Japanese drugmaker Astellas has redrawn its marketing partnership with Canada’s Cardiome in the wake of the US Food and Drug Administration’s rejection of their marketing submission for RSD1235 for atrial fibrillation.

The two companies said they met with the FDA last Friday and are now confident that the marketing application for the drug will go ahead later this year. In the meantime, Astellas has reinforced its commitment to the project, agreeing to shoulder the costs of the revised filing.

The FDA turned the dossier down because of inconsistencies and omissions in the way the information was presented, rather than any failings in the data. Both Cardiome and Astellas said that no additional clinical trials would be required.

Astellas also said it would ahead with a $10 million milestone payment to Cardiome on the second filing. Under their original agreement, this had been conditional on the FDA accepting the application for review.

Datamonitor believes RSD1235 still has a significant role to play in the fast-growing market for anti-arrhythmic drugs – expected to rise from $1 billion at present to $3 billion in 2015, even though the product looks set to be delayed by around a year.

Prior to the refusal-to-file notification from the FDA, Datamonitor had predicted that the intravenous formulation of RSD1235 would capture 25% of the marketplace by 2015 and be the top-selling product in the segment. It now believes that the delay will allow a rival compound Stedicor (azimilide) from P Pharma to capture the top slot.

That said, both these agents, as well as Sanofi-Aventis’ new Multaq (dronedarone) candidate, look likely to win significant sales in the region of $500 million or more, according to Datamonitor.

Cardiome is also working on an oral formulation of RSD1235 in Phase II trials. Results from that programme are expected within the next few weeks.

Osteoporosis drug filed in Japan

Meantime, Astellas and ONO Pharmaceutical have filed for approval to market the osteoporosis drug YM529/ONO-5920 in Japan. The compound, which is also known as minodronic acid hydronate, is a bisphosphonate that will compete with other drugs in this class such as Merck & Co’s Fosamax (alendronate).

Astellas and ONO claim minodronic acid is one of the most potent drugs in the bisphosphonate class.