Adcom recommends Potiga approval but will success be resounding?

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Partners Valeant Pharmaceuticals International and GlaxoSmithKline could breathe a sigh of relief yesterday after an FDA advisory commitee gave unanimous support for approval of anti-epileptic Potiga (ezogabine/retigabine) for partial onset seizures, after concerns were raised about the drug causing urinary complications (Event - FDA on parallel track with Europe on Potiga, August 3, 2010).

About one quarter of phase I and II trial patients reported issues, mainly urinary retention. The adcom decided that, despite presenting a significant safety problem, this could be addressed through a patient monitoring system. The companies now await a decision from the FDA due by August 30, and although many are now predicting good news a delay is probably likely, given the time frame. Approval in Europe is also anticipated in the fourth quarter. So while consensus is that the drug will have few further troubles gaining approval, the focus now shifts to Potiga’s commercial potential, and predictions here seem to differ.

Urinary retention manageable

The first-in-class, potassium channel/GABA agonist has been filed for approval in patients already refractory to one to three anti-epileptics. The FDA’s Peripheral and Central Nervous System Drugs Advisory Committee saw the urinary retention problem for Potiga as manageable, given the companies’ plans for patient monitoring and a postmarketing observational trial.

One panellist, though, Dr Philip Hanno, attending urologist at the University of Pennsylvania Hospital, did express concern that Potiga’s effects on urinary disorders could be more marked than is initially obvious from the studies presented. Dr Hanno thought that the unexpected emergence of at least one patient with renal failure, and lack of any urodynamic studies, were particularly worrying, given the potentially huge population this drug could service.

That said, the panel were unanimous in their approval, and on a second quarter results conference call days before, no other issues were raised by analysts. Gaining adcom support despite a major safety concern has removed the biggest hurdle for Valeant, and no doubt will make merger partner Biovail happy. Choppy stock market conditions saw Valeant’s share price dip to $57.09 yesterday, which climbed back to $58.40 upon announcement of the adcom’s decision, close to the record high of $59.38 touched earlier this month.

Mixed forecasts

Jefferies, which sees the drug as a potential blockbuster, predicts that Potiga will generate $100m in alliance-based revenues to Valeant in 2014. Bank of America-Merrill Lynch, however, set its 2014 estimates at half that figure, despite expressing confidence during the entire course of 2010 that Potiga would be approved and become a success.

Consensus data from EvaluatePharma has GSK booking $219m in worldwide sales in 2016. One of the most bullish analysts, Credit Suisse, predicts worldwide sales in 2016 of $357m, compared to the most bearish, once again, Bank of America-Merril Lynch, showing 2016 forecasts of $169m.

These differing forecasts no doubt reflect varying levels of confidence in the drug’s success. For example some analysts believe its thrice-daily dosing schedule could prove a hindrance, and others point to an apparent lack of added efficacy over other marketed anti-epileptics. With many of these agents due to lose patent protection, these issues could be particularly damaging if the urinary issues become more marked in a wider population.

Still, there are few doubts from all sides over whether Potiga will be approved, in both the US and Europe. However, the question of commercial potential remains, as the partners ready themselves to commit serious marketing money to Potiga.

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