Hubert Truebel

Anticipated classes of new medications and molecular targets for pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) remains a life-limiting condition with a major impact on the ability to lead a normal life. Although existing therapies may improve the outlook in some patients there remains a major unmet need to develop more effective therapies in this condition. There have been significant advances in our understanding of the genetic, cell and molecular basis of PAH over the last few years. This research has identified important new targets that could be explored as potential therapies for PAH. In this review we discuss whether further exploitation of vasoactive agents could bring additional benefits over existing approaches. Approaches to enhance smooth muscle cell apotosis and the potential of receptor tyrosine kinase inhibition are summarised. We evaluate the role of inflammation, epigenetic changes and altered glycolytic metabolism as potential targets for therapy, and whether inherited genetic mutations in PAH have revealed druggable targets. The potential of cell based therapies and gene therapy are also discussed. Potential candidate pathways that could be explored in the context of experimental medicine are identified.

Novel Insights Into Phosgene-Induced Acute Lung Injury in Rats: Role of Dysregulated Cardiopulmonary Reflexes and Nitric Oxide in Lung Edema Pathogenesis

Phosgene gas is a lower respiratory tract irritant. As such, it stimulates nociceptive vagal C-fiber-related reflexes in a dose-rate and concentration × exposure duration (C × t)-dependent manner. In rats, this reflex is characterized by extended apnea time periods, bradycardia, and hypothermia. Although inhalation exposures at nonlethal C × t products show rapid reversibility of reflexively induced changes in respiratory patterns, lethal C × t products seem to cause prolonged stimulation after discontinued exposure to phosgene. This observation has been taken as indirect evidence that phosgene-induced lethal lung edema is likely to be associated with a dysfunctional neurogenic control of cardiopulmonary and microvascular physiology. In order to verify this hypothesis, data from respiratory function measurements during and after the inhalation exposure to phosgene gas were compared with time-course measurements of cardiac function over 20 h post-phosgene exposure. These data were complemented by time-course analyses of nitric oxide (NO(e)) and carbon dioxide in exhaled breath, including time-dependent changes of extravasated protein in bronchoalveolar lavage fluid and hemoglobin in blood. The nitric oxidase synthetase inhibitors L-NAME and L-NIL were used to further elucidate the role of NO(e) in this type of acute lung injury and whether its analysis can serve as an early biomarker of pulmonary injury. Collectively, the sequence and time course of pathological events in phosgene-induced lung edema appear to suggest that overstimulated, continued sensorimotor vagal reflexes affect cardiopulmonary hemodynamics. A continued parasympathetic tone appears to be involved in this etiopathology.

Effects of Different Pulmonary Vasodilators on Arterial Saturation in a Model of Pulmonary Hypertension

Background Approved therapies for pulmonary arterial hypertension can induce oxygen desaturation when administered to patients with secondary forms of pulmonary hypertension (PH), probably due to an increase in ventilation/perfusion mismatch. Thus, so far these treatments have largely failed in secondary forms of PH. Methods We established an animal model of heterogeneous lung ventilation to evaluate the desaturation potential of mechanistically distinct vasoactive drugs launched or currently in clinical development for the treatment of PH. Single-lung ventilation was induced in five groups (N = 6) of anesthetized minipigs (7 weeks, 4 to 5 kg BW), and their hemodynamic parameters were monitored before and after intravenous injection of control (vehicle only), endothelin antagonist (bosentan; 0.3, 1, 3, 10 mg/kg), phosphodiesterase type 5 inhibitor (sildenafil; 3, 10, 30, 100 µg/kg), and soluble guanylate cyclase stimulators (BAY 41–8543 and riociguat; 1, 3, 10, 30 µg/kg). Cumulative doses were administered before successive unilateral ventilation cycles. The doses were chosen to achieve equal effect on blood pressure by the different pharmacologic principles. Results Single-lung ventilation resulted in transient increases in mean pulmonary artery pressure (mPAP) and desaturation. In contrast to control, all drugs dose-dependently decreased hypoxic mPAP (a positive treatment effect) and increased area under the arterial hemoglobin saturation curve (unwanted desaturation effect). Riociguat and bosentan reduced hypoxic mPAP to the greatest extent, while the soluble guanylate cyclase stimulators riociguat and BAY 41–8543 lowered arterial oxygen saturation of hemoglobin the least. Conclusions Future investigations will be required to confirm these findings in clinical settings.

Analysis of V/Q-matching—a safety “biomarker” in pulmonary drug development?

Ventilation (V′)/perfusion (Q′) mismatch (VQM) is the single most important reason for gas-exchange abnormalities in pulmonary diseases. Pharmacological approaches can further aggravated VQM and its assessment is important to avoid hypoxemia. A theoretical framework for VQM, its relevance in clinical trials, and a stepwise evaluation approach is outlined. This assessment should entail stratification of patients- and mechanisms-at-risk for VQM. Also, its boundary conditions (e.g. cardiac output, perfusion pressure, hemoglobin concentration, changes in ventilation) need to be taken into consideration. Ultimately, VQM assessment requires invasive approaches. VQM evaluation is an important safety “biomarker” to avoid negative study outcome due to gas-exchange abnormalities.

Effect of Diet on Serum Creatinine in Healthy Subjects During a Phase I Study

Creatinine is widely used as an indirect marker of renal function. However, interfering factors such as diet, exercise and problems with the assay can generate false results and misinterpretation of real kidney function. In this article, we report the dietary effects on serum creatinine during a phase I single dose escalation study and discuss the reasons why serum creatinine should be measured under fasting conditions.

How soon will digital endpoints become a cornerstone for future drug development

Digital technologies are transforming healthcare and will provide the basis for more patient-centric innovation in the pharmaceutical industry. Digital endpoints in clinical studies have the potential to drive innovation and reduce costly late-stage failures. This is also currently under consideration by regulatory agencies, such as the US Food and Drug Administration (FDA). The academic-industrial collaboration MOBILISED-D aims to implement and validate real-world walking speed (RWS) as a digital endpoint accepted by regulatory authorities as a first of its class. Previous work has shown that loss of mobility driven by chronic illness and frailty in older patients can be a relevant readout or effect of different diseases and various organ systems.