Boehringer bags a 'breakthrough' tag for its Pradaxa antidote

German giant Boehringer Ingelheim is racing to the market with an antidote to its blockbuster blood-thinner Pradaxa, securing the FDA's coveted breakthrough therapy designation for its in-development treatment.

The antidote is a fully humanized antibody fragment designed to reverse the anti-coagulant effects of Pradaxa, which prevents clotting by blocking the enzyme thrombin. Dubbed idarucizumab, Boehringer's reversal agent charted immediate, complete and sustained reversal of Pradaxa's effects in a Phase I study, the company said, and a Phase III trial is in the midst of enrollment.

The FDA's breakthrough tag guarantees a speedy review and a front-row seat with regulators, and Boehringer is planning to pursue an accelerated approval for its antidote.

Boehringer says idarucizumab is the first specific antidote for any of the new class of oral anticoagulants--which includes Bayer and Johnson & Johnson's ($JNJ) Xarelto as well as Bristol Myers-Squibb ($BMY) and Pfizer's ($PFE) Eliquis.

Pradaxa sales grew 9% to about $1.7 billion last year, likely creating a sizable market for a treatment to reverse its effects in uncontrolled bleeding situations.

But Boehringer's not alone in the antidote space. Portola Pharmaceuticals' ($PTLA) has a breakthrough tag of its own for andexanet alfa (PRT4445), an anti-anticoagulant already in Phase III trials to reverse the effects of Factor Xa blockers. Portola's drug essentially works as Factor Xa decoy, fooling inhibitors like Xarelto into targeting it instead of the body's coagulation-regulating enzymes and thus halting the effect of blood thinners and keeping patients safe in major bleeding events.

Boehringer is quick to point out that the development of an antidote in no way undermines its faith in Pradaxa's safety. In May, the company agreed to pay about $650 million to settle more than 4,000 lawsuits tied to the blood thinner, a move that came just months after the FDA reviewed data on the drug and concluded that, when used as directed, it's as safe as warfarin.

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