This story has been updated after the FDA clarified that the CDC's monkeypox test should be used only for diagnostic purposes and not for validating other tests.
NEW YORK — US Food and Drug Administration officials said Wednesday that over-the-counter molecular assays could bridge gaps in monkeypox testing, as agency officials also continued work on creating guidance specific to antigen tests for the disease.
In a virtual townhall held with industry stakeholders including diagnostics developers, FDA officials said makers of all types of monkeypox assays can get into a fast lane for Emergency Use Authorization reviews if they signal to the agency by Oct. 13 that they are working on monkeypox tests.
Monkeypox emerged in the US in May, and the US declared a public health emergency Aug. 4, right as new infection numbers reached past an average of 400 a day. Daily confirmed cases peaked in the mid-400s that month and since have declined to an average of fewer than 200 a day, according to the US Centers for Disease Control and Prevention.
The US Department of Health and Human Services started sending monkeypox tests to five commercial laboratories in June, and Quest Diagnostics secured the first EUA for a monkeypox test on Sept. 7. Quest has said its qualitative test targets two sequences of monkeypox and non-variola orthopoxvirus DNA.
FDA officials used Wednesday's call to answer assay developers' questions on the process of validating tests and gaining authorizations. They also said that to manage assay reagent supplies, the CDC has said its test should be reserved for diagnosis and not used to validate other tests.
In response to questions about how to evaluate assay performance, FDA officials said test developers have only one comparator test available today: the CDC's FDA-cleared non-variola orthopoxvirus assay, which is a real-time PCR test run at the CDC's Laboratory Response Network partner labs and five other reference laboratories. Developers may be able to obtain residual sample materials from the laboratories running the CDC's assay, and more comparators will become available as agency officials authorize more tests that are validated with patient samples, FDA officials said.
Timothy Stenzel, director of the Office of In Vitro Diagnostics within the FDA's Office of Product Evaluation and Quality, also said during the call it remains unclear whether rapid antigen tests are sensitive enough to detect monkeypox infections. Stenzel noted that the FDA has granted authorization for three over-the-counter molecular tests for COVID-19, and, while those tests are more expensive than home-use antigen tests, he said that similar tests for monkeypox may fill an unmet need and "bridge the gap between high-sensitivity molecular tests and lower-cost rapid antigen tests."
FDA officials are still developing a template for rapid antigen test development. They said in a prior town hall meeting Sept. 14 that firms with access to labs that are deemed biosafety level 3, or BSL3 labs, can use cultured virus and cloned expressed protein to begin work on those products.
BSL3 labs can study microbes that can cause serious or deadly diseases by being inhaled.
During both meetings, FDA officials also recommended that rapid antigen test developers contact the National Institutes of Health, which announced this month plans to accelerate validation, regulatory authorization, and commercialization of point-of-care and home-based monkeypox virus tests through the Rapid Acceleration of Diagnostics Initiative's Independent Test Assessment Program. The program began accepting applications Sept. 7.