The stock market has been on a tear for nearly a decade, emerging from the financial crisis in 2009 to post strong gains. The past year has been a particularly good one, with markets rising double-digit percentages and setting new records repeatedly.

Yet some stocks have managed to produce life-changing wealth in a relatively short period of time. In particular, a select handful of stocks has risen enough to turn an initial $8,000 investment into more than $40,000 in just a single year. Today, we'll look at Nektar Therapeutics (NASDAQ:NKTR), Weight Watchers International (NYSE:WTW), and Straight Path Communications (NYSEMKT:STRP) to see how they produced such strong returns, and what's next for these companies.

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Nektar gets great news from its drug pipeline

Biotechnology company Nektar Therapeutics managed to post gains of almost 545% over the past year, turning an initial $8,000 investment into more than $51,000. A huge portion of the rise in Nektar's stock price came last November, when the company got good news on multiple fronts. Its third-quarter earnings report included an upfront payment from partner Eli Lilly on the autoimmune disease therapy NKTR-358, and Nektar also said that it would file for approval with the U.S. Food and Drug Administration for its NKTR-181 mu-opioid receptor agonist. Favorable study results with its NKTR-214 cancer fighter also lifted Nektar's prospects, spurring a collaboration with Bristol-Myers Squibb that included a $1 billion upfront payment and another $850 million in equity investment.

Nektar has a lot of potential for further gains, especially as interest rises in its pain and cancer treatments. The company has the ability to collect a substantial amount from milestone payments in the future, and continuing research activity holds promise for new treatments as well. With encouraging study results on multiple fronts, things still look good for Nektar.

Box of fruit labeled with the Weight Watchers logo

Image source: Weight Watchers International.

One number Weight Watchers wants to go up

Most customers of Weight Watchers International focus on reducing weight numbers, but the weight-loss specialist has its eye on fattening up its investors' wallets with higher share prices. The arrival of Oprah Winfrey as a major shareholder and board member has raised awareness of Weight Watchers, and that's clearly been a factor in driving the value of a $8,000 investment a year ago to more than $44,000 today.

But Weight Watchers is far from content with its progress so far. In early February, the company said that it wants to achieve 50% sales growth between now and 2020, topping the $2 billion mark in revenue. With a goal of helping 10 million people be healthier, Weight Watchers thinks that it can both serve the public interest and grow its business. And consumer-conscious moves like removing artificial ingredients from its food products could help Weight Watchers make further gains in the years to come.

Straight Path reaches the end

Finally, Straight Path Communications has been a big success story for investors. Most of the stock's gains over the past year came early on, when a bidding war for its lucrative wireless spectrum assets arose between the two largest players in the U.S. wireless telecom industry. Eventually, Verizon emerged victorious, with a final bid that nearly doubled its rival's initial offer. That helped set the stage for a performance that turned an $8,000 investment a year ago into almost $43,000 today.

Alas, further gains won't be possible for Straight Path, because the deal with Verizon finally closed today. Under the deal, Straight Path shareholders can take their cash proceeds and do whatever they want with it, perhaps choosing to invest elsewhere in wireless telecom, or going outside the industry to more lucrative opportunities elsewhere.

One of the best things about the stock market is that outsized returns like these are always possible. You won't always be able to find the same gains that Straight Path, Weight Watchers, and Nektar produced. But over time, rising share prices can take you much closer to your financial goals, if you find high-quality companies with the potential for greatness.

Dan Caplinger has no position in any of the stocks mentioned. The Motley Fool owns shares of and recommends Verizon Communications. The Motley Fool has a disclosure policy.