Results of a phase 1b study of osimertinib plus sapanisertib or alisertib for osimertinib-resistant, EGFR-mutant non–small cell lung cancer (NSCLC)

9105 Background: The aurora kinase and mTOR pathways are implicated in resistance to EGFR inhibitor osimertinib. Here, we investigated the safety and efficacy of the aurora kinase inhibitor alisertib and the mTOR inhibitor sapanisertib in combination with osimertinib. Methods: This is a phase 1b study with dose finding and expansion portions (NCT04479306). The dose finding portion used a Bayesian optimal interval (BOIN) design to assess two arms: osimertinib 80 mg daily in combination with alisertib 20 mg, 30 mg, and 40 mg daily day 1-21 of 28-day cycle (osi-ali arm) and osimertinib 80 mg daily in combination with sapanisertib 2 mg and 3 mg daily (osi-sapa arm). Dose limiting toxicities (DLTs) were predefined in the protocol. Patients with EGFR (L858R/exon 19 deletion) mutant NSCLC whose disease have progressed on osi and up to one additional line of systemic therapy were assigned, at investigator discretion, to either study arm. Tumor biopsy was mandatory at study entry and optional upon progression. Results: As of February 1, 2022, 40 patients are enrolled (20 in each arm). One DLT was observed in each arm: grade 3 nausea in ali-osi arm and grade 3 AST elevation in osi-sapa arm. Grade 3 treatment emergent adverse events (TEAEs) occurred in 10% of each arm, and no grade 4 TEAEs were observed. The most common TEAEs in osi-ali arm was leucopenia (45%) and anemia (35%) while in osi-sapa arm, hyperglycemia (45%) and stomatitis (40%). In osi-ali arm (n = 20), median progression free survival (mPFS) was 1.9 months while objective response rate (ORR) and disease control rate (DCR) were 5% (95% CI: 0.1 ̃ 24.9%) and 40% (95% CI: 19.1 ̃ 63.9%), respectively. In osi-sapa arm (n = 16, evaluated for response to date), mPFS was 4.6 months while ORR and DCR were 12.5% (95% CI: 1.6 ̃ 38.3%) and 68.7% (95% CI: 35.7 ̃ 82.7%), respectively. Conclusions: Osimertinib with alisertib or sapanisertib is well tolerated in osimertinib-resistant, EGFR mutant NSCLC. The sapanisertib combination, but not the alisertib combination, demonstrates antitumor activity suggesting that mTOR inhibition warrants further exploration in this population. Biomarker analysis is ongoing to identify the molecular determinants of response and resistance to sapasertib. Clinical trial information: NCT04479306.