Hydrolytic stability of anticancer drugs and one metabolite in the aquatic environment

Development of hydrolytic stability screening methods for early drug discovery with high differentiation and predictive power

In early drug discovery, hydrolytic chemical stability is routinely assessed to ensure future developability of quality compounds and stability in in vitro test environments. When conducting high-throughput hydrolytic stability analyses as part of the compound risk assessment, aggressive conditions are typically applied to allow for faster screening. However, it can be challenging to extrapolate the real stability risk and to rank compounds due to over-estimating risk based on aggressive conditions and the narrow discriminative window. In this study, critical assay parameters including temperature, concentration, and detection technique were systematically assessed using selected model compounds, and the impact and interplay of these parameters on predictive power and prediction quality were evaluated. Improved data quality was achieved using high sample concentration and reduced temperature, combined with ultraviolet (UV) detection, while mass spectrometry (MS) detection was found to be a useful complementary detection technique. Therefore, a highly discriminative stability protocol with optimized assay parameters and experimental data quality is proposed. The optimized assay can provide early guidance on the potential stability risk of a drug molecule as well as enable more confident decision-making in compound design, selection, and development.

Sub-50 nm core-shell nanoparticles with the pH-responsive squeezing release effect for targeting therapy of hepatocellular carcinoma

The development of drug delivery systems with high drug loading capacity, low leakage at physiological pH, and rapid release at the lesion sites remains an ongoing challenge. In this work, core-shell poly(6-O-methacryloyl-D-galactose)@poly(tert-butyl methacrylate) (PMADGal@PtBMA) nanoparticles (NPs) of sub-50 nm are facilely synthesized by reversible addition-fragmentation chain transfer (RAFT) soap-free emulsion polymerization with the assistance of 12-crown-4. A hydrophilic poly(methacrylic acid) (PMAA) core can then be revealed after deprotection of the tert-butyl groups, which is negatively charged and can adsorb nearly 100% of incubated doxorubicin (DOX) from a solution at pH 7.4. The physical shrinkage of PMAA chains below pH 6.0 endows the core with the squeezing effect, therefore realizing rapid drug release. It is demonstrated that the DOX release rate of PMADGal@PMAA NPs at pH 5 was 4 times that at pH 7.4. Cellular uptake experiments confirm the high targeting ability of the galactose modified PMADGal shell to human hepatocellular carcinoma (HepG2) cells. The fluorescence intensity of DOX in HepG2 cells is 4.86 times that of HeLa cells after 3 h incubation. Moreover, 20% cross-linked NPs show the highest uptake efficiency by HepG2 cells due to their moderate surface charge, size and hardness. In summary, both the core and the shell of PMADGal@PMAA NPs promise the rapid site-specific release of DOX in HepG2 cells. This work provides a facile and an effective strategy to synthesize core-shell NPs for hepatocellular carcinoma targeting therapy.

Anticancer Drugs: Recent Strategies to Improve Stability Profile, Pharmacokinetic and Pharmacodynamic Properties

In past decades, anticancer research has led to remarkable results despite many of the approved drugs still being characterized by high systemic toxicity mainly due to the lack of tumor selectivity and present pharmacokinetic drawbacks, including low water solubility, that negatively affect the drug circulation time and bioavailability. The stability studies, performed in mild conditions during their development or under stressing exposure to high temperature, hydrolytic medium or light source, have demonstrated the sensitivity of anticancer drugs to many parameters. For this reason, the formation of degradation products is assessed both in pharmaceutical formulations and in the environment as hospital waste. To date, numerous formulations have been developed for achieving tissue-specific drug targeting and reducing toxic side effects, as well as for improving drug stability. The development of prodrugs represents a promising strategy in targeted cancer therapy for improving the selectivity, efficacy and stability of active compounds. Recent studies show that the incorporation of anticancer drugs into vesicular systems, such as polymeric micelles or cyclodextrins, or the use of nanocarriers containing chemotherapeutics that conjugate to monoclonal antibodies can improve solubility, pharmacokinetics, cellular absorption and stability. In this study, we summarize the latest advances in knowledge regarding the development of effective highly stable anticancer drugs formulated as stable prodrugs or entrapped in nanosystems.

Photodegradation of methotrexate in aqueous solution: degradation kinetics and identification of transformation products

Methotrexate is an antineoplastic folate analog of high environmental concern, due to its low biodegradability and toxicological properties. This study focused on its photodegradation under two irradiation conditions, aiming to be representative of environment (300-450 nm) and drinking water treatment (254 nm). The photodegradation experiments were conducted at two pH, to vary the methotrexate ionization state and to produce a large variety of transformation products (TPs). The degradation kinetics determined through LC-UV monitoring were contrasted according to pH and irradiation wavelength. However, the quantum yields were independent of ionization state at 254 nm and the changes in kinetics at higher wavelengths were attributed to a change in the degradation mechanism. The TPs formed during the reactions were identified by UHPLC-MS/MS, using both the positive and negative modes. Among the eleven proposed structures, five were described as methotrexate TPs for the first time. The TPs result from N-demethylation, glutamic acid oxidation, and C-N cleavage, all of them leading to further degraded photoproducts presenting modified or lost glutamic acid part. This was made possible thanks to the negative mode, which allowed the exploration of the glutamic acid moiety modifications. Cytotoxicity assessment on A549 cancer cells demonstrated that all photoproducts formed at pH 7 were less toxic than the parent compound.