Enhancing the Safety and Efficacy of PSMA-Based Small-Molecule Drug Conjugates by Linker Stabilization and Conjugation to Transthyretin Binding Ligand.

This work describes the enhancement of a novel antitumor therapeutic platform that combines advantages from small-molecule drug conjugates (SMDCs) and antibody drug conjugates (ADCs). Valine-citrulline (VCit) dipeptide linkers are commonly used cathepsin B cleavable linkers for ADCs. However, the instability of these linkers in mouse serum makes translating efficacy data from mouse to human more challenging. Replacing the VCit linker with glutamic acid-valine-citrulline (EVCit) has been reported to enhance the stability of ADCs in mouse serum. However, the effect of EVCit linker on the stability of SMDCs has not been reported. Here, we report that incorporating the EVCit linker in prostate-specific membrane antigen-targeting SMDCs, equipped with the transthyretin ligand AG10, resulted in conjugates with lower toxicity, an extended half-life, and superior therapeutic efficacy to docetaxel in a xenograft mouse model of prostate cancer. This should make SMDCs' preclinical toxicity and efficacy data from mice more reliable for predicting human results.

Peripherally restricted transthyretin-based delivery system for probes and therapeutics avoiding opioid-related side effects.

Several investigations into the sites of action of opioid analgesics have utilized peripherally acting mu-opioid receptor antagonists (PAMORAs), which have been incorrectly assumed to possess limited permeability across the blood-brain barrier. Unfortunately, the poor pharmacokinetic properties of current PAMORAs have resulted in misunderstandings of the role of central nervous system and gastrointestinal tract in precipitating side effects such as opioid-induced constipation. Here, we develop a drug delivery approach for restricting the passage of small molecules across the blood-brain barrier. This allows us to develop naloxone- and oxycodone-based conjugates that display superior potency, peripheral selectivity, pharmacokinetics, and efficacy in rats compared to other clinically used PAMORAs. These probes allow us to demonstrate that the mu-opioid receptors in the central nervous system have a fundamental role in precipitating opioid-induced constipation. Therefore, our conjugates have immediate use as pharmacological probes and potential therapeutic agents for treating constipation and other opioid-related side effects.

Comparison of the cardiac effects of electronic cigarette aerosol exposure with waterpipe and combustible cigarette smoke exposure in rats.

AIMS: Electronic cigarette (ECIG) has been used as an alternative to tobacco smoking as it lacks the majority of toxicants found in tobacco smoke. However, the effect of ECIG aerosol inhalation on cardiac health are not well studied. The present study aimed to compare the effects of ECIGs with that of combustible tobacco cigarette (T-Cigs) and waterpipe (WP) smoke on cardiac biomarkers of oxidative stress, inflammation, and fibrosis. MAIN METHODS: Rats were randomized into control (fresh air, n = 12), ECIG aerosol (n = 12), T-Cig smoke (n = 15), or WP (n = 13) smoke conditions in which they were exposed 1 h/daily, 6 day/week for 4 weeks. Cardiac biomarkers of oxidative stress, inflammation, and remodeling were assessed. KEY FINDINGS: Relative to control, significant increase in heart to body weight ratio was observed in all exposed groups. Cardiac endothelin-1 and myeloperoxidase were increased for ECIG and T-Cig. Cardiac nitrite and TBARS were increased in all exposed groups, but activity of superoxide dismutase was increased for ECIG and T-Cig only while glutathione levels increased for ECIG only. No changes were observed for cardiac C-reactive protein and catalase activity. Cardiac fibrosis was observed in all exposed groups coupled with an increase in the transforming growth factor beta protein that was significant for ECIG only. SIGNIFICANCE: ECIG aerosol may promote cardiac alterations in similar manner to tobacco smoke by promoting myocardial oxidative stress and inflammation leading to fibrosis. With regard to cardiac health, exposure to ECIG aerosol and combustible T-Cig smoke may lead to similar adverse outcomes.