Pharmacologic class (EPC) · 6 drug pages

HER2/neu receptor antagonist: adverse event reports filed with FDA

85,553 reports list a drug in this class as a suspect or interacting product, 2004–2026.

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.

85,553
reports across the class: 0.4% of all reports; 5,681
reports, 12 months to June 2026: 9,362 in the 12 months before; 86.6%
marked serious by the reporter: 57.4% across all reports; 6
drugs with a page: brand and generic names counted separately

HER2/neu receptor antagonist is a pharmacologic class (an FDA Established Pharmacologic Class) with 6 drug pages on this site. Together those drugs are listed as a suspect or interacting product in 85,553 adverse event reports received by FDA, 0.4% of the database, from January 2004 to June 2026.

5,681 reports arrived in the 12 months to June 2026, down 39% from 9,362 in the 12 months before. FDA releases FAERS data quarterly, so the newest months are incomplete and grow in later releases. 86.6% of the class's reports are marked serious, 12% record death among the outcomes and 32% record hospitalisation, as reported.

Across the class the reactions recorded most often are diarrhoea (11.5%), off label use (7.3%) and nausea (7.3%). 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
HerceptinTrastuzumab	brand	30,399	934	81.2%	Diarrhoea
Trastuzumab	generic	28,929	2,893	95.7%	Diarrhoea
PerjetaPertuzumab	brand	12,939	643	77.7%	Diarrhoea
Pertuzumab	generic	11,353	1,125	95.6%	Diarrhoea
KanjintiTrastuzumab-anns	brand	1,432	74	22.4%	Product storage error
Ontruzant	generic	501	12	93.4%	Diarrhoea

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

Diarrhoealoose or frequent stools11.5%9,860
Off label useused for a purpose or in a way not on the label7.3%6,287
Nauseafeeling sick7.3%6,257
Fatiguetiredness7%5,995
Disease progressionthe disease advanced5.5%4,734
Myelosuppression5.4%4,582
Deaththe patient died; cause not stated by this term5.2%4,457
Vomitingbeing sick4.8%4,129
Dyspnoeashortness of breath4.4%3,745
Pyrexiafever4%3,448
Neuropathy peripheralnerve damage in hands or feet3.6%3,049
Neutropenialow neutrophils, a type of white blood cell3.6%3,041
Astheniaweakness or lack of energy3.5%2,986
Ejection fraction decreased3.2%2,755
Anaemialow red blood cells3.1%2,664
Rashskin rash3.1%2,664
Alopeciahair loss3%2,529
Headachehead pain2.8%2,415
Febrile neutropeniafever with low white blood cells2.5%2,162
Metastases to central nervous system2.5%2,106
Decreased appetitereduced appetite2.5%2,105
Painpain, site not specified2.2%1,863
Chillschills or shivering2.1%1,824
Pneumonialung infection2.1%1,804
Thrombocytopenialow platelets2.1%1,804

Solid bar: share of all class reports. Hollow bar: the median share across the 6 member drugs, the reference used on each member's page. One report can record several terms.

Outcomes, patients and reporters

Outcomes recorded

Death12%10,306

Life-threatening4.1%3,544

Hospitalisation (initial or prolonged)32%27,337

Disability1.9%1,621

Congenital anomaly0.2%170

Other serious55.2%47,188

Not serious13.4%11,500

Patient age

Under 20.1%77

2 to 110%15

12 to 170%3

18 to 4412.3%10,491

45 to 6433.6%28,769

65 to 7412%10,246

75 and over5.2%4,437

Age not given36.8%31,515

Who reported

Physician48.3%41,297

Pharmacist6.8%5,777

Other health professional28.5%24,377

Lawyer0.7%619

Consumer or non-health professional14.6%12,508

Not given1.1%975

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 HER2/neu receptor antagonist reports

Which drugs are in the HER2/neu receptor antagonist class on this site?

Herceptin, Trastuzumab, Perjeta, Pertuzumab, Kanjinti and Ontruzant. Class membership comes from the pharmacologic class (EPC) on the drug's FDA label.

How many reports does the class have?

85,553 reports through June 2026, 5,681 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?

diarrhoea (11.5%), off label use (7.3%), nausea (7.3%), fatigue (7%) and disease progression (5.5%).

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.