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On Friday, the Food and Drug Administration approved the first drug in a new class of drugs to treat infections caused by a biological weapon. The drug is called “antiviral pills,” the first by the name of CVC-123A. (An example of a viral infection is “rabies” or “viruslla.”) CVC-123A is in the same class of drugs as Lovaza, the most popular of the previous (and other) antiviral pills.
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In a news release, FDA Commissioner Scott Gottlieb noted that the nasal spray-form of CVC-123A “may offer patients and clinicians an alternative treatment option for people who are sick from exposure to certain strains of a biological weapon.” On Tuesday, FDA staff suggested the agency could potentially approve an oral form of the drug as well. The oral version would be attractive to hospitals since there are no hospital time constraints for antiviral medication, and topical medications are costlier than oral.
There are still reasons to be cautious, however. In August 2016, before receiving FDA approval, the drug’s sponsor, led by Hoffman-La Roche, also submitted a safety information letter to address concerns about acute inflammatory vasculitis, or the development of inflammation associated with acute effects from a biological agent.
The safety letter did not suggest that the treatment caused the swelling that the FDA described, or mention that the patient was given antiviral drugs in the course of a bioagent exposure. The letter describes a patient who had been given courses of Conatumumab (known in the news release as CVC-106), which may or may not have been an antiviral medicine, before the study that created the new class of drugs.
In its letter, FDA staff notes a number of examples from the study, including the patient’s history of rhinitis, or “runny nose.” But there are also one-off events that would not be expected to occur in the cohort.
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The most striking example is a single patient that experienced severe vasculitis (inflammation of the blood vessels) in both arms and both legs after a single 10-minute visit to a variety of medical facilities, including a physical therapy clinic, an infectious disease office, an acute care hospital, and a gastroenterology clinic. The patient had no history of the allergy-inducible neuraminidase antibody that the FDA typically prescribes for these acute effects.
Given the lack of an allergy and the previous two years’ history of use of a flu vaccine, an antibiotic, a nasopharyngeal flu shot, and a flu nasal spray, it is unlikely that the patient received CVC-106, not even one of the varicella vaccines typically given as part of the varicella antiviral defense. It is possible that this patient received all of the subjects’ other immunization or other pre-infection steps (such as HIV vaccinations) to promote blood-borne pathogen immunity. That this individual developed such a serious complication immediately after gaining immune-based immunity is, unfortunately, predictable for some patients who receive long-term immunization.
The full study design and papers describe more than 70.5 million visits from Americans to healthcare facilities between 2007 and 2016. This massive sample covers acute and chronic or residual exposure to a range of biological agents and infections, including hemorrhagic fevers (zoonotic diseases).
All of this points to an opportunity to determine if CVC-123A is truly effective and safe in the interim. It is unknown how long the company will have to address the issues raised in the letter, and although the FDA could revoke the drug’s approval if it still has safety and efficacy issues to resolve, there is a high probability it would grant future approval, particularly in the current highly uncertain regulatory environment.