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Rescripting PAH

Bayer's riociguat gives FDA new opportunity to shift how it evaluates PAH rugs

If FDA approves Bayer AG's entire dose titration scheme for Adempas riociguat, the agency will be departing from its past decisions on PAH drugs, which have been determined by significant improvements on six-minute walk distance, not by surrogate cardiopulmonary markers.

The agency's Cardiovascular and Renal Drugs Advisory Committee laid the groundwork last week.

In two separate votes, the panel voted 11-0 that Phase III data for riociguat support approval to treat pulmonary arterial hypertension (PAH) and chronic thromboembolic pulmonary hypertension (CTEPH) at the company's proposed titration doses of 0.5, 1, 1.5, 2 and 2.5 mg.

The advisors brushed off agency concerns that the highest dose of riociguat conferred no additional benefit on six-minute walk over lower doses while increasing the risk of hypotension. The panel was swayed by Stuart Rich of University of Chicago Pritzker School of Medicine, a permanent voting member and one of only two pulmonologists on the 11-member committee.

Rich made clear he preferred evaluating a PAH drug's benefit-risk profile using a hemodynamic measure like cardiac output rather than the primary endpoint of six-minute walk distance (6MWD), which FDA reviewers relied on in their analysis. The highest riociguat dose showed improvements in cardiac output compared with lower doses without showing improvements in 6MWD.

While Rich's views may have led the panel to take a more holistic view of riociguat, the

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