Osimertinib mesylate is a kinase inhibitor, prescribed for the treatment of patients, who are diagnosed with metastatic epidermal growth factor receptor (EGFR) T790M mutation positive non-small cell lung cancer (NSCLC). The Innovator of the product is AstraZeneca and its brand name in US and EU market is TAGRISSO® (Osimertinib) 40 mg and 80 mg film coated Tablets. The recommended dose is one 80 mg tablet once daily taken orally with or without a meal. Approximately, 80-90 % of lung cancer comprise NSCLC. Solubility of Osimertinib is known to be affected by pH, it belongs to BCS class-III molecule. The current work attempted to study the impact of both particle size of API and concentrations of disintegrant (L-HPC) on in vitro drug release profiles of Osimertinib from tablet dosage form in comparison to in vitro drug release profiles of corresponding Innovator product in US market. Based on the scientific discussion of TAGRISSO® in EU market, and to increase the flow properties of blend for compression into tablets, dry granulation method (by Roller compaction) was adopted. Assay and in vitro dissolution of the finished product was analysed by UV method. The obtained dissolution results suggested that 500 ml of pH 4.5 Acetate buffer at 25 rpm was found to be more discriminatory media than pH 6.8 Phosphate buffer and pH 1.3 (containing 0.2 % NaCl) and film coated tablets with input micronized API (<10μ) has shown similar physical characteristics (hardness, disintegration time) and in vitro drug release profiles to that of Innovator product.