PharmAbcine said Wednesday that the company began the administration of its VISTA-targeted immunotherapy candidate, PMC-309, in patients in Australia.

The Australian phase 1a/b trial will be conducted on 67 patients with advanced or metastatic solid tumors at four medical institutions.

According to PharmAbcine, PMC-309 is an IgG1 monoclonal antibody with a specificity to bind only VISTA on immunosuppressive cells, with excellent binding independent of varying pH conditions in the tumor microenvironment (TME). PMC-309 binds to immunosuppressive VISTA and controls its function.

The company said it has a differentiated mechanism of action, showing anticancer effects through T-cell activation and a conventional immuno-oncology mechanism. It also contributes to monocyte activation and M1 macrophage proliferation.

The clinical trial will consist of phase 1a and phase 1b.

Phase 1a will evaluate PMC-309 monotherapy in combination with Keytruda in patients with advanced or metastatic solid tumors to determine the maximum tolerated dose (MTD) and recommended preliminary phase 2 dose (RP2D). Phase 1b will evaluate the safety and tolerability of PMC-309 monotherapy and Keytruda combo therapy at the recommended preliminary phase 2 dose.

"In this study, we will confirm the human safety of both VISTA immunotherapy alone and in combination with Keytruda,” PharmAbcine CEO Yoo Jin-san said. “We will do our best to develop it as a new treatment for cancer patients."