Today, the U.S. Food and Drug Administration (FDA) approved Palynziq® (pegvaliase-pqpz), an enzyme therapy developed by BioMarin, for individuals with phenylketonuria (PKU) ages 12-17. Previously approved for adults in 2018, this decision expands treatment options for adolescents living with PKU.
For families navigating the transition from childhood to adolescence, this expanded approval provides another treatment option at a time when managing blood phenylalanine (phe) levels and diet often becomes more challenging.
What is Palynziq?
Palynziq is an enzyme therapy that helps the body break down phe in the blood. The medication is given as an injection. Doses are slowly increased over time—a process called titration—to help the body adjust and reduce the risk of side effects.
The American College of Medical Genetics and Genomics (ACMG) published guidelines in 2023 recommending a blood phe threshold of <360 µmol/L for optimal health. In accordance with these guidelines, Palynziq aims to lower blood phe levels and allow increased natural protein in the diet over time. While the medication can lower blood phe, it carries a risk of anaphylaxis, and individuals are prescribed epinephrine and closely monitored at the start of treatment.
What Does the Research Show?
A 2026 multi-site study by Hollander et al. evaluated Palynziq use in 53 people ages 14-22. In the study, 64% achieved treatment response. Treatment response was defined as:
- Blood phe levels below 360 µmol/L
- At least 40 grams of dietary protein tolerated per day
Key findings included:
- Mean blood phe decreased by 60%, reaching an average of 231 µmol/L
- Average time to initial response was 6 months
- Full efficacy was typically reached around 14 months
- Most common side effects included injection site reactions, joint pain, rash, headache, fatigue, fever, and gastrointestinal symptoms
- Fewer than 10% of participants experienced anaphylaxis
- Higher rates of treatment success found in those who started Palynziq during ninth-eleventh grade
One Family’s Experience with Palynziq
Although today’s approval is new for adolescents, some teens have already accessed Palynziq through clinical trials or off-label use.
Morgan, mother of two teenage daughters with PKU, shared her family’s experience starting treatment. Initially, they were apprehensive. Like many families, they had heard about the risk of anaphylaxis and felt anxious about daily injections. But her 14-year-old daughter responded well to treatment.
“Her phe levels started dropping right around the time she increased to 20 mg daily, about two months into titration. She began slowly increasing protein after three months on Palynziq. Her protein tolerance had always been 6 grams. She increased gradually to 8, 10, 15, 20, and now 25 grams. It’s been a steady increase — and truly life-changing for her.”Morgan shared that she hopes more families hear balanced stories about treatment experiences.
“I’m so happy about how this is going to make the future of my girls easier. I look ahead to college and beyond, and how this diet liberalization is going to improve their lives.”Choosing the Right Treatment for PKU
Adolescents with PKU now have three FDA-approved treatment options:
- Kuvan (sapropterin dihydrochloride)—approved in 2007
- Sephience (sepiapterin)—approved in 2025
- Palynziq (pegvaliase-pqpz)—approved in 2018 for adults 18+, now approved for ages 12–17
Each treatment works differently and comes with its own considerations. Some individuals may respond well; others may not respond at all. Side effects, administration method, lifestyle fit, and personal preferences all play a role.
Choosing the right treatment is a decision best made collaboratively between families and their metabolic care team.
Why Adolescence is a Critical Window in PKU Care
Adolescence is often one of the most challenging periods for dietary management in PKU.
Management can becomes difficult as teens:
- Spend more time independently
- Experience increased social pressure
- Begin preparing for college or work
- Gradually assume responsibility for their own medical care
The Hollander study suggests that starting Palynziq during early to mid-adolescence— while caregiver support may remain strong—can increase the likelihood of successful treatment continuation into adulthood.
Next Steps for Families Interested in Palynziq
Families interested in exploring Palynziq for their teen can:
- Speak with their metabolic care team
- Review safety considerations
- Understand insurance and prior authorization requirements
- RSVP to our flok-hosted Palynziq webinar to learn more
Like any treatment, access will depend on insurance coverage and medical eligibility. Families can also contact a BioMarin RareConnections Case Manager for guidance and support.
BioMarin’s Role in Advancing Metabolic Care
As research advances and new therapies emerge, collaboration between clinicians, researchers, industry partners, and patient communities remains central to improving quality of life across our conditions. flok’s programs are built around care, community connection, and research—and partnership with industry leaders like BioMarin play an important role in advancing that mission.
For more than two decades, BioMarin has helped drive progress for the PKU community. We are grateful for their ongoing support of the flok community through sponsorship, educational collaboration, and direct engagement with individuals and families we serve. Breakthroughs in PKU treatment—and across all our conditions—are made possible through these collective efforts, as we work to elevate the voices and priorities of people living with our rare metabolic conditions.
