Umbilical cord blood has been used in transplants for more than thirty years, yet research on it continues. A cord blood transplant is an established treatment, but it has a well-known weak spot: the cells take time to engraft, and in the meantime the patient is more vulnerable to infection.
In April 2026, the Journal of Clinical Oncology published a study that tackles exactly this limitation with an experimental product called dilanubicel. To see what it means, it helps to take a step back: what cord blood is used for today, why recovery can be slow and which solutions are already approved.
What cord blood is used for today
The blood left in the umbilical cord and placenta after birth is rich in haematopoietic stem cells, the same cells that produce blood in the bone marrow. This is why it can replace bone marrow as a source of cells for transplantation.
The first cord blood transplant took place in October 1988 in Paris. The patient was a child with Fanconi anaemia, a rare bone marrow disorder, who received cord blood from a compatible sibling, collected at birth. According to a review published in 2020, more than 40,000 have been performed worldwide since then, in children and adults.
Today, a cord blood transplant is an established option for some serious blood diseases, such as leukaemia and myelodysplastic syndromes, and for some inherited bone marrow disorders. It is chosen mainly when the patient has no compatible adult donor, partly because cord blood requires a less strict genetic (HLA) match.
Haematopoietic stem cells: what they are
These cells can renew themselves and generate every type of blood cell: red cells, white cells and platelets. After the transplant they travel to the patient’s bone marrow and, within a few weeks, start producing new blood. This process is called engraftment.
When people talk about umbilical cord stem cells, a distinction is useful. Cord blood mainly contains haematopoietic cells, whereas the cord tissue contains mesenchymal cells, which differ in nature and use and are still mostly studied in research. This article is only about the former.
The limitation of cord blood transplant: few cells, slower engraftment
A cord blood unit often contains a low number of stem cells, and this can delay engraftment. The European Medicines Agency (EMA) made the same point when presenting one of the new therapies for this type of transplant.
Time matters above all for neutrophils, the white blood cells that defend the body against bacteria and fungi. Until they return to adequate levels, the patient is more exposed to infection. With a standard unit this usually takes about three weeks: in the study that led to the approval of omidubicel, discussed below, the median time was 22 days.
To increase the cell dose, especially in adults, many centres have adopted transplants with two units instead of one. It is a widespread strategy, but it means finding two compatible units.
How research is trying to speed up recovery
To shorten the wait after a cord blood transplant, research has followed two paths in recent years: multiplying the unit’s cells in the laboratory, or supporting them with temporary help that covers the first few weeks.
Multiplying cells in the lab: the products already approved
The first path is cord blood expansion: the unit’s cells are grown and multiplied in the laboratory before infusion. Two products based on this principle have already been approved.
Omidubicel, marketed as Omisirge, was approved by the US Food and Drug Administration in April 2023 for patients aged 12 and over with blood cancers who are candidates for a cord blood transplant. In the randomised study of 125 patients, neutrophils recovered in 12 days versus 22 with a standard unit (median values). Significant bacterial or fungal infections in the first 100 days fell from 60% to 39%.
In the European Union, in August 2025, the European Commission granted a conditional marketing authorisation to Zemcelpro for adults with blood cancers who need a transplant and have no other suitable donor. ‘Conditional’ means that the data are still limited: the company must provide further results, including those of a randomised study.
The path that takes a cell therapy from the laboratory to the patient follows precise rules, as we explained in our article on the requirements for advanced cell therapies.
Dilanubicel: a ‘bridge’ from several donors
The second path is different: dilanubicel does not multiply the cells of the patient’s unit but supports them temporarily.
The product is made by pooling blood progenitor cells from six to eight donated cord blood units, which are then multiplied in the laboratory. It is stored frozen, ready to use and does not require an HLA match with the patient.
These cells do not engraft permanently. They produce white blood cells for a few days, peaking around day 7, and disappear by day 14. In the meantime, the main unit has time to engraft and rebuild the patient’s immune system.
“This is the first time transplant patients received cells from what amounts to nine different human beings,” said Filippo Milano, first author of the study, which was carried out at Fred Hutch Cancer Center in Seattle.
The dilanubicel study in practice
Who took part
It is a phase 2 study, carried out at a single centre without a randomised control group. It involved 28 patients aged 10 to 63 with leukaemia or myelodysplastic syndromes who did not have a fully matched donor.
Each patient received a single cord blood unit and, a few hours later, a dose of dilanubicel. The study is registered on ClinicalTrials.gov under the code NCT03399773.
What the researchers found
- It occurred in all patients: neutrophils recovered in 18 days and platelets in 31 (median values).
- Early support. Dilanubicel cells supported white blood cell production in the first week and then disappeared, as expected.
- Graft-versus-host disease is the complication in which donor cells react against the patient’s tissues. About three in four patients had a mild acute form; none developed a severe form, either acute or chronic.
- After a median follow-up of 1.4 years, 27 of 28 patients were alive and disease-free. One patient died of causes other than relapse; another relapsed, was treated and is back in remission.
The researchers compared these results with those of patients who had previously received cord blood alone. Compared with that group, blood recovery was faster with dilanubicel and severe GVHD less frequent: in the comparison group, 26% had developed high-grade GVHD and 21% chronic GVHD.
How to read these results
These are encouraging data, but they call for caution:
- the sample is small, 28 patients, and the study took place at a single centre;
- the comparison is with patients treated in the past, not with a randomised group, so differences may also reflect other factors, such as changes in care over the years;
- dilanubicel is an experimental product, not approved by the FDA or any other regulatory authority;
- the product was supplied by the company developing it, Deverra Therapeutics, and some authors declared ties to the company.
The mechanism is not fully clear either. The authors suggest that dilanubicel may create a favourable immune environment by briefly activating T cells from the transplanted unit. Larger studies will be needed to confirm the results and understand how it works.
What this means for expectant parents
The dilanubicel study involved patients with blood cancers who received donated cord blood. The message, however, applies to everyone: research is finding ways to get more out of every unit collected. It is also a good opportunity to clarify the options available at birth.
Public donation, private or hybrid storage
There are three options, each with a different purpose:
- Public donation. The cord blood is donated to a public bank and entered in the Swiss registry of blood stem cell donors. From there it is available to any compatible patient, in Switzerland and worldwide. Donation is free of charge and the family keeps no exclusive rights to the cells. The hospitals that collect cord blood for donation are listed on the Swiss Blood Stem Cells website.
- Private storage. The family entrusts the cord blood to a private biobank under a contract. The sample remains at the family’s exclusive disposal, and the family decides how to use it: for the child or for a compatible relative, such as a brother or sister. In Switzerland this activity is regulated by the Transplantation Act and supervised by Swissmedic and the Federal Office of Public Health (FOPH).
- Hybrid storage. This is a pilot project launched in 2020 by Inselspital, Bern University Hospital, with Swiss Transfusion SRC and SSCB. The sample stays with the family but is also listed in the public registry: if a compatible patient needs it, the parents can choose to release it. Find out more about our hybrid banking model.
These options serve different purposes, and none of them is mandatory. The best decision is an informed one, discussed in good time during pregnancy with your gynaecologist or midwife.
Why collection and storage make a difference
Whatever the choice, the usefulness of a unit depends largely on how many cells it contains and how they have been handled. It is the same problem that research starts from: more viable haematopoietic stem cells generally mean faster engraftment.
That is why the quality of collection at birth, rapid transport, laboratory processing and cryopreservation all matter. These are the steps a biobank works on every day. SSCB, a biobank active since 2005, manages them in line with GMP standards and holds FACT-NetCord accreditation, one of the leading international benchmarks for cord blood banks.
In brief
- A cord blood transplant is an established treatment for some serious blood diseases, especially useful when no compatible adult donor is available.
- Its main limitation is the low number of cells, which can slow engraftment and extend the period of infection risk.
- Two products that multiply cells in the laboratory are already approved: Omisirge in the United States and Zemcelpro, conditionally, in the European Union.
- Dilanubicel is still experimental: in a phase 2 study of 28 patients it showed a good safety profile and encouraging results, which need to be confirmed by larger studies.
- Public donation, private storage and hybrid storage meet different needs, and none of them is mandatory.
Find out more
Research on cord blood moves forward step by step, and the dilanubicel study is a good example: a promising result that now needs confirmation. If you are considering what to do with your baby’s cord blood, our frequently asked questions cover the most common doubts about collection and storage.
On our blog we follow research developments, such as the five-year follow-up on cord blood in preterm infants. For specific questions, our team is happy to help.
Sources
- Milano F, Dahlberg A, Pedersen J, et al. Safety and Clinical Outcomes of Pooled Donor, Nonengrafting Expanded Progenitor Cells in Single-Unit Cord Blood Transplantation. J Clin Oncol. 2026. doi:10.1200/JCO-25-02510
- Fred Hutch Cancer Center. Umbilical cord blood transplant with pooled stem cell product shows 96% survival and no graft-versus-host-disease in leukemia patients. Press release, 27 April 2026.
- Fred Hutch Cancer Center. New cell products can improve cord blood transplant outcomes. Science Spotlight, June 2026.
- Milano F, Dahlberg A, Roberts LC, et al. Dilanubicel, a Non-HLA-Matched Pooled Universal Product, Transforming Single Cord Blood Transplantation Success Rates. Abstract, 66th ASH Annual Meeting, 2024.
