Phase I dose-escalation and -expansion study of buparlisib (BKM120), an oral pan-Class I PI3K inhibitor, in patients with advanced solid tumors

Purpose The pan-Class I PI3K inhibitor buparlisib (BKM120) has shown activity in a range of preclinical cancer models. This first-in-man study was initiated to identify the maximum tolerated dose (MTD) of buparlisib (100 mg/day) and to assess safety and preliminary efficacy. Methods Patients with advanced solid tumors (N = 83) enrolled in a Phase I dose-escalation and -expansion study of single-agent buparlisib. Patients in the dose-expansion arm (n = 43) had tumor samples with PIK3CA and/or PTEN alterations. Results The most common cancers were colorectal (n = 31) and breast cancer (n = 21). Median number of prior antineoplastic regimens was four (range: 1–12). Grade 3/4 adverse events (AEs) included asthenia (12.0 %) and performance status decrease (9.6 %). Treatment-related AEs (all grades) included decreased appetite, diarrhea, nausea (each in 33 % of patients), hyperglycemia (31 %) and rash (29 %). One confirmed partial response (PR; triple-negative breast cancer) and three unconfirmed PRs (parotid gland carcinoma, epithelioid hemangiothelioma, ER + breast cancer) were reported. Tumor molecular status did not predict clinical benefit in the full study cohort, or among the colorectal or breast cancer subpopulations. Pharmacodynamic biomarkers (¹⁸F-FDG-PET, C-peptide, pS6) demonstrated dose-dependent changes; however, tumor heterogeneity precluded a clear correlation with clinical benefit. Conclusion Buparlisib was well tolerated up to the 100 mg/day dose and showed preliminary activity in patients with advanced cancers. Future studies in more homogeneous patient populations will evaluate buparlisib in combination with other agents and further investigate the use of predictive biomarkers.