What the label lists and what reports show
Zongertinib side effects
Zongertinib's FDA label: “Most common adverse reactions (≥ 20%) are diarrhea, rash, hepatotoxicity, fatigue, nausea, musculoskeletal pain, and upper respiratory tract infection.” FAERS holds 124 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 diarrhoea (36 reports).
- No generic listed
Check it at the source: the zongertinib FDA label on DailyMed (effective August 13, 2026, Boehringer Ingelheim Pharmaceuticals, Inc.); 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 HERNEXEOS?HERNEXEOS may cause serious side effects, including: liver problems. Liver problems are common with HERNEXEOS and can be severe and life-threatening. Your healthcare provider will do blood tests to check your liver function before you start taking HERNEXEOS and during your treatment. Tell your healthcare provider right away if you develop any signs and symptoms of liver problems, including: yellowing of your skin or the white part of your eyes (jaundice) dark or brown (tea colored) urine pain on the upper right side of your stomach area (abdomen) bleeding or bruising more easily than normal feeling very tired loss of appetite nausea or vomiting heart problems that may affect your heart's ability to pump blood. HERNEXEOS can cause severe heart problems. Your healthcare provider will do tests to check your heart function before you start taking HERNEXEOS and during treatment. […]
Source: FDA drug label, Boehringer Ingelheim Pharmaceuticals, Inc., effective August 13, 2026 (SPL set d3fabf12-354e-4e5c-b5de-20fdb579b783), via openFDA; the full label on DailyMed
What does the label list?
From the label: adverse reactionsMost common adverse reactions (≥ 20%) are diarrhea, rash, hepatotoxicity, fatigue, nausea, musculoskeletal pain, and upper respiratory tract infection.
Table 3 Adverse Reactions (≥ 15%) in Patients with Non-Squamous NSCLC with HER2 TKD Mutations Who Received HERNEXEOS in Beamion LUNG-1
| Reaction | Adverse Reaction All Grades 1 % | HERNEXEOS N = 177 Grade 3 or 4 % |
|---|---|---|
| Diarrhea | 56 | 2.8 |
| Nausea | 25 | 0.6 |
| Stomatitis | 21 | 0 |
| Rash | 32 | 0.6 |
| Nail disorders | 21 | 0.6 |
| Pruritus | 15 | 0 |
| Fatigue | 26 | 0.6 |
| Headache | 16 | 0.6 |
| Cough | 23 | 0 |
| Musculoskeletal pain | 23 | 2.3 |
| Upper respiratory tract infections | 23 | 0 |
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 adverse reactions are discussed in greater detail in other sections of the labeling: Hepatotoxicity [see Warnings and Precautions (5.1) ] Left Ventricular Dysfunction [see Warnings and Precautions (5.2) ] Interstitial Lung Disease/Pneumonitis [see Warnings and Precautions (5.3) ] Most common adverse reactions (≥ 20%) are diarrhea, rash, hepatotoxicity, fatigue, nausea, musculoskeletal pain, and upper respiratory tract infection. ( 6.1 ) The most common (≥ 2%) Grade 3 or 4 laboratory abnormalities were decreased lymphocytes, increased alanine aminotransferase, increased aspartate aminotransferase, increased gamma glutamyl transferase, decreased potassium, and decreased neutrophils. ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Boehringer Ingelheim Pharmaceuticals, Inc. at 1-800-542-6257 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 clinical practice. …
Source: FDA drug label, Boehringer Ingelheim Pharmaceuticals, Inc., effective August 13, 2026 (SPL set d3fabf12-354e-4e5c-b5de-20fdb579b783), via openFDA; the full label on DailyMed
What do FAERS reports show?
124 reports list zongertinib among the medicines taken, each a report of something that happened, not proof the medicine caused it; 17 are coded as a death and 31 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, 8 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.
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?
- Zongertinib: 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