The Early Results of This Gene Therapy Trial for Phenylketonuria Look Encouraging

According to a story from, the genetic medicines company Homology Medicines, Inc., has recently released promising early data from its phase 1/2 clinical trial. This clinical trial is testing the company’s experimental gene therapy HMI-102 as a treatment for phenylketonuria (PKU). This is the first ever trial to test a gene therapy as a potential treatment for this rare genetic disorder. This dose-escalation trial has seen three patients receive the therapy, including two from the low-dose cohort and one from the mid-dose cohort.

About Phenylketonuria

Phenylketonuria (PKU) is a type of metabolic disorder affecting the enzyme phenylalanine, which builds up in the body and can cause serious problems. Normally, phenylalanine is broken down, but a mutation affecting the PAH gene prevents this from happening in patients with the disorder. Prompt treatment is essential to avoid major complications. Symptoms of phenylketonuria include small head size, low birth weight, an unusual musty odor, pale skin, behavioral problems, intellectual disability, heart issues, seizures, and mental disorders. All of these symptoms can be prevented with proper and timely treatment; phenylketonuria is routinely screened for in newborns for this reason. The primary management strategy is a highly controlled diet that is low in phenylalanine. Supplements may also be considered. Most patients eventually go off the diet when they reach adulthood. Some older patients may still have trouble managing the condition later in life. To learn more about phenylketonuria, click here.

Early Findings

The focus of the excitement so far has been the results from the patient in cohort 2, the mid-dose cohort. This patient experienced a reduction in phenylalanine (Phe) of 35 percent after one week, which rose to 48 percent at four weeks. In addition this patient saw increases in tyrosine by 72 percent at week one and 85 percent at week four. Tyrosine is the amino acid that Phe turns into as it is processed by the PAH enzyme in an unaffected person. These results suggest that the therapy has restored gene and enzyme function.

While it is important to note that these are very early results with a limited number of dosed patients, the phenylketonuria community should definitely watch the progress of this trial closely, as a successful gene therapy would herald a major advancement in the treatment of this disorder.

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