Dec 1 (Reuters) - BeyondSpring Inc (BYSI.O) said on Wednesday the U.S. Food and Drug Administration (FDA) had declined to approve its drug candidate for prevention of chemotherapy-induced neutropenia, citing need for an additional study, sending its shares down nearly 56%. The regulator indicated that results from the company"s late-stage trial did not provide enough evidence on the benefits of the drug, plinabulin, and that a second trial would be required to support the marketing application, the company said. "BeyondSpring"s prospect to profitability is solely reliant on the clinical, regulatory, and commercial success of plinabulin," William Blair analyst Andy Hsieh said, downgrading the company to "market perform" factoring in the capital investment and time needed to conduct a second late-stage trial. Neutropenia, a decrease in the number of white blood cells (WBCs) is a common complication of chemotherapy that kills healthy WBCs along with cancer cells, increasing a patient"s susceptibility to infections. About 60,000 cancer patients in the United States are hospitalized with the condition and 4,000 die of fever associated with neutropenia, according to the U.S. Centers for Disease Control and Prevention. BeyondSpring said in November last year plinabulin in combination with an anti-infection drug met the main goal in its late-stage trial, demonstrating improvement in the rate of prevention of neutropenia. The company"s neutropenia program is the farthest along in its pipeline, followed by its study of plinabulin as a potential second or third line treatment for non-small-cell lung cancer. Plinabulin is also under regulatory review in China for neutropenia prevention and Jiangsu Hengrui Pharma has obtained the rights to sell and co-develop the drug in the region. Shares in the company, which said it intends to work with the FDA to determine the drug"s pathway for neutropenia prevention, were trading at $5.65.