Rose, M, Menge, M, Bohland, C, Zschiesche, E, Wilhelm, C, Kilp, S, Metz, W, Allan, M, Röpke, R, Nürnberger, M Pharmacokinetics of tildipirosin in porcine plasma, lung tissue, and bronchial fluid and effects of test conditions on in vitro activity against reference strains and field isolates of Actinobacillus pleuropneumoniae. J. vet. Pharmacol. Therap. 36, 140–153. The pharmacokinetics of tildipirosin (Zuprevo® 40 mg/mL solution for injection for pigs), a novel 16‐membered‐ring macrolide for the treatment for swine respiratory disease (SRD), was investigated in studies collecting blood plasma and postmortem samples of lung tissue and bronchial fluid (BF) from swine. In view of factors influencing the in vitro activity of macrolides, and for the interpretation of tildipirosin pharmacokinetics in relation to minimum inhibitory concentrations (MIC), additional experiments were conducted to study the effects of pH, carbon dioxide‐enriched atmosphere, buffers, and serum on tildipirosin MICs for various reference strains and Actinobacillus (A.) pleuropneumoniae field isolates. After single intramuscular (i.m.) injection at 4 mg/kg body weight, maximum plasma concentration (Cmax) was 0.9 μg/mL observed within 23 min (Tmax). Mean residence time from the time of dosing to the time of last measurable concentration (MRTlast) and terminal half‐life (T1/2) both were about 4 days. A dose–response relationship with no significant sex effect is observed for area under the plasma concentration–time curve from time 0 to the last sampling time with a quantifiable drug concentration (AUClast) over the range of doses up to 6 mg/kg. However, linear dose proportionality could not be proven with statistical methods. The time–concentration profile of tildipirosin in BF and lung far exceeded that in blood plasma. In lung, tildipirosin concentrations reached 3.1 μg/g at 2 h, peaked at 4.3 μg/g at day 1, and slowly declined to 0.8 μg/g at day 17. In BF, tildipirosin levels were 14.3, 7.0, and 6.5 μg/g at days 5, 10, and 14. T1/2 in lung was ∼7 days. Tildipirosin is rapidly and extensively distributed to the respiratory tract followed by slow elimination. Culture media pH and carbon dioxide‐enriched atmosphere (CO2‐EA) had a marked impact on in vitro activity of tildipirosin in reference strains of various rapidly growing aerobic and fastidious bacteria including Histophilus (H.) somni ATCC 700025 and A. pleuropneumoniae ATCC 27090. For A. pleuropneumoniae ATCC 27090 testing conditions without CO2‐EA resulted in reduced acidification of culture media pH and a reduction in the minimum inhibitory concentrations compared to standard in vitro test conditions by 2 log2 dilution steps (4‐fold) from 8 to 2 μg/mL. Supplementary buffering of standard culture media resulted in a reduction in the A. pleuropneumoniae (n = 8) MIC range by 4 log2 dilution steps (16‐fold) from 8–16 to 0.5–1 μg/mL. Incremental supplementation of culture media with 50% serum resulted in noticeable shifts to lower minimum or maximum MICs by at least 2 log2 dilution steps (≥4‐...

The pharmacokinetics of tildipirosin (Zuprevo(®) 180 mg/mL solution for injection for cattle), a novel 16-membered macrolide for treatment, control, and prevention of bovine respiratory disease, were investigated in studies collecting blood plasma, lung tissue, and in vivo samples of bronchial fluid (BF) from cattle. After single subcutaneous (s.c.) injection at 4 mg/kg body weight, maximum plasma concentration (C(max)) was 0.7 μg/mL. T(max) was 23 min. Mean residence time from the time of dosing to the time of last measurable concentration (MRT(last)) and terminal half-life (T(1/2) ) was 6 and 9 days, respectively. A strong dose-response relationship with no significant sex effect was shown for both C(max) and area under the plasma concentration-time curve from time 0 to the last sampling time with a quantifiable drug concentration (AUC(last) ) over the range of doses up to 6 mg/kg. Absolute bioavailability was 78.9%. The volume of distribution based on the terminal phase (V(z)) was 49.4 L/kg, and the plasma clearance was 144 mL/h/kg. The time-concentration profile of tildipirosin in BF and lung far exceeded those in blood plasma. In lung, tildipirosin concentrations reached 9.2 μg/g at 4 h, peaked at 14.8 μg/g at day 1, and slowly declined to 2.0 μg/g at day 28. In BF, the concentration of tildipirosin reached 1.5 and 3.0 μg/g at 4 and 10 h, maintained a plateau of about 3.5 μg/g between day 1 and 3, and slowly declined to 1.0 at day 21. T(1/2) in lung and BF was approximately 10 and 11 days. Tildipirosin is rapidly and extensively distributed to the respiratory tract followed by slow elimination.

γ-tilmanocept (Technetium-99m–labeled- or 99mTc-tilmanocept) is the first mannose-containing, receptor-directed, radiolabeled tracer for the highly sensitive imaging of sentinel lymph nodes (SLNs) in solid tumor staging. To elucidate the mannose-binding receptor that retains tilmanocept in this microenvironment, human macrophages were used which have high expression of the C-type lectin mannose receptor (MR, CD206). Cy3-labeled tilmanocept exhibited high specificity binding to macrophages that was nearly abolished in competitive inhibition experiments. Furthermore, Cy3-tilmanocept binding was markedly reduced on macrophages deficient in the MR by siRNA treatment, and increased on MR-transfected HEK 293 cells. Finally, confocal microscopy revealed co-localization of Cy3-tilmanocept with the macrophage membrane MR and binding of labeled tilmanocept to MR-positive cells [macrophages and/or dendritic cells (DCs)] in human SLN tissues. Together these data provide strong evidence that CD206 is a major binding receptor for γ-tilmanocept. Identification of CD206 as the γ-tilmanocept-binding receptor enables opportunities for designing receptor-targeted advanced imaging agents and therapeutics for cancer and other diseases.

Background-Several 99m Tc-labeled agents that are not approved by the U.S. Food and Drug Administration are used for lymphatic mapping. A new low-molecular-weight mannose receptorbased, reticuloendothelial cell-directed, 99m Tc-labeled lymphatic imaging agent, 99m Tc-tilmanocept, was used for lymphatic mapping of sentinel lymph nodes (SLNs) from patients with primary breast cancer or melanoma malignancies. This novel molecular species provides the basis for potentially enhanced SLN mapping reliability.

Sentinel lymph node (SLN) mapping is common, however question remains as to what the ideal imaging agent is and how such an agent might provide reliable and stable localization of SLNs. (99m)Tc-labeled nanocolloid human serum albumin (Nanocoll) is the most commonly used radio-labeled colloid in Europe and remains the standard of care (SOC). It is used in conjunction with vital blue dyes (VBDs) which relies on simple lymphatic drainage for localization. Although the exact mechanism of Nanocoll SLN localization is unknown, there is general agreement that Nanocoll exhibits the optimal size distribution and radiolabeling properties of the commercially available radiolabel colloids. [(99m)Tc]Tilmanocept is a novel radiopharmaceutical designed to address these deficiencies. Our aim was to compare [(99m)Tc]Tilmanocept to Nanocoll for SLN mapping in breast cancer. Data from the Phase III clinical trials of [(99m)Tc]Tilmanocept's concordance with VBD was compared to a meta-analysis of a review of the literature to identify a (99m)Tc albumin colloid SOC. The primary endpoints were SLN localization rate and degree of localization. Six studies were used for a meta-analysis to identify the colloid-based SOC. Five studies (6,134 patients) were used to calculate the SOC localization rate of 95.91 % (CI 0.9428-0.9754) and three studies (1,380 patients) were used for the SOC SLN degree of localization of 1.6683 (CI 1.5136-1.8230). The lower bound of the confidence interval was used for comparison to Tilmanocept. Tilmanocept data included 148 patients, and pooled analysis revealed a 99.99 % (CI 0.9977-1.0000) localization rate and degree of localization of 2.16 (CI 1.964-2.3600). Tilmanocept was superior to the Nanocoll SOC for both endpoints (P < 0.0001).