Noninvasive real-time fluorescence imaging of the lymphatic uptake of BSA-IRDye 680 conjugate administered subcutaneously in mice

Understanding Inter-Individual Variability in Monoclonal Antibody Disposition

Monoclonal antibodies (mAbs) are currently the largest and most dominant class of therapeutic proteins. Inter-individual variability has been observed for several mAbs; however, an understanding of the underlying mechanisms and factors contributing to inter-subject differences in mAb disposition is still lacking. In this review, we analyze the mechanisms of antibody disposition and the putative mechanistic determinants of inter-individual variability. Results from in vitro, preclinical, and clinical studies were reviewed evaluate the role of the neonatal Fc receptor and Fc gamma receptors (expression and polymorphism), target properties (expression, shedding, turnover, internalization, heterogeneity, polymorphism), and the influence of anti-drug antibodies. Particular attention is given to the influence of co-administered drugs and disease, and to the physiological relevance of covariates identified by population pharmacokinetic modeling, as determinants of variability in mAb pharmacokinetics.

Optical tracer size differences allow quantitation of active pumping rate versus Stokes-Einstein diffusion in lymphatic transport

Lymphatic uptake of interstitially administered agents occurs by passive convective–diffusive inflow driven by interstitial concentration and pressure, while the downstream lymphatic transport is facilitated by active propulsive contractions of lymphatic vessel walls. Near-infrared fluorescence imaging in mice was used to measure these central components of lymphatic transport for the first time, using two different-sized molecules––methylene blue (MB) and fluorescence-labeled antibody immunoglobulin G (IgG)-IRDye 680RD. This work confirms the hypothesis that lymphatic passive inflow and active propulsion rates can be separated based upon the relative differences in Stokes–Einstein diffusion coefficient. This coefficient specifically affects the passive-diffusive uptake when the interstitial volume and pressure are constant. Parameters such as mean time-to-peak signal, overall fluorescence signal intensities, and number of active peristaltic pulses, were estimated from temporal imaging data. While the mean time to attain peak signal representative of diffusion-dominated flow in the lymph vessels was 0.6±0.2??min for MB and 8±6??min for IgG, showing a size dependence, the active propulsion rates were 3.4±0.8??pulses/min and 3.3±0.5??pulses/min, respectively, appearing size independent. The propulsion rates for both dyes decreased with clearance from the interstitial injection-site, indicating intrinsic control of the smooth muscles in response to interstitial pressure. This approach to size-comparative agent flow imaging of lymphatic function can enable noninvasive characterization of diseases related to uptake and flow in lymph networks.

Preparation and characterization of anti-HIV nanodrug targeted to microfold cell of gut-associated lymphoid tissue

The human immunodeficiency virus 1 (HIV-1) still remains one of the leading life-threatening diseases in the world. The introduction of highly active antiretroviral therapy has significantly reduced disease morbidity and mortality. However, most of the drugs have variable penetrance into viral reservoir sites, including gut-associated lymphoid tissue (GALT). Being the largest lymphoid organ, GALT plays a key role in early HIV infection and host–pathogen interaction. Many different treatment options have been proposed to eradicate the virus from GALT. However, it becomes difficult to deliver traditional drugs to the GALT because of its complex physiology. In this regard, we developed a polymer-based Pluronic nanocarrier containing anti-HIV drug called efavirenz (EFV) targeting Microfold cells (M-cells) in the GALT. M-cells are specialized epithelial cells that are predominantly present in the GALT. In this work, we have exploited this paracellular transport property of M-cells for targeted delivery of Pluronic nanocarrier tagged EFV, bioconjugated with anti-M-cell-specific antibodies to the GALT (nanodrug). Preliminary characterization showed that the nanodrug (EFV-F12-COOH) is of 140 nm size with 0.3 polydispersion index, and the zeta potential of the particles was −19.38±2.2 mV. Further, drug dissolution study has shown a significantly improved sustained release over free drugs. Binding potential of nanodrug with M-cell was also confirmed with fluorescence microscopy and in vitro uptake and release studies. The anti-HIV activity of the nanodrug was also significantly higher compared to that of free drug. This novel formulation was able to show sustained release of EFV and inhibit the HIV-1 infection in the GALT compared to the free drug. The present study has potential for our in vivo targeted nanodrug delivery system by combining traditional enteric-coated capsule technique via oral administration.

Imaging the lymphatic system

Visualization of the lymphatic system is clinically necessary during diagnosis or treatment of many conditions and diseases; it is used for identifying and monitoring lymphedema, for detecting metastatic lesions during cancer staging and for locating lymphatic structures so they can be spared during surgical procedures. Imaging lymphatic anatomy and function also plays an important role in experimental studies of lymphatic development and function, where spatial resolution and accessibility are better. Here, we review technologies for visualizing and imaging the lymphatic system for clinical applications. We then describe the use of lymphatic imaging in experimental systems as well as some of the emerging technologies for improving these methodologies.

Image-guided drug delivery to the brain using nanotechnology

Targeting across the blood-brain barrier (BBB) for treatment of central nervous system (CNS) diseases represents the most challenging aspect of, as well as one of the largest growing fields in, neuropharmaceutics. Combining nanotechnology with multiple imaging techniques has a unique role in the diagnosis and treatment (theranostics) of CNS disease. Such imaging techniques include anatomical imaging modalities, such as magnetic resonance imaging (MRI), ultrasound (US), X-ray computed tomography (CT), positron emission tomography (PET), single-photon emission computed tomography (SPECT), electron microscopy, autoradiography and optical imaging as well as thermal images. In this review, we summarize and discuss recent advances in formulations, current challenges and possible hypotheses concerning the use of such theranostics across the BBB.

Cholesterol derivatives based charged liposomes for doxorubicin delivery: preparation, in vitro and in vivo characterization

Cholesterol plays a critical role in liposome composition. It has great impact on the behavior of liposome in vitro and in vivo. In order to verify the possible effects from cholesterol charge, surface shielding and chemical nature, two catalogs of liposomes with charged and PEGylated cholesterols were synthesized. Anionic liposomes (AL) and cationic liposomes (CL) were prepared, with charges from hemisuccinate and lysine in cholesterol derivatives, respectively. Characteristics of different formulated liposomes were investigated after doxorubicin encapsulation, using neutral liposomes (NL) as control. Results showed that after PEGylation, AL and CL liposomes displayed prolonged retention release profile, while kept similar size distribution, encapsulation efficiency, low cytotoxicity and hemolysis comparing with NL. Confocal laser scanning microscopy and flow cytometry experiments confirmed the significantly higher cell uptake from AL and CL vesicles than the NL in mouse breast carcinoma and melanoma cells, human epithelial carcinoma and hepatoma cells. It was in accordance with our corresponding cellular mortality studies of DOX-loaded liposomes. The in vivo anti-tumor effect experiments from charged liposomes also presented much higher tumor inhibition effect (70% vs 45%, p < 0.05) than NL liposomes. This is the first time reporting anti-cancer effect from charged cholesterol liposome with/without PEGylation. It may give deeper understanding on the liposome formulation which is critical for liposome associated drug research and development.

Image guided biodistribution and pharmacokinetic studies of theranostics

Image guided technique is playing an increasingly important role in the investigation of the biodistribution and pharmacokinetics of drugs or drug delivery systems in various diseases, especially cancers. Besides anatomical imaging modalities such as computed tomography (CT), magnetic resonance imaging (MRI), molecular imaging strategy including optical imaging, positron emission tomography (PET) and single-photon emission computed tomography (SPECT) will facilitate the localization and quantization of radioisotope or optical probe labeled nanoparticle delivery systems in the category of theranostics. The quantitative measurement of the bio-distribution and pharmacokinetics of theranostics in the fields of new drug/probe development, diagnosis and treatment process monitoring as well as tracking the brain-blood-barrier (BBB) breaking through by high sensitive imaging method, and the applications of the representative imaging modalities are summarized in this review.

Mechanistic determinants of biotherapeutics absorption following SC administration

The subcutaneous (SC) route is of growing interest for the administration of biotherapeutics. Key products on the biotherapeutic market such as insulins, but also several immunoglobulins or Fc-fusion proteins, are administered SC. Despite the importance of the SC route, the available knowledge about the processes involved in the SC absorption of biotherapeutics is limited. This review summarizes available information on the physiology of the SC tissue and on the pharmacokinetic processes after SC administration including "first pass catabolism" at the administration site as well as transport in the extracellular matrix of the SC tissue, followed by absorption into the blood circulation or the lymphatic system. Both monoclonal antibodies and other biotherapeutics are discussed. Determinants of absorption after SC administration are summarized including compound properties such as charge or molecular weight. Scale-up of animal data to humans is discussed, including the current shortcomings of empirical scaling approaches and the lack of suitable mechanistic approaches.

Pharmacokinetics, lymph node uptake, and mechanistic PK model of near-infrared dye-labeled bevacizumab after IV and SC administration in mice

Our objective was to determine the pharmacokinetics, bioavailability and lymph node uptake of the monoclonal antibody bevacizumab, labeled with the near-infrared (IR) dye 800CW, after intravenous (IV) and subcutaneous (SC) administration in mice. Fluorescence imaging and enzyme-linked immunosorbent assay (ELISA) assays were developed and validated to measure the concentration of bevacizumab in plasma. The bevacizumab-IRDye conjugate remained predominantly intact in plasma and in lymph node homogenate samples over a 24-h period, as determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis and size exclusion chromatography. The plasma concentration vs. time plots obtained by fluorescence and ELISA measurements were similar; however, unlike ELISA, fluorescent imaging was only able to quantitate concentrations for 24 h after administration. At a low dose of 0.45 mg/kg, the plasma clearance of bevacizumab was 6.96 mL/h/kg after IV administration; this clearance is higher than that reported after higher doses. Half-lives of bevacizumab after SC and IV administration were 4.6 and 3.9 days, respectively. After SC administration, bevacizumab-IRDye800CW was present in the axillary lymph nodes that drain the SC site; lymph node uptake of bevacizumab-IRDye 800CW was negligible after IV administration. Bevacizumab exhibited complete bioavailability after SC administration. Using a compartmental pharmacokinetic model, the fraction absorbed through the lymphatics after SC administration was estimated to be about 1%. This is the first report evaluating the use of fluorescent imaging to determine the pharmacokinetics, lymphatic uptake, and bioavailability of a near-infrared dye-labeled antibody conjugate.