OSE Immunotherapeutics SA presented an update on the positive results of OSE-279 in the Phase 1/2 clinical evaluation in advanced solid tumors at the 2024 ESMO Targeted Anticancer Therapies Congress [1] (ESMO TAT) held in Paris, France (February 26 ? 28, Abstract #368; FPN 30P). The ESMO-TAT communication reported on the positive results from the Phase 1/2 clinical trial (NCT05751798 [2]) evaluating OSE-279 monotherapy in patients with advanced solid tumors, with no therapeutic option available.

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.

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 and myeloid cells in the tumor microenvironment is a mechanism of tumor immune escape. The first-in-human open label Phase 1/2 dose escalation and expansion study, initiated in December 2022, aims to determine the Maximum Tolerated Dose (MTD) and/or the RP2D of OSE-279 as a monotherapy in advanced solid tumors with two possible administration regimens.

Secondary objectives include assessment of OSE-279?s antitumor activity, evaluation of the safety profile, pharmacokinetic and receptor occupancy or pharmacodynamic profile.