Pfizer Initiates Phase 1 Trial of IDO1 Inhibitor for Brain Cancer

Pfizer Inc. has initiated a Phase 1 clinical trial for its investigational IDO1 inhibitor, PF-06840003, in patients diagnosed with malignant gliomas. The primary objectives of this study are to determine the safety, maximum tolerated dose (MTD), and recommended Phase 2 dose for the drug. The trial will also monitor early biomarkers of activity.

This study marks a milestone in the collaboration between Pfizer and iTeos Therapeutics, which began in December 2014. The partnership focuses on developing therapeutics targeting the tumor immune environment. iTeos identified and optimized PF-06840003, which was subsequently licensed to Pfizer based on promising preclinical data, including efficacy in various cancer models.

IDO1 inhibitors function by targeting indoleamine 2,3-dioxygenase (IDO1), an enzyme associated with immune suppression in many cancers. By inhibiting IDO1, these drugs aim to restore the immune system's ability to recognize and attack tumor cells. PF-06840003, a small molecule inhibitor, has demonstrated anti-tumor activity in preclinical models, particularly when combined with immune checkpoint inhibitors.

The Phase 1 trial is an open-label, multicenter study designed to establish the recommended Phase 2 dose of oral PF-06840003 administered once daily as a monotherapy. Secondary objectives include assessing the drug's safety and tolerability, pharmacokinetics, and preliminary anti-cancer activity. Exploratory objectives will involve the investigation of biomarkers.

This clinical trial progression is a significant step in Pfizer's immuno-oncology pipeline, aiming to bring new therapeutic options to patients. The results will inform the design of future clinical studies.