Discovery of a Novel Series of Potent, Selective, Orally Available, and Brain-Penetrable C1s Inhibitors for Modulation of the Complement Pathway.

A novel series of non-amidine-based C1s inhibitors have been explored. Starting from high-throughput screening hit 3, isoquinoline was replaced with 1-aminophthalazine to enhance C1s inhibitory activity while exhibiting good selectivity against other serine proteases. We first disclose a crystal structure of a complex of C1s and a small-molecule inhibitor (4e), which guided structure-based optimization around the S2 and S3 sites to further enhance C1s inhibitory activity by over 300-fold. Improvement of membrane permeability by incorporation of fluorine at the 8-position of 1-aminophthalazine led to identification of (R)-8 as a potent, selective, orally available, and brain-penetrable C1s inhibitor. (R)-8 significantly inhibited membrane attack complex formation induced by human serum in a dose-dependent manner in an in vitro assay system, proving that selective C1s inhibition blocked the classical complement pathway effectively. As a result, (R)-8 emerged as a valuable tool compound for both in vitro and in vivo assessment.

Increasing Effects of Selective 5-Hydroxytryptamine Type 2C Receptor Stimulation on Evoked Momentary Urethral Closure in Female Rats and Humans.

Under healthy conditions, more than one urethra-closing reflex, including both bladder afferent-independent and -dependent actions, function during momentary elevation of intravesical (bladder) pressure to prevent urinary incontinence. In the current study, the effects of a novel selective 5-hydroxytryptamine type 2C (5-HT2C) receptor agonist, TAK-233, on evoked momentary urethra-closing functions were investigated in female rats and humans to elucidate 5-HT2C receptor functions. In anesthetized female rats, TAK-233 dose-dependently and significantly increased urethral resistance during sneezing in rats with distended vaginas and bilaterally transected pelvic nerves. The drug also dose-dependently and significantly increased urethral resistance during momentary intravesical pressure elevation by electrical stimulation of abdominal muscles in rats with a transected spinal cord at the T8-T9 level and intact pelvic nerves. The increased effects observed during electrical stimulation were abolished by either an intravenously administered selective 5-HT2C receptor antagonist, SB 242084, or bilateral transection of the pelvic nerves or somatic nerves innervating the external urethral sphincter and pelvic floor muscles. In the spinal cord-transected and pelvic nerve-intact rats, TAK-233 enlarged the urethra-closing responses induced by both passive and abrupt intravesical pressure elevation, measured by a microtip transducer located in the middle urethra. Additionally, the effects of TAK-233 on the stimulus threshold of urethral contractile responses induced by transcranial magnetic stimulation were investigated in healthy female volunteers. The drug dose-dependently and significantly lowered this stimulus threshold, indicating an increased sensitivity of the response. These results demonstrate that 5-HT2C receptor stimulation enhances the evoked momentary urethra-closing functions in both female rats and humans. SIGNIFICANCE STATEMENT: 5-hydroxytryptamine (serotonin) type 2C (5-HT2C) receptor stimulation by TAK-233 enhanced urethral resistance in rats during an evoked momentary event in which the bladder afferent-independent or -dependent reflex functions via striated muscle-mediated mechanisms. The increases in sensitivity of transcranial magnetic stimulation-evoked urethral contractile responses in healthy female subjects indicates that this mechanism also functions in humans. The evoked momentary conditions activating these reflexes provide a suitable model to demonstrate the effects of 5-HT2C receptor stimulation.

Discovery of 7-Oxo-2,4,5,7-tetrahydro-6 H-pyrazolo[3,4- c]pyridine Derivatives as Potent, Orally Available, and Brain-Penetrating Receptor Interacting Protein 1 (RIP1) Kinase Inhibitors: Analysis of Structure-Kinetic Relationships.

We report the discovery of 7-oxo-2,4,5,7-tetrahydro-6 H-pyrazolo[3,4- c]pyridine derivatives as a novel class of receptor interacting protein 1 (RIP1) kinase inhibitors. On the basis of the overlay study between HTS hit 10 and GSK2982772 (6) in RIP1 kinase, we designed and synthesized a novel class of RIP1 kinase inhibitor 11 possessing moderate RIP1 kinase inhibitory activity and P-gp mediated efflux. The optimization of the core structure and the exploration of appropriate substituents utilizing SBDD approach led to the discovery of 22, a highly potent, orally available, and brain-penetrating RIP1 kinase inhibitor with excellent PK profiles. Compound 22 significantly suppressed necroptotic cell death both in mouse and human cells. Oral administration of 22 (10 mg/kg, bid) attenuated disease progression in the mouse experimental autoimmune encephalomyelitis (EAE) model of multiple sclerosis (MS). Moreover, analysis of structure-kinetic relationship (SKR) for our novel chemical series was also discussed.

Discovery and pharmacological characterization of a new class of prolyl-tRNA synthetase inhibitor for anti-fibrosis therapy.

Scleroderma has clinical characteristics including skin and other tissue fibrosis, but there is an unmet need for anti-fibrotic therapy. Halofuginone (HF) is a well-known anti-fibrosis agent in preclinical and clinical studies which exerts its effect via inhibition of TGF-ß/Smad3 signaling pathway. Recently, prolyl-tRNA synthetase (PRS) was elucidated as a target protein for HF that binds to the proline binding site of the catalytic domain of PRS. Here, we characterized a new class of PRS inhibitor (T-3833261) that is carefully designed in a way that binds to the ATP site of the catalytic domain and does not disrupt binding of proline. The anti-fibrotic activity and the mechanism of action for T-3833261 on TGF-ß-induced fibrotic assay were compared with those of HF in primary human skin fibroblast. We evaluated in vivo effect of topical application of T-3833261 and HF on TGF-ß-induced fibrotic genes expression in mice. We found that T-3833261 suppressed TGF-ß-induced α-smooth muscle actin (α-SMA) and type I collagen α1 (COL1A1) expression through the Smad3 axis in a similar fashion to HF. In vivo topical application of T-3833261 reduced the increase of fibrotic genes expression such as α-Sma, Col1a1 and Col1a2 by TGF-ß intradermal injection to the ear of a mouse. We revealed that T-3833261 is more effective than HF under the conditions of high proline concentration, as reported in fibrotic tissues. These results suggest the potential of ATP competitive PRS inhibitors for the treatment of fibrotic diseases such as scleroderma.

CETSA quantitatively verifies in vivo target engagement of novel RIPK1 inhibitors in various biospecimens.

The proof of target engagement (TE) is a key element for evaluating potential investment in drug development. The cellular thermal shift assay (CETSA) is expected to facilitate direct measurement of intracellular TE at all stages of drug development. However, there have been no reports of applying this technology to comprehensive animal and clinical studies. This report demonstrates that CETSA can not only quantitatively evaluate the drug-TE in mouse peripheral blood, but also confirm TE in animal tissues exemplified by using the receptor interacting protein 1 kinase (RIPK1) lead compound we have developed. Our established semi-automated system allows evaluation of the structure-activity relationship using native RIPK1 in culture cell lines, and also enables estimation of drug occupancy ratio in mouse peripheral blood mononuclear cells. Moreover, optimized tissue homogenisation enables monitoring of the in vivo drug-TE in spleen and brain. Our results indicate that CETSA methodology will provide an efficient tool for preclinical and clinical drug development.

A novel JAK inhibitor, peficitinib, demonstrates potent efficacy in a rat adjuvant-induced arthritis model.

The Janus kinase (JAK) family of tyrosine kinases is associated with various cytokine receptors. JAK1 and JAK3 play particularly important roles in the immune response, and their inhibition is expected to provide targeted immune modulation. Several oral JAK inhibitors have recently been developed for treating autoimmune diseases, including rheumatoid arthritis (RA). Here, we investigated the pharmacological effects of peficitinib (formerly known as ASP015K), a novel, chemically synthesized JAK inhibitor. We found that peficitinib inhibited JAK1 and JAK3 with 50% inhibitory concentrations of 3.9 and 0.7 nM, respectively. Peficitinib also inhibited IL-2-dependent T cell proliferation in vitro and STAT5 phosphorylation in vitro and ex vivo. Furthermore, peficitinib dose-dependently suppressed bone destruction and paw swelling in an adjuvant-induced arthritis model in rats via prophylactic or therapeutic oral dosing regimens. Peficitinib also showed efficacy in the model by continuous intraperitoneal infusion. Area under the concentration versus time curve (AUC) at 50% inhibition of paw swelling via intraperitoneal infusion was similar to exposure levels of AUC at 50% inhibition via oral administration, implying that AUC might be important for determining the therapeutic efficacy of peficitinib. These data suggest that peficitinib has therapeutic potential for the oral treatment of RA.

Design, synthesis, and biological evaluation of a novel series of peripheral-selective noradrenaline reuptake inhibitors-Part 2.

Peripherally selective inhibition of noradrenaline reuptake is a novel mechanism for the treatment of stress urinary incontinence to overcome adverse effects associated with central action. Herein, we describe our medicinal chemistry approach to discover peripheral-selective noradrenaline reuptake inhibitors to avert the risk of P-gp-mediated DDI at the blood-brain barrier. We observed that steric shielding of the hydrogen-bond acceptors and donors (HBA and HBD) of compound 1 reduced the multidrug resistance protein 1 (MDR1) efflux ratio; however, the resulting compound 6, a methoxyacetamide derivative, was mainly metabolized by CYP2D6 and CYP2C19 in the in vitro phenotyping study, implying the risk of PK variability based on the genetic polymorphism of the CYPs. Replacement of the hydrogen atom with a deuterium atom in a strategic, metabolically hot spot led to compound 13, which was mainly metabolized by CYP3A4. To our knowledge, this study represents the first report of the effect of deuterium replacement for a major metabolic enzyme. The compound 13, N-{[(6S,7R)-7-(4-chloro-3-fluorophenyl)-1,4-oxazepan-6-yl]methyl}-2-[(2H(3))methyloxy]acetamide hydrochloride, which exhibited peripheral NET selective inhibition at tested doses in rats, increased urethral resistance in a dose-dependent manner.

Design, synthesis, and biological evaluation of a novel series of peripheral-selective noradrenaline reuptake inhibitors - Part 3.

Peripheral-selective inhibition of noradrenaline reuptake is a novel mechanism for the treatment of stress urinary incontinence to overcome adverse effects associated with central action. Here, we describe our medicinal chemistry approach to discover a novel series of highly potent, peripheral-selective, and orally available noradrenaline reuptake inhibitors with a low multidrug resistance protein 1 (MDR1) efflux ratio by cyclization of an amide moiety and introduction of an acidic group. We observed that the MDR1 efflux ratio was correlated with the pKa value of the acidic moiety. The resulting compound 9 exhibited favorable PK profiles, probably because of the effect of intramolecular hydrogen bond, which was supported by a its single-crystal structure. The compound 9, 1-{[(6S,7R)-7-(4-chloro-3-fluorophenyl)-1,4-oxazepan-6-yl]methyl}-2-oxo-1,2-dihydropyridine-3-carboxylic acid hydrochloride, which exhibited peripheral NET-selective inhibition at tested doses in rats by oral administration, increased urethral resistance in a dose-dependent manner.

Structure-Based Design and Synthesis of 3-Amino-1,5-dihydro-4H-pyrazolopyridin-4-one Derivatives as Tyrosine Kinase 2 Inhibitors.

We report herein the discovery and optimization of 3-amino-1,5-dihydro-4H-pyrazolopyridin-4-one TYK2 inhibitors. High-throughput screening against TYK2 and JAK1-3 provided aminoindazole derivative 1 as a hit compound. Scaffold hopping of the aminoindazole core led to the discovery of 3-amino-1,5-dihydro-4H-pyrazolopyridin-4-one derivative 3 as a novel chemotype of TYK2 inhibitors. Interestingly, initial SAR study suggested that this scaffold could have a vertically flipped binding mode, which prompted us to introduce a substituent at the 7-position as a moiety directed toward the solvent-exposed region. Introduction of a 1-methyl-3-pyrazolyl moiety at the 7-position resulted in a dramatic increase in TYK2 inhibitory activity, and further optimization led to the discovery of 20. Compound 20 inhibited IL-23-induced IL-22 production in a rat PD assay, as well as inhibited IL-23 signaling in human PBMC. Furthermore, 20 showed selectivity for IL-23 signaling inhibition against GM-CSF, demonstrating the unique cytokine selectivity of the novel TYK2 inhibitor.

Design, synthesis and biological evaluation of a novel series of peripheral-selective noradrenaline reuptake inhibitor.

Centrally acting noradrenaline reuptake inhibitor (NRI) is reportedly effective for patients with stress urinary incontinence (SUI) by increasing urethral closure in the clinical Phase IIa study with esreboxetine. Noradrenaline transporters are expressed in both central and peripheral nervous systems and the contribution of each site to efficacy has not been clarified. This report describes the development of a series of peripheral-selective 7-phenyl-1,4-oxazepane NRIs to investigate the contribution of the peripheral site to increasing urethral resistance in rats. (6S,7R)-1,4-Oxazepane derivative 7 exhibited noradrenaline transporter inhibition with high selectivity against inhibitions of serotonin and dopamine transporters. A replacement of hydroxyl with acetamide group contributed to enhancement of peripheral selectivity by increasing molecular polarity. Compound 12, N-{[(6S,7R)-7-(3,4-dichlorophenyl)-1,4-oxazepan-6-yl]methyl}acetamide 0.5 fumarate, which showed effectively no brain penetration in rats, increased urethral resistance in a dose-dependent manner and exhibited a maximal effect on par with esreboxetine. These results demonstrate that the urethral resistance-increasing effects of NRI in rats are mainly caused by the inhibition of noradrenaline transporters in the peripheral sites.

Pharmacological profile of FK881(ASP6537), a novel potent and selective cyclooxygenase-1 inhibitor.

Nonsteroidal anti-inflammatory drugs (NSAIDs) are now understood to fall into one of two agent classes in clinical use. Traditional NSAIDs inhibit both cyclooxygenases-1 and 2 (COX-1, 2), which act as key enzymes catalyzing the same reaction in the production of prostaglandins (PGs), while the second class of NSAIDs selectively inhibit COX-2. Inhibition of the inducible COX-2 isoform is believed to be responsible for the therapeutic effects of NSAIDs, such as anti-inflammatory, analgesic, and antipyretic effects, while COX-1 inhibition results in side-effects on the gastrointestinal (GI) system. In the present study, however, we changed this notion that inhibiting only COX-1 causes adverse effects. We discovered FK881, a specific COX-1 inhibitor which exhibits a 650-fold ratio for human whole blood COX-1/COX-2 and rats in vivo. In rats, FK881 dose dependently inhibited carrageenan-induced paw edema (ED30: 22 mg/kg; diclofenac ED30: 3.6 mg/kg, rofecoxib ED30: 26 mg/kg) and paw swelling associated with adjuvant arthritis (ED50: 17 mg/kg; diclofenac ED50: 1.4 mg/kg, rofecoxib ED50: 1.8 mg/kg). Further, FK881 dose dependently inhibited acetic acid-induced writhing in mice (ED50: 19 mg/kg; diclofenac ED50: 14 mg/kg, rofecoxib ED50: >100mg/kg) and adjuvant arthritis hyperalgesia in rats (ED50: 1.8 mg/kg; diclofenac ED50: 1.0mg/kg, rofecoxib ED50: 0.8mg/kg). However, unlike traditional NSAIDs, GI tolerability was improved, although the antipyretic effect of FK881 was weak (NOEL: >320 mg/kg; diclofenac NOEL: <1mg/kg, rofecoxib NOEL: 100 mg/kg). These results suggest that FK881 may be useful in treating symptoms of rheumatoid arthritis and osteoarthritis.

Role of vasopressin V(1A) receptor in the urethral closure reflex in rats.

An enhanced urethral closure reflex via the spinal cord is related to urethral resistance elevation during increased abdominal pressure. However, with the exception of monoamines, neurotransmitters modulating this reflex are not understood. We investigated whether the vasopressin V(1A) receptor (V(1A)R) is involved in the urethral closure reflex in urethane-anesthetized female rats. V(1A)R mRNA was highly expressed among the vasopressin receptor family in the total RNA purified from lamina IX in the spinal cord L6-S1 segment. In situ hybridization analysis of the spinal L6-S1 segment confirmed that these positive signals from the V(1A)Rs were only detected in lamina IX. Intrathecally injected Arg8-vasopressin (AVP), an endogenous ligand, significantly increased urethral resistance during an intravesical pressure rise, and its effect was blocked by the V(1A)R antagonist. AVP did not increase urethral resistance in rats in which the pelvic nerves were transected bilaterally. Urethral closure reflex responses to the intravesical pressure rise increased by up to threefold compared with the baseline response after AVP administration in contrast to no increase by vehicle. In addition, intravenously and intrathecally injected V(1A)R antagonists decreased urethral resistance. These results suggest that V(1A)R stimulation in the spinal cord enhances the urethral closure reflex response, thereby increasing urethral resistance during an abdominal pressure rise and that V(1A)R plays a physiological role in preventing urine leakage.

Anti-inflammatory activity of non-nucleoside adenosine deaminase inhibitor FR234938.

Adenosine has anti-inflammatory activity. Adenosine deaminase (EC 3.5.4.4) metabolizes extracellular adenosine, resulting in an exacerbation of inflammation. Consequently, it was hypothesized that adenosine deaminase inhibitors produce anti-inflammatory activity by increasing extracellular adenosine concentration. This group recently developed a non-nucleoside adenosine deaminase inhibitor, FR234938, by using rational structure-based drug design. FR234938 inhibits recombinant human adenosine deaminase enzyme competitively. FR234938 inhibits interleukin (IL)-6-dependent immunoglobulin (Ig) M production by SKW6.4 cells, in the presence of adenosine. Inhibitory effect of FR234938/adenosine combination is blocked by an A2a adenosine receptor antagonist. FR234938 also inhibits anti-type II collagen delayed type hypersensitivity (DTH) in a dose-dependent manner, both in the presence and absence of recombinant human adenosine deaminase. Moreover, FR234938 inhibits tumor necrosis factor (TNF)-alpha and IL-10 production in a lipopolysaccharide (LPS)-induced cytokine production model in mice. These results indicate that FR234938 has potential anti-inflammatory activity. Non-nucleoside adenosine deaminase inhibitor FR234938 has good potential as a new type of anti-rheumatic and anti-inflammatory drug, by modulating host-defense concentrations of adenosine.

Structural basis of compound recognition by adenosine deaminase.

Structural snapshots corresponding to various states enable elucidation of the molecular recognition mechanism of enzymes. Adenosine deaminase has two distinct conformations, an open form and a closed form, although it has so far been unclear what factors influence adaptation of the alternative conformations. Herein, we have determined the first nonligated structure as an initial state, which was the open form, and have thereby rationally deduced the molecular recognition mechanism. Inspection of the active site in the nonligated and ligated states indicated that occupancy at one of the water-binding positions in the nonligated state was highly significant in determining alternate conformations. When this position is empty, subsequent movement of Phe65 toward the space induces the closed form. On the other hand, while occupied, the overall conformation remains in the open form. This structural understanding should greatly assist structure-oriented drug design and enable control of the enzymatic activity.

Rational design of non-nucleoside, potent, and orally bioavailable adenosine deaminase inhibitors: predicting enzyme conformational change and metabolism.

From metabolic considerations and prediction of an inhibitor-induced conformational change, novel adenosine deaminase (ADA) inhibitors with improved activities and oral bioavailability have been developed on the basis of our originally designed non-nucleoside ADA inhibitors. They demonstrated in vivo efficacy in models of inflammation and lymphoma. Furthermore, X-ray crystal structure analysis has revealed a novel induced fit to ADA.

Structure-based design, synthesis, and structure-activity relationship studies of novel non-nucleoside adenosine deaminase inhibitors.

We disclose herein optimization efforts around the novel, highly potent non-nucleoside adenosine deaminase (ADA) inhibitor, 1-[(R)-1-hydroxy-4-(6-(3-(1-methylbenzimidazol-2-yl)propionylamino)indol-1-yl)-2-butyl]imidazole-4-carboxamide 1 (K(i)= 7.7 nM), which we recently reported. Structure-based drug design (SBDD) utilizing the crystal structure of the 1/ADA complex was performed in order to obtain structure-activity relationships (SAR) for this type of compound rationally and effectively. To utilize the newly formed hydrophobic space (F2), replacement of the benzimidazole ring of 1 with a n-propyl chain (4b) or a simple phenyl ring (4c) was tolerated in terms of binding activity, and the length of the methylene-spacer was shown to be optimal at two or three. Replacement of an amide with an ether as a linker was also well tolerated in terms of binding activity and moreover improved the oral absorption (6a and 6b). Finally, transformation of indol-1-yl to indol-3-yl resulted in discovery of a novel highly potent and orally bioavailable ADA inhibitor, 1-[(R)-4-(5-(3-(4-chlorophenyl)propoxy)-1-methylindol-3-yl)-1-hydroxy-2-butyl]imidazole-4-carboxamide 8c.

Structure-based design and synthesis of non-nucleoside, potent, and orally bioavailable adenosine deaminase inhibitors.

We disclose optimization efforts based on the novel non-nucleoside adenosine deaminase (ADA) inhibitor, 4 (K(i) = 680 nM). Structure-based drug design utilizing the crystal structure of the 4/ADA complex led to discovery of 5 (K(i) = 11 nM, BA = 30% in rats). Furthermore, from metabolic considerations, we discovered two inhibitors with improved oral bioavailability [6 (K(i) = 13 nM, BA = 44%) and 7 (K(i) = 9.8 nM, BA = 42%)]. 6 demonstrated in vivo efficacy in models of inflammation and lymphoma.

A highly potent non-nucleoside adenosine deaminase inhibitor: efficient drug discovery by intentional lead hybridization.

We disclose herein the rapid discovery of the first highly potent (Ki = 7.7 nM) non-nucleoside adenosine deaminase (ADA) inhibitor based on the rational hybridization of two structurally distinct leads. Two micromolar inhibitors were discovered by a parallel rational design and random screening program, and individual crystal structures of bovine ADA in complexation with these inhibitors revealed several unknown binding sites and distinct binding modes. Using this information as the starting point, highly effective lead hybridization was achieved in only two structure-based drug design iterations. The conceptual approach illustrated by this example promises to be broadly useful in the search for new chemical entities and can contribute greatly to improve the overall efficiency and speed of drug discovery.

In vitro and in vivo activities of T-705 and oseltamivir against influenza virus.

T-705 (6-fluoro-3-hydroxy-2-pyrazinecarboxamide) has a potent and selective inhibitory activity against influenza virus. We studied the effects of an infectious dose on the anti-influenza virus activities of T-705 and oseltamivir, a commercially available neuraminidase inhibitor, both in vitro and in vivo. Plaque formation of influenza A/PR/8/34 virus was completely inhibited by 10 microg/ml of T-705 after 72 h incubation, whereas visible plaque formation was detected in the plate treated with GS 4071, the active form of oseltamivir (10 microg/ml). The antiviral activity of T-705 was not influenced by an increase in multiplicity of infection (MOI) from 0.0001 to 1, but that of GS 4071 was influenced in a yield reduction assay. No increase in viral yield was seen in either culture supernatant or cells after removal of T-705 (10 microg/ml) but, in contrast, productive infection recurred in culture supernatant and in cells after removal of GS 4071. In mice infected with a high challenge dose of influenza A/PR/8/34 virus, orally administered T-705 (200 and 400 mg/kg/day) completely prevented the death of mice and the survival rates of mice were significantly higher than those in mice treated with oseltamivir (P<0.01). When the treatment was delayed at 1, 13 and 25 h post infection, oral administration of 200 mg/kg of T-705 significantly prevented the death of mice (P<0.01), and the survival rates of mice treated with T-705 were comparable to those of mice treated with oseltamivir. These results suggest that T-705 has the potential to be a potent inhibitor of human influenza virus infections.

Structure-based de novo design of non-nucleoside adenosine deaminase inhibitors.

We searched for non-nucleoside inhibitors of adenosine deaminase by rational structure-based de novo design and succeeded in the discovery of 1-(1-hydroxy-4-phenyl-2-butyl)imidazole-4-carboxamide (FR221647: K(i)=5.9 microM to human ADA) as a novel inhibitor with moderate activity and good pharmacokinetics compared with the known inhibitors pentostatin and EHNA.