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OREXIGEN THERAPEUTICS, INC. filed this Form S-1/A on 04/09/2007
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covering the Empatic composition, and we have filed additional patents covering various compositions, methods of use and formulations.
Zonisamide IR was approved in the United States in 2000 for the adjunctive treatment of partial seizures, which is a form of epilepsy. The precise mechanism of zonisamide is unknown; however, it is believed that zonisamide has a number of pharmacologic mechanisms including sodium-channel modulation and enhancement of dopamine and serotonin neurotransmission. Zonisamide, given alone, has also shown weight loss in prior clinical trials conducted at Duke University.
We initiated clinical testing of Empatic, using fixed dosages of zonisamide IR and bupropion SR, with a Phase II clinical trial in 2004. This trial enrolled 127 patients across five clinical sites in a similar protocol to our Phase II clinical trial of Contrave. The primary endpoint for this trial was percent change in body weight 16 weeks after the start of treatment, with secondary endpoints that included percent change in body weight 24 weeks after the start of treatment. The placebo group from the Phase II trial of Contrave also served as the placebo arm in this trial. Results from this trial are summarized as follows:
  •      On an intent-to-treat basis, Empatic demonstrated mean weight loss of 5.2% of baseline body weight at 16 weeks and 5.8% at 24 weeks.
  •      On a completer basis, Empatic demonstrated mean weight loss of 8.3% of baseline body weight at 16 weeks and 9.2% at 24 weeks.
The trial design also included a re-randomization option after week 28 where Empatic subjects could continue either at their same dose or a reduced dose for up to an additional 20 weeks of open-label treatment. For those study participants who continued treatment on Empatic for an additional 20 week extension and remained on the full Empatic dose, mean weight loss at 36 weeks and 48 weeks was approximately 12% of baseline body weight.
The most common side effects observed in our clinical trials of Empatic to date include gastrointestinal upset, insomnia and mild rash.
We recently initiated a Phase IIb clinical trial of Empatic utilizing our proprietary SR formulation of zonisamide. This trial has a matrix design intended to determine the optimal dose ratio of zonisamide SR and bupropion SR to evaluate in further clinical development. The primary outcome measure for this trial will be percent change in body weight 24 weeks after the start of treatment, with a 24 week extension period. We have enrolled over 600 patients across 14 sites in this trial.
We currently retain worldwide marketing rights for both Contrave and Empatic. If approved, we may consider marketing these product candidates to select specialists; however, we expect that Contrave and Empatic have the potential to be prescribed to a significant extent by primary care physicians. In order to target this large group of potential prescribers, we may consider entering into a collaboration with a pharmaceutical company with the sales force and marketing resources to adequately address this physician audience. However, for the foreseeable future, we expect to maintain commercial rights to our product candidates and to continue to develop them independently. We expect to position Contrave for mild to moderate weight loss, particularly in women who report food craving. We believe that Empatic may be especially well-suited for men and post-menopausal women who are heavier and require greater weight reduction. However, the FDA does not distinguish between these types of obesity and, if approved, any potential label for Contrave or Empatic would be expected to refer to obesity generally.
Risk Factors
We are a development stage company with no product revenues and only limited revenues from licensing and collaborative agreements, and our operations to date have generated substantial and increasing needs for cash. Our business and our ability to execute on our business strategy are subject to a number of