Treatment naïve patients with SSc-APAH will be included in the investigator initiated trial (IIT) to assess efficacy and safety of ambrisentan. As patients life-expectancy after diagnosis of untreated patients is only one year we put forward a screening to identify borderline PAH patients and treat them before PH manifests. Therapy with ambrisentan reached a significant improvement in SSc-IPAH patients (Galiè et al. 2008). In PAH mPAP improved about 15% due to ambrisentan (Klinger et al. 2011).~Thus, especially patients with SSc-APAH have a high need for an early diagnosis and therapy. It is important to determine factors predictive of incident SSc-APAH and PH as well as the event rate of PAH and PH occurrence. Early identification and intervention with specific modern therapies as with ambrisentan may improve hemodynamic, symptoms, exercise capacity, quality of life and outcomes in this patient population, in particular in SSc-patients of borderline-PAH. It is considered reasonable that the development of manifest APAH might be preventable in this defined population with SSc and early pulmonary vascular changes. A reliable trial testing this latter hypothesis cannot be performed without critical evidence which defines the response to medical PAH-targeted therapy in borderline-PAH and the associated disease progression of manifest PAH.~Due to the positive results in the treatment of patients with SSc-APAH, the initiation of this proof-of-concept study is justified.~Previously identified patients with borderline PAH indicated by borderline mPAP values will be included in this single centre randomized, controlled, double-blind, parallel group, proof-of-concept (PoC) phase IIa IIT. If assessments necessary for screening have already been made under the screening for PH in Systemic sclerosis trial (non-drug trial, Ethics committee of Heidelberg # S360/2009), these examinations may be used for screening for this trial, as long as they have been performed within the given time frame of the screening period.~On their first visit the patients' medical history will be obtained and physical examination will be conducted. Moreover, an electrocardiogram (ECG), laboratory testing (NT-proBNP, uric acid and other laboratory tests), echocardiography at rest and during exercise and right heart catheterization will be carried out. If patients fulfill the inclusion criteria and still suffer from borderline mPAP values they will be invited to join the study. Patients will be asked to sign the informed consent form (ICF) before the initial screening will be conducted. Randomization will be performed after a maximum of 28 days and medication or placebo will be provided. If patients have been identified within the last 6 months before baseline by right heart catheterization, the measurements are considered valid for the baseline visit to spare patients a repetition of this invasive procedure. Non-invasive measurements that are out of the time-frame have to be repeated for the study. An 1:1 oral ambrisentan: oral Placebo randomization will be performed.~Patients will be randomized into either:~A treatment arm with ambrisentan treatment (19 patients)~A placebo arm (19 patients will receive placebo). Safety and tolerability will be controlled at each study visit until the end of study (day 180 ± 2 weeks). If necessary, the dose will be adapted. As to common practice of the clinic, the patient will adapt the dose according to tolerability and after consultation (by phone or personally) with one of the investigators.
Trial Design Patients with borderline PAH indicated by borderline mPAP values will be included in this single centre study. This clinical investigation is performed as a Proof-of-Concept (PoC) investigator initiated trial (IIT) using a prospective, randomized, double-blind, parallel group, placebo-controlled, phase IIA clinical study design. On their first visit their medical history will be obtained and physical examination will be conducted. Moreover, an electrocardiogram (ECG), laboratory testing (NT-proBNP, uric acid and other laboratory tests), echocardiography at rest and right heart catheterization will be carried out. If patients have been identified within the last 6 months before screening investigations by right heart catheterization, the measurements are considered valid as baseline investigations and will not be repeated. If patients fulfill the inclusion criteria and still suffer from borderline mPAP values they will be invited to join the study. The clinical investigations will begin within 28 days. The prospective study will comprise a 6 months study period (180 ±2 weeks) plus the screening phase up to 28 days and a follow-up phase of 30 ±7 days.