Until now, the problem this newsletter has covered has been treatments that should not exist: unproven, overstated, sold to people who had no way to assess what they were buying. Issue 7 is about a different problem. A treatment that genuinely works, backed by rigorous clinical evidence, approved by the FDA, capable of eliminating the central burden of a devastating inherited disease. It costs $2.2 million per patient. Fewer than 50 centres in the United States can administer it. The people most likely to need it are the least likely to reach it. Approval, it turns out, is only the beginning of the problem.

Sickle cell disease is inherited. A single mutation in the gene that produces haemoglobin causes red blood cells to form in a crescent shape instead of the smooth, flexible disc that moves freely through blood vessels. These misshapen cells break down faster than normal, block circulation, and trigger episodes of severe pain - vaso-occlusive crises - that accumulate over a lifetime into organ damage, stroke, and shortened life expectancy. Approximately 100,000 Americans live with the condition. The disease disproportionately affects Black patients, who have historically received less research investment and face greater structural barriers to specialist care.

Until recently, the only potential cure was a bone marrow transplant. It required a matched donor, was available to roughly one in four patients, and carried significant risks of its own.

In December 2023, the FDA approved Casgevy - the first therapy ever to use CRISPR-Cas9 gene editing in humans. The treatment modifies the patient's own blood stem cells: they are harvested, edited in a laboratory to activate a genetic switch that prompts the body to produce foetal haemoglobin instead of the defective adult form, and reinfused. The stem cell component is what places this within the field this newsletter covers. The gene editing is what makes it unlike anything that came before.

The clinical data is real. In the pivotal trial, 28 of 29 patients with severe sickle cell disease had no serious vaso-occlusive events for at least 12 consecutive months following treatment. A separate analysis found that 93.5% of patients receiving Casgevy experienced no such events in the months after treatment. These are not marginal findings. For patients who have spent their lives managing crises that hospitalise, disable, and compound over decades, this is a meaningful clinical result.

The price is $2.2 million per patient. Its companion therapy, Lyfgenia, which uses a different gene modification approach and the same stem cell delivery mechanism, is priced at $3.1 million. Both require months of preparation before treatment begins, including procedures to collect stem cells and chemotherapy conditioning to clear the patient's bone marrow. The full process involves multiple hospital stays extending over weeks. Fewer than 50 treatment centres in the United States have the infrastructure to administer either therapy.

The Centers for Medicare and Medicaid Services launched the Cell and Gene Therapy Access Model in 2024, now active across 33 states, covering approximately 84% of Medicaid beneficiaries with sickle cell disease. States negotiate prices with manufacturers and reimbursement is tied to outcomes. That solves the financing problem for one payer group. It does not move the treatment centres, and it does not reach patients whose insurance sits outside Medicaid. Sickle cell disease is most prevalent in the American South and in urban centres with high Black populations. The capable centres are not where the patients are.

It does not address geography, clinical capacity, or patients whose insurance sits outside Medicaid entirely. Sickle cell disease is most prevalent in the American South and in urban centres with high Black populations. The distribution of capable treatment centres does not yet reflect that geography.

The broader lesson will apply to every expensive cell or gene therapy that follows. The pathway from laboratory to patient requires manufacturing infrastructure, clinical capacity, payer frameworks, and geographic access. Casgevy established that the science can be ready. The two years since have shown that readiness is not sufficient.

Pivotal trial - Casgevy (exagamglogene autotemcel), published in the New England Journal of Medicine, 2021 and updated through FDA review, 2023

Vertex Pharmaceuticals and CRISPR Therapeutics enrolled patients with severe sickle cell disease characterised by recurrent vaso-occlusive crises. Each patient's blood stem cells were harvested, edited using CRISPR-Cas9 technology to reactivate foetal haemoglobin production, and reinfused following chemotherapy conditioning.

Study type: Single-arm, open-label; human patients, no control group

Sample size: 29 patients in the pivotal analysis

What they found: 28 of 29 patients had no severe vaso-occlusive crises for at least 12 consecutive months following treatment. Foetal haemoglobin levels rose substantially in all treated patients and remained elevated through follow-up.

Most important caveat: Single-arm with no concurrent control group. Long-term durability beyond the trial follow-up period is not yet established. The chemotherapy conditioning required before treatment carries its own risks, including effects on fertility. Sample size is small, though consistent with trials in rare disease populations.

Why it matters anyway: This is the first therapy to use CRISPR gene editing in approved clinical practice. The results were sufficiently compelling for FDA approval in a condition where the unmet need is severe and the alternatives are limited. It is the evidence standard — hard-won, honestly limited, genuinely meaningful.

CRISPR-Cas9 is a gene editing tool borrowed from bacterial biology. In practical terms, a protein called Cas9 acts as molecular scissors, guided to a precise location in a cell's DNA by a strand of RNA designed to match it. Once there, it cuts. The cell's own repair mechanisms do the rest.

In Casgevy, CRISPR does not replace the defective haemoglobin gene. It disables a suppressor gene - one that blocks the production of foetal haemoglobin, a form that functions normally regardless of the sickle cell mutation. Disabling that suppressor lets foetal haemoglobin re-emerge, compensating for the defective version.

Earlier gene therapies delivered corrective genes into cells using viral vectors. CRISPR edits the existing DNA directly. The distinction matters for precision and for the scope of what future therapies - including some in the iPSC pipeline - may eventually be able to do.

The disease has always been there. The research took decades longer than it should have, in part because the people who carry it were not the people the research system was built around. The cure arrived in 2023. In 2026, the question is who gets to find out.