CRISPR, genetic engineering and humanity

What is CRISPR ?

CRISPR-Cas9 is a method for making targeted changes to genetic DNA. It was adapted from a defence system in bacteria, which use it to recognize and cut the DNA of invading viruses. The tool has two main parts: a guide RNA, a short molecule designed to match a specific DNA sequence, and Cas9, an enzyme that cuts the DNA at that location. After the cut, the cell's own repair machinery takes over which enables researchers to disable a gene or alter its sequence. 

In terms of the origin of this biotechnology, in 2012 Emmanuelle Charpentier and Jennifer Doudna demonstrated that the bacterial system could be reprogrammed to cut any DNA molecule at a chosen site. They received the 2020 Nobel Prize in Chemistry for the work . Refinements have since followed such as Base editing, for example, that changes a single DNA letter without making a complete double-strand cut.

Current use in health care

The first approved CRISPR medicine is Casgevy (exagamglogene autotemcel), from Vertex Pharmaceuticals and CRISPR Therapeutics. The US Food and Drug Administration approved it on December 8, 2023 for sickle cell disease, and on January 16, 2024 for transfusion-dependent beta thalassemia. Both approvals cover patients aged 12 and older. Both diseases stem from mutations in the HBB gene, which encodes part of adult hemoglobin.

Casgevy works outside the body, a method called ex vivo editing. A patient's blood-forming stem cells are collected, edited in a laboratory at a regulatory region of the BCL11A gene, and returned to the patient. The edit allows the body to produce fetal hemoglobin, which lacks the abnormality behind these diseases. Before infusion, patients receive the chemotherapy drug busulfan to make room for the edited cells.

 

In the phase 3 sickle cell trial, 44 patients were treated. Of the 30 with enough follow-up to be evaluated, 29 had no severe pain crises for at least 12 consecutive months, and all 30 avoided hospitalization for them. Median follow-up was 19.3 months.

CRIPR-based treatment has costs. As an example, it list price is $2.2 million, and it must be given at authorized centres experienced in stem cell transplantation. The most common side effects for patients are mouth sores, fever with low white blood cell counts, and reduced appetite.

  

Personalized therapy and future uses
In May 2025, physicians at the Children's Hospital of Philadelphia and Penn Medicine reported the first personalized CRISPR-based treatment. The patient was an infant, known as KJ, with severe CPS1 deficiency, a metabolic disease usually treated with a liver transplant. The team designed and manufactured a base-editing therapy, delivered to the liver in lipid nanoparticles, within six months.  No serious side effects had been reported at the time of this blog article. The lead physician-researcher described the hope that this approach can be scaled to fit individual patients' needs. However the result comes from just one patient, so its' general applicability is unproven.

 

Other researchers see base editing as a possible durable treatment for single-gene liver diseases that conventional gene therapy handles poorly. Three constraints are visible in the current evidence. First, most advanced examples target blood or liver. Second, follow-up is measured in months to a few years, so long-term durability and safety remain open. Third, prices on the order of millions of dollars limit access. Whether personalized editing can become routine will depend on the cost, speed, and efficacy of designing therapies one patient at a time.