If you choose to participate in this study, you will visit the clinic up to 6 times over a 24-week period. You will also get a phone call from study staff at least once a week. You will be asked to report any difficulties or side effects that you experience, regardless of whether or not you feel they are related to or caused by the study drug. It is very important for you to discuss any illnesses, difficulties or side effects that you may have during the study with your study doctor. Your study doctor may remove you from the study and recommend approved or other investigational treatments.

Eligible: 1. Subject has been diagnosed with systemic sclerosis (SSc) as defined by American College of Rheumatology (ACR) criteria. 2. Males and females age greater than 18 years at time of Screening. 3. Presence of at least one active digital ulcer (meets protocol defined qualifications for active digital ulcer, Section 3.3.1.1) at Baseline. Not Eligible: 1. Has diagnosis of pulmonary arterial hypertension (PAH). 2.Body weight less than 40 kg at time of Screening, confirmed at Baseline. 3.The subject has a history of postural hypotension, unexplained syncope, a blood pressure that is less than 95 mmHg systolic or 50 mmHg diastolic at Screening or Baseline. 4.Hemoglobin concentration less than 75% of the lower limit of the normal range at time of Screening. 5.Moderate to severe hepatic impairment, i.e., Child-Pugh Class B or C, or ALT greater than 3 times the upper limit of normal. 6.Intractable diarrhea, or severe malabsorption, defined as greater than 15% unintentional loss of body weight in the last 6 months prior to Screening; any severe organ failure (e.g., lung, kidney), bleeding diathesis or platelet disorder, or any life-threatening condition. 8.Simultaneously fulfills criteria for a second connective tissue disease including systemic lupus erythematosus, rheumatoid arthritis, or inflammatory myopathy. 9.Sympathectomy of the upper limb performed within 12 months of Baseline. 10.Receipt of prostanoid treatment (epoprostenol, treprostinil sodium, or other prostacyclin analog) within the previous 3 months of Baseline for conditions including Raynaud’s phenomenon, rest pain and / or digital ulcers.

The purpose of this research study is to determine if treprostinil diethanolamine (UT-15C SR) is effective at healing digital ulcers. The study will also look at the safety of the study drug and how well subjects tolerate it.