Disable Evoluent vertical mouse thumb and bottom buttons

My Evoluent vertical mouse has a thumb and bottom button. I got the mouse for ergonomic reasons, not for these buttons, and I occasionally click them by accident which causes actions I didn't intend. The following xmodmap command disables them:

xmodmap -e "pointer = 1 2 3 4 5 15 14 13 12 10 11 9 8 7 6"