In December 2023, the United Kingdom’s Medicines and Healthcare products Regulatory Agency authorized a therapy called Casgevy for the treatment of sickle cell disease, making it the first medicine based on CRISPR gene editing to receive regulatory approval anywhere in the world. Days later, the U.S. Food and Drug Administration followed suit, approving Casgevy for sickle cell disease and, in January 2024, for transfusion-dependent beta thalassemia. A decade after Jennifer Doudna and Emmanuelle Charpentier published the foundational CRISPR-Cas9 paper — work that earned them the 2020 Nobel Prize in Chemistry — gene editing had become a medicine.
How Casgevy Works
Casgevy, developed by Vertex Pharmaceuticals and CRISPR Therapeutics, treats sickle cell disease by editing a patient’s own blood stem cells. Sickle cell disease is caused by a mutation in the HBB gene that produces abnormal haemoglobin, causing red blood cells to deform into a rigid, sickle shape that blocks blood flow and causes severe pain, organ damage, and shortened life expectancy.
Rather than repairing the faulty gene directly, Casgevy takes a clever indirect route. It disables a regulatory gene called BCL11A, which normally switches off production of foetal haemoglobin after birth. By turning BCL11A off in the patient’s stem cells, the therapy reactivates production of foetal haemoglobin — a form that does not sickle. The edited cells are then reinfused into the patient, where they repopulate the bone marrow with red blood cells that resist sickling.
The process is intensive. Patients undergo chemotherapy to clear out their existing bone marrow, receive the edited cells, and spend weeks in hospital. In clinical trials, the vast majority of patients were free of severe pain crises for extended periods — a dramatic result for a disease that had few good options short of a risky bone marrow transplant.
Lyfgenia and the Broader Field
The FDA simultaneously approved a second sickle cell therapy, Lyfgenia, developed by bluebird bio. Lyfgenia uses a different approach — a lentiviral vector to deliver a modified gene rather than CRISPR editing — but shares the ex vivo stem cell model. Regulatory approval of two therapies in the same month signalled that gene therapy for blood disorders had crossed a threshold.
Beyond sickle cell, CRISPR Therapeutics and other firms are pursuing therapies for beta thalassemia, certain cancers, and autoimmune conditions. Intellia Therapeutics has advanced in vivo editing — editing genes directly inside the body — with early clinical results for transthyretin amyloidosis, a condition caused by a misfolded protein. Editas Medicine, Beam Therapeutics, and Verve Therapeutics are pursuing base editing and prime editing, newer techniques that make precise changes without cutting both DNA strands, potentially reducing unintended effects.
The Cost Problem
The science is remarkable. The economics are brutal. Casgevy’s list price in the United States was set at $2.2 million per patient, with Lyfgenia at $3.1 million. Even accounting for the fact that a one-time cure may be cheaper than a lifetime of managing a chronic disease, such prices strain insurers and public health systems.
Manufacturing is a major cost driver. The therapy is personalised: each batch is made from a patient’s own cells, edited in a specialised facility, tested, and returned. There are no economies of scale in the traditional sense. Improving manufacturing efficiency — reducing the cost of the editing process and the required hospitalisation — is a central focus.
Access is also geographically uneven. The specialised centres capable of administering these therapies are concentrated in wealthy countries. Sickle cell disease disproportionately affects people of African descent and is most prevalent in sub-Saharan Africa, where the infrastructure for such treatment barely exists. A cure that cannot reach the people who need it most is a partial victory.
Ethical and Safety Questions
CRISPR therapies that edit somatic cells — the body’s ordinary cells — are broadly accepted, because changes are not inherited. The far more contested frontier is germline editing, which alters embryos or reproductive cells and passes changes to future generations. The 2018 case of He Jiankui, a Chinese scientist who edited twins’ embryos and was subsequently imprisoned, remains a cautionary tale. Most scientists and regulators support a moratorium on heritable human editing, though the international governance remains fragmented.
Off-target effects — unintended edits elsewhere in the genome — remain a safety concern, though improved guide RNA design and newer editing techniques have reduced the risk. Long-term monitoring of treated patients will be essential.
What Comes Next
The pipeline is broadening. Base editing allows a single DNA letter to be changed without a double-strand break; prime editing can insert, delete, or replace sequences with greater precision. In vivo delivery — using lipid nanoparticles or viral vectors to edit cells inside the body — would eliminate the need for harvesting and reinfusing cells, transforming the cost structure.
If in vivo editing matures, CRISPR could move from rare blood disorders to common conditions: high cholesterol, cardiovascular disease, and eventually more complex diseases. The ambition is enormous, and the timeline will be measured in years, not months.
The Canadian Context
Canada has a stake in this field. Canadian researchers contributed to early CRISPR work, and the country’s health system — with its single-payer structure — faces a distinctive challenge in deciding how to fund multi-million-dollar one-time therapies. The Canadian Agency for Drugs and Technologies in Health has begun assessing them, and the answers will shape whether these cures reach patients or remain theoretical options.
The Delivery Challenge
Even if the cost problem were solved, delivery remains formidable. Casgevy and Lyfgenia require mobilising a patient’s stem cells, editing them in a specialised laboratory, and reintroducing them after myeloablative chemotherapy — a punishing regimen that destroys the existing bone marrow and carries real risks of infection and infertility. Patients spend weeks in hospital. Only a limited number of medical centres worldwide are equipped to administer these therapies, and the training and infrastructure requirements are substantial. Scaling access means scaling this entire apparatus, which is far harder than scaling a pill.
In Vivo Editing: The Real Prize
The cost and complexity of ex vivo therapy — harvesting, editing, and reinfusing cells — is precisely why researchers are chasing in vivo editing, in which the editing machinery is delivered directly into the body. Lipid nanoparticles, the same technology used in mRNA vaccines, can be engineered to target specific organs, particularly the liver. Intellia Therapeutics has shown that in vivo CRISPR can reduce the production of a disease-causing protein in transthyretin amyloidosis, with results durable enough to suggest a one-time treatment. If in vivo delivery can be extended to more tissues, it would slash the cost and complexity of gene editing and open the door to treating common diseases.
Base and Prime Editing
CRISPR-Cas9 cuts both DNA strands, and the cell’s repair of that cut is imperfect, occasionally producing unwanted changes. Two newer techniques reduce this risk. Base editing chemically converts one DNA letter into another without breaking the double helix, allowing precise correction of point mutations. Prime editing, developed by David Liu’s lab, uses a modified Cas9 fused to a reverse transcriptase to write new sequences directly, with even greater precision. Both are further from the clinic than Casgevy but advance quickly. They represent the field’s move from crude cutting to precise rewriting.
The Patent Wars
The commercial history of CRISPR has been shadowed by one of the bitterest patent disputes in modern biotechnology. The Broad Institute of MIT and Harvard and the University of California, Berkeley (with the University of Vienna and Emmanuelle Charpentier) fought for years over foundational CRISPR patents, with rulings in different jurisdictions going different ways. The dispute affected licensing, investment, and the competitive landscape for companies built on the technology. It is a reminder that scientific credit and commercial rights in a transformative field can become deeply entangled.
Regulatory and Ethical Frontiers
Somatic editing — altering a patient’s own body cells — is broadly accepted and regulated like other advanced therapies. Germline editing, which changes heritable DNA, is prohibited in most countries and widely condemned after the He Jiankui affair. But oversight is uneven, and the technology’s power invites misuse. As costs fall and capabilities grow, the governance gap becomes more dangerous. International norms exist but lack enforcement teeth; a rogue actor in a permissive jurisdiction could act with far-reaching consequences. Building credible, coordinated oversight without crippling legitimate research is one of the defining science-policy challenges of the decade.
What Patients and Payers Need to Know
For patients with sickle cell disease and beta thalassemia, the approval of Casgevy is genuinely transformative news — a potential one-time cure after a lifetime of pain, hospitalizations, and shortened life expectancy. But access depends on far more than regulatory approval. Patients need to be at a qualified centre, be medically eligible for the conditioning regimen, and have insurance or public coverage that pays. In Canada, provincial health plans and the pan-Canadian Pharmaceutical Alliance will negotiate coverage and pricing. The history of expensive cell and gene therapies suggests that access will be uneven and slow to materialise. The scientific breakthrough and the practical reach are very different questions, and the field will be judged on both.
Conclusion
The approval of Casgevy is a genuine milestone — the moment gene editing moved from laboratory promise to approved medicine. But it also lays bare the gap between scientific capability and equitable access. The next decade of CRISPR will be defined less by whether we can edit genes and more by whether we can do so affordably, safely, and justly. On that measure, the work has barely begun.
