Status of enzyme replacement therapy for Gaucher disease

At this point in time, enzyme replacement therapy for Gaucher disease appears both biochemically effective (patients 1-3, and 10) as well as clinically promising (patients 4 and 5), although these salutary responses have not been obtained consistently (patients 6-9). The discrepancy may be due to the method employed for the isolation of the enzyme. One current opinion is that glucocerebrosidase prepared by conventional fractionation and ion exchange chromatographic procedures may have been more effective in vivo than enzyme prepared by butanol extraction and hydrophobic column chromatography, which we developed because of the difficulty in obtaining large quantities of glucocerebrosidase by the conventional method. It should be remembered that the enzyme prepared by the latter procedure was fully active on glucocerebroside in liver biopsy specimens in vitro. Furthermore, glucocerebrosidase prepared by the second method exerted a positive effect in 2 young patients, who received relatively large amounts of enzyme, and in an adult who was treated with corticosteroid prior to infusion of the enzyme. At this moment, a possible explanation is that a necessary associated factor, perhaps a lipid, may have been removed by the large-scale isolation procedure. We are attempting to improve the biochemical and clinical responses to enzyme infusion by investigating the effects of lysosomal modifying agents and by enhancing the uptake and localization of the infused enzyme in lysosomes of cells that contain the stored glucocerebroside.

[Therapeutics future of liposomes (author's transl)]

The possibility to use the liposomes as drug vehicles has been largely investigated in recent years. Most of the studies have been carried out in animals and are related to disease involving predominantly the reticulohistiocytic system. Attempts to use these liposomes orally (induced diabetes) or locally (induced arthritis) are also reported. Further trials are required to get a better knowledge of the mechanisms involved in the exchanges between the cell membrane and the liposome the latter being variable as regards its composition, size and permeability according to the various investigators; the adjustment to the liposome of a complex capable to electively direct it towards the target organ is studied.

Incorporation of glucocerebrosidase into Gaucher's disease monocytes in vitro

Several carriers were evaluated for use in the delivery of exogenous glucocerebrosidase to monocytes from Gaucher's disease patients. Only gamma globulin-coated, resealed erythrocytes proved to be an effective vehicle for enzyme delivery. Glucocerebrosidase added in this manner normalized intracellular enzyme levels for at least 18 hr. In this model system for the study of enzyme replacement therapy, soluble enzyme, enzyme in uncoated resealed erythrocytes, and enzyme incorporated into liposomes were ineffective.

Enzyme replacement therapy in Gaucher's disease: preliminary clinical trial of a new enzyme preparation

A patient with far-advanced adult type Gaucher's disease was treated with solubilized, highly purified placental glucocerebrosidase administered after entrapment in human erythrocytes or by direct intravenous injection. In some instances the enzyme-containing erythrocytes were coated with gamma globulin. No toxic side effects were observed after enzyme infusion. There were suggestive, but not conclusive, findings that enzyme infusion may have been beneficial. After therapy, there was a decrease in transfusion requirement, some improvement of liver function, possible decrease in liver size, and relief of subjective symptoms. Erythrocyte and plasma glucocerebroside levels were unchanged during therapy, but there was a possibly significant decrease in leukocyte and platelet levels of the glycolipid. No changes occurred in serum acid phosphatase or angiotensin-converting enzyme activity.

Enzyme replacement therapy in Gaucher's disease: large-scale purification of glucocerebrosidase suitable for human administration

Enzyme replacement therapy for the alleviation of Gaucher's disease has been impeded because of the difficulty in preparing large amounts of glucocerebrosidase, the enzyme that is deficient in patients with this disorder. A large-scale procedure for the purification of human placental glucocerebrosidase has been developed. The method uses cholate extraction, ammonium sulfate fractionation, acid precipitation, butanol extraction, and hydrophobic chromatography; the final enzyme preparation has a specific activity of more than 10(6) units/mg of protein with an overall recovery of 30%. In addition, the contamination of enzyme preparations, intended for human infusion, prepared by isolation procedures involving concanavalin A columns has been studied and is reported here.

Treatment of Gaucher's disease with liposome-entrapped glucocerebroside: beta-glucosidase

An adult with Gaucher's disease was injected with liposomes containing human glucocerebroside: beta-glucosidase. After 13 months of treatment the lower border of the right hepatic lobe and moved up 3 cm, and the left lobe had shrunk. Reduction in the size of the liver was associated with relief of pressure symptoms in the left lower abdomen. Scans obtained after the injection of radiolabelled liposomes suggested improvement in function of the reticuloendothelial system.

Enzyme replacement therapy in Gaucher's and Fabry's disease

Glucocerebrosidase and ceramidetrihexoside-alpha-galactosidase were obtained in a high degree of purity from human placental tissue. The enzymes were infused in Gaucher and Fabry patients, respectively. Following the administration of the proteins to supplement the genetically determined deficiencies, there resulted a specific reduction in the accumulated hlycolipids in the circulation and liver. These results indicate that enzyme replacement may provide hope for the clinical treatment of these disorders.

Enzyme replacement therapy in Gaucher's disease: a rapid, high-yield method for purification of glucocerebrosidase

Gaucher's disease is caused by a deficiency of the lysosomal enzyme glucocerebrosidase (glucosylceramidase; D-glucosyl-N-acylsphingosine glucohydrolase, EC 3.2.1.45); this disorder has been a leading candidate for enzyme replacement trials. A rapid, high-yield method for purification of glucocerebrosidase has been developed. Detergent extraction of human placenta was followed by salt fractionation, concanavalin A-Sepharose chromatography, organic solvent precipitation, and affinity chromatography on phosphatidylserine-agarose; the total yield is 60% with 6000-fold purification. Purified glucocerebrosidase has been administered intravenously to a volunteer Gaucher's patient on two separate occasions. For the first injection, the enzyme was entrapped in resealed erythrocytes; for the second injection, the enzyme was given without any carrier. The enzyme infusions caused no untoward effects.

Investigations in enzyme replacement therapy in lipid storage diseases

Enzyme replacement appears to offer much promise as specific therapeutic procedures for patients with Fabry's disease and Gaucher's disease. However, enzyme replacement in patients with Tay-Sachs disease and other heritable metabolic disorders where the central nervous system is affected will require first the development of effective methods for the delivery of exogenous enzymes to the brain; such methods are not yet available.

The lipid storage diseases: new concepts and control

The nature of the enzymatic defect is now well established in ten inherited disorders of lipid metabolism. This information has provided for the development of facile, sensitive tests using readily available materials such as washed leukocytes or cultured skin fibroblasts for the diagnosis of these disorders; the detection of heterozygous carriers of these traits; and the monitoring of pregnancies at risk for any of these conditions. Recent investigations of enzyme replacement therapy have shown great promise for the treatment of patients with Fabry's disease and those with the adult form of Gaucher's disease. Additional procedures must be developed for successful enzyme replacement in patients where the central nervous system is damaged by the accumulation of lipids.

Enzyme loading of erythrocytes

We demonstrated that beta-glucosidase and beta-galactosidase can be trapped inside erythrocytes by rapid hemolysis of the cell in the presence of these enzymes. Enzyme enters only during hemolysis, and optimum uptake occurs within 60 sec. There is no loss in cell number after hemolysis-induced enzyme uptake, and the ghosts have only a slightly increased mean cell volume. Smaller proteins enter more readily than larger proteins, although enzymes with a molecular weight of at least 180,000 can be readily entrapped by erythrocytes. This finding may provide a useful approach to the problem of enzyme replacement in certain diseases, including Gaucher's disease.