Introduction: Epidermal Growth Factor Receptor (EGFR) mutation is a crucial biomarker in selecting appropriate therapies for NSCLC patients. Gefitinib, a first-generation EGFR-TKI, is commonly used as initial treatment for EGFR-mutant NSCLC at Dr. Soetomo General Hospital. Gefitinib is available in two variants: Iressa (originator) and Gefitero (me-too drug). Methods: This analytic observational study was conducted in January 2017 - January 2022, involving NSCLC patients with positive EGFR mutations who received Gefitinib as first-line treatment at Dr. Soetomo General Hospital. Adverse effects, semisubjective responses, objective responses, and PFS were compared among two Gefitinib therapy groups (Iressa, Gefitero) using Fishers exact test and Mann-Whitneys test. Results: A total of 65 subjects are characterized by mean age 59,7 years old, with the majority encompassing male subjects (52,3%), with stage IV disease (95,4%), and exon 19 mutation (60,0%). Iressa was the most frequently administered drug (89,2%), followed by Gefitero (10,8%). Skin toxicity was the primary adverse effect across all Gefitinib therapies (50,8%), while weight loss was more prevalent within the Iressa group (48,3%). Stable Disease (SD) was the most frequently reported response therapy (66,2%). The Iressa group had a longer median PFS compared to Gefitero (6 vs 4 months). However, there were no significant differences regarding side effects, weight changes, response therapy, and PFS between the different Gefitinib therapies. Conclusion: There were no significant differences of therapy responses between the first generation of EGFR TKI originator and their me-too drug.