Since bottoming out on March 23, 2020, the stock market has been virtually unstoppable. The widely followed S&P 500 took less than 17 months to double in value, marking the most robust rebound from a bear-market bottom in history.

But here's the kicker: Even with the market nipping at new all-time highs, there are still some serious values to be had, according to some Wall Street investment banks and analysts. If the high-water price target for each of the following five stocks were to come to fruition, shareholders would be looking at gains ranging from a low of 195% to as much as 467%.

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Plug Power: Implied upside of 195%

If you're "only" looking to triple your money, analyst Amit Dayal of H.C. Wainwright would suggest putting it to work in hydrogen fuel-cell solutions company Plug Power (PLUG 10.20%). Dayal's price target of $78 implies a cool 195% upside from where its shares closed this past weekend. 

The bull case for Plug Power has to do with the multidecade vehicle replacement cycle that lies ahead for consumers and enterprises. In an effort to fight climate change, alternative energy solutions, including hydrogen fuel cells, are becoming increasingly popular.

In January, Plug Power landed two significant partnerships, cementing its status as an alternative energy game-changer. SK Group took a 10% equity stake in Plug and plans to work with the company to roll out fuel cell-powered vehicles and hydrogen refilling stations throughout South Korea. Meanwhile, a joint venture with French automaker Renault will see the duo target Europe's light commercial vehicle market.

While there's no denying the opportunity on Plug Power's doorstep, let's not overlook that it isn't yet profitable. Also, ramping up production capacity isn't guaranteed to be without its hiccups. Plug is promising, for certain, but a $78 price target is probably asking a bit much.

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Zogenix: Implied upside of 319%

Small-cap biotech stock Zogenix (ZGNX) also offers some serious upside, according to Wall Street. With the loftiest price target calling for $62, Zogenix's shares could more than quadruple.

Optimism surrounding the company has to do with its U.S. Food and Drug Administration (FDA)-approved drug Fintepla, which is aimed at treating a variety of seizure-related ailments. It's already approved to treat Dravet syndrome, and Zogenix has plans to file a supplemental new drug application (sNDA) in the third quarter to expand Fintepla's label to include Lennox-Gastaut syndrome (LGS). If this sNDA is approved, commercial sales would commence as early as the first half of 2022. The rapid growth of Fintepla should make Zogenix one of the fastest-growing stocks on the planet, at least on a nominal basis, over the next three years.

However, growing sales of Fintepla won't be a cakewalk for Zogenix. That's because GW Pharmaceuticals, which was acquired by Jazz Pharmaceuticals in May, has a highly successful cannabinoid-based seizure-reducing therapy on pharmacy shelves. Epidiolex brought in almost $156 million in second-quarter sales and has had a longer runway to build up sales in Dravet and LGS than Fintepla. While there looks to be enough room for both companies to coexist, there's the potential for growing pains.

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Inovio Pharmaceuticals: Implied upside of 311%

Another stock receiving some serious love from Wall Street is clinical-stage biotech company Inovio Pharmaceuticals (INO 7.79%). Oppenheimer analyst Hartaj Singh believes Inovio's shares are worth $35, which implies an increase of 311% from where it closed last week.

Singh's lofty price target is mostly based on the expected success and near-term revenue generation potential of INO-4800, a coronavirus vaccine 2019 (COVID-19) treatment that's readying for a phase 3 global trial. With billions of people left to vaccinate, there's certainly room for a half-dozen or more major players to help with the inoculation and/or booster shot effort. Singh also believes VGX-3100, an experimental human papillomavirus treatment, could be a success for Inovio. 

One thing this company has never lacked is a robust portfolio of experimental candidates. Inovio currently lists 11 novel compounds in various stages of clinical-stage trials. What it has lacked is a successful late-stage study. At no point in the company's more than four decades since being formed has an Inovio-developed product hit pharmacy shelves.

What's more, regulators pumped the brakes on INO-4800 in the U.S., which is what forced the company to take its trial to international markets. A combination of partial clinical holds by the FDA and the pulling of all U.S. funding from Inovio's phase 3 study removed its chance to be an early COVID-19 vaccine winner. With this being said, it's probably best to take a wait-and-see approach with Inovio Pharmaceuticals.

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Intercept Pharmaceuticals: Implied upside of 467%

The crème de la crème of upside opportunities, at least on this list, is liver disease-focused biotech small-cap Intercept Pharmaceuticals (ICPT). Yasmeen Rahimi of Piper Sandler has an overweight rating and an $82 price target on Intercept. If accurate, this would entail 467% upside from where it closed this past week.

There's no sugarcoating that obeticholic acid (OCA) as a treatment for nonalcoholic steatohepatitis (NASH) will make or break Intercept. NASH affects 2% to 5% of the U.S. adult population, is an estimated $35 billion indication, and has no FDA-approved treatments currently on the market.

Intercept's lead drug did meet one of its two co-primary endpoints in the phase 3 Regenerate trial, with a statistically significant improvement in liver fibrosis without a worsening in NASH. However, the more effective higher dose also led to a notable uptick in trial participant withdrawals and a higher precedence of pruritus (itching), compared to the placebo. Intercept was given a Complete Response Letter on its first attempt to get OCA approved and intends to submit additional trial data in the hopes of reaching pharmacy shelves. Even if it were approved and used for only a small subset of NASH patients, it could offer billion-dollar annual sales potential.

In addition, OCA is approved by the FDA to treat primarily biliary cholangitis (PBC). This PBC indication could provide Intercept with $350 million-plus in annual sales. While the risk/reward profile of Intercept is favorable here, an $82 price target seems too lofty.

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Amarin: Implied upside of 259%

A fifth and final stock with significant implied upside is biotech stock Amarin (AMRN -0.94%). In addition to being extremely bullish on Intercept, Rahimi stuck to a $19 price target on Amarin, along with an overweight rating. This suggests a 259% upside may await patient shareholders.

Amarin is a popular drug developer that's certainly caught in a tug-of-war between optimists and pessimists. Last year, shares of the company imploded after Vascepa, an FDA-approved drug designed to lower cardiovascular event risk in combination with statins, had its exclusivity invalidated in the United States. This allowed generic-drug makers to enter the market with significantly lower-priced versions of Vascepa. 

On the other hand, Vascepa's patent is well protected in Europe for nearly another two decades, and the company will be launching its top-seller, known as Vazkepa overseas, in Germany and the U.K. this year. Plus, in spite of facing generic competition in the U.S. for eight months (through June 2021), Vascepa still maintained an 89% share of its market category.

The company also has $523 million in cash, cash equivalents, and long-term investments, compared to a meager $8.9 million in long-term lease liabilities and no outstanding debt. That's a quarter of the company's market value in cash, and the company effectively trading at 3 times sales. If Vazkepa takes off in Europe and Amarin pushes to recurring profitability, hitting a $19 price target is possible.