USTekinumab in Fistulising Perianal Crohn's Disease (USTAP)

Inclusion Criteria: * Age ≥18 years * Adults with moderate to severe Crohn's disease for at least six months * Patients with at least one active perianal fistula track (between the anus or low rectum and the perineum or vulva) confirmed by MRI within the previous 12 weeks * Patients either naïve to anti-TNF therapy (50%) or refractory to anti-TNF therapy (50%). * If female, subject is either not of child bearing potential, defined as post-menopausal for at least1 year, surgically sterile (bilateral tubal ligation, bilateral oophorectomy or hysterectomy), or is of childbearing potential and practicing one of the following methods of birth control during the study and for 150 days after the last dose: * Condoms, sponge and foam, jellies with diaphragm or intrauterine device (IUD). IUDs may fail during azathioprine treatment. Alternative or additional contraceptive measures are advised, if azathioprine is initiated * Oral or parenteral contraceptives for 3 months prior to study drug administration * A vasectomized partner * Male subjects must agree to use an acceptable form of birth control, listed above at the start of azathioprine administration and for 90 days after last dose of azathioprine. Males should also commit to inform his partner(s) about it and to report any pregnancy to the investigator. * If female, subject is not breast-feeding throughout the study and for 150 days after last dose. * Subjects or his/her legal representative have voluntarily signed and dat…