The medicinal chemistry community has become increasingly aware of the value of tracking calculated physical properties such as molecular weight, topological polar surface area, rotatable bonds, and hydrogen bond donors and acceptors. We hypothesized that the shift to high-throughput synthetic practices over the past decade may be another factor that may predispose molecules to fail by steering discovery efforts toward achiral, aromatic compounds. We have proposed two simple and interpretable measures of the complexity of molecules prepared as potential drug candidates. The first is carbon bond saturation as defined by fraction sp3 (Fsp3) where Fsp3 = (number of sp3 hybridized carbons/total carbon count). The second is simply whether a chiral carbon exists in the molecule. We demonstrate that both complexity (as measured by Fsp3) and the presence of chiral centers correlate with success as compounds transition from discovery, through clinical testing, to drugs. In an attempt to explain these observations,...

Escape from flatland: increasing saturation as an approach to improving clinical success.

http://csmres.co.uk/cs.public.upd/article-downloads/Synthetic-therapeutic-peptides-science-and-market.pdf

Synthetic therapeutic peptides: science and market.

The neurons of the central nervous system (CNS) require precise control of their bathing microenvironment for optimal function, and an important element in this control is the blood–brain barrier (BBB). The BBB is formed by the endothelial cells lining the brain microvessels, under the inductive influence of neighbouring cell types within the ‘neurovascular unit’ (NVU) including astrocytes and pericytes. The endothelium forms the major interface between the blood and the CNS, and by a combination of low passive permeability and presence of specific transport systems, enzymes and receptors regulates molecular and cellular traffic across the barrier layer. A number of methods and models are available for examining BBB permeation in vivo and in vitro, and can give valuable information on the mechanisms by which therapeutic agents and constructs permeate, ways to optimize permeation, and implications for drug discovery, delivery and toxicity. For treating lysosomal storage diseases (LSDs), models can be included that mimic aspects of the disease, including genetically-modified animals, and in vitro models can be used to examine the effects of cells of the NVU on the BBB under pathological conditions. For testing CNS drug delivery, several in vitro models now provide reliable prediction of penetration of drugs including large molecules and artificial constructs with promising potential in treating LSDs. For many of these diseases it is still not clear how best to deliver appropriate drugs to the CNS, and a concerted approach using a variety of models and methods can give critical insights and indicate practical solutions.

Blood-brain barrier structure and function and the challenges for CNS drug delivery.

Diseases of infection, of neurodegeneration (such as Alzheimer’s and Parkinson’s diseases), and of malignancy (cancers) have complex and varied causative factors. Modern drug discovery has the power to identify potential modulators for multiple targets from millions of compounds. Computational approaches allow the determination of the association of each compound with its target before chemical synthesis and biological testing is done. These approaches depend on the prior identification of clinically and biologically validated targets. This Perspective will focus on the molecular and computational approaches that underpin drug design by medicinal chemists to promote understanding and collaboration with clinical scientists.

/pdf/a-perspective-on-multi-target-drug-discovery-and-design-for-fi1sy4qsss.pdf

A perspective on multi-target drug discovery and design for complex diseases

The human brain is a uniquely complex organ, which has evolved a sophisticated protection system to prevent injury from external insults and toxins. Designing molecules that can overcome this protection system and achieve optimal concentration at the desired therapeutic target in the brain is a specific and major challenge for medicinal chemists working in CNS drug discovery. Analogous to the now widely accepted rule of 5 in the design of oral drugs, the physicochemical properties required for optimal brain exposure have been extensively studied in an attempt to similarly define the attributes of successful CNS drugs and drug candidates. This body of work is systematically reviewed here, with a particular emphasis on the interplay between the most critical physicochemical and pharmacokinetic parameters of CNS drugs as well as their impact on medicinal chemistry strategies toward molecules with optimal brain exposure. A summary of modern CNS pharmacokinetic concepts and methods is also provided.

CNS drug design: balancing physicochemical properties for optimal brain exposure.

Fundamental physiochemical features of CNS drugs are related to their ability to penetrate the blood-brain barrier affinity and exhibit CNS activity. Factors relevant to the success of CNS drugs are reviewed. CNS drugs show values of molecular weight, lipophilicity, and hydrogen bond donor and acceptor that in general have a smaller range than general therapeutics. Pharmacokinetic properties can be manipulated by the medicinal chemist to a significant extent. The solubility, permeability, metabolic stability, protein binding, and human ether-ago-go-related gene inhibition of CNS compounds need to be optimized simultaneously with potency, selectivity, and other biological parameters. The balance between optimizing the physiochemical and pharmacokinetic properties to make the best compromises in properties is critical for designing new drugs likely to penetrate the blood brain barrier and affect relevant biological systems. This review is intended as a guide to designing CNS therapeutic agents with better drug-like properties.

https://link.springer.com/content/pdf/10.1602/neurorx.2.4.541.pdf

George R. Lenz

Papers

Medicinal chemical properties of successful central nervous system drugs.