X0303 4 2011-01-21 0 0001142576 OPTIMER PHARMACEUTICALS INC OPTR 0001380901 Chang Michael N 10110 SORRENTO VALLEY ROAD SUITE C SAN DIEGO CA 92121 1 0 0 0 Stock option (right to buy) 12.34 2011-01-21 4 A 0 150000 0 A 2020-05-05 Common stock 150000 150000 D On May 5, 2010, the reporting person was granted an option to purchase 150,000 shares of common stock, subject to the satisfaction of certain performance criteria. The performance criteria was met on January 21, 2011, at which time the option vested as to 37,500 shares. The remaining shares subject to the option vest and become exercisable thereafter in 24 monthly installment. John D. Prunty, attorney-in-fact 2011-01-25