The purpose of this study is to evaluate efficacy and safety of osimertinib (tablet) in combination with Dato-DXd (i.v. infusion) compared with osimertinib (tablet) monotherapyas a first-line therapy in participants with locally advanced or metastatic EGFRm (Ex19del and/or L858R) NSCLC.

Study details include:

1. The study duration will be event-driven, with an estimated duration of approximately 8 years.
2. Participants may receive study treatment until disease progression, unacceptable toxicity, or other specific discontinuation criteria are met.
3. The visit frequency will be every 3 weeks during the treatment period.

Note: Participants on osimertinib treatment(osimertinib only arm or who have discontinued Dato-DXd while are still receiving osimertinib) are required to attend visits to perform assessments every 6 weeks from Cycle 7 until Cycle 17 and then visits every 12 weeks until disease progression or IP discontinuation. Participants who are receiving osimertinib + Dato-DXd are still required to attend visit to perform assessment every 3 weeks (q3w) per SoA.

This is a global Phase III, open-label, randomised, multicentre study assessing the efficacy and safety of osimertinib in combination with Datopotamab Deruxtecan compared with osimertinib in participants with locally advanced or metastatic EGFRm (Ex19del and/or L858R) NSCLC who have not received any prior therapy for advanced disease.

Inclusion Criteria:

Age

1. Participant must be ≥ 18 years.

   Type of Participant and Disease Characteristics

2. Histologically or cytologically documented nonsquamous NSCLC. NSCLC of mixed histology is allowed if adenocarcinoma is the predominant histology. Mixed small-cell lung cancer and NSCLC histology, and sarcomatoid variant of NSCLC is ineligible.

3. Stage IIIB or IIIC or Stage IV metastatic NSCLC or recurrent NSCLC (based on the American Joint Committee on Cancer Edition 8) not amenable to curative surgery or definitive chemoradiation at the time of randomisation.

4. Participants must not have received prior EGFR TKIs or other systemic therapy for Stage IIIB, IIIC or IV NSCLC.

5. The tumour harbors at least 1 of the 2 common EGFR mutations known to be associated with EGFR-TKI sensitivity (Ex19del or L858R), either alone or in combination with other genomic alterations, which may include EGFR T790M, assessed by a CLIA-certified (US sites) or an accredited (outside of the US) local laboratory or by central prospective tissue testing.

6. For participants enrolled in randomisation period, mandatory provision of an unstained, archival tumour tissue sample in a quantity sufficient to allow for central confirmation of the EGFR mutation status.

7. WHO performance status of 0 or 1.

8. At least one lesion not previously irradiated that qualifies as a RECIST 1.1 TL at baseline and can be accurately measured at baseline as ≥10 mm in the longest diameter (except lymph nodes, which must have short axis ≥15 mm) with CT or MRI and is suitable for accurate repeated measurements.

9. Adequate bone marrow reserve and organ function before the first dose of study intervention.

Exclusion Criteria:

1. As judged by the investigator, any evidence of diseases (such as severe or uncontrolled systemic diseases, including active bleeding diseases, history of allogenic organ transplant which, in the investigator's opinion, makes it undesirable for the participant to participate in the study or that would jeopardise compliance with the protocol.
2. Refractory nausea and vomiting, chronic gastrointestinal disease, inability to swallow the formulated product, or previous significant bowel resection that would preclude adequate absorption, distribution, metabolism, or excretion of osimertinib.
3. History of another primary malignancy.
4. Spinal cord compression and/or unstable brain metastases, as defined by Protocol.
5. Clinically significant corneal disease.
6. Has active or uncontrolled hepatitis B or C virus infection, as defined by Protocol.
7. Past medical history of ILD/penumonitis, including radiation pneumonitis (apart from radiation pneumonitis that did not require steroids), or drug-induced ILD/pneumonitis, or has suspected ILD/pneumonitis that cannot be ruled out by imaging at screening.
8. Pulmonary embolism within 3 months of the study enrolment or has severe pulmonary function compromise.
9. Has clinically severe pulmonary function compromise resulting from intercurrent pulmonary illnesses.

Qualified researchers can request access to anonymized individual patient-level data from AstraZeneca group of companies sponsored clinical trials via the request portal Vivli.org. All requests will be evaluated as per the AZ disclosure commitment: https://astrazenecagrouptrials.pharmacm.com/ST/Submission/Disclosure.

Yes, indicates that AZ are accepting requests for IPD, but this does not mean all requests will be shared.

AstraZeneca will meet or exceed data availability as per the commitments made to the EFPIA PhRMA Data Sharing Principles. For details of our timelines, please rerefer to our disclosure commitment at https://astrazenecagrouptrials.pharmacm.com/ST/Submission/Disclosure.

When a request has been approved AstraZeneca will provide access to the anonymized individual patient-level data via secure research environment Vivli.org. Signed Data Usage Agreement (non-negotiable contract for data accessors) must be in place before accessing requested information.