AEterna Zentaris Inc. President and Chief Executive officer David Mazzo has resigned, the company announced on Friday.

The biopharmaceutical firm that specializes on endocrine therapy and oncology said Mazzo was leaving the company immediately, not giving reason for the departure.

Juergen Ernst, the current Chairman, will be the interim president and chief executive officer until a replacement is found, the company said. Mazzo had been President and chief executive since April 9, 2007.

The Quebec City, Canad- based company also said its senior vice-president, business operations and chief business officer Ellen McDonald resigned, effective immediately.

Shares of AEterna Zentaris trading on the Toronto Stock Exchange fell 38 cents, or more than 21 percent to $1.41 at 11:13 a.m. EST. U.S. traded shares fell 23 percent.