Comparative pharmacokinetic, immunologic and hematologic studies on the anti-HIV-1/2 compounds aconitylated and succinylated HSA

Abstract

Charge modification by succinylation or cis-aconitylation of the terminal ϵNH₂ functions of the amino acid lysine in human serum albumin, resulted in polyanionic compounds with an anti-HIV-1 activity in the low nanomolar concentration range. After iv injections in rats of the negatively charged albumins (NCAs), a dose dependent elimination pattern was observed indicating a saturable eliminations pathway. The Michaelis-Menten parameters V_max and K_m were 62 ± 8 μg.min⁻¹.kg⁻¹ and 16 ± 4 μg.ml⁻¹ (Cl_intr 3.9 ± 1.1 ml.min⁻¹.kg-1) and 74 ± 6 μg.min⁻¹.kg⁻¹ and 11 ± 2 μg.ml⁻¹ (Cl_intr 6.7 ± 1.2 ml.min⁻¹.kg⁻¹) for aconitylated-HSA (Aco-HSA) and succinylated-HSA (Suc-HSA) respectively, using ¹²⁵I-labelled proteins. The volume of distribution (V) of both compounds was approximately 60 ml.kg⁻¹. Coadministration of poly-inosinic acid and formaldehyde treated albumin showed a marked inhibition of blood clearance indicating that the compounds are mainly cleared from the bloodstream by scavenger receptors on liver and spleen endothelial cells and macrophages.

The Michaelis-Menten constant K_m was remarkably higher when the hydrophobic fluorophore fluorescein was covalently linked to the protein, indicating that the affinity for the scavenger receptors is largely decreased by FiTC conjugation. The latter observation may have implications for the kinetic behavior of drug-carrier preparations if antiviral drugs like AZT or PMEA are linked to these intrinsic active carriers.

In contrast to other polyanionic compounds like heparins and dextran sulfate, these NCAs did not exhibit acute toxicity and had no effect on blood coagulation. They neither had an effect on the lymphocyte proliferation. Studies on immunogenicity of the homologous derivatized albumins in rats did not show a significant response.

The present pharmacokinetic and toxicologic data of Suc-HSA and Aco-HSA show that both compounds are interesting preparations for studies in SIV infected monkeys and AIDS patients.

Key Words:

• Pharmacokinetics
• Suc-HSA
• Aco-HSA
• AIDS
• HIV
• Polyanions
• Toxicity
• Immunogenicity