Pionyr Immunotherapeutics has dosed the first subject in the Phase Ib expansion trial of its monoclonal antibody PY314 to treat solid tumour patients.

PY314 attaches to Triggering Receptor Expressed on Myeloid Cells 2 (TREM2) on the immunosuppressive, pro-tumour myeloid cell surface.

It can potentially reduce TREM2-expressing tumour-associated macrophages (TAMs), offering productive anti-tumour immunity. 

The Phase Ib expansion trial will analyse PY314 as monotherapy and along with pembrolizumab to treat predefined tumour types, including breast, ovarian, colorectal, lung and renal cancers.

The first subject who was dosed in the trial received PY314 as a monotherapy for advanced ovarian cancer while the combination arms of the trial commenced enrolment.

In this trial, anti-tumour activity, safety, tolerability and pharmacokinetics of PY314 will be analysed.

Furthermore, additional exploratory biomarkers, including the assessment of TREM2-expressing macrophages in tumour biopsy samples, will be evaluated.

The Phase Ib trial comes after the Phase Ia dose-escalation study that analysed the safety and tolerability of PY314 as monotherapy and with pembrolizumab for various solid tumours.

The multicentre Phase 1a trial in the US concluded subject enrolment and determined the recommended dose for the Phase Ib trial.

Pionyr Immunotherapeutics executive vice-president and chief medical officer Leonard Reyno said: “Dosing the first patient in our Phase Ib expansion study is an important milestone for the clinical development of PY314, having passed the first safety analysis and identifying a recommended dose for further evaluation.

“PY314 represents an opportunity to expand immunotherapy options for patients with advanced solid tumours, which continues to represent a major unmet need, especially among patients with checkpoint resistant tumours.”

The company signed a transformational collaboration in July 2020 through which Gilead Sciences obtained its minority interest.