NEW YORK (TheStreet) -- Verastem (VSTM) - Get Report shares are down by 64.9% to $1.99 on Monday morning, after the biopharmaceutical company halted the study of its experimental cancer therapy.

The company announced that it is stopping a mid-stage study of VS-6063, Verastem's leading mesothelioma cancer treatment candidate, after studies showed that the treatment was not effective enough to warrant further studies.

"Malignant pleural mesothelioma is among the most aggressive and lethal cancers with only one approved therapy. With the aggressiveness of this disease, the use of single agent VS-6063 as a maintenance treatment following chemotherapy where all patients had residual disease was not sufficient," Interim Chief Medical Officer Lou Vaickus said in a statement.

"We are disappointed with the COMMAND outcome, but we are deeply grateful for the support and commitment from the patients participating in the study, their families, and the study investigators," CEO Robert Forrester added.

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