Ahead of a panel review, staff at the US Food and Drug Administration has backed Bayer's riociguat for two forms of pulmonary hypertension but at a lower dose than the German group is looking for.

In briefing documents released ahead of the FDA's Cardiovascular and Renal Drugs Advisory Committee meeting on August 6, the staffers have recommended riociguat, which Bayer intends to market as Adempas, as a treatment for pulmonary arterial hypertension and chronic thromboembolic pulmonary hypertension. FDA reviewer Preston Dunnmon wrote that the drug, an oral soluble guanylyl cyclase stimulator, should be approved for both indications but recommended "a modified dosing regimen".

Bayer is seeking approval of riociguat, which is under priority review at the FDA, for both indications with a starting dose of 1mg thrice-daily titrated up to a maximum dose of 2.5mg. However, Dr Dunnmon writes that dosing should start at 0.5mg thrice-daily for PAH up to maximum of 1.5mg thrice daily. For CETPH, for which there are no approved therapies, the reviewers said patients with high systolic blood pressure who do not experience an adequate clinical response could be given a maximum dose of 2.5mg thrice-daily.

For PAH, if approved, riociguat would go up against Actelion's Tracleer (bosentan) and Gilead Sciences/GlaxoSmithKline's Letairis/Volibris (ambrisentan). Actelion, which has dominated the PAH market, has filed its follow-up to Tracleer, Opsumit (macitentan), with the FDA and it has a PDUFA date of October 19.