A Study to Investigate Safety of GS-248 and Efficacy on Raynauds' Phenomenon in Systemic Sclerosis

Inclusion Criteria: * Subjects must provide signed and dated written informed consent before the conduct of any study-specific procedures. * Male and female subjects aged 18-75 years inclusive. * Systemic Sclerosis diagnosed according to European League Against Rheumatism (EULAR)/American College of Rheumatology (ACR) criteria (van den Hoogen F et al. 2013). Subjects with signs of other autoimmune diseases (e.g. Sjögren's syndrome, myositis, rheumatoid arthritis) could be included if SSc is the dominating phenotype. * Raynaud attacks typically ≥7 times per week during the last 4 weeks prior to screening despite background medication (only allowed vasodilatory therapy is calcium channel blockers or PDE-5 inhibitors). * Women of childbearing potential must be using a highly effective method of contraception to avoid pregnancy throughout the study and for 4 weeks after the last dose of Investigational Medicinal Product in such manner that the risk of pregnancy is minimised. * Women must not be pregnant or breastfeeding. * Male subjects to agree to use condom in combination with use of contraceptive methods with a failure rate of \<1% to prevent pregnancy and drug exposure of a partner, and refrain from donating sperm from the first date of dosing until 3 months after last dosing of the IMP. * Ability of subjects to participate fully in all aspects of this clinical trial. Exclusion Criteria: * Systemic Sclerosis disease duration of greater than 120 months from first non-Raynaud manifestation * Current smokers or stopped smoking \<3 months prior to Visit 1. * Dose-change or initiation of vasodilating substances (calcium blockers or PDE-5 inhibitors) within 4 weeks prior to Visit 1. * Use of iloprost or other intravenous (iv) or po prostacyclin receptor agonist within 4 weeks prior to Visit 1. * Ongoing treatment with immunosuppressive therapies (other than mycophenolate) including, but not restricted to; cyclophosphamide, azathioprine, methotrexate, or cyclosporine, or use of those medications within 4 weeks of trial entry. * Use of systemic corticosteroids during 4 weeks before screening and during the course of the study. * Concurrent serious medical condition, with special attention to cardiovascular conditions, which in the opinion of the Investigator makes the subject not suitable for this study. * Prolonged QTcF interval defined as a mean QTcF \>450 msec. * Creatinine clearance \<50 mL/min (determined by Cockcroft-Gault equation) at Screening. * Active digital ulcer (DU) within 4 weeks prior to Visit 1. * Clinically meaningful laboratory abnormalities at Screening (Visit 1), as determined and documented by the Investigator.