Among the biggest winners in Thursday’s early trading are Arena Pharma (Nasdaq: ARNA), Clean Energy (Nasdaq: CLNE) and West Marine (Nasdaq: WMAR).

Arena’s Bull Run

Shares of Arena Pharmaceuticals (Nasdaq: ARNA) continue to ascend, rising another +12% on Thursday, good for a +50% gain during the past three weeks. We first told you of Arena’s promising anti-obesity drug in early July.

Today’s gains are due to a rising perception that Arena’s drug is more promising than those of rivals Oreixigen (Nasdaq: OREX) and VIVUS (Nasdaq: VVUS). And investors are starting to realize that if Arena can capture a big part of this market, then it stands to reap massive sums of money from marketing partner Eisai.

Action to Take –> Even with the recent run, shares still trade for less than half of the potential total value of the Eisai relationship — and that’s just for the United States. If and when Arena inks a foreign partner, shares could spike even higher.

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Clean Energy’s Legislative Hopes

Shares of Clean Energy (Nasdaq: CLNE) are rising +12% on hopes that imminent Congressional legislation will provide incentives to adopt natural gas as a transportation fuel source. Clean Energy operates a network of natural gas fueling stations, primarily to fleet operators.

#-ad_banner-#Last week, we opined that Clean Energy would get a lift from any government-related initiatives to jump-start the industry.

Senate Democrats reportedly plan to unveil the energy bill next week. Senator Reid (D-NV) will attempt to begin debate on the bill the week of July 26. But they’ve got a short window. The Senate is scheduled to begin a month-long summer recess on Aug. 6.

Action to Take –> Shares of Clean Energy have spiked and slumped as the prospects for Federal legislation have waxed and waned. In the absence of any support, Clean Energy may struggle to meet aggressive 2011 sales and profit forecasts. As of now, analysts anticipate that the industry will get government support, and that the company will be in the black for the first time in its history in 2011. If legislation is passed, shares would quickly move into the $20s.

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West Marine’s Rebound

Any boat owner can tell you that this leisure industry has been dead for several years. Boat sellers have found few buyers, and many boaters have opted to simply keep their boats out of the water to save money. But the industry is springing back to life recently as boat sales rise and marina slips fill up once again. That notion was underscored by surprisingly strong quarterly results from West Marine (Nasdaq: WMAR), which operates a nationwide chain of stores and an eponymous catalog catering to boat owners.

West Marine announced an +8.4% jump in same-store sales in its fiscal first quarter ended in April (though that’s less than timely as we are already near the end of the next quarter). After three straight years of falling sales, analysts generally stopped following this retailer, so it’s unclear where these results were relative to expectations. But fund managers and other investors have certainly anticipated the rebound, pushing shares up nearly threefold during the past 18 months. If West Marine can maintain this sales momentum, it should be able to post solid profits thanks to heavy cost cuts. In 2009, West Marine posted its first profit since 2005, even though sales fell another -7%.

Action to Take –> By my rough math, West Marine could earn $1 a share this year as the company is now in its seasonally most profitable quarters. Shares, despite today’s +6% gain, could have further upside — if the U.S. economy can start to build a head of steam. This is a very economically sensitive sector, and West Marine appears positioned to thrive during the good times.