Some semicarbazones, such as nitrofurazone, and thiosemicarbazones are known to have anti-viral and anti-cancer activity, usually mediated through binding to copper or iron in cells.  Many semicarbazones are crystalline solids, useful for the identification of the parent aldehydes/ketones by melting point analysis.
A thiosemicarbazone is an analog of a semicarbazone which contains a sulfur atom in place of the oxygen atom.