Pharmacologic class (EPC) · 2 drug pages

Neonatal Fc receptor blocker: adverse event reports filed with FDA

3,904 reports list a drug in this class as a suspect or interacting product, 2020–2026.

Read first · FDA's statement on these data

Adverse event reports submitted to FDA do not undergo extensive validation or verification. Therefore, a causal relationship cannot be established between product and reactions listed in a report. While a suspected relationship may exist, it is not medically validated and should not be the sole source of information for clinical decision making or other assumptions about the safety or efficacy of a product. Additionally, it is important to remember that adverse event reports represent a small percentage of total usage numbers of a product. Common products may have a higher number of adverse events due to the higher total number of people using the product. openFDA, FDA

FDA adds: "There is no certainty that the reported event (adverse event or medication error) was actually due to the product. FDA does not require that a causal relationship between a product and event be proven, and reports do not always contain enough detail to properly evaluate an event." The information in these reports "cannot be used to estimate the incidence of these events."

Do not rely on openFDA to make decisions regarding medical care. While we make every effort to ensure that data is accurate, you should assume all results are unvalidated.

Not medical advice. This site counts what was reported to FDA. Questions about a medicine or device belong with a pharmacist or clinician.

3,904
reports across the class: 0% of all reports; 492
reports, 12 months to June 2026: 556 in the 12 months before; 87.3%
marked serious by the reporter: 57.4% across all reports; 2
drugs with a page: brand and generic names counted separately

Neonatal Fc receptor blocker is a pharmacologic class (an FDA Established Pharmacologic Class) with 2 drug pages on this site. Together those drugs are listed as a suspect or interacting product in 3,904 adverse event reports received by FDA, 0% of the database, from August 2020 to June 2026.

492 reports arrived in the 12 months to June 2026, down 12% from 556 in the 12 months before. FDA releases FAERS data quarterly, so the newest months are incomplete and grow in later releases. 87.3% of the class's reports are marked serious, 8.5% record death among the outcomes and 46.7% record hospitalisation, as reported.

Across the class the reactions recorded most often are myasthenia gravis (19.7%), myasthenia gravis crisis (10.9%) and fatigue (9.9%). The class median share shown beside each term is the middle value across the member drugs; it is the comparison used on every drug page in this class.

The members table is ordered by report count for navigation only. FDA states that adverse event reports "represent a small percentage of total usage numbers of a product", that "common products may have a higher number of adverse events due to the higher total number of people using the product", and that the data "by themselves are not an indicator of the safety profile of the drug or biologic."

Drugs in the class

Drug	Name type	Reports	Latest 12 months	Marked serious	Top term recorded
VyvgartEfgartigimod alfa	brand	3,354	239	93.7%	Myasthenia gravis
RystiggoRozanolixizumab	brand	550	253	48.2%	Drug ineffective

Ordered by report count for navigation only. FDA states that adverse event reports "represent a small percentage of total usage numbers of a product", that "common products may have a higher number of adverse events due to the higher total number of people using the product", and that the data "by themselves are not an indicator of the safety profile of the drug or biologic."

Reports by month, five years

FDA releases FAERS data quarterly, so the newest months are incomplete and grow in later releases.

Reactions recorded across the class

share of class reports recording the termmedian drug in the class

Myasthenia gravis19.7%770
Myasthenia gravis crisis10.9%425
Fatiguetiredness9.9%386
Dyspnoeashortness of breath7.6%296
Astheniaweakness or lack of energy6.6%256
Drug ineffectivethe medicine did not work as expected5.8%225
Headachehead pain5.6%220
Falla fall5.4%209
Hospitalisationadmission to hospital5.2%204
Urinary tract infectionbladder or urinary infection4.9%193
Deaththe patient died; cause not stated by this term4.7%184
Dysphagiadifficulty swallowing4.4%172
Covid-19COVID-19 infection4.2%163
Muscular weaknessmuscle weakness4.2%163
Nauseafeeling sick4.1%161
Diarrhoealoose or frequent stools4%156
Symptom recurrence4%155
Inappropriate schedule of product administrationthe product was taken at the wrong times3.7%144
Pneumonialung infection3.6%142
Malaisegeneral feeling of being unwell3.2%124
Diplopiadouble vision3%119
Eyelid ptosis2.8%108
Condition aggravatedthe condition being treated got worse2.7%107
Therapy interrupted2.6%102
Back painback pain2.6%100

Solid bar: share of all class reports. Hollow bar: the median share across the 2 member drugs, the reference used on each member's page. One report can record several terms.

Outcomes, patients and reporters

Outcomes recorded

Death8.5%333

Life-threatening5.4%211

Hospitalisation (initial or prolonged)46.7%1,825

Disability0.7%27

Congenital anomaly0%0

Other serious49.1%1,915

Not serious12.7%495

Patient age

Under 20%0

2 to 110%1

12 to 170.1%2

18 to 442.4%94

45 to 643.7%144

65 to 743.7%145

75 and over3.6%140

Age not given86.5%3,378

Who reported

Physician13.9%541

Pharmacist2.5%98

Other health professional14.3%559

Lawyer0%1

Consumer or non-health professional68.5%2,674

Not given0.8%31

Grey bar: all 20,646,523 reports in the database. Outcome flags are as the reporter set them and are not verified by FDA.

Questions about Neonatal Fc receptor blocker reports

Which drugs are in the Neonatal Fc receptor blocker class on this site?

Vyvgart and Rystiggo. Class membership comes from the pharmacologic class (EPC) on the drug's FDA label.

How many reports does the class have?

3,904 reports through June 2026, 492 of them in the latest 12 months. A report listing two drugs of the class counts once for each.

What reactions are recorded most often?

myasthenia gravis (19.7%), myasthenia gravis crisis (10.9%), fatigue (9.9%), dyspnoea (7.6%) and asthenia (6.6%).

Can the members table be used to rank the drugs?

No. FDA states that adverse event reports "represent a small percentage of total usage numbers of a product", that "common products may have a higher number of adverse events due to the higher total number of people using the product", and that the data "by themselves are not an indicator of the safety profile of the drug or biologic." Drugs differ in how many people take them, in the conditions they treat, in time on the market and in how diligently reports are collected.

How do I report an adverse event?

Through FDA MedWatch (Form FDA 3500, or 1-800-FDA-1088) or to the manufacturer. See the guide on how to report.

Where this comes from. Counts are built from the openFDA Drug Adverse Event (FAERS) bulk export released 28 Sep 2026, which holds reports FDA received through 30 Jun 2026. Drug names are as reported, resolved to the brand or generic name on the FDA label where openFDA's harmonisation matched them; classes are the pharmacologic class (EPC) from the label and the National Drug Code Directory of 17 Sep 2026. A class is the Established Pharmacologic Class most often attached to a drug's reports by openFDA's label harmonisation, or from the NDC Directory where reports carry none. No report narrative, lot number, patient detail or reporter identity is published. See the methodology and sources; FDA's record is authoritative, and corrections are handled within five working days.

Drug data (FAERS) through 30 Jun 2026; device data (MAUDE) through 31 Aug 2026. Not medical advice.