Safety of Eliquis Questioned Due to Missing Clinical Trial Data

Thursday, September 17, 2015
Eliquis Anticoagulant

Among the three new generation oral anticoagulants – Pradaxa, Eliquis and Xarelto – released in the past few years to replace the traditional standby warfarin, Eliquis has made the boldest claims about decreasing the risks of stroke, internal bleeding and death.

However, a new report out last month indicates the data relied upon by Pfizer and Bristol-Myers Squibb in making claims about Eliquis’ safety may be flawed. And, at least one FDA reviewer has called for changes to the drug’s label to reflect this.

The questions surround missing data from some 300 patients involved in Eliquis clinical trials. With Pfizer/BMS making claims that their drug is superior to others, experts say the missing data could actually have enough of a statistical effect that the safety claims are no longer valid.

Initially, a March 2012 approval hearing for Eliquis was pushed back to June, then eventually December of 2012 due to questions of data loss. The drug was eventually approved that year to prevent stroke in patients with atrial fibrillation.

However, an internal FDA memo released this year shows that at least one agency reviewer, Thomas Marciniak, was so concerned with missing data that he had no confidence that Eliquis was safer than warfarin, as its makers have claimed.

In a memo sent to other reviewers in December 2012, Marciniak explained that over 300 patients involved in Eliquis clinical trials had missing data. And, if this data showed at least one more death among Eliquis users, or one fewer among warfarin users, it would statistically eliminate the benefit.

Of course, the missing data could also show that Eliquis is even safer than expected. Or, it could show it to be more dangerous than warfarin, Xarelto and Pradaxa. However, the public and FDA may never know until additional studies are completed.

In his memo, Marciniak called for a description of the missing data problems in Eliquis’ label. However, other members of the review board disagreed.

A recent analysis by Forbes concluded that Eliquis will account for roughly 25% of the value of BMS in coming years, so they are unlikely to add any label warnings that could suggest the drug is less safe than advertised.

However, BMS and Pfizer recently announced a new 4,600 patient study called AUGUSTUS to measure Eliquis’ safety profile against warfarin.

DrugNews will continue to track and new developments with Eliquis and other blood-thinning drugs.



Jones, C. Slippery Slope: FDA Reviewer Questions Eliquis Mortality Claim. MedPage Today. (August 2, 2015). Retrieved from

Fauber, J. Eliquis claim about reduced deaths questioned by FDA reviewer. Milwaukee Journal Sentinel. (August 1, 2015). Retrieved from

Trefis. Why Eliquis is so important for Bristol-Myers Squibb. Forbes. (September 15, 2015). Retrieved from

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