In a bizarre sequence of events, the World Health Organization accidentally posted and then removed from its website trial results that seemed to cast doubt on the effectiveness of remdesivir, the Gilead Sciences drug under investigation as a potential treatment for Covid-19, according to the health news website STAT.

Gilead (ticker: GILD) said in a statement that the post “included inappropriate characterizations” of the study, and that, because the study ended early because of troubles enrolling patients, it was not large...