The design,synthesis and structure-activity relationships associated with C28 amine-based betulinic acid derivatives as inhibitors of HIV-1 maturation

The design and synthesis of a series of C28 amine-based betulinic acid derivatives as HIV-1 maturation inhibitors is described. This series represents a continuation of efforts following on from previous studies of C-3 benzoic acid-substituted betulinic acid derivatives as HIV-1 maturation inhibitors (MIs) that were explored in the context of C-28 amide substituents. Compared to the C-28 amide series, the C-28 amine derivatives exhibited further improvements in HIV-1 inhibitory activity toward polymorphisms in the Gag polyprotein as well as improved activity in the presence of human serum. However, plasma exposure of basic amines following oral administration to rats was generally low, leading to a focus on moderating the basicity of the amine moiety distal from the triterpene core. The thiomorpholine dioxide (TMD) 20 emerged from this study as a compound with the optimal antiviral activity and an acceptable pharmacokinetic profile in the C-28 amine series. Compared to the C-28 amide 3, 20 offers a 2- to 4-fold improvement in potency towards the screening viruses, exhibits low shifts in the EC₅₀ values toward the V370A and ΔV370 viruses in the presence of human serum or human serum albumin, and demonstrates improved potency towards the polymorphic T371A and V362I virus variants.     

Structure-based design and synthesis of macrocyclic human rhinovirus 3C protease inhibitors

The design and synthesis of macrocyclic inhibitors of human rhinovirus 3C protease is described. A macrocyclic linkage of the P1 and P3 residues, and the subsequent structure-based optimization of the macrocycle conformation and size led to the identification of a potent biochemical inhibitor 10 with sub-micromolar antiviral activity.     

Structure-activity relationship study of a series of caspase inhibitors containing γ-amino acid moiety for treatment of cholestatic liver disease

A series of caspase inhibitors containing γ-amino acid moiety have been synthesized. A systemic study on their structure-activity relationship of anti-apoptotic cellular activity is presented. These efforts led to the discovery of compound 20o as a potent caspase inhibitor, which demonstrated preclinical ameliorating total bilirubin efficacy with a significantly improved pharmacokinetic profile.     

Synthesis and evaluation of a ring-constrained Hsp90 C-terminal inhibitor that exhibits neuroprotective activity

KU-596 is a second-generation C-terminal heat shock protein 90 KDa (Hsp90) modulator based on the natural product, novobiocin. KU-596 has been shown to induce Hsp70 levels and manifest neuroprotective activity through induction of the heat shock response. A ring-constrained analog of KU-596 was designed and synthesized to probe its binding orientation and ability to induce Hsp70 levels. Compound 2 was found to exhibit comparable or increased activity compared to KU-596, which is under clinical investigation for the treatment of neuropathy.     

Small molecule inhibitors of anthrax edema factor

Anthrax is a highly lethal disease caused by the Gram-(+) bacteria Bacillus anthracis. Edema toxin (ET) is a major contributor to the pathogenesis of disease in humans exposed to B. anthracis. ET is a bipartite toxin composed of two proteins secreted by the vegetative bacteria, edema factor (EF) and protective antigen (PA). Our work towards identifying a small molecule inhibitor of anthrax edema factor is the subject of this letter. First we demonstrate that the small molecule probe 5′-Fluorosulfonylbenzoyl 5′-adenosine (FSBA) reacts irreversibly with EF and blocks enzymatic activity. We then show that the adenosine portion of FSBA can be replaced to provide more drug-like molecules which are up to 1000-fold more potent against EF relative to FSBA, display low cross reactivity when tested against a panel of kinases, and are nanomolar inhibitors of EF in a cell-based assay of cAMP production.     

Effects of newly synthetized isoquinoline derivatives on rat uterine contractility and ROCK II activity

Protein kinases have an important role in signal transduction in the cellular system via protein phosphorylation. RhoA activated Rho-kinases have a pivotal role in the regulation of smooth muscle contraction. ROCK I and ROCK II phosphorylate myosin-phosphatase and myosin-kinase, which induces contraction in the myometrium. Several studies have investigated the affinity of isoquinoline alkaloids (HA-1077, H1152P) to Rho-kinases, and these compounds notably inhibited the Ca²⁺-independent process.We measured the efficiency of 25 original, newly synthesized isoquinoline derivatives for the Rho-kinase activity using Rho-associated kinase activity assay and determined their effects on the non-pregnant, 20-day pregnant and parturient rat myometrial contraction in vitro.The IC₅₀ values of 11 from among the 25 derivatives were significantly lower on the oxytocin-induced non-pregnant rat uterine contraction compared with Y-27632 and fasudil, although their maximal inhibitory effects were weaker than those of Y-27632 and fasudil. We measured the effects of 11 isoquinoline molecules with significant IC₅₀ values on ROCK II activity. We found two isoquinolines out of 11 compounds (218 and 852) which decreased the active ROCK II level similarly as Y-27632. Then we found that 218 and 852 relaxed the 20th-day pregnant and parturient rat uterus with greater potency as compared with fasudil.The majority of the synthesized isoquinoline derivatives have uterus relaxant effects and two of them significantly suppress the Rho-kinase mediated myosin light chain phosphorylation. Our results may suggest that the isoquinoline structure has a promising prospect for the development of new and effective inhibitors of uterine contractions in preterm birth.     

Clickable photoaffinity ligands for the human serotonin transporter based on the selective serotonin reuptake inhibitor (S)-citalopram

To date, the development of photoaffinity ligands targeting the human serotonin transporter (hSERT), a key protein involved in disease states such as depression and anxiety, have been radioisotope-based (i.e., ³H or ¹²⁵I). This letter instead highlights three derivatives of the selective serotonin reuptake inhibitor (SSRI) (S)-citalopram that were rationally designed and synthesized to contain a photoreactive benzophenone or an aryl azide for protein target capture via photoaffinity labeling and a terminal alkyne or an aliphatic azide for click chemistry-based proteomics. Specifically, clickable benzophenone-based (S)-citalopram photoprobe 6 (hSERT K_i?=?0.16?nM) displayed 11-fold higher binding affinity at hSERT when compared to (S)-citalopram (hSERT K_i?=?1.77?nM), and was subsequently shown to successfully undergo tandem photoaffinity labeling-biorthogonal conjugation using purified hSERT. Given clickable photoprobes can be used for various applications depending on which reporter is attached by click chemistry subsequent to photoaffinity labeling, photoprobe 6 is expected to find value in structure-function studies and other research applications involving hSERT (e.g., imaging).     

Discovery of heterocyclic replacements for the coumarin core of anti-tubercular FadD32 inhibitors

Previous work established a coumarin scaffold as a starting point for inhibition of Mycobacterium tuberculosis (Mtb) FadD32 enzymatic activity. After further profiling of the coumarin inhibitor 4 revealed chemical instability, we discovered that a quinoline ring circumvented this instability and had the advantage of offering additional substitution vectors to further optimize. Ensuing SAR studies gave rise to quinoline-2-carboxamides with potent anti-tubercular activity. Further optimization of ADME/PK properties culminated in 21b that exhibited compelling in vivo efficacy in a mouse model of Mtb infection.     

Discovery of 3(S)-thiomethyl pyrrolidine ERK inhibitors for oncology

Compound 5 (SCH772984) was identified as a potent inhibitor of ERK1/2 with excellent selectivity against a panel of kinases (0/231 kinases tested @ 100?nM) and good cell proliferation activity, but suffered from poor PK (rat AUC PK @10?mpk?=?0?μM?h; F%?=?0) which precluded further development. In an effort to identify novel ERK inhibitors with improved PK properties with respect to 5, a systematic exploration of sterics and composition at the 3-position of the pyrrolidine led to the discovery of a novel 3(S)-thiomethyl pyrrolidine analog 28 with vastly improved PK (rat AUC PK @10?mpk?=?26?μM?h; F%?=?70).     

Indole acids as a novel PDE2 inhibitor chemotype that demonstrate pro-cognitive activity in multiple species

An internal HTS effort identified a novel PDE2 inhibitor series that was subsequently optimized for improved PDE2 activity and off-target selectivity. The optimized lead, compound 4, improved cognitive performance in a rodent novel object recognition task as well as a non-human primate object retrieval task. In addition, co-crystallization studies of close analog of 4 in the PDE2 active site revealed unique binding interactions influencing the high PDE isoform selectivity.