• Written informed consent to participate in the study and the ability to comply with scheduled visits, treatment plan, laboratory tests, and other study procedures is provided.

• Aged 18 to 55 years old (inclusive).

• A weight of ≥50 kg and a body mass index between 18 and 32 kg/m2 (inclusive).

• Considered healthy by the investigator, based on a detailed medical history, full physical examination, clinical laboratory tests, 12-lead ECG, and vital signs.

• Women of childbearing potential (WOCBP) may be considered if the participant is following the contraception guidance below in 5a. The participant will be questioned at each visit where there is a potential pregnancy. Similarly, male participants must follow the contraception guidance below in 5b.

• a. Female participants meet this criterion if they are: i. Postmenopausal for at least 1 year before the first dose of study drug, including a serum FSH level of \>40 mIU/mL to be reported to confirm menopause.

• OR ii. Surgically sterile (documented hysterectomy \[by self-disclosure\] or bilateral oophorectomy ≥90 days prior to enrollment).

• OR iii. Abstinent from heterosexual intercourse as per usual lifestyle (self-reported).

• OR iv. Using effective contraceptive methods for at least 6 weeks prior to enrollment and agree to continue effective contraceptive methods throughout study participation and up to 81 weeks (t1/2 x 5) after the last dose of the study drug.

• b. Male participants meet this criterion if they agree to: i. Practice effective barrier contraception from the time of enrollment throughout study participation and up to 81 weeks (t1/2 x 5) after the last dose of the study drug.

• OR ii. Be abstinent from heterosexual intercourse as per usual lifestyle (self-reported).

• AND iii. Refrain from donating sperm during study participation and up to 81 weeks (t1/2 x 5) after the last dose of the study drug.

• Non-smoker. If participant is a social smoker (up to 10 cigarettes per week), participant is willing to abstain during confinement.

• Written informed consent to participate in the study and the ability to comply with scheduled visits, treatment plan, laboratory tests, and other study procedures is provided.

• Age ≥ 18 years.

• A weight ≥ 50 kg and a body mass index (BMI) between 18 and 32 kg/m2 (inclusive).

• Women of childbearing potential (WOCBP) and men must follow the contraception guidance as per the original protocol, ensuring no potential for pregnancy.

• A confirmed diagnosis of UC for ≥ 3 months.

• Moderate-to-severe UC, as defined by:

∙ Aggregate UC severity score ≥ 4

‣ Endoscopic severity score ≥ 2

‣ Blood in stool score ≥ 1

• Active disease beyond the rectum, with \> 15 cm of active disease from the anal verge (confirmed by endoscopy).

• Documented inadequate response, loss of response, or intolerance to ≥ 1 prior therapy from any of the following classes, confirmed by medical record OR investigator attestation OR patient-reported history (Investigator must confirm in the eCRF):

∙ Systemic corticosteroids

‣ Immunosuppressants

‣ Anti-TNF agents

‣ Anti-integrin inhibitors

‣ Anti-IL-12/23 inhibitors

‣ JAK inhibitors

‣ S1PR modulators

• If concomitantly taking 5-aminosalicylates, the participant must be on a stable dose for at least 4 weeks before baseline efficacy assessments.\*

⁃ If concomitantly taking low-dose corticosteroids (≤ 20 mg/day), the participant must be on a stable dose for at least 2 weeks before baseline efficacy assessments.\*

⁃ If concomitantly taking thiopurines, the participant must be on a stable dose for at least 8 weeks before baseline efficacy assessments.\* \*Baseline efficacy assessments include 7-Day Symptom Collection and Endoscopy.