OS Therapies has dosed the first subject in the pivotal Phase IIb clinical trial of its lead therapy, OST-HER2 (OST31-164), to treat patients with recurred, resected osteosarcoma.

An Lm vector-based off-the-shelf immunotherapy, OST-HER2 can potentially prevent metastasis, boost overall survival and delay recurrence.

It acts on osteosarcoma in kids and young adults, as well as other solid tumour types.

The nationwide open-label Phase IIb trial plans to recruit a total of 39 to 45 osteosarcoma patients who have had cancer that metastasised to the lungs and was surgically removed.

The company is carrying out the trial across 20 institutions affiliated with Children’s Oncology Group (COG), starting at Seattle Children’s Hospital in the US.

OS Therapies CMO/CSO Dr Robert Petit said: “The OST-HER2 treatment has been highly successful in multiple trials in canine osteosarcoma, demonstrating three times improvement in overall survival and disease progression, with significant similarities between human and canine osteosarcoma.

“We hope to demonstrate that it works as well, or even better, in kids.”

A solid tumour of the bone, osteosarcoma mostly affects adolescents, as well as young adults with surgical procedures and chemotherapy being the standard therapies.

So far, the OST-HER2 Lm vector platform technology was used in more than 450 cancer patients in ongoing and concluded trials.

The Food and Drug Administration and European Medicines Agency granted Fast-Track and Orphan designations to the immunotherapy while OS Therapies is currently pursuing Rare Disease Designation for OST-HER2.

On obtaining favourable results from the Phase IIb trial, the company intends to apply for a breakthrough designation for the treatment.

Early findings from a concluded Phase III trial of OST-HER in canines showed a clear distinction between treated and untreated canine subjects in overall survival and disease progression.