Phase I pharmacokinetic (PK), and pharmacodynamic (PD) trial of the novel oral Notch inhibitor MK-0752 in patients (pts) with advanced breast cancer (BC) and other solid tumors

Abstract

10574 Introduction: Activation of Notch signaling occurs in ∼40% of human BCs and high Notch expression is associated with poor outcome. Inhibition of Notch inhibits BC cell proliferation in vitro. Notch signaling requires gamma secretase (GS), which cleaves Notch, releasing the Notch intracellular domain (NICD) to activate transcription of target genes. MK-0752 is a potent GS inhibitor. Methods: In Part 1 of the study, pts with advanced solid tumors were enrolled using an accelerated dose escalation with 1 pt/dose level until the occurrence of ≥Grade 2 toxicity, then 3–6 pts/dose level. MK-0752 was administered by once-daily oral dosing in 28-day cycles. Once a maximum tolerated dose (MTD) was established, an additional 22 pts with advanced BC were to be enrolled in Part 2. Six-point PK plasma profiles were collected over 24 hours on Days 1 and 28 and assayed by LC/MS/MS. PD measurement of plasma Abeta40 peptide (another gamma secretase substrate) was performed pre/post dose on Days 1 and 28. Tumor biopsies on Days 1 and 28 were obtained from a subset of pts to assess changes in Notch activity by immunohistochemical analysis of NICD. Results: In Part 1, two pts were enrolled at 450mg daily, and five pts at 600mg daily. Dose-limiting toxicities (DLTs) were Grade 3 diarrhea, constipation, nausea, and abdominal cramping at 600 mg. In Part 2, an additional 14 pts with BC were enrolled at 450mg daily. In this cohort, Grade 2/3 fatigue requiring dose reduction occurred in 6 pts. Grade 3 diarrhea (1pt), nausea (1 pt) and elevated liver transaminases (2 pt) were also observed. Mean PK parameters (at 450mg, 600 mg) on Day 1 were AUC0–24hr = 1036, 1065μM·hr, Cmax = 72, 61μM, C24hr = 25, 32μM, and tmax = 3, 7 hr. PD measurements of GS inhibition showed a 12–78% (mean 46%) decrease in plasma Abeta40 at 4 hours on Day 1 compared to predose. Conclusion: Continuous dosing of MK-0752 at 450mg daily in pts with BC was associated with significant toxicity, predominantly fatigue, and cannot be considered a MTD. An intermittent dosing schedule is being explored. MK-0752 at all doses inhibited GS, as demonstrated by decreases in plasma Abeta40. Analysis of efficacy and intratumoral Notch inhibition will be reported at the meeting. [Table: see text]