2 Ultra-High-Growth Biotech Stocks to Buy Now

Buying biotech stocks in May is rarely a good idea. This class of equities, after all, tends to fade in a big way around this time year. However, there are some outstanding exceptions to this general rule of thumb.

For instance, Amicus Therapeutics (NASDAQ: FOLD) and Array BioPharma (NASDAQ: ARRY) are two biotech stocks poised to continue churning higher -- even during this historically weak period of the year for the industry as a whole. Here's why investors might want to add these two top growth stocks to their portfolios soon.

Amicus: A top orphan-drug specialist

From an investing standpoint, rare-disease drugs can be worth their weight in gold. So-called orphan drugs come with a built-in seven-year period of market exclusivity, a premium pricing structure, and many of these products face little to no competition from rival therapies -- at least outside of orphan cancer indications. As a result, companies that specialize in this field tend to generate market-crushing returns on capital for early-bird investors. Amicus Therapeutics, a mid-cap rare-disease drugmaker, appears to have the pieces in place to be the next company to follow this powerful trend.

Amicus' story centers around its Fabry disease drug Galafold. At its current trajectory, the company thinks Galafold will reach $500 million in sales as soon as 2023 and perhaps over $1 billion by 2028. Put simply, Amicus appears to have a true franchise-level drug capable of driving its growth for the better part of the next decade. However, the biotech also has a high-value Pompe disease candidate known as AT-GAA in development, as well as an intriguing gene-therapy platform that could prove to be a game changer for a number of orphan indications.

Now, the company did recently announce a $150 million public offering to shore up its balance sheet and advance its gene therapy platform into the next stage of its life cycle. And that's not sitting particularly well with shareholders based on the initial reaction to this news (shares fell 5% in after-hours trading yesterday). But a longer-term view of this stock strongly suggests that this public offering will ultimately be a value-creating event. Thus, investors might want to take advantage of this weakness to pick up some shares soon.

Array: An emerging cancer treatment play

Cancer is easily the largest pharmaceutical market in terms of annual sales. Even so, this massive market also happens to be the fastest growing as well, thanks to the combination of novel treatments opening up new segments of the space and the ever-rising incidence rate for most malignancies across the globe. As a result, companies that successfully navigate the risky clinical trials process to bring a well-differentiated oncology treatment to market tend to be highly coveted by investors. Array BioPharma fits into this mold to perfection.

Last year, the Food and Drug Administration (FDA) approved its advanced BRAF-mutant melanoma combo treatment consisting of Braftovi and Mektovi. Since launch, this unique combination therapy has quickly become an important new weapon in the battle against BRAF-mutated skin cancer. As proof, Array reported $35.1 million in net sales during the most recent quarter. That's an impressive haul for a drug that hasn't even been on the market for a full year yet. Array thinks this first indication could eventually push the therapy's sales close to blockbuster territory (> $1 billion per year), although Wall Street largely thinks the drug will ultimately top out at around $500 million.

Array, though, has even bigger plans for its first major cancer treatment. The company recently reported positive late-stage results for Braftovi and Mektovi -- when used in conjunction with another compound called Erbitux -- in patients with BRAF-mutated colorectal cancer. The FDA has already granted this triplet therapy breakthrough therapy designation, which should shorten its review time to roughly half a year. So, with Array on track to file a supplemental New Drug Application in the second half of this year for this unique triplet regimen, the company could see a sizable jump in its top line in 2020 and beyond. Backing this assertion, EvaluatePharma, a top industry analytics firm, has the combo's peak sales for advanced colorectal cancer pegged at approximately $700 million.

All told, this promising cancer treatment stock should have a lot more room to run based on the healthy commercial prospects for its flagship therapy -- not to mention the fact that Array also has a fairly robust pipeline outside of Braftovi and Mektovi.

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George Budwell has no position in any of the stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. The Motley Fool has a disclosure policy.