Pharmacokinetic and pharmacodynamic evaluation of elosulfase alfa, an enzyme replacement therapy in patients with Morquio A syndrome.

BACKGROUND AND OBJECTIVES: Morquio A syndrome (mucopolysaccharidosis IVA; MPS IVA) is a lysosomal storage disorder caused by deficiency of N-acetylgalactosamine-6-sulfatase, an enzyme required for degradation of the glycosaminoglycan keratan sulfate. Enzyme replacement therapy with elosulfase alfa provides a potential therapy for Morquio A syndrome. We analyzed the pharmacokinetics and pharmacodynamics of elosulfase alfa in Morquio A patients from a phase III clinical trial. METHODS: In a randomized double-blind study, elosulfase alfa at 2.0 mg/kg was administrated weekly or every other week for 24 weeks. Pharmacokinetic parameters of elosulfase alfa were determined at weeks 0 and 22 by non-compartmental analysis. Safety was assessed throughout the study. The relationship of pharmacokinetic parameters to patient demographics, pharmacodynamic assessments, immunogenicity, and efficacy and safety outcomes were assessed graphically by treatment group. RESULTS: Elosulfase alfa exposure and half-life (t(½)) increased for both dose regimens during the study. There appeared to be no consistent trend between drug clearance (CL) and patient's sex, race, body weight, or age. All patients developed anti-drug antibodies, but no association was noted between total antibody titer and CL. In contrast, positive neutralizing antibody (NAb) status appeared to associate with decreased CL and prolonged t(½) for patients in the cohort dosed weekly. NAb may interfere with receptor-mediated cellular uptake and lead to increased circulation time of elosulfase alfa. CONCLUSION: Despite the association between NAb and decreased drug clearance, neither dosing cohort showed associations between drug exposure and change in urinary keratan sulfate, 6-min walk test distances, or the occurrence of adverse events.

Inhibition of tubulinyl-tyrosine carboxypeptidase by brain soluble RNA and proteoglycan.

Rat brain extracts contain two heat-stable, nondialyzable inhibitors of tubulinyl-tyrosine carboxypeptidase. One of the inhibitors was sensitive to ribonuclease and insensitive to trypsin and pronase, indicating that the inhibitor is RNA. This is supported by the observation that purified RNA from rat brain inhibited the enzyme activity to the same extent as similar amounts of the endogenous RNA. Similar results were obtained with calf liver RNA. The other inhibitor was purified by chromatography on a DEAE-Sephadex and identified as proteoglycan. The elimination of the protein moiety of the proteoglycan resulted in a small increase of its inhibitory activity. Glycosaminoglycan was released from the proteoglycan by beta elimination, indicating that the linkage between glycosaminoglycan and the protein moiety is through an O-glycosidic bond. The glycosaminoglycan contains uronic acid, hexosamine and sulfate in a molar ratio of 1:1.01:0.99, respectively. Treatment of the glycosaminoglycan with chondroitinase ABC completely abolished its inhibitory activity. Chondroitin sulfate A, chondroitin sulfate B, chondroitin sulfate C, and the brain glycosaminoglycan inhibited tubulinyl-tyrosine carboxypeptidase to the same extent when used in comparable amounts.

Compositional changes of urinary acidic glycosaminoglycans in progressive systemic sclerosis.

The compositional changes of acidic glycosaminoglycans (AGAG) in the urine of progressive systemic sclerosis (PSS) patients were studied using chondroitinases and heparitinase in appropriate enzyme assays and by electrophoretic characterization. Daily urinary excretion of AGAG in patients with PSS was increased, when compared to normals. The proportion of urinary AGAG in PSS patients, which was undigested by chondroitinase-ABC (most probably representing heparan sulfates (HS)), increased significantly from the normal value. The substance was found to be mainly HS as determined by the electrophoretic pattern, thin-layer chromatographic analysis and by its susceptibility to heparitinase. After digestion of urinary chondroitin sulfate isomers with chondroitinases, the unsaturated disaccharides were mainly separated into 4-sulfated and 6-sulfated disaccharide units by paper chromatography. In all of the patients with PSS, the ratio of the unsaturated 4-sulfated disaccharide to the unsaturated disaccharide was higher than that in normal subjects. These observations indicate an abnormal turnover of AGAG in patients with PSS.