Shares of Eli Lilly & Co. /zigman2/quotes/200106384/composite LLY +0.79% were up 0.3% in premarket trading on Monday after the company said the U.S. government modified purchase agreements for its COVID-19 antibody therapies. The agreement for bamlanivimab, which was the first Lilly antibody treatment to receive emergency authorization, now includes etesevimab. Using a combination of the two antibody therapies is more effective against some of the new virus variants that have emerged. Lilly said the new agreement terminates the original purchase agreement for bamlanivimab and in effect cancels the roughly 350,000 doses of bamlanivimab that had been scheduled for delivery in March. Lilly's stock has gained 9.2% since the start of the year, while the S&P 500 /zigman2/quotes/210599714/realtime SPX +0.74% has gained 9.9%.