Hubert Trübel

Discovery of the Soluble Guanylate Cyclase Stimulator Vericiguat (BAY 1021189) for the Treatment of Chronic Heart Failure

The first-in-class soluble guanylate cyclase (sGC) stimulator riociguat was recently introduced as a novel treatment option for pulmonary hypertension. Despite its outstanding pharmacological profile, application of riociguat in other cardiovascular indications is limited by its short half-life, necessitating a three times daily dosing regimen. In our efforts to further optimize the compound class, we have uncovered interesting structure-activity relationships and were able to decrease oxidative metabolism significantly. These studies resulting in the discovery of once daily sGC stimulator vericiguat (compound 24, BAY 1021189), currently in phase 3 trials for chronic heart failure, are now reported.

Rat models of acute lung injury: exhaled nitric oxide as a sensitive, noninvasive real-time biomarker of prognosis and efficacy of intervention.

Exhaled nitric oxide (eNO) has received increased attention in clinical settings because this technique is easy to use with instant readout. However, despite the simplicity of eNO in humans, this endpoint has not frequently been used in experimental rat models of septic (endotoxemia) or irritant acute lung injury (ALI). The focus of this study is to adapt this method to rats for studying ALI-related lung disease and whether it can serve as instant, non-invasive biomarker of ALI to study lung toxicity and pharmacological efficacy. Measurements were made in a dynamic flow of sheath air containing the exhaled breath from spontaneously breathing, conscious rats placed into a head-out volume plethysmograph. The quantity of eNO in exhaled breath was adjusted (normalized) to the physiological variables (breathing frequency, concentration of exhaled carbon dioxide) mirroring pulmonary perfusion and ventilation. eNO was examined on the instillation/inhalation exposure day and first post-exposure day in Wistar rats intratracheally instilled with lipopolysaccharide (LPS) or single inhalation exposure to chlorine or phosgene gas. eNO was also examined in a Brown Norway rat asthma model using the asthmagen toluene diisocyanate (TDI). The diagnostic sensitivity of adjusted eNO was superior to the measurements not accounting for the normalization of physiological variables. In all bioassays - whether septic, airway or alveolar irritant or allergic, the adjusted eNO was significantly increased when compared to the concurrent control. The maximum increase of the adjusted eNO occurred following exposure to the airway irritant chlorine. The specificity of adjustment was experimentally verified by decreased eNO following inhalation dosing of the non-selective nitric oxide synthase inhibitor amoniguanidine. In summary, the diagnostic sensitivity of eNO can readily be applied to spontaneously breathing, conscious rats without any intervention or anesthesia. Measurements are definitely improved by accounting for the disease-related changes in exhaled CO2 and breathing frequency. Accordingly, adjusted eNO appears to be a promising methodological improvement for utilizing eNO in inhalation toxicology and pharmacological disease models with fewer animals.

Corticosteroids found ineffective for phosgene-induced acute lung injury in rats

Various therapeutic regimes have been proposed with limited success for treatment of phosgene-induced acute lung injury (P-ALI). Corticoids were shown to be efficacious against chlorine-induced lung injury but there is still controversy whether this applies also to P-ALI. This study investigates whether different regimen of curatively administered budesonide (BUD, 10 mg/kg bw, i.p. bid; 100 mg/m(3)×30 min, nose-only inhalation), mometasone (MOM, 3 mg/kg bw, i.p. bid) and dexamethasone (DEX, 10, 30 mg/kg bw, i.p. bid), show efficacy to alleviate P-ALI. Efficacy of drugs was judged by nitric oxide (eNO) and carbon dioxide (eCO2) in exhaled air and whether these non-invasive biomarkers are suitable to assess the degree of airway injury (chlorine) relative to alveolar injury (phosgene). P-ALI related analyses included lung function (enhanced pause, Penh), morbidity, increased lung weights, and protein in bronchial alveolar lavage fluid (BALF) one day postexposure. One of the pathophysiological hallmarks of P-ALI was indicated by increased Penh lasting for approximately 20 h postexposure. Following the administration of BUD, this increase could be suppressed; however, without significant improvement in survival and lung edema (increased lung weights and BALF-protein). Collectively, protocols shown to be efficacious for chlorine (Chen et al., 2013) were ineffective and even increased adversity in the P-ALI model. This outcome warrants further study to seek for early biomarkers suitable to differentiate chlorine- and phosgene-induced acute lung injury at yet asymptomatic stage. The patterns of eNO and eCO2 observed following exposure to chlorine and phosgene may be suitable to guide the specialized clinical interventions required for each type of ALI.

Single high-dose dexamethasone and sodium salicylate failed to attenuate phosgene-induced acute lung injury in rats

Life-threatening acute lung injury potentially occurs following high-level accidental exposures to phosgene gas. This situation was mirrored in rats exposed nose-only at 900-1000 mg phosgene/m(3)min. At this exposure level, previous studies on rats demonstrated sustained reflexively induced cardiopulmonary dysfunction and evidence of vascular fluid redistribution. These findings challenge the currently applied treatment strategies to mitigate the presumed non-cardiogenic lung edema by steroidal or non-steroidal anti-inflammatory drugs. This study investigates whether high doses of curatively administered dexamethasone (DX; 100 mg/kg bw, ip) and sodium salicylate (SS; 200 mg/kg bw, ip), alone or in combination, show efficacy to mitigate the phosgene-induced lung edema. Exhaled nitric oxide (eNO), animal morbidity and mortality, and increased lung weights one day postexposure served as endpoints of lung injury and drug efficacy. When applying this dosing regimen, SS showed minimal (if any) efficacy while DX, alone or in combination with SS, substantially aggravated the emerging lung edema (lung weights) with 40% mortality. The degree of acute lung injury (ALI) was mirrored by increased eNO. Its direct relationship to ALI-severity was evidenced by decreased eNO following NO-synthetase inhibitor administration (aminoguanidine-aerosol) and associated mitigation of ALI. All non-treated phosgene-exposed as well as treated but non-phosgene-exposed rats survived. This experimental evidence suggests that high-dose corticoid treatments may aggravate the pulmonary toxicity of phosgene. Similarly, this outcome supports the supposition that non-inflammatory, cardiogenic and/or neurogenic factors play a role in this type of acute lung injury.

Phosgene- and chlorine-induced acute lung injury in rats: Comparison of cardiopulmonary function and biomarkers in exhaled breath

This study compares changes in cardiopulmonary function, selected endpoints in exhaled breath, blood, and bronchoalveolar lavage fluid (BAL) following a single, high-level 30-min nose-only exposure of rats to chlorine and phosgene gas. The time-course of lung injury was systematically examined up to 1-day post-exposure with the objective to identify early diagnostic biomarkers suitable to guide countermeasures to accidental exposures. Chlorine, due to its water solubility, penetrates the lung concentration-dependently whereas the poorly water-soluble phosgene reaches the alveolar region without any appreciable extent of airway injury. Cardiopulmonary endpoints were continually recorded by telemetry and barometric plethysmography for 20h. At several time points blood was collected to evaluate evidence of hemoconcentration, changes in hemostasis, and osteopontin. One day post-exposure, protein, osteopontin, and cytodifferentials were determined in BAL. Nitric oxide (eNO) and eCO2 were non-invasively examined in exhaled breath 5 and 24h post-exposure. Chlorine-exposed rats elaborated a reflexively-induced decreased respiratory rate and bradycardia whereas phosgene-exposed rats developed minimal changes in lung function but a similar magnitude of bradycardia. Despite similar initial changes in cardiac function, the phosgene-exposed rats showed different time-course changes of hemoconcentration and lung weights as compared to chlorine-exposed rats. eNO/eCO2 ratios were most affected in chlorine-exposed rats in the absence of any marked time-related changes. This outcome appears to demonstrate that nociceptive reflexes with changes in cardiopulmonary function resemble typical patterns of mixed airway-alveolar irritation in chlorine-exposed rats and alveolar irritation in phosgene-exposed rats. The degree and time-course of pulmonary injury was reflected best by eNO/eCO2 ratios, hemoconcentration, and protein in BAL. Increased fibrin in blood occurred only in chlorine-exposed rats 1-day post-exposure. Hence, the analysis of NO and CO2 in exhaled breath, including endpoints in blood mirroring changes in the peripheral to pulmonary fluid distribution, seem to be sensitive diagnostic endpoints readily available for early prognostic assessment of severity of injury and efficacy of any chosen countermeasure.