The US Food and Drug Administration issued new draft guidance this summer to spell out how it plans to handle the approval process for in vitro companion diagnostic devices. The draft guidance emphasizes that in vitro companion diagnostic devices and their corresponding therapeutics should be developed and sent through the approval process at the same time. "The reason is that once the drug is approved, the companion diagnostic needs to be available, but we can't approve a diagnostic with the intended use to support a drug until the drug is approved," says Elizabeth Mansfield at FDA's Center for Devices and Radiological Health.
Mansfield says the agency has seen an uptick in the number of investigational drug packages that would need a companion diagnostic. In 2005, the agency wrote a concept paper that dealt with companion diagnostics, but for the current draft guidance, Mansfield says, "we wanted to make the regulatory policy clear and predictable."
In the draft guidance, the agency first defines what a companion diagnostic device is, saying that it "provides information that is essential for the safe and effective use of a corresponding therapeutic product." For example, a companion diagnostic would identify patients who should or should not receive certain drugs or identify the dosage of a drug that patients should receive. Then, the agency says that the companion diagnostic and therapeutic product should ideally be approved at the same time. FDA notes, however, that there may be cases where that is not feasible, such as when a potentially life-saving therapeutic may be moved quickly through the approval process to get it to patients. "The development timeline for the diagnostic and the drug could be out of sync, and we don't want to deny the availability of the drugs if it's reasonably safe without the diagnostic," Mansfield adds.
Though the draft guidance is essentially already being used, there is a 60-day comment period — which ends in the middle of this month — for the public to submit thoughts and comments for FDA to consider. "Hopefully, we won't have to make a lot of changes," Mansfield says, adding that she thinks that the draft is fairly clear. "We'd like to do it as quickly as possible. The final guidance is always the most helpful."