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.

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.