Phase II trial of the phosphatidyinositol-3 kinase (PI3K) inhibitor BKM120 in recurrent glioblastoma (GBM).

Abstract

2015 Background: The PI3K pathway is activated in most GBMs and represents a potential therapeutic target. BKM120 is an oral, pan-Class I PI3K inhibitor that enters the brain at therapeutic concentrations demonstrated to inhibit PI3K pathway, and potently inhibits the growth of U87 GBM tumors and human glioma tumor spheres in vitro and in vivo. Methods: The Ivy Foundation Early Phase Clinical Trials Consortium is conducting a phase II study of BKM120 in recurrent GBM patients with activation of the PI3K pathway (mutation, homozygous deletion or loss of IHC of PTEN, PIK3CA or PIK3RI mutations, or detectable pAKT). Additional eligibility criteria included radiologic progression, 1st or 2nd relapse, > 18 yrs, KPS > 60, adequate bone marrow and organ function, controlled blood glucose, and no enzyme-inducing antiepileptic drugs. Patients received BKM120 100mg daily. The study consisted of 2 parts conducted concurrently. Part 1 involved up to 15 patients who received BKM120 daily for 8-12 days prior to surgery for recurrent disease. Patients underwent FDG PET, pharmacokinetic (PK) studies, and tumor was obtained for drug concentrations and pharmacodynamic effects. Part 2 consisted of up to 50 patients with unresectable GBM treated with BKM120. The primary endpoint for Part 2 was 6-month progression-free survival (p0 =15%; p1= 32%). Results: To date 7 patients have been enrolled into Part 1, 33 into part 2. There were 5 women and 35 men. Median age was 54 yrs (29-68). Treatment was fairly well-tolerated. Major grades 3/4 toxicities were asymptomatic lipase elevation (5), fatigue (3), hyperglycemia (3), rash (3) elevated AST (1), and depression (1). Analysis of tumor from Part 1 showed reduction of pAkt by IHC. Genotyping of tumor specimens is ongoing. To date 33 patients had positive pAkt, 21 had PTEN loss by IHC. Of the first 19 patients who underwent whole exome sequencing, 3 had PIK3Ca mutations and 6 had PTEN mutations. Conclusions: BKM120 is generally well tolerated in patients with recurrent GBM and achieves adequate tumor concentration to inhibit pAkt. Updated PK and efficacy data and correlation of the latter with tumor genotype will be presented. Clinical trial information: NCT01339052.