What's Happening: After releasing positive clinical data at the end of May, ImmunoGen's (NASDAQ:IMGN) shares have been soaring higher, including a 15% jump earlier today.

Investor enthusiasm stems from reports last month that 53% of 17 heavily pre-treated ovarian cancer patients taking ImmunoGen's IMGN853 responded to it.

Despite the small size of the trial, ImmunoGen's shares soared 65% the day of clinical data was released, and with today's move, ImmunoGen's shares have now jumped 86% since May and 174% since December.

Why It's Happening: Investors are eager to see the company develop another source of revenue following the sale of some of its Kadcyla royalty stream to TSP Special Situations Partners for $200 million earlier this year. 

Ultimately, the sale of those rights is funding ImmunoGen's R&D effort, including a mid-stage study to validate its IMGN853 early-stage results.

If IMGN853's efficacy is backed up by this next trial, then there's a possibility that those results could form the basis for a filing with the FDA. Typically, a phase 3 trial would be necessary; however, advanced ovarian cancer patients' significant unmet need for new treatment options could accelerate the FDA's usual timeline. ImmunoGen estimates that between 2,000 and 3,000 of the 14,200 ovarian cancer patients who die annually from ovarian cancer could potentially benefit from this therapy.

Although IMGN853 could end up offering new hope to many patients who have seen their disease return following other treatment, investors do need to remember that there's no guarantee that ImmunoGen's future trials of IMGN853 will pan out. Historically, 93% of cancer drugs that enter human trials fail to make it to market, and 60% of drugs that enter phase 2 end up in the waste basket, rather than on pharmacy shelves. 

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