Pharmacokinetic-pharmacodynamic modeling of telmisartan using an indirect response model in spontaneously hypertensive rats

Dosing time optimization of antihypertensive medications by including the circadian rhythm in pharmacokinetic-pharmacodynamic models

Blood pressure (BP) follows a circadian variation, increasing during active hours, showing a small postprandial valley and a deeper decrease during sleep. Nighttime reduction of 10–20% relative to daytime BP is defined as a dipper pattern, and a reduction of less than 10%, as a non-dipper pattern. Despite this BP variability, hypertension’s diagnostic criteria and therapeutic objectives are usually based on BP average values. Indeed, studies have shown that chrono-pharmacological optimization significantly reduces long-term cardiovascular risk if a BP dipper pattern is maintained. Changes in the effect of antihypertensive medications can be explained by circadian variations in their pharmacokinetics (PK) and pharmacodynamics (PD). Nevertheless, BP circadian variation has been scarcely included in PK-PD models of antihypertensive medications to date. In this work, we developed PK-PD models that include circadian rhythm to find the optimal dosing time (Ta) of first-line antihypertensive medications for dipper and non-dipper patterns. The parameters of the PK-PD models were estimated using global optimization, and models were selected according to the lowest corrected Akaike information criterion value. Simultaneously, sensitivity and identifiability analysis were performed to determine the relevance of the parameters and establish those that can be estimated. Subsequently, Ta parameters were optimized to maximize the effect on BP average, BP peaks, and sleep-time dip. As a result, all selected models included at least one circadian PK component, and circadian parameters had the highest sensitivity. Furthermore, Ta with which BP>130/80 mmHg and a dip of 10–20% are achieved were proposed when possible. We show that the optimal Ta depends on the therapeutic objective, the medication, and the BP profile. Therefore, our results suggest making chrono-pharmacological recommendations in a personalized way.

An Integrative Approach for Improved Assessment of Cardiovascular Safety Data

Cardiovascular adverse effects in drug development are a major source of compound attrition. Characterization of blood pressure (BP), heart rate (HR), stroke volume (SV), and QT-interval prolongation are therefore necessary in early discovery. It is, however, common practice to analyze these effects independently of each other. High-resolution time courses are collected via telemetric techniques, but only low-resolution data are analyzed and reported. This ignores codependencies among responses (HR, BP, SV, and QT-interval) and separation of system (turnover properties) and drug-specific properties (potencies, efficacies). An analysis of drug exposure-time and high-resolution response-time data of HR and mean arterial blood pressure was performed after acute oral dosing of ivabradine, sildenafil, dofetilide, and pimobendan in Han-Wistar rats. All data were modeled jointly, including different compounds and exposure and response time courses, using a nonlinear mixed-effects approach. Estimated fractional turnover rates [h^-1, relative standard error (%RSE) within parentheses] were 9.45 (15), 30.7 (7.8), 3.8 (13), and 0.115 (1.7) for QT, HR, total peripheral resistance, and SV, respectively. Potencies (nM, %RSE within parentheses) were IC ₅₀ = 475 (11), IC ₅₀ = 4.01 (5.4), EC ₅₀ = 50.6 (93), and IC ₅₀ = 47.8 (16), and efficacies (%RSE within parentheses) were I _max = 0.944 (1.7), I_max = 1.00 (1.3), E _max = 0.195 (9.9), and I_max = 0.745 (4.6) for ivabradine, sildenafil, dofetilide, and pimobendan. Hill parameters were estimated with good precision and below unity, indicating a shallow concentration-response relationship. An equilibrium concentration-biomarker response relationship was predicted and displayed graphically. This analysis demonstrates the utility of a model-based approach integrating data from different studies and compounds for refined preclinical safety margin assessment. SIGNIFICANCE STATEMENT: A model-based approach was proposed utilizing biomarker data on heart rate, blood pressure, and QT-interval. A pharmacodynamic model was developed to improve assessment of high-resolution telemetric cardiovascular safety data driven by different drugs (ivabradine, sildenafil, dofetilide, and pimobondan), wherein system- (turnover rates) and drug-specific parameters (e.g., potencies and efficacies) were sought. The model-predicted equilibrium concentration-biomarker response relationships and was used for safety assessment (predictions of 20% effective concentration, for example) of heart rate, blood pressure, and QT-interval.

Analysis of the Relationship between the Expression Levels of Neutrophil Gelatinase-Associated Lipocalin and Cytokine Genes in Bone Marrow

Background: Recently, various associations of NGAL with several hematological cancers have been reported. However, given that the regulation of NGAL gene expression by cytokines is tissue-specific, NGAL expression in relation to those of cytokine genes has not been analyzed in bone marrow (BM) tissue. The purpose of this study was to analyze the association between NGAL and 48 cytokine gene expression levels in mononuclear cells (MNCs) of BM at the time of diagnosis of hematological malignancy and to explore the expression pattern of NGAL and related cytokine genes in patients with hematological malignancies and controls. Methods: BM MNCs were isolated from 48 patients, who were classified as patients presenting myeloproliferative neoplasm, acute myeloid leukemia, myelodysplastic syndrome, and as controls. NGAL and cytokine genes were analyzed using NanoString. Data on hematological parameters were collected from medical records. Single and multiple regression analyses were performed to analyze relationships. Results: Normalized counts of 26 cytokine genes were related to NGAL normalized counts, while STAT3 and TLR4 normalized counts had the highest explanatory power. The following multiple regression model was developed: NGAL normalized counts=4316.825 + 9.056 × STAT3 normalized counts + 844.226 × IL5 normalized counts + 17.540 × TLR1 normalized counts - 28.206 × TLR2 normalized counts - 42.524 × IRAK4 normalized counts. In the multiple regression analysis, STAT3 and TLR4 normalized counts showed multicollinearity. NGAL, STAT3, IL5, and TLR4 normalized counts showed similar intergroup patterns. Conclusions: NGAL normalized counts was predicted by a multiple regression model, while they showed similar intergroup patterns to STAT3, IL5, and TLR4 normalized counts.

Association of peripheral blood neutrophil gelatinase-associated lipocalin levels with bone marrow neutrophil gelatinase-associated lipocalin levels and neutrophil count in hematologic malignancy

Background

Although neutrophil gelatinase‐associated lipocalin (NGAL) is a biomarker for acute kidney injury, recently, high NGAL levels have been reported in hematologic malignancies. Given the mechanism underlying NGAL synthesis and secretion in neutrophilic series, it is speculated that NGAL levels are higher in bone marrow (BM) than in peripheral blood (PB). Additionally, PB NGAL levels are thought to be associated with neutrophilic parameters. We aimed to test both hypotheses in hematologic malignancies.

Methods

Paired BM and PB samples were collected from 41 patients undergoing BM examination for hematologic malignancies. NGAL levels were measured using immunoassays. Data on hematologic parameters were collected from medical records. Single and multiple regression analyses were performed to analyze the relationship.

Results

PB and BM NGAL (n = 41) levels were significantly different (163.0 ± 258.3 and 413.1 ± 616.2 ng/mL [mean ± standard deviation], respectively; P < 0.05). Simple regression analysis and multicollinearity assessment showed that BM NGAL levels, BM neutrophil%, and neutrophil count were significant predictors of PB NGAL. Two multiple regression models were developed (model 1, PB NGAL = 21.467* neutrophil count ‐ 0.785*BM neutrophil%; model 2, PB NGAL = 21.202*neutrophil count‐ 0.915*BM neutrophil% +0.10*BM NGAL). Akaike's information criterion and adjusted R² values showed that model 1 had higher predictive accuracy for PB NGAL. In both models, neutrophil count was the only significant predictor.

Conclusion

BM NGAL was significantly higher than PB NGAL in hematologic malignancy. In addition, PB NGAL could be expressed as a multiple regression model including neutrophil count and BM neutrophil%, being significantly influenced by neutrophil count.

Alternative Interventions to Prevent Oxidative Damage following Ischemia/Reperfusion

Ischemia/reperfusion (I/R) lesions are a phenomenon that occurs in multiple pathological states and results in a series of events that end in irreparable damage that severely affects the recovery and health of patients. The principal therapeutic approaches include preconditioning, postconditioning, and remote ischemic preconditioning, which when used separately do not have a great impact on patient mortality or prognosis. Oxidative stress is known to contribute to the damage caused by I/R; however, there are no pharmacological approaches to limit or prevent this. Here, we explain the relationship between I/R and the oxidative stress process and describe some pharmacological options that may target oxidative stress-states.

Angiotensin II AT1 receptor alters ACE2 activity, eNOS expression and CD44-hyaluronan interaction in rats with hypertension and myocardial fibrosis

AIM

This study tested the hypothesis that angiotensin II (Ang II) AT1 receptor is involved in development of hypertension and cardiac fibrosis via modifying ACE2 activity, eNOS expression and CD44-hyaluronan interaction.

MAIN METHODS

Male Sprague-Dawley rats were subjected to Ang II infusion (500ng/kg/min) using osmotic minipumps up to 4weeks and the AT1 receptor blocker, telmisartan was administered by gastric gavage (10mg/kg/day) during Ang II infusion.

KEY FINDINGS

Our results indicated that Ang II enhances AT1 receptor, downregulates AT2 receptor, ACE2 activity and eNOS expression, and increases CD44 expression and hyaluronidase activity, an enzyme for hyaluronan degradation. Further analyses revealed that Ang II increases blood pressure and augments vascular/interstitial fibrosis. Comparison of the Ang II group, treatment with telmisartan significantly increased ACE2 activity and eNOS expression in the intracardiac vessels and intermyocardium. These changes occurred in coincidence with decreased blood pressure. Furthermore, the locally-expressed AT1 receptor was downregulated, as evidenced by an increased ratio of the AT2 over AT1 receptor (1.4±0.4% vs. 0.4±0.1% in Ang II group, P<0.05). Along with these modulations, telmisartan inhibited membrane CD44 expression and hyaluronidase activity, decreased populations of macrophages and myofibroblasts, and reduced expression of TGFβ1 and Smads. Collagen I synthesis and tissue fibrosis were attenuated as demonstrated by the less extensive collagen-rich area.

SIGNIFICANCE

These results suggest that the AT1 receptor is involved in development of hypertension and cardiac fibrosis. Selective activating ACE2/eNOS and inhibiting CD44/HA interaction might be considered as the therapeutic targets for attenuating Ang II induced deleterious cardiovascular effects.

Anti-hypertensive treatment preserves appetite suppression while preventing cardiovascular adverse effects of tesofensine in rats

OBJECTIVE

Tesofensine is a novel triple monoamine reuptake inhibitor which is in development for the treatment of obesity. Preclinical and clinical data suggest that appetite suppression is an important mechanism by which tesofensine exerts its robust weight reducing effect. Notably, the strong hypophagic response to tesofensine treatment is demonstrated to be linked to central stimulation of noradrenergic and dopaminergic neurotransmission. The sympathomimetic mode of action of tesofensine may also associate with the elevated heart rate and blood pressure observed in clinical settings, and we therefore sought experimentally to address this issue.

DESIGN AND METHODS

The anorexigenic and cardiovascular effects of tesofensine were studied simultaneously in telemetrized conscious rats in a combined real-time food intake and cardiovascular telemetry monitoring system.

RESULTS

Acute administration of tesofensine caused a dose-dependent hypophagic effect as well as increased heart rate and blood pressure. Interestingly, combined treatment with metoprolol (b1 adrenoceptor blocker, 10-20 mg/kg, p.o.) fully prevented the cardiovascular sympathetic effects of tesofensine while leaving the robust inhibitory efficacy on food intake unaffected. Similarly, the angiotensin AT1 receptor antagonist telmisartan (1.0-3.0 mg/kg, p.o.) did not interfere with the anti-obesity effects of tesofensine, however, telmisartan only partially reversed the increase in systolic blood pressure and had no effect on the elevated heart rate induced by tesofensine.

CONCLUSION

These data suggests that tesofensine causes elevations in heart rate and blood pressure by increasing sympathetic activity, and that different adrenoceptor subtypes may be responsible for the anti-obesity and cardiovascular effects of tesofensine.

Pharmacokinetics, pharmacodynamics and toxicity of a combination of metoprolol succinate and telmisartan in Wistar albino rats: safety profiling

Metoprolol succinate (MET), a cardioselective β blocker and telmisartan (TEL), an angiotensin receptor blocker were administered orally, both individually and in combination to Wistar albino rats for evaluation of their pharmacokinetics, pharmacodynamics and repeated dose oral toxicity (28 days). Pharmacokinetic study was performed by analyzing drug concentration in plasma by a developed and validated LC-MS/MS method following oral administration of MET and TEL at 2.5 mg/kg and 2.0 mg/kg dose, respectively, both individually and in combination. Antihypertensive activity of MET and TEL in above dose and manner was evaluated on artificially induced hypertension on laboratory animals. In repeated dose oral toxicity study, MET (60, 120 and 240 mg/kg/day) and/or TEL (12, 24 and 48 mg/kg/day) were administered to animals for 28 days followed by a recovery period of 14 days. Pharmacokinetic data revealed the probable absence of any pharmacokinetic interaction when co-administered. Improved blood pressure lowering effect was observed by combination therapy. Moreover, toxic effects obtained at high dose level of each treatment groups were transient and reversible and no evidence of additive toxic effects were observed due to concomitant administration. So, this combination can primarily be stated as safe which will be confirmed after clinical interaction studies in humans.

Fabrication and evaluation of pH-modulated solid dispersion for telmisartan by spray-drying technique

The present study was undertaken to overcome the problems associated with solubility, dissolution and oral bioavailability of a poorly water-soluble ionizable drug, telmisartan (TMS). For these purposes, a solubility test was carried to select the appropriate formulation composition from various carriers and alkalizers. Solid dispersions (SDs) of TMS were prepared at different drug-to-carrier ratios by the spray-drying technique, and were characterized by dissolution and aqueous solubility studies. The optimum formulation was investigated by dissolution studies at different pH and water media and its solid state characterisations were performed by scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and X-ray diffraction (XRD) studies. In solubility and dissolution tests, all TMS-loaded pH-modulated SDs (pH(M)-SDs) exhibited marked improvement in the dissolution behavior when compared with crystalline TMS powder. The optimum formulation of pH(M)-SD consisted of TMS/PVP (polyvinylpyrrolidone) K30/Na(2)CO(3) at a weight ratio of 2/0.5/3 and showed significant improvement in the aqueous solubility and dissolution rate by approximately 40,000- and 3-fold, respectively, compared to TMS powder. Solid-state characterization revealed the changed in crystallinity of TMS into amorphous state. Furthermore, area under the drug concentration time-curve (AUC) of TMS from the pH(M)-SD increased by 13.4- and 2.1-fold, compared with TMS powder and commercial product, respectively. According to these observations, taken together with dissolution and pharmacokinetic behaviors, pH-modulated SD in the presence of an alkalizer for a poorly water-soluble ionizable drug, TMS, appeared to be efficacious for enhancing its bioavailability.

Bladder angiotensin-II receptors: characterization and alteration in bladder outlet obstruction

BACKGROUND

It is assumed that angiotensin II (AngII) is significantly implicated in the pathogenesis of urinary dysfunction because of bladder outlet obstruction (BOO).

OBJECTIVE

The current study was undertaken to characterize AngII receptors in the rat bladder in relation to BOO.

MEASUREMENTS

Bladder AngII receptors were measured by a sensitive binding assay using a specific antagonist radioligand, [(125)I]-Sar(1)-Ile(8)-AngII, in bladder outlet-obstructed rats with and without repeated oral administration of telmisartan.

RESULTS AND LIMITATIONS

[(125)I]-Sar(1)-Ile(8)-AngII bound specifically to the rat bladder homogenates with high affinity. This specific binding of [(125)I]-Sar(1)-Ile(8)-AngII was concentration-dependently displaced by the type 1 subtype (AT(1))-selective antagonists. These findings revealed the significant existence of pharmacologically relevant AngII (AT(1)) receptors in the bladder with relatively high density. Oral administration of telmisartan in rats has been shown to bind to the bladder AngII receptors. Bladder weight was about three times greater in bladder outlet-obstructed rats than in sham rats. Maximal number of binding sites (B(max)) for [(125)I]-Sar(1)-Ile(8)-AngII binding in the bladder was significantly (48%) decreased in the bladder-outlet rats when compared with sham rats, suggesting the down regulation of pharmacologically relevant AngII receptor sites. Notably, repeated oral administration of telmisartan (3mg/kg/d, 14 d) in rats completely prevented the development of a BOO-induced decrease in B(max) for bladder [(125)I]-Sar(1)-Ile(8)-AngII binding. Telmisartan treatment also effectively attenuated the increase in the bladder-wet weight caused by urinary outlet obstruction.

CONCLUSIONS

Bladder AngII may be at least partly associated with the pathogenesis of urinary dysfunction occurring subsequent to BOO through stimulation of the AT(1) receptor subtype.