Calcium-sensing receptor activator cinacalcet for treatment of cyclic nucleotide-mediated secretory diarrheas.

Cyclic nucleotide elevation in intestinal epithelial cells is the key pathology causing intestinal fluid loss in secretory diarrheas such as cholera. Current secretory diarrhea treatment is primarily supportive, and oral rehydration solution is the mainstay of cholera treatment. There is an unmet need for safe, simple and effective diarrhea treatments. By promoting cAMP hydrolysis, extracellular calcium-sensing receptor (CaSR) is a regulator of intestinal fluid transport. We studied the antidiarrheal mechanisms of FDA-approved CaSR activator cinacalcet and tested its efficacy in clinically relevant human cell, mouse and intestinal organoid models of secretory diarrhea. By using selective inhibitors, we found that cAMP agonists-induced secretory short-circuit currents (Isc) in human intestinal T84 cells are mediated by collective actions of apical membrane cystic fibrosis transmembrane conductance regulator (CFTR) and Clc-2 Cl- channels, and basolateral membrane K+ channels. 30 µM cinacalcet pretreatment inhibited all 3 components of forskolin and cholera toxin-induced secretory Isc by ∼75%. In mouse jejunal mucosa, cinacalcet inhibited forskolin-induced secretory Isc by ∼60% in wild type mice, with no antisecretory effect in intestinal epithelia-specific Casr knockout mice (Casr-flox; Vil1-cre). In suckling mouse model of cholera induced by oral cholera toxin, single dose (30 mg/kg) oral cinacalcet treatment reduced intestinal fluid accumulation by ∼55% at 20 hours. Lastly, cinacalcet inhibited forskolin-induced secretory Isc by ∼75% in human colonic and ileal organoids. Our findings suggest that CaSR activator cinacalcet has antidiarrheal efficacy in distinct human cell, organoid and mouse models of secretory diarrhea. Considering its excellent clinical safety profile, cinacalcet can be repurposed as a treatment for cyclic nucleotide-mediated secretory diarrheas including cholera.

Ivabradine treatment lowers blood pressure and promotes cardiac and renal protection in spontaneously hypertensive rats.

Hypertension is linked to hyperpolarization-activated cyclic nucleotide-gated (HCN) function, expressed in excitable and non-excitable cells. Considering that the reduction in heart rate (HR) improves coronary perfusion and cardiac performance, ivabradine (IVA) emerged as an important drug for the treatment of cardiovascular diseases. AIM: Evaluate if IVA chronic treatment effect can mitigate hypertension and reverse the cardiac and renal damage in SHR. MAIN METHODS: Rats were divided into 4 groups treated for 14 days with PBS (1 ml/kg; i.p) or IVA (1 mg/kg; i.p): 1) WKY PBS; 2) SHR PBS; 3) WKY IVA; and 4) SHR IVA. The systolic blood pressure (SBP) was measured, indirectly, before and during the treatment period with IVA (day 0, 1, 7 and 11). Rats were subjected to artery cannulation for direct blood pressure (BP) measurement. Morphofunctional and gene expression were evaluated in the heart and kidneys. KEY FINDINGS: IVA reduced SBP only in SHR on the 7th day. Direct blood pressure measurement showed that IVA chronic treatment reduced HR in the SHR. Interestingly, mean arterial pressure (MAP) was reduced in SHR IVA when compared to SHR PBS. Serum and urinary biochemical data were not altered by IVA. Moreover, IVA reduced the renal inflammatory infiltrates and increased glomerular density, besides preventing the cardiac inflammatory and hypertrophic responses. SIGNIFICANCE: IVA treatment lowered blood pressure, improved cardiac remodeling and inflammation, as well as decreasing renal damage in SHR. Further, IVA increased renal HCN2 mRNA and reduced cardiac HCN4 mRNA.

Synergy of a STING agonist and an IL-2 superkine in cancer immunotherapy against MHC I-deficient and MHC I+ tumors.

Cyclic dinucleotides (CDN) and Toll-like receptor (TLR) ligands mobilize antitumor responses by natural killer (NK) cells and T cells, potentially serving as complementary therapies to immune checkpoint therapy. In the clinic thus far, however, CDN therapy targeting stimulator of interferon genes (STING) protein has yielded mixed results, perhaps because it initiates responses potently but does not provide signals to sustain activation and proliferation of activated cytotoxic lymphocytes. To improve efficacy, we combined CDN with a half life-extended interleukin-2 (IL-2) superkine, H9-MSA (mouse serum albumin). CDN/H9-MSA therapy induced dramatic long-term remissions of the most difficult to treat major histocompatibility complex class I (MHC I)­deficient and MHC I+ tumor transplant models. H9-MSA combined with CpG oligonucleotide also induced potent responses. Mechanistically, tumor elimination required CD8 T cells and not NK cells in the case of MHC I+ tumors and NK cells but not CD8 T cells in the case of MHC-deficient tumors. Furthermore, combination therapy resulted in more prolonged and more intense NK cell activation, cytotoxicity, and expression of cytotoxic effector molecules in comparison with monotherapy. Remarkably, in a primary autochthonous sarcoma model that is refractory to PD-1 checkpoint therapy, the combination of CDN/H9-MSA with checkpoint therapy yielded long-term remissions in the majority of the animals, mediated by T cells and NK cells. This combination therapy has the potential to activate responses in tumors resistant to current therapies and prevent MHC I loss accompanying acquired resistance of tumors to checkpoint therapy.

Au naturale: use of biologically derived cyclic di-nucleotides for cancer immunotherapy.

Cyclic di-nucleotides (CDNs) are widespread second messenger signalling molecules that regulate fundamental biological processes across the tree of life. These molecules are also potent modulators of the immune system, inducing a Type I interferon response upon binding to the eukaryotic receptor STING. Such a response in tumours induces potent immune anti-cancer responses and thus CDNs are being developed as a novel cancer immunotherapy. In this review, I will highlight the use, challenges and advantages of using naturally occurring CDNs to treat cancer.

Refractoriness of STING therapy is relieved by AKT inhibitor through effective vascular disruption in tumour.

Stimulator of interferon genes (STING) promotes anti-tumour immunity by linking innate and adaptive immunity, but it remains unclear how intratumoural treatment with STING agonists yields anti-tumour effects. Here we demonstrate that intratumoural injection of the STING agonist cGAMP induces strong, rapid, and selective apoptosis of tumour endothelial cells (ECs) in implanted LLC tumour, melanoma and breast tumour, but not in spontaneous breast cancer and melanoma. In both implanted and spontaneous tumours, cGAMP greatly increases TNFα from tumour-associated myeloid cells. However, compared to spontaneous tumour ECs, implanted tumour ECs are more vulnerable to TNFα-TNFR1 signalling-mediated apoptosis, which promotes effective anti-tumour activity. The spontaneous tumour's refractoriness to cGAMP is abolished by co-treatment with AKT 1/2 inhibitor (AKTi). Combined treatment with cGAMP and AKTi induces extensive tumour EC apoptosis, leading to extensive tumour apoptosis and marked growth suppression of the spontaneous tumour. These findings propose an advanced avenue for treating primary tumours that are refractory to single STING agonist therapy.

Identification of Novel Carbocyclic Pyrimidine Cyclic Dinucleotide STING Agonists for Antitumor Immunotherapy Using Systemic Intravenous Route.

Stimulator of Interferon Genes (STING) plays an important role in innate immunity by inducing type I interferon production upon infection with intracellular pathogens. STING activation can promote increased T-cell activation and inflammation in the tumor microenvironment, resulting in antitumor immunity. Natural and synthetic cyclic dinucleotides (CDNs) are known to activate STING, and several synthetic CDN molecules are being investigated in the clinic using an intratumoral administration route. Here, we describe the identification of STING agonist 15a, a cyclic dinucleotide structurally diversified from natural ligands with optimized properties for systemic intravenous (iv) administration. Our studies have shown that STING activation by 15a leads to an acute innate immune response as measured by cytokine secretion and adaptive immune response via activation of CD8+ cytotoxic T-cells, which ultimately provides robust antitumor efficacy.

Established T Cell-Inflamed Tumors Rejected after Adaptive Resistance Was Reversed by Combination STING Activation and PD-1 Pathway Blockade.

Patients with head and neck squamous cell carcinoma harbor T cell-inflamed and non-T cell-inflamed tumors. Despite this, only 20% of patients respond to checkpoint inhibitor immunotherapy. Lack of induction of innate immunity through pattern-recognition receptors, such as the stimulator of interferon (IFN) genes (STING) receptor, may represent a significant barrier to the development of effective antitumor immunity. Here, we demonstrate robust control of a T cell-inflamed (MOC1), but not non-T cell-inflamed (MOC2), model of head and neck cancer by activation of the STING pathway with the synthetic cyclic dinucleotide RP,RP dithio-c-di-GMP. Rejection or durable tumor control of MOC1 tumors was dependent upon a functional STING receptor and CD8 T lymphocytes. STING activation resulted in increased tumor microenvironment type 1 and type 2 IFN and greater expression of PD-1 pathway components in vivo Established MOC1 tumors were rejected and distant tumors abscopally controlled, after adaptive immune resistance had been reversed by the addition of PD-L1 mAb. These findings suggest that PD-1 pathway blockade may reverse adaptive immune resistance following cyclic dinucleotide treatment, enhancing both local and systemic antitumor immunity. Cancer Immunol Res; 4(12); 1061-71. ©2016 AACR.

DMXAA causes tumor site-specific vascular disruption in murine non-small cell lung cancer, and like the endogenous non-canonical cyclic dinucleotide STING agonist, 2'3'-cGAMP, induces M2 macrophage repolarization.

The vascular disrupting agent 5,6-dimethylxanthenone-4-acetic acid (DMXAA), a murine agonist of the stimulator of interferon genes (STING), appears to target the tumor vasculature primarily as a result of stimulating pro-inflammatory cytokine production from tumor-associated macrophages (TAMs). Since there were relatively few reports of DMXAA effects in genetically-engineered mutant mice (GEMM), and models of non-small cell lung cancer (NSCLC) in particular, we examined both the effectiveness and macrophage dependence of DMXAA in various NSCLC models. The DMXAA responses of primary adenocarcinomas in K-rasLA1/+ transgenic mice, as well as syngeneic subcutaneous and metastatic tumors, generated by a p53R172HΔg/+; K-rasLA1/+ NSCLC line (344SQ-ELuc), were assessed both by in vivo bioluminescence imaging as well as by histopathology. Macrophage-dependence of DMXAA effects was explored by clodronate liposome-mediated TAM depletion. Furthermore, a comparison of the vascular structure between subcutaneous tumors and metastases was carried out using micro-computed tomography (micro-CT). Interestingly, in contrast to the characteristic hemorrhagic necrosis produced by DMXAA in 344SQ-ELuc subcutaneous tumors, this agent failed to cause hemorrhagic necrosis of either 344SQ-ELuc-derived metastases or autochthonous K-rasLA1/+ NSCLCs. In addition, we found that clodronate liposome-mediated depletion of TAMs in 344SQ-ELuc subcutaneous tumors led to non-hemorrhagic necrosis due to tumor feeding-vessel occlusion. Since NSCLC were comprised exclusively of TAMs with anti-inflammatory M2-like phenotype, the ability of DMXAA to re-educate M2-polarized macrophages was examined. Using various macrophage phenotypic markers, we found that the STING agonists, DMXAA and the non-canonical endogenous cyclic dinucleotide, 2'3'-cGAMP, were both capable of re-educating M2 cells towards an M1 phenotype. Our findings demonstrate that the choice of preclinical model and the anatomical site of a tumor can determine the vascular disrupting effectiveness of DMXAA, and they also support the idea of STING agonists having therapeutic utility as TAM repolarizing agents.

Cyclic nucleotide-based therapeutics for chronic obstructive pulmonary disease.

Chronic obstructive pulmonary disease (COPD) defines a group of chronic inflammatory disorders of the airways that are characterised by a progressive and largely irreversible decline in expiratory airflow. Drugs used to treat COPD through actions mediated by cyclic AMP (cAMP) are restricted to long-acting and short-acting ß2-adrenoceptor agonists and, in a subset of patients with chronic bronchitis, a phosphodiesterase 4 inhibitor, roflumilast. These agents relax airway smooth muscle and suppress inflammation. At the molecular level, these effects in the airways are mediated by two cAMP effectors, cAMP-dependent protein kinase and exchange proteins activated by cAMP. The pharmacology of newer agents, acting through these systems, is discussed here with an emphasis on their potential to interact and increase therapeutic effectiveness.

Corneal epithelial healing rates after topical nucleotides.

Discrete 28mm2 epithelial lesions in paired rabbit corneas were treated four times daily with either vehicle alone or 10(-2)M or 10(-3)M Db cAMP in the presence or absence of either theophylline (10(-2)M) or epinephrine (5.5 x 10(-3)M). Cyclic GMP was also used either alone or with pilocarpine (1%). The lesion size was determined photographically at various intervals over 48 hours. No treatment regimen at the concentrations of cyclic nucleotides used had any influence on the rate of epithelial regrowth.

2',3'-Bis(2-chloroethyl)aminophosphoryl-3'-amino-3'-deoxyadenosine: a cyclic nucleotide with antitumor activity.

The synthesis of the title compound from 3'-amino-3'-deoxyadenosine in 40% yield is reported. 3'-Amino-3'-deoxyadenosine was made by an improved synthesis in 12 steps from inexpensive D-xylose in 15% overall yield. Both isomers of the title compound, separated by column chromatography, possess confirmed activity against KB tumor cell cultures.

Synthesis and anti-DNA -virus activity of the 5'-monophosphate and the cyclic 3',5'-monophosphate of 9-(beta-D-xylofuranosyl) guanine.

9-(beta-TD-xylofuranosyl)guanine (xylo-G) was converted chemically to the 9-(beta-D-xylofuranosyl)guanine 5'-monophosphate (xylo-GMP) and 9-(beta-D-xylofuranosyl)guanine cyclic 3',5'-monophosphate (c-xylo-GMP). These compounds were tested against a variety of DNA viruses in tissue culture in parallel with 9-(beta-D-arabinofuranosyl)adenine (ara-A). This evaluation revealed that xylo-G, xylo-GMP, and c-xylo-GMP were all moderately active but less effective than ara-A. When the four compounds were administered intracerebrally as a treatment for herpes virus, type 1 induced encephalitis in mice, c-xylo-GMP exhibited superior activity to that shown by the other three. When administered intraperitoneally, c-xylo-GMP was found to have a therapeutic index of about 4, which is less than that for ara-A (approximately 30) in the same system.

Feedback inhibition by 6-methylthioinosine 3',5'-cyclic monophosphate in tumor cells resistant to the nucleoside.

The 3',5'-cyclic phosphate derivative (cMTIMP) of methylthioinosine (MTI) was shown to produce feedback inhibition of the de novo purine pathway in an Ehrlich ascites tumor subline resistant to MTI because of lack of adenosine kinase activity for the nucleoside analog.

Synthesis and biological activity of some 8-substituted selenoguanosine cyclic 3',5'-phosphates and related compounds.

8-Bromoguanosine cyclic 3',5'-monophosphate, 8-bromoguanosine 5'-monophosphate, and 8-bromoguanosine served as intermediates for the chemical synthesis of a series of 8-substituted seleno cyclic nucleotides, nucleotides, and their nucleosides. Selenourea was found to be a useful reagent in synthesizing these seleno-substituted nucleoside, nucleotide, and cyclic nucleotide. A nucleic acid analyzer was used to study the hydrolysis of these cyclic nucleotides by phosphodiesterase. It was found that all of the 8-substituted selenoguanosine cyclic 3',5'-phosphates synthesized, except 8-MeSe-cGMP, were resistant to hydrolyze by phosphodiesterase. These 8-substituted seleno cyclic GMP derivatives showed some antitumor activities against murine leukemic cells (L5178Y) in vitro and in vivo.