Press Release Details

Gosselies, Belgium– April 12, 2018 –iTeos Therapeutics SA, a biotechnology company developing novel cancer immunotherapies, today announced that it will present data for its A_2Aantagonist and anti-TIGIT antibody programs in two abstracts at the upcoming American Association for Cancer Research (AACR) Annual Meeting, taking place from April 14-18, 2018 in Chicago, IL.

“We continue to make good progress advancing our best-in-class A_2A receptor antagonist and our promising anti-TIGIT antibody toward the clinic and are delighted to present this data at AACR,” said Michel Detheux, Ph.D., Chief Executive Officer of iTeos.“After the advancement of the A2Areceptor antagonist program into the clinic in 2018, the anti-TIGIT antibody will follow in 2019, fortifying our position as a leading player in the immunotherapy field.”

Adenosine A_2AReceptor Inhibitor (EOS100850): Best-in-class A_2Areceptor antagonistprogram currently being evaluated for safety and efficacy in preclinical models with a Phase I trial expected to begin in 2018.

Presentation Title: EOS100850, an insurmountable and non-brain penetrant A_2Areceptor antagonist, inhibits adenosine-mediated T cell suppression, demonstrates anti-tumor activity and exhibits best-in class characteristics

Session Title:Late-Breaking Research: Immunology 2

Session Date and Time:Tuesday, April 17, 2018 from 1:00 PM - 5:00 PM CT
Session Location: Poster Section 44

Human Anti-TIGIT Antibody (EOS884448): Antagonist antibody against human TIGIT that demonstrates a classical human IgG pharmacokinetics profile. It is currently being evaluated for safety and efficacy in preclinical models with a Phase I trial expected to begin in 2019.

Presentation Title: A TIGIT antagonist antibody EOS884448 shows dual mechanism of action by restoration of T cell effector functions and preferential depletion of Treg

Session Title:Late-Breaking Research: Immunology 1

Session Date and Time:Monday, April 16, 2018 from 8:00 AM - 12:00 PM CT
Session Location:Poster Section 45

About iTeos’ Adenosine A_2AReceptor Inhibitor (EOS100850)

The adenosine A_2Areceptor is the main adenosine receptor expressed on immune cells, which promotes immune suppression, leading to tumor evasion. iTeos’ best-in-class A_2Areceptor antagonist, EOS100850, restores T-cell activation inhibited by adenosine. EOS100850 promotes anti-tumor efficacy in mouse tumor models in combination with several immune-checkpoint inhibitors, retains high potency in the presence of elevated intra-tumoral adenosine concentrations, and is non-brain penetrant. EOS100850 is currently being evaluated for safety and efficacy in preclinical models.

About iTeos’ Human Anti-TIGIT Antibody (EOS884448)

Tigit is an immunosuppressive receptor expressed on lymphoid cell populations. TIGIT expression increases in cancer patients and marks exhausted T cells. EOS884448 is an antagonist antibody against human TIGIT. Preclinical studies show its potency to restore T cell function and to preferentially deplete Treg cells in cancer patient material. ADCC/ADCP-enabling isotypes of a-TIGIT surrogate Ab show potent monotherapy efficacy in murine tumor models that correlates to increased T cell activation and reduced Treg infiltration of tumors. EOS884448 demonstrates classical human IgG pharmacokinetics profile and a good developability profile. EOS884448 is currently being evaluated for safety and efficacy in preclinical models.

About iTeos Therapeutics

iTeos Therapeutics is a privately-held, clinical-stage biopharmaceutical company dedicated to extending and improving the lives of cancer patients by designing and developing next generation immunotherapies. The Company is advancing EOS100850, an insurmountable and non-brain penetrant adenosine A_2A receptor antagonist, into a Phase I trial in the second half of 2018. A second program for its human ADCC-enabling anti-TIGIT antibody (EOS884448) is expected to enter the clinic in 2019. The company is currently also evaluating its third program, EOS200271, a clinical-stage potent and selective IDO1 inhibitor. Based in Gosselies, Belgium, iTeos Therapeutics was founded out of the Ludwig Institute for Cancer Research (LICR) and the de Duve Institute in 2011, with funds from the LICR, the Walloon Region of Belgium and the European Fund for Economic and Regional Development (FEDER). For more information, please visit www.iteostherapeutics.com.

For further information, please contact:

Michel Detheux, CEO

iTeos Therapeutics

info@iteostherapeutics.com

Amber Fennell, Mathew Neal, Sukaina Virji, Hendrik Thys

Consilium Strategic Communications

+44 203 709 5700

iteos@consilium-comms.com

Sarah McCabe

Stern Investor Relations, Inc.

+ 1 212 362 1200

sarah@sternir.com