Bosentan in Digital Ulcers

Inclusion Criteria:

1. Patients with SSc according to the classification criteria of the American College of
Rheumatology

2. SSc patients with at least one DU at baseline qualifying as a CU (see definition
section 3.2.2)

3. CU occurred < 3 months and > 1 week prior to randomization. The subset of patients
with SSc felt to be at high risk for DUs will be identified in the screening period
but will not be eligible for enrollment until a CU has developed

4. Male or female patients >/= 18 years of age

5. Women of childbearing potential must have a negative pre-treatment pregnancy test and
use a reliable method of contraception during study treatment and for at least 3
months after study treatment termination

6. Women not of childbearing potential are defined as postmenopausal (i.e., amenorrhea
for at least 1 year), or surgically or naturally sterile

7. Signed informed consent.

Exclusion Criteria:

1. DUs due to condition other than SSc

2. Severe PAH (WHO class III and IV)

3. Systolic blood pressure < 85 mmHg

4. Hemoglobin concentration < 75% of the lower limit of the normal range

5. AST and/or ALT values greater than 3 times the upper limit of normal

6. Moderate to severe hepatic impairment, i.e., Child-Pugh Class B or C

7. Severe malabsorption or any severe organ failure (e.g., lung, kidney) or any
life-threatening condition

8. Pregnancy or breast-feeding

9. Previous treatment with bosentan

10. Treatment with any of the following: glibenclamide (glyburide), fluconazole,
cyclosporine A, tacrolimus and any other calcineurin inhibitor 1 week prior to
randomization

11. Local injection of botulinum toxin in an affected finger 1 month prior to
randomization

12. Treatment with parenteral prostanoids (prostaglandin E, epoprostenol, treprostinil
sodium or other prostacyclin analogs) 3 months prior to randomization

13. Treatment with inhaled or oral prostanoids one month prior to randomization

14. Systemic antibiotics to treat infection of DUs 2 weeks prior to randomization

15. Treatment with phosphodiesterase inhibitors such as sildenafil, except for
intermittent treatment of male erectile dysfunction

16. Body weight < 40 kg

17. Patient with conditions that prevent compliance with the protocol or adhering to
therapy

18. Patient who received an investigational product within 1 month preceding screening

19. Known hypersensitivity to bosentan or any of the excipients.