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It could be two weeks until there is news on a paused trial of Eli Lilly’s closely watched monoclonal antibody treatment for Covid-19.

The National Institutes of Health said late Tuesday that it paused the trial because one of the two groups in the study — one had received the antibody, the other a placebo — was doing better than the other. Both groups also received remdesivir, a Covid-19 treatment from Gilead Sciences. 


The NIH said the trial’s independent data and safety monitoring board, or DSMB, noted Tuesday morning that the study had reached a “predefined boundary for safety” after five days of treatment, meaning that there was an overall difference between the two patient groups. The agency, however, did not indicate whether it was the treatment group or the placebo group that may have crossed a safety threshold. 

The DSMB, a group of independent experts overseeing the trial to ensure the safety of patient volunteers, then recommended pausing the enrollment of new patients in the study, according to the NIH.

The investigators running the study, who are the ones actually enrolling and treating patients, remain unaware of which patients received the treatment, LY-CoV555, and which received placebo. The investigators will continue to follow the study’s 326 patients, and the DSMB will meet again on Oct. 26, the NIH said in a statement.


Lilly’s antibody has been in the spotlight since the company said that the treatment reduced the amount of virus in patients’ nasal swabs and appeared to help keep patients out of the hospital. Since then, Lilly has announced further results for LY-CoV555 used in combination with a second antibody that also targets the coronavirus. 

Regeneron Pharmaceuticals, a competing firm, also released promising results of its own monoclonal antibody cocktail, which was then used to treat President Trump when he contracted Covid-19.

But the studies that have read out were of people who had been diagnosed with Covid-19 but were not yet hospitalized. The study that has been paused instead tests LY-CoV555 in patients who are in the hospital because of their illness.

When a DSMB meets to look over a study, it can make one of several decisions. It can decide to recommend stopping the study, or making changes, because patients are at risk. It can recommend stopping the study because no answer is likely to emerge. It can stop the study because it is already clear that a treatment works. Or it can allow the study to continue.

It’s not clear what the likely outcome of the DSMB’s deliberations here will be. Both Eli Lilly and the NIH refer to a potential safety issue, which would seem to indicate that the difference between the study groups is due to a potential side effect.

Regeneron said in a statement that trials of its antibody are all active.

The machinations of clinical trials for Covid-19 treatments and vaccines are receiving a large amount of scrutiny. Normally, announcements of clinical trial pauses would not be made until a DSMB had met and made a recommendation. A DSMB meeting that resulted in a study continuing would usually receive no notice. But in the current environment, any sign of change becomes newsworthy.

The pause in the study of the Eli Lilly antibody was first noted by Brief19, a new medical news site run by several physicians. On Sunday, a pause of the study of Johnson & Johnson’s Covid-19 vaccine was first reported by STAT.

In early September, STAT also reported a stop in the U.S. study of a Covid-19 vaccine developed by AstraZeneca. That study has still not begun giving patients new doses of vaccine or enrolling new patients.

  • What does “pause” mean exactly? Does it mean that they are still recruiting or administering the drug to people ? If they are still doing these things, when can this study possibly end? What else can they pause, since biology doesn’t have a pause button? Thanks

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