Biotechnology stocks can pop or drop because of clinical trial successes or failures, and that makes investing in biotech stocks riskier than investing in other industries. Nevertheless, the rewards for those biotech companies that successfully innovate new therapies can be significant, and that makes stocks like Regenxbio (RGNX 1.49%), Regeneron Pharmaceuticals (REGN -0.89%), and AbbVie (ABBV -4.76%) worth considering. Read on to learn more about these companies and why some of our Motley Fools think they could be top stocks to add to portfolios this month.

This gene therapy stock could be onto something big

Todd Campbell (Regenxbio): If you're willing to take on some risk in your growth portfolio, then you might want to consider Regenxbio, a clinical-stage biotech working on a novel approach that could make gene therapy safer and more effective.

Gold and silver pills spill out of a gold and silver capsule onto $20 bills.

IMAGE SOURCE: GETTY IMAGES.

Many diseases are the result of genes working incorrectly, so researchers are developing therapies that tinker with genes to correct their function.

Delivering gene therapies to their proper place requires the use of inactivated viruses; however, these viral vectors can be tough to manufacture, and there's concern that they won't produce durable responses. There's also worry they'll cause immune system responses that lead to adverse events.

To overcome those concerns, Regenxbio has developed its NAV technology, a platform consisting of over 100 adeno-associated viral vectors it believes can deliver gene therapy payloads better than other viral vectors.

The company is using its NAV technology platform to develop its own gene therapies, and it's licensing its vectors to other companies in exchange for upfront payments, milestones, and hopefully, royalties.

The most advanced gene therapy in development that's using Regenxbio's technology is AVXS-101, a one-and-done gene therapy for spinal muscular atrophy (SMA), a devastating disease. Earlier this year, Novartis spent $8.7 billion acquiring AveXis to land AVXS-101, and depending on data, Novartis plans to file for FDA approval of AVXS-101 before the end of 2018.

If AVXS-101 is successful, it could move the needle for Regenxbio, but investors will also want to be on the look out later this year for top-line data from trials of Regenxbio's RGX-314, a gene therapy for wet-AMD, and RGX-501, a gene therapy for an inherited form of high cholesterol called homozygous familial hypercholesterolemia (HoFH). Wet-AMD and HoFH are blockbuster indications that these gene therapies could significantly reshape.

Make no mistake, though. This is a high-risk stock. Its revenue consists solely of partnership payments right now, it doesn't have any commercially approved therapies on the market, and there's a chance its studies fail. For this reason, Regenxbio is only suitable for aggressive investors who can withstand disappointment.

The price is right

Brian Feroldi (Regeneron Pharmaceuticals): Once upon a time, Regeneron Pharmaceuticals was a red-hot growth stock that could do no wrong. Unfortunately, a series of events have since caused the tides to turn. This former market-darling has badly underperformed the S&P 500 over the last three years as investors have been forced to make downward adjustments to their growth expectations.

SPY Chart

SPY data by YCharts.

While the last few years have been quite trying for investors, I think there are finally reasons to believe that the company's future is starting to look bright. Eylea remains a megablockbuster drug that is still posting strong sales growth. Sales of cholesterol-busting drug Praluent might finally be poised to show meaningful sales growth now that Regernson has proven more willing to negotiate with payers on price. At the same time, eczema drug Dupixent is off to a decent start and could get a major boost if it wins FDA approval as a treatment for asthma. 

When adding in the fact that Regeneron boasts 17 programs in late-stage clinical development -- some of which hold blockbuster potential -- market watchers expect the company's profits will grow in excess of 11% annually over the next five years. While that's a far slower rate than what the company has put up in the past, it's still quite good for a company that is currently trading for less than 17 times next year's earnings estimates. 

Three scientists collaborate together in a lab.

IMAGE SOURCE: GETTY IMAGES.

What's not to like with this biotech stock?

Keith Speights (AbbVie): There are few stocks on the market that can appeal to every kind of investor, but I think one big biotech stock just might: AbbVie.

Let's start with why income investors should like the stock. Most biotechs don't pay dividends, but AbbVie does. Its dividend currently yields more than 4%. And AbbVie has boosted its dividend payout by a whopping 140% over the last five years. 

What about value investors? AbbVie stock trades at only 10.4 times expected earnings. That's dirt-cheap for a company with the world's best-selling drug and a stable of other strong performers.

Of course, most biotech investors are looking for growth. AbbVie checks the box there, too. Analysts project that AbbVie will grow its annual earnings by nearly 17% on average over the next five years. The company has one of the fastest-growing cancer drugs with Imbruvica. It launched a new hepatitis C drug, Mayvyret, last year that's well on its way to blockbuster status.

Then there's AbbVie's pipeline. Market research firm EvaluatePharma ranked it as the second-best pipeline in the biopharmaceutical industry. AbbVie could have several big winners on the way, including endometriosis drug elagolix and autoimmune disease drugs risankizumab and upadacitinib.

Great dividends, attractive valuation, and strong growth prospects. What's not to like about AbbVie?