Jan 11 (Reuters) - Regeneron Pharmaceuticals Inc's dual antibody therapy for COVID-19 will likely be effective against new variants of the coronavirus identified so far, the drugmaker's chief executive officer said on Monday.

The discovery in recent weeks of highly transmissible new variants of the coronavirus in the United Kingdom and South Africa has raised alarm that current drugs and vaccines against the virus might be rendered less effective.

Eli Lilly and Co said its coronavirus antibody treatment, bamlanivimab, which is approved for emergency use by the U.S. Food and Drug Administration, is effective against the UK variant, but may not be able to neutralize the one identified in South Africa.

Experiments are underway, but the coronavirus version found in South Africa "has a number of changes in the spike proteins that could make antibodies less effective," Daniel Skovronsky, Lilly’s chief scientific officer, said in an interview on Sunday.

Regeneron's two-antibody combination also has FDA emergency use authorization for patients with mild to moderate COVID-19.

"Having a cocktail makes it more likely we will be able to deal with variants that might pop up," Chief Executive Officer Leonard Schleifer said during the J.P. Morgan Health Conference.

Regeneron said its cocktail approach has resulted in a treatment that should work against the major variants described in South Africa and the United Kingdom.

The UK variant has turned up in at least nine U.S. states including hard-hit California. The South Africa variant has not yet been found in the United States, which lags other nations in sequencing coronavirus samples.

"Let's hope we can keep it that way," Skovronsky said, noting that Lilly continues to work on additional antibody drugs, including cocktail approaches.

Regeneron reported fourth-quarter net sales of $144 million for its combination of casirivimab and imdevimab.

"We are also working on additional cocktails should the virus continue to mutate and escape," Regeneron President George Yancapoulos said.

The company said there was substantial demand for its COVID-19 therapy and that it was collaborating with Roche Holding AG to address demand outside the United States. (Reporting by Mrinalika Roy and Manojna Maddipatla in Bengaluru and Deena Beasley in Los Angeles; Editing by Shinjini Ganguli and Bill Berkrot)