Osimertinib can cause adverse reactions ranging from mild and manageable effects to uncommon but potentially life-threatening complications. Not every patient experiences the same effects.
The safety profile differs somewhat depending on whether osimertinib is used alone or with chemotherapy.
Common adverse effects
U.S. prescribing information identifies common reactions during osimertinib monotherapy including:
- Diarrhea
- Rash
- Musculoskeletal pain
- Nail toxicity
- Dry skin
- Stomatitis
- Fatigue
- Changes in blood cell counts, including leukopenia, lymphopenia, thrombocytopenia, anemia and neutropenia
The EMA also identifies diarrhea, rash, paronychia, dry skin and stomatitis among common effects with Tagrisso monotherapy.
Diarrhea
Diarrhea is one of the characteristic adverse effects of EGFR-targeted treatment. Persistent or severe diarrhea can cause dehydration and electrolyte disturbances. Patients should discuss significant or ongoing diarrhea with their healthcare team.
Skin and nail changes
Rash, dry skin, nail inflammation or other nail changes can occur. Patients should report severe skin reactions or rapidly worsening symptoms.
Mouth inflammation
Stomatitis can cause painful mouth irritation and may interfere with eating or drinking.
Blood-count abnormalities
Osimertinib may affect blood cell counts. Clinicians may use laboratory testing to monitor for clinically important abnormalities.
Serious adverse reactions
Important potentially serious risks include:
| Risk | Why it matters |
| ILD/pneumonitis | Can be severe or fatal |
| QTc prolongation | May increase risk of serious cardiac rhythm problems |
| Cardiomyopathy | Can impair heart function |
| Keratitis | Can threaten ocular health if severe |
| SJS/TEN/EMM | Severe skin and mucosal reactions |
| Cutaneous vasculitis | May involve blood vessels and systemic organs |
| Aplastic anemia | Serious bone-marrow failure |
| Embryo-fetal toxicity | Can harm a developing fetus |
Warning signs requiring prompt attention
Patients should seek urgent medical assessment for:
- New or worsening shortness of breath
- New cough accompanied by fever or breathing difficulty
- Fainting or severe palpitations
- New swelling or symptoms suggesting heart failure
- Significant eye pain, redness, light sensitivity or vision changes
- Extensive blistering or peeling of the skin
- Severe mucosal lesions
- Unexplained bleeding or bruising
- Severe weakness associated with abnormal blood counts
Side effects do not mean treatment should automatically stop
A healthcare professional may manage adverse reactions through supportive treatment, temporary interruption, dose reduction or permanent discontinuation depending on severity and the relevant prescribing information.