Novel mannopyranoside esters as sterol 14α-demethylase inhibitors: Synthesis, PASS predication, molecular docking, and pharmacokinetic studies.

Direct unimolar one-step valeroylation of methyl α-d-mannopyranoside (MDM) furnished mainly 6-O-valeroate. However, similar reaction catalyzed by DMAP resulted 3,6-di-O-valeroate (21%) and 6-O-valeroate (47%) indicating reactivity sequence as 6-OH>3-OH>2-OH,4-OH. To get potential antimicrobial agents, 6-O-valeroate was converted into four 2,3,4-di-O-acyl esters, and 3,6-di-O-valeroate was converted into 2,4-di-O-acetate. Direct tetra-O-valeroylation of MDM gave a mixture of 2,3,4,6-tetra-O-valeroate and 2,3,6-tri-O-valeroate indicating that the C2-OH is more reactive than the equatorial C4-OH. The activity spectra analysis along with in vitro antimicrobial evaluation clearly indicated that these novel MDM esters had better antifungal activities over antibacterial agents. In this connection, molecular docking indicated that these MDM esters acted as competitive inhibitors of sterol 14α-demethylase (CYP51), an essential enzyme for clinical target to cure several infectious diseases. Furthermore, pharmacokinetic studies revealed that these MDM esters may be worth considering as potent candidates for oral and topical administration. Structure activity relationship (SAR) affirmed that saturated valeric chain (C5) in combination with caprylic (C8) chains was more promising CYP51 inhibitor over conventional antifungal antibiotics.

Evaluation of topical econazole nitrate formulations with potential for treating Raynaud's phenomenon.

The purpose of this work was to design and characterize a topical formulation of econazole nitrate (EN) with potential for treating Raynaud's phenomenon (RP). Four topical dosage forms (F1_topical solution, F2_HPMC or hydroxypropyl methylcellulose dispersion, F3_VersaBase® cream, and F4_Lipoderm® Activemax™ Cream) containing 3% w/w EN were prepared and characterized for drug content, pH, viscosity, spreadability, drug crystallinity, stability, and in vitro permeation using Franz cells across pig ear skin, and results were compared to the 1% marketed EN cream. All four formulations had acceptable physical and visual characteristics required for topical application, with 3% w/w EN. The order of amount of drug permeated from highest to lowest was F2 (10.27%) > F4 (2.47%) > F1 (2.28%) > F3 (1.47%) > marketed formulation (0.22%). Formulation F2 showed better penetration of the drug into the stratum corneum, epidermis, and dermis layers. The drug concentration in the stratum corneum and epidermis was approximately 10-20 times higher with F2 compared to the marketed formulation. All formulations were found to be stable for up to 6 months. All four EN formulations were found to be better than the 1% marketed cream. Formulation F2_HPMC dispersion could be further explored as a treatment option for RP.

Evaluation of VT-1161 for Treatment of Coccidioidomycosis in Murine Infection Models.

Coccidioidomycosis, or valley fever, is a growing health concern endemic to the southwestern United States. Safer, more effective, and more easily administered drugs are needed especially for severe, chronic, or unresponsive infections. The novel fungal CYP51 inhibitor VT-1161 demonstrated in vitro antifungal activity, with MIC50 and MIC90 values of 1 and 2 µg/ml, respectively, against 52 Coccidioides clinical isolates. In the initial animal study, oral doses of 10 and 50 mg/kg VT-1161 significantly reduced fungal burdens and increased survival time in a lethal respiratory model in comparison with treatment with a placebo (P < 0.001). Oral doses of 25 and 50 mg/kg VT-1161 were similarly efficacious in the murine central nervous system (CNS) model compared to placebo treatment (P < 0.001). All comparisons with the positive-control drug, fluconazole at 50 mg/kg per day, demonstrated either statistical equivalence or superiority of VT-1161. VT-1161 treatment also prevented dissemination of infection from the original inoculation site to a greater extent than fluconazole. Many of these in vivo results can be explained by the long half-life of VT-1161 leading to sustained high plasma levels. Thus, the efficacy and pharmacokinetics of VT-1161 are attractive characteristics for long-term treatment of this serious fungal infection.

Antitrypanosomal Treatment with Benznidazole Is Superior to Posaconazole Regimens in Mouse Models of Chagas Disease.

Two CYP51 inhibitors, posaconazole and the ravuconazole prodrug E1224, were recently tested in clinical trials for efficacy in indeterminate Chagas disease. The results from these studies show that both drugs cleared parasites from the blood of infected patients at the end of the treatment but that parasitemia rebounded over the following months. In the current study, we sought to identify a dosing regimen of posaconazole that could permanently clear Trypanosoma cruzi from mice with experimental Chagas disease. Infected mice were treated with posaconazole or benznidazole, an established Chagas disease drug, and parasitological cure was defined as an absence of parasitemia recrudescence after immunosuppression. Twenty-day therapy with benznidazole (10 to 100 mg/kg of body weight/day) resulted in a dose-dependent increase in antiparasitic activity, and the 100-mg/kg regimen effected parasitological cure in all treated mice. In contrast, all mice remained infected after a 25-day treatment with posaconazole at all tested doses (10 to 100 mg/kg/day). Further extension of posaconazole therapy to 40 days resulted in only a marginal improvement of treatment outcome. We also observed similar differences in antiparasitic activity between benznidazole and posaconazole in acute T. cruzi heart infections. While benznidazole induced rapid, dose-dependent reductions in heart parasite burdens, the antiparasitic activity of posaconazole plateaued at low doses (3 to 10 mg/kg/day) despite increasing drug exposure in plasma. These observations are in good agreement with the outcomes of recent phase 2 trials with posaconazole and suggest that the efficacy models combined with the pharmacokinetic analysis employed here will be useful in predicting clinical outcomes of new drug candidates.

Binding mode and potency of N-indolyloxopyridinyl-4-aminopropanyl-based inhibitors targeting Trypanosoma cruzi CYP51.

Chagas disease is a chronic infection in humans caused by Trypanosoma cruzi and manifested in progressive cardiomyopathy and/or gastrointestinal dysfunction. Limited therapeutic options to prevent and treat Chagas disease put 8 million people infected with T. cruzi worldwide at risk. CYP51, involved in the biosynthesis of the membrane sterol component in eukaryotes, is a promising drug target in T. cruzi. We report the structure-activity relationships (SAR) of an N-arylpiperazine series of N-indolyloxopyridinyl-4-aminopropanyl-based inhibitors designed to probe the impact of substituents in the terminal N-phenyl ring on binding mode, selectivity and potency. Depending on the substituents at C-4, two distinct ring binding modes, buried and solvent-exposed, have been observed by X-ray structure analysis (resolution of 1.95-2.48 Å). The 5-chloro-substituted analogs 9 and 10 with no substituent at C-4 demonstrated improved selectivity and potency, suppressing ≥ 99.8% parasitemia in mice when administered orally at 25 mg/kg, b.i.d., for 4 days.

4-Aminopyridyl-based CYP51 inhibitors as anti-Trypanosoma cruzi drug leads with improved pharmacokinetic profile and in vivo potency.

CYP51 is a P450 enzyme involved in the biosynthesis of the sterol components of eukaryotic cell membranes. CYP51 inhibitors have been developed to treat infections caused by fungi, and more recently the protozoan parasite Trypanosoma cruzi, the causative agent of Chagas disease. To specifically optimize drug candidates for T. cruzi CYP51 (TcCYP51), we explored the structure-activity relationship (SAR) of a N-indolyl-oxopyridinyl-4-aminopropanyl-based scaffold originally identified in a target-based screen. This scaffold evolved via medicinal chemistry to yield orally bioavailable leads with potent anti-T. cruzi activity in vivo. Using an animal model of infection with a transgenic T. cruzi Y luc strain expressing firefly luciferase, we prioritized the biaryl and N-arylpiperazine analogues by oral bioavailability and potency. The drug-target complexes for both scaffold variants were characterized by X-ray structure analysis. Optimization of both binding mode and pharmacokinetic properties of these compounds led to potent inhibitors against experimental T. cruzi infection.

Nano-amorphous spray dried powder to improve oral bioavailability of itraconazole.

The objective of this study was to formulate nano-amorphous spray-dried powders of itraconazole to enhance its oral bioavailability. A combination approach of solvent-antisolvent precipitation followed by spray drying was used. DoE studies were utilized to understand the critical processing parameters: antisolvent-to-solvent ratio, drug concentration and stabilizer concentration. Particle size was the critical quality attribute. Spray drying of the nano-precipitated formulation was performed with several auxiliary excipients to obtain nano-sized amorphous powder formulations. PLM, DSC and PXRD were utilized to characterize the spray-dried powders. In vitro dissolution and in vivo bioavailability studies of the nano-amorphous powders were performed. The particle size of the nano-formulations was dependent on the drug concentration. The smallest size precipitates were obtained with low drug concentration. All high molecular weight auxiliary excipients and mannitol containing formulations were unstable and crystallized during spray drying. Formulations containing disaccharides were amorphous and non-aggregating. In vitro dissolution testing and in vivo studies showed the superior performance of nano-amorphous formulations compared to melt-quench amorphous and crystalline itraconazole formulations. This study shows superior oral bioavailability of nano-amorphous powders compared to macro-amorphous powders. The nano-amorphous formulation showed similar bioavailability to the nano-crystalline formulation but with a faster absorption profile.

Antitrypanosomal lead discovery: identification of a ligand-efficient inhibitor of Trypanosoma cruzi CYP51 and parasite growth.

Chagas disease is caused by the intracellular protozoan parasite Trypanosomal cruzi , and current drugs are lacking in terms of desired safety and efficacy profiles. Following on a recently reported high-throughput screening campaign, we have explored initial structure-activity relationships around a class of imidazole-based compounds. This profiling has uncovered compounds 4c (NEU321) and 4j (NEU704), which are potent against in vitro cultures of T. cruzi and are greater than 160-fold selective over host cells. We report in vitro drug metabolism and properties profiling of 4c and show that this chemotype inhibits the T. cruzi CYP51 enzyme, an observation confirmed by X-ray crystallographic analysis. We compare the binding orientation of 4c to that of other, previously reported inhibitors. We show that 4c displays a significantly better ligand efficiency and a shorter synthetic route over previously disclosed CYP51 inhibitors, and should therefore be considered a promising lead compound for further optimization.

Voriconazole in clinical practice.

Invasive fungal diseases are associated with significant morbidity and mortality in immunocompromized patients. Voriconazole is the first line treatment of invasive aspergillosis, and has been successfully used in other invasive fungal infections, such as candidiasis, fusariosis or scedosporidiosis. Voriconazole has non-linear pharmacokinetics and undergoes extensive hepatic metabolism by the cytochrome P450 system that depends on age, genetic factors, and interactions with other drugs. Thus, significant interpatient variability is observed after administration of the same dose. Additionally, the therapeutic window is narrow, with high risk of side effects at serum levels 3-5 times higher than the minimal threshold for efficacy. Therefore, the knowledge of pharmacological properties, metabolism, interactions, dosage indications in various populations and side effects is crucial. Therapeutic drug monitoring can help maximize the efficacy and minimize the risk of toxicity. Pharmacological, mycological and clinical aspects of the treatment with voriconazole are summarized in order to optimize its use in daily clinical practice.

Pharmacological characterization, structural studies, and in vivo activities of anti-Chagas disease lead compounds derived from tipifarnib.

Chagas disease, caused by the protozoan pathogen Trypanosoma cruzi, remains a challenging infection due to the unavailability of safe and efficacious drugs. Inhibitors of the trypanosome sterol 14α-demethylase enzyme (CYP51), including azole antifungal drugs, are promising candidates for development as anti-Chagas disease drugs. Posaconazole is under clinical investigation for Chagas disease, although the high cost of this drug may limit its widespread use. We have previously reported that the human protein farnesyltransferase (PFT) inhibitor tipifarnib has potent anti-T. cruzi activity by inhibiting the CYP51 enzyme. Furthermore, we have developed analogs that minimize the PFT-inhibitory activity and enhance the CYP51 inhibition. In this paper, we describe the efficacy of the lead tipifarnib analog compared to that of posaconazole in a murine model of T. cruzi infection. The plasma exposure profiles for each compound following a single oral dose in mice and estimated exposure parameters after repeated twice-daily dosing for 20 days are also presented. The lead tipifarnib analog had potent suppressive activity on parasitemia in mice but was unsuccessful at curing mice, whereas posaconazole as well as benznidazole cured 3 of 5 and 4 of 6 mice, respectively. The efficacy results are consistent with posaconazole having substantially higher predicted exposure than that of the tipifarnib analog after repeat twice-daily administration. Further changes to the tipifarnib analogs to reduce plasma clearance are therefore likely to be important. A crystal structure of a trypanosomal CYP51 bound to a tipifarnib analog is reported here and provides new insights to guide structure-based drug design for further optimized compounds.

Effects of CYP3A4 inhibition and induction on the pharmacokinetics and pharmacodynamics of tolvaptan, a non-peptide AVP antagonist in healthy subjects.

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT: Before these trials were done, the effects of CYP3A4 inhibition and induction on the pharmacokinetics (PK) and pharmacodynamics (PD) of tolvaptan in healthy subjects were unknown. As tolvaptan is a CYP3A4 substrate, knowing the effects of inhibition and induction on CYP3A4-mediated metabolism was important for dosing recommendations. WHAT THIS STUDY ADDS: This paper describes the changes in tolvaptan PK and PD following inhibition or induction of CYP3A4 and explores the mechanisms behind the disparity seen between tolvaptan PK and effects on urine output. It also discusses the concentrations at which tolvaptan produces its maximal response on urine output and the timing of the onset and offset of this response. AIMS In vitro studies indicated CYP3A4 alone was responsible for tolvaptan metabolism. To determine the effect of a CYP3A4 inhibitor (ketoconazole) and a CYP3A4 inducer (rifampicin) on tolvaptan pharmacokinetics (PK) and pharmacodynamics (PD), two clinical trials were performed. METHODS: For CYP3A4 inhibition, a double-blind, randomized (5:1), placebo-controlled trial was conducted in 24 healthy subjects given either a single 30 mg dose of tolvaptan (n= 19) or matching placebo (n= 5) on day 1 with a 72 h washout followed by a 3 day regimen of 200 mg ketoconazole, once daily with 30 mg tolvaptan or placebo also given on day 5. For CYP3A4 induction, 14 healthy subjects were given a single dose of 240 mg tolvaptan with 48 h washout followed by a 7 day regimen of 600 mg rifampicin, once daily, with 240 mg tolvaptan also given on the seventh day. RESULTS: When co-administered with ketoconazole, mean C(max) and AUC(0,∞) of tolvaptan were increased 3.48- and 5.40-fold, respectively. Twenty-four hour urine volume increased from 5.9 to 7.7 l. Erythromycin breath testing showed no difference following a single dose of tolvaptan. With rifampicin, tolvaptan mean C(max) and AUC were reduced to 0.13- and 0.17-fold of tolvaptan administered alone. Twenty-four hour urine volume decreased from 12.3 to 8.8 l. CONCLUSIONS: Tolvaptan is a sensitive CYP3A4 substrate with no inhibitory activity. Due to the saturable nature of tolvaptan's effect on urine excretion rate, changes in the pharmacokinetic profile of tolvaptan do not produce proportional changes in urine output.

Pharmacokinetic interaction between domperidone and ketoconazole leads to QT prolongation in healthy volunteers: a randomized, placebo-controlled, double-blind, crossover study.

AIMS: To assess the steady-state pharmacokinetic and QT(c) effects of domperidone and ketoconazole, given alone and together. METHODS: A randomized, placebo-controlled, double-blind, crossover study was carried out. Healthy subjects (14 men, 10 women; age 18-39 years; mean weight 73.5kg, range 53.8-98.8kg; 23 Europid, 1 Afro-Caribbean) received orally, for 7 days each, placebo, domperidone 10mg, four doses daily, at 4h intervals, ketoconazole 200mg 12-hourly and domperidone and ketoconazole together. The washout period was 15 days. Pharmacokinetics and serial 12-lead ECGs were assessed on day 7, and serial ECGs on day -1 and at follow-up. Two subjects withdrew before the third treatment period, so data were available for 22-24 subjects. RESULTS Ketoconazole tripled domperidone concentrations at steady-state. Domperidone, ketoconazole and their combination significantly increased QT(c) F in men. Overall adjusted mean differences from placebo were 4.20 (95% CI 0.77, 7.63), 9.24 (95% CI 5.85, 12.63) and 15.90 (95% CI 12.47, 19.33) ms, respectively. In women, QT(c) F was not significantly different from placebo on either domperidone or ketoconazole alone, or in combination. However, QT(c) was positively correlated with plasma drug concentrations, in both men and women. ΔQT(c) F increased by about 2ms per 10ngml(-1) rise in domperidone concentration, and per 1µgml(-1) rise in ketoconazole concentration. CONCLUSIONS: Ketoconazole tripled the plasma concentrations of domperidone. Domperidone and ketoconazole increased QT(c) F in men, whether given together or separately. The effect of domperidone alone was below the level of clinical importance. The negative result in women is unexplained.

Effects of strong CYP2D6 and 3A4 inhibitors, paroxetine and ketoconazole, on the pharmacokinetics and cardiovascular safety of tamsulosin.

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT: Tamsulosin metabolism involves both CYP2D6 and 3A4. However, data on potential drug-drug interactions between tamsulosin and inhibitors of CYP2D6 and 3A4 are limited and information on potential pharmacodynamic consequences of such pharmacokinetic interactions is missing. WHAT THIS STUDY ADDS: This study provides information on the drug-drug interactions of tamsulosin with strong CYP2D6 and strong CYP3A4 inhibitors after single dose administration in healthy subjects. AIM: To determine the effect of the strong CYP2D6 inhibitor paroxetine and strong CYP3A4 inhibitor ketoconazole on the pharmacokinetics and safety (orthostatic challenge) of tamsulosin. METHODS: Two open-label, randomized, two-way crossover studies were conducted in healthy male volunteers (extensive CYP2D6 metabolizers). RESULTS: Co-administration of multiple oral doses of 20 mg paroxetine once daily with a single oral dose of the 0.4 mg tamsulosin HCl capsule increased the adjusted geometric mean (gMean) values of C(max) and AUC(0,∞) of tamsulosin by factors of 1.34 (90% CI 1.21, 1.49) and 1.64 (90% CI 1.44, 1.85), respectively, and increased the terminal half-life (t(1/2) ) of tamsulosin HCl from 11.4 h to 15.3 h. Co-administration of multiple oral doses of 400 mg ketoconazole once daily with a single oral dose of the 0.4 mg tamsulosin increased the gMean values of C(max) and AUC(0,∞) of tamsulosin by a factor of 2.20 (90% CI 1.96, 2.45) and 2.80 (90% CI 2.56, 3.07), respectively. The terminal half-life was slightly increased from 10.5 h to 11.8 h. These pharmacokinetic changes were not accompanied by clinically significant alterations of haemodynamic responses during orthostatic stress testing. CONCLUSION: The exposure to tamsulosin is increased upon co-administration of strong CYP2D6 inhibitors and even more so of strong 3A4 inhibitors, but neither PK alteration was accompanied by clinically significant haemodynamic changes during orthostatic stress testing.