Shares of Ariad Pharmaceuticals tumbled again Friday after the company said it is ending a study of its cancer drug Iclusig because of recently disclosed side effects.

Ariad said it is stopping a late-stage trial of Iclusig as a treatment for newly diagnosed chronic myeloid leukemia because of “arterial thrombotic events,” or side effects related to blood clots in patients’ arteries. The company said last week that those blockages were occurring more often than it had previously believed. Ariad said it is stopping the trial by mutual agreement with the Food and Drug Administration, and patients are being removed from treatment and will be transferred to care of their physicians.

The company’s shares dropped $1.79, or 40 percent, to $2.71 in morning trading. Earlier in the session shares touched $2.62, their lowest point since February 2009.

The Food and Drug Administration approved Iclusig in December to treat two rare types of leukemia: treatment-resistant chronic myeloid leukemia and acute lymphoblastic leukemia in patients with a type of chromosome abnormality. It is the Cambridge, Mass., company’s first approved product, and Iclusig sales totaled $13.9 million in the second quarter. The company is running additional studies to expand the marketing approval and improve sales.

On Oct. 9 the company disclosed a higher rate of side effects related to blood clots. Ariad Pharmaceuticals Inc. said that after two years of research in another late-stage study, 11.8 percent of patients treated with the drug suffered a serious blood clot in an artery, worsening from the 8 percent rate after 11 months. The FDA halted enrollment of patients in new studies, although treatment of patients who were already enrolled in those studies hadn’t stopped. The company said patients would have reduced dosages of Iclusig, however.

Iclusig is a pill intended to be taken once per day. In the latest trial, which was called EPIC, a total of 307 patients were being treated with either Iclusig or Novartis AG’s drug Gleevec.