The FDA granted donanemab a breakthrough therapy designation, meant to expedite the development and review of medicines for serious or life-threatening conditions.
The source, who spoke on condition of anonymity, said the findings involved the production of drugs including Lilly's COVID-19 therapy, whose use in the United States is funded by the federal government.
Separately, FDA inspectors in March identified numerous manufacturing lapses at a second Lilly facility in Indianapolis that bottles the COVID-19 therapy and other drugs.
With 3.45 million active cases, India recorded 357,229 new infections over the last 24 hours, while deaths rose 3,449 for a toll of 222,408, health ministry data showed. Experts say actual numbers could be five to 10 times higher, however.
The drugmaker said it will work urgently to increase the supply multifold over the coming weeks.
Nearly 30% of the US population has been vaccinated against COVID-19, hitting demand for antibody drugs that already suffered from slower-than-expected uptake by hospitals.
Sales of other high-profile Lilly drugs also fell short of Wall Street expectations and its shares fell 3% to $181.64 in morning trading.
The request made to the US Food and Drug Administration is not due to any new safety issues, but in response to the new variants in the country that could be resistant to bamlanivimab when used alone, the drugmaker said in a statement.
Hospitals with bamlanivimab supply should now order etesevimab to pair with it, Lilly said.
Lilly and the US government have agreed to modify their existing agreement to enable the supply of etesevimab to complement doses of bamlanivimab the US government had already purchased, the drugmaker said.
The earlier supply agreement for bamlanivimab has been terminated and cancels the remaining 350,856 doses of bamlanivimab that were scheduled to be delivered by the end of March 2021.
The drug, donanemab, also showed positive trends that failed to reach statistical significance on a range of secondary trial goals, the company said, providing details for the first time.
The ability to carry out activities like dressing and eating is often impacted by Alzheimer's disease, which reduces cognitive ability like memory and language.
The drugmaker said it immediately hired external counsel to conduct an independent probe after it was made aware of the allegations.
Lilly said the behavior exhibited poor judgment by Smiley. The company would not give further details on the communications or the number of employees involved.
Antibody treatments work by recognizing and locking onto foreign invaders to prevent infection of healthy cells.
We are impressed with Lilly's data, in particular the reduction in hospitalizations, and are enthusiastic about the potential for these neutralizing antibodies as a therapeutic for COVID-19.