A Phase 2 Study of Osimertinib and S-1 in Treatment Resistant EGFR Mutant NSCLC

Trial number:
Trial phase:
Study type:
Targeted therapy
Overall status:
Not yet recruiting

Study start date

August, 2023

Scientific title

A Phase 2 Study of Osimertinib and S-1 in Treatment Resistant EGFR Mutant NSCLC (SOS-1 Study)


The objective of this study is to determine overall response rate to combination of S-1 and Osimertinib in treatment-resistant EGFR mutant lung cancer.

Patients must have histologically or cytologically confirmed EGFR mutant NSCLC.Patients must have measurable disease, defined as at least one lesion that can be accurately measured in at least one dimension (longest diameter to be recorded for non-nodal lesions and short axis for nodal lesions) as >20 mm with conventional techniques or as >10 mm with spiral CT scan, MRI, or calipers by clinical exam. Prior therapy: Patient with recurrent and/or metastatic EGFR mutant NSCLC, that has progressed on osimertinib as most recent line of treatment, and the primary doctor intends to continue with osimertinib treatment. Patients with no matched alterations (tumor or plasma) where clinical trials or approved systemic anti-cancer therapy are available, are eligible Patients with matched alterations on rebiopsy (tumor or plasma) who declined matching clinical trials, or approved systemic anti-cancer therapy, are eligible Age ≥21 years. ECOG performance status ≤2 (Karnofsky ≥60%, see Appendix A).

Patients must have adequate organ and marrow function as defined below:

absolute neutrophil count ≥1,500/mcLplatelets ≥100,000/mcL total bilirubin ≤ institutional upper limit of normal (ULN) AST(SGOT)/ALT(SGPT) ≤3 × institutional ULN creatinine ≤ institutional ULN OR glomerular filtration rate (GFR) ≥50 mL/min/1.73 m2 Human immunodeficiency virus (HIV)-infected patients on effective anti-retroviral therapy with undetectable viral load within 6 months are eligible for this trial provided that DDI with osimertinib has been addressed. For patients with evidence of chronic hepatitis B virus (HBV) infection, the HBV viral load must be undetectable on suppressive therapy, if indicated. Patients with a history of hepatitis C virus (HCV) infection must have been treated and cured. For patients with HCV infection who are currently on treatment, they are eligible if they have an undetectable HCV viral load. Patients with treated brain metastases are eligible if follow-up brain imaging after central nervous system (CNS)-directed therapy shows no evidence of progression. Patients with asymptomatic new or progressive brain metastases (active brain metastases) or leptomeningeal disease are eligible if the treating physician determines that immediate CNS specific treatment is not required and is unlikely to be required during the first cycle of therapy. Patients with a prior or concurrent malignancy whose natural history or treatment does not have the potential to interfere with the safety or efficacy assessment of the investigational regimen are eligible for this trial. Patients with known history or current symptoms of cardiac disease, or history of treatment with cardiotoxic agents, should have a clinical risk assessment of cardiac function using the New York Heart Association Functional Classification. To be eligible for this trial, patients should be class 2B or better. The effects of S-1 on the developing human fetus are unknown. For this reason and because cytotoxic agents are known to be teratogenic, women of childbearing potential (WOCBP) must use appropriate method(s) of contraception. WOCBP must have a negative serum or urine pregnancy test (minimum sensitivity 25 IU/L or equivalent units of HCG) within 24 hours prior to the start of treatment. Women must not be breastfeeding. Men who are sexually active with WOCBP must use any contraceptive method with a failure rate of less than 1% per year. Ability to understand and the willingness to sign a written informed consent document.

Study design

Primary purpose: Treatment, Allocation: N/A, Intervention model: Single Group Assignment, Masking: None (Open Label),



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