"There are always so many moving parts, but … we're hitting our best numbers, our best timelines, and things are going really well," Dr. George Yancopoulos, Regeneron's co-founder, president and chief scientific officer, said in a telephone interview Monday night.

The company had previously said it aimed to have hundreds of thousands of doses ready for human testing in late summer, so the new goal is a significant acceleration. Regeneron said it plans to start large-scale manufacturing by the middle of next month and still plans to ramp up to hundreds of thousands of preventive doses a month by the end of summer.

The approach involves creating antibodies to the virus that could be used to treat the disease and to prevent it, Regeneron said in a statement Tuesday.

Biotech giant Regeneron said it aims to have doses of a potential drug for COVID-19 ready to start human clinical trials by early summer.

Regeneron is developing the therapy the same way it created a drug for Ebola, which is now under review by the FDA, and four other drugs already on the market: It uses mice genetically engineered to have human-like immune systems. The mice are exposed to a target protein and generate human antibodies in response.

Those antibodies are now used in medicines approved to treat such maladies as asthma, high cholesterol, rheumatoid arthritis and cancer.

The approach has been heralded by health experts including former Food and Drug Administration Commissioner Dr. Scott Gottlieb as among the most promising for new tools to apply against the novel coronavirus potentially in the fall, when infections could resurge even if they tamp down during the summer.

For COVID-19, the mice were exposed to part of the SARS-CoV-2 virus. Regeneron said its scientists have now isolated hundreds of antibodies that neutralize the virus, and they're sorting through them — as well as antibodies isolated from people who have recovered from COVID-19 — to find the best two with which to create a cocktail treatment.

Yancopoulos said Regeneron plans to combine two antibodies because "you want to ensure if, God forbid, there's a mutation or variation in the virus, you don't lose [efficacy] due to that one antibody."

For Ebola, Regeneron used the same approach to create a three-antibody cocktail, which proved life-saving in a clinical trial in the Democratic Republic of Congo in 2018.

The approach to provide treatment and protection in one potential medicine for COVID-19 puts Regeneron somewhere in between the vaccine projects underway at Moderna, Johnson & Johnson, Sanofi, and others, and the hunt for medicines across the industry, including at Gilead Sciences. Yancopoulos said the duration of protection that Regeneron's antibodies could provide is unknown before human studies are run, but extrapolating from earlier experience, they "expect one dose to last at least a month."

The dose needed for protection is a lot less than for treatment after someone is infected, he said, which is why Regeneron's goal of hundreds of thousands of doses by late summer applies to preventive use.

"For every hundred people you 'prophylax,' you can probably treat like five or 10 people," Yancopoulos said.

He noted the first people likely to receive the prophylactic treatment would be health-care workers and others at high risk for the disease. They would likely need a dose once a month until a vaccine conferring longer-term immunity becomes available. (National Institute of Allergy and Infectious Diseases Director Dr. Anthony Fauci, who is leading the nation's COVID-19 vaccine development, has said a vaccine won't be available for a year to 18 months.)

And though Regeneron is meeting its own most optimistic timelines for the project, Yancopoulos said, "it still depends on a lot of things going right. This is biology, not coding or writing an app. There are a lot of things that can still go wrong."

The company also said Monday it is starting clinical trials of its rheumatoid arthritis drug, Kevzara, to treat the severe immune response that can occur in the lungs of patients with COVID-19. Since that drug is already on the market, it could provide an immediate option for the most critical patients, if it's successful.

"We really do feel," Yancopoulos said, "like we've been preparing for years for this opportunity to make a difference."