Immunotherapy and Cancer: Harnessing the Power of Diagnostic Assays - 13

Immunotherapy and Cancer | Harnessing the Power of Diagnostic Assays
To realize the potential of immunotherapies, we need to know
how and why certain individuals respond to treatment. This
goes beyond the approach of profiling tumor mutations as is
done with targeted therapies. We need to identify the level of
tumor immunogenicity, the level of immune infiltration and
to characterize how effective the patient's immune system is
at recognizing and engaging the tumor.
CO: Why are current biomarkers, such as PD-L1

expression insufficient?

CS: This issue can be viewed at two levels-the first is a technical one. Analysis of PD-L1 expression is highly subjective, and
requires not only standardization across laboratories, but
within a laboratory. Current methods utilize different cutoff values and rely upon pathologists' training and level of
expertise.

PD-L1 IHC staining has
been adopted by clinical
laboratories to assess response
to immunotherapies, yet
is an imperfect biomarker
and requires further
standardization and
optimization.

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The second issue is that PD-L1 expression is likely to be one
dimensional. Looking at one biomarker for one drug, is not dissimilar to only using EGFR testing for non-small cell
lung cancer patients. Our understanding
of patient response to treatment is
evolving, so it becomes difficult to
"Hundreds of new
select one biomarker, or to estabimmunotherapeutic
lish a specific cut-off threshold for
agents are in
patient selection. This is particudevelopment. "
larly true when different PD-L1
antibodies are used and different
tumor types are being evaluated. Various methods are being use to gain multidimensional information about the tumor and its
microenvironment, including tumor infiltration, tumor mutation burden, gene expression, and microsatellite instability.
CO: What is the role of diagnostics in therapy today,

and why is it critical?

CS: Diagnostics need to be clinically meaningful and deployable
in medical practice. Unfortunately, a wide variety of biomarker
assays and methodologies are being used in clinical trials. The
implications of not having standardization will become problematic as different methodologies are likely to generate conflicting results.
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