Targeting dexamethasone to macrophages in a porcine endotoxemic model.

OBJECTIVES: Macrophages are important cells in immunity and the main producers of pro-inflammatory cytokines. The main objective was to evaluate if specific delivery of glucocorticoid to the macrophage receptor CD163 is superior to systemic glucocorticoid therapy in dampening the cytokine response to lipopolysaccharide infusion in pigs. DESIGN: Two randomized, placebo-controlled trials. SETTING: University hospital laboratory. SUBJECTS: Female farm-bred pigs (26-31 kg). DESIGN: A humanized antibody that binds to pig and human CD163 was produced, characterized, and conjugated with dexamethasone. In the first study (total n = 12), pigs were randomly assigned to four groups: 1) saline; 2) dexamethasone (1.0 mg/kg); 3) dexamethasone (0.02 mg/kg); and 4) anti-CD163-conjugated dexamethasone (0.02 mg/kg). In the second study (total n = 36), two additional groups were included in addition to the four original groups: 5) anti-CD163-conjugated dexamethasone (0.005 mg/kg); 6) unconjugated anti-CD163. Treatments were given 20 hours prior to infusion of lipopolysaccharide (1 µg × kg × h) for 5 hours. Blood samples were analyzed for cytokines, cortisol, and adrenocorticotropic hormone. RESULTS: In the saline group, lipopolysaccharide increased cytokine and plasma cortisol levels. In both studies, dexamethasone (1 mg/kg) and anti-CD163 dexamethasone (0.02 mg/kg) uniformly attenuated tumor necrosis factor-α peak levels (both p < 0.05) compared with low-dose dexamethasone (0.02 mg/kg). However, dexamethasone 1 mg/kg significantly suppressed plasma cortisol and adrenocorticotropic hormone levels compared with anti-CD163 dexamethasone (0.02 mg/kg; p < 0.05). No significant hemodynamic difference existed between groups. The anti-CD163 dexamethasone drug conjugate exhibited a fast plasma clearance, with a half-life of approximately 5-8 minutes. CONCLUSION: Targeted delivery of dexamethasone to macrophages using a humanized CD163 antibody as carrier exhibits anti-inflammatory effects comparable with 50 times higher concentrations of free dexamethasone and does not inhibit endogenous cortisol production. This antibody-drug complex showing similar affinity and specificity for human CD163 is, therefore, a promising drug candidate in this novel type of anti-inflammatory therapy.

An extended study of dimeric phenyl tropanes.

A series of dimeric phenyl tropanes consisting of two molecules of 4-chloro, 4-iodo or 4-(3-thiopheno)-phenyl tropane tethered together at the carboxylic acid moiety by a diamine or diol linker were prepared. The diamines used were a variety of linear, cyclic and aromatic diamines, while the diol tethered compounds were prepared by 'click' chemistry and contained a triazole in the linker. The new compounds were tested for binding to hDAT, hSERT and hNET. Amide linked chlorophenyl tropanes with an aromatic linker was found to be potent and selective DAT inhibitors with the best K(i) value for hDAT being 6nM. The ester linked halophenyl tropanes were more potent but displayed little selectivity in inhibition of monoamine transporter binding. Among the studied compounds an ester linker of 10 atoms between the tropane moieties gave the highest affinity. One monomeric phenyl tropane was made for comparison and was found to be less potent than the dimeric counterparts towards SERT and NET but remain highly active against DAT. Dimeric thiophenophenyl tropanes were in general found to be comparatively poor monoamine transporter binders, but significant gains of affinity of up to 45-fold could be achieved with selected dimeric chlorophenyl tropanes compared to the parent monomer. This observation implies that a secondary binding site that has affinity for phenyl tropanes, most likely the putative S2 site, is located within 13A of the primary central S1 binding site.

Synthesis, inhibition and binding of simple non-nitrogen inhibitors of monoamine transporters.

A series of simple truncated analogues of phenyl tropanes, 2-arylcycloalk-1-enyl carboxylic acid methylesters, were prepared and investigated for their activity towards the dopamine, serotonin and norepinephrine transporters. The compounds were prepared from cyclic ketoesters, which were converted to enolic triflates and reacted with arylboronates using the Suzuki coupling. For comparison the corresponding piperidines were also made and investigated. The new compounds inhibit monoamine-transporters with Ki values ranging from 0.1 to 1000 microM.