Genome editing can be used to treat genetic diseases, fight cancer, improve crop nutrition, control disease-carrying insects, boost biofuel production, and engineer disease-resistant livestock. The first genome-editing therapy won FDA approval in late 2023, and applications are expanding rapidly across medicine, agriculture, and environmental science.
How Genome Editing Works
All genome editing tools work by cutting DNA at a precise location, then letting the cell’s own repair machinery fix the break. Scientists can use that repair process to disable a gene, correct a mutation, or insert new genetic instructions. The three major tools are zinc-finger nucleases (ZFNs), TALENs, and CRISPR-Cas9. ZFNs came first, using engineered proteins that recognize specific DNA sequences and pair them with a cutting enzyme. TALENs followed around 2009, offering more flexible targeting because each protein module recognizes a single DNA letter rather than a three-letter chunk.
CRISPR-Cas9, the tool that made genome editing a household term, works differently. Instead of engineering a new protein for every target, it uses a short strand of RNA as a guide to lead the Cas9 cutting enzyme to the right spot. This makes it far cheaper and faster to design new edits, which is why CRISPR dominates current research and clinical development.
Treating Genetic Blood Disorders
The most visible medical use so far is Casgevy, the first CRISPR-based therapy approved by the FDA. Approved in late 2023 for sickle cell disease, it works by editing a patient’s own blood stem cells outside the body. The edit disables a gene called BCL11A that normally suppresses production of fetal hemoglobin, a form of the oxygen-carrying protein that doesn’t cause the sickling problem. Once the edited cells are infused back into the patient and engraft in the bone marrow, they begin producing fetal hemoglobin, which compensates for the defective adult version.
In clinical trials, 29 out of 31 evaluable patients (93.5%) went at least 12 consecutive months without the severe pain crises that define sickle cell disease. That’s a transformative result for a condition that previously required lifelong management or a bone marrow transplant from a matched donor.
Other Genetic Diseases in Clinical Trials
Beyond sickle cell disease, genome editing therapies are in clinical trials for several other inherited conditions. One targets familial hypercholesterolemia, a common genetic disorder that causes dangerously high cholesterol from birth. Early results from the VERVE-101 trial show promising reductions in cholesterol levels using a technique called base editing, which changes a single DNA letter without cutting both strands. Another trial is testing a base editing therapy for alpha-1 antitrypsin deficiency, a genetic condition that damages the liver and lungs. Both of these therapies are delivered via tiny fat particles (lipid nanoparticles) that carry the editing machinery directly to liver cells, avoiding the need to remove and re-infuse a patient’s cells.
Engineering Immune Cells to Fight Cancer
CAR-T therapy, where a patient’s immune cells are reprogrammed to hunt cancer, has already proven effective against certain blood cancers. Genome editing is now being used to make these engineered immune cells more powerful and more widely available.
One major application is creating “off the shelf” CAR-T cells from donor immune cells. Normally, using another person’s immune cells would trigger a dangerous reaction called graft-versus-host disease. By using CRISPR to disable the gene (called TRAC) that encodes the T-cell receptor responsible for recognizing foreign tissue, researchers can prevent this reaction. Disrupting one copy of this gene eliminates the problematic receptor in roughly 50 to 60% of the edited cells.
The other frontier is preventing T-cell exhaustion, a process where immune cells lose their ability to keep fighting tumors. Cancer cells exploit molecular “brakes” on T cells to shut them down. Editing out the genes for these brakes, particularly the one encoding PD-1, is the most widely studied strategy for keeping CAR-T cells active longer. Researchers are also knocking out genes for other exhaustion signals like TIM-3, LAG-3, and CTLA-4. In preclinical cancer models, disabling CTLA-4 alone improved CAR-T cell proliferation and tumor-killing ability.
Improving Crop Nutrition
Two genome-edited food products are already on the market. Calyxt’s Calyno soybean oil, launched in the United States, was developed using TALENs to knock out genes that convert oleic acid into less desirable fats. The result is a soybean with over 80% oleic acid, comparable to olive oil, and less than 3% linolenic acid, which causes off-flavors and shorter shelf life. In Japan, Sanatech Seed released the Sicilian Rouge High GABA tomato in 2021, containing four to five times the normal amount of GABA, an amino acid linked to blood pressure regulation.
The pipeline is much broader. CRISPR has been used in research settings to boost lycopene content in tomatoes by more than fivefold, increase resistant starch in rice (which lowers glycemic impact), raise vitamin C levels in wild tomato varieties, and increase beta-carotene in bananas. Peanuts have been edited to roughly double their oleic acid content, and rapeseed has been modified for higher oil yields with a healthier fatty acid profile. Sorghum has been edited to improve protein digestibility, which matters enormously in regions where it’s a dietary staple.
Controlling Disease-Carrying Mosquitoes
Gene drives represent one of the most ambitious and controversial uses of genome editing. A gene drive is a genetic element designed to spread through a wild population faster than normal inheritance would allow. For malaria control, researchers have built CRISPR-based gene drives targeting the doublesex gene in Anopheles gambiae mosquitoes, which renders females infertile. In caged laboratory populations, this approach achieved complete population suppression.
Field-like conditions tell a more complicated story. When gene drives were placed at three genetic loci affecting female fertility, biased inheritance approached 100%, and gene drive frequency peaked at 72 to 77% by the sixth generation. But by the 25th generation, the population had only declined by less than 20%, likely because resistance mutations evolved. This gap between laboratory cages and longer-term outcomes remains one of the biggest challenges before gene drives could be deployed in the wild.
Engineering Disease-Resistant Livestock
Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) costs the global pig industry billions of dollars annually. The virus enters pig cells through a receptor protein called CD163. Researchers used genome editing to introduce a single-letter change (E529G) in the CD163 gene of pigs, which prevents the virus from binding to and entering cells. In viral challenge tests, pigs carrying this edit had viral loads two orders of magnitude lower than unedited pigs, essentially conferring resistance to highly pathogenic strains of the virus. Unlike traditional breeding, which would take many generations to achieve a similar result, genome editing introduced this protective change in a single step.
Boosting Biofuel Production
Genome editing is accelerating progress in making biofuels from microorganisms. A CRISPR-engineered strain of the green alga Chlamydomonas reinhardtii increased its lipid yield (the raw material for biodiesel) by up to 64.25%. In another experiment with the same species, total lipid accumulation reached 28% of dried biomass, with oleic acid production rising by 27.2%. On the ethanol side, CRISPR-modified strains of brewer’s yeast (Saccharomyces cerevisiae) have achieved yields up to 74.7% higher than unmodified strains. These improvements come from knocking out genes that divert metabolic energy away from fuel-relevant compounds and ramping up genes involved in lipid or alcohol synthesis.
Safety Challenges: Off-Target Edits
The core safety concern with any genome editing tool is off-target effects, where the editing machinery cuts DNA at unintended locations. Even small, unplanned mutations could theoretically activate cancer-promoting genes or disrupt essential functions. Current best practices call for using at least two methods to check for off-target cuts: a computational prediction tool (Elevation is the most recommended) to identify the top 100 or so candidate sites, and an experimental detection method called GUIDE-seq to catch sites the software might miss.
The gold standard for measuring off-target editing is amplicon-based next-generation sequencing, which can detect unintended mutations down to a frequency of about 0.1%, meaning one edited cell in a thousand. Sites where the unintended editing rate exceeds 0.5% are generally flagged as concerning and tend to rank among the top predicted off-target locations. These detection limits are important context: they’re sensitive enough to catch most clinically relevant problems, but rare events below 0.1% could still go undetected.
Regulatory Lines: Somatic vs. Heritable Editing
The World Health Organization draws a sharp distinction between somatic editing (changes to non-reproductive cells that affect only the treated individual) and heritable germline editing (changes to eggs, sperm, or embryos that would be passed to future generations). Somatic editing, like Casgevy, is considered acceptable in countries with appropriate regulations and is already in clinical use. Heritable editing is a different matter entirely. In July 2019, the WHO Director-General stated that “it would be irresponsible at this time for anyone to proceed with clinical applications of human germline genome editing.”
A WHO Expert Advisory Committee published a governance framework in 2021 addressing the scientific, ethical, social, and legal dimensions of human genome editing. The concern isn’t just safety. Heritable edits would affect people who never consented to them, and errors could propagate through generations. For now, the international consensus holds that heritable human genome editing should not move to clinical application, while somatic therapies continue advancing through standard regulatory channels.