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What the label lists and what reports show

Lazertinib side effects

Lazertinib's FDA label: “The most common adverse reactions (≥ 20%) were rash, nail toxicity, infusion-related reaction (amivantamab), musculoskeletal pain, edema, stomatitis, VTE, paresthesia, fatigue, diarrhea, constipation, COVID-19, hemorrhage, dry skin, decreased appetite …” FAERS holds 706 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 rash (134 reports).

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Check it at the source: the lazertinib FDA label on DailyMed (effective May 5, 2026, Janssen Biotech, 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 LAZCLUZE?

LAZCLUZE may cause serious side effects, including: blood clot problems. Blood clots in the veins of your legs (deep vein thrombosis) or lungs (pulmonary embolism) are serious, but common, and may lead to death. Your healthcare provider will start you on medicine to reduce the risk of blood clots for the first four months of treatment. Tell your healthcare provider right away if you have any signs and symptoms of blood clots, including swelling, pain or tenderness in the leg, sudden unexplained chest pain, or shortness of breath. lung problems. LAZCLUZE may cause lung problems that may lead to death. Symptoms may be similar to those symptoms from lung cancer. Tell your healthcare provider right away if you get any new or worsening lung symptoms, including shortness of breath, cough, or fever. skin problems. […]

Source: FDA drug label, Janssen Biotech, Inc., effective May 5, 2026 (SPL set c417f9ee-2027-4ed5-92ad-3c19266de16c), via openFDA; the full label on DailyMed

What does the label list?

From the label: adverse reactions

The most common adverse reactions (≥ 20%) were rash, nail toxicity, infusion-related reaction (amivantamab), musculoskeletal pain, edema, stomatitis, VTE, paresthesia, fatigue, diarrhea, constipation, COVID-19, hemorrhage, dry skin, decreased appetite, pruritus, and nausea.

Table 3: Adverse Reactions (≥ 10%) in Patients with NSCLC with Exon 19 Deletion or Exon 21 L858R Substitution Mutations in MARIPOSA

ReactionAll Grades (%)Grade 3 or 4 (%)All Grades (%)Grade 3 or 4 (%)
Rash Grouped terms8626481.2
Nail toxicity7111340.7
Dry skin251180.2
Pruritus240.5170.2
Infusion-related reaction Applicable only to amivantamab63600
Musculoskeletal pain472.1391.9
Stomatitis432.4270.5
Diarrhea312.6450.9
Constipation290130
Nausea211.2140.2
Vomiting120.550
Abdominal pain110100
Hemorrhoids100.22.10.2
Edema432.680
Fatigue323.8201.9
Pyrexia12090
Venous thromboembolism361182.8
Hemorrhage251131.2
Paresthesia351.7100.2
Dizziness140100
Headache130.2130
COVID-19261.7241.4
Conjunctivitis110.21.60
Decreased appetite241181.4
Cough190230

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, continued

The following adverse reactions are discussed elsewhere in the labeling: Venous Thromboembolic Events [see Warnings and Precautions (5.1) ] Interstitial Lung Disease/Pneumonitis [see Warnings and Precautions (5.2) ] Dermatologic Adverse Reactions [see Warnings and Precautions (5.3) ] Hepatotoxicity [see Warnings and Precautions (5.4) ] Ocular Toxicity [see Warnings and Precautions (5.5) ] LAZCLUZE in Combination with Amivantamab The most common adverse reactions (≥ 20%) were rash, nail toxicity, infusion-related reaction (amivantamab), musculoskeletal pain, edema, stomatitis, VTE, paresthesia, fatigue, diarrhea, constipation, COVID-19, hemorrhage, dry skin, decreased appetite, pruritus, and nausea. ( 6.1 ) The most common Grade 3 or 4 laboratory abnormalities (≥ 2%) were decreased albumin, decreased sodium, increased ALT, decreased potassium, decreased hemoglobin, increased AST, increased GGT, and increased magnesium. ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Janssen Biotech, Inc. at 1-800-526-7736 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.

Source: FDA drug label, Janssen Biotech, Inc., effective May 5, 2026 (SPL set c417f9ee-2027-4ed5-92ad-3c19266de16c), via openFDA; the full label on DailyMed

What do FAERS reports show?

706 reports list lazertinib among the medicines taken, each a report of something that happened, not proof the medicine caused it; 32 are coded as a death and 175 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 24 reactions below, 17 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?

Lazertinib: the full record
label, generics, price, shortages, recalls
Side effects hub
the most reported medicines and reactions