FDA Gives Palynziq the Green Light for Treatment of Adults with Phenylketonuria

Biomarin Pharmaceutical’s Palynziq, or pegvaliase-pqpz, has just received approval from the US Food and Drug Administration (FDA) to reduce blood phenylalanine (Phe) concentrations in adults with phenylketonuria (PKU), who, despite existing management, have uncontrolled blood Phe concentrations higher than 600 micromo/L.

Estimated to impact about 1 in 12,500 children annually in the United States, PKU is a rare inherited metabolic disorder that affects the way the body processes food into energy. Left untreated, PKU results in increased levels of Phe in the blood; left untreated, Phe can potentially build up to reach harmful levels within the body, neurological and neuropsychiatric-related complications that can impact the way a patient thinks, acts, and feels.

"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,” Cary Harding, MD, a professor at Oregon Health & Science University and the investigator for the Phase 3 studies, said in a statement. “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."

The FDA’s decision was made based on data from a phase 3 clinical trial, PRISM-2, in which pegvaliase reduced blood Phe levels, meeting the primary endpoint of change in blood Phe compared with placebo (P <.0001). In total, 57% of patients were taking medical food at baseline and 16% were on a protein-restricted diet at baseline (defined as receiving greater than 75% of total protein intake from medical food).

During the course of the randomized withdrawal period trial, patients were randomized in a 2:1 ratio to either continued maintenance dosage (20 mg or 40 mg once daily) or to receive matching placebo, for a duration of 8 weeks. Those treated with pegvaliase maintained blood Phe concentrations as compared to randomized withdrawal baseline measurements, while those on placebo returned to their pretreatment concentration levels.

The approval comes during National PKU Awareness Month, were patient organizations worldwide are working to spread awareness of the rare disease and raise funds to go towards more academic research. There is no cure for PKU, but the approval of Palynziq offers an effective new treatment option to adults living with the disorder.

"BioMarin is thrilled to be able to offer this important new therapy to adults with PKU who are unable to control their Phe levels with existing options. The approval of Palynziq is the culmination of more than a decade of perseverance by BioMarin employees dedicated to bringing treatments to PKU adult patients," said Jean-Jacques Bienaimé, the chairman and chief executive officer of BioMarin, said in a statement. "We are proud of this medical achievement and appreciate the FDA's thoughtful review of our application. We also are grateful to the PKU patients and medical communities for their continued partnership and participation in the clinical program that led to the approval of this effective therapy."

According to BioMarin, the therapy is expected to be available in June 2018, with marketing beginning immediately.