Abstract LB277: Exposure response and safety analysis of osimertinib in combination with pemetrexed and platinum-based chemotherapy for the first-line treatment of locally advanced or metastatic NSCLC patients with EGFRm (FLAURA2)

Abstract Osimertinib (Osi) is a potent, CNS-active irreversible inhibitor of epidermal growth factor receptor-mutate (EGFRm) and T790M mutations. It is currently approved as the standard of care in patients with locally advanced (Stage IIIB or IIIC) or metastatic (Stage IV) EGFR T790M mutation-positive NSCLC whose disease has progressed on or after EGFR-TKI therapy and as the first-line agent in patients with locally advanced or metastatic EGFRm NSCLC. FLAURA2 is a global, randomized, open-label, multi-center phase III clinical study to investigate the safety and efficacy of Osi 80 mg once daily in combination with platinum-pemetrexed chemotherapy compared to Osi monotherapy, as a first-line treatment in patients with locally advanced or metastatic EGFRm NSCLC. This study is ongoing and an sNDA has been submitted for approval. The objectives of this current analyses were to 1) assess the exposure-efficacy relationship between population PK model-derived Osi exposure metrics (AUCss, Cmaxss, Cminss), and PFS in patients from the investigational arm (Osi + chemotherapy arm, n=244) of FLAURA2 study and 2) assess the relationship between Osi exposure metrics and key safety endpoints. The exposure response (ER) relationship between Osi and progression free survival (PFS) in patients enrolled in the investigational arm of FLAURA2 was assessed. Kaplan Meier plots with patients stratified by quartile exposure of Osi in the investigational arm indicated no clear ER relationship, though there appears to be a trend of lower PFS with highest AUCss quartile. A stepwise Cox proportional hazard analysis indicated that the effect of Osi exposure metrics were not statistically significant associated with PFS; however, the number of pemetrexed cycles appeared to be a significant covariate on PFS. The relationship between Osi exposure metrics and AEs CTCAE Grade 3 and above causally related to Osi, as well as AESIs from the investigational arm of FLAURA2 study were explored. The graphical exploration and logistic regression analysis did not identify statistically significant relationship of Osi exposures on CTCAE ≥ Grade 3 adverse events (AEs) causally related to Osi, AEs leading to Osi dose interruptions/reductions/discontinuations, and AESIs including ≥ Grade 3 haematological AEs, cardiac effects, left ventricular ejection fraction decrease and ≥ Grade 1 interstitial lung disease causally related to Osi. In conclusions, no statistically significant relationships between exposure of Osi and response were observed, supporting the recommended dose of Osi of 80 mg daily in the FLAURA2 patient population. Overall, the recommended dose of Osi as monotherapy or in combination with chemotherapy is 80 mg once daily, with a dose reduction to 40 mg daily if unacceptable toxicity is observed. Citation Format: Jincheng Yang, Damilola Olabode, Aarti Sawant, Karthick Vishwanathan, Srinivas Bachina, Alexandar Todd, Dana Ghiorghiu, Yuri Rukazenkov, Alex Phipps, Diansong Zhou, Azar Shahraz. Exposure response and safety analysis of osimertinib in combination with pemetrexed and platinum-based chemotherapy for the first-line treatment of locally advanced or metastatic NSCLC patients with EGFRm (FLAURA2) abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (7Suppl): Abstract nr LB277.