Laboratory tests to understand why some patients with mesothelioma respond better to a combination of chemotherapy and immunotherapy

Nowak AKLesterhuis WJ, Lassmann T, Cook AM, Yip S, McDonnell AM. (2019-2020)

Funding: Cancer Council of Western Australia

Synopsis (lay): Immunotherapies including checkpoint blockade have revolutionised the outlook of some cancers. Combinations of chemotherapy and checkpoint blockade are poised to be the next cancer breakthrough. However, understanding why some people respond and others do not is critical – both to target treatment to the right people, and to fine-tune treatment and enhance outcomes in those who may otherwise not respond. This study harnesses a potentially ground-breaking positive clinical trial of chemo-immunotherapy in people with mesothelioma, and uses blood specimens that have already been collected from trial participants before and during their treatment for cutting edge scientific analyses of the patient’s immune cells. Understanding the biology of response and non-response will help us understand why a tumour has or has not responded, enabling us to develop improved treatments. We may also be able to better predict in advance who will benefit from this treatment.

Synopsis (scientific): We have an unparalleled opportunity to conduct translational biomarker studies to complement and explore the exciting clinical results from our recently completed phase II clinical trial of durvalumab in combination with cisplatin and pemetrexed chemotherapy in mesothelioma (the DREAM trial). The outstanding preliminary results have triggered development of a randomised phase III clinical trial comparing cisplatin and pemetrexed in combination with either durvalumab or placebo. However, given the financial costs, potential severe side effects and differential responses, the identification of predictive biomarkers of response is crucial. In addition, identifying on-treatment correlates with response could result in the development of additional treatments that can increase the response rate. We therefore aim to perform critical correlative biomarker studies, for which we already have collected and stored all samples, which will guide biomarker studies for the planned future phase III study.

One facet of this biomarker analysis is to identify cell subset changes using flow cytometry on PBMCs. We will also examine a range of activation and proliferation markers on cell subsets of interest. Cryopreserved PBMC will be stained with panels of fluorescently conjugated antibodies, including: CD3, CD4, CD8a, CD11c, CD14, CD16, CD19, CD20, CD27, CD38, CD45, CD45RA, CD61, CD66, CD123, CD235a/b, HLA-DR, pSTAT1, pSTAT3, pSTAT6, ICOS, PD-L1, PD-L2, Lag-3, PD-1, together with a viability dye excluding dead cells. Data will be analysed using the viSNE high-dimensional data visualisation tool and the SPADE and CITRUS unsupervised clustering analysis algorithms in addition to manual gating using FlowJo (CID). This will allow us to validate differences in phenotypic and functional markers (eg. STAT phosphorylation, ICOS or PD-L1/2 expression) across cell subsets and between responders and non-responders as identified from RNAseq data. Primary outcome measures for statistical testing: 6 month PFS (continuous) and responders vs. non-responders (discrete). Data will be hypothesis-generating and exploratory, but able to be confirmed in the event of a subsequent randomised trial.

NCARD Research Team