Eli Lilly's (NYSE:LLY) COVID-19 roller-coaster ride took a turn for the worse on Wednesday morning. According to Reuters, the FDA found quality-control issues last year at a site currently being used to manufacture LY-CoV555, a monoclonal antibody that attaches itself to the coronavirus responsible for COVID-19 before it can enter host cells and turn them into virus-replicating factories.

Following an inspection last November, the FDA found data regarding manufacturing processes that had been deleted without an appropriate audit from the company's quality-control unit. While these recently highlighted issues don't concern LY-CoV555 directly, they did result in an "Official Action Indicated" notice from the FDA that hasn't yet been resolved. As such, they could lead to a delay in LY-CoV555 receiving emergency use authorization because it was manufactured on the same site.

Person working in a laboratory.

Image source: Getty Images.

On Tuesday, the National Institutes of Health (NIH) pumped the brakes on a clinical trial testing LY-CoV555 in combination with Gilead Sciences' (NASDAQ:GILD) antiviral drug remdesivir due to potential safety concerns. The study randomized patients to receive remdesivir plus either LY-CoV555 or a placebo. It's unclear at this point which medicine being tested was responsible -- or if either of them were.

The NIH study, which began on Aug. 4, is expected to enroll around 10,000 hospitalized COVID-19 patients through 51 locations. With such a large population of hospitalized patients, there's a good chance the NIH's decision to pause the study wasn't related to an unresolved issue regarding a different drug at LY-CoV555's manufacturing site.

On Oct. 7, Eli Lilly sent a request to the FDA for emergency use authorization for LY-CoV555 based on some compelling clinical trial results that suggest the benefits it provides outweigh any apparent risks. 

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