© Reuters. FILE PHOTO: A Gilead Sciences, Inc. logo is seen outside the company headquarters in Foster City, California, U.S. May 1, 2018. REUTERS/Stephen Lam/File Photo

(Reuters) – Gilead Sciences (NASDAQ:) said on Wednesday the U.S. Food and Drug Administration had put a hold on trials testing the company’s blood cancer drug following increased risk of patient death in some studies.

The company will stop testing the drug, magrolimab, for all blood cancers and will review its safety across other studies such as those in patients with colon and breast cancers.

Gilead gained access to the drug through its $4.9 billion purchase of Forty Seven Inc in 2020.

Shares of the company, which forecast 2024 sales below estimates late Tuesday, were down 3.6% in noon trading.

The drug is an antibody treatment that blocks a type of protein, called CD47, which helps damaged cells avoid destruction by the immune system.

An analysis of a late-stage trial and other studies showed an increased risk of death, the company said, adding it also showed that the drug was unlikely to succeed in the trials.

The company had discontinued the study of the drug in combination with a type of chemotherapy in patients with a higher risk of myelodysplastic syndromes in July.

I-mab, Innovent Biologics, Akeso are among companies looking to develop similar class of drug for cancer.

(This story has been corrected to remove reference to Eli Lilly (NYSE:) in paragraph 8)