The "price of entry" for a buyout is not always reflected in the market price of the stock. This is corporate finance 101, but to buy a public company you must first convince an overwhelming majority of the company's shareholders to sell, and, where a company has a substantial percentage of its stock in the hands of management and institutions, that must be done through negotiations rather than market purchases.
There is no reason to believe that the recent low share price (which occurred on very low volume while short positions were rising by the way) would in any way influence management's view of the value of the company. Arena is well funded for the immediate future and is making satisfactory progress in growing Belviq sales. There is no pressure on Arena management to find a buyer.
As counter-intuitive as it may seem, the possibility of a buyout will increase once Belviq meets some important goals, such as EU approval and hitting sales targets for the first and second year, even though this will naturally increase the market price. This is partly due to the fact that the buyer's management will not be putting their own company at risk to a fiasco (which is often career ending) which happens when a premium is paid for stock which then collapses. Longs may not be happy to hear this, but today Arena is not a sure thing in the eyes of all potential buyers.
This board should be wary of pumper articles designed to create enthusiasm for far fetched events whose true purpose is to snag shares from disappointed retail investors by shorts who need to cover. This is probably one of such attempts.