John J. Baldwin

Discovery of VTP-27999, an Alkyl Amine Renin Inhibitor with Potential for Clinical Utility.

Structure guided optimization of a series of nonpeptidic alkyl amine renin inhibitors allowed the rational incorporation of additional polar functionality. Replacement of the cyclohexylmethyl group occupying the S1 pocket with a (R)-(tetrahydropyran-3-yl)methyl group and utilization of a different attachment point led to the identification of clinical candidate 9. This compound demonstrated excellent selectivity over related and unrelated off-targets, >15% oral bioavailability in three species, oral efficacy in a double transgenic rat model of hypertension, and good exposure in humans.

Design, synthesis and use of binary encoded synthetic chemical libraries

SummaryWith the advent of combinatorial chemistry a new paradigm is evolving in the field of drug discovery. The approach is based on an integration of chemistry, high-throughput screening and automation engineering. The chemistry arm is usually based on solid-phase synthesis technology as the preferred approach to library construction. One of the most powerful of the solid-phase methods is encoded split synthesis, in which the reaction history experience by each polymeric bead is unambiguously recorded. This split-and-pool approach, employing chemically robust tags, was used to construct a 85 000-membered dihydrobenzopyran library.

Small molecule antagonists of the bradykinin B1 receptor.

Screening Pharmacopeias encoded combinatorial libraries has led to the identification of potent, selective, competitive antagonists at the bradykinin B1 receptor. Libraries were screened using a displacement assay of [3H]-des-Arglo-kallidin ([3H]-dAK) at IMR-90 cells expressing an endogenous human B1 receptor (Bmax = 20,000 receptors/cell, K(D) = 0.5+/-0.1 nM) or against membranes from 293E cells expressing a recombinant human B1 receptor (Bmax = 8,000 receptors/cell, K(D) = 0.5 +/- 0.3 nM). Compound PS020990, an optimized, representative member from the class of compounds, inhibits specific binding of 3H-dAK at IMR-90 cells with a KI of 6 +/- 1 nM. The compound inhibits dAK-induced phosphatidyl inositol turnover (K(Bapp) = 0.4 +/- 0.2 nM) and calcium mobilization (K(Bapp) = 17 +/- 2 nM) in IMR-90 cells. Compounds from the lead series are inactive at the B2 receptor and are > 1000-fold specific for B1 vs. a variety of other receptors, ion channels and enzymes. PS020990 and other related chemotypes therefore offer an excellent opportunity to explore further the role of B1 receptors in disease models and represent a potential therapeutic avenue.

Design and Optimization of Renin Inhibitors: Orally Bioavailable Alkyl Amines

Structure-based drug design led to the identification of a novel class of potent, low MW alkylamine renin inhibitors. Oral administration of lead compound 21l, with MW of 508 and IC(50) of 0.47nM, caused a sustained reduction in mean arterial blood pressure in a double transgenic rat model of hypertension.

Optimization of orally bioavailable alkyl amine renin inhibitors.

Structure-guided drug design led to new alkylamine renin inhibitors with improved in vitro and in vivo potency. Lead compound 21a, has an IC(50) of 0.83nM for the inhibition of human renin in plasma (PRA). Oral administration of 21a at 10mg/kg resulted in >20h reduction of blood pressure in a double transgenic rat model of hypertension.

III. Identification of novel CXCR3 chemokine receptor antagonists with a pyrazinyl-piperazinyl-piperidine scaffold.

The SAR of a novel pyrazinyl-piperazinyl-piperidine scaffold with CXCR3 receptor antagonist activity was explored. Optimization of the DMPK profile and reduction of hERG inhibition is described. Compound 16e with single-digit CXCR3 affinity, good rat PK and hERG profiles has been identified as a lead for further study.

Binary encoded small-molecule libraries in drug discovery and optimization

A variety of small-molecule combinatorial libraries have been prepared on solid support using a binary encoding strategy employing non-sequenceable encoding molecules. Library members are attached to the support using photolabile linkers which permit their release for assay free in solution. The encoding molecules are attached using a carbene insertion reaction and are released via oxidation. A wide variety of synthetic reactions have been utilized for library synthesis including, for example, cyclocondensations, reductive aminations, and heteroaromatic halide displacements, as well as acylations and sulfonylations. Initial screening of two such libraries identified lead structures for the inhibition of carbonic anhydrase. Subsequently, based upon these leads a smaller focused combinatorial library was constructed and used to analyze the structure-activity relationships (SARs) governing enzyme inhibition and isozyme selectivity. The combination of random screening with a broad diversity of compounds, followed by focused libraries for detailed SARs and selectivity, demonstrates the power of binary encoded small-molecule combinatorial libraries for drug discovery.

2 - Combinatorial Chemistry and High-Throughput Screening in Drug Discovery and Development

Combinatorial chemistry is a synthesis strategy that enables the simultaneous production of large numbers of related compounds. It is coupled to high-throughput screening (HTS) and computational methods and has been integrated into the lead discovery and optimization process throughout the pharmaceutical industry. Innovations in combinatorial chemistry have enabled the synthesis of large collections of libraries, which have led to the current efforts in developing methods capable of screening these compounds. The general synthetic strategy used for combinatorial chemistry is similar to the more classical approach, that is, commercial synthons or building blocks are combined through a range of usually established methods to generate a new entity. The combinatorial approach differs in that the reactions are generalized for a range of building blocks, so that a related set of compounds are simultaneously produced. As computational and experimental procedures for absorption, distribution, metabolism, and excretion (ADME) improve, the identification of problematic leads earlier in the drug discovery process will be possible. Taken together, innovations in chemical synthesis and library design, coupled with screening and bioinformatics technology, will help greatly to decrease drug development times and costs.

Biphenyl/diphenyl ether renin inhibitors: Filling the S1 pocket of renin via the S3 pocket

Structure-based design led to the discovery of a novel class of renin inhibitors in which an unprecedented phenyl ring filling the S1 site is attached to the phenyl ring filling the S3 pocket. Optimization for several parameters including potency in the presence of human plasma, selectivity against CYP3A4 inhibition and improved rat oral bioavailability led to the identification of 8d which demonstrated antihypertensive efficacy in a transgenic rat model of human hypertension.

Deconvolution methods in solid-phase synthesis

The word library is used to define a collection of compounds usually built around a common structural motif. There are three general approaches to library preparation: parallel synthesis, mixture synthesis and split synthesis. One of these preferred strategies, parallel synthesis, is the approach where the compounds are made individually by automated or semi-automated methods. The library members may be made either in solution by classical methods, in solution attached to a polymeric carrier or on solid support. In parallel synthesis there must be linkage to a spatially defined position. The structure of the product is inferred from the position of the reactor and by the order of addition of the synthons and reagents at that position in space. Every possible member, resulting from the combinatorial mix of the synthons, need not be included in the library.