Osimert 80 mg contains Osimertinib, a third-generation epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI). It is primarily indicated for the treatment of non-small cell lung cancer (NSCLC) in patients whose tumors harbor specific EGFR mutations. Osimertinib is particularly effective against the T790M resistance mutation and demonstrates strong efficacy both as a first-line therapy and in later stages of NSCLC progression.

Mechanism of Action
Osimertinib selectively and irreversibly inhibits mutant forms of EGFR, including sensitizing mutations (e.g., L858R and exon 19 deletions) and the T790M resistance mutation, which commonly arises after treatment with earlier-generation EGFR inhibitors. By binding to these mutant receptors, Osimertinib blocks the signaling pathways that promote cancer cell growth and survival. It has minimal activity against wild-type EGFR, helping reduce the risk of off-target side effects.

Indications
Osimert 80 mg is indicated for:

• First-line treatment of metastatic NSCLC with EGFR exon 19 deletions or exon 21 L858R mutations.

• Second-line treatment of metastatic NSCLC with EGFR T790M mutation-positive status in patients who have progressed on or after previous EGFR TKI therapy.

• Adjuvant therapy following surgical resection in early-stage NSCLC with EGFR mutation-positive tumors.

Dosage and Administration

• The recommended dose is one tablet orally once daily, with or without food, taken at the same time each day.

• If a dose is missed, take it as soon as remembered on the same day unless it is almost time for the next dose.

• Tablets should be swallowed whole. For patients who have difficulty swallowing, tablets can be dissolved in non-carbonated water and consumed immediately.

Pharmacokinetics

• Osimertinib is well absorbed orally, reaching peak plasma levels in approximately 6 hours.

• It is mainly metabolized by CYP3A4 and CYP3A5 enzymes in the liver.

• The elimination half-life is around 48 hours, supporting once-daily dosing.

• Excretion occurs primarily via feces, with minimal renal clearance.

Side Effects
Common side effects:

• Diarrhea

• Rash

• Dry skin

• Nail inflammation

• Fatigue

• Mouth ulcers (stomatitis)

• Reduced appetite

Serious side effects:

• Interstitial lung disease/pneumonitis (may be life-threatening; discontinue immediately if suspected)

• QT interval prolongation (risk of cardiac arrhythmias)

• Cardiomyopathy (monitor left ventricular ejection fraction)

• Thrombocytopenia and anemia (regular blood monitoring recommended)

• Eye disorders (e.g., keratitis, conjunctivitis)

Contraindications and Precautions

• Contraindicated in patients with known hypersensitivity to Osimertinib or any excipients.

• Use caution in patients with a history of cardiovascular or pulmonary disease.

• Liver and kidney function should be assessed before and during treatment.

• Women of childbearing potential should avoid pregnancy during and at least 6 weeks after treatment; men with partners of childbearing potential should use effective contraception during treatment and for 4 months afterward.

Drug Interactions

• Strong CYP3A4 inducers (e.g., rifampin, phenytoin, carbamazepine) may reduce Osimertinib efficacy.

• CYP3A4 inhibitors (e.g., ketoconazole, clarithromycin) may increase plasma concentrations.

• Caution with other drugs that prolong the QT interval.

• Proton pump inhibitors and antacids have minimal effect on absorption.

Clinical Efficacy

• FLAURA trial: Osimertinib significantly improved progression-free survival (PFS) and overall outcomes compared to first-generation EGFR TKIs in first-line therapy.

• AURA3 trial: Demonstrated efficacy in T790M mutation-positive patients who progressed on prior EGFR TKIs, with better PFS and symptom control.

• ADAURA trial: Reduced risk of disease recurrence in early-stage NSCLC as adjuvant therapy.

Storage and Handling

• Store at 15–30°C in the original packaging to protect from moisture and light.

• Keep out of reach of children.

Conclusion
Osimert 80 mg (Osimertinib) is a major advancement in targeted therapy for EGFR-mutated NSCLC, offering significant survival benefits with a favorable safety profile. Its ability to target both sensitizing and resistance mutations makes it a versatile and essential option for multiple stages of lung cancer. Treatment should be supervised by an experienced oncologist to maximize benefits and ensure patient safety.