13. RESTRUCTURING CHARGES

In September 2016, we announced that we had reduced our workforce by 46 positions, mostly in the research area.  We also announced that effective September 15, 2016, Donald G. Payan, M.D, has retired from the board of directors and from his position as Executive Vice President and President of Discovery and Research. We recorded restructuring charges during the three months ended September 30, 2016 of approximately $5.8 million within Restructuring Charges in the accompanying Statement of Operations, which included $5.0 million of severance costs paid in cash, $319,000 impairment of certain property and equipment, and $499,000 of non-cash stock-based compensation expense as a result of the modification of our former executive’s stock options (see Note 6). At December 31, 2018 and 2017, we have no accrued restructuring liability, and there were no related expenses during the years ended December 31 2018 and 2017.