From 'First in Human' Studies to Enduring Advances
"The Goal is to Put Ourselves Out of Business"
Stem cell transplantation is the transfer of human stem cells from outside a patient's body into the patient. A complex procedure with many variations and possible complications, it is often used for treating an array of life-threatening blood cancers, while the potential in treating other diseases is being explored.
The National Heart, Lung, and Blood institute (NHLBI) is conducting first in human research studies at the NIH Clinical Center exploring combinations of stem cell sources (bone marrow, circulatory system blood and umbilical cord blood) with different degrees of human leukocyte antigen matching (leukocytes are a type of molecule found on the surface of most cells that play an important part in the body's immune response to foreign substances), often depending on whether the donor cells are from a related or unrelated person.
Dr. Richard Childs, a rear admiral and assistant surgeon general in the United States Public Health Service Commissioned Corps, is the clinical director of NHLBI's Division of Intramural Research and serves as the principal investigator on an experimental stem cell study that began five years ago. The study is examining the effectiveness of transplanting a large number of ex vivo expanded umbilical cord blood stem cells into patients with treatment refractory severe aplastic anemia with a goal of decreasing the high incidence of transplant rejection that occurs with conventional cord blood transplants.
"Ideas for studies like this generally are formed from things learned in prior research, then often refined in the lab, and sometimes animal testing, before they are considered for first-in-human studies" said Childs.
After five years, results have been positive for most of the first 11 patients treated in the study, including 10 who have had sustained engraftment. Seeing numerous advantages over transplants using conventional non-expanded cord blood, Childs's team has observed a much quicker return of the white blood cells that protect patients from bacterial infection and faster restoration of the immune system, which is temporarily deactivated through chemotherapy treatments prior to the stem cell transplant to prevent graft rejection.
Research on the trial slowed due to COVID-related delays and interruptions.
"We'll need to transplant about five more patients in this study until we have numbers that are sufficient to have confidence in reporting safety, engraftment, recovery and survival [rates]," stated Childs.
The current goals for Childs' team are maximizing benefits of stem cell transplantation for blood cancers, while minimizing the risks of transplant rejection, post-transplant infections due to a recovering immune system, complications posed by viral activity, and graft-versus-host-disease (GVHD) in which the transplanted cells view their new environment as foreign and go on the attack against it.
"We're seeing much improvement with this new transplant approach with a reduction in all these complications" said Childs.
"We have Food and Drug Administration-approved drugs to treat GVHD that we didn't have 20 or 25 years ago, as well as better drug therapy against infections and viruses. A very common virus called Cytomegalovirus (CMV) is cause for concern."
Once infected with CMV, the body retains the virus for life. It rarely causes problems in healthy people but can be dangerous if your immune system is weakened.
"CMV used to be one of the biggest contributors to mortality after a transplant. Now we have medications that completely prevent CMV from reactivating in 85% of patients."
Looking ahead, Childs is enthusiastic about the several primary goals for advancing the field: finding effective combinations of stem cell sources and donor types, thereby expanding patient eligibility for some cell transplants; working towards better engraftment results; and reducing the common complications of rejection, infection and viral challenges.
"In a very real way, we'd like to see a day when stem cell transplants are less prevalent. If asked about the ultimate goal of our research, we'll say it's is to put ourselves out of business! But this really just means reaching a stage where many patients - despite how far we have come - don't have to endure the very real and time-consuming challenges of the conventional stem cell transplantation process - pre-transplant conditioning, uncertainty in outcomes, and potential post-transplant complications that in the worst-case scenario can be fatal," said Childs.
- Robert Burleson