Although doctors cured the disease that Mr. Harper suffered from, he still suicided.
You can use 'suicided' like this. Although it's pretty unusual (and some people won't like it), here are two real examples:
(1) Timmons found out she suicided. [source: Law and Order US TV show]
(2) As police surrounded him on a nearby highway, he suicided. [source: Sydney Morning Herald Newspaper]