August ushers in the end of the so-called "dog days of summer" when the temperatures are typically the highest throughout much of the U.S. But while the heat might not be quite as bad throughout this month, some stocks could just be getting warmed up.

That's especially the case in the biotech industry. We asked three of our Motley Fool contributors to pick three biotech stocks that could make you richer in August (and beyond). Here's why they chose Gilead Sciences (NASDAQ:GILD), Moderna (NASDAQ:MRNA), and Regeneron Pharmaceuticals (NASDAQ:REGN)

Test tube rack with increasingly higher levels of green liquid in each of the five test tubes and a green line with an arrow sloping upward in the background.

Image source: Getty Images.

An incredible bargain

Zhiyuan Sun (Gilead Sciences): Gilead Sciences is one of the cheapest biotech stocks out there. You can buy shares for just 3.4 times revenue and 9.6 times earnings. That's not to mention the company pays a solid dividend amounting to a yield of 4.06% per year to its shareholders. So what gives?

All good things must come to an end. For Gilead, the company's coronavirus treatment Veklury is increasingly becoming redundant due to the widespread availability of coronavirus vaccines. Gilead grew its revenue by 21% year over year to $6.2 billion in the second quarter. Excluding Veklury, however, revenue from its core HIV and HCV franchises only grew by 5%. The drug generated $829 million in sales in the quarter, and that could all go bust very soon.

Luckily, Gilead can count on its blockbuster drug Biktarvy. The drug has now become the No. 1 most prescribed HIV regimen in the U.S., with a revenue growth rate of 24% compared to the prior year's quarter. The company plans to expand its HIV franchise as well, seeking regulatory approval for its up-and-coming lenacapavir, which targets heavily treatment-experienced HIV patients with multi-drug resistance.

Aside from that, Gilead's subsidiary Kite Pharma recently announced that its drug Yescarta improved event-free survival by 60% over the standard of care plus stem cell transplant for patients with recurring large B-cell lymphoma.

Overall, the company has a solid franchise and pipeline. For the year, Gilead projects it can bring in up to $25 billion in revenue and $7.25 in earnings per share. Both reflect year-over-year increases. Gilead remains a solid stock with a cheap valuation that investors should add to their portfolios. 

Not just a coronavirus play

Prosper Junior Bakiny (Moderna): Moderna is still riding the wave of its COVID-19 vaccine, mRNA-1273, which it developed in record time last year. Shares of the company are up more than 230% year to date on the back of $1.7 billion in sales of mRNA-1273 in the first quarter. Moderna expects to record a total of at least $19.2 billion in revenue from its crown jewel this year, and given that the company has signed more supply agreements since making that projection,  it will likely revise it upward. 

Further, with COVID-19 infections on the rise -- and with the delta variant spreading like wildfire -- chances are high that booster shots will eventually come into play, even for those already fully vaccinated against the disease. Moderna's top and bottom lines would benefit from this scenario. The biotech's short-term prospects look bright, but investors shouldn't overlook its long-term prospects. 

mRNA-1273's smashing success has helped validate Moderna's master plan to develop a platform of mRNA-based vaccines for infectious diseases. Moderna's mRNA technology boasts several advantages, including the potential to speed up vaccine development time and the ability of just one vaccine to target multiple pathogens. Thanks to the revenue it will generate this year, Moderna will have the funds to develop other vaccines. And the opportunities are vast. 

There are no approved vaccines for several of the viruses Moderna is targeting, including the Zika virus and the cytomegalovirus. Moderna is also looking to develop a flu vaccine on the grounds that the current leaders in this market are only 40% to 60% effective. The more ambitious programs in the biotech's pipeline include a potential vaccine against HIV and others targeting several forms of cancer.

With all that said, investors shouldn't assume it will be smooth sailing for Moderna from here on out. Some of the company's programs may not pan out. Once its coronavirus tailwind comes to an end, the company's stock could suffer.

Still, in my view, Moderna's mRNA technology looks likely to earn some major clinical and regulatory victories in the next five years. This bodes well for the biotech's future, and even after crushing the market over the past year and a half, Moderna still looks like a buy. 

Firing on all cylinders

Keith Speights (Regeneron Pharmaceuticals): There aren't many big biotech companies that have as much going for them right now as Regeneron Pharmaceuticals. Sales for all six of the drugmaker's top-selling products continue to grow by double-digit percentages.

Regeneron's biggest moneymaker is its eye-disease drug Eylea. The company markets the drug in the U.S. on its own but partners with Bayer outside of the U.S. It also has partnerships in place for its other biggest-selling products.

Sanofi records the global sales of immunology drugs Dupixent and Kevzara but splits the profits with Regeneron. The French drugmaker also markets cancer drug Libtayo and cholesterol drug Praluent outside of the U.S.  

Regeneron markets its COVID-19 antibody therapy REGEN-COV on its own in the U.S. However, it teamed up with Roche to distribute the antibody cocktail in international markets. 

In addition to these current products with strong sales momentum, Regeneron's pipeline holds the potential to fuel even more growth. Most of the company's late-stage programs target additional indications for already approved drugs such as Dupixent and Libtayo. However, there are several earlier-stage candidates that are especially promising.

I'd put NTLA-2001 high on that list. Regeneron partnered with Intellia Therapeutics to develop the gene-editing therapy. The companies recently announced encouraging results from a phase 1 study of the experimental drug in treating rare genetic disease transthyretin (ATTR) amyloidosis. 

My view is that the increase in COVID-19 cases caused by the highly-contagious delta variant will continue to boost sales of REGEN-COV. I look for recent regulatory wins for Libtayo to drive increased sales of the cancer drug. Over the long term, I think that Regeneron's pipeline will pay off in a big way. This biotech stock, in my opinion, truly is one that could make investors richer in August and beyond.

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.