Building a new class of immunotherapy The journey from a VIB discovery to a clinical-stage program at Mestag Therapeutics Few discoveries make the journey from a biological observation in the lab to a therapy tested in patients. The collaboration between the Bergers lab at VIB-KU Leuven, VIB Discovery Sciences and Mestag Therapeutics is one such example. More than a decade ago, Prof. Gabriele Bergers and her team at the VIB-KU Leuven Center for Cancer Biology set out to better understand how blood vessels and immune cells interact inside tumors. What began as a fundamental question in tumor biology led to the discovery of a mechanism that could help overcome one of the biggest challenges in cancer immunotherapy: how to bring effective immune responses into tumors that largely remain invisible to the immune system. Today, that discovery has evolved into MST-0312, a bispecific antibody being developed by UK-based biotech company Mestag Therapeutics. In May 2026, the program reached a major milestone when the first patient was dosed in the Phase I STARLYS clinical trial, evaluating its potential as a novel therapeutic strategy for patients with advanced solid tumors. Discovering a new route into the tumor Not all tumors are equally visible to the immune system. Some contain large numbers of immune cells and respond relatively well to immunotherapies. Others, often referred to as 'cold' tumors, contain few immune cells and are much harder to treat. Understanding this difference became a central focus of Bergers' research. "We've been studying the interaction between blood vessels and immune cells in tumors for many years," says Bergers. "A few years ago, we found that we could therapeutically change tumor blood vessels from being a barrier with immunosuppressive features into a vascular structure that actively promotes the entry of immune cells into tumors." The breakthrough emerged while studying tumors treated with a combination of anti-angiogenic therapy and immune...