• Provide a signed and dated informed consent form (ICF) prior to any study specific procedures, sampling, and analyses.

• Aged at least 18 years old at the time of ICF signature.

• Complete resection (R0) of the primary tumor and histologically confirmed diagnosis of NSCLC (participants with tumor histology indicative of neuroendocrine carcinoma, sarcomatoid carcinoma, or small cell lung cancer should be excluded).

‣ Complete surgical resection of the primary NSCLC is mandatory. All gross lesions must be completely resected to achieve microscopically negative margins. Hilar and mediastinal lymph node dissection should be performed per clinical guidelines.

⁃ Acceptable surgery type: lobectomy, sleeve lobectomy, bilobectomy, or pneumonectomy.

⁃ Acceptable surgery approach: thoracotomy or thoracoscopic surgery.

• Participants must have NSCLC classified post-operatively as stage IB, II, or IIIA according to the AJCC TNM staging 9.0th edition.

• Have documented EGFR exon20ins (Cohort 1) or EGFR PACC mutations (Cohort 2) from a local Clinical Laboratory Improvement Amendments (CLIA)-certified laboratory (or equivalent).

• • Common EGFR PACC mutations include, but not limited to, L718Q, G719X, S768I, L747P/S, V769L, E709\_T710delinsD, L792H, and T854I.

• Participants must provide sufficient tumor tissue samples for confirmation of EGFR mutations by the sponsor designated central laboratory.

• ECOG performance status is 0 or 1.

• Participants must recover from prior lung surgery and systemic therapy (e.g., neoadjuvant therapy and/or adjuvant chemotherapy) without Grade 1 or higher AEs (except alopecia of any grade and ≤ Grade 2 platinum-associated neuropathy) at randomization.

‣ Participants who have not previously received adjuvant chemotherapy should be randomized as early as 4 weeks and within 10 weeks after the radical surgery.

⁃ Participants who have previously received adjuvant chemotherapy can be randomized within 2 - 10 weeks of completion of adjuvant chemotherapy with a maximum interval of no more than 26 weeks from surgery to randomization. The adjuvant chemotherapy can start as early as 4 weeks after the radical surgery, in 21-day cycles, and up to 4 cycles.

• Adequate bone marrow reservation or organ functions within 7 days prior to randomization.

⁃ Male participants with female partners of child-bearing potential should use barrier contraceptives (e.g., by use of condoms), during their participation in this study and for 6 months following the last dose of the study drug. Male participants must refrain from donating sperm during their participation in the study and for 6 months following the last dose of the study drug. If male participants wish to father children, they should be advised to arrange for freezing of sperm samples prior to the start of study drug.

⁃ Female participants of child-bearing potential should use reliable contraceptives from the time of screening until 2 months after discontinuation of study drug. Female participants should not be breast feeding and must have a negative pregnancy test (serum or urine β-human chorionic gonadotropin) prior to start dosing or must fulfil one of the following criteria at screening:

∙ Post-menopausal defined as aged at least 50 years old and amenorrhea for at least 12 months following cessation of all exogenous hormonal treatment.

‣ Women under 50 years old would be considered postmenopausal if they have been amenorrheic for ≥ 12 months following cessation of exogenous hormonal treatments and with luteinizing hormone (LH) and follicle-stimulating hormone (FSH) levels in the post-menopausal range.

‣ Documentation of irreversible surgical sterilization by hysterectomy, bilateral oophorectomy or bilateral salpingectomy but not tubal ligation.