Among patients undergoing standard myeloablative umbilical cord blood transplantation (UCBT), omidubicel may improve neutrophil and platelet recovery while reducing time in hospital, according to research published in Blood. Omidubicel does not, however, appear to improve overall survival rates vs those seen with standard UCB.

Among adult patients undergoing allogeneic hematopoietic stem cell transplantation, umbilical cord blood has been an essential source of stem cells for the past several decades. This source is, furthermore, especially important for non-White patients, who remain underrepresented in donor registries.

There is, however, evidence that adult UCBT may be linked with both transplant-related morbidity and mortality. UCBT is also associated with delayed hematopoietic recovery.

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Cell-line studies suggest that ex vivo expansion of UCB before transplantation may help to mitigate the issues associated with UCBT. Omidubicel, a patient-specific product, is made up of an expanded CD133-positive fraction and a non-expanded CD133-negstive fraction, and is derived from 1 UCB unit.

For this randomized phase 3 study, researchers compared the safety and efficacy of myeloablative allogeneic stem cell transplantation using omidubicel vs that of standard UCB grafting. The study’s primary endpoint was length of time to neutrophil engraftment.

Overall, 125 patients were enrolled and randomly assigned to the omidubicel group (62 patients) or the standard UCB group (63 patients). In the omidubicel and standard UCB groups, 30 (48%) vs 23 (36%) patients were female, respectively, the median ages were 40 vs 43 years, 35 (57%) vs 37 (59%) patients were White, and 27 (43%) vs 33 (52%) had a primary acute myeloid leukemia diagnosis, which was the most common primary diagnosis in the overall cohort.

Analysis showed that the median time to engraftment in the omidubicel vs standard UCB groups was 12 vs 22 days (P <.001); the cumulative neutrophil engraftment incidence was 96% vs 89%.

Patients in the omidubicel arm had, furthermore, a higher rate of platelet recovery by 42 days (55% vs 35% in the standard UCB group; P =.0028), as well as a lower rate of first grade 2 or 3 bacterial/invasive fungal infections (37% vs 57%, respectively; P =.027).

Patients in the omidubicel group were also more likely to spend a small proportion of their first 100 post-transplant days outside of the hospital (61 days vs 48 in the standard UCB group; P =.005).

Among patients who proceeded to transplant, however, the rates of graft vs host disease were not significantly different (56% with omidubicel vs 43% with standard UCB; P =.18). Overall survival rates were, furthermore, not significant different between the 2 groups (hazard ratio with omidubicel vs standard UCB, 0.57; P =.09).

“Hematopoietic recovery following omidubicel transplantation was faster, reduced early transplant-related complications and reduced number of days hospitalized as compared to standard UCBT,” the authors wrote. “The results of this trial demonstrate that omidubicel represents a major therapeutic advance and should be considered as a new standard of care for adult patients eligible for UCBT.”

Disclosure: The study author(s) declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures. 


Horwitz ME, Stiff PJ, Cutler CS, et al. Omidubicel versus standard myeloablative umbilical cord blood transplantation: results of a phase III randomized study. Blood. Published online June 22, 2021. doi:10.1182/blood.2021011719