Structural requirements for alkylglycoside-type renal targeting vector

Synthesis, characterization and assessment of suitability of trehalose fatty acid esters as alternatives for polysorbates in protein formulation

Nonionic polyethylene glycol-derived surfactants are today's choice as surfactants in protein formulations. Different groups discovered that although surface-induced stresses are reduced by these excipients, the long-term stability of different proteins decreased due to polyethylene glycol-related induction of oxidation processes under static storage conditions. In this paper, the potential of polyoxyethylene-free surfactants for protein formulation was evaluated. Three different sugar-based surfactants, 6-O-monocaprinoyl-α,α-trehalose, 6-O-monolauroyl-α,α-trehalose and 6-O-monopalmitoyl-α,α-trehalose, were synthesized in four reaction steps. These substances lack polyethylene glycol residues and can be produced from renewable resources. The chemical and physical properties of these three surfactants were investigated and compared with polysorbate 20 and 80. 6-O-monopalmitoyl-α,α-trehalose was insoluble in water at room temperature and was hence excluded from some of the further tests. The critical micellar concentration of all surfactants is in a comparable range of approximately 0.001-0.01% (m/V). The sugar-based surfactants showed slightly higher hemolytic activity than the polysorbate references. The surfactants with shorter chain length proved to be comparable to polysorbates in regard to physicochemical properties. Finally for human growth hormone, the protein-stabilizing properties against shaking-induced stress were tested and compared to polysorbate-containing formulations. Whereas in the absence of surfactant, dramatic monomer loss and aggregate formation occurred, it was found that 100% monomer content was maintained when 0.1% (m/V) 6-O-monocaprinoyl-α,α-trehalose or 6-O-monolauroyl-α,α-trehalose was added to the formulation. Polysorbate 80 at a concentration of 0.1% (m/V) also significantly stabilized the protein. Lower amounts of surfactants result in only partial stabilization. Furthermore, adsorption of human growth hormone to the container surface is reduced in the presence of the surfactants. Thus, the new sugar-based surfactants offer a promising alternative and have potential for application in protein formulations.

Thioglycosides as inhibitors of hSGLT1 and hSGLT2: potential therapeutic agents for the control of hyperglycemia in diabetes

The treatment of diabetes has been mainly focused on maintaining normal blood glucose concentrations. Insulin and hypoglycemic agents have been used as standard therapeutic strategies. However, these are characterized by limited efficacy and adverse side effects, making the development of new therapeutic alternatives mandatory. Inhibition of glucose reabsorption in the kidney, mediated by SGLT1 or SGLT2, represents a promising therapeutic approach. Therefore, the aim of the present study was to evaluate the effect of thioglycosides on human SGLT1 and SGLT2. For this purpose, stably transfected Chinese hamster ovary (CHO) cells expressing human SGLT1 and SGLT2 were used. The inhibitory effect of thioglycosides was assessed in transport studies and membrane potential measurements, using alpha-methyl-glucoside uptake and fluorescence resonance energy transfer, respectively. We found that some thioglycosides inhibited hSGLT more strongly than phlorizin. Specifically, thioglycoside I (phenyl-1'-thio-beta-D-glucopyranoside) inhibited hSGLT2 stronger than hSGLT1 and to a larger extent than phlorizin. Thioglycoside VII (2-hydroxymethyl-phenyl-1'-thio-beta-D-galacto-pyranoside) had a pronounced inhibitory effect on hSGLT1 but not on hSGLT2. Kinetic studies confirmed the inhibitory effect of these thioglycosides on hSGLT1 or hSGLT2, demonstrating competitive inhibition as the mechanism of action. Therefore, these thioglycosides represent promising therapeutic agents for the control of hyperglycemia in patients with diabetes.

Radiolabeled Carbohydrated Somatostatin Analogs: A Review of the Current Status

During the last decade, peptide radiopharmaceuticals have become an important class of tracers for the detection and localization of malignant neoplasms by peptide receptor imaging (PRI) and for therapeutic intervention by peptide receptor radiotherapy (PRRT). Various radiometalated peptides have entered detailed clinical studies or found broad application for peptide receptor radiotherapy. In contrast, radiohalogenated peptides could not benefit from this development. Especially with respect to the growing number of peptidic structures with high receptor affinity and the increasing demand for means of corresponding receptor status quantification for therapy planning and control, the development of methods for the improved availability of 18F-labeled peptides for positron emission tomography imaging is still a very important objective in radiopharmaceutical research. Consequently, as part of our ongoing efforts in this field, we investigated the potential of carbohydration as a valuable tool to modify pharmacokinetics of peptides and evaluated the influence of this modification on the in vitro and in vivo behavior of octreotide analogs. Furthermore, a new methodology is presented allowing for the fast and straightforward labeling of peptides in a chemoselective manner. This combined approach to the chemoselective conjugation of unprotected, carbohydrated peptides seems to have the potential for a redirection and reevaluation of the future of radiohalogenated peptides in nuclear medicine.

Detection of the membrane protein recognized by the kidney-specific alkylglucoside vector

PURPOSE

Previously, we suggested that alkylglucoside can be an effective vector for renal-specific drug delivery (Suzuki et al., J. Pharmacol. Exp. Ther, 288:57-61, 1999). The purpose of the present study is to characterize the membrane protein which is recognized by this alkylglucoside.

METHODS

The binding of [125I] tyrosine conjugated with a octylthioglucoside (Glc-S-C8-[125I]Tyr) Glc-S-C8-[125I]Tyr to crude membrane fractions of kidney was determined. In addition, the membrane was cross-linked with this alkylglucoside and examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis.

RESULTS

Glc-S-C8-[125I]Tyr was shown to have a specific binding site on the kidney membrane (Kd = 931 nM and Bmax = 987 pmol/mg protein). Cross-linking of the membrane with Glc-S-C8-[125I]Tyr resulted in the detection of a protein (Mr = 62,000), which was unaffected by reducing agents. The results of this cross-linking study were consistent with previous information on its localization and binding characteristics.

CONCLUSIONS

The kidney membrane protein, to which alkylglucoside binds in a specific manner, has a molecular weight of 62,000. Crosslinking is a useful tool for detecting this novel membrane protein in kidney.