A Study to Evaluate the Safety of PRV-300 in Adult Subjects With Moderately to Severely Active Ulcerative Colitis

Inclusion Criteria: 1. Subject must be a man or woman aged 18-75 years, inclusive. 2. Subject has a clinical diagnosis of UC at least 3 months before screening. 3. Subject has moderately to severely active UC, defined as a Mayo score of 6 to 12, inclusive, at screening. 4. Subject has a Mayo endoscopic subscore of ≥2 based on central read of the video sigmoidoscopy at screening. 5. Subject must be willing and able to adhere to the prohibitions and restrictions specified in this protocol. Exclusion Criteria: 1. Subject has severe extensive colitis as evidenced by any of the following: 1. Current hospitalization for the treatment of UC. 2. Investigator judgment that the subject is likely to require a colectomy within 12 weeks of baseline. 3. Temperature ≥37.8 ºC (oral or tympanic) and a heart rate \>90 bpm. 2. Subject has UC limited to \<15 cm of the colon. 3. Subject has a diagnosis of CD or the presence or history of fistula or indeterminate colitis. 4. Presence of a gastrostomy, jejunostomy, ileostomy or colostomy. 5. Subject has had or is expected to have surgery for active gastrointestinal bleeding, peritonitis, intestinal obstruction, or intra-abdominal or pancreatic abscess requiring surgical drainage, or other conditions that may confound study evaluations from 2 months before screening through the end of this study. 6. Presence of symptomatic colonic or small bowel obstruction 7. History of colonic resection 8. History of colonic mucosal high-grade dysplasia 9. Subject has chronic or recurrent infectious disease 10. Subject has positive serology to human immunodeficiency virus (HIV) 1 or 2, hepatitis B virus (HBV) or hepatitis C virus (HCV) at screening. 11. Subject has any known malignancy or has a history of malignancy (with the exception of basal cell carcinoma; squamous cell carcinoma in situ of the skin; or cervical carcinoma in situ that has been treated with no evidence of recurrence; or squamous cell carcinoma of the skin that has been treated with no evidence of recurrence within 5 years before screening). 12. Subject has ever received PRV-300 (or CNTO 3157) or has known allergies, hypersensitivity, or intolerance to PRV-300 or its excipients; or known or suspected intolerance or hypersensitivity to any biologic medication or known allergies or clinically significant reactions to murine, chimeric, or human proteins, to monoclonal antibodies or antibody fragments; or a history of severe allergic reactions, angioedema, or anaphylaxis that might suggest risk for a reaction to a biologic agent. 13. Subject has any condition for which, in the opinion of the Investigator, participation would not be in the best interest of the subject (eg, compromise the well-being) or that could prevent, limit, or confound the protocol-specified assessments.