UPDATE: J&J, Bayer Get FDA Response Letter on Xarelto

--J&J, Bayer get second complete response letter from FDA

--FDA rejects Xarelto for acute coronary syndrome patients

--FDA concerned Xarelto causes life-threatening bleeding

(Updated throughout to include Janssen comments and more background.)

By Melodie Warner

Johnson & Johnson's ( JNJ ) Janssen Research & Development LLC said the U.S. Food and Drug Administration again rejected the approval of its blood thinner Xarelto for patients with a heart problem known as acute coronary syndrome.

The FDA had previously rejected Xarelto for this use in June because of concerns about life-threatening bleeding.

Janssen said it is evaluating the second complete response letter and will respond to the agency's questions.

"While we saw an increase in major bleeding, there was no increase in fatal bleeding," said Janssen Vice President Christopher Nessel. "We will continue to work with the FDA to address their questions."

Xarelto is co-marketed by J&J and Bayer AG (BAYRY), and the anticoagulant is one of a new crop of drugs designed to replace an older blood thinner, warfarin, that can be difficult to administer. Since the FDA initially cleared Xarelto in July 2011 to help prevent certain blood clots after knee- or hip-replacement surgery, the agency has recently approved the expanded use of Xarelto for treating certain blood clots and reducing their recurrence.

Bayer also said it remains confident of the safety and efficacy of Xarelto.

Shares of J&J and Bayer closed Monday at $77.20 and $99.06, respectively. Both were inactive premarket.

Write to Melodie Warner at melodie.warner@dowjones.com

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