However, he said the strain found in South Africa likely presents greater challenges.
"The South African variant ... is the one of concern. It has more dramatic mutations to that spike protein, which is the target" of these antibody drugs, Ricks said on "Squawk Box." "Theoretically, it could evade our medicines."
Eli Lilly's antibody drug received emergency use authorization from the U.S. Food and Drug Administration in November. The drug is targeted toward people who are recently diagnosed with Covid-19, with the hopes of preventing the need for hospitalization. Regeneron's Covid-19 antibody treatment, which President Donald Trump received after contracting the disease, also has received limited clearance from the FDA.
Ricks said Eli Lilly wants to work with the FDA to be able to quickly test different versions of antibodies to see whether they would be effective against virus variants such as the one found in South Africa.
"We actually have a large library of these antibodies now that are sitting pre-clinically," said Ricks. "We could think about a very expedited path to study them in maybe a month or two, and then authorize their use. That would seem to be a smart thing to do as this virus mutates."
Coronavirus variants initially found in the U.K. and South Africa have garnered significant attention in recent weeks. They are believed to be more transmissible — but not more deadly — than previous strains. Even so, a more contagious virus that leads to more infections could further burden health-care systems and lead to more fatalities.
The discovery of these mutations also coincides with the rollout of Covid-19 vaccines from drug makers such as Pfizer and BioNTech, as well as Moderna. It has led to some questions about whether the vaccines — along with treatments for the disease — would retain their efficacy.
In a CNBC interview Monday, BioNTech CEO Dr. Ugur Sahin expressed confidence that its vaccine, produced in partnership with Pfizer, would work against the virus strains found in the U.K. and South Africa.
Gilead Sciences CEO Daniel O'Day told CNBC it is testing its treatment remdesivir against those new strains, but he said Monday the antiviral drug would likely be effective. Antivirals such as remdesivir try to prevent the virus from replicating. By contrast, antibody drugs like Eli Lilly's attach to the existing virus in the body and attempt to neutralize it.
There have not been any confirmed cases of the variant first discovered in South Africa in America, but according to The Wall Street Journal, it has been detected in countries such as Japan, South Korea and Switzerland. In the U.S., there have been about 70 confirmed cases of the coronavirus variant initially found in the U.K., according to the Centers for Disease Control and Prevention.
"It seems clear that the single antibody from Lilly, and probably the cocktail from Regeneron, will arrest that, just like it does the normal variant," Ricks said of the strain linked to the U.K. "We haven't done a clinical study to that effect, but we have pre-clinical data that is highly suggestive that that is not going to be an issue."
After the FDA granted emergency use authorization to Eli Lilly and later Regeneron for their antibody therapies, challenges arose around actually delivering the drug, which requires intravenous infusion, to Covid patients. In mid-December, CNBC reported that between 5% and 20% of the delivered doses had been administered.
That figure is now "climbing," Ricks said Monday. He pointed to Alabama as one state where the antibody drugs are being used widely. Alabama "basically runs out every week and gets refilled," he said.
"There's quite a range" from state to state, Ricks acknowledged. "We wish all states could learn from those practices and really use this medicine because the benefit is it keeps patients out of the hospital, particularly seniors. We know if you're a senior and you have Covid-19 and you end up in a hospital bed, the outlook is not good."