A tailor-made genetic patch for very rare mutations

New centre for RNA therapy set up for small patient groups.

Scientists and physicians of the Leiden University Medical Centre (LUMC) and the Radboudumc together started the Dutch Center for RNA Therapeutics (DCRT). This new virtual centre was set up with the objective to develop tailor-made RNA therapy. A therapy meant for patients with rare genetic disorders, such as Usher Syndrome.


Dutch Center for RNA Therapeutics
The DCRT opened its doors for the first time on 29 February 2020, Rare Disease Day. The DCRT is the first centre in Europe to develop RNA therapy for very rare diseases. This is about genetic diseases and mutations that are so rare, that it is less interesting for pharmaceutical companies to invest in developing a treatment. The therapies are targeted on stopping or slowing down progressive genetic eye, brain and muscle diseases by local administration of medication.

RNA therapy for Usher Syndrome
The objective of RNA therapy, also called AON therapy, is to repair the genetic defect at RNA level, so that a smaller but partly functional Usher protein can be made.
For a specific mutation an antisense oligonucleotide can be designed. Antisense-oligonucleotides, abbreviated by ASOs or AONs, can be regarded as a ‘genetic patch’ that covers the area of the mutation and makes it invisible. In this way the cause of Usher Syndrome is removed and, hopefully, the deterioration of the eyesight (and possibly hearing) with this group of patients can be stopped or mitigated.
Erwin van Wijk of the Radboud UMC in Nijmegen, the Netherlands, studies the therapeutic effect of antisense oligonucleotides (AON) for the future treatment for Usher Syndrome.
Jennifer Lentz from New Orleans (LSU School of Medicine, USA) is working on the development of an antisense oligonucleotide (AON) for patients with a specific mutation in the USH1C gene, the c.216G>A mutation.

Non-profit
Over 500 different mutations are known for the USH2A gene and RNA therapy is not possible for all these mutations. RMA therapy will be possible for about one third of the people with mutations in the USH2A gene, but some mutations are extremely rare. The new Dutch Center for RNA Therapeutics (DCRT) wants to develop tailor-made ‘genetic patches’ for this really small group of patients.

‘It is impossible for the industry to make medicines for only a few patients. Therefore it is the duty of the academic hospitals to be there especially for that group’, according to scientist Anniemiek Aartsma-Rus.

The in-house making of a ‘genetic patch’ for one specific mutation has one factor that saves a lot of time. No registration with the European Medicines Agency (EMA) is required.
Together with patients’ associations and subsidies this centre must be developed further in order to make sure that an (affordable) ‘genetic patch’ will be available for all patients with (very) rare mutations in the Usher gene in the future.

The DCRT is made possible by a financial contribution of the Human Genetics department of the LUMC. This non-profit centre will be managed by Dr. Willeke van Roon-Mom and Prof. Annemieke Aartsma-Rus of the Human Genetics department of the LUMC Also neurologists Dr. Erik Niks and Prof. Jan Verschuuren, ophthalmologists Prof. Camiel Boon and Prof. Gré Luyten and hospital pharmacist/clinical pharmacologist Prof. Henk-Jan Guchelaar are involved in this as well. Apart from Dr. Collin, geneticists Prof. Frans Cremers, Dr. Susanne Roosing and Dr. Alex Garanto as well as Dr. Erwin van Wijk as researcher of the ENT department, ophthalmologist Prof. Carel Hoyng and ENT specialist Dr. Ronald Pennings from Nijmegen are involved in the DCRT as well.

STELLAR
ProQR Therapeutics from Leiden has further developed the antisense oligonucleotides (AON), developed by Dr. Erwin van Wijk, into the medicine QR 421a and this is currently tested for effectiveness and safety in a trial called STELLAR. This is a ‘genetic patch’ for exon13, the most frequently occurring mutation in the USH2A gene. The first results will soon be published.
The ‘genetic patch’ must be regarded as a medicine and not as a gene (replacement) therapy. This is because actually no gene is replaced or repaired. The ‘patch’ must be administered repeatedly in order to have a permanent effect on the deterioration of the eyesight.