Healthcare stocks have a rich history of churning out big winners. The sector has been a hotbed of innovation over the past decade, leading to breakthrough treatments for a variety of hard-to-treat cancers, rare diseases, and chronic illnesses like arthritis and diabetes, among many others. 

Which healthcare stocks could be the next to make explosive moves higher thanks to groundbreaking innovations? Aprea Therapeutics (NASDAQ:APRE), Viking Therapeutics (NASDAQ:VKTX), and Vaxart (NASDAQ:VXRT) each sport clinical-stage assets capable of being major growth drivers in the years to come. Here's why these three risky biotech stocks may deserve a spot in your portfolio. 

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Aprea: On the cusp of a major binary event

Aprea is a small-cap cancer specialist racing toward a late-stage readout for its lead product candidate APR-246 (eprenetapopt). APR-246 is a small molecule p53 reactivator, which is a novel therapeutic pathway that may enhance apoptosis (programmed cell death) in numerous types of cancer cells.

The drug is currently being evaluated, in combination with chemotherapy, as a first-line treatment for TP53 mutant myelodysplastic syndromes (MDS). TP53 MDS is a rare but severe form of bone marrow cancer. Patients with TP53 MDS presently have few viable treatment options. Aprea expects to announce top-line data from this ongoing trial for APR-246 before year-end. 

The big deal is that this first indication for APR-246 could be worth hundreds of millions in annual sales. That's a healthy revenue projection for a biopharma company with a market cap of less than $530 million at present. 

Aprea's upcoming data release could thus cause its stock to jump in a big way in the coming weeks. That said, cancer drugs more often than not fail to hit the mark in their late-stage programs. Investors, in turn, arguably shouldn't risk more than they can afford to lose on this clinical-stage biotech stock. 

Viking: A wide-open opportunity in NASH

Non-alcoholic steatohepatitis, or NASH for short, is a severe type of fatty liver disease. This increasingly common ailment is initially characterized by inflammation of the liver, which can then progress into more serious tissue changes including fibrosis and cirrhosis.

Unfortunately, there are no approved treatments for this potentially deadly disease. While several pharma companies have attempted to crack this untapped drug market, the most advanced experimental compounds have all either missed the mark in late-stage clinical trials or failed to win over regulators

Viking Therapeutics, a clinical-stage biotech, is therefore staring down a possible multi-billion dollar commercial opportunity with its midstage NASH candidate known as VK2809. The intrigue over VK2809's utility as a potent NASH treatment stems from a prior midstage trial, where the drug produced a statistically significant 45% median reduction in liver fat content among patients at week 16.

Viking is currently assessing the drug in a second midstage trial specifically for biopsy-confirmed NASH. Top-line data from this ongoing NASH trial should be available for public consumption sometime in the second half of 2021

Why should investors sit up and take notice? Viking has a market cap of $460 million at the moment. VK2809, by contrast, stands a realistic shot at generating several billion in annual sales as one of the first NASH treatments on the market.

Of course, the drug still has to find success where so many others have failed. But there's no doubt that this small-cap biotech has the potential to rapidly morph into a large cap drugmaker by the middle of the decade.      

Vaxart: An attractive COVID-19 play

Vaxart's stock started 2020 off on an absolute tear, thanks to the company's entrance into the COVID-19 vaccine game. The company's unique solution to the pandemic is an orally administered vaccine known as VXA-CoV2-1.

VXA-CoV2-1 does not require cold storage or specialized equipment to administer, thus allowing it to be distributed globally with relative ease. Vaxart's oral COVID-19 vaccine, in effect, offers notable logistical advantages compared to more traditional injectables. 

The only problem is that the biotech's COVID-19 vaccine candidate is several months behind the leaders in the space in terms of clinical development. There are already three late-stage vaccine candidates with 90% efficacy rates, after all.

What's more, the biotech is facing a slew of legal issues over the wording of a press release regarding its involvement in the Operation Warp Speed program. These two key headwinds -- the latecomer status of its vaccine and the various legal proceedings -- have weighed heavily on the biotech's shares over the past several weeks. 

Vaxart, though, may yet find a profitable niche with VXA-CoV2-1. This early-stage oral vaccine could solve a host of commercial and logistical issues swirling around the first tier of injected vaccines.

So, if this novel COVID-19 vaccine can indeed pass muster in its clinical program, Vaxart's shares should regain their footing over the course of 2021. That said, this is a super risky developmental biotech stock -- a fact that potential investors shouldn't take lightly.     

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.