Paris (AFP)

The Telethon, in more than 30 years of existence, has contributed to the revolution of gene therapy against rare diseases affecting three million French people and helped build tools used in more widespread diseases, such as certain cancers.

For its 2019 edition, Friday and Saturday on public television channels, the great charity marathon will share the hopes and success of this "medical revolution" as called the French Association against Myopathies-Telethon.

Faced with the arrival this year of the first gene therapy for a rare neuromuscular disease, the most serious form of spinal muscular atrophy, which carries children who are most often affected before the age of ten months, the president of the AFM-Téléthon, Laurence Tiennot-Herment does not hide her emotion: "I have seen so many babies die in 30 years of association".

In the United States, where this treatment has been marketed since May 24 for children under two, the little Evelyn, treated while she was only a few weeks old, now dances with her doctor. "Such a result had never been achieved, we dreamed of images like these!" Exclaims Dr. Serge Braun, scientific director of the association.

In France, six first babies were able to benefit from the treatment, thanks to the accelerated access system called ATU (temporary authorization of use) before it was put on the market.

Like Hyacinthe, diagnosed around 7 months old. "We've seen progress quickly, and as soon as we've had an injection, she started to move her arms, to put things in her mouth," which means she can eat, and "she can move your legs a bit, "says his mother.

"The difference," says Tiennot-Herment, "is that Evelyn was treated earlier and Hyacinte at 18 months."

The disease is due to the degeneration of the motor neurons that control the muscular contraction and serve to move. It is a question of treating before an excessive loss of these neurons, even before the appearance of the symptoms. The AFM-Telethon is therefore back to the charge to claim a neonatal screening to avoid the "loss of opportunity" for babies (250 per year) that are born today while treatments exist.

- Industrialize biotherapies -

Among the researches to which Telethon money contributed, the stem cell-based "patches" grafted under the retina to treat retinitis pigmentosa, which affects nearly 30,000 people in France. The first French trial began, but eventually this treatment could also address age-related macular degeneration (AMD) affecting 1.5 million people.

Tools, "vectors" (gene repair gene carriers) designed for severe rare genetic immune deficiency (baby-bubble disease) are now being used to genetically arm white blood cells against tumors, notes Dr. Braun. Three drugs of this type are already authorized for lymphomas and leukemias.

But "the large-scale production of gene therapy drugs is coming up against an unresolved obstacle," says Dr. Braun.

"A gene therapy treatment requires a billion times more virus particles (repair gene vehicle, ed) than for a vaccine and it takes larger amounts to treat a patient with a neuromuscular disease", explains t -he.

Moreover, the cost of production can reach several hundreds of thousands of euros, he says. Thus for the Zolgensma (Novartis) from the work of Genethon and the CNRS, "half the price (about 2 million euros to treat a patient in one go) probably corresponds to the cost of production" and "whether to treat other forms of spinal muscular atrophy, the economic model would not hold ". On the other hand, the contract with the laboratory stipulates that the price must not hinder the treatment of patients in France, he says.

The challenge now is to invent new means of production to enable the industrialization of these innovative biotherapies.

Of the 8 gene therapy drugs on the market, 7 are linked directly (3) or indirectly (4) to Genethon, the Telethon laboratory.

Pledges are made at number 3637 or on telethon.fr.

© 2019 AFP