Thanks to dosing logistics, COVID-19 antibodies from Eli Lilly and Regeneron have gotten off to a slow start in the U.S., and now they’re facing a new stumbling block in viral variants.

While the two companies are scrambling to learn about their meds’ efficacy against the variants, other drugmakers are advancing their own antibodies with eyes on both challenges—dosing and the new variants.

Eli Lilly, which has agreed to sell 950,000 doses of its bamlanivimab antibody to the U.S., believes the drug “should maintain full activity against the new strain originating in the U.K.,” a spokeswoman said.

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But the variant that originated in South Africa presents another scenario: The company’s tests show the “first generation of antibody therapies, including bamlanivimab, etesevimab and others may not be as effective.”

As for Regeneron, a spokeswoman said that “everything we know so far about these new variants and our antibodies—including data from preliminary neutralization analyses and against other currently circulating variants—indicate that our antibody cocktail will remain effective against new strains.”

RELATED: Lilly and Regeneron COVID-19 antibodies are available all over the U.S. Why aren’t they getting to more patients? 

One of Regeneron’s antibodies in the cocktail “may be susceptible” to the South African variant, the company’s spokeswoman said, but the other should still work. That’s the “exact idea behind the combination approach,” she said, which is to “mitigate risk.”

“As we know, viruses change over time, so the appearance of this new variant is not a surprise,” she said. “Again, this is the reason we take a multi-antibody approach in our infectious disease programs, as the virus would need to mutate in two distinct locations to evade the binding and neutralizing capacity of both antibodies.” 

The Lilly and Regeneron antibodies launched in November after FDA emergency use authorizations, but uptake has been slower than expected because the meds are infused under a healthcare provider’s supervision. That’s difficult because they’re only authorized in patients with mild-to-moderate illness who aren’t typically in a hospital.

RELATED: AstraZeneca gets $486M to test if COVID-19 antibodies can provide 12 months of protection 

States and hospitals are working to raise awareness of the meds—and they’ve set up infusion centers and transportation networks to get patients to treatment.

Meanwhile, new antibodies that are administered via injection or protect against new variants are in the works, as the Wall Street Journal reports

AstraZeneca is studying its antibody combination AZD7442 to prevent infection and as a post-exposure prophylaxis, and it’s planning to study the combo as a treatment in 4,000 patients. An injection rather than an infusion, the cocktail would be much easier to get to patients. The company’s in discussions with pharmacy chains to eventually open access for patients who’ve tested positive for COVID-19 at local stores.

“We want it to be same day, same location,” Mark Esser, VP for microbial sciences, told the Journal.  

In October, the U.S. government invested $486 million to help fund AZ’s antibody research and purchase up to 100,000 doses. The government also has the option to purchase another 1 million doses down the line. 

RELATED: Vir CEO Scangos on competing in the COVID antibody space—and life beyond the pandemic

Aside from the dosing challenge, biotechs are researching antibodies that could protect more broadly against Sars-CoV-2 variants. Vir Biotechnology, a newer biotech with no marketed products, is advancing a phase 3 candidate based on a sample from a SARS patient in 2003, the Journal reports. Researchers designed the drug to be protective even when the virus mutates.

Vir is testing its medicine as an infusion in clinical trials, but the company is also working on an injection formulation, its CEO George Scangos told the Journal.

A new biotech, Adagio Therapeutics—a spinout of Adimab—plans to advance its own antibody drug based on a SARS patient’s sample, according to the newspaper. The company believes the drug will be effective against COVID-19 variants and similar coronaviruses that may pose a threat in the future.