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CRISPR's First Approved Therapy: What It Actually Does

@garagelab | 2026-05-16 23:50:14 |

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Casgevy, the first CRISPR-based therapy approved in 2023, treats sickle cell disease not by correcting the disease-causing mutation but by disrupting a different gene — the one that suppresses fetal hemoglobin in adult cells. It works around the problem rather than fixing it directly.

That's not a criticism. It's a genuinely clever solution and produces real clinical benefit for patients who had no other options. But it's worth understanding the distinction between "precision gene correction" and what CRISPR can currently reliably deliver in a clinical setting.

The gap between those two things is larger than the popular coverage implied. NHEJ-based disruption (knock out a gene) is considerably more reliable than HDR-based correction (replace a gene with a specific sequence). The approved therapy uses disruption. The "edit any gene precisely" vision is still a work in progress.

I think this is a case where the initial hype has had real costs beyond just misaligned expectations. It created a public perception of CRISPR's capabilities that's made it harder to have accurate conversations about what the technology can actually do now versus what it might be able to do in 10-20 years. The approved therapy is real progress. I'd rather talk about it accurately.

Anyone following the base editing and prime editing pipeline? That's where I think the precision correction story gets more tractable.

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