A Closer Look at Companion Diagnostics Strategies

I have written a number of previous notes about companion diagnostics. Briefly stated, this is a strategy pursued by some IVD companies, Roche Diagnostics in particular, whereby the company develops a gatekeeper biomarker assay. This is a lab test that serves to qualify a patient for treatment with a particular drug. The most common example of such a test is the HER-2/neu assay that is required prior to treatment with Herceptin. Herceptin is used for adjuvant treatment of HER2-over-expressing node-negative (ER/PR-negative or with one high-risk feature) or node-positive breast cancer following multi-modality anthracycline-based chemotherapy. To restate the obvious, a companion diagnostics strategy can be very successful when linked to a popular drug but obviously less attractive if the associated drug proves not to be well accepted. Another interesting scenario occurs when a lab test can be used to provide evidence that a particular drug is not therapeutically effective -- essentially an anti-companion test.

Given this background, I pay attention when an executive of a national reference lab opines about the interplay between drugs and lab tests. Below is an excerpt from such an article (see: LabCorp CEO: Tests Could Slice Market for Cancer Drugs),an interview of David King of LabCorp (boldface emphasis mine):

Some drug companies are betting on the future of targeted medicine, hoping to improve outcomes by using high-tech tests to figure out which patients could benefit from a given drug. But what if a diagnostic test comes along and shows that a drug that’s already been approved for a disease may not work well for some patients? The pharmaceutical companies won’t always welcome this,” David King, CEO of the diagnostics shop LabCorp.....But with specialty drugs getting more expensive, and testing getting more sophisticated, such tests are likely to emerge soon whether drug makers like it or not. Genentech’s Avastin, which was recently approved for breast cancer without clear evidence that it extends the lives of patients with the disease, would be one potential candidate for such a test, King said. A new diagnostic test could wind up shrinking the market for a drug by ruling out some patients....Abbott [has announced that] its diagnostics unit has cut a deal with Genentech, OSI and Roche to develop a genetic test to assess the potential benefit of Tarceva, a drug for cancer of the lung and pancreas that is co-marketed by the companies.

I have the distinct impression that the term companion diagnostics may have outlived its usefulness -- but I am equally sure that it will not go away. My major problem with it is that the word companion sounds too warm and fuzzy. My first thought was that we should now refer to such testing as surveillance or sentinel lab testing. The basic idea here is that the lab test is used to determine efficacy or, contrariwise, the lack of efficacy or even the potential harmful side effects of treatment with the drug. I must also confess to a slight anxiety about too cozy a relationship between the developers of such surveillance/sentinel lab tests and the pharmaceutical companies that develop and manufacture a particular drug. Nevertheless and on balance, I think that such relationships will probably work for the benefit of the patients by determining whether they are candidates for newly developed drugs.

Comments

[Dr Radcliffe herceptin her2]

The companion techique should be well researched and studied before allowing
with Herceptin

[Paul Epner]

I read with interest your views on the use of the term "companion diagnostics." I am also concerned that it is too imprecise, however I would suggest that we consider other accepted terms as a basis for new jargon. In this case, I refer to therapeutic drug monitoring (TDM) which leads me to think that the appropriate term here would be "therapeutic drug assessment (TDA)" or slightly more distant, "drug effectiveness assessment (DEA)", the latter having a possibly confusing acronym. I am less worried about the industry relationships. Failure to provide valid TDA's increases clinical and economic risks for healthcare consumers. History has shown that development of TDM's through industry relationships has been beneficial.