In most cases, the original disease-causing stem cells are effectively eliminated by the conditioning regimen (high-dose chemotherapy and/or radiation) used before the (autologous) transplantation, so they do not regenerate and cause further harm to the patient. However, in some cases, residual disease cells may survive the conditioning regimen and persist after transplantation, leading to disease relapse. This is more likely to occur in patients with aggressive or refractory disease or in those who receive a mismatched or haploidentical donor graft. To prevent disease relapse, post-transplantation maintenance therapy, such as immunosuppressive drugs or targeted therapies, may be used to eliminate residual disease cells. Additionally, close monitoring of the patient's blood counts and immune system function can help identify and manage any signs of disease relapse.
This paper seems to have more details on the actual procedure
Patients were treated and monitored according to the schedule described in the appendix (p 17) and as previously reported.16, 17 HSPCs harvested from bone marrow or mobilised peripheral blood (MPB) were transduced with clinical-grade lentiviral vector encoding human ARSA cDNA under the control of the human phosphoglycerate kinase gene promoter.
In general, gene therapy is probably most useful currently for diseases that affect the bone marrow (and the eyes), because these are two tissues where you can precisely deliver the virus. It's still challenging to control where the virus goes and which cells it infects if you just inject it straight into the bloodstream.
I would also have to imagine they would have to do myeloablative chemo or radiation to make sure the fixed cells propagate more than the diseased cell line.
Edit: read the study, they do give them the same chemo used for normal transplants.
(fyi a decent amount of stem cell transplant survivors do not have to take immunosuppressants for life)
https://ashpublications.org/blood/article/104/12/3501/89040/...
>Previous studies have shown that 30% to 70% of all patients surviving beyond 100 days after HCT require treatment for chronic GHVD,2,4-6 often for more than 2 years.
Re: a better system is where you don't need donors:
https://www.cbsnews.com/newyork/news/l-i-woman-dies-after-ma...
One of my friends gave his wife a kidney which allowed her to get off dialysis, so yeah, thanks to anybody who is willing to do this for someone they don't even know.
Hmm...
How does this translate to other places? E.g. can you only match Han in China?
Do Italians and Scots match? Turks and Egyptians?
What matters isn't really the proportion of the subpopulations that are registered, but the absolute numbers.
What's horrific to me is that matching by race is still a thing! These genes are under diversifying selection. That means that they often do not match the surrounding genetic background. That means that racially driven matching is bonkers.
This does not imply that germ line cells were changed and COULD mean the person could still have a high risk of making children with the original gene defect.
> The new gene therapy [...] works by inserting into the body working copies of the genes that are faulty in MLD, thus restoring the ability to break down sulfatides.
How does the new copy of the gene get into every existing cell that needs it? A virus?