Efficacy and Safety Study of MAX-002 Suppository Versus Placebo and Active Medicine in Mild to Moderate Ulcerative Proctitis

Inclusion Criteria: * Participants who are 18 years old or older * Participants with total Mayo DAI score between 5 to 10 at Screening and participants with score of 2 or more for the rectal bleeding and for the findings of flexible proctosigmoidoscopy or colonoscopy sub-scores of the Mayo DAI * Participants with confirmed mild to moderate active UP not extending above rectum as evidenced by flexible proctosigmoidoscopy and histopathology assessments * Female participants of child-bearing age who have negative serum beta-human chorionic gonadotropin (β-HCG) at the time of entry into the study * Female participants of child-bearing age who use medically acceptable form of birth control * Participants who are smokers and non-smokers must not change their smoking habits or nicotine use during the DB treatment period * Participants who are literate and have legal ability to sign informed consent form Exclusion Criteria: * Participants with other digestive diseases interfering with the measurement of any sub-score of the Mayo DAI * Participants with known presence or suspicion of malignant disease of the digestive system or presence or history of neoplasms other than carcinoma in situ of the cervix or basal carcinoma of the skin * Participants with clinically significant electrocardiographic abnormalities that would compromise its participation in the study * Participants who are chronically using oral 5-aminosalicylic acid (5-ASA) at a dose greater than 4g daily, change in the oral 5-ASA dosing, or use of any form of rectal 5-ASA formulations during the 30 days prior to randomization * Participants with significant use of corticosteroids ,immunosuppressant's or biologic response modifiers that may have a therapeutic effect on ulcerative proctitis during the 45 days before the date of consent * Participants who use any rectally administered medicine during the 30 days prior to randomization * Participants who have contraindication to the use of mesalamine or suppository vehicle, analgesia, flexible proctosigmoidoscopy or colonoscopy * Participants who have blood parameters of grade 3 or higher on the common terminology criteria for adverse events (CTCAE) 5-point scale * Participants with severe renal or hepatic impairment with parameters of grade 3 or higher on the CTCAE * Participants with clinically significant urinary tract obstruction and history of idiopathic pancreatitis * Participants with presence of other known clinically significant medical and/or psychological illnesses precluding participation * Participants who participate in clinical studies other than observational studies during the 90 days before the date of the informed consent form signature * Participants who are unable or unwilling to complete the follow-up evaluations required for the study