Discovery of isoquinolinone and naphthyridinone-based inhibitors of poly(ADP-ribose) polymerase-1 (PARP1) as anticancer agents: Structure activity relationship and preclinical characterization.

The exploitation of GLU988 and LYS903 residues in PARP1 as targets to design isoquinolinone (I & II) and naphthyridinone (III) analogues is described. Compounds of structure I have good biochemical and cellular potency but suffered from inferior PK. Constraining the linear propylene linker of structure I into a cyclopentene ring (II) offered improved PK parameters, while maintaining potency for PARP1. Finally, to avoid potential issues that may arise from the presence of an anilinic moiety, the nitrogen substituent on the isoquinolinone ring was incorporated as part of the bicyclic ring. This afforded a naphthyridinone scaffold, as shown in structure III. Further optimization of naphthyridinone series led to identification of a novel and highly potent PARP1 inhibitor 34, which was further characterized as preclinical candidate molecule. Compound 34 is orally bioavailable and displayed favorable pharmacokinetic (PK) properties. Compound 34 demonstrated remarkable antitumor efficacy both as a single-agent as well as in combination with chemotherapeutic agents in the BRCA1 mutant MDA-MB-436 breast cancer xenograft model. Additionally, compound 34 also potentiated the effect of agents such as temozolomide in breast cancer, pancreatic cancer and Ewing's sarcoma models.

Targeting glucose-dependent insulinotropic polypeptide receptor for neurodegenerative disorders.

INTRODUCTION: Incretin hormones, glucose-dependent insulinotropic polypeptide (GIP), and glucagon-like peptide-1 (GLP-1) exert pleiotropic effects on endocrine pancreas and nervous system. Expression of GIP and GIP receptor (GIPR) in neurons, their roles in neurogenesis, synaptic plasticity, neurotransmission, and neuromodulation uniquely position GIPR for therapeutic applications in neurodegenerative disorders. GIP analogs acting as GIPR agonists attenuate neurobehavioral and neuropathological sequelae of neurodegenerative disorders in preclinical models, e.g. Alzheimer's disease (AD), Parkinson's disease (PD), and cerebrovascular disorders. Modulation of GIPR signaling offers an unprecedented approach for disease modification by arresting neuronal viability decline, enabling neuronal regeneration, and reducing neuroinflammation. Growth-promoting effects of GIP signaling and broad-based neuroprotection highlight the therapeutic potential of GIPR agonists. Areas covered: This review focuses on the role of GIPR-mediated signaling in the central nervous system in neurophysiological and neuropathological conditions. In context of neurodegeneration, the article summarizes potential of targeting GIPR signaling for neurodegenerative conditions such as AD, PD, traumatic brain injury, and cerebrovascular disorders. Expert opinion: GIPR represents a validated therapeutic target for neurodegenerative disorders. GIPR agonists impart symptomatic improvements, slowed neurodegeneration, and enhanced neuronal regenerative capacity in preclinical models. Modulation of GIPR signaling is potentially a viable therapeutic approach for disease modification in neurodegenerative disorders.

Bilateral quinolinic acid-induced lipid peroxidation, decreased striatal monoamine levels and neurobehavioral deficits are ameliorated by GIP receptor agonist D-Ala2GIP in rat model of Huntington's disease.

Huntington's disease (HD) is an inherited complex progressive neurodegenerative disorder with an established etiopathology linked to neuronal oxidative stress and corticostriatal excitotoxicity. Present study explores the effects of glucose-dependent insulinotropic polypeptide (GIP) receptor agonist on the neurobehavioral sequelae of quinolinic acid-induced phenotype of Huntington's disease in rats. Bilateral administration of quinolinic acid (300 nmol/4 µl) to the rat striatum led to characteristic deficits in, locomotor activity, motor coordination, neuromuscular coordination and short-term episodic memory. Therapeutic treatment for 14 days with a stable and brain penetrating GIP receptor agonist, D-Ala2GIP (100 nmol/kg, i.p.), attenuated the neurobehavioral deficits due to quinolinic acid (QA) administration. Protective actions of D-Ala2GIP were sensitive to blockade with a GIP receptor antagonist, (Pro3)GIP (50 nmol/kg, i.p.), indicating specific involvement of GIP receptor signaling pathway. Stimulation of GIP receptor with D-Ala2GIP attenuated lipid peroxidation, evidenced by reduced levels of brain malondialdehyde (MDA), and restoration of reduced glutathione (GSH) levels in brain. Quinolinic acid administration led to significant loss of striatal monoamines, e.g., norepinephrine, epinephrine, serotonin, dopamine, and metabolites, 3,4-Dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA) and 5-Hydroxyindoleacetic acid (5-HIAA). D-Ala2GIP attenuated the QA-induced depletion of striatal monoamines, without affecting the monoamine degradation pathways. Thus, observed effects with D-Ala2GIP in the QA-induced Huntington's disease model could be attributable to reduction in lipid peroxidation, restoration of endogenous antioxidants and decreased striatal monoamine levels. These findings together suggest that stimulation of GIP receptor signaling pathway in brain could be a potential therapeutic strategy in the symptomatic management of Huntington's disease.

Prediction of Tumor-to-Plasma Ratios of Basic Compounds in Subcutaneous Xenograft Mouse Models.

BACKGROUND: Predicting target site drug concentrations is of key importance for rank ordering compounds before proceeding to chronic pharmacodynamic models. We propose generic tumor-specific correlation-based regression equations to predict tumor-to-plasma ratios (tumor-Kps) in slow- and fast-growing xenograft mouse models. METHODS: Disposition of 14 basic small molecules was investigated extensively in mouse plasma, tissues and tumors after a single oral dose administration. Linear correlation was assessed and compared between tumor-Kp and normal tissue-to-plasma ratio (tissue-Kps) separately for each tumor xenograft. The developed regression equations were validated by leave-one-out cross-validation (LOOCV) method. RESULT: Both slow- and fast-growing tumor-Kps showed good correlation (r 2 ≥ 0.7) with majority of the normal tissue-Kps. Substantial difference was observed in the slopes of developed equations between two xenografts, which was in line with observed difference in tumor distribution. The linear correlations between tumor-Kp and skin- or spleen-Kp were within the acceptable statistical criteria (LOOCV) across xenografts and the class of compounds evaluated. Since > 70% of tumor-Kps from the test data sets were predicted within a factor of twofold for both slow- and fast-growing xenograft mouse models, the results validate the applicability of the developed equations across xenografts. CONCLUSION: Tumor-specific correlation-based regression equations were developed and their applicability was adequately validated across xenografts. These equations could be successfully translated to predict tumor concentrations in order to preclude experimental tumor-Kp determination.

Effect of D-Ala2GIP, a stable GIP receptor agonist on MPTP-induced neuronal impairments in mice.

The aim of the present study was to evaluate the ability of D-Ala2GIP, a gastric inhibitory polypeptide (GIP) receptor agonist, to attenuate the behavioral phenotype of Parkinson's disease caused by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) administration in mice. In the behavioral studies, MPTP administration led to spontaneous locomotor activity deficits, impaired rotarod performance, akinesia, muscular rigidity and increased tremor amplitude, which was attenuated by pretreatment with D-Ala2GIP (50-100 nmol/kg, i.p.). This acute neuroprotective response by D-Ala2GIP was found to be blocked by a selective GIP receptor antagonist, (Pro3)GIP (50 nmol/kg, i.p.), indicating that the observed effects are mediated through GIP receptor mediated signaling pathway. Biochemical studies revealed that D-Ala2GIP reduced the brain malondialdehyde levels and enhanced the brain glutathione levels, thereby mitigating the MPTP-induced oxidative stress. MPTP administration resulted in reduction of the striatal concentration of dopamine and its metabolites, homovanillic acid (HVA) and 3, 4-Dihydroxyphenylacetic acid (DOPAC). Pretreatment with D-Ala2GIP attenuated the loss of striatal dopamine levels without affecting the normal dopamine catabolism. Thus, the observed effects in the MPTP-induced Parkinsonism model could be in part attributable to the antioxidant properties of D-Ala2GIP and enhanced turnover of dopamine in the nigrostriatal pathways in mouse brain. These findings together suggest that GIP receptor could be a therapeutic target in the management of symptoms of Parkinson's disease.

Gastric-sparing nitric oxide-releasable 'true' prodrugs of aspirin and naproxen.

Nitric oxide-releasing non-steroidal anti-inflammatory drugs (NO-NSAIDs) are gaining attention as potentially gastric-sparing NSAIDs. Herein, we report a novel class of '1-(nitrooxy)ethyl ester' group-containing NSAIDS as efficient NO releasing 'true' prodrugs of aspirin and naproxen. While an aspirin prodrug exhibited comparable oral bioavailability and antiplatelet activity (i.e., TXB2 inhibition) to those of aspirin, a naproxen prodrug exhibited better bioavailability than naproxen. These promising NO-NSAIDs protected experimental rats from gastric damage. We therefore believe that these promising NO-NSAIDs could represent a new class of potentially 'Safe NSAIDs' for the treatment of arthritic pain, inflammation and cardiovascular disorders in the case of NO-aspirin.

Synthesis and therapeutic evaluation of pyridyl based novel mTOR inhibitors.

A series of novel cyanopyridyl based molecules (1-14) were designed, synthesized and probed for inhibition of mammalian target of rapamycin (mTOR) activity. Compound 14 was found to be a potent inhibitor of mTOR activity as assessed by enzyme-linked immunoassays and Western blot analysis. Most importantly, systemic application (intraperitoneal; ip) of compound 14 significantly suppressed macroscopic and histological abnormalities associated with chemically-induced murine colitis.

The influence of dextromethorphan on morphine analgesia in Swiss Webster mice is sex-specific.

NMDA (N-methyl-d-aspartate) antagonists are known to enhance the analgesic effects of opioids. However, virtually, all studies of this phenomenon have been done using male subjects. Here, the noncompetitive NMDA receptor antagonist dextromethorphan (DEX) was tested over a range of doses (10-200 microg intracerebroventricularly [i.c.v.]) in male and female Swiss Webster mice in combination with 5 mg/kg intraperitoneal (i.p.) morphine. Males exhibited enhanced morphine analgesia following either 100 or 200 microg DEX, but there was no evidence of DEX-mediated potentiation in females at any dose. Instead, DEX attenuated morphine analgesia in females. We also evaluated the effect of 100 microg i.c.v. DEX with different doses of morphine (1, 5 and 10 mg/kg). Again, DEX significantly enhanced morphine analgesia in male mice and attenuated it in females. Next, ovariectomized (OVX) female mice were compared to males following 5 mg/kg i.p. morphine and 100 microg i.c.v. DEX. Male and OVX females exhibited equivalent maximal levels of analgesia following administration of DEX. Morphine analgesia was not enhanced by DEX in sham-treated females and OVX mice with estradiol treatment (5 microg i.p. once daily for 7 days) also did not show DEX enhancement. These experiments demonstrate that the ability of NMDA receptor antagonists to potentiate morphine analgesia is modulated by an estrogen-sensitive mechanism and suggest that sex differences may play a critical role toward a more general understanding of the potentiation of opioid-induced analgesia through NMDA receptor antagonists.

Protective effect of a polyherbal formulation (Immu-21) against cyclophosphamide-induced mutagenicity in mice.

The object was to evaluate the effects of a polyherbal formulation, Immu-21, against cyclophosphamide (CP)-induced chromosomal aberrations (CA) and micronuclei (MN) in mice. CP alone (40 mg/kg, i.p.) produced classical as well as non-classical chromosomal aberrations in mice, and the incidence of CA was significantly more in the CP treated group when compared with that of the control group. Immu-21, which contains extracts of Ocimum sanctum, Withania somnifera, Emblica officinalis and Tinospora cordifolia, was given at 100 mg/kg, daily, over 7 days, and 30 mg/kg daily over 14 days and inhibited both CP-induced classical and non-classical chromosomal aberrations ( approximately 40%-60% of control). A significant increase in MN was also observed in bone marrow erythrocytes of mice treated with CP, and pretreatment with Immu-21 also significantly reduced these. Cytotoxicity was evaluated by estimating the ratio of polychromatic erythrocytes (PCEs) to normochromatic erythrocytes (NCEs). The present results indicate that chronic treatment with Immu-21 prevented CP-induced genotoxicity in mice.

Cell proliferation and natural killer cell activity by polyherbal formulation, Immu-21 in mice.

Immunomodulatory activity of an Ayurvedic polyherbal formulation, Immu-21 containing extracts of Ocimum sanctum, Withania somnifera, Emblica officinalis and Tinospora cordifolia was studied on proliferative response of splenic leukocytes to T cell mitogens, concanavalin (Con)-A and phytohemagglutinin (PHA) and B cell mitogen, lipopolysaccharide (LPS) in vitro by [3H]-thymidine uptake assay in mice. The cytotoxic activity of Immu-21 was tested by measuring the splenic leukocyte natural killer (NK) cell activity against K 562 cells. Intraperitoneal (i.p.) treatment with Immu-21 (30 mg/kg) once a day for 14 and 21 days did not cause change in body weight and spleen weight, where as splenocytes/spleen count was increased. Treatment of Immu-21 (30 mg/kg, i.p.) for 14 days and 1 mg/kg for 21 days significantly increased LPS induced leukocyte proliferation. NK cell activity was significantly increased when mice were pretreated with Immu-21 (10 and 30 mg/kg, i.p.) once a day for 7 days. The results indicate that pretreatment with Immu-21 selectively increased the proliferation of splenic leukocyte to B cell mitogen, LPS and cytotoxic activity against K 562 cells in mice.