Inclusion Criteria:

Part 1 (OLE)

• Patients who were previously enrolled in Study GA29144 and experienced any of the following:
  • Disease worsening in the Induction Phase of Study GA29144, defined as a CDAI score at Week 10 or later in the Induction Phase being greater than the patient’s baseline (Week 0) score;
  • Not eligible for the Maintenance Phase in Study GA29144;
  • Completed the Week 14 visit in Study GA29144 and could not subsequently enter the Maintenance Phase, because the sample size for the Maintenance Phase has been achieved;
  • A clinical relapse during the Maintenance Phase of Study GA29144, defined as two consecutive CDAI scores during the Maintenance Phase (may include unscheduled visits) that are  the baseline (Week 0) score and/or ≥ 100 points higher than the Week 14 score, with at least one of the two scores being ≥ 220 points.
    • CDAI score ≥ the baseline (Week 0) score
    • CDAI score ≥ 100 points higher than the Week 14 score
  • Completed the Maintenance Phase including the Week 66 or Week 74 clinic visit in Study GA29144.
  • Ability and willingness to provide written informed consent and comply with the requirements of the OLE-SM protocol.
• For women who are not postmenopausal (at least 12 months of non-therapy-induced amenorrhea) or surgically sterile (absence of ovaries and/or uterus): agreement to remain abstinent or to use highly effective method of contraception (e.g., combined oral contraceptive pill or transdermal patch, spermicide and barrier [condoms], intrauterine device, implants for contraception, injections for contraception [with prolonged release], hormonal vaginal device, sterilization, or surgical tubal ligation) during the treatment period and for at least 24 weeks after the last dose of study drug.
  • Abstinence is acceptable only if it is in line with the preferred and usual lifestyle of the patient. Periodic abstinence (e.g., calendar, ovulation, symptothermal, or postovulation methods) and withdrawal are not acceptable methods of contraception.
• For men: agreement to remain abstinent or to use a condom, as well as not donate sperm, during the treatment period and for at least 24 weeks after the last dose of study drug.
  • Abstinence is acceptable only if it is in line with the preferred and usual lifestyle of the patient. Periodic abstinence (e.g., calendar, ovulation, symptothermal, or postovulation methods)  and withdrawal are not acceptable methods of contraception.

Part 2 (SM)

• Patients who participated in Study GA29144 and are not eligible or chose not to enroll in Part 1 (OLE).
• Patients who participated in Part 1 (OLE) of this protocol.
• Ability and willingness to provide written informed consent and comply with the requirements of Part 2 (SM) of the OLE-SM protocol.
• All patients must have completed the 12-week safety follow-up in either GA29144 or GA29145, Part 1 (OLE), as applicable, prior to entering Part 2 (SM).

Exclusion Criteria:

Part 1 (OLE)

• Patients who leave Study GA29144 before Week 10.
• Patients who discontinue study drug in the Induction Phase of Study GA29144, except for those escaping between and including Weeks 10 and 14 due to disease worsening.
• Inability to comply with the study protocol, in the opinion of the investigator.
• Pregnancy or lactation.
• Patients who developed an anaphylactic/anaphylactoid or severe allergic reaction to study medication during Study GA29144.
• Patients who have an untreated or unresolved serious infection event.
• Patients who experienced a de novo or reactivated serious viral infection such as hepatitis B virus (HBV), hepatitis C virus (HCV), or HIV during Study GA29144.
• Patients who developed cytomegalovirus (CMV) colitis leading to early treatment discontinuation during Study GA29144.
• Patients who developed life-threatening infections during Study GA29144.
• Patients who developed a malignancy (with the exception of local and resected basal or squamous cell carcinoma of the skin) or who develop adenocarcinoma in situ (AIS), high-grade squamous  intraepithelial lesions (HSIL), or cervical intraepithelial neoplasia (CIN) of Grade > 1 on cervical Pap smear or who develop colonic dysplasia during Study GA29144.
• Receipt of the following prohibited medications since commencement of Study GA29144:
  • Any investigational treatment, including investigational vaccines;
  • Use of T or B cell depleting agents (e.g., rituximab, alemtuzumab, or visilizumab), with the exception of AZA and 6-MP (or equivalent);
  • Use of cyclosporine, tacrolimus, sirolimus, or mycophenolate mofetil (MMF);
  • Use of natalizumab or vedolizumab;
  • Use of TNF antagonists;
  • Use of antagonists of IL-12 ± IL-23 (e.g., ustekinumab);
  • Immunization with a live/attenuated vaccine;
  • Use of anti-adhesion molecules (e.g., anti-MAdCAM-1).
• In the opinion of the investigator, any new (since enrolling in Study GA29144), significant, uncontrolled comorbidity, such as neurological, cardiac (e.g., moderate to severe heart failure New York Heart Association [NYHA] Class III/IV), pulmonary, renal, hepatic, endocrine, or gastrointestinal (GI) disorders (excluding CD).
• Any patient who developed PML in Study GA29144.
• Any patient with neurological symptoms where suspected PML has not been ruled out.

Part 2 (SM)

• No exclusion criteria.