Correction of polycythemia vera via CRISPR/AAV6 genome editing

[PT99]

Not sure about the technical details but this seems like it may be a promising development.

techfinder.stanford.edu/tec...

[EPguy]

It is a new way to uncloak the Jak2 mutation, still very early in vitro only (no mouse tests etc yet)-

The patent application describes it in more detail.

patentscope.wipo.int/search...

This part of the 1st claim is the essential step:

"the RNA-guided nuclease cleaves a mutant JAK2V617F gene in the genome of the cell but does not cleave a wild-type JAK2 gene in the genome of the cell"

This means they found away to "uncloak" the mutated genes. Once the v617f location is exposed the gene can be cleaved, or broken apart, at this location. Then familiar CRISPR methods can be used to modify the mutation. (with many novel techniques required no doubt)

They are not addressing Exon 12 mutations, but presumably this technique should work there too.

As in prior discussions, Jak2 mutations have resisted direct targeting for lack of a way to expose them. This has also apparently been solved by Incyte with INCB160058 with a sort of greatly improved Rux:

healthunlocked.com/mpnvoice...

It seems the Jak2 mutation's days of hiding from us are numbered.

In contrast CALR is exposed on the cell surface, vs hidden inside, and Cell therapies are under way to take advantage of that exposure.

[Bluetop in reply to EPguy]

Thanks for the further explanation!

[Spanelmad in reply to EPguy]

Thanks for explaining in plain English!! Actually understood

[Bluetop]

Thanks for posting. Interesting.

[saltmarsh]

Yes. Many thanks for this post.

[Manouche]

 »The safety of using CRISPR/AAV6 genome editing for correcting polycythemia vera (PV) is still under investigation. Here are some key points to consider:

1. **Precision and Specificity**: The CRISPR/Cas9 system is designed to target specific DNA sequences, which helps minimize off-target effects. In the case of PV, researchers have developed methods to specifically target the JAK2 mutation while preserving the normal allele¹.

2. **In Vitro Success**: Initial experiments in human hematopoietic stem cells (HSCs) have shown promising results, with efficient correction of the JAK2 mutation and minimal impact on the wild-type allele¹. This suggests a high level of precision and potential safety in a controlled laboratory setting.

3. **Ongoing Research**: The procedure is still in the research phase, with ongoing in vivo studies to further assess its safety and efficacy¹. These studies are crucial to understanding the long-term effects and potential risks when applied in a clinical setting.

4. **Potential Risks**: As with any gene-editing technology, there are potential risks, including unintended genetic changes, immune responses to the viral vector, and the possibility of incomplete correction leading to mixed cell populations¹.

Overall, while the initial results are promising, more research is needed to fully establish the safety and effectiveness of this approach for treating PV. If successful, it could offer a groundbreaking, curative treatment option for patients. »

(1) Correction of polycythemia vera via CRISPR/AAV6 genome editing. techfinder.stanford.edu/tec....

(2) Polycythemia vera: 2024 update on diagnosis, risk‐stratification, and .... onlinelibrary.wiley.com/doi....

(3) Correction of polycythemia vera via CRISPR/AAV6 genome editing. techfinder.stanford.edu/pri....

[EPguy in reply to Manouche]

One detail not yet clear is what a clinical procedure would be. I have a feeling this requires an SCT (marrow transplant) to install the repaired genes as the current sickle cell CRSPR does. If so most ET, PV pts likely would not qualify if current therapy is working and stable, esp if VAF is low and/or declining on the conventional therapy. Then the risk trade off for SCT would be a factor. The new Incyte drug I noted could then have a risk advantage since it is a simple pill that treats the mutation inside the body. But if they can make this CRSPR an IV or shot that could open it to more MPN pts.

[Manouche in reply to EPguy]

Yes, you are correct.

« The clinical procedure for correcting polycythemia vera (PV) using CRISPR/AAV6 genome editing would likely involve a stem cell transplant (SCT), similar to the approach used for sickle cell disease.

Here's a more detailed outline of the potential clinical procedure:

1. **Collection of Hematopoietic Stem Cells (HSCs)**: The patient's own HSCs would be collected, typically from the bone marrow or peripheral blood.

2. **Ex Vivo Gene Editing**: The collected HSCs would be edited outside the body (ex vivo) using the CRISPR/Cas9 system to target and correct the JAK2 mutation. The AAV6 vector would deliver the normal donor template to repair the gene through homologous recombination¹.

3. **Conditioning Regimen**: The patient would undergo a conditioning regimen, which may include chemotherapy or radiation, to create space in the bone marrow for the edited HSCs and to suppress the immune system to prevent rejection.

4. **Transplantation of Edited HSCs**: The corrected HSCs would then be infused back into the patient. These edited cells would ideally engraft in the bone marrow and start producing healthy blood cells, effectively curing the disease¹.

5. **Monitoring and Follow-Up**: Post-transplant, the patient would be closely monitored for engraftment success, potential complications, and long-term efficacy of the treatment.

This approach aims to provide a one-time, curative treatment by permanently correcting the genetic defect in the patient's own stem cells¹. However, it's important to note that this procedure is still in the research phase, and further studies are needed to fully establish its safety and effectiveness.

¹: [Stanford's Porteus Lab - Correction of Polycythemia Vera via CRISPR/AAV6 Genome Editing](techfinder.stanford.edu/tec...

(1) Correction of polycythemia vera via CRISPR/AAV6 genome editing. techfinder.stanford.edu/tec....

(2) Polycythemia vera: 2024 update on diagnosis, risk‐stratification, and .... onlinelibrary.wiley.com/doi....

(3) Treatment and clinical endpoints in polycythemia vera: seeking the best .... ashpublications.org/blood/a....

[EPguy in reply to Manouche]

This SCT would have one large advantage over the SCT we know. The description matches autologous (from your own marrow) as is sickle cell therapy. This contrasts with allogenic (from a donor) that MPN SCTs are now. So the risk of rejection should be vastly lower, thus substantially reducing the risk.

[MPNBlog]

Thank you for keeping us informed. It maybe quite a way off, but it is good to know that someone is working on a way of helping us. So often I feel as if there are so few of us affected by MPNs, it isn't worth the research time and money to come up with solutions that won't make a lot of money for research companies. And thanks for the expanded explanations.