Developing molecular diagnostic tests in tandem with targeted therapeutics
The anticipated success of personalized medicine will in part depend on a molecular-targeted drug having a linked, or “companion,” diagnostic test designed to determine precisely whether a patient will benefit from the specific treatment, or to monitor therapy in "real time" as a way to determine ongoing efficacy.
Theranostics, or Rx/Dx, refers to the development of molecular diagnostic tests and targeted therapeutics in an interdependent, collaborative manner with the goals of individualizing treatment by targeting therapy to an individual's’ specific disease subtype and genetic profile. This strategy will enable optimization of drug efficacy and safety and will assist in streamlining the drug development process.
The companion diagnostic is a tool that may enable health care providers to determine the subtype of the disease, its progression, and the characteristics of a patient. These advanced capabilities are expected to enable physicians to make better-informed decisions on timing, quantity, type of drugs, and choice of treatment procedure, as well as to evaluate response to treatment, all based on the relevant information provided by the companion diagnostic tests.
The combination of Genentech’s Herceptin® with DakoCytomation’s HercepTest® is the best-known example of a commercialized theranostic. Herceptin® targets the HER2 protein, which is overexpressed in 25% to 30% of breast cancers. Physicians use the HercepTest® to detect susceptible tumors, which enables targeting of the treatment to patients that are likely to benefit from the drug. The FDA approved Herceptin® as a biological product in September 1998; at the same time, the FDA’s Center for Devices and Radiological Health reviewed and approved DakoCytomation’s HercepTest® diagnostic kit for HER2 expression. The drug and the diagnostic came to market at the same time, with the drug’s labeling specifying the requisite diagnostic test.
This integration of drug selection to target a cancer on a personal basis as a direct result of the information derived from a diagnostic test is among the foremost targeted therapy strategies in oncology today, and many experts view Rx/Dx co-development as the ultimate goal of personalized medicine.