FDA throws up a tricky roadblock for Arena's lorcaserin

The FDA has issued a Complete Response Letter to Arena Pharmaceuticals (ARNA) rejecting an immediate approval for the weight drug lorcaserin and pointing the developer down a very narrow regulatory path that just might let the developer skirt the need for new clinical studies. Arena eagerly announced plans to meet with the FDA as soon as possible to address its concerns, hopeful that it won't have to wait very long to get a thumbs up. Some analysts, however, sounded distinctly doubtful that any quick resolution is in the offing and at least one thought the delay could stretch out as much as five years.

Arena announced the CRL on Saturday, a day after the agency's PDUFA date for one of the most closely watched decisions of the year. In it, the developer said, the FDA detailed its concerns about signs of tumors found during an animal study and voiced concerns that the weight-loss experienced by non-diabetics in its clinical trials was marginal. Regulators asked for new data from a one-year study of obese and diabetic patients and asked Arena to come up with one or more independent experts to take a second look at the tumor data to see if the agency's cancer worries can be addressed. In the event the FDA is left unconvinced, "additional clinical studies may be required to obtain a more robust assessment of lorcaserin's benefit-risk profile."

"This is an important step for us toward the FDA's approval of lorcaserin," said Arena CEO Jack Lief, who added that he's seeking a Type A meeting, which would have to be conducted within 30 days. "While the complete response letter provides us with recommendations from the agency, we intend to meet with the FDA to obtain further clarity on the approval path and timeline. We will work with the agency to address the issues with our NDA as quickly as possible."

Just how quickly, however, is hard to gauge. Matthew Herper at Forbes, who's been following the progress of lorcaserin closely, added up the various regulatory worries and concluded that Arena was facing a delay of at least a year. On top of the immediate delay in waiting for a meeting, Herper expects the agency to classify the next step as a Class 2 resubmission, which will add another six months past Arena's response. While preliminary data from Arena's current trial is due soon, full results could take months.

Piper Jaffray analysts Edward Tenthoff and Chad Messer looked over the FDA's response and came up with a far bleaker outlook, estimating that Arena and its partner Eisai won't get a final decision for at least three years and may have to wait until 2015. Arena's immediate goal will be to soothe anxious investors.

In a conference call this morning, Lief said that Arena and Eisai are committed to moving forward together on development of the drug, though the CEO didn't answer a question about whether Eisai would drop out of the pact if lorcaserin is approved for Type II diabetes patients only. The CEO expects Arena to end the year with $150 million and wouldn't comment on any potential cuts to its staff.

ALSO: After FDA's ARNA decision, what's next for obesity drugs? Story

PLUS: A look back at Arena's lorcaserin. Timeline

- here's the press release
- read the Reuters story
- here's the analysis from Forbes' Matthew Herper 

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