NEW YORK (AP) — Celgene Corp. said it will stop a late-stage study of its cancer drug Revlimid because leukemia patients who took the drug were more likely to die than patients who were given an older treatment.

The biotech drugmaker’s shares, which have been trading at all-time highs, slumped $4.79, or 3.4 percent, to $131.92 in morning trading Thursday.

The Summit, N.J., company was running a trial of Revlimid as a treatment for B-cell chronic leukemia as part of an effort to broaden the approval of Revlimid and boost sales. Celgene said the Food and Drug Administration placed the study on hold Friday, halting the use of Revlimid in the study. Celgene said it found that patients who were given Revlimid were more likely to die than patients who received the other drug in the study, GlaxoSmithKline PLC’s Leukeran.

The company said 210 patients were treated with Revlimid and 34 died, compared to 18 deaths in 211 patients treated with Leukeran. Celgene said the cause of the imbalance in deaths hasn’t been identified.

The study compared Revlimid to Leukeran as a treated with chronic B-cell leukemia in patients 65 and older. The patients were not considered candidates for treatment with more aggressive chemotherapy drugs because they had health problems like diabetes, heart failure, or kidney impairment.

Celgene said studies of Revlimid as a treatment for chronic lymphocytic leukemia are continuing. The investigators are being told about the trial stoppage and they are being told to inform patients.

Revlimid is approved as a treatment for multiple myeloma in patients who have received at least one previous round of treatment. The drug is also approved as treatment for severe anemia and in June the FDA cleared its use against mantle cell lymphoma.

In the first quarter Celgene reported $1 billion in sales of Revlimid, about two-thirds of its total revenue. The company reported $3.77 billion in Revlimid sales in 2012 and expects $4.1 billion to $4.2 billion in 2013.

Celgene shares have climbed 74 percent in 2013 and peaked at $137.80 on Wednesday.