While Fools should generally take the opinion of Wall Street with a grain of salt, it's not a bad idea to take a closer look at particularly stock-shaking upgrades and downgrades -- just in case their reasoning behind the call makes sense.

What: Shares of Ariad Pharmaceuticals (NASDAQ:ARIA) popped more than 10% this morning after Chardan Capital upgraded the biotech from neutral to buy.

So what: Along with the upgrade, analyst Ling Wang planted a price target of $9 on the stock, representing about 40% worth of upside to Friday's close. The stock surged last week after the FDA OK'd the return of its leukemia treatment Iclusig to the U.S., but Wang believes there's plenty of room to run given the drug's untapped sales potential.

Now what: Chardan expects Ariad to generate Iclusig sales between $220 million and $240 million by 2019. "Iclusig updated label in the U.S. is much narrower than the original label," noted Chardan. "We expect physicians to largely reserve Iclusig in the refractory setting until patients progresses on all approved therapies in patients without T315I mutation, and potentially use Iclusig as a preferred second line therapy for patients with T315I mutation." More important, with the stock still a whopping 70% from its 52-week highs, biotech-savvy Fools (who are tolerant of plenty of risk) might have room to buy into that bullishness. 

Fool contributor Brian Pacampara has no position in any stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.