Arena Pharmaceuticals' (NASDAQ:ARNA) shareholders -- and those who short the stock, for that matter -- are anxiously awaiting the launch of the company's obesity drug Belviq. The Food and Drug Administration approved the drug back in June, but the biotech and its marketing partner Eisai can't launch until the Drug Enforcement Agency decides its potential for abuse.

Meanwhile, Arena isn't sitting around doing nothing. Earlier this month, the company said it's starting a phase 1 trial testing a new drug, APD334, in healthy adult volunteers. A phase 1 trial isn't going to produce data that will move the share price, but it's a necessary step toward that end.

APD334 targets the sphingosine 1-phosphate subtype 1 receptor, which is involved in numerous autoimmune diseases, including multiple sclerosis, psoriasis, and rheumatoid arthritis. All three diseases are large markets with multiple blockbuster drugs treating them. Biogen Idec (NASDAQ:BIIB), for instance, has two multiple sclerosis drugs -- Avonex and Tysabri -- that are both blockbusters. AbbVie's (NYSE:ABBV) Humira, which treats both psoriasis and rheumatoid arthritis, posted sales of more than $9.2 billion last year.

Blockbuster obesity drugs have been a long time coming. If APD334 works in phase 2 and phase 3 trials, it's a clearer pathway to billion-dollar annual sales than the huge-but-unproven obesity market.

The rest of the pipeline
APD334 isn't the only drug Arena is working on. The company is focused on G protein-coupled receptors, which are involved in a wide variety of diseases, including 5-HT2C that Belviq targets and the S1P1 receptor that APD334 targets.

APD811, which targets the prostacyclin receptor, is being tested for patients with pulmonary arterial hypertension, or high blood pressure in the arteries that carry blood from the heart to the lungs. The company has completed phase 1 dosing of ADP811 in healthy volunteers, but plans to run another cohort of subjects to get the dose right before initiating a phase 2 trial.

Temanogrel is in the same boat. Arena has already run one phase 1 trial, but plans to run another phase 1 trial because the maximum tolerated dose wasn't reached in the first trial. Arena has licensed temanogrel to Ildong Pharmaceutical, which is responsible for funding the second phase 1 trial and the phase 2a trial in patients with serious thrombotic diseases including heart attacks, acute coronary syndrome, and stroke. 

Arena also has a few preclinical compounds targeting other G protein-coupled receptors.

Progress, but...
I'm impressed with Arena's progress. Compare it to a company like Onyx Pharmaceuticals, which for years insisted that Nexavar was sufficient for survival, only to eventually change its tune and acquire an external pipeline.

But in the short term, Arena is still highly dependent on Belviq. The biotech has a market cap of $1.8 billion; a company with three phase 1 compounds is only worth a tenth of that. It remains to be seen whether Arena and Eisai can compete with VIVUS' Qsymia, which produces greater weight loss but with potential for more severe side effects.

At least Arena has a backup plan.

Fool contributor Brian Orelli has no position in any stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.