What the label lists and what reports show
Pegvaliase side effects
Pegvaliase's FDA label: “Most common adverse reactions (at least 20% in either treatment phase) are: injection site reactions, arthralgia, hypersensitivity reactions, headache, generalized skin reactions lasting at least 14 days, nausea, abdominal pain, vomiting, cough, oropharyngeal …” FAERS holds 8,167 reports naming it through July 30, 2026; the reaction reported most often, leaving out the conditions it is used for, product-use terms and outcomes, is arthralgia (1,395 reports).
- No generic listed
- Boxed warning
Check it at the source: the pegvaliase FDA label on DailyMed (effective March 2, 2026); the FDA FAERS public dashboard.
What does the patient leaflet say about side effects?
From the patient leaflet: What are the possible side effects of PALYNZIQ?PALYNZIQ may cause serious side effects, including: Severe allergic reactions (anaphylaxis). See " What is the most important information I should know about PALYNZIQ? " Other allergic reactions to PALYNZIQ can happen during treatment. Call your healthcare provider right away if you get any of the following symptoms of an allergic reaction including: rash, itching, or swelling of the face, lips, eyes, or tongue. Your healthcare provider may change your dose or temporarily stop treatment with PALYNZIQ, or give you medicine for you to take before your PALYNZIQ injection to help reduce the symptoms of an allergic reaction. Injection site infections. Serious infections at the injection site have happened in people during treatment with PALYNZIQ. […]
Source: FDA drug label, BioMarin Pharmaceutical Inc., effective March 2, 2026 (SPL set 6dba844a-db02-44f8-8593-ce497ed9406c), via openFDA; the full label on DailyMed
What does the label list?
From the label: adverse reactionsMost common adverse reactions (at least 20% in either treatment phase) are: injection site reactions, arthralgia, hypersensitivity reactions, headache, generalized skin reactions lasting at least 14 days, nausea, abdominal pain, vomiting, cough, oropharyngeal pain, pruritus, diarrhea, nasal congestion, fatigue, dizziness, and anxiety.
Table 2: Adverse Reactions ≥ 15% incidence in either treatment phase Reported in at Least 15% of PKU Patients Treated with PALYNZIQ in an Induction/Titration/Maintenance Regimen in Studies 1, 2, and 3 – Incidence and…
| Adverse Reaction | N (%) N (%) = Number of patients with at least 1 Adverse Reaction (%); Rate =… | Episodes (Rate) | N (%) | Episodes (Rate) |
|---|---|---|---|---|
| Injection site reactions Includes injection site: reaction, erythema, pruritus, pain,… | 252 (88%) | 2965 (21) | 166 (74%) | 2169 (3.3) |
| Arthralgia Includes arthralgia, pain in extremity, back pain, musculoskeletal pain, neck… | 211 (74%) | 1049 (7.4) | 154 (68%) | 893 (1.4) |
| Hypersensitivity reactions Includes rash, urticaria, anaphylaxis, rash generalized,… | 153 (54%) | 634 (4.5) | 145 (64%) | 845 (1.3) |
| Headache Includes headache, migraine, sinus headache | 102 (36%) | 214 (1.5) | 126 (56%) | 1049 (1.6) |
| Generalized skin reaction lasting at least 14 days Includes pruritus, rash, urticaria,… | 61 (21%) | 97 (0.7) | 93 (41%) | 186 (0.3) |
| Nausea | 52 (18%) | 68 (0.5) | 69 (31%) | 141 (0.2) |
| Abdominal pain Includes abdominal pain, abdominal pain upper, abdominal discomfort | 39 (14%) | 54 (0.4) | 67 (30%) | 162 (0.3) |
| Vomiting | 36 (13%) | 53 (0.4) | 68 (30%) | 139 (0.2) |
| Cough | 27 (9%) | 33 (0.2) | 67 (30%) | 100 (0.2) |
| Oropharyngeal pain | 38 (13%) | 45 (0.3) | 65 (29%) | 108 (0.2) |
| Pruritus | 58 (20%) | 102 (0.7) | 61 (27%) | 424 (0.7) |
| Diarrhea | 26 (9%) | 32 (0.2) | 61 (27%) | 116 (0.2) |
| Nasal congestion | 12 (4%) | 16 (0.1) | 61 (27%) | 87 (0.1) |
| Fatigue | 37 (13%) | 81 (0.6) | 55 (24%) | 110 (0.2) |
| Dizziness | 47 (16%) | 65 (0.5) | 48 (21%) | 100 (0.2) |
| Anxiety | 14 (5%) | 23 (0.2) | 48 (21%) | 100 (0.2) |
| Alopecia | 13 (5%) | 14 (0.1) | 43 (19%) | 62 (0.1) |
Rows and numbers as the label prints them, under its own column headings (the first rows of a longer table where it runs on). A reaction in a trial table is not necessarily caused by the medicine, and trials differ from everyday use.
From the label: adverse reactions, continuedThe following serious adverse reactions are discussed below and in other sections of labeling: Anaphylaxis [see Warnings and Precautions (5.1) ] Other Hypersensitivity Reactions [see Warnings and Precautions (5.3) ] Injection Site Infections [see Warnings and Precautions (5.4) ] Hypophenylalaninemia [see Warnings and Precautions (5.5) ] Most common adverse reactions (at least 20% in either treatment phase) are: injection site reactions, arthralgia, hypersensitivity reactions, headache, generalized skin reactions lasting at least 14 days, nausea, abdominal pain, vomiting, cough, oropharyngeal pain, pruritus, diarrhea, nasal congestion, fatigue, dizziness, and anxiety. ( 6.1 ) Most common adverse reactions in patients who are 12 to less than 18 years of age (at least 20% and greater than in control) are: injection site reactions, arthralgia, headache, pyrexia, hypersensitivity reactions, dizziness, nausea, vomiting, fatigue, and pain in extremity. ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact BioMarin Pharmaceutical Inc. at 1-866-906-6100, or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. …
Source: FDA drug label, BioMarin Pharmaceutical Inc., effective March 2, 2026 (SPL set 6dba844a-db02-44f8-8593-ce497ed9406c), via openFDA; the full label on DailyMed
What do FAERS reports show?
8,167 reports list pegvaliase among the medicines taken, each a report of something that happened, not proof the medicine caused it; 12 are coded as a death and 301 as a hospital stay. Counts follow how widely a medicine is used and watched, and they are not a measure of how risky it is. Of the 23 reactions below, 15 are named by the same term (in US spelling) in the label's adverse reactions, warnings or patient leaflet; a reaction the label does not name may still be there under another word, and a report does not show that the medicine caused it.
Reports received each year
The 25 most reported reactions
Source: FDA Adverse Event Reporting System (FAERS) via openFDA, reports through July 30, 2026; reactions as MedDRA preferred terms
What next?
- Pegvaliase: the full record
- label, generics, price, shortages, recalls
- Report a side effect to the FDA
- MedWatch
- Side effects hub
- the most reported medicines and reactions