Today is Thanksgiving in the U.S.—in the spirit of the holiday, I want to focus on a positive story about CRISPR, instead of the misadventures of He Jiankui:

“How CRISPR + GWAS (May Have) Cured Sickle Cell Disease”

Surely a story about which to be thankful. (thread) https://twitter.com/kiranmusunuru/status/1199651783708225537">https://twitter.com/kiranmusu...
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#SickleCell disease (SCD), devastating for millions and most prevalent in sub-Saharan Africa, is caused by abnormal adult hemoglobin (HbS) deforming red blood cells.

Fetal hemoglobin (HbF) functions similarly to normal adult hemoglobin.

But HbF levels fall soon after birth.
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Increased HbF improves SCD—the mechanism for SCD drug hydroxyurea.

Researchers asked if some people have genetic variants increasing HbF.

Common variant studies—genome-wide association studies (GWAS)—were more fruitful than rare variant studies.

H/t @skathire for figure.
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In 2008, @GLettre, @bloodgenes, @joelhirschhorn, Orkin & team reported that common variants in the BCL11A locus associate with HbF levels and *severity of disease* in SCD patients.

https://www.ncbi.nlm.nih.gov/pubmed/18667698 ">https://www.ncbi.nlm.nih.gov/pubmed/18...
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In 2011, Xu (of @JianXuLab), Orkin & team found in a mouse model of SCD that inactivation of BCL11A in the erythroid (red blood cell) lineage corrected the disease.

This opened the door to varied strategies to inactivate BCL11A to treat SCD patients.

https://www.ncbi.nlm.nih.gov/pubmed/21998251 ">https://www.ncbi.nlm.nih.gov/pubmed/21...
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$VRTX and $CRSP have developed a CRISPR therapy—CTX001—that edits the BCL11A erythroid enhancer in bone marrow stem cells of patients with SCD or beta thalassemia (another blood disorder in which increased HbF is beneficial).

https://clinicaltrials.gov/ct2/show/NCT03745287">https://clinicaltrials.gov/ct2/show/...
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Earlier this year, two patients—one with SCD, one with beta thalassemia—received the CRISPR therapy.

Last week, we learned that both patients have had dramatic improvements in their health. So much so, the treatment might have been a full cure. https://twitter.com/sxbegle/status/1196778144822448128">https://twitter.com/sxbegle/s...
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The SCD patient who received the CRISPR therapy had her HbF level surge to ≈50% of total hemoglobin and has had no disease attacks since. The other patient had her HbF rise to almost 100%.

I don’t think I’m exaggerating when I say this is stunning. https://twitter.com/NPR/status/1196902482858926081">https://twitter.com/NPR/statu...
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This is just the beginning. There are a variety of additional viable strategies to genetically treat SCD, including RNA interference to knock down BCL11A. https://twitter.com/AndyBiotech/status/1197520820769361921">https://twitter.com/AndyBiote...
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There are vocal detractors who bemoan the “billions” in taxpayer money spent on GWAS.

Yes, it was a lot of money.

But even if all that comes from it is a cure for sickle cell disease & beta thalassemia—IMHO that’s not so bad a return on investment.

https://www.ebi.ac.uk/gwas/diagram ">https://www.ebi.ac.uk/gwas/diag...
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There’s a happy irony that with the money mostly going to the genotyping of people of European ancestry, the biggest near-term impact of GWAS might actually be on the health of people of sub-Saharan African ancestry.

Map of sickle cell disease distribution:
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The CRISPR trial for #SickleCell is so late-breaking that I wasn’t able to include it in #TheCRISPRGeneration. On the list for the 2nd edition.

Next time, it’s back to He Jiankui: what was he hoping to achieve by editing CCR5, and did he succeed? https://twitter.com/kiranmusunuru/status/1198927090315345921">https://twitter.com/kiranmusu...
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