Cell type-selective targeted delivery of a recombinant lysosomal enzyme for enzyme therapies.

Lysosomal diseases are a class of genetic disorders predominantly caused by loss of lysosomal hydrolases, leading to lysosomal and cellular dysfunction. Enzyme replacement therapy (ERT), where recombinant enzyme is given intravenously, internalized by cells, and trafficked to the lysosome, has been applied to treat several lysosomal diseases. However, current ERT regimens do not correct disease phenotypes in all affected organs because the biodistribution of enzyme uptake does not match that of the affected cells that require the enzyme. We present here targeted ERT, an approach that utilizes antibody-enzyme fusion proteins to target the enzyme to specific cell types. The antibody moiety recognizes transmembrane proteins involved in lysosomal trafficking and that are also preferentially expressed in those cells most affected in disease. Using Pompe disease (PD) as an example, we show that targeted ERT is superior to ERT in treating the skeletal muscle phenotypes of PD mice both as a protein replacement therapeutic and as a gene therapy.

Anti-obesity, anti-diabetic, and lipid lowering effects of the thyroid receptor beta subtype selective agonist KB-141.

Selective thyroid hormone receptor subtype-beta (TRbeta) agonists have received attention as potential treatments for hypercholesterolemia and obesity, but have received less attention as treatments for diabetes, partly because this condition is not improved in thyroid hormone excess states. The TRbeta selective agonist KB-141 induces 5-10% increases in metabolic rate and lowering of plasma cholesterol levels without tachycardia in lean rats, unlike the major active thyroid hormone, T3. In the current study, we determined whether KB-141 promotes weight loss in obese animals and whether it exhibits anti-diabetogenic effects. Body weight, adiposity (DEXA), and lipid levels were examined following p.o. administration of KB-141 to obese Zucker fa/fa rats at 0.00547-0.547 mg/kg/day for 21 days, and in ob/ob mice at 0.5mg/kg/day KB-141 for 7 days. In rats, KB-141 reduced body weight by 6 and 8%, respectively, at 0.167 and 0.0547 mg/kg/day without tachycardia and adiposity was reduced at 0.167 mg/kg/day (5-6%). In ob/ob mice, KB-141 lowered serum cholesterol (35%), triacylglycerols (35%) and both serum and hepatic free fatty acids (18-20%) without tachycardia. Treatment of ob/ob mice with KB-141 (0.0547 or 0.328 mg/kg/day over 2 weeks) improved glucose tolerance and insulin sensitivity in a dose-dependent manner with no effect on heart rate. Thus, KB-141 elicits anti-obesity, lipid lowering and anti-diabetic effects without tachycardia suggesting that selective TRbeta activation may be useful strategy to attenuate features of the metabolic syndrome.

Pharmacological profile of the thyroid hormone receptor antagonist NH3 in rats.

NH3 is a thyroid hormone receptor (TR) antagonist that inhibits binding of thyroid hormones to their receptor and that inhibits cofactor recruitment. It was active in a tadpole tail resorption assay, with partial agonist activity at high concentrations. We determined the effect of NH3 on the cholesterol-lowering, thyroid stimulating hormone (TSH)-lowering, and tachycardic action of thyroid hormone (T(3)) in rats. Cholesterol-fed, euthyroid rats were treated for 7 days with NH3, and a dose response (46.2-27,700 nmol/kg/day) was determined. We also determined the effect of two doses of T(3) on the NH3 dose-response curve. NH3 decreased heart rate modestly starting at 46.2 nmol/kg/day, but the effect was lost at >2920 nmol/kg/day. At 27,700 nmol/kg/day, tachycardia was seen, suggesting partial agonist activity. NH3 increased plasma cholesterol to a maximum of 27% at 462 nmol/kg/day. At higher doses, cholesterol was reduced, suggesting partial agonist activity. Plasma TSH was increased from 46.2 to 462 nmol/kg/day NH3, but at higher doses, this effect was lost, and partial agonist effects were apparent. T(3) at 15.4 and 46.2 nmol/kg/day increased heart rate, reduced cholesterol, and reduced plasma TSH. NH3 inhibited the cholesterol-lowering, TSH-lowering and tachycardic effects of 15.4 nmol/kg/day T(3), but much of the effect was lost at >924 nmol/kg/day doses. NH3 had no effect on the cholesterol-lowering action of 46.2 nmol/kg/day T(3), but it inhibited the tachycardic and TSH suppressant effects up to the 924 nmol/kg/day dose. Single doses of 462 and 27,700 nmol/kg caused no TR inhibitory effects. In conclusion, NH3 has TR antagonist properties on T(3)-responsive parameters, but it has partial agonist properties at higher doses.