Targeting VLA4 integrin and CXCR2 mobilizes serially repopulating hematopoietic stem cells

Mobilized peripheral blood has become the primary source of hematopoietic stem and progenitor cells (HSPCs) for stem cell transplantation, with a five-day course of granulocyte colony stimulating factor (G-CSF) as the most common regimen used for HSPC mobilization. The CXCR4 inhibitor, plerixafor, is a more rapid mobilizer, yet not potent enough when used as a single agent, thus emphasizing the need for faster acting agents with more predictable mobilization responses and fewer side effects. We sought to improve hematopoietic stem cell transplantation by developing a new mobilization strategy in mice through combined targeting of the chemokine receptor CXCR2 and the very late antigen 4 (VLA4) integrin. Rapid and synergistic mobilization of HSPCs along with an enhanced recruitment of true HSCs was achieved when a CXCR2 agonist was co-administered in conjunction with a VLA4 inhibitor. Mechanistic studies revealed involvement of CXCR2 expressed on BM stroma in addition to stimulation of the receptor on granulocytes in the regulation of HSPC localization and egress. Given the rapid kinetics and potency of HSPC mobilization provided by the VLA4 inhibitor and CXCR2 agonist combination in mice compared to currently approved HSPC mobilization methods, it represents an exciting potential strategy for clinical development in the future.

Antifungal Phenothiazines: Optimization, Characterization of Mechanism, and Modulation of Neuroreceptor Activity

New classes of antifungal drugs are an urgent unmet clinical need. One approach to the challenge of developing new antifungal drugs is to optimize the antifungal properties of currently used drugs with favorable pharmacologic properties, so-called drug or scaffold repurposing. New therapies for cryptococcal meningitis are particularly important given its worldwide burden of disease and limited therapeutic options. We report the first systematic structure-activity study of the anticryptococcal properties of the phenothiazines. We also show that the antifungal activity of the phenothiazine scaffold correlates well with its calmodulin antagonism properties and, thereby, provides the first insights into the mechanism of its antifungal properties. Guided by this mechanism, we have generated improved trifluoperazine derivatives with increased anticryptococcal activity and, importantly, reduced affinity for receptors that modulate undesired neurological effects. Taken together, these data suggest that phenothiazines represent a potentially useful scaffold for further optimization in the search for new antifungal drugs.

Hepatitis B virus genetic diversity has minimal impact on sensitivity of the viral ribonuclease H to inhibitors

Hepatitis B virus (HBV) causes hepatitis, cirrhosis, liver failure, and liver cancer, but the current therapies that employ either nucelos(t)ide analogs or (pegylated)interferon α do not clear the infection in the large majority of patients. Inhibitors of the HBV ribonuclease H (RNaseH) that are being developed with the goal of producing anti-HBV drugs are promising candidates for use in combination with the nucleos(t)ide analogs to improve therapeutic efficacy. HBV is genetically very diverse, with at least 8 genotypes that differ by ≥8% at the sequence level. This diversity is reflected in the viral RNaseH enzyme, raising the possibility that divergent HBV genotypes or isolates may have varying sensitivity to RNaseH inhibitors. To evaluate this possibility, we expressed and purified 18 patient-derived RNaseHs from genotypes B, C, and D. Basal RNaseH activity and sensitivity to three novel RNaseH inhibitors from three different chemotypes were assessed. We also evaluated four consensus HBV RNaseHs to determine if such sequences would be suitable for use in antiviral drug screening. The patient-derived enzymes varied by over 10-fold in their basal RNaseH activities, but they were equivalently sensitive to each of the three inhibitors. Similarly, all four consensus HBV RNaseH enzymes were active and were equally sensitive to an RNaseH inhibitor. These data indicate that a wide range of RNaseH sequences would be suitable for use in antiviral drug screening, and that genotype- or isolate-specific genetic variations are unlikely to present a barrier during antiviral drug development against the HBV RNaseH.

IL-13-induced airway mucus production is attenuated by MAPK13 inhibition

Increased mucus production is a common cause of morbidity and mortality in inflammatory airway diseases, including asthma, chronic obstructive pulmonary disease (COPD), and cystic fibrosis. However, the precise molecular mechanisms for pathogenic mucus production are largely undetermined. Accordingly, there are no specific and effective anti-mucus therapeutics. Here, we define a signaling pathway from chloride channel calcium-activated 1 (CLCA1) to MAPK13 that is responsible for IL-13-driven mucus production in human airway epithelial cells. The same pathway was also highly activated in the lungs of humans with excess mucus production due to COPD. We further validated the pathway by using structure-based drug design to develop a series of novel MAPK13 inhibitors with nanomolar potency that effectively reduced mucus production in human airway epithelial cells. These results uncover and validate a new pathway for regulating mucus production as well as a corresponding therapeutic approach to mucus overproduction in inflammatory airway diseases.

Self-cleavage of human CLCA1 protein by a novel internal metalloprotease domain controls calcium-activated chloride channel activation

The chloride channel calcium-activated (CLCA) family are secreted proteins that regulate both chloride transport and mucin expression, thus controlling the production of mucus in respiratory and other systems. Accordingly, human CLCA1 is a critical mediator of hypersecretory lung diseases, such as asthma, chronic obstructive pulmonary disease, and cystic fibrosis, that manifest mucus obstruction. Despite relevance to homeostasis and disease, the mechanism of CLCA1 function remains largely undefined. We address this void by showing that CLCA proteins contain a consensus proteolytic cleavage site recognized by a novel zincin metalloprotease domain located within the N terminus of CLCA itself. CLCA1 mutations that inhibit self-cleavage prevent activation of calcium-activated chloride channel (CaCC)-mediated chloride transport. CaCC activation requires cleavage to unmask the N-terminal fragment of CLCA1, which can independently gate CaCCs. Gating of CaCCs mediated by CLCA1 does not appear to involve proteolytic cleavage of the channel because a mutant N-terminal fragment deficient in proteolytic activity is able to induce currents comparable with that of the native fragment. These data provide both a mechanistic basis for CLCA1 self-cleavage and a novel mechanism for regulation of chloride channel activity specific to the mucosal interface.

Aminopyridinecarboxamide-based inhaled IKK-2 inhibitors for asthma and COPD: Structure-activity relationship

Installation of sites for metabolism in the lead compound PHA-767408 was the key focus of the IKK-2 inhaled program. This paper reports our efforts to identify a novel series of aminopyridinecarboxamide-based IKK-2 inhibitors, which display low nanomolar potency against IKK-2 with long duration of action (DOA), and metabolically labile to phase I and/or phase II metabolizing enzymes with potential capability for multiple routes of clearance. Several compounds have demonstrated their potential usefulness in the treatment of asthma and chronic obstructive pulmonary disease (COPD).

Dopaminergic and serotonergic activities of imidazoquinolinones and related compounds

The synthesis of 5-(dipropylamino)-5,6-dihydro-4H-imidazo[4,5,1-ij] quinolin-2(1H)-one (5), a potent dopamine D2 agonist showing high dopamine/serotonin (5HT1A) selectivity, is described. Dopaminergic activity is associated with the (R)-enantiomer of 5; the (S)-enantiomer shows no dopaminergic activity. A series of analogues where the imidazolone ring was modified to various 5- or 6-membered heterocyclic rings were prepared. Some of these compounds showed a combination of dopaminergic and serotonergic activity, while one compound, 6-(dipropylamino)-1,2,6,7-tetrahydro-3H,5H-pyrido[3,2,1- ij]quinazolin-3-one (24), was a selective serotonergic agonist. Various analogues of 5 where the dipropylamine substituent was modified were prepared. Most of these showed reduced dopaminergic activity, while several were as potent as 5 at the serotonin 5HT1A receptor. Orientations for the new compounds at dopamine and serotonin receptors are proposed and compared with those of other tricyclic ligands known to have high affinity at these receptors.

A Convergent, Scalable Synthesis of HIV Protease Inhibitor PNU-140690

PNU-140690, an inhibitor of the HIV protease enzyme undergoing clinical evalution as a chemotherapeutic agent for treatment of AIDS, was synthesized by a convergent approach amenable to large-scale preparation in a pilot plant environment. The key step is the aldol addition of nitroaromatic ester (+)-8 to aldehyde 19e. The two stereocenters present in the target molecule were each set independently by resolution of enantiomers. Intermediates along the synthetic routes were chosen to maximize opportunities for isolation and purification by crystallization.

Synthesis and biological activities of (R)-5,6-dihydro-N,N-dimethyl-4H-imidazo[4,5,1-ij]quinolin-5-amine and its metabolites

The imidazoquinoline (R)-5,6-Dihydro-N,N-dimethyl-4H-imidazo[4,5,1-ij]quinolin-5-amine [(R)-3] is a potent dopamine agonist when tested in animals but surprisingly shows very low affinity in in vitro binding assays. When incubated with mouse or monkey liver S9 microsomes, (R)-3 is metabolized by N-demethylation and oxidation to (R)-5,6-dihydro-5-(methylamino)-4H-imidazo[4,5,1-ij]quinolin-2(1H) -one [(R)-6], intermediate metabolites, where N-demethylation to the imidazoquinoline (R)-4 and where oxidation to the imidazoquinolinone (R)-5 has taken place, are also observed in these incubates. A cross-species study on the metabolism of (R)-3 in vitro has shown large variations in the extent of metabolism from species to species. Imidazoquinolinones (R)-5 and (R)-6 have comparable activity to (R)-3 in animals and also show good dopaminergic (D2) and serotonergic (5HT1A) activities in binding assays. It is probable that these metabolites account at least in part for the in vivo activity found for (R)-3. Efficient syntheses for compounds 3-6 as single enantiomers from quinoline are presented together with information on the biological activities and metabolic stabilities of these compounds.

Medicinal chemistry of imidazoquinolinone dopamine receptor agonists

(R)-5-(Dipropylamino)-5,6-dihydro-4H-imidazo[4,5,1-ij]-quinolin-2( 1H)-on e (1a, U-86170), a potent high intrinsic activity dopamine (D2) agonist, has been prepared in eleven steps from quinoline. In several tests, the compound showed dopamine autoreceptor agonist activity at low doses. It showed postsynaptic agonist activity at somewhat higher doses, reversing the effects of reserpine in mice and increasing striatal acetylcholine levels. The compound showed some serotonergic (5HT1A) activity, but was inactive at other receptors. The related monopropylamine 2 (U-91356), also showed good dopaminergic agonist activity, and had improved metabolic stability and oral bioavailability in the rat and monkey when compared to 1a. Compounds 1a and 2 have been prepared in tritiated form, and [3H]1a (69 Ci/mmol) has found use as a D2 agonist radioligand in binding assays. The dopaminergic (D2) and serotonergic (5HT1A) activities of a series of compounds related to 1a have been evaluated using this ligand, [3H]raclopride, and [3H]8-OH DPAT.

alpha-Methyl analogues of acetylenic amines as striatal muscarinic antagonists

The effect of acetylenic amines, with or without alpha-methyl substitution, on striatal acetylcholine (ACh) concentration in rats was investigated. Oxotremorine, oxotremorine-1, and U-77053 (trimethyl (4-(1-pyrrolidinyl)-2 butynyl)-urea), the unsubstituted amines, increased striatal ACh concentration. On the other hand, the corresponding alpha-methyl substituted analogues, alpha-methyl-oxotremorine, BM-5, and alpha-methyl U-77053, decreased the concentration of ACh in the striatum. The results indicate that substitution of alpha-methyl in acetylenic amines converts compounds from agonists to antagonists for striatal muscarinic receptors.

Cholinergic activity of acetylenic imidazoles and related compounds

A series of acetylenic imidazoles related to oxotremorine (1a) were prepared and evaluated as cholinergic agents with in vitro binding assays and in vivo pharmacological tests in mice. 1-[4-(1H-Imidazol-1-yl)-2-butynyl]-2-pyrrolidinone (1b) was a cholinergic agonist with one-half the potency of oxotremorine. Analogues of 1b with a 5- or 2-methyl substituent in the imidazole ring (compounds 1c and 1g) were cholinergic partial agonists. Analogues of 1b with a methyl substituent at the 5-position in the pyrrolidinone ring (7b) or at the alpha-position in the acetylenic chain (8b) were antagonists. Various analogues of these imidazole acetylenes where the pyrrolidinone ring was replaced by an amide, carbamate, or urea residue were prepared. Several compounds which contained 5-methylimidazole as the amine substituent were partial agonists. The activities of the imidazole compounds are compared with those of the related pyrrolidine and dimethylamine analogues. Agonist and antagonist conformations for these compounds at muscarinic receptors are proposed.