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Mirna Therapeutics Inc. (NASDAQ: MIRN) shares got crushed on Wednesday after the company halted an early-phase trial. The ongoing Phase 1 study of MRX34 as a microRNA therapy for multiple cancers is being closed. Effectively, this pushed shares to hit an all-time low, although they have only been trading just under a year.

Essentially, Mirna voluntarily halted enrollment and dosing in the clinical study following multiple immune-related severe adverse events observed in patients dosed with MRX34 over the course of the trial.

At the same time, the company also announced that it will not be initiating a translational medicine study of MRX34 in melanoma patients, planned to begin later this year. Mirna will be further analyzing its full preclinical and clinical data set and will discuss with its advisors, as well as the FDA, possible future development of MRX34 and will provide updates when appropriate.

Paul Lammers, M.D., M.Sc., president and CEO of Mirna, commented:

Patient safety is the primary objective of our MRX34 Phase 1 clinical trial. We made the difficult decision to close the study after a fifth, immune-related serious adverse event was recently reported by one of our clinical sites. This patient experienced severe (Grade 4) cytokine release syndrome and is undergoing treatment. We have notified the U.S. FDA and the Korean FDA of our decision and are in the process of closing the trial.

Even excluding Wednesday’s move, Mirna had vastly underperformed the broad markets, with the stock down about 61% year to date.

Shares of Mirna were last trading down more than 23% at $1.88, with a consensus analyst price target of $7.38 and a 52-week trading range of $1.83 to $11.01.