Which Assay to Use?
Almost every new oncology drug being developed today is targeted toward a specific protein or family of proteins. Thus, companion diagnostic assays are needed to help identify those patients who will benefit from a new drug. There are a number of methods and platforms for which the companion diagnostics can be applied. Dako, an Agilent Technologies company, focuses on immunohistochemistry (IHC), fluorescent in situ hybridization (FISH), and bright-field chromogenic in situ hybridization (CISH) assays on fully automated systems.
According to Hans Christian Pedersen, principal scientist at Dako, “A companion diagnostic needs to be available wherever the drug is intended to be used. Thus, the selected technology must be adaptable into routine clinical practice and the costs secured through adequate reimbursement.”
“Additionally, a companion diagnostic test must have a reasonable turnaround time, typically within one day, to avoid delays in providing test results to the oncologists making the treatment decision. IHC and Dako’s recently introduced IQFISH technology fulfill all of these criteria and also have the advantage that most pathology laboratories are performing these tests today, and therefore have the infrastructure, know-how, and skills necessary to perform these assays.”
Pedersen adds that since most new drugs are directed at a protein, and the protein represents the functional entity in the cell, it is important to look at the protein in the context of both cellular localization (membrane/nuclear/cytoplasmic) and being able to assess protein expression levels directly in the context of the tissue. “Again, IHC allows for this type of determination and performs very well,” Pedersen notes.
For the future, Pedersen agrees that NGS and quantitative polymerase chain reaction (PCR) may be used more in the clinical setting. “We are already seeing companion diagnostic collaborations that utilize quantitative PCR technology. At the moment, these technologies represent big potential, but also big challenges.”
“With the rapid pace at which the technology is moving, today’s NGS platform may differ from tomorrow’s NGS platform. It is uncertain what effect NGS will have on the quantitative PCR-type tests being developed today. However, it is crucial for pharmaceutical companies to select a technology platform for their companion diagnostic that won’t be outdated by the time the drug is launched.”