A New PqsR Inverse Agonist Potentiates Tobramycin Efficacy to Eradicate Pseudomonas aeruginosa Biofilms.

Pseudomonas aeruginosa (PA) infections can be notoriously difficult to treat and are often accompanied by the development of antimicrobial resistance (AMR). Quorum sensing inhibitors (QSI) acting on PqsR (MvfR) - a crucial transcriptional regulator serving major functions in PA virulence - can enhance antibiotic efficacy and eventually prevent the AMR. An integrated drug discovery campaign including design, medicinal chemistry-driven hit-to-lead optimization and in-depth biological profiling of a new QSI generation is reported. The QSI possess excellent activity in inhibiting pyocyanin production and PqsR reporter-gene with IC50 values as low as 200 and 11 × 10-9 m, respectively. Drug metabolism and pharmacokinetics (DMPK) as well as safety pharmacology studies especially highlight the promising translational properties of the lead QSI for pulmonary applications. Moreover, target engagement of the lead QSI is shown in a PA mucoid lung infection mouse model. Beyond that, a significant synergistic effect of a QSI-tobramycin (Tob) combination against PA biofilms using a tailor-made squalene-derived nanoparticle (NP) formulation, which enhance the minimum biofilm eradicating concentration (MBEC) of Tob more than 32-fold is demonstrated. The novel lead QSI and the accompanying NP formulation highlight the potential of adjunctive pathoblocker-mediated therapy against PA infections opening up avenues for preclinical development.

Dovitinib enhances temozolomide efficacy in glioblastoma cells.

The multikinase inhibitor and FDA-approved drug dovitinib (Dov) crosses the blood-brain barrier and was recently used as single drug application in clinical trials for GB patients with recurrent disease. The Dov-mediated molecular mechanisms in GB cells are unknown. We used GB patient cells and cell lines to show that Dov downregulated the stem cell protein Lin28 and its target high-mobility group protein A2 (HMGA2). The Dov-induced reduction in pSTAT3Tyr705 phosphorylation demonstrated that Dov negatively affects the STAT3/LIN28/Let-7/HMGA2 regulatory axis in GB cells. Consistent with the known function of LIN28 and HMGA2 in GB self-renewal, Dov reduced GB tumor sphere formation. Dov treatment also caused the downregulation of key base excision repair factors and O6 -methylguanine-DNA-methyltransferase (MGMT), which are known to have important roles in the repair of temozolomide (TMZ)-induced alkylating DNA damage. Combined Dov/TMZ treatment enhanced TMZ-induced DNA damage as quantified by nuclear γH2AX foci and comet assays, and increased GB cell apoptosis. Pretreatment of GB cells with Dov ('Dov priming') prior to TMZ treatment reduced GB cell viability independent of p53 status. Sequential treatment involving 'Dov priming' and alternating treatment cycles with TMZ and Dov substantially reduced long-term GB cell survival in MGMT+ patient GB cells. Our results may have immediate clinical implications to improve TMZ response in patients with LIN28+ /HMGA2+ GB, independent of their MGMT methylation status.

Antinociceptive effects of the selective CB2 agonist MT178 in inflammatory and chronic rodent pain models.

Cannabinoid CB(2) receptor activation by selective agonists has been shown to produce analgesic effects in preclinical models of inflammatory, neuropathic, and bone cancer pain. In this study the effect of a novel CB(2)agonist (MT178) was evaluated in different animal models of pain. First of all, in vitro competition binding experiments performed on rat, mouse, or human CB receptors revealed a high affinity, selectivity, and potency of MT178. The analgesic properties of the novel CB(2) agonist were evaluated in various in vivo experiments, such as writhing and formalin assays, showing a good efficacy comparable with that produced by the nonselective CB agonist WIN 55,212-2. A dose-dependent antiallodynic effect of the novel CB(2) compound in the streptozotocin-induced diabetic neuropathy was found. In a bone cancer pain model and in the acid-induced muscle pain model, MT178 was able to significantly reduce mechanical hyperalgesia in a dose-related manner. Notably, MT178 failed to provoke locomotor disturbance and catalepsy, which were observed following the administration of WIN 55,212-2. CB(2) receptor mechanism of action was investigated in dorsal root ganglia where MT178 mediated a reduction of [(3)H]-d-aspartate release. MT178 was also able to inhibit capsaicin-induced substance P release and NF-κB activation. These results demonstrate that systemic administration of MT178 produced a robust analgesia in different pain models via CB(2) receptors, providing an interesting approach to analgesic therapy in inflammatory and chronic pain without CB(1)-mediated central side effects.

Effects of dopamine D2/D3 receptor ligands on food-cocaine choice in socially housed male cynomolgus monkeys.

Dopamine D2/D3 receptor partial agonists have been suggested as medications for cocaine dependence. The present experiments examined the effect of acute and repeated administration of drugs with varying intrinsic efficacy at D2/D3 receptors on the relative reinforcing strength of cocaine. Use of socially housed cynomolgus monkeys permitted the assessment of whether social status, known to alter D2/D3 receptor availability, influenced the behavioral effects of D2/D3 receptor compounds. The high-efficacy agonist R(-)-norpropylapomorphine [(-)-NPA], low-efficacy agonist aripiprazole (ARI), and antagonist eticlopride (ETIC) were administered acutely to monkeys self-administering cocaine under a food-cocaine choice procedure in which a cocaine self-administration dose-effect curve was determined daily. The effects of 5-day treatment with ARI and (-)-NPA were characterized under conditions in which monkeys did (ARI) or did not [ARI and (-)-NPA] self-administer cocaine during treatment. When administered acutely, ARI and ETIC increased the choice of low cocaine doses, and only (-)-NPA decreased the choice of higher cocaine doses and cocaine intake; effects were similar across social ranks. When administered repeatedly while self administration occurred only on days 1 and 5 of treatment, ARI, but not (-)-NPA, decreased cocaine choice in dominant monkeys, whereas (-)-NPA, but not ARI, did so in subordinates. When dominant monkeys self-administered cocaine on all five days of ARI treatment, however, these effects were not observed. The results indicate that the behavioral effects of D2/D3 receptor agonists can differ according to intrinsic efficacy and subject characteristics. Moreover, these results suggest that exposure to cocaine during treatment can counteract treatment-induced reductions in the reinforcing effects of cocaine.

Onset of action of indacaterol in patients with COPD: comparison with salbutamol and salmeterol-fluticasone.

BACKGROUND: indacaterol is a novel, inhaled once-daily ultra-long-acting ß(2)-agonist for the treatment of chronic obstructive pulmonary disease (COPD). OBJECTIVES: this study compared the onset of action of single doses of indacaterol 150 and 300 µg with salbutamol 200 µg, salmeterol-fluticasone 50/500 µg, and placebo in moderate-to-severe COPD patients. METHODS: this was a multicenter, randomized, double-blind, placebo-controlled crossover study. The primary variable was forced expiratory volume in one second (FEV(1)) at five minutes postdose. RESULTS: out of 89 patients randomized (mean age 62 years), 86 completed the study. At five minutes postdose, both indacaterol doses were statistically and clinically superior to placebo (P < 0.001), with treatment-placebo differences in FEV(1) of 100 (95% confidence interval [CI] 70-130) mL and 120 (95% CI 90-150) mL for indacaterol 150 and 300 µg, respectively. FEV(1) at five minutes postdose with both indacaterol doses was numerically higher than for salbutamol (10 and 30 mL for indacaterol 150 and 300 µg, respectively) and significantly higher than for salmeterol-fluticasone (50 mL, P = 0.003; 70 mL, P < 0.001, respectively). Moreover, both indacaterol doses showed significantly higher FEV(1) than placebo (P < 0.001) at all postdose time points. The numbers of patients with an FEV(1) increase of at least 12% and 200 mL at five minutes postdose were 16 (18.8%), 24 (27.6%), 20 (23.3%), 8 (9.1%), and 3 (3.4%) for indacaterol 150 and 300 µg, salbutamol 200 µg, salmeterol-fluticasone 50/500 µg, and placebo, respectively. CONCLUSIONS: single doses of indacaterol 150 and 300 µg demonstrated a fast onset of action similar to that for salbutamol and faster than that for salmeterol-fluticasone.

Third generation antipsychotic drugs: partial agonism or receptor functional selectivity?

Functional selectivity is the term that describes drugs that cause markedly different signaling through a single receptor (e.g., full agonist at one pathway and antagonist at a second). It has been widely recognized recently that this phenomenon impacts the understanding of mechanism of action of some drugs, and has relevance to drug discovery. One of the clinical areas where this mechanism has particular importance is in the treatment of schizophrenia. Antipsychotic drugs have been grouped according to both pattern of clinical action and mechanism of action. The original antipsychotic drugs such as chlorpromazine and haloperidol have been called typical or first generation. They cause both antipsychotic actions and many side effects (extrapyramidal and endocrine) that are ascribed to their high affinity dopamine D(2) receptor antagonism. Drugs such as clozapine, olanzapine, risperidone and others were then developed that avoided the neurological side effects (atypical or second generation antipsychotics). These compounds are divided mechanistically into those that are high affinity D(2) and 5-HT(2A) antagonists, and those that also bind with modest affinity to D(2), 5-HT(2A), and many other neuroreceptors. There is one approved third generation drug, aripiprazole, whose actions have been ascribed alternately to either D(2) partial agonism or D(2) functional selectivity. Although partial agonism has been the more widely accepted mechanism, the available data are inconsistent with this mechanism. Conversely, the D(2) functional selectivity hypothesis can accommodate all current data for aripiprazole, and also impacts on discovery compounds that are not pure D(2) antagonists.

Las Quinolonas / The Quinolones

La continua lucha que el hombre libera contra gérmenes patógenos ha permitido obtener cada vez mejores y más eficaces antibióticos. Desde la década del sesenta el clínico dispone de un grupo de antimicrobianos que por sus características conforman un grupo especial: Las quinolonas. El entendimiento de su mecanismo de acción, actividad antimicrobiana, interacciones medicamentosas y otros aspectos son pilares básicos para que el médico comprenda y racionalice su uso. La inmensa gama de posibilidades de modificación en su molécula básica, indica que las quinolonas están llamadas a quedarse en el arsenal terapéutico durante varias décadas; de allí la importancia de revisar y actualizar los conceptos que hasta hoy rigen su uso clínico