Merck & Co and Eli Lilly have decided to expand their existing oncology collaboration with another immunotherapy combination trial.

The study will assess the potential of Lilly's Lartruvo (olaratumab) with Merck's Keytruda (pembrolizumab) in patients with previously treated advanced or metastatic soft tissue sarcoma (STS).

Regulators on both sides of the Atlantic have recently cleared Lartruvo, in combination with doxorubicin, for the treatment of some adults with STS, a rare and notoriously difficult-to-treat cancer with few treatment options.

Larturvo is a platelet-derived growth factor receptor alpha (PDGFR-α) blocking antibody that specifically binds PDGFR-α and prevents receptor activation. The drug exhibits in vitro and in vivo anti-tumour activity against selected sarcoma cell lines and disrupted the PDGFR-α signalling pathway in in vivo tumour implant models, according to the firms.

Keytruda is a humanised monoclonal antibody that works by increasing the ability of the body's immune system to help detect and fight tumour cells, blocking the interaction between PD-1 and its ligands and thereby activating T lymphocytes.

The companies are exploring whether a combination of these two drugs and their differing modes of attack will results in a more powerful response.

"This collaborative study builds on the exciting data we have seen with olaratumab and supports our focus on investigating the potential of rational combinations to enhance efficacy and change the standards of care for people with cancer," noted Susan Mahony, senior vice president and president, Lilly Oncology.

Lilly is sponsoring the Phase I trials, with enrolment is expected to begin mid-2017. Financial details of the collaboration were not disclosed.