Lymphatic Targeting of anti-HIV Nucleosides: Distribution of 3′-azido-3′-deoxythymidine (AZT) and 3′-azido-2′,3′-dideoxyuridine (AZdU) after Administration of Dipalmitoylphosphatidyl Prodrugs to Mice

Abstract

Human immunodeficiency virus appears to be proliferating within the lymphatic system throughout the period of clinical latency. Targeting of anti-HIV compounds to the lymphatic tissue may therefore provide therapeutic benefits. The purpose of this investigation was to determine the distribution of 3′-azido-3′-deoxythymidine (AZT) and 3′-azido-2′,3′-dideoxyuridine (AZdU) in lymph nodes in a mouse model after administration of the lipophilic prodrugs dipalmitoylphosphatidyl-azidodeoxythymidine (DPP-AZT) and dipalmitoylphosphatidyl-azidodideoxyuridine (DPP-AZdU). Mice received 50 mg kg⁻¹ of parent nucleoside and 164 mg kg⁻¹ of DPP-AZT (equivalent to 50 mg kg⁻¹ AZT) intravenously or orally and 180mg kg⁻¹ DPP-AZdU (equivalent to 50 mg kg⁻¹ AZdU) orally. Serum, neck, axillary and mesenteric lymph nodes were collected at selected times and AZT and AZdU concentrations were determined by HPLC. The disposition of AZT and AZdU in serum and lymph nodes was significantly altered after intravenous and oral administration of DPP-AZT and oral administration of DPP-AZdU when compared to that after administration of parent nucleoside. Lower peak concentrations of AZT and AZdU were observed in serum and lymph nodes after administration of the phospholipid prodrugs. However, DPP-AZT and DPP-AZdU produced consistently higher concentrations of AZT and AZdU, respectively, 2-3 h after prodrug administration. Half-life values for both nucleosides in serum and lymph nodes were significantly greater after prodrug administration. Greater AUC values for nucleosides were noted in neck (AZT and AZdU) and mesenteric (AZT) lymph nodes after administration of prodrugs compared with values obtained for parent drugs. Furthermore, relative lymph node exposure to AZT and AZdU in the lymph nodes was greater after administration of prodrug than after administration of parent compound. Thus, DPP-AZT and DPP-AZdU show potential as useful prodrugs for the delivery of AZT and AZdU to the lymphatic system.