Combination therapy with Bosentan and Sildenafil improves Raynaud's phenomenon and fosters the recovery of microvascular involvement in systemic sclerosis

Domain reporting in systemic sclerosis-related Raynaud's phenomenon: An OMERACT scoping review

BACKGROUND

Raynaud's phenomenon (RP) is a cardinal feature of SSc and is associated with significant disease-related morbidity that impacts on quality of life. The assessment of SSc-RP is challenging. The aim of this scoping review was to evaluate the outcome domains studied and outcome measures used in clinical studies of SSc-RP.

METHODS

Embase, MEDLINE, and the Cochrane Central Register of Controlled Trials were used to identify randomized control trials (RCTs), quasi-randomized studies, case-control studies, prospective and retrospective cohort studies, case series, and cross-sectional studies of adult participants with SSc-associated RP, written in English. A minimum of 25 participants for studies of imaging modalities and 40 participants for questionnaire-based studies was required for inclusion. Basic laboratory and genetic studies were excluded. No limitations were imposed based on intervention, comparator, or study setting. Study characteristics and primary and secondary target domains in each study were recorded.

RESULTS

58 studies (24 randomized clinical trials) were included in the final analysis. The commonest domains captured were severity of attacks (n=35), frequency of attacks (n=28), and duration of attacks (n=19). Objective assessments of digital perfusion were also commonly used in studies of SSc-RP.

CONCLUSION

The outcome domains and the associated outcomes used to assess the impact of SSc-RP in research studies are broad and have varied across studies. The results of this study will inform the OMERACT Vascular Disease in Systemic Sclerosis Working Group to establish a core set of disease domains encompassing the impact of RP in SSc.

Standardised interpretation of capillaroscopy in autoimmune idiopathic inflammatory myopathies: A structured review on behalf of the EULAR study group on microcirculation in Rheumatic Diseases

OBJECTIVE

We conducted a systematic review, on behalf of the EULAR Study Group on Microcirculation in Rheumatic Diseases (EULAR SG MC/RD), to investigate the value of nailfold videocapillaroscopy (NVC) in idiopathic inflammatory myopathies (IIM).

METHODS

Three electronic databases were systematically searched to find all relevant manuscripts reporting NVC outcomes in IIM patients. Articles were assessed based on study design, population, NVC methodology and description of NVC results. To allow comparison between the articles, all NVC results were interpreted according to standardised capillaroscopic terminology, as previously consented by the EULAR SG MC/RD and the Scleroderma Clinical Trials Consortium (SCTC) Group on Capillaroscopy.

RESULTS

Of the 653 identified records; five were retained after critical appraisal on title, abstract and manuscript level. A marked difference in NVC was observed between (juvenile) dermatomyositis [(j)DM] versus polymyositis, healthy controls and systemic sclerosis patients. In addition, reduced capillary density and scleroderma pattern seem to be associated with active disease in (j)DM, while immunosuppressive treatment appears to reduce NVC abnormalities.

CONCLUSION

This is the first systematic review investigating NVC in IIM, interpreting the results according to an international consented standardised manner, as proposed by the EULAR SG MC/RD and SCTC Group on Capillaroscopy. We can conclude that NVC presents a promising asset in the diagnosis of (j)DM. Moreover, NVC could be a biomarker for organ involvement and follow-up. Large multicentre prospective standardised studies are further needed to definitely describe associations with clinical and laboratory parameters in the different IIM subtypes.

Capillaroscopy and Immunological Profile in Systemic Sclerosis

Introduction: Data on the associations between capillaroscopic changes and diagnostic systemic-sclerosis (SSc)-related antibodies are scarce. Presence of such correlation would improve current knowledge about the disease’s pathogenesis by revealing the mechanisms of microangiopathy. The microvascular pathology of SSc is a hallmark of the disease, and immunological abnormalities probably contribute to its development. Patients and methods: 19 patients with definite diagnosis of SSc were included in the current pilot study; 16 had limited and 3 had diffuse cutaneous involvement; their mean age was 51.56 ± 15.07 years. All patients exhibited symptoms of Raynaud’s phenomenon of the fingers. A “scleroderma” type capillaroscopic pattern was classified according to the staging suggested by Cutolo et al. (2000): “early”, “active” or ”late” phase. In the presence of different degrees of capillaroscopic changes in different fingers, the most-advanced microvascular pathology was chosen for classification. In cases without capillaroscopic features of microangiopathy, the findings were categorized as normal or nonspecific (dilated, tortuous capillaries, and/or hemorrhages). Indirect immunofluorescence on HEp-2 cells was performed as the gold-standard screening method for the detection of antinuclear autoantibodies (ANA), and determination of the immunofluorescent staining pattern (anti-cell pattern) was in accordance with the International Consensus on ANA Patterns. Scleroderma-associated autoantibodies in the patients’ serum were assessed using line immunoblot assay for detection of autoantibodies to 13 scleroderma-associated autoantigens: Scl-70, CENP A, CENP B, RP11/RNAP-III, RP155/RNAP-III, fibrillarin, NOR-90, Th/To, PM-Scl100, PM-Scl75, Ku, PDGFR, and Ro-52. Results: In 73.7% (n = 14) of the examined patients, “scleroderma” type capillaroscopic changes were found, and in 26.3% (n = 5), capillaroscopic features of microangiopathy were absent (nonspecific changes, n = 3; normal findings, n = 2). In SSc patients with positive anti-Scl-70 (n = 7) antibodies, significantly lower mean capillary density was observed along with a higher frequency of “active” and “late” phase capillaroscopic changes as compared to the anti-Scl-70-negative patients (p < 0.05). Anti-RNAP III−155 positive patients (n = 4) had significantly higher mean capillary density than anti-RNAP III−155 negative patients (n = 15). In three of the anti-RNAP III−155-positive cases, capillaroscopic features of microangiopathy were not detected, and in one case there was an “early” phase “scleroderma” pattern. Conclusion: In the current pilot study, the association between more advanced capillaroscopic changes and the presence of anti-Scl-70 autoantibodies was confirmed. As a novel observation, positive anti-RNAP III−155 antibodies were found in SSc patients with or without early microangiopathy. The question of associations between microvascular changes in SSc and other SSc-related autoantibodies requires further research.

Detection of microvascular changes in systemic sclerosis and other rheumatic diseases

Morphological and functional analysis of the microcirculation are objective outcome measures that are recommended for use in the presence of clinical signs of altered peripheral blood flow (such as Raynaud phenomenon), which can occur in systemic sclerosis (SSc) and other autoimmune rheumatic diseases. Several advanced non-invasive tools are available for monitoring the microcirculation, including nailfold videocapillaroscopy, which is the best-studied and most commonly used method for distinguishing and quantifying microvascular morphological alterations in SSc. Nailfold videocapillaroscopy can also be used alongside laser Doppler techniques to assist in the early diagnosis and follow-up of patients with dermatomyositis or mixed connective tissue disease. Power Doppler ultrasonography, which has been used for many years to evaluate the vascularity of synovial tissue in rheumatoid arthritis, is another promising tool for the analysis of skin and nailbed capillary perfusion in other autoimmune rheumatic diseases. Other emerging methods include raster-scanning optoacoustic mesoscopy, which offers non-invasive high-resolution 3D visualization of capillaries and has been tested in psoriatic arthritis and SSc. The principle functions and operative characteristics of several non-invasive tools for analysing microvascular changes are outlined in this Review, and the clinical roles of validated or tested imaging methods are discussed for autoimmune rheumatic diseases.

Prediction and primary prevention of major vascular complications in systemic sclerosis

OBJECTIVE

In Systemic Sclerosis (SSc), vasculopathy is the background of major vascular complications (MVCs), like digital ulcers (DUs), pulmonary arterial hypertension (PAH) and scleroderma renal crisis (SRC). We aimed to identify the predictors and to test the primary preventive effect of vasoactive/vasodilating drugs (VVD) for the development of MVCs in SSc MVCs-naïve patients.

METHODS

patients fulfilling the ACR/EULAR 2013 classification criteria for SSc without history of MVCs were eligible. Data about clinical manifestations, laboratory and instrumental assessments and treatments were retrospectively collected at baseline and latest available follow-up.

RESULTS

134 SSc patients were enrolled (mean age 56.5 years ± 14.2, females 88.1%, limited subset 61.9%, ACA positivity 60.4%). In a mean of 43 ± 19 months of follow-up 12 (9.0%) patients developed at least 1 MVC (10 DU, 2 PAH and 1 SRC). Dyspnoea and arthritis at baseline were independent predictors for MVCs development (p = 0.012, and p = 0.002 respectively). No primary preventive effect of VVD on MVCs development was found. However, sildenafil reduced the renal resistive index increase (p = 0.042) and alprostadil slowed the DLco decline (p = 0.029). Both iloprost and angiotensin-receptor blockers (ARBs) delayed MVCs development, while angiotensin converting enzyme inhibitors (ACEi) determined an earlier onset of such MCVs.

CONCLUSIONS

in SSc patients, our data confirm the role of arthritis and dyspnea as independent predictors of major vascular complications, in particular in MVCs-naïve patients. Prostanoids, sildenafil and ARBs, even in absence of a primary preventive action, might help in slowing disease progression and postponing the onset of MVCs.

Change of the microvascularization in systemic sclerosis, a matter of air

Systemic sclerosis (SSc) is a rare complex disease, characterized by microvascular damage, auto-immunity, and fibrosis. Nailfold capillary microscopy (NCM), a safe and noninvasive imaging technique, can be used to visualize specific microvascular alterations in SSc. In this review, we discuss an interesting case of a patient with changes in microvascular pattern on NCM after pulmonary transplantation. We provide an overview of microvascular alterations in systemic sclerosis and the evidence in the literature about the effect of vasoactive and immunomodulation therapy on these vascular changes. We also outline the influence of pulmonal pathology, such as interstitial lung disease and pulmonary arterial hypertension, on the capillaroscopic pattern, and finally, we discuss how NCM could possibly serve as a biomarker of treatment.

Sildenafil beyond erectile dysfunction and pulmonary arterial hypertension: Thinking about new indications

Sildenafil, approved two decades ago, is the inhibitor of phosphodiesterase 5 (PDE5). First of all, it was designated for angina pectoris, but soon it showed a wonderful efficacy in erectile dysfunction (ED) and then pulmonary arterial hypertension (PAH). Due to the distribution of phosphodiesterase (PDE) in almost all organs, maybe it effects other diseases. Hence, a great number of investigations began to understand the role of PDEi in different organs. Preliminary research on sildenafil in cell culture and animal models has yielded promising results. Soon, a greater number of animal researches and clinical trials joined them. The results disclosed sildenafil can have beneficial effects in each organ such as heart, liver, kidney, brain, and intestines. Furthermore, it has significantly improved the prognosis of organ ischemia in various animal models. Clinical trials in several diseases, such as recurrent spontaneous miscarriage, fatty liver disease, bronchopulmonary dysplasia (BPD), heart failure, and premature ejaculation (PE) brought promising results. Although some clinical trials are available on the effects of sildenafil on various diseases, further studies on humans are needed to consolidate the ultimate effects of sildenafil. The aim of this review was to describe the effects of sildenafil on each organ and explain its mechanisms of action. Further, other PDE inhibitors such as tadalafil and vardenafil have been briefly discussed in parts of this review.

Digital Ulcers in Systemic Sclerosis

Digital ulcers (DU) are one of the most common complication of Systemic Sclerosis (SSc)-related vasculopathy and represent an important burden for the patients as well as for the society. Still today there is no agreement on the definition, classification and cathegorization of DU even if they are of pivotal importance in clinical practice, for treatment choice and prognostic outcomes, as well as for clinical trials. DU management requires a dedicated multidisciplinary team, that must remain ever vigilant for the development of infective complications and gangrene throughout their disease course, as well as patient education that is crucial to obtain the best compliance to assure the success of the treatment. Currently several drugs are available for DU treatment but in the future, more investigations will be needed to ameliorate the approach and the systemic and local therapies.

Progression of nailfold capillaroscopic patterns and correlation with organ involvement in systemic sclerosis: a 12 year study

OBJECTIVE

The aim of this observational study was to investigate the evolution of scleroderma microangiopathy throughout different nailfold videocapillaroscopy (NVC) patterns ('early', 'active', 'late') as well as the prevalence of organ involvement in SSc patients during a 12-year follow-up.

METHODS

Thirty-four SSc patients showing at baseline (first capillaroscopic analysis) the 'early' NVC pattern of microangiopathy were enrolled and followed for 12 years (s.d. 2). Complete NVC analysis and clinical and serological findings were collected. Patients were in a standard therapeutic care setting. Statistical analysis was carried out by non-parametric tests.

RESULTS

After a 12-year follow-up, the 'early' NVC pattern changed from baseline in 76% of the patients. The NVC pattern was found to be 'active' in 9 patients (26%), 'late' in 13 (38%) and characterized by non-specific capillary abnormalities in 4 (12%). In the subgroup whose microangiopathy progressed from the 'early' to the 'late' NVC pattern, the median time of progression from the 'early' to the 'active' pattern was significantly shorter (11 months) when compared with patients who progressed from the 'early' to the 'active' NVC pattern (55 months) (P = 0.002). The median time of progression between NVC patterns was significantly shorter in SSc patients showing either a nucleolar ANA pattern or Scl70 autoantibodies (P = 0.048). Organ involvement was progressively greater in SSc patients with 'early', 'active' and 'late' NVC patterns, respectively.

CONCLUSIONS

This longitudinal study confirms over a 12-year follow-up the evolution of specific NVC patterns associated with the progressive severity of organ involvement in SSc patients in a standard clinical care setting.

Monitoring the microcirculation in the diagnosis and follow-up of systemic sclerosis patients: Focus on pulmonary and peripheral vascular manifestations

Systemic sclerosis (SSc) is a connective tissue disease, characterized by vascular damage and progressive fibrosis, affecting the skin and internal organs. The vascular changes include functional and structural abnormalities in the microcirculation, which play a central role not only in diagnosis but also in the prognosis and follow-up of systemic sclerosis patients. Nailfold videocapillaroscopy (NVC) is a safe, validated, noninvasive, inexpensive, reliable, and reproducible method that allows for the evaluation of structural changes in scleroderma microangiopathy. However, capillary blood flow/perfusion cannot be measured by NVC under standard conditions and, consequently, must rely on various laser techniques and thermography for the assessment and quantification of cutaneous blood perfusion. Other emerging technologies, such as optical Doppler tomography and spectroscopy, may be used to evaluate the skin flow. This review updates current knowledge on the use of microvascular evaluation techniques in SSc, including complications such as digital ulcers and pulmonary arterial hypertension.

Combination therapy with bosentan and sildenafil for refractory digital ulcers and Raynaud's phenomenon in a 30-year-old woman with systemic sclerosis: Case report and literature review

Background

Systemic sclerosis is a rare autoimmune disease characterized by skin and organ fibrosis, and vasculopathy. Raynaud's phenomenon is almost universally present in systemic sclerosis and can be the most debilitating symptom. Raynaud's phenomenon may lead to the development of digital ulcers, potentially complicated by infection, tissue necrosis, and auto-amputation. Recommended treatments have variable efficacy.

Methods

We report the case of a 30-year-old woman with diffuse systemic sclerosis suffering from severe Raynaud's phenomenon and digital ulcers with digital tissue necrosis who was treated with combination therapy of an endothelin receptor antagonist and phosphodiesterase 5 inhibitor. In addition, we reviewed the literature on the topic.

Results

Previous therapy with calcium-channel blockers, intravenous iloprost, and bosentan had all failed to control symptoms. We added sildenafil in combination with bosentan and observed a rapid and sustained treatment effect. Raynaud's phenomenon severity, number of attacks, and attack duration decreased within 2 weeks of initiating treatment. Furthermore, this resulted in the healing of established digital ulcers.

Conclusion

Our case report suggests that combination therapy may be a feasible treatment for the most severely affected and refractory patients. In our literature review, we found one retrospective study and three additional cases with similarly encouraging results.

Inhomogeneity of capillaroscopic findings in systemic sclerosis

BACKGROUND

Despite the great interest in capillaroscopy in systemic sclerosis (SSc), research on the possible combinations of different microvascular phenomena at different fingers in SSc patients have not been performed until now.

OBJECTIVE

To assess the diversity of capillaroscopic findings in SSc.

METHODS

The study includes analysis of the capillaroscopic findings in 40 SSc patients who were divided into the following categories: "scleroderma", type pattern - "early", "active", "late" phase, normal and/or nonspecific findings. The data were analyzed using descriptive statistics and t test.

RESULTS

In 77% of the patients, inhomogeneity of the capillaroscopic findings of the fingers was detected. The most frequent combinations of capillaroscopic patterns were "early + active" (n = 7), "active + late" phase (n = 7), "active" phase + normal and/or nonspecific findings (n = 6), "early + active" phase + normal and/or nonspecific findings (n = 4). Concomitant presence of normal and/or nonspecific findings and "late" phase was detected in only 3 cases.

CONCLUSION

Inhomogeneity of the capillaroscopic findings in SSc is a frequent phenomenon. The results indicate that combinations of "scleroderma" type capillaroscopic findings from different phases could be observed as well as concomitant appearance of pathological and normal/or nonspecific findings of different digits. This phenomenon could be a result of the complex action of different factors eg, disease duration, severity of Raynaud's phenomenon, presence of digital ulcers, local action of different angiogenic and angiostatic factors, gradual transition from one phase to another due to the extensive capillary area, therapeutic interventions.

Nailfold capillaroscopy in systemic sclerosis - state of the art: The evolving knowledge about capillaroscopic abnormalities in systemic sclerosis

Capillaroscopy is a unique method for morphological evaluation of the nailfold capillaries that plays a crucial role for early diagnosis of systemic sclerosis. The first description of the pathological capillaroscopic changes in systemic sclerosis was made by Brown and O'Leary in 1925. Several decades later they have been validated and accepted as a diagnostic criterion in the current 2013 EULAR/ACR classification criteria. This article summarizes the evolving knowledge about the use of nailfold capillaroscopy in systemic sclerosis. Initially, Maricq et al. suggested two major categories of capillaroscopic findings in systemic sclerosis - an 'active'and 'slow' capillaroscopic pattern. Their description and terminology suggested a correlation between capillaroscopic changes and disease activity and progression. In the later classification of Cutolo et al., three phases were defined, i.e. 'early', 'active' and 'late' that reflect the time-related evolution of the capillaroscopic changes suggesting their association with disease duration. Current knowledge about the microvascular changes in systemic sclerosis supports both associations with disease activity and disease duration. The general opinion about the association of capillaroscopic findings with clinical involvement and disease activity in systemic sclerosis is not uniform. This is supposedly because the phase changes of systemic sclerosis-related microangiopathy are almost a universal feature in scleroderma and are not specific for a certain type of an accompaning clinical manifestation. Thus, the speed of progression of microvascular alterations might be a decisive criterion, and in cases of rapid dynamics of capillaroscopic findings, it could be considered as an indicator of disease activity. Interestingly, vascular 'recovery' has been observed after treatment with immunosuppressive drugs, haematopoietic stem cell transplantation, and the endothelin receptor antagonist - bosentan. The evolving knowledge about nailfold capillaroscopy in systemic sclerosis will further spread its application from a mainly diagnostic tool to an established, reliable method for evaluation of disease activity, prognosis and therapeutic response.

Expression of the oxygen-sensitive transcription factor subunit HIF-1α in patients suffering from secondary Raynaud syndrome

Anti-ischemic therapy remains a challenge due to the complexity of hypoxia response pathways. Hypoxia-inducible factor (HIF)-1 is a heterodimer transcription factor consisting of 2 subunits, HIF-1α and HIF-1β. Hypoxia-dependent activation of HIF-1α regulates cellular O₂ homeostasis. Raynaud syndrome (RS), as a comorbidity of the autoimmune disease systemic sclerosis (SS), is characterized by vasospasms that limit blood flow to the limbs, resulting in hypoxia. A single-center randomized study was conducted to compare prostaglandin E1 (PgE1) therapy with a treatment combining PgE1 and an endothelin-1 blocker, bosentan. A total of 30 patients suffering from SS with RS were enrolled. We examined the regulation of HIF-1α, its target heme oxygenase-1 (HMOX-1), and the serum levels of the HIF-1α protein in a subset of patients as well as in ten healthy individuals. The expression of HIF-1α and HMOX-1 in monocytes was measured using absolute plasmid-based quantitative real-time PCR, whereas serum HIF-1α levels were measured with ELISA. Samples were taken at the time of randomization and after 24 weeks. We found that HIF-1α and HMOX-1 mRNA expression in monocytes and serum HIF-1α protein levels were significantly higher in the SS/RS patients compared to the healthy control group. Single-drug therapy significantly increased HIF-1α and HMOX-1 mRNA expression in monocytes and serum HIF-1α protein levels in the SS/RS patients compared to those at the time of randomization, whereas combining PgE1 with an endothelin-1 blocker prevented the further increases in HIF-1α and HMOX-1 expression. We propose HIF-1α and HMOX-1 as novel markers for anti-ischemic therapy in RS.

Vascular Leaking, a Pivotal and Early Pathogenetic Event in Systemic Sclerosis: Should the Door Be Closed?

The early phase of systemic sclerosis (SSc) presents edema as one of the main features: this is clinically evident in the digital swelling (puffy fingers) as well as in the edematous skin infiltration of the early active diffuse subset. Other organs could be affected by this same disease process, such as the lung (with the appearance of ground glass opacities) and the heart (with edematous changes on cardiac magnetic resonance imaging). The genesis of tissue edema is tightly linked to pathological changes in the endothelium: various reports demonstrated the effect of transforming growth factor β, vascular endothelial growth factor and hypoxia-reperfusion damage with reactive oxygen species generation in altering vascular permeability and extravasation, in particular in SSc. This condition has an alteration in the glycocalyx thickness, reducing the protection of the vessel wall and causing non-fibrotic interstitial edema, a marker of vascular leak. Moreover, changes in the junctional adhesion molecule family and other adhesion molecules, such as ICAM and VCAM, are associated with an increased myeloid cells' extravasation in the skin and increased myofibroblasts transformation with further vascular leak and cellular migration. This mini-review examines current knowledge on determinants of vascular leak in SSc, shedding light on the role of vascular protection. This could enhance further studies in the light of drug development for early treatment, suggesting that the control of vascular leakage should be considered in the same way that vasodilation and inflammation reduction, as potential therapeutic targets.

Phosphodiesterase-5 inhibition potentiates cerebrovascular reactivity in chronic traumatic brain injury

BACKGROUND

Traumatic cerebrovascular injury (TCVI), a common consequence of traumatic brain injury (TBI), presents an attractive therapeutic target. Because phosphodiesterase-5 (PDE5) inhibitors potentiate the action of nitric oxide (NO) produced by endothelial cells, they are candidate therapies for TCVI. This study aims to: (1) measure cerebral blood flow (CBF), cerebrovascular reactivity (CVR), and change in CVR after a single dose of sildenafil (ΔCVR) in chronic TBI compared to uninjured controls; (2) examine the safety and tolerability of 8-week sildenafil administration in chronic symptomatic moderate/severe TBI patients; and as an exploratory aim, (3) assess the effect of an 8-week course of sildenafil on chronic TBI symptoms.

METHODS

Forty-six subjects (31 chronic TBI, 15 matched healthy volunteers) were enrolled. Baseline CBF and CVR before and after administration of sildenafil were measured. Symptomatic TBI subjects then completed an 8-week double-blind, placebo-controlled, crossover trial of sildenafil. A neuropsychological battery and neurobehavioral symptom questionnaires were administered at each study visit.

RESULTS

After a single dose of sildenafil, TBI subjects showed a significant increase in global CVR compared to healthy controls (P < 0.001, d = 0.9). Post-sildenafil CVR maps showed near-normalization of CVR in many regions where baseline CVR was low, predominantly within areas without structural abnormalities. Sildenafil was well tolerated. Clinical Global Impression (CGI) scale showed a trend toward clinical improvement while on sildenafil treatment.

FINDINGS

Single-dose sildenafil improves regional CVR deficits in chronic TBI patients. CVR and ΔCVR are potential predictive and pharmacodynamic biomarkers of PDE5 inhibitor therapy for TCVI. Sildenafil is a potential therapy for TCVI.

Points to consider for skin ulcers in systemic sclerosis

This article discusses points to consider when undertaking a clinical trial to test therapy for skin ulcers in SSc. A validated definition of skin ulcers should be used if available. Defining a uniform SSc patient population, including consideration of disease duration, history of digital ulcers and capillaroscopic patterns, is important. Excluding confounding factors such as infection, calcinosis and trauma should be strongly considered, or at least accounted for, in defining patients. Outcome measures such as time to healing, prevention of new ulcers, function, pain and objective measures such as US, laser Doppler and thermography can be considered as outcome measures, although their validation has not yet been achieved and efforts may be needed to validate them before use. Likewise, biomarkers should be considered or consideration should be given to storing serum, plasma or cells for possible future analysis. A pre-planned analysis is important and should include consideration of missing data.

Physicochemical Properties of Bosentan and Selected PDE-5 Inhibitors in the Design of Drugs for Rare Diseases

The study provides the physicochemical characteristic of bosentan (BOS) in comparison to tadalafil (TA) and sildenafil citrate (SIL). Despite some reports dealing with thermal characteristic of SIL and TA, physicochemical properties of BOS have not been investigated so far. Recent clinical reports have indicated that the combination of bosentan and PDE-5 inhibitor can improve the effectiveness of pharmacotherapy of pulmonary arterial hypertension (PAH). However, in order to design personalized medicines for therapy of chronic rare diseases, detailed information on the thermal behaviour and solubility of each drug is indispensable. Thus, XRD, DSC and TGA-QMS analyses were applied to compare the properties of the drugs, their thermal stability as well as to identify the products of thermal degradation. The dehydration of BOS started at 70°C and was followed by the chemical degradation with the onset at 290°C. The highest thermal stability was stated for TA, which decomposed at ca. 320°C, whereas the lowest onset of the thermal decomposition process was stated for SIL, i.e. 190°C. The products of the drug decomposition were identified. FT-FIR was applied to study intra- and intermolecular interactions between the drug molecules. FT-MIR and Raman spectroscopy were used to examine the chemical structure of the drugs. Chemoinformatic tools were used to predict the polar surface area, pKa, or logP of the drugs. Their results were in line with solubility and dissolution studies.