Palynziq (pegvaliase-pqpz)
An approved treatment for Phenylketonuria.
Drug facts
The same compound appears under different names depending on the context. Here is how to identify Pegvaliase-pqpz wherever you encounter it, plus the key facts at a glance.
- Generic name
- Pegvaliase-pqpz
- Brand name
- Palynziq
- Development code
- BMN 165
- Drug class
- Phenylalanine-metabolizing enzyme (PEGylated)
- Manufacturer
- BioMarin Pharmaceutical
- How it's taken
- Injected under the skin from prefilled syringes, by the patient or a caregiver after training.
A daily self-injected enzyme that lowers blood Phe in PKU when diet and other treatment have not kept it below 600 micromol/L. It is approved for people 12 and older, and because it can cause a severe allergic reaction, it comes only through a safety program that requires carrying epinephrine.
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Where Pegvaliase-pqpz fits
The only PKU drug that breaks down Phe directly, so it can work whatever a person's PAH gene changes are. Kuvan (sapropterin) and Sephience (sepiapterin) work only in people whose own PAH enzyme responds to them.
How Pegvaliase-pqpz works
In PKU, the PAH enzyme in the liver does not work, so phenylalanine (Phe) from protein builds up in the blood and harms the brain. Pegvaliase is a different enzyme, borrowed from bacteria, that breaks Phe down without needing PAH. It is coated in PEG, a chemical shield that helps it stay in the body longer. Because it works regardless of a person's PAH gene changes, it can help people whose PKU does not respond to Kuvan.
Side effects and safety
- Other allergic reactions. Allergic reactions other than anaphylaxis, such as rash, hives and itching, affected 72% of people 16 and older and 33% of younger teens in the trials.
- Injection site infections. Abscess, cellulitis and skin breakdown at the shot site have been reported, and some needed a hospital stay or surgery.
- Phe too low. Blood Phe can fall below 30 micromol/L, so Phe is checked and diet protein or the dose is adjusted.
- Blood Phe every 4 weeks until a steady dose is reached, and more often in teens
- Watch for allergic reactions for at least 60 minutes after the first dose
- An adult observer may be needed during injections
Palynziq has a boxed warning for anaphylaxis, a severe allergic reaction that can happen at any time during treatment. In the adult trials, 10% of people had at least 1 episode, and 11% of teens did in the teen trial. Most happened within an hour of a dose, though some came up to 48 hours later. Epinephrine must be prescribed and carried at all times.
Other allergic reactions were very common, and so were injection site reactions and joint pain. The label also warns about injection site infections and Phe dropping too low.
This is not a complete list of side effects. Talk to your doctor or pharmacist about what to expect and when to seek medical attention.
Taking Pegvaliase-pqpz
Injected under the skin from prefilled syringes, by the patient or a caregiver after training. Treatment starts slowly at 2.5mg once a week for 4 weeks, then steps up over at least 5 weeks to 20mg once a day. People stay on 20mg a day for at least 24 weeks before any increase to 40mg, and then to a maximum of 60mg. Treatment stops if Phe has not come down enough after 16 weeks at 60mg. The doctor may suggest an antihistamine or fever reducer before each dose.
Availability and cost
Only available as the brand-name product.
Help paying for Palynziq
Pick your insurance to see which help fits. Drugmaker copay cards can't be used with Medicare, Medicaid or TRICARE; charity funds are the usual route there.
- Insurance and case manager help
A Case Manager helps with insurance coverage and the specialty pharmacy, and a Clinical Coordinator provides injection training.
The official page does not say who qualifies. Ask the program. · source - Copay help
Eligible commercially insured patients may pay as little as $0; BioMarin says over 97% did. Not valid with Medicare, Medicare Advantage, Medigap, Medicaid, VA, DoD, TRICARE or other government programs, or for cash-paying patients. US and Puerto Rico only, and eligibility is reconfirmed every year.
For: private insurance · source
Good to know: Call 1-866-906-6100, weekdays 8am-8pm ET. Palynziq is available only through the Palynziq REMS (1-855-758-7367). The official page does not describe a free medicine program; ask the Case Manager.
- From a charity · NORD RareCarePhenylketonuria (PKU) Medical Assistance fundOpen
Pays for: Medical and medication costs.
The foundation says: “Accepting Applications” - From a charity · NORD RareCarePhenylketonuria (PKU) Premium Copay Assistance fundOpen
Pays for: Insurance premiums and copays.
The foundation says: “Accepting Applications” - From a charity · NORD RareCarePhenylketonuria (PKU) Emergency Relief fundOpen
Pays for: Emergency relief.
The foundation says: “Accepting Applications”
Access and eligibility
Approved for people 12 and older with PKU whose blood Phe stays above 600 micromol/L on their current management. Patients, prescribers and pharmacies must all enroll in the Palynziq REMS, and patients must carry epinephrine.
Source: BioMarin RareConnections (Palynziq support)
Access program details are provided for informational purposes and may vary based on insurance coverage, geographic location, and individual circumstances. Confirm current eligibility directly with the manufacturer or your specialty pharmacy.
Clinical trial results
The adult approval rested on PRISM, 2 trials in people with PKU whose Phe was above 600 micromol/L. In PRISM-301 (NCT01819727), 261 adults started Palynziq, and 75% reached their target dose. In PRISM-2 (NCT01889862), 86 people whose Phe had dropped at least 20% were randomly switched to stay on Palynziq or to placebo for 8 weeks.
Phe rose sharply on placebo, leaving a gap of 973 micromol/L at the 20mg dose and 589 at 40mg. Each gap had less than a 1 in 10,000 chance of being a fluke. For teens, the PEGASUS trial (NCT05270837) compared Palynziq with diet alone in 55 people aged 12-17. Phe fell 473 micromol/L on Palynziq against 19 on diet alone over 72 weeks.
Development history
BioMarin developed pegvaliase, and the FDA approved it on May 24, 2018 for adults with uncontrolled PKU. An October 6, 2020 update set the maximum at 60mg a day. On February 27, 2026 the FDA extended approval to teens aged 12-17. The same change updated the REMS so that any form of epinephrine can be prescribed, not only an auto-injector.
Explore Phenylketonuria trials
Other Phenylketonuria treatments
PKU has 3 kinds of FDA-approved drug treatment alongside a low-protein diet and medical formula. Kuvan (sapropterin), approved in 2007, and its generics help people whose PAH enzyme responds to it, from 1 month of age. Sephience (sepiapterin) was approved July 28, 2025 from 1 month of age for people who respond. Palynziq (pegvaliase), approved May 24, 2018, is a daily injection for people 12 and older whose Phe stays above 600 micromol/L.
Common questions about Pegvaliase-pqpz
▸What is Pegvaliase-pqpz (Palynziq)?
A daily self-injected enzyme that lowers blood Phe in PKU when diet and other treatment have not kept it below 600 micromol/L. It is approved for people 12 and older, and because it can cause a severe allergic reaction, it comes only through a safety program that requires carrying epinephrine.
▸How does Pegvaliase-pqpz work?
In PKU, the PAH enzyme in the liver does not work, so phenylalanine (Phe) from protein builds up in the blood and harms the brain. Pegvaliase is a different enzyme, borrowed from bacteria, that breaks Phe down without needing PAH. It is coated in PEG, a chemical shield that helps it stay in the body longer. Because it works regardless of a person's PAH gene changes, it can help people whose PKU does not respond to Kuvan.
▸What are the side effects of Pegvaliase-pqpz?
Palynziq has a boxed warning for anaphylaxis, a severe allergic reaction that can happen at any time during treatment. In the adult trials, 10% of people had at least 1 episode, and 11% of teens did in the teen trial. Most happened within an hour of a dose, though some came up to 48 hours later. Epinephrine must be prescribed and carried at all times. Other allergic reactions were very common, and so were injection site reactions and joint pain. The label also warns about injection site infections and Phe dropping too low.
▸How is Pegvaliase-pqpz taken?
Injected under the skin from prefilled syringes, by the patient or a caregiver after training. Treatment starts slowly at 2.5mg once a week for 4 weeks, then steps up over at least 5 weeks to 20mg once a day. People stay on 20mg a day for at least 24 weeks before any increase to 40mg, and then to a maximum of 60mg. Treatment stops if Phe has not come down enough after 16 weeks at 60mg. The doctor may suggest an antihistamine or fever reducer before each dose.
▸Is Pegvaliase-pqpz FDA approved?
Yes, Pegvaliase-pqpz (Palynziq) is FDA approved (2018) for the treatment of Phenylketonuria.
▸Why do I need to carry epinephrine with Palynziq?
Palynziq can cause anaphylaxis at any point in treatment, even after months of doses without trouble. In the trials, 10% of adults and 11% of teens had at least 1 episode. Epinephrine must be prescribed and kept on hand so a reaction can be treated right away.
▸Can teenagers take Palynziq?
Yes, since February 27, 2026 it is approved for ages 12-17 as well as adults. In the PEGASUS trial, teens on Palynziq lowered Phe by 473 micromol/L on average over 72 weeks, against 19 on diet alone.
▸How long does Palynziq take to work?
It can take many months, because the dose is raised slowly over at least 9 weeks, then held at 20mg a day for at least 24 weeks before any increase. Some people need 40mg or 60mg a day to bring Phe down.
▸What is the difference between Palynziq and Kuvan?
Kuvan helps a person's own PAH enzyme work better, so it only works for people who respond to it. Palynziq breaks Phe down directly, so it can work regardless of PAH gene changes, but it is an injection with a serious allergy risk.
Sources and references
Every factual claim on this page is drawn from the public sources listed below. Click any reference to open the original document.
- U.S. National Library of Medicine, DailyMed · 2026-03-02. PALYNZIQ (pegvaliase-pqpz) injection: prescribing information. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=6dba844a-db02-44f8-8593-ce497ed9406c
- U.S. Food and Drug Administration · 2018-05-24. FDA approves a new treatment for PKU, a rare and serious genetic disease. https://www.fda.gov/news-events/press-announcements/fda-approves-new-treatment-pku-rare-and-serious-genetic-disease
- U.S. Food and Drug Administration · 2026-02-27. BLA 761079 supplement approval letter (ages 12-17 and REMS update). https://www.accessdata.fda.gov/drugsatfda_docs/appletter/2026/761079Orig1s031correctedltr.pdf
- ClinicalTrials.gov. Phase 3 Study to Evaluate the Efficacy & Safety of Self-Administered Injections of BMN165 by Adults With PKU (PRISM-2). https://clinicaltrials.gov/study/NCT01889862
- ClinicalTrials.gov. Study to Evaluate the Safety and Efficacy of Pegvaliase in Adolescents (Ages 12-17) With Phenylketonuria (PEGASUS). https://clinicaltrials.gov/study/NCT05270837
- BioMarin. PALYNZIQ patient support. https://www.biomarin-rareconnections.com/patient/palynziq/