A Phase 1/1b, Three-Part, Randomised, Placebo-Controlled, Single- and Multiple-Ascending-Dose Studyto Evaluate the Safety, Pharmacokinetics, and Activity of SZN-1326 in Healthy Volunteers and in Subjects with Moderate to Severe Ulcerative Colitis

Part 1: Single dose of SZN-1326 via intravenous injection, or subcutaneous injection. Each dose level will be tested within one cohort. Each patient will only be assigned one dose level. Dose cohorts will progress through 25mg IV, 2.5mg IV, .01mg IV, 04mg IV, .1mg IV/SC, .4mg IV/SC, 1mg IV/SC, and two additional doses whose concentration will be determined based on data from the prior cohorts. Progression between cohorts will commence based upon recommendation of the SRC based on its review of safety data after all patients in the preceding cohort have been observed for at least 14 days after dose. All dosing is performed while patients are confined in the clinical trial unit for a period prior and after dosing. Part 2: Multiple Ascending Dose - Healthy Volunteers: Multiple doses of SZN-1326 for a period of 4 weeks via weekly intravenous injection . Part 2 may commence upon recommendation of the SRC based on its review of all safety data available when patients in dose cohort .4mg have been observed for 14 days after last dose. Each patient will only be assigned one dose level. 3 dose cohorts will be tested starting at .1mg and progressing to the highest dose concentration based on data from the SAD, with route of administration also determined by data in the SAD. All dosing is performed while patients are confined in the clinical trial unit for a period prior and after dosing.