Background: Activation of the PI3K pathway, by PIK3CA mutation or amplification or PTEN deletion, has been implicated in a wide variety of human cancers. PF-05212384 is a dual-specificity inhibitor of PI3K and mTOR that is formulated for intravenous (IV) administration. PF-05213384 is the first IV PI3K/mTOR inhibitor to be tested in a clinical trial.

Methods: In this ongoing phase 1 trial, PF-05212384 was administered once weekly, using a modified continual reassessment method (CRM) for estimation of the maximum tolerated dose (MTD). Assessments included safety (NCI CTC AE v4.0), pharmacokinetics (PK), pharmacodynamics (PD), and antitumor activity (RECIST v1.1). PD assessments included blood glucose and immunohistochemistry analysis of phosphoprotein biomarkers in tumor and surrogate tissue (hair follicles). The population was actively enriched for patients with dysregulation in the PI3K pathway.

Results: As of 15 March 2011, 47 patients have been enrolled at doses ranging from 10 mg to 319 mg. Median age was 58. Represented tumor types included CRC (8), NSCLC (4), ovarian/endometrial/cervical (8), salivary (3) and gastric/esophageal (3). Analysis of archived tumor biopsies revealed PI3K pathway alterations in 12/26 evaluable patients; alterations included PTEN loss, PIK3CA mutation or amplification. PF-05212384 was well tolerated with the most common AEs being mucositis (44%), nausea (42%), fatigue (28%), rash (28%), and hyperglycemia (26%). DLTs included mucositis, rash, transaminase elevation, and hyperglycemia. An MTD of 154 mg weekly has been estimated. PF-05212384 is eliminated with a half-life of approximately 16 hours, with low clearance (5–9 L/h) and relatively high volume of distribution (54–144 L). Changes in blood glucose have been observed in 13 patients, including 2 patients with Grade 3 hyperglycemia, a known effect of PI3K/Akt pathway suppression. No objective tumor response has been observed; 12 patients have achieved stable disease (SD) in excess of 16 weeks, with 9 patients on study for ≥24 weeks and one patient (salivary) on study for >46 weeks. Enrollment to MTD expansion cohorts is ongoing.

Conclusions: Weekly administration of PF-05212384 is safe and tolerable across dose levels with multiple patients deriving clinical benefit with prolonged SD. The occurrence of hyperglycemia is suggestive of target modulation. Updated data for safety, PK, PD and antitumor activity will be presented

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr A167.