What happened

Shares of rare-disease specialist Amicus Therapeutics (FOLD 0.39%) are marching higher today. Specifically, the drugmaker's stock is up by 10% as of 12:45 p.m. EST. 

What's driving this double-digit rally today? The biotech's shares are jumping in response to a noteworthy upgrade from Cantor Fitzgerald's analyst Eliana Merle. The big-ticket item is that Merle's forward-looking price target of $20 per share implies a whopping 124% upside potential -- that is, relative to where the biotech's stock closed on Monday.  

Stacks of wooden blocks with upward-facing arrows on them grow taller as they move to the right.

Image source: Getty Images.

So what

Prior to today's hefty rally, Amicus' stock was clearly stuck in a rut. Weighed down by concerns over a rival Pompe disease treatment from French drug giant Sanofi and an already-rich valuation, Amicus' stock had been slowly losing ground since the end of the first quarter of 2019. In short, investors were growing increasingly concerned that Amicus' sky-high valuation may not be justified. Cantor, for its part, apparently doesn't think the biotech's eye-popping price-to-sales ratio of 15.7 is a problem in the least. 

Now what

Is it time to buy? Amicus' experimental Pompe disease treatment known as AT-GAA could one day generate upwards of $2 billion in sales. So, if that line holds true, the biotech's stock should not only double from current levels, but it could easily triple in value within a few short years. As such, it might indeed be worthwhile to take a flier on this top orphan drug stock on the heels of this overwhelmingly positive analyst upgrade.