Campbell and colleagues reported unprecedented antiparasitic effects of the agent in vivo, and that the "B1a" component of the molecule was most effective as a single oral dose.
(Order of authorship in the original publication: Egerton, Oslin, Blair....Campbell.) Digital facsimile from PubMedCentral at this link.

In 2015 William C. Campbell shared half of the Nobel Prize in Physiology or Medicine with Satoshi Ōmura “for their discoveries concerning a novel therapy against infections caused by roundworm parasites.” The other half was awarded to Tu Youyou “for her discoveries concerning a novel therapy against Malaria.”

(Thanks to Juan Weiss for this reference and its interpretation.)