The primary objective of the study is to determine the activity of selexipag on Raynaud attack frequency in subjects with Raynaud's Phenomenon (RP) secondary to Systemic Sclerosis (SSc).

Key inclusion criteria:

• Signed informed consent prior to any study-mandated procedure.
• Male and female subjects aged 18 years and above with a history of recurrent multiple weekly RP attacks secondary to SSc.
• Women of childbearing potential must agree to use a reliable method of birth control.

Key exclusion criteria:

• Known moderate or severe hepatic impairment (i.e. Child-Pugh C).
• Known hypersensitivity to selexipag or drugs of the same class, or any of their excipients.
• Subjects who have received prostacyclin (epoprostenol) or prostacyclin analogs (i.e., treprostenol, iloprost, beraprost) within 3 months prior to the screening visit.
• Subjects who have received a Phosphodiesterase type 5 (PDE-5) inhibitor within 1 week prior to the screening visit.
• Any dose change or initiation of any of the following drugs within 1 month prior to the screening visit: Calcium channel blockers, Nitrates or nitric oxide donors, ERA's, Alpha-blockers, Antithrombotic agents, NSAIDs (occasional use allowed), Angiotensin Converting Enzyme (ACE) inhibitors, Beta-blockers, Clonidine, Systemic corticosteroids, Fluoxetine.
• Severe renal insufficiency (at randomization).
• Any circumstances or conditions, which, in the opinion of the investigator, may affect the subject's full participation in the study or compliance with the protocol