What the label lists and what reports show
Avalglucosidase alfa side effects
Avalglucosidase alfa's FDA label: “The most common adverse reactions (>5%) were headache, fatigue, diarrhea, nausea, arthralgia, dizziness, myalgia, pruritus, vomiting, dyspnea, erythema, paresthesia and urticaria.” FAERS holds 914 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 drug specific antibody present (142 reports).
- No generic listed
- Boxed warning
Check it at the source: the avalglucosidase alfa FDA label on DailyMed (effective June 5, 2025); the FDA FAERS public dashboard.
What does the label list?
From the label: adverse reactionsThe most common adverse reactions (>5%) were headache, fatigue, diarrhea, nausea, arthralgia, dizziness, myalgia, pruritus, vomiting, dyspnea, erythema, paresthesia and urticaria.
Table 4: Adverse Reactions Reported in at Least 6% of NEXVIAZYME-Treated Patients with LOPD in Study 1
| Adverse Reaction | NEXVIAZYME (N=51) n (%) | Alglucosidase Alfa (N=49) n (%) |
|---|---|---|
| Headache | 11 (22%) | 16 (33%) |
| Fatigue | 9 (18%) | 7 (14%) |
| Diarrhea | 6 (12%) | 8 (16%) |
| Nausea | 6 (12%) | 7 (14%) |
| Arthralgia | 5 (10%) | 8 (16%) |
| Dizziness | 5 (10%) | 4 (8%) |
| Myalgia | 5 (10%) | 7 (14%) |
| Pruritus | 4 (8%) | 4 (8%) |
| Vomiting | 4 (8%) | 3 (6%) |
| Dyspnea | 3 (6%) | 4 (8%) |
| Erythema | 3 (6%) | 3 (6%) |
| Paresthesia | 3 (6%) | 2 (4%) |
| Urticaria | 3 (6%) | 1 (2%) |
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 in greater detail in other sections of the labeling: Hypersensitivity Reactions Including Anaphylaxis [see Warnings and Precautions (5.1) ] Infusion-Associated Reactions (IARs) [see Warnings and Precautions (5.2) ] The most common adverse reactions (>5%) were headache, fatigue, diarrhea, nausea, arthralgia, dizziness, myalgia, pruritus, vomiting, dyspnea, erythema, paresthesia and urticaria. ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Genzyme at 1-800-633-1610, option 1 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. 6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice. Adverse Reactions from Clinical Trials in the Pompe Disease Population The pooled safety analysis from 4 clinical trials in the Pompe disease population (including Study 1) with a mean exposure of 26 months and up to 85 months of treatment included a total of 141 NEXVIAZYME-treated patients (118 adult and 23 pediatric patients [see Clinical Studies (14.1) ]. Adverse reactions were similar across both adult and pediatric populations. …
Source: FDA drug label, Genzyme Corporation, effective June 5, 2025 (SPL set 80eb3c9c-01d3-44fe-90ef-81df101b954d), via openFDA; the full label on DailyMed
What do FAERS reports show?
914 reports list avalglucosidase alfa among the medicines taken, each a report of something that happened, not proof the medicine caused it; 7 are coded as a death and 102 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 22 reactions below, 10 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?
- Avalglucosidase alfa: 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