Polyethylene glycol-based linkers as hydrophilicity reservoir for antibody-drug conjugates.

Antibody-drug conjugates (ADCs) are an established therapeutic entity in which potent cytotoxic drugs are conjugated to a monoclonal antibody. In parallel with the great emphasis put on novel site-specific bioconjugation technologies, future advancements in this field also rely on exploring novel linker-drug architectures that improve the efficacy and stability of ADCs. In this context, the use of hydrophilic linkers represents a valid strategy to mask or reduce the inherent hydrophobicity of the most used cytotoxic drugs and positively impact the physical stability and in vivo performance of ADCs. Here, we describe the use of linkers containing monodisperse poly(ethylene glycol) (PEG) moieties for the construction of highly-loaded lysine-conjugated ADCs. The studied ADCs differ in the positioning of PEG (linear or pendant), the bonding type with the antibody (amide or carbamate), and the drug-to-antibody ratio (DAR). These ADCs were first evaluated for their stability in solution under thermal stress, showing that both the drug-linker-polymer design and the nature of the antibody-linker bonding are of great importance for their physical and chemical stability. Amide-coupled ADCs bearing two pendant 12-unit poly(ethylene glycol) chains within the drug-linker structure were the best performing conjugates, distancing themselves from the ADCs obtained with a conventional linear 24-unit PEG oligomer or the linker of Kadcyla®. The pharmacokinetic profiles of amide-linked ADCs, with a linear or pendant configuration of the PEG, were tested in mice in comparison to Kadcyla®. Total antibody pharmacokinetics paralleled the trends in aggregation tendency, with slower clearance rates for the ADCs based on the pendant drug-linker format. The above-mentioned findings have provided important clues on the drug-linker design and revealed that the positioning and configuration of a PEG unit have to be carefully tuned to achieve ADCs with improved stability and pharmacokinetics.

Poly(ethylene glycol)-mesalazine conjugate for colon specific delivery.

Chronic inflammatory bowel diseases (IBDs) are still waiting for improved and innovative therapeutic treatments, which can overcome the limits of the current approaches. Since IBDs affect mainly the lower tract of the intestine, a localized therapy in the colon tract will avoid most of the problems caused by systemic or poor selective therapies. Particularly promising are the advance drug delivery systems that can reach specific colon delivery, thus guaranteeing active agent release only at the site of action. This approach can meet two aims at the same time, first of all the drug will not affect healthy tissue and second a lower drug dose may be used because all the administered active agent will reach the target. To obtain a specific colon delivery we exploited the azoreductase enzymes, selectively present only in colon, by inserting an azo linker between a selected drug and a macromolecular carrier. The drug employed is mesalazine, a well know and used agent against IBDs. Poly(ethylene glycol) (PEG), of different molecular weights and structures, was used as carrier. Three different conjugates were synthesized and characterized, and the most promising one, with highest drug loading thanks to the use of diamino PEG of 4 kDa, was further investigated in vitro on mouse colonic epithelial cells (CMT-9) and in vivo on model mice with induced colitis. The data presented here demonstrate that PEG conjugation of mesalazine prevents drug release and absorption in upper intestine, after oral administration of the conjugates, and that the azo linker ensures a good drug release in the colon tract. The results in vivo take into consideration mice bodyweight gain, tissue histology and interleukin-2 beta as an index of inflammation. These parameters, all together, demonstrated the conjugate effectiveness against the controls.

Polyethylene glycol and a novel developed polyethylene glycol-nitric oxide normalize arteriolar response and oxidative stress in ischemia-reperfusion.

Polyethylene glycol (PEG) has been shown to repair cell membranes and, thus, inhibit free radical production in in vitro and in vivo models. We hypothesized that PEG and newly developed organic nitrate forms of PEG (PEG-NO) could repair endothelial dysfunction in ischemia-reperfusion (I/R) injury in the hamster cheek pouch visualized by intravital fluorescent microscopy. After treatments, we evaluated diameter and RBC velocity and flow in arterioles, as well as lipid peroxides in the systemic blood, perfused capillary length, vascular permeability, leukocyte adhesion, and amount of von Willebrand factor (vWF) in the blood after I/R injury. A control group was treated with 5,000- or 10,000-Da PEG, and three groups were treated with PG1 (1 NO molecule covalently bound to PEG, 5,170 Da), PG8 (8 NO molecules covalently bound to PEG, 11,860 Da), and PG16 (16 NO molecules covalently bound to PEG, 14,060 Da). All animals received 0.5 mg/0.5 ml. Lipid peroxides increased at 5 and 15 min of reperfusion, whereas diameter, RBC velocity, and blood flow decreased in arterioles after I/R injury. Vascular permeability, leukocyte adhesion, and vWF increased significantly. PEG and PG1 attenuated lipid peroxides and vasoconstriction during reperfusion and decreased leukocyte adhesion and vascular permeability. PG8 maintained lipid peroxides at normal levels, increased arteriolar diameter, flow, and perfused capillary length, and decreased vWF level and leukocyte adhesion (P < 0.05). PG16 was less effective than PG1 and PG8. In conclusion, PEG-NO shows promise as a compound that protects microvascular perfusion by normalizing the balance between NO level and excessive production of free radicals in endothelial cells during I/R injury.

PEG-Ara-C conjugates for controlled release.

The antitumour agent 1-beta-D arabinofuranosilcytosyne (Ara-C) was covalently linked to poly(ethylene glycol) (PEG) in order to improve the in vivo stability and blood residence time. Eight PEG conjugates were synthesised, with linear or branched PEG of 5000, 10000 and 20000 Da molecular weight through an amino acid spacer. Starting from mPEG-OH or HO-PEG-OH, conjugation was carried out to the one or two available hydroxyl groups at the polymer's extreme. Furthermore, to increase the drug loading of the polymer, the hydroxyl functions of PEG were functionalised with a bicarboxylic amino acid yielding a tetrafunctional derivative and, by recursive conjugation with the same bicarboxylic amino acid, products with four or eight Ara-C molecules for each PEG chain were prepared. A computer graphic investigation demonstrated that aminoadipic acid was a suitable bicarboxylic amino acid to overcome the steric hindrance between the vicinal Ara-C molecules in the dendrimeric structure. In this paper we report the optimised conditions for synthesis and purification of PEG-Ara-C products with a low amount of remaining free drug, studies toward the hydrolysis of PEG-Ara-C and the Ara-C deamination by cytidine deaminase, pharmacokinetics in mice and cytotoxicity towards HeLa human cells were also investigated. Increased stability towards degradation of the conjugated Ara-C products, in particular for the highly loaded ones, improved blood residence time in mice and a reduced cytotoxicity with respect to the free Ara-C form was demonstrated.

Public health in Canada: a comparative study of six provinces.

PURPOSE: To describe the public health systems and their projected futures in six provinces in the context of two developments: 1) the emerging discourse on population health and 2) the trend toward regionalization of the health care system. METHODS: Telephone interviews with key informants and key document review. RESULTS AND CONCLUSIONS: Communicable disease control and health protection are currently the "core businesses" of public health; the population health discourse has not resulted in mandated programming. The reality is a retrenchment of public health scope during a time that should be considered conducive to expansion. Only Ontario has not regionalized its health care system, although public health is already delivered regionally. Alberta, Saskatchewan and Manitoba have either evolved or are evolving toward an integrated health system. There were concerns about the potential impact on public health identity and funding of this "vertical integration". Regionalization of public health may result in units that are too small to support adequate local expertise and may jeopardize development and enforcement of province-wide programs.

Evaluation of the audioscope in an industrial setting.

In this study, the findings of a 25 dB hearing level Welch Allyn Audioscope test at 0.5, 1, 2, 4 kHz were compared with the standard of conventional pure-tone audiometry in 228 newly hired construction workers. The sensitivity for all frequency-specific comparisons combined was found to be lower than in previous studies done in a nonoccupational setting. After correction for sampling bias, the specificity for all frequencies combined was well within the range reported in other studies. Only 1.9% of ears (1/53) that were able to hear all four audioscope frequencies were found by conventional audiometry to have clinically important hearing loss defined as a 25 dB hearing level averaged over the speech frequencies. Hence, the audioscope can be used as a rapid initial test in workers who otherwise would not have access to hearing screening.