On Monday, Immunomedics (NASDAQ:IMMU) announced it was halting its successful phase 3 study of sacituzumab govitecan as a treatment for triple-negative breast cancer, on the advice of its Data Safety Monitoring Committee (DSMC).

"Triple-negative breast cancer (TNBC) is a disease with extremely limited treatment options beyond classic chemotherapy," said the chairperson of the committee, Julie Gralow, a professor at the University of Washington School of Medicine. "The remarkable results we observed across multiple endpoints in the ASCENT study warranted early discontinuation of the trial and are indicative of a potential major advance in the treatment of this devastating disease."

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Sacituzumab govitecan, Immunomedics' lead treatment candidate, has been highly sought after for several years now. Seattle Genetics tried to acquire the rights to the drug in 2017. In fact, a deal was made, which caused such consternation at venBio Select Advisor -- a major investor in Immunomedics -- that the hedge fund launched a proxy fight for control of the company. It won, venBio managing partner Behzad Aghazadeh became the chairman of Immunomedics' board, and the company retained the rights to the molecule.

Aghazadeh is now the executive chairman of Immunomedics. "Today's announcement marks a significant milestone toward fulfilling our promise to patients globally with TNBC of providing a new treatment option that can meaningfully improve their lives," he said Monday. "We are grateful to all the patients, their families and healthcare providers who participated in the ASCENT study. On behalf of all of my colleagues at Immunomedics, we remain committed to working tirelessly to bring this potentially transformative drug to all mTNBC patients in need."

As of 11:15 a.m. Monday, the stock was up 99%.