Rubius Therapeutics is currently recruiting patients for its Phase 1b clinical trial that will evaluate the safety and early efficacy of RTX-134, its investigational cell therapy for phenylketonuria.
RTX-134 uses red blood cells collected from a healthy donor that are genetically engineered to produce the enzyme phenylalanine ammonia lyase (PAL). This enzyme can bypass the neurotoxic effects of the reduced levels of functional phenylalanine hydroxylase (PAH) that characterize phenylketonuria.
This investigational cell therapy is believed to prevent the buildup of phenylalanine induced by PAH deficiency by converting the amino acid into two of its natural metabolites: trans-cinnamic acid and ammonia.
The open-label Phase 1b trial (NCT04110496) is expected to enroll approximately 12 patients, 18 years or older, with genetically confirmed phenylketonuria at the Children’s Hospital Colorado.
Participant will receive a single dose of RTX-134 administrated directly into the vein (intravenously).
Researchers will primarily assess the safety and tolerability of increasing dosages of the cell therapy, as well as its stability when inside the body. They will also evaluate the blood levels of trans-cinnamic acid as a measure of RTX-134’s efficacy and proof-of-mechanism.
These data will allow researchers to select the optimal dose of treatment that could be safely used to achieve the best clinical outcome possible in further studies.
“Over the last quarter, our team has successfully manufactured RTX-134 for our Phase 1b trial for the treatment of patients with phenylketonuria,” Pablo J. Cagnoni, MD, CEO of Rubius Therapeutics, said in a press release. “Our clinical sites are actively recruiting patients, and we plan to announce when we have treated the first patient. In order for us to share follow up data from the first patients treated in the study, we expect to report initial clinical results during the first quarter of 2020.”
Find more information about the trial and how to participate here or here.
Preclinical studies confirmed the therapy’s mechanism of action, showing that red blood cells from mice engineered to carry the PAL enzyme could effectively transform phenylalanine into trans-cinnamic acid and ammonia. The engineered cells were stably in circulation in the body of the mice by approximately 50 days after administration, which is the equivalent to the normal circulating time of mouse red blood cells.
Based on these results, the researchers believe that RTX-134 may have an approximate circulating time of up to 120 days in patients, which is the normal circulating time of human red blood cells.
RTX-134 represents an off-the-self approach that may provide a more efficacious and convenient treatment option for patients with phenylketonuria, according to the company.
Earlier this year, Rubius announced the U.S. Food and Drug Administration’s clearance of its investigational new drug application for RTX-134.