"In October 1987, Roy Vagelos, then the chief executive of [pharmaceutical company] Merck, launched the largest pharmaco-philanthropic venture ever," William Foege, an epidemiologist and former director of the CDC, writes in a Washington Post opinion piece highlighting the company's efforts to combat onchocerciasis in the developing world through the free distribution of its drug Mectizan. Initially developed to protect dogs against heartworms, Merck found a human version of the drug "could inhibit the microfilaria of onchocerciasis for a year with a single dose," Foege continues, adding, "Merck said that it would supply the drug as long as it was needed. Extended surveillance has shown this to be one of the safest drugs ever developed."