Gene therapy

Every cell in the body contains a blueprint that determines which proteins the cell produces. This blueprint is called the genome or DNA, and it is organized into segments known as genes. If such a segment is faulty, an important building block in the body may be missing. This is the cause of many congenital diseases. In gene therapy, doctors introduce a functioning copy of the segment into the cells or repair the defect directly on-site. Classic medications do not do this: they merely compensate for the missing substance, often daily and for a lifetime.

From lifelong treatment to a one-time repair

For many rare hereditary diseases, there was long no treatment at all. Affected children died early or were permanently and severely impaired. Gene therapy has, for the first time, made real cures possible here. In spinal muscular atrophy, for instance, a disease that robs infants of their muscle strength, a single infusion can halt the progression of the disease.

Economically, the procedure is a special case. Because a treatment ideally works for a lifetime, manufacturers charge the equivalent value of many years of treatment all at once. Individual approved gene therapies therefore cost between one and three million euros per patient. Health insurers and manufacturers are now negotiating contracts in which part of the money is refunded if the treatment fails to work.

At the same time, the market is small. Many of the treatable diseases affect only a few thousand people worldwide. For investors, this is a risk: development costs hundreds of millions, yet the number of paying patients remains limited. Several companies have withdrawn approved gene therapies from the market again because distribution was not financially viable.

How the gene gets into the cell

The main problem is transport. A naked copy of genetic material would immediately break down in the blood and never reach a cell. That is why transport vehicles, so-called vectors, are used. Most commonly, these are disarmed viruses, from which the disease-causing genes have been removed and replaced with the desired gene. Viruses are suitable for this because they are naturally specialized in infecting cells and delivering genetic material into them.

There are two approaches. In in-vivo treatment, the vector is injected directly, for example into the eye or into the bloodstream. In the second approach, cells are taken from the patient, modified in the lab, and then given back to them. This is more elaborate but easier to control, because one can check beforehand whether the modification was successful.

A newer variant cuts directly into the genome. The gene-editing tool CRISPR locates a specific site in the DNA and cuts it there, so that the cell corrects the error while repairing it. An important distinction, which is often confused, is this: treatment is applied to the body cells of a living person. Changes to egg or sperm cells would be passed on to children and are prohibited in Germany and most other countries.

Approved therapies and companies making headlines

In Europe and the US, more than twenty gene therapies have now been approved. Among other things, they treat an inherited form of blindness, hemophilia, and sickle cell disease, a disorder of the red blood cells. In 2023, the first therapy using the CRISPR gene-editing tool was approved, which is considered a turning point.

In business news, names like Novartis, Vertex, CRISPR Therapeutics, or Bluebird Bio come up. Their share prices depend heavily on individual approval decisions by regulatory authorities. If a study turns out badly, a stock price can plunge by half in a single day.

A common misconception is that gene therapy is a cure for every disease. It works mainly where a single faulty gene is the cause. Widespread conditions such as type 2 diabetes arise from the interplay of many genes and lifestyle factors. In those cases, little can be expected from gene therapy for the foreseeable future.