Phytocannabinoid Pharmacology: Medicinal Properties of Cannabis sativa Constituents Aside from the "Big Two".

Plant-based therapies date back centuries. Cannabis sativa is one such plant that was used medicinally up until the early part of the 20th century. Although rich in diverse and interesting phytochemicals, cannabis was largely ignored by the modern scientific community due to its designation as a schedule 1 narcotic and restrictions on access for research purposes. There was renewed interest in the early 1990s when the endocannabinoid system (ECS) was discovered, a complex network of signaling pathways responsible for physiological homeostasis. Two key components of the ECS, cannabinoid receptor 1 (CB1) and cannabinoid receptor 2 (CB2), were identified as the molecular targets of the phytocannabinoid Δ9-tetrahydrocannabinol (Δ9-THC). Restrictions on access to cannabis have eased worldwide, leading to a resurgence in interest in the therapeutic potential of cannabis. Much of the focus has been on the two major constituents, Δ9-THC and cannabidiol (CBD). Cannabis contains over 140 phytocannabinoids, although only a handful have been tested for pharmacological activity. Many of these minor cannabinoids potently modulate receptors, ionotropic channels, and enzymes associated with the ECS and show therapeutic potential individually or synergistically with other phytocannabinoids. The following review will focus on the pharmacological developments of the next generation of phytocannabinoid therapeutics.

Safety and tolerability of CFI-400945, a first-in-class, selective PLK4 inhibitor in advanced solid tumours: a phase 1 dose-escalation trial.

BACKGROUND: CFI-400945 is a first-in-class oral inhibitor of polo-like kinase 4 (PLK4) that regulates centriole duplication. Primary objectives of this first-in-human phase 1 trial were to establish the safety and tolerability of CFI-400945 in patients with advanced solid tumours. Secondary objectives included pharmacokinetics, pharmacodynamics, efficacy, and recommended phase 2 dose (RP2D). METHODS: Continuous daily oral dosing of CFI-400945 was evaluated using a 3+3 design guided by incidence of dose-limiting toxicities (DLTs) in the first 28-day cycle. Safety was assessed by CTCAE v4.0. ORR and CBR were evaluated using RECIST v1.1. RESULTS: Forty-three patients were treated in dose escalation from 3 to 96 mg/day, and 9 were treated in 64 mg dose expansion. After DLT occurred at 96 and 72 mg, 64 mg was established as the RP2D. Neutropenia was a common high-grade (19%) treatment-related adverse event at ≥ 64 mg. Half-life of CFI-400945 was 9 h, with Cmax achieved 2-4 h following dosing. One PR (45 cycles, ongoing) and two SD ≥ 6 months were observed (ORR = 2%; CBR = 6%). CONCLUSIONS: CFI-400945 is well tolerated at 64 mg with dose-dependent neutropenia. Favourable pharmacokinetic profiles were achieved with daily dosing. Response rates were low without biomarker pre-selection. Disease-specific and combination studies are ongoing. TRIAL REGISTRATION: Clinical Trials Registration Number - NCT01954316 (Oct 1st, 2013).

Design and optimization of (3-aryl-1H-indazol-6-yl)spiro[cyclopropane-1,3'-indolin]-2'-ones as potent PLK4 inhibitors with oral antitumor efficacy.

Previous efforts from our laboratory demonstrated that (E)-3-((3-(E)-vinylaryl)-1H-indazol-6-yl)methylene)-indolin-2-ones are potent PLK4 inhibitors with in vivo anticancer efficacy upon IP dosing. As part of a continued effort to develop selective and orally efficacious inhibitors, we examined variations on this theme wherein 'directly-linked' aromatics, pendant from the indazole core, replace the arylvinyl moiety. Herein, we describe the design and optimization of this series which was ultimately superseded by (3-aryl-1H-indazol-6-yl)spiro[cyclopropane-1,3'-indolin]-2'-ones. The latter compounds are potent and selective inhibitors of PLK4 with oral exposure in rodents and in vivo anticancer activity. Compound 13b, in particular, has a bioavailability of 22% and achieved a 96% tumor growth inhibition in an MDA-MB-468 xenograft study.

Physical and pharmacokinetic characterization of Soluvec™, a novel, solvent-free aqueous ivermectin formulation.

Purpose: To describe application of the Quicksol™ solvent-free approach to solubilize ivermectin (IVM). Methods: Lyophilized IVM complexed with hydroxypropyl-ß-cyclodextrin (HP-ß-CD) was resolubilized in aqueous polysorbate-80, generating Soluvec™. Lyophilizate was examined by Fourier-transform infrared spectroscopy and differential scanning calorimetry; Soluvec, by dynamic light scattering. Pharmacokinetics was evaluated in dogs allocated to subcutaneous (SC) or intramuscular (IM) Soluvec or oral IVM. Results: IVM in Soluvec was tightly bound by HPßCD, forming nearly monodisperse 28 nm particles with solubility ∼2500-times that of free IVM. SC and IM Soluvec increased IVM exposure, peak IVM and extended duration of IVM exposure, versus oral dosing. Conclusion: The Quicksol method generated Soluvec, a concentrated aqueous parenteral IVM formulation with pharmacokinetic properties suitable for veterinary or human use.

Ivermectin (IVM) kills insects and worms that cause disease. Because it doesn't dissolve well, blood IVM can be low. We found a new way to dissolve IVM, using simple, common materials. Dogs receiving our IVM (Soluvec™) had high blood IVM levels for longer, compared with tablet IVM. Next, we hope to learn the best ways to dose Soluvec in animals and people.

Spiro-naphthyridinone piperidines as inhibitors of S. aureus and E. coli enoyl-ACP reductase (FabI).

Spiropiperidine naphthyridinone inhibitors of Staphylococcus aureus and Escherichia coli FabI have been prepared. Compounds 14a and 14c were identified as having sub-nanomolar E. coli FabI activity and are among the most potent FabI inhibitors yet described. The structural model of 14a bound to E. coli FabI is shown.

2,3,4,5-Tetrahydro-1H-pyrido[2,3-b and e][1,4]diazepines as inhibitors of the bacterial enoyl ACP reductase, FabI.

In the search for new antibacterial agents, the enzyme FabI has been identified as an attractive target. Employing a structure guided approach, the previously reported ene-amide series of FabI inhibitors were expanded to include 2,3,4,5-tetrahydro-1H-pyrido[2,3-b and e][1,4]diazepines. These novel series incorporate additional H-bonding functions and can be more water soluble than their naphthyridinone progenitors; diazepine 16c is shown to be efficacious in a mouse infection model.

Discovery of Pyrazolo[1,5-a]pyrimidine TTK Inhibitors: CFI-402257 is a Potent, Selective, Bioavailable Anticancer Agent.

This work describes a scaffold hopping exercise that begins with known imidazo[1,2-a]pyrazines, briefly explores pyrazolo[1,5-a][1,3,5]triazines, and ultimately yields pyrazolo[1,5-a]pyrimidines as a novel class of potent TTK inhibitors. An X-ray structure of a representative compound is consistent with 1(1)/2 type inhibition and provides structural insight to aid subsequent optimization of in vitro activity and physicochemical and pharmacokinetic properties. Incorporation of polar moieties in the hydrophobic and solvent accessible regions modulates physicochemical properties while maintaining potency. Compounds with enhanced oral exposure were identified for xenograft studies. The work culminates in the identification of a potent (TTK K i = 0.1 nM), highly selective, orally bioavailable anticancer agent (CFI-402257) for IND enabling studies.

Use of analogues of methionine and methionyl adenylate to sample conformational changes during catalysis in Escherichia coli methionyl-tRNA synthetase.

Binding of methionine to methionyl-tRNA synthetase (MetRS) is known to promote conformational changes within the active site. However, the contribution of these rearrangements to enzyme catalysis is not fully understood. In this study, several methionine and methionyl adenylate analogues were diffused into crystals of the monomeric form of Escherichia coli methionyl-tRNA synthetase. The structures of the corresponding complexes were solved at resolutions below 1.9A and compared to those of the enzyme free or complexed with methionine. Residues Y15 and W253 play key roles in the strength of the binding of the amino acid and of its analogues. Indeed, full motions of these residues are required to recover the maximum in free energy of binding. Residue Y15 also controls the size of the hydrophobic pocket where the amino acid side-chain interacts. H301 appears to participate to the specific recognition of the sulphur atom of methionine. Complexes with methionyl adenylate analogues illustrate the shielding by MetRS of the region joining the methionine and adenosine moieties. Finally, the structure of MetRS complexed to a methionine analogue mimicking the tetrahedral carbon of the transition state in the aminoacylation reaction was solved. On the basis of this model, we propose that, in response to the binding of the 3'-end of tRNA, Y15 moves again in order to deshield the anhydride bond in the natural adenylate.

The discovery of Polo-like kinase 4 inhibitors: design and optimization of spiro[cyclopropane-1,3'[3H]indol]-2'(1'H).ones as orally bioavailable antitumor agents.

Polo-like kinase 4 (PLK4), a unique member of the polo-like kinase family of serine-threonine kinases, is a master regulator of centriole duplication that is important for maintaining genome integrity. Overexpression of PLK4 is found in several human cancers and is linked with a predisposition to tumorigenesis. Previous efforts to identify potent and efficacious PLK4 inhibitors resulted in the discovery of (E)-3-((1H-indazol-6-yl)methylene)indolin-2-ones, which are superseded by the bioisosteric 2-(1H-indazol-6-yl)spiro[cyclopropane-1,3'-indolin]-2'-ones reported herein. Optimization of this new cyclopropane-linked series was based on a computational model of a PLK4 X-ray structure and SAR attained from the analogous alkenelinked series. The racemic cyclopropane-linked compounds showed PLK4 affinity and antiproliferative activity comparable to their alkene-linked congeners with improved hysicochemical, ADME, and pharmacokinetic properties. Positive xenograft results from the MDA-MB-468 human breast cancer xenograft model for compound 18 support the investigation of PLK4 inhibitors as anticancer therapeutics. A PLK4 X-ray co-structure with racemate 18 revealed preferential binding of the 1R,2S enantiomer to the PLK4 kinase domain.

The discovery of Polo-like kinase 4 inhibitors: identification of (1R,2S).2-(3-((E).4-(((cis).2,6-dimethylmorpholino)methyl)styryl). 1H.indazol-6-yl)-5'-methoxyspiro[cyclopropane-1,3'-indolin]-2'-one (CFI-400945) as a potent, orally active antitumor agent.

Previous publications from our laboratory have introduced novel inhibitors of Polo-like kinase 4 (PLK4), a mitotic kinase identified as a potential target for cancer therapy. The search for potent and selective PLK4 inhibitors yielded (E)-3-((1Hindazol-6-yl)methylene)indolin-2-ones, which were superseded by the bioisosteric 2-(1H-indazol-6-yl)spiro[cyclopropane-1,3'-indolin]-2'-ones, e.g., 3. The later scaffold confers improved drug-like properties and incorporates two stereogenic centers. This work reports the discovery of a novel one-pot double SN2 displacement reaction for the stereoselective installation of the desired asymmetric centers and confirms the stereochemistry of the most potent stereoisomer, e.g., 44. Subsequent work keys on the optimization of the oral exposure of nanomolar PLK4 inhibitors with potent cancer cell growth inhibitory activity. A short list of compounds with superior potency and pharmacokinetic properties in rodents and dogs was studied in mouse models of tumor growth. We conclude with the identification of compound 48 (designated CFI-400945) as a novel clinical candidate for cancer therapy.

The Discovery of Orally Bioavailable Tyrosine Threonine Kinase (TTK) Inhibitors: 3-(4-(heterocyclyl)phenyl)-1H-indazole-5-carboxamides as Anticancer Agents.

The acetamido and carboxamido substituted 3-(1H-indazol-3-yl)benzenesulfonamides are potent TTK inhibitors. However, they display modest ability to attenuate cancer cell growth; their physicochemical properties, and attendant pharmacokinetic parameters, are not drug-like. By eliminating the polar 3-sulfonamide group and grafting a heterocycle at the 4 position of the phenyl ring, potent inhibitors with oral exposure were obtained. An X-ray cocrystal structure and a refined binding model allowed for a structure guided approach. Systematic optimization resulted in novel TTK inhibitors, namely 3-(4-(heterocyclyl)phenyl)-1H-indazole-5-carboxamides. Compounds incorporating the 3-hydroxy-8-azabicyclo[3.2.1]octan-8-yl bicyclic system were potent (TTK IC50 < 10 nM, HCT116 GI50 < 0.1 µM), displayed low off-target activity (>500×), and microsomal stability (T(1/2) > 30 min). A subset was tested in rodent PK and mouse xenograft models of human cancer. Compound 75 (CFI-401870) recapitulated the phenotype of TTK RNAi, demonstrated in vivo tumor growth inhibition upon oral dosing, and was selected for preclinical evaluation.

Methionine in and out of proteins: targets for drug design.

The increasing need for new antibiotics to overcome rapidly developing resistance mechanisms observed in clinical isolates of Gram-positive and Gram-negative eubacteria has placed critical emphasis on the search for new antibacterial enzyme targets and the structural and mechanistic investigation of such targets. Among these potential targets, the enzymes responsible for integrating the amino acid methionine into proteins, along with its subsequent post-translational modification and repair, have emerged as promising candidates for the development of novel antibiotics. As well, there is increasing evidence for the importance of several of these enzymes in the development of anti-cancer, anti-parasitic, and anti-atherosclerotic drugs. Within the last three years, the crystal structures of all of these enzymes have been determined, which offers an unprecedented source of structural information for inhibitor design. The development of combinatorial chemistry and high throughput screening procedures has quickly provided several potent, specific inhibitors for a number of these enzymes, particularly the peptide deformylase, methionine aminopeptidase, and methionyl-tRNA synthetase enzymes. This review critically analyzes the future potential for inhibition of enzymes in this pathway, allowing for a pragmatic view of the success of inhibitor developments and highlighting areas in which further investigations are warranted.

Synthesis and structure-activity relationships of novel arylpiperazines as potent and selective agonists of the melanocortin subtype-4 receptor.

The melanocortin receptors have been implicated as potential targets for a number of important therapeutic indications, including inflammation, sexual dysfunction, and obesity. We identified compound 1, an arylpiperazine attached to the dipeptide H-d-Tic-d-p-Cl-Phe-OH, as a novel melanocortin subtype-4 receptor (MC4R) agonist through iterative directed screening of nonpeptidyl G-protein-coupled receptor biased libraries. Structure-activity relationship (SAR) studies demonstrated that substitutions at the ortho position of the aryl ring improved binding and functional potency. For example, the o-isopropyl-substituted compound 29 (K(i) = 720 nM) possessed 9-fold better binding affinity compared to the unsubstituted aryl ring (K(i) = 6600 nM). Sulfonamide 39 (K(i) = 220 nM) fills this space with a polar substituent, resulting in a further 2-fold improvement in binding affinity. The most potent compounds such as the diethylamine 44 (K(i) = 60 nM) contain a basic group at this position. Basic heterocycles such as the imidazole 50 (K(i) = 110 nM) were similarly effective. We also demonstrated good oral bioavailability for sulfonamide 39.

The discovery of PLK4 inhibitors: (E)-3-((1H-Indazol-6-yl)methylene)indolin-2-ones as novel antiproliferative agents.

The family of Polo-like kinases is important in the regulation of mitotic progression; this work keys on one member, namely Polo-like kinase 4 (PLK4). PLK4 has been identified as a candidate anticancer target which prompted a search for potent and selective inhibitors of PLK4. The body of the paper describes lead generation and optimization work which yielded nanomolar PLK4 inhibitors. Lead generation began with directed virtual screening, using a ligand-based focused library and a PLK4 homology model. Validated hits were used as starting points for the design and discovery of PLK4 inhibitors of novel structure, namely (E)-3-((1H-indazol-6-yl)methylene)indolin-2-ones. Computational models, based on a published X-ray structure (PLK4 kinase domain), were used to understand and optimize the in vitro activity of the series; potent antiproliferative activity was obtained. The kinase selectivity profile and cell cycle analysis of selected inhibitors are described. The results of a xenograft study with an optimized compound 50 (designated CFI-400437) support the potential of these novel PLK4 inhibitors for cancer therapy.

Synthesis of an alpha-aminophosphonate nucleoside as an inhibitor of S-adenosyl-L-homocysteine hydrolase.

A phosphonic acid analogue of S-adenosyl-L-homocysteine was prepared by a novel method and the epimeric mixture separated. Preliminary studies indicate that each epimer causes time-dependent inactivation of S-adenosyl-L-homocysteine hydrolase, however each presented distinct kinetic characteristics.