Using High Content Imaging for Biomarker Discovery to Support Precision Oncology
Gavin J. Gordon, MBA, PhD, Vice President of Commercial Operations at Fluidigm Corporation, South San Francisco, CA
Q: Huge new advances in technology continue to illuminate the research and translational space. How do you think your new product the Hyperion Imaging System is likely to influence precision medicine testing?
A: The Hyperion™ Imaging System* is part of a group of emerging life sciences research platforms that enable highly multiplexed immunohistochemistry (IHC). High-parameter IHC is a nascent application with the potential to drive significant advancements in precision medicine, particularly in oncology, and positively impact patient care.
The rationale for the potential impact of high-parameter IHC on precision medicine, and by extension the Hyperion Imaging System, is based on two recent observations in translational medicine.
First of all, biomarker discovery efforts in translational medicine and pharma R&D are increasingly reliant on an antibody-mediated approach for protein detection in fixed tissue sections to complement existing efforts to interrogate the genome for signatures that are predictive of drug response or that correlate with prognosis. The development of immunotherapies, primarily in oncology, is a significant driver of this trend. As a result, monitoring and characterizing the immune repertoire is an essential component of any successful proteomics-based biomarker discovery strategy for immunotherapy.
Secondly, there is significant diversity inherent in the immune repertoire that, when combined with a range of tissue-specific cellular phenotypes, requires biomarker studies that can provide “single-cell resolution” and measure a relatively large number of both cell surface and intracellular protein markers.
Both of these observations are particularly relevant for developing oncology therapy, and oncology is the most exciting area of precision medicine. Thus, a high-parameter IHC approach is particularly well-positioned to contribute to a paradigm shift in precision oncology research. However, there are relatively few options for platforms capable of meeting the requirements described above, none with simplified workflows. This has necessarily limited the scope and number of these types of studies at the current time.
Highlighting the relevance of this approach, and the pitfalls that can occur by minimizing the importance of the biomarker to the success of the drug, are recent immunology clinical trials from both BMS and Merck targeting the programmed death ligand 1 (PD-L1) pathway. Recently the BMS immunotherapy Opdivo® missed its primary endpoint in the Phase III CheckMate -026 trial, namely progression-free survival in treatment-naïve NSCLC patients whose tumors expressed PD-L1 at ≥5%. While BMS’s strategy was to include a broad subset of patients in that trial, Merck’s KEYTRUDA® clinical trial focused on a much narrower target group with higher levels of the PD-L1 biomarker. Data from the KEYNOTE-024 study showed a progression-free survival benefit in patients with tumors expressing PD-L1 on at least 50 percent of cells taking Merck’s drug. But even in the case of KEYTRUDA, not every PD-L1 positive tumor responds to the drug, and there are also responders among those who fail to meet the PD-L1 cutoff.
Clearly, single-marker IHC is insufficient to stratify cancer patients for many types of immunotherapy and predict clinical outcome, thereby justifying a higher-parameter approach to biomarker discovery for this application.
This is a problem that traditional IHC cannot easily solve, if at all, since these platforms are not capable of multiplexing at a high enough level due to inherent limitations of the antibody detection technology. Current state of the art for “high-parameter” IHC using an immunofluorescence (IF) approach enables simultaneous detection of up to 4 markers on a single tissue section, clearly not enough for biomarker discovery efforts in immuno-oncology. Specialized IF platforms can push this to 7-8 markers, but these methods are cumbersome, complex, and require significant informatics to spectrally “unmix” the signal from overlapping fluorescent emission spectrums. And it’s a lot of effort to go through since the additional data from even 7-8 markers cannot comprehensively characterize the tumor microenvironment. General consensus is that ~15-25 markers will be required to conduct the next generation of IHC-based biomarker discovery studies in immuno-oncology.
The Hyperion Imaging System, developed by Fluidigm, has overcome this insufficiency through the development of a mass cytometry (CyTOF®) platform capable of simultaneously measuring the relative expression levels of 4 to 37 proteins at single-cell resolution in fixed tissue sections [including formalin-fixed, paraffin-embedded (FFPE)] and cytological preparations. This innovative platform uses an antibody-mediated approach and metal isotopes of defined mass to enable highly multiplexed and high-throughput studies of protein expression in individual cells in situ. As a result, the Hyperion Imaging System greatly expands and builds on the inherent value of relatively low-parameter IHC (for cells on fixed tissue sections) and has the added benefit of preserving precious patient samples since data for all markers can be obtained from a single tissue section at the same time.
While it remains to be seen exactly what level of impact the Hyperion Imaging System platform will have in driving significant advancements in precision oncology, the same can be said about all other similar IHC platforms and indeed the field of high-parameter IHC in general. Time will tell as more and more studies emerge showing biological relevance and attesting to the clinical utility of such an approach.
*The Hyperion Imaging System is available only from Fluidigm Corporation. More information can be obtained at fluidigm.com/hyperion.
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