First Patient Dosed in Phase I/II Study of Experimental Gene Therapy for Cystinosis

According to a recent press release from the Massachusetts-based biotechnology company Avrobio, Inc., the first patient has been dosed in the Company’s phase I/II clinical study of their investigational cystinosis drug candidate AVR-RD-04.

The trial, which will involve up to six volunteers with cystinosis, will primarily attempt to assess the safety of the drug in addition to early evaluation of its effectiveness.

About Cystinosis

Cystinosis is a medical condition characterized by the buildup of cystine in cells throughout the body. Cystine is an amino acid — one of the building blocks used by the body to construct proteins.

In healthy individuals, cystine in cells moves around freely — including into and out of lysosomes, which are the “stomachs” of the cell that “digest” and recycle materials. This is facilitated by the transporter protein cystinosin, which is responsible for shuttling cystine molecules out of lysosomes.

The instructions for producing cystinosin are provided in a gene called CTNS. Cystinosis is caused by mutations to CTNS that result in cystinosin deficiencies. Subsequently, without transporter proteins to effectively remove it, cystine starts to build up in lysosomes. As cystine builds up, it crystallizes, potentially causing serious damage to cells — especially those in the eyes and kidneys.

There are three types of cystinosis that are differentiated by patient age at onset and areas of the body most affected. Nephropathic cystinosis or “infantile” cystinosis is the most serious, and can cause life-threatening damage to the kidneys. Intermediate-onset cystinosis tends to be less immediately severe, often causing vision loss and sensitivity to light. Eventually, they may develop kidney damage as well. Non-nephropathic, or occular cystinosis, typically occurs later in life and, as its name implies, does not affect the kidneys.

Ultimately, cystinosis patients have reduced life expectancy and often painful symptoms that can include muscle wasting, blindness, and breathing difficulties. Without treatment, nephropathic cystinosis is typically fatal by 10 and 12 years of age.

About AVR-RD-04

AVR-RD-04 is an investigational cystinosis treatment being developed by Avrobio. The treatment is a gene therapy that modifies a patient’s blood stem cells with a deactivated lentivirus to deliver an artificially-created but functional version of the CTNS gene, thereby normalizing cytinosin and cystine levels.

Gene therapies tend to be extraordinarily expensive, but have the potential to halt disease progression with a single dose. Avrobio’s impending phase I/II study will be the first step on a long clinical road with the eventual goal being AVR-RD-04’s market approval by the Food and Drug Administration. The first of a planned six patients has already received their dose of AVR-RD-04. Results collected from the study will largely determine whether or not Avrobio continues develop the drug.


Gene therapies are massive investments, but when effective, they can bring about life-changing results for patients. What do you think of this exciting new study? Share your thoughts with Patient Worthy!

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