Amgen announced on Monday that it is stopping its clinical trials for an experimental drug called rilotumumab intended to treat patients with advanced stomach cancer due to the sudden increase of deaths among the study participants.

The California-based biopharmaceutical company said that an independent safety panel observed that more patients were dying after combining the experimental drug with chemotherapy, compared to those who received only chemotherapy, according to an Amgen press release.

"While we are disappointed with these results, we will work with lead investigators to further analyze the data in order to help inform future research and therapies in this area," Sean E. Harper, Amgen executive vice president of research and development, said in a statement.

Ending the experimental drug trial is a setback to the company's plan to submit the results to the U.S. Food and Drug Administration (FDA) for approval next year. Amgen has other drugs pending for approval, including the lung cancer drug blinatumomab, melanoma treatment T-Vec and ovarian cancer treatment trebananib, FierceBiotech reported.

It might also be disappointing news for the more than 74,000 people living with stomach cancer in the United States. According to the National Cancer Institute, the survival rate of patients within five years of diagnosis is only 28 percent based on date from 2004 to 2010. If Amgen's drug was successful, the survival rate could have been higher.

Rilotumumab is an experimental drug developed to slow down the growth of tumor cells. The initial analysis showed that it increased the survival rate of patients with advanced stomach cancer by 33 percent, or up to 5.6 months, when combined with chemotherapy.

Officials were not immediately available for comment.