Sanja Koštrun

Intensity of macrolide anti-inflammatory activity in J774A.1 cells positively correlates with cellular accumulation and phospholipidosis

Some macrolide antibiotics were reported to inhibit interleukin-6 (IL6) and prostaglandin-E2 (PGE(2)) production by bacterial lipopolysaccharide (LPS) stimulated J774A.1 cells. Macrolides are also known to accumulate in cells and some were proven inducers of phospholipidosis. In the present study, with a set of 18 mainly 14- and 15-membered macrolides, we have investigated whether these macrolide induced phenomena in J774A.1 cells are connected. In LPS-stimulated J774A.1 cells, the extent of inhibition of proinflammatory markers (IL6 and PGE(2)) by macrolides significantly correlated with their extent of accumulation in cells, as well as with the induction of phospholipidosis, and cytotoxic effects in prolonged culture (with correlation coefficients (R) ranging from 0.78 to 0.93). The effects observed were related to macrolide binding to phospholipids (CHI IAM), number of positively charged centres, and were inversely proportional to the number of hydrogen bond donors. Similar interdependence of effects was obtained with chloroquine and amiodarone, whereas for dexamethasone and indomethacin these effects were not linked. The observed macrolide induced phenomena in J774A.1 cells were reversible and elimination of the macrolides from the culture media prevented phospholipidosis and the development of cytotoxicity in long-term cultures. Based on comparison with known clinical data, we conclude that LPS-stimulated J774A.1 cells in presented experimental setup are not a representative cellular model for the evaluation of macrolide anti-inflammatory potential in clinical trials. Nevertheless, our study shows that, at least in in vitro models, binding to biological membranes may be the crucial factor of macrolide mechanism of action.

Physicochemical profile of macrolides and their comparison with small molecules

Macrolides are stereospecific macrolactones of high molecular weights. Herein, 600 mostly semisynthetic macrolides are compared with 50,000 small non-macrolide synthetic molecules in terms of measured physicochemical properties in order to assess the drug-likeness and developability chances of macrolides. The pre-selected set of diverse macrolides is comprised mostly of derivatives of clarithromycin and azithromycin cores. Lipophilicity (CHI logD), affinity for immobilized artificial membranes (CHI IAM), human serum albumin (HSA) and α(1)-acid glycoprotein (AGP) plasma protein bindings (PPB), DMSO precipitative solubility as well as artificial membrane permeability (AMP) have been determined by high-throughput screening methods. It has been found that macrolides and small molecules have similar lipophilicity profiles, though macrolides show weaker PPB and have better solubility than small discovery molecules. However, macrolides are poorly permeable and have high affinity for immobilized artificial membranes signifying their strong interaction with biological phospholipids. In order to retain the drug-like profile, the design of novel macrolide molecules should be focused on optimisation of macrolide cores, that is macrolactone moiety with sugars and other small substituents avoiding large substituents and flexible linkers such as in conjugate derivatives.

Structure-property relationship for cellular accumulation of macrolones in human polymorphonuclear leukocytes (PMNs).

Macrolones are a new class of antimicrobial compounds consisting of a macrolide scaffold linked to a 4-quinolone-3-carboxylic acid moiety via C(4″) position of a macrolide. As macrolides are known to possess favorable pharmacokinetic properties by accumulating in inflammatory cells, in this study we determined the intensity of accumulation in human polymorphonuclear leukocytes (PMNs) of 57 compounds of the macrolone class and analyzed the relationship between the molecular structure and this cellular pharmacokinetic property. Accumulation of macrolones ranged from 0 to 5.5-fold higher than the standard macrolide azithromycin. Distinct structural features in all three considered molecule parts: the macrolide scaffold, quinolone moiety and the linker, affect cellular accumulation. Interestingly, while the parent macrolide, azithromycin, accumulates approximately 3-fold more than clarithromycin, among macrolones all clarithromycin derivatives accumulated in PMNs significantly more than their azithromycin counterparts. Modeling cellular accumulation of macrolones with simple molecular descriptors, as well as with the measured octanol-water distribution coefficient, revealed that the number of hydrogen bond donors and secondary amide groups negatively contribute to macrolone accumulation, while lipophilicity makes a positive contribution.

Around the macrolide – Impact of 3D structure of macrocycles on lipophilicity and cellular accumulation

The aim of this study was to investigate lipophilicity and cellular accumulation of rationally designed azithromycin and clarithromycin derivatives at the molecular level. The effect of substitution site and substituent properties on a global physico-chemical profile and cellular accumulation of investigated compounds was studied using calculated structural parameters as well as experimentally determined lipophilicity. In silico models based on the 3D structure of molecules were generated to investigate conformational effect on studied properties and to enable prediction of lipophilicity and cellular accumulation for this class of molecules based on non-empirical parameters. The applicability of developed models was explored on a validation and test sets and compared with previously developed empirical models.

Current Trends in Macrocyclic Drug Discovery and beyond-Ro5

This chapter will discuss the recent literature of macrocycles and drug-like property space moving beyond the rule of five (bRo5). Trends in chemical classes that fall within this definition are discussed and the impact of the latest technologies in the field assessed. The physicochemical properties, which have provided both successes and challenges, especially in scale-up, are discussed. A recent patent literature is reviewed and the chapter concludes with a perspective on the future of macrocyclic drug discovery.