Bavarian Nordic saw its shares plummet as much as 50 percent in the wake of news that the firm’s cancer immunotherapy ProstVac failed to prolong survival in men with a particular type of prostate cancer.

The company announced the termination of the Phase III PROSPECT trial, which was assessing the drug in patients with metastatic castration-resistant prostate cancer (mCRPC), after an independent Data Monitoring Committee determined that it would be "futile" to continue based on an interim analysis of data.

“We are extremely disappointed for patients that this study of PROSTVAC as monotherapy was not successful,” said company president and chief executive Paul Chaplin. “While this is certainly not the desired outcome, we remain steadfast believers in the power of combination treatments, including immunotherapies, to transform the future of cancer therapies.”

ProstVac (rilimogene galvacirepvec/rilimogene glafolivec, or “rilimogene”) is a prostate specific antigen (PSA)-targeted immunotherapy candidate designed to enhance or stimulate the body’s immune response, specifically T cells that identify and kill prostate cancer cells.

The therapy is being developed in collaboration with the National Cancer Institute under a Cooperative Research and Development Agreement.