(Adds details on the antibody, preclinical study results, background)

May 26 (Reuters) - Shanghai Junshi Biosciences Co Ltd 1877.HK said on Tuesday it plans to start clinical studies to test its experimental antibody against COVID-19 in the United States and China in the second quarter of the year, with partner Eli Lilly and Co LLY.N .

Lilly and several other drugmakers such as Gilead Sciences GILD.O , Pfizer Inc PFE.N and Merck & Co Inc MRK.N are racing to develop treatments or vaccines for the fast-spreading respiratory illness caused by the novel coronavirus.

Junshi said the companies intend to file an application to begin human testing of one of their two antibodies - protective proteins produced in response to infection - tested first in rhesus monkeys.

Shanghai Junshi said results from the preclinical studies, published in the science journal Nature, show that both the tested antibodies, called CA1 and CB6, showed substantial neutralization activity against the virus.

The company said CB6, which showed a greater reduction in virus levels in the monkeys, will be advanced to human trials.

Separately, Merck on Tuesday announced a deal and multiple partnerships to develop vaccines and test an antiviral drug against COVID-19.