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 Progenics Pharmaceuticals (NASDAQ:PGNX) were up this morning after Needham & Company upgraded the biotechnology company to buy from hold.

So what: Along with the upgrade, analyst Chad Messer, Ph.D. planted a price target of $8 on the stock, representing about 67% worth of upside to Friday's close. While investors might be turned off by last week's bit of very bad news -- an abstract revealed the death of two patients during mid-stage trials of its experimental prostate cancer antibody-drug conjugate, PSMA-ADC -- Messer thinks that Progenics is too juicy to pass up given the positive data it presented at the American Society of Clinical Oncology GU Cancers Symposium.

Now what: According to Needham, Progenics' risk/reward trade-off is pretty attractive at this point. "Progenics presented positive data from two Phase II studies at ASCO-GU, including one from a PSMA-ADC therapeutics agent and a PSMA imaging agent," Messer noted. "We believe that these data validate the company's strategy of refocusing resources on cancer and making a big investment in the novel prostate cancer target PSMA. In particular, we believe the imaging agent could progress rapidly into Phase III testing and become a near-term value driver for PGNX shares." So while PSMA's toxicity concerns make Progenics far too risky for average investors, biotech-savvy contrarians might want to take a closer look at Needham's turnaround call.