Rare Daily Staff

The U.S. Food and Drug Administration approved BioMarin Pharmaceutical’s Palynziq for adult patients with phenylketonuria or PKU, a rare genetic disease that results in the inability to breakdown proteins in foods and can lead to toxic accumulations that can affect the brain.

PKU is marked by an inability to break down Phe, an amino acid that is found in all forms of protein. Left untreated, high levels of Phe become toxic to the brain and may lead to serious neurological and neuropsychiatric-related issues, impacting the way a person thinks, feels, and acts. Patients living with PKU require life-long management, including adherence to a challenging and severely restrictive daily diet of medical foods and formula that avoids the ingestion of Phe that is present in most foods.

Palynziq is the first approved enzyme substitution therapy to target the underlying cause of PKU by helping the body to break down Phe. Palynziq is BioMarin’s second approved treatment for PKU.

“The goal in treating PKU is to keep blood Phe levels within the range set in the medical guidelines, as elevation of Phe can be toxic and damaging to the brain,” said Cary Harding, professor at Oregon Health & Science University and investigator for the phase 3 studies. “Palynziq provides another much-needed tool for us to help adult patients control their Phe levels, which previously had not been achievable for many adults living with the condition.”

Palynziq significantly reduced blood Phe levels in a pivotal phase 3 study, which met the primary endpoint of change in blood Phe compared with placebo. During the double-blind, placebo-controlled, randomized withdrawal period trial, participants were randomized in a 2:1 ratio to either continue their maintenance Palynziq dosage (20 mg once daily or 40 mg once daily) or to receive matching placebo for a total of 8 weeks. Palynziq-treated patients maintained their blood Phe concentrations as compared to their randomized withdrawal baseline, whereas patients randomized to matching placebo returned to their pretreatment baseline blood Phe concentrations.

Palynziq is expected to be available in the United States by the end of June. The drug is available only through a restricted program under a Risk Evaluation and Mitigation Strategy called the
Palynziq REMS. Palynziq carries a boxed warning because of the risk of anaphylaxis, a serious and potentially life-threatening allergic reaction.

In March 2018, the European Medicines Agency accepted BioMarin’s submission of a Marketing Authorization Application for Palynziq.

May 25, 2018

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