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 Clovis Oncology Inc (NASDAQ:CLVS) surged 7% today after Stifel upgraded the biopharmaceutical company from hold to buy.

So what: Along with the upgrade, analyst Brian Klein planted a price target of $50 on the stock, representing 30% worth of upside to yesterday's close. So while momentum traders might be turned off by Clovis' sharp price decline in recent months, Klein's call could reflect a sense on Wall Street that its pipeline prospects are just too cheap to pass up.

Now what: According to Stifel, Clovis' risk/reward trade-off is rather attractive at this point. "Following the significant pull-back of ~60% from recent highs, we believe Clovis now presents with significant upside potential based on clinical and commercial prospects for CO-1686 in second-line EGFR-mutant NSCLC with T790M mutation," said Klein. "While we still remain conservative on approval timing and potential in earlier-stage disease, and note safety/tolerability concerns (particularly hyperglycemia), we view '1686 as a compelling and commercially viable, clinical candidate." So while Clovis remains just too speculative for average Fools, biotech-savvy contrarians might want to follow Stifel's lead.

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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.