ANTI-HUMAN-IMMUNODEFICIENCY-VIRUS ACTIVITY AND CELLULAR-METABOLISM OFA POTENTIAL PRODRUG OF THE ACYCLIC NUCLEOSIDE PHOSPHONATE 9-R-(2-PHOSPHONOMETHOXYPROPYL)ADENINE (PMPA), BIS(ISOPROPYLOXYMETHYLCARBONYL)PMPA

Bis(isopropyloxymethylcarbonyl) 9-R-(2-phosphonomethoxypropyl)adenine [bis(POC)PMPA] has been identified as a novel prodrug of PMPA. The ant i-human immunodeficiency virus activity of bis(POC)PMPA was >100-fold greater than that of PMPA in both an established T-cell line and prima ry peripheral blood lymphocytes. This improved efficacy was shown to b e due to a rapid intracellular uptake of the prodrug resulting in an i ncreased intracellular accumulation of PMPA diphosphate (PMPApp), the pharmacologically active metabolite, PMPApp levels in bis(POC)PMPA-tre ated cells exceeded by >1,000-fold the levels seen in cells treated wi th unmodified PMPA in both resting and activated peripheral blood lymp hocytes. Significant differences in the intracellular catabolism of PM PA metabolites were noted between the resting and activated lymphocyte s. The half-life for the disappearance of PMPApp, derived from either bis(POC)PMPA or PMPA, was 12 to 15 h in the activated lymphocytes and 33 to 50 h in the resting lymphocytes. This long persistence of PMPApp , particularly in resting lymphocytes, may be unique to the nucleoside phosphonate analogs and indicates that effective levels of the active metabolite can be achieved and maintained with relatively infrequent administration of the parent drug.