The topic of IHC came up recently. Specifically, why is it used so frequently for companion diagnostic development.
The discussion came up during our 2020 wrap up, looking at all active CDx or CDx-track studies NeoGenomics has worked on. Looking back through our historical trends, the bulk of CDx-track studies NeoGenomics has supported are IHC-based assays. Even when you exclude multiples of the same biomarker (and there are a lot of PDL1 and HER2 in there), IHC still comes out ahead. In all, 2020 was a record year in terms of new CDx-track studies that NeoGenomics is working on, with IHC still ahead as the most popular. People were wondering why. In the age of NGS panels, multiplex immunofluorescence, and RNAsequencing, there are many next-generation approaches to predictive biomarkers.
IHC has many virtues. I thought it worthwhile reviewing what makes IHC a good choice for CDx development:
- Turnaround time. We can turn around an IHC assay in a few days, typically much faster than PCR or NGS-based assays
- Infrastructure. IHC is a widely adopted technology, making global harmonization for clinical trials straightforward. There are several well-established manufacturers in this space that can provide global support
- Laboratory operations. IHC is amendable to running one or two samples at a time. Contrast this with molecular technologies, which often require minimum batch sizes in order to be cost-effective.
- Cost. Low cost relative to other approaches.
- Simplicity. Often, a single biomarker is sufficient. This is often the case with a therapeutic that targets a particular surface marker. IHC-based assays remain the standard approach for antibody-based drugs, antibody-drug conjugates, or CAR T-cells targeting a particular cell surface antigen
- Commercialization. The well-established IVD manufactures in the pathology space, combined with widely distributed infrastructure, make global launch and commercialization of a CDx straightforward
- Regulatory. The pathway for regulatory approval is well-established, and a broad array of predicate devices that can be used
- Reimbursement. In general, laboratories get paid for it, laboratories like to use it
There are downsides, of course. The subjective nature of pathologist evaluation, and reproducibility of complex scoring algorithms, has long been a concern with this technology. However, we see a bright future in further development of digital pathology solutions to provide truly quantitative and reproducible read-out
How long will IHC remain on top? In terms of the request that came into NeoGenomics for development or support of CDx projects, 2020 was the first year that requests for IHC was the second-most popular technology requested. NGS-based technologies were number one. So while our current portfolio is heavily IHC-focused, I foresee it sharing the stage with newer technologies.