Prophylactic Mesalamine to Prevent Colitis Following Treatment With Ipilimumab/Nivolumab (Ipi/Nivo)

Inclusion Criteria:

1. Patients must be 18 years of age or older.

2. Patients with histologically confirmed, unresectable stage III or IV malignantmelanoma.

3. Patients must be capable of providing consent to enrolment and treatment.

4. Patients with a performance status of ECOG 0-224 will be eligible for enrolment (seeappendix16.1).

5. Women of child bearing potential (WOCBP) must have a negative serum (or urine)pregnancy test at the time of screening. WOCBP is defined as any female who hasexperienced menarche and who has not undergone surgical sterilization (hysterectomyor bilateral oophorectomy or bilateral salpingectomy) and is not postmenopausal.Menopause is defined as 12 months of amenorrhea in a woman over age 45 years in theabsence of other biological or physiological causes. In addition, females under theage of 55 years must have a serum follicle stimulating hormone, (FSH) level > 40mIU/mL to confirm menopause.

6. Patients of childbearing / reproductive potential should use highly effective birthcontrol methods, as defined by the investigator, during the study treatment periodand for a period of 30 days after the last dose of study drug. A highly effectivemethod of birth control is defined as those that result in low failure rate (i.e.less than 1% per year) when used consistently and correctly.

-Note: abstinence is acceptable if this is established and preferred contraceptionfor the patient and is accepted as a local standard.

7. Female patients who are breast-feeding should discontinue nursing prior to the firstdose of study treatment and until 30 days after the last dose of study drug.

8. Male patients should agree to not donate sperm during the study and for a period ofat least 30 days after last dose of study drug

9. Absence of any condition hampering compliance with the study protocol and follow- upschedule; those conditions should be discussed with the patient before registrationin the trial.

• The following adequate organ function laboratory values must be met:

Hematological:

• Absolute neutrophil count (ANC) >1.5 x109/L

• Platelet count >100 x109/L

• Hemoglobin >9 g/dL (may have been transfused)

Renal:

o Estimated creatinine clearance ≥ 30 mL/min according to the Cockcroft-Gault formula (or local institutional standard method)

Hepatic:

• Total serum bilirubin <2x ULN

• AST and ALT <2.5x ULN (or ≤ 5 x ULN for subjects with documented metastatic diseaseto the liver)

Exclusion Criteria:

1. Clinically significant (i.e., active) cardiovascular disease: cerebral vascularaccident/stroke (< 6 months prior to enrollment), myocardial infarction (< 6 monthsprior to enrollment), unstable angina, congestive heart failure (≥ New York HeartAssociation Classification Class II), or serious cardiac arrhythmia requiringmedication.

2. Current use of immunosuppressive medication, EXCEPT for the following: a.intranasal, inhaled, topical steroids, or local steroid injection (e.g.,intra-articular injection); b. Systemic corticosteroids at physiologic doses ≤ 10mg/day of prednisone or equivalent; c. Steroids as premedication forhypersensitivity reactions (e.g., CT scan premedication).

3. Known prior severe hypersensitivity to investigational product or any component inits formulations, including known severe hypersensitivity reactions to monoclonalantibodies (CTCAE v5 Grade ≥ 3).

4. Other severe acute or chronic medical conditions or laboratory abnormalities thatmay increase the risk associated with study participation or study treatmentadministration or may interfere with the interpretation of study results and, in thejudgment of the investigator, would make the patient inappropriate for entry intothis study.