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Heads up! Orexigen (NASDAQ:OREX) is to release Phase IIB data for its second weight loss drug Wednesday morning before market open, then hold a conference call at 8:30 a.m. ET. Empatic weight loss results have been somewhat better than those for OREX’s other drug Contrave so far, but it is about a year farther back in development.

As a reminder, both these drugs are combinations of existing, approved drugs available in generic form, with a view toward treating obesity as a disease of the central nervous system. Empatic is a combination of zonisamide sustained release (SR)/bupropion (Wellbutrin) SR, while Contrave is a combination of bupropion SR/naltrexone SR. Zonisamide is used for adjunctive treatment of partial seizures, a form of epilepsy. Its precise mechanism of action is unknown.

What we should be hearing about tomorrow is results from OREX’s second Phase IIb trial, a 24-week study on healthy, non-diabetic, obese patients. This is the first trial in which Empatic has been reformulated with sustained-release components to allow a single daily dose and reduce side effects.

The single daily dose is a bigger deal than one might think at first glance. Many obese patients, even supposedly “uncomplicated” obese patients like those in this study, take all sorts of pills and drugs already, some of which have to be taken apart from one another, or on an empty or full stomach, or as far from bedtime as possible -- so it really can make it much more feasible and practical to take another pill (in medical jargon, this is called “improve compliance”) if there is only one of it.

Previous results for Empatic were strong. Mean weight loss (placebo-adjusted) was 7.5% at 24 weeks and 15% at 48 weeks, with, importantly, little sign of plateau. While I don’t expect to see wildly different results from the new trial, it will certainly be noteworthy if we do. Also, with all the hoopla that has surrounded recent announcements by competitors Vivus, Inc. (NASDAQ:VVUS) and Arena Pharmaceuticals (NASDAQ:ARNA), it can't be bad for OREX to pull the spotlight back toward itself for a while, and may even bring OREX to the attention of any new investors that have started to look at the obesity space lately. (Although I think they should have noticed it before!)

Side effects were mild, with the most common being anxiety, nausea, insomnia and dry mouth. In an earlier study, at the highest dose level, 16.9% of participants discontinued due to adverse effects (AE), while only 9.7% of the placebo arm discontinued due to AE. This difference is not statistically significant. We can expect plenty of questions about AE on the call though.

I expect the NDA for Empatic to be submitted in 2011, about a year after the Contrave NDA, which puts an expected FDA decision for Empatic in 2012.

For anyone interested in the saga of weight gain caused by atypical antipsychotics (ok, me and whoever else): OREX also did a Phase I trial of zonisamide plus olanzapine. That’s the active ingredient in Eli Lilly & Co’s (NYSE:LLY) top-seller Zyprexa, which goes off-patent in 2011. OREX was evidently hoping for a "skinny Zyprexa" (my phrase, not theirs), but had to cut back the research due to funding pressures during 2009.

Disclosure: No positions

Source: What to Look for in Orexigen's Empatic Data Release