Arena Pharmaceuticals (NASDAQ:ARNA) is revving up for the launch of its obesity drug, Belviq. The drug was the first obesity drug approved earlier this year but got held back by DEA scheduling while rival Qsymia from VIVUS (NASDAQ:VVUS) made it to market.

The obesity wars have turned rather heated, with investors often weighing in on one side while lambasting the other. It's an easy fire to fuel since both drugs have proven fairly effective and have similar risk profiles. Still, the battle drums beat on...

But all this talk about the obesity war's victor overlooks one important question: What's next for Arena?

Puny pipeline potentials
When it comes to drug development, the safer bets are companies with moderate pipelines. Lean too far toward either end of the spectrum and the risks increase of having either overextension with too many drugs or over-reliance on one or two drugs. Drug development is a long, insanely costly process, and the chances of drugs making it to market from the human trials stage are estimated to be below 1 in 10.

VIVUS has one up on Arena in that it has a second drug on the market: erectile dysfunction treatment Stendra. On the pipeline front, Arena has a step up on VIVUS in that it actually has a pipeline beyond its obesity drug, but it isn't much of a victory. The company has two preclinical candidates hanging around -- one for autoimmune conditions such as rheumatoid arthritis, and the other for pain -- but that's about all that's worth mentioning in the "early" pipeline.

What classifies as later stage in Arena's puny pipeline  is APD811, a prostacyclin (IP) receptor agonist for the treatment of pulmonary arterial hypertension, or PAH. In October, Arena announced the initialization of a double-blind, multiple dose phase 1 study.

PAH market
PAH is a condition where the pulmonary arteries constrict severely, causing the heart to beat faster to get blood through arteries and elevating the blood pressure in the lungs. The condition is serious because the heart and lungs begin to weaken over time. Survival rates aren't high, with around 50% of those diagnosed with PAH dying within five years and an average lifespan for undiagnosed people of three years. PAH is incurable, so developed treatments are meant to manage the condition.

On the slim chance it makes it that far, Arena's drug wouldn't be the first PAH treatment on the market. Current treatments on the market include Letairis from Gilead (NASDAQ:GILD) and Tracleer from Actelion. Letairis brought in $293.4 million in 2011, a 20% year-over-year increase. Tracleer  brought in $1.52 billion Swiss francs last year, but it's losing market share thanks to the FDA removing a liver damage warning label requirement for Letairis. 

Money matters
Pushing drugs through the pipeline requires money. An additional influx of cash is needed if the drug actually makes it to the bright light of market, where it needs to land at a gallop.

Belviq is racing out of the gates with Japanese drug maker Eisai at the reins. As Foolish health care master Brian Orelli reported, Eisai got the U.S. rights for Belviq in 2010 for the pretty upfront price of $50 million. Eisai will eventually have the marketing rights to all of the North and South American territories for which the drug wins approval. Arena starts benefiting if Belviq becomes a blockbuster. Success will increase Arena's percentage of net sales and could potentially trigger up to $1.2 billion in milestone payments.

Arena's current reliance on Eisai combines with the meager pipeline to paint a less-than-rosy picture. If Belviq isn't a runaway success, Arena is going to be in deep trouble because it currently has nothing else to fall back on, and anything less than a stellar performance is going to be more of a win for Eisai.

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