Homology Medicines' Gene Therapy For Phenylketonuria Found Safe, Efficacy Data Mixed

Shares of genetic therapy company Homology Medicines Inc FIXX were moving to the downside Wednesday.

Homology Medicines Reports Trial Data

Bedford, Massachusetts-based Homology announced initial Phase 1/2 data from the pheNIX trial that evaluated its HMI-102 gene therapy in patients with phenylketonuria, with safety data showing that HMI-102 was well-tolerated.

Cohort 1 consisted of two patients administered a low dose and Cohort 2 consisted of one patient administered a medium dose. 

The efficacy data was mixed, with the Cohort 1 patients not showing a reduction in phenylalanine through weeks 10 and 12.

But the patient dosed in Cohort 2 showed a reduction in phenylalanine of 35% and 48% from the baseline at weeks one and four, respectively.

Additionally, the first patient dosed in Cohort 2 also showed increases in tyrosine levels of 72% and 85% at weeks one and four, respectively, which suggests increased PAH enzyme activity.

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About Phenylketonuria 

Phenylketonuria is a rare inherited error of metabolism caused by a mutation in the PAH gene. No approved treatment options exist and the current standard of a care is a highly restrictive diet that is not always effective.

If left untreated, the disorder results in progressive and serious neurological impairment.

Phenylketonuria affects about 16,500 people in the U.S. and 50,000 people globally, according to Homology Medicines. An estimated 350 newborns are diagnosed with the disorder in the U.S. every year.

"Over a year-and-a-half ago as a preclinical company, we made a commitment to report initial clinical data from the pheNIX trial by the end of 2019. Today, we provide more data than we promised, which I believe is a testament to our team's ability to execute as well as the strong interest from patients and physicians," CEO Arthur Tzianabos said in a statement. 

Homology shares were down 3.84% at $20.92 at the time of publication Wednesday.