OSE-279 is a high affinity humanized anti-PD1 monoclonal antibody blocking both PD-L1 and PD-L2, the ligands of PD1 overexpressed by tumor cells and tumor microenvironment. Overexpression of PD-L1 and PD-L2 on tumor cells and other cell types of the tumor microenvironment is a mechanism of tumor immune escape.

Given the advantages of owning a proprietary and protected high affinity anti-PD1 antagonist antibody, OSE Immunotherapeutics has developed a global intellectual property strategy protecting OSE-279 until at least 2039. This has been achieved through recent grants of patents in the U.S., various European countries, China, Japan, Korea, Australia, and Mexico to date. These patents protect the original antibody sequences of OSE-279 associated with its innovative biological and manufacturing properties.


OSE-279 is being evaluated in a Phase 1/2 clinical trial in patients with advanced solid tumors.

This first-in-human open label Phase 1/2 dose escalation and expansion study aims to determine the Maximum Tolerated Dose and/or the recommended Phase 2 dose of OSE-279 as a monotherapy in advanced solid tumors. Secondary objectives include assessment of OSE-279’s antitumor activity, evaluation of the safety profile, pharmacokinetic and receptor occupancy or pharmacodynamic profile (NCT05751798).

In February 2024, OSE Immunotherapeutics presented an update on the positive data of this Phase 1/2 clinical trial at the the 2024 ESMO Targeted Anticancer Therapies Congress (ESMO TAT).

The updated data show a good pharmacokinetic/pharmacodynamic (PK/PD) and manageable safety profile in line with previous anti-PD1 development and with a high signal of efficacy in the first 20 patients representing 13 different tumor types. Four confirmed ongoing partial responses (PR) with 600 mg every six weeks (q6w), with a response rate of 36%, were reported in patients with anal squamous cell carcinoma, undifferentiated pleomorphic sarcoma, oncocytic thyroid cancer, and alveolar soft part sarcoma. One still ongoing confirmed PR (81% reduction of target lesions) has been observed in a patient with hepatocellular carcinoma after one single dose of OSE-279 300 mg. Five stable diseases (SD) were reported at multiple dose levels. Treatment is ongoing in seven patients. Pharmacokinetic (PK) showed dose-proportionality and favorable exposure. Receptor occupancy (RO) was maintained. At 600 mg q6w, no dose-limiting toxicities (DLTs) were reported in 10 patients. Further to the recommendation of a Phase 2 dose (RP2D) of 300 mg q3w, the dose of 600 mg q6w has been selected as the second RP2D.

To receive OSE Immunotherapeutics’ latest news