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# iTeos Regains Rights from Pfizer for Oncology Therapy
- URL: https://www.fdaweb.com/iteos-regains-rights-from-pfizer-for-oncology-therapy/
- Published: 2018-01-04T12:00:00.000Z
- Updated: 2026-09-14T23:10:57.000Z
- Author: David McFarland
- Tags: Drugs, #legacy-id-D5140421

iTeos Therapeutics, a biotech firm developing cancer immunotherapies, has regained exclusive worldwide rights from Pfizer to develop EOS200271, a highly selective, clinical-stage indoleamine 2,3-dioxygenase (IDO1) inhibitor. A recent Phase 1 study by Pfizer did not demonstrate the therapy’s efficacy as a single agent in patients with malignant gliomas. “Interim data from 17 patients confirmed the safety and brain penetration of EOS200271 at doses ranging up to 500 mg BID, the maximum dose tested by Pfizer in the study,” iTeos says. The company is currently reviewing the full data set and plans to continue the therapy’s development in oncology indications.

EOS200271 is a synthetic, small molecule inhibitor of IDO1, an immunosuppressive enzyme that is induced in a wide range of cancers. “Inhibiting IDO1 in the tumor micro-environment suppresses a powerful immunosuppressive mechanism that is predicted to promote immune-mediated tumor elimination,” iTeos says. It was originally licensed from iTeos to Pfizer 12/2014.