Phase I Dose-Escalation Study of Pilaralisib (SAR245408, XL147), a Pan-Class I PI3K Inhibitor, in CombinationWith Erlotinib in Patients With Solid Tumors

Background: This phase I study evaluated the maximum tolerated dose (MTD), safety, pharmacokinetics (PK), and pharmacodynamics of pilaralisib (SAR245408), an oral pan-class I phosphoinositide 3-kinase (PI3K) inhibitor, in combination with erlotinib, an epidermal growth factor receptor (EGFR) inhibitor. Methods: In a 3 + 3 dose-escalation study, patients with advanced solid tumors received pilaralisib capsules once daily (21 days per 28-day cycle; 50-600 mg) plus erlotinib tablets once daily (28 days per 28-day cycle; 100 or 150 mg). An MTD expansion cohort of patients with non-small cell lung cancer who had previously received treatment with an EGFR inhibitor was included. Results: Thirty-five patients were enrolled. Only one patient had an EGFR activating mutation. One dose-limiting toxicity was reported (grade 4 drug reaction or rash with eosinophilia and systemic symptoms). MTD was pilaralisib 400 mg plus erlotinib 150 mg. The most commonly reported treatment-related adverse events were rash (62.9%), diarrhea (42.9%), and fatigue (40.0%). Pilaralisib PK findings were consistent with previous studies, suggesting erlotinib had no effect on pilaralisib pharmacokinetics. Pharmacodynamic analyses indicated moderate inhibition of PI3K, mitogen-activated protein kinase, and EGFR pathways. Of 27 evaluable patients, one had a partial response (3.7%) and 14 (51.9%) had stable disease. There was no association between molecular alterations of PI3K pathway components and clinical activity. Conclusion: Pilaralisib plus erlotinib had limited antitumor activity. Safety findings were similar to recent studies of single-agent pilaralisib or other PI3K inhibitors.