7 ms·

The article was skimpy on the details. Can someone explain how this part works? > The new gene therapy [...] works by inserting into the body working copies o

by SamBam 4y ago

The article was skimpy on the details. Can someone explain how this part works? > 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?

amelius 4y ago
Also, when cells replicate, will the new ones automatically be of the edited type? Or is it not that simple?
- ethanwillis 4y ago
  In general it depends. If you modified existing blood cells genotype then it wont persist indefinitely. You'd need to modify the bone marrow. But then some cell lines work like you posed in your question.
- MaryBall 4y ago
  Because this therapy edits the stem cells that are found in the bone marrow, it essentially means that the disease is being fixed at the source. Bone marrow stem cells eventually turn into blood cells and immune cells. So if 100% of the cells have been edited, then the resulting cells they turn into will be the edited type.
- janeway 4y ago
  That is the goal but not that simple. 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.
herlitzj 4y ago
https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(21)02017-1/fulltext https://www.thelancet.com/journals/lancet/article/PIIS0140-6... 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.
MaryBall 4y ago
Yes, you’re right! A lentiviral vector is used to insert the working gene into the patient’s stem cells. Obviously this is a non-pathogenic version of the virus, so it’s ability to make you ill has been essentially “switched off”. However the ability for the virus to insert genetic information into the DNA of cells remains.
bglazer 4y ago
Yes, it's a virus, specifically a lentivirus, which inserts its own genome into the cells DNA, including the therapeutic gene. Looks like they first extract bone marrow from a patient, apply the virus which adds the gene, then they put the "fixed" bone marrow cells back into the patient (probably after killing most existing bone marrow through some really unpleasant procedures). The re-inserted, treated cells then expand and begin making new cells that have inherited the fixed gene. 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.
- meese712 4y ago
  I'm confused how this would reduce disease progression compared to a much cheaper allo bone marrow transplant then if they are only modifying hematopoietic stem cells since a BMT is just doing the exact same thing except with someone else's non affected cells. BMTs are a horrific procedure though so this definitely has an advantage in that regard. 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.
  - theGnuMe 4y ago
    Well it removes graft vs host complications which is a win and the requirement to take immunosuppressants for life.
    - meese712 4y ago
      Definitely true GVHD sucks. The article gave me the impression that they were saying it was somehow superior at stopping the disease because it said this "stem cell transplants, have sometimes been used to slow the disorder's progression in infants," (fyi a decent amount of stem cell transplant survivors do not have to take immunosuppressants for life)
Traubenfuchs 4y ago
In this specific case CRISPR-CAS9 was used to edit "hematopoietic stem and progenitor cells". This means all modified stem cells (sadly not 100% of them) will from now on produce cells with the gene bugfix applied. 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. https://pubmed.ncbi.nlm.nih.gov/34882002/ https://pubmed.ncbi.nlm.nih.gov/34882002/
deleted 4y ago
[deleted]

by SamBam 4y ago

amelius 4y ago

Also, when cells replicate, will the new ones automatically be of the edited type? Or is it not that simple?

ethanwillis 4y ago
In general it depends. If you modified existing blood cells genotype then it wont persist indefinitely. You'd need to modify the bone marrow. But then some cell lines work like you posed in your question.
MaryBall 4y ago
Because this therapy edits the stem cells that are found in the bone marrow, it essentially means that the disease is being fixed at the source. Bone marrow stem cells eventually turn into blood cells and immune cells. So if 100% of the cells have been edited, then the resulting cells they turn into will be the edited type.
janeway 4y ago
That is the goal but not that simple. 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.

herlitzj 4y ago

https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(21)02017-1/fulltext https://www.thelancet.com/journals/lancet/article/PIIS0140-6... 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.

MaryBall 4y ago

Yes, you’re right! A lentiviral vector is used to insert the working gene into the patient’s stem cells. Obviously this is a non-pathogenic version of the virus, so it’s ability to make you ill has been essentially “switched off”. However the ability for the virus to insert genetic information into the DNA of cells remains.

bglazer 4y ago

Yes, it's a virus, specifically a lentivirus, which inserts its own genome into the cells DNA, including the therapeutic gene. Looks like they first extract bone marrow from a patient, apply the virus which adds the gene, then they put the "fixed" bone marrow cells back into the patient (probably after killing most existing bone marrow through some really unpleasant procedures). The re-inserted, treated cells then expand and begin making new cells that have inherited the fixed gene. 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.

meese712 4y ago
I'm confused how this would reduce disease progression compared to a much cheaper allo bone marrow transplant then if they are only modifying hematopoietic stem cells since a BMT is just doing the exact same thing except with someone else's non affected cells. BMTs are a horrific procedure though so this definitely has an advantage in that regard. 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.
- theGnuMe 4y ago
  Well it removes graft vs host complications which is a win and the requirement to take immunosuppressants for life.
  - meese712 4y ago
    Definitely true GVHD sucks. The article gave me the impression that they were saying it was somehow superior at stopping the disease because it said this "stem cell transplants, have sometimes been used to slow the disorder's progression in infants," (fyi a decent amount of stem cell transplant survivors do not have to take immunosuppressants for life)

Traubenfuchs 4y ago

In this specific case CRISPR-CAS9 was used to edit "hematopoietic stem and progenitor cells". This means all modified stem cells (sadly not 100% of them) will from now on produce cells with the gene bugfix applied. 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. https://pubmed.ncbi.nlm.nih.gov/34882002/ https://pubmed.ncbi.nlm.nih.gov/34882002/

deleted 4y ago

[deleted]