What: Shares of Arena Pharmaceuticals (NASDAQ:ARNA), a biopharmaceutical company primarily focused on the development of weight control management products, sank as much as 10% on Thursday after the company announced its second-quarter earnings results.

So what: For the quarter, Arena's revenue sank by 28% to $9.18 million from the $12.8 million it reported in the year-ago quarter. Although net product sale revenue recognition for weight control management drug Belviq rose to $4.29 million from $3.53 million in Q2 2014, collaborative revenue from Belviq's licensing partner Eisai dropped $5.3 million.

In terms of sales growth for Belviq, IMS Health estimated that in the neighborhood of 183,000 prescriptions for Belviq were filled during the quarter, which would represent 66% year-over-year script growth and nearly 9% sequential quarterly growth.

Net loss for the quarter was $26.8 million, a saddening reversal from the $7.5 million profit recorded in the year-ago quarter. On an EPS basis, Arena lost $0.11 compared to a profit of $0.03 in Q2 2014.

Comparatively speaking, Wall Street had been expecting a wider loss of $0.14 per share, but it had also been expecting more robust revenue of $10.9 million.

Source: Arena Pharmaceuticals.

Now what: Although Arena Pharmaceuticals' other pipeline products have demonstrated early stage promise -- APD334, for instance, demonstrated a dose-dependent lowering of lymphocyte counts in patients' blood of up to 69% in a phase 1b study -- the cement block tied to its metaphorical ankles is the disappointment of Belviq.

Belviq was expected to be a potential blockbuster drug considering that more than a third of adult Americans are considered obese based on the Body Mass Index. However, things haven't panned out. Whether it's a concern on physicians' part over the long-term safety of weight control management drugs, increased competition, or the struggles of gaining insurer coverage, Belviq has failed to generate substantial revenue and is looking more like a flop with each passing quarter.

My suggestion would be to avoid this stock until it has successfully brought other products to market and dramatically lowers its cash burn rate.