Regeneron's closely watched COVID-19 drug didn't appear to help everyone who got it in early clinical tests. The treatment's benefit, according to data released so far by the company, seems confined mostly to people whose immune systems haven't mounted a defense against the new coronavirus.
But without quick, reliable testing, identifying those patients will be a significant challenge, one regulators may be grappling with as they decide whether or not to grant an emergency clearance to the drug, dubbed REGN-COV2.
Regeneron executives, speaking on an earnings conference call Thursday, outlined a strategy they believe will allow their drug to be used most effectively, assuming an emergency use authorization from the Food and Drug Administration.
The company said REGN-COV2, a combination of two synthetic antibodies that bind to the SARS-CoV-2 virus, should be used in infected people at high risk of progressing to hospitalization, such as those with obesity or heart disease. Trial data released last week showed a broad benefit for the use of REGN-COV2 in infected people who weren't sick enough to need hospital care, but much of that was driven by higher-risk patients.
That study also screened participants based on whether they had antibodies already fighting SARS-CoV-2. Regeneron executives said those people showed little benefit. However, because many healthcare facilities don't have the ability to quickly test, the best strategy will likely be to reserve REGN-COV2 for high-risk patients because of initial supply limitations.
"It could be given to all of the eligible outpatients, because there is no risk to the individuals who won't benefit the most," Regeneron's president, George Yancopolous, said on Thursday's call. "The only reason to really limit it at this point, is because there's going to be limitations for the amount of doses available to treat."
The company estimates it will have doses sufficient for 80,000 patients by the end of November and enough for 300,000 by the end of January. The drug's availability will be dependent on the FDA's decision, which could be issued in the coming weeks.
Testing based on virus levels could offer another way for providers to find people most likely to benefit, said company CEO Leonard Schleifer. Patients who haven't generated an antibody response typically have virus levels 1,000 times higher than those whose immune systems have mounted an attack, he said. "So that could be used as your tip to screen patients."
Regeneron is also discussing potential diagnostic approaches with Roche, with which it's partnered to manufacture REGN-COV2. "We're working with them to see whether [their] test can be validated with our data set," he said.
While promising, REGN-COV2's benefit has not yet been conclusively proven, and researchers are still figuring out its risk-benefit profile in different groups of people.
Clinical trial monitors, for example, recently paused testing of REGN-COV2 in hospitalized COVID-19 patients who need high-flow oxygen support or mechanical ventilation because of a "potential safety signal and an unfavorable risk/benefit profile."
Responding to analysts' questions, Yancopolous said Regeneron has not seen the results because the committee overseeing the trial is still evaluating the data.
"We remain hopeful that there is not going to be a safety signal and, eventually, at least in some subset of these patients, even the hospitalized patients that we may provide a benefit," he said.