Anticancer Properties of Halogenated Pyrrolo[3,2‐d]pyrimidines with Decreased Toxicity via N5 Substitution

Halogenated pyrrolo3,2‐d]pyrimidine analogues have shown antiproliferative activity in recent studies, with cell accumulation occurring in the G₂/M stage without apoptosis. However, the mechanism of action and pharmacokinetic (PK) profile of these compounds has yet to be determined. To investigate the PK profile of these compounds, a series of halogenated pyrrolo3,2‐d]pyrimidine compounds was synthesized and first tested for activity in various cancer cell lines followed by a mouse model. EC₅₀ values ranged from 0.014 to 14.5 μm , and maximum tolerated doses (MTD) in mice were between 5 and 10 mg kg^?1. This indicates a wide variance in activity and toxicity that necessitates further study. To decrease toxicity, a second series of compounds was synthesized with N5‐alkyl substitutions in an effort to slow the rate of metabolism, which was thought to be leading to the toxicity. The N‐substituted compounds demonstrated comparable cell line activity (EC₅₀ values between 0.83–7.3 μm ) with significantly decreased toxicity (MTD=40 mg kg^?1). Finally, the PK profile of the active N5‐substituted compound shows a plasma half‐life of 32.7 minutes, and rapid conversion into the parent unsubstituted analogue. Together, these data indicate that halogenated pyrrolo3,2‐d]pyrimidines present a promising lead into potent antiproliferative agents with tunable activity and toxicity, and rapid metabolism.