Gosselies, Belgium – September 28, 2016 – iTeos Therapeutics SA, a biotechnology company working with Pfizer Inc. (NYSE: PFE) to develop therapeutics targeting the tumor immune environment, today announced dosing of the first patient in a Phase 1 dose-escalation study of PF-06840003 (EOS200271) being conducted by Pfizer in patients with brain cancer (malignant gliomas). The objectives of the study are to determine the safety, maximum tolerated dose (MTD) and recommended Phase 2 dose while monitoring early biomarkers of activity. This achievement will trigger a milestone payment for iTeos by Pfizer.

"The start of this Phase 1 trial shows good progress in our relationship with Pfizer," said Michel Detheux, chief executive officer of iTeos. "PF-06840003 (EOS200271) was identified and optimized by iTeos in 15 months. It was licensed to Pfizer with an encouraging preclinical data package, including evaluation of pharmacodynamics and efficacy in combination with different treatments in preclinical models, as well as the profiling of IDO1 expression in more than 1200 clinical human samples."

“This milestone in our collaboration with iTeos marks an important step for Pfizer as we continue to build a robust immuno-oncology pipeline that will help us bring potential new therapies to patients in need,” said Robert Abraham, Ph.D., Senior Vice President and Head of Pfizer’s Oncology Research & Development Group, Pfizer. “We believe that PF-06840003 may have the potential to enhance anti-tumor immune responses in certain settings, and we look forward to the results of this Phase 1 trial.”

iTeos and Pfizer entered into a license and collaboration agreement in December 2014.

About the Phase 1 Trial
This Phase 1, open-label, multicenter study (NCT02764151) is designed to determine the recommended Phase 2 dose of oral PF-06840003 administered as a single agent once-daily in patients with malignant gliomas. The secondary objectives of the study are to assess PF-06840003's safety and tolerability, pharmacokinetics, and preliminary anti-cancer activity, with an exploratory objective to explore biomarkers of activity.

About PF-06840003 ( EOS200271)
PF-06840003 is a synthetic, small molecule inhibitor of indoleamine 2,3- dioxygenase (IDO1), an immunosuppressive enzyme that is induced in a wide range of cancers. Inhibiting IDO1 helps restore immune surveillance of tumors, which could potentially lead to their elimination.

PF-06840003 has demonstrated anti-tumor activity in multiple preclinical tumor models when administered in combination with immune checkpoint inhibitors. PF06840003 was exclusively licensed from iTeos to Pfizer in December 2014.

About iTeos Therapeutics SA
Based in Gosselies, Belgium, iTeos, a spin-off of Ludwig Cancer Research (LICR) and de Duve Institute (UCL), has built a discovery platform to identify therapeutics targeting the immune tumor micro-environment and is now positioned to help deliver the next generation of cancer immunotherapies. iTeos combines expertise in tumor immunology with drug discovery of small molecules and biologics. The company entered into a strategic collaboration with Pfizer in December 2014. iTeos is developing partnerships with top-tier academic and industrial partners to develop new programs. iTeos is supported by the Walloon Region of Belgium and the FEDER (European Fund for Economic and Regional Development).