The first patient in a Phase 1b clinical trial of Rubius Therapeutics‘ RTX-134, an experimental cell therapy for phenylketonuriara, has received a dose of the treatment, the company said.
The open-label trial (NCT04110496) is still recruiting participants at a single site in the U.S. — Children’s Hospital Colorado — and about 12 adults with phenylketonuria are expected to enroll.
“Phenylketonuria is a devastating metabolic disorder that can lead to serious cognitive impairment if not properly treated,” Rubius CEO Pablo J. Cagnoni, MD, said in a press release. “Our ultimate goal in developing RTX-134, the first of its kind, off-the-shelf Red Cell Therapeutic, is to provide patients with a well-tolerated and effective treatment option that lowers phenylalanine via infrequent administration and allows people with PKU to enjoy a normal diet.”
RTX-134 uses red blood cells collected from healthy donors that are genetically modified to produce phenylalanine ammonia lyase (PAL), an enzyme that is able to convert the amino acid phenylalanine into its natural metabolite, trans-cinnamic acid. Amino acids are the building blocks of proteins.
PAL can then prevent the buildup of toxic phenylalanine caused by the lack of activity of the enzyme phenylalanine hydroxylase (PAH) that characterizes phenylketonuria.
The study is designed to assess the safety, tolerability and pharmacokinetic properties of escalating doses of RTX-134 in patients with phenylketonuria whose phenylalanine levels are greater than 600 micromoles per liter. Pharmacokinetic properties are studied to evaluate how a medication is absorbed, distributed, metabolized, and eliminated from the body.
Each person in the study will receive a single intravenous infusion of RTX-134, and will be monitored for up to 28 days after the last detection of RTX-134 in the bloodstream. The trial will include at least four dosing groups, each with two patients, with the possibility of including additional patients or dosing groups if necessary.
“The initiation of this trial is a very exciting moment for both Rubius and the patients and caregivers we hope to serve,” Cagnoni said.
The company expects to report initial clinical data from the first patients enrolled in the trial — including preliminary safety, the therapy’s longevity in the bloodstream, and its mechanism of action — in the coming months, with an update on timing of the data to be announced as the trial progresses.