Immuno-oncology therapeutics embrace modulation of the immune system to recognize and target tumor cells for destruction, either by increasing the function of the immune system or preventing the evasion of tumor cells from it. The evolution of tumors to suppress the immune system, as well as maintaining a suppressive micro-environment, has hindered drug efficacy and restricted regression of tumor masses. However, once these mechanisms are clearly understood, this complexity presents many known and novel targets for drug discovery.
Translational research typically starts by screening compounds in simple cell-based assays, determining modulation of immune activity or responses. For example, changes in the number of immune cells to fight immune evasion or the amount of cytokines released by the immune cells, which raise immune reactivity therefore driving an anti-tumor response. Utilizing an internal blood donor panel, Charles River’s in vitro platform includes primary human immune cell assays that profile T cell activation, T cell mediated-cancer cell kill, and expansion of T cell populations, with the benefit of being able to return to donors on a repeating basis.
Through these assays, compounds are identified for further characterization in more complex co-culture assays, such as mixed lymphocyte reactions, T cell invasion, antibody-dependent cellular cytotoxicity and complement-dependent cytotoxicity. These multicellular in vitro assays can bridge the gap from single cellular functional screening to in vivo models by providing a predictive model to move compounds further in the pipeline.
These multi-cellular assays, like the simpler immune cell assays, are validated with standard of care molecules, including check-point inhibitors and a selection of small-molecule inhibitors of targets known to modulate immune responses, confirming Charles River’s predictive immuno-oncology platform.
Our most complex co-culture model uses 3D tumor cell spheroids and immune cell populations, in conjunction with standard-of-care compounds, to model potential high bar efficacy models as a final check before moving to in vivo models. Allied to this, ex vivo analysis of the standard-of-care therapeutics effect on activated mouse splenocytes, measured as cytokine release, and modulation of immune cell populations; as determined by flow cytometry, supports the translation of important compounds from the bench to preclinical models. A better understanding of the compound in these immune cell populations provides insight into what type of cell is being modulated and helps to guide the design of in vivo preclinical models.
Syngeneic tumor models have frequently been used to profile immune responses in tumors and Charles River has optimized and profiled existing checkpoint inhibitors to support immuno-oncology drug discovery using mouse and rat antibody variants of anti-CTLA4 and anti-PD1, to help build understanding of which model to use with novel compounds and whether they can be used in combination. To confirm the translational development of the platform, Charles River has developed and optimized humanized research models using subcutaneous implanted patient-derived xenografts (PDX) with human engraftment via CD34+ haematopoeitic stem cells in NOG mice. As with the in vitro component of the immune-oncology platform we have treated large panels of PDX tumors with check-point inhibitors as a platform for determine efficacy. Assessment of immune cell infiltration and PDL-1 expression was detected by flow cytometry (FC) and immunohistochemistry (IHC) in hematopoietic organs and tumor tissue, supporting the initial in vitro response in primary immune cells.
Charles River’s translatable immuno-oncology platform enables oncology researchers to rapidly assess the immune modulatory function of therapeutic modalities in high throughput platforms, illustrating T cell activation, increased proliferation and cytokine release. A spheroid model of T cell mediated cancer cell death is presented as an important complex cell model to support translational drug discovery, sitting alongside T cell exhaustion, T cell migration and macrophage phagocytosis helping to define diverse aspects of micro-environmental control of immune response. The translatable function of the platform is completed by our efficacy models embracing genomically defined syngeneic and patient derived models, all supported by flow cytometry enabled biomarker studies.
Martin O’Rourke has been working in oncology drug discovery for more than 10 years. His initial postdoctoral research focus was in vitro and in vivo models of angiogenesis within the drug discovery group at Queen’s University, Belfast (UK). This research led to the discovery of the endogenous protein FKBPL, ultimately identifying a derived peptide as a potent anti-angiogenic agent in prostate cancer models. Martin joined Charles River as a group leader, then became department director. Following this appointment, he took a short leave to serve as Head of Biology with Kesios Therapeutics, leading their clinical candidate back-up project, then returned to Charles River and the Integrated Drug Discovery team. Dr. O’Rourke is a member of the Irish Association of Cancer Research and American Association of Cancer Research. His research has appeared in 21 peer-reviewed papers and has yielded 6 patents.