Aziridinyl quinone antitumor agents can be metabolically unstable due to a sigmatropic shift reaction that changes their structure. Benzoquinone-based agents like DZQ and AZQ are more stable than indole-based ones like EO9 because they don't undergo this reaction as quickly. This difference in stability affects how these agents are metabolized in the body, with benzoquinone-based agents being less likely to be rapidly inactivated.