Esoit-poay was a remedy created from the flora of the planet Ecaz, which could cure some deliberating diseases.
Wolfram Moritani's Disorder
Near the end of the Corrino Empire, Wolfram Moritani, heir of House Moritani, had contracted such an illness. Due to his father, Hundro Moritani's, long-standing conflict with the ruler of planet Ecaz, Armand Ecaz, he was unable to procure esoit-poay, and be cured of his disorder.
The grief that Viscount Moritani experienced when Wolfram died of his disease, caused homicidal madness within his father, and Hundro immediately killed Wolfram's Suk Doctor, Vando Terboli, at his son's bed-side. Hundro furthered fulfilled his revenge by assassinating Armand's youngest daughter, Ilesa Ecaz, and her wedding nuptials to Atreides Duke Leto Atreides I. This set off the chain of events which came to be the War of Assassins of 10,187 AG.