A phase I study of pivaloyloxymethyl butyrate, a prodrug of the differentiating agent butyric acid, in patients with advanced solid malignancies.

Pivaloyloxymethyl butyrate (AN-9), an acyloxyalkyl ester prodrug of butyric acid (BA), has demonstrated greater potency than BA at inducing malignant cell differentiation and tumor growth inhibition and has demonstrated more favorable toxicological, pharmacological, and pharmaceutical properties than BA in preclinical studies. The principal objective of this study was to determine the feasibility of administering AN-9 as a 6-h i.v.