Eli Lilly and Co. /zigman2/quotes/200106384/composite LLY -0.35% said Friday it is seeking a revocation of the emergency use authorization granted by U.S. regulators for its bamlanivimab antibody treatment for COVID-19 alone in order to complete the transition to bamlanivimab and etesevimab together. "Lilly made this request due to the evolving variant landscape in the U.S. and the full availability of bamlanivimab and etesevimab together," the company said in a statement. The combination has proved to be more effective in neutralizing the COVID-19 variants that have been detected in the U.S. after first emerging in the U.K., South Africa and Brazil, and that are more infectious than the original virus. The combination is also better at treating the rapidly growing B.1.427/B.1.429 California strain that currently accounts for 50% of virus cases in California and over 10% of cases in other states. "In the U.S., bamlanivimab alone should no longer be administered. However, sites of care should not dispose of bamlanivimab supply; instead, they should order etesevimab to pair with it," said Lilly. Bamlanivimab was the first neutralizing monoclonal antibody to receive an EUA from the FDA as a treatment for mild to moderate COVID-19 and more than 400,000 patients have been given it. Lilly estimates that has prevented more than 20,000 hospitalizations and at least 10,000 deaths during the peak of pandemic cases. Lily expects that in collaboration with Amgen Inc. /zigman2/quotes/209157011/composite AMGN +0.40% , it can manufacture sufficient supply of the two antibodies to meet global supply needs. Lilly shares were up 0.6% premarket, and have gained 10% in the year-to-date, matching the S&P 500's /zigman2/quotes/210599714/realtime SPX -0.25% gains.