All but left for dead at $0.84 per share back in March, Immunomedics (NASDAQ:IMMU) is back with a bang. The stock climbed 60% Thursday after the company reported results from a phase 2 trial testing its epratuzumab drug in patients with lupus.

That mouthwatering six-month return may have gotten Immunomedics (back) on your radar screen, but I'd recommend treading lightly, Fools. Lupus is where drugs go to die, and epratuzumab is a drug that has already died a few times and come back to life.

Sure, epratuzumab could follow in the footsteps of Benlysta, from GlaxoSmithKline (NYSE:GSK) and Human Genome Sciences (NASDAQ:HGSI), and pass its phase 3 trial, but it could also stumble and end up where Biogen Idec (NASDAQ:BIIB), Teva Pharmaceutical (NASDAQ:TEVA), BioMarin Pharmaceuticals (NASDAQ:BMRN), and so many others have thrown their failed drugs.

Then again, epratuzumab seems to be an unkillable zombie, so maybe it would be right at home in the graveyard. In 2004, Amgen (NASDAQ:AMGN) gave Immunomedics back the rights to epratuzumab after a four-year partnership because Amgen didn't think it was worth running a phase 3 trial to test the drug in patients with non-Hodgkin's lymphoma. A few years later, the Food and Drug Administration put a hold on a lupus trial, since lifted, after a new partner, UCB, became worried about the sterility of epratuzumab made by Immunomedics.

If you've got a high risk tolerance, Immunomedics might be a reasonable bet still at this point -- it's down about 12% today. Its market cap is a fifth of Human Genome Sciences', which is also developing a lupus drug, so there's still plenty of upside, if the phase 3 trial is successful.

But that's still a big if.

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Fool contributor Brian Orelli, Ph.D., doesn't own shares of any company mentioned in this article. The Fool has a disclosure policy.