplantation (HCT), whereby the candidate would allow post-HCT treatment with a CD33-targeting therapy without toxicity to engrafted cells.

Positive data from 10 patients treated with trem-cel and Mylotarg

In total, 18 patients treated with trem-cel, of which ten had received Mylotarg as of the data cut-off date of July 19, 2024 were included in the latest data annoucement. Following a positive update from the VBP101 trial late last year, the latest data demonstrated reliable engraftment of trem-cel with all patients achieving primary neutrophil engraftment​ and robust platelet recovery. High CD33-editing efficiency was observed as was full myeloid chimerism, i.e., 100% of haematopoietic cells derived from the donor, 28 days post-treatment. The data also revealed that trem-cel led to effective shielding of blood cells against Mylotarg on-target toxicity, with maintained neutrophil and platelet counts across multiple Mylotarg doses of 0.5, 1, and 2 mg/m2 and an increased therapeutic index for Mylotarg. When relapse-free survival was compared to published survival rate for high-risk AML comparators, the data provided early evidence of patient benefit.

According to its press release, Vor Bio has plans to approach the FDA to discuss a pivotal trial design for trem-cel + Mylotarg sometime around the end of 2024.

We will continue to update you on the gene-editing clinical trials as new details emerge. In the meantime, can find all of our coverage on clinical-stage gene editing programmes here.

For a complete overview of current gene editing clinical trials, check out CRISPR Medicine News' Clinical Trials Database.