The promise of gene therapy

For diseases caused by a single faulty gene, a once-radical idea is becoming real: repair the instructions themselves.

Most medicines manage a disease. Gene therapy aims at something more fundamental, to correct the genetic error at its source.

The core idea

Gene therapy works by delivering new genetic material into a patient's cells, to compensate for or replace a faulty gene, or to switch a harmful one off.¹ For conditions caused by a single defective gene, it offers the possibility not of managing symptoms, but of addressing the cause.

The delivery problem

The central challenge has always been delivery: how to get genetic material into exactly the right cells. The leading solution borrows from biology itself, engineered viruses, especially adeno-associated viruses (AAVs), which are naturally efficient at entering cells. AAV-based systems have been used in over 400 clinical trials targeting more than 65 diseases.¹

Not to manage the error, but to correct it.

The editing era

A newer tool has accelerated the whole field: CRISPR-Cas, which allows genes to be edited with remarkable precision.² In 2023, Casgevy became the first approved CRISPR-based therapy, treating sickle cell disease and beta-thalassemia by editing a gene to reactivate the body's fetal haemoglobin.² It joined a growing list of approved gene therapies for once-untreatable conditions.

Why it matters

Gene therapy remains complex, costly, and early. But for rare genetic diseases, where a single gene so often holds the answer, it represents one of the most hopeful shifts medicine has seen in a generation.