Eluforsen (formerly QR-010) is an experimental treatment developed by ProQR Therapeutics for cystic fibrosis (CF). The inhaled treatment is designed to repair the cystic fibrosis transmembrane (CFTR) protein in patients who carry the so-called F508del mutation. F508del is the most common disease-causing mutation, affecting more than 70 percent of CF patients.

How Eluforsen works

The role of the CFTR protein is to transport charged ions across cell membranes. The transport of chloride ions, in particular, has implications in the movement of water within tissues, allowing the formation of a thin mucus that protects and lubricates the reproductive system, organs like the lungs, and other tissues.

CF patients have defective CFTR proteins that are produced when a mutationin the CFTR gene occurs. The most common of these mutations is called F508del, where an amino acid (the building blocks of proteins) is deleted at position 508 in the protein. As a result, the passage of water and charged ions through the cell membrane is compromised, resulting in the production of a thick mucus. The information necessary to make a protein is contained within the DNA. When a certain gene (or protein encoding portion of DNA) is activated, the cell makes a temporary copy of the gene that will be read and made into a protein. This temporary copy is called an RNA. A mutation in the DNA carries over to the RNA and results in the production of a faulty protein.

Eluforsen is a type of DNA molecule that is complementary to the CFTR RNA template molecule. It binds to the RNA and corrects the faulty sequence. Because the molecule is designed to bind to RNA carrying a specific mutation, this experimental therapy can treat only CF patients with that particular mutation, namely F508del.

Eluforsen in clinical trials

A Phase 1 clinical trial (NCT02564354) was initiated in 2015, with final data collection concluding in 2016. This open-label study involved 18 CF patients with the F508del mutation and was conducted in the U.S. and Europe. It assessed the increase in CFTR function through the nasal potential difference (NPD) test. This test measures skin conductance in the nasal passages as a measure of chloride transport through the CFTR protein.

In October 2016, ProQR announced that the NPD test revealed that CFTR activity is restored after Eluforsen administration.

A Phase 1b randomized, double-blind, placebo-controlled clinical trial (NCT02532764) was completed in 2017. It enrolled 70 adults from the U.S., Canada, and Europe. The aim of the study was to evaluate the safety, tolerability, and pharmacokinetics (movement in the body) of single or multiple ascending doses of Eluforsen. The results demonstrated that Eluforsen is safe and well-tolerated in all doses tested.

Other information

Eluforsen was granted fast track designation by the U.S. Food and Drug Administration (FDA) in July 2016.

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