The present trial is designed to determine whether pre-treatment with PledOx lowers the frequency and severity of side effects from FOLFOX6 administration in patients with metastatic colorectal cancer.

The efficacy of PledOx will be assessed when added to FOLFOX6 chemotherapy as first line treatment of metastatic colorectal cancer.

This study was performed in multiple parts/phases. Part 1 was an open dose-escalation study with the doses 2, 5 and 10 micromol/kg of calmangafodipir. No study outcomes were planned for this part. In part 2a, participants randomly received either Placebo, 2 or 10 micromol/kg of calmangafodipir. In part 2b, participants randomly received either Placebo, 2 or 5 micromol/kg of calmangafodipir. The overall intent of the study was to compare the effect of antioxidant agent PledOx against placebo in one of three different doses/combinations (2 micromol/kg, 5/10 micromol/kg, 2/5/10 micromol/kg vs. placebo, in the first 8 cycles of FOLFOX6 treatment

Globally, nearly 800 000 colorectal cancers are believed to occur annually. Approximately about half of the patients with colorectal cancer develop metastatic disease. These patients are often offered chemotherapy with the FOLFOX6 regimen (FOL = FOLic acid; F = Fluorouracil (5-FU); OX = OXaliplatin) The use of FOLFOX6 is, however, hampered by a high incidence and severity of adverse reactions.

In the current trial patients will receive the antioxidant agent PledOx in one of two different doses, or placebo, in the first 8 cycles of FOLFOX6 treatment.

Inclusion Criteria:

• Advanced metastatic colorectal (stage IV) cancer verified by biopsy
• Patients may have received up to three previous treatment lines of chemotherapy, which may include fluoropyrimidine, irinotecan and targeted therapies. The last dose of antitumor drug must be given at least 4 weeks prior to inclusion and all toxicity (except alopecia and fatigue) resolved. Patients may also be chemotherapy-naïve, have received prior adjuvant treatment but no previous treatment with oxaliplatin
• CT-scan or MRI of thorax, abdomen and pelvis; within ≤4 weeks before start of chemotherapy
• Evaluable disease and one measurable site of disease according to RECIST 1.1 criteria (at least 10mm for CT-scan or MRI)
• Neurological examination with no significant pathological findings
• ≥18 years
• WHO performance status 0≤2 and Life expectancy ≥ 3 months
• Adequate haematological function, Hb ≥ 100 g/L, ANC ≥ 1.5 x 109/L, platelets ≥ 100 x 109/L
• Adequate renal and hepatic functions: creatinine clearance >50 cc/min, total bilirubin ≤ 1.5 times ULN, ASAT and ALAT ≤ 3 times ULN (ASAT and ALAT ≤ 5 times ULN in case of liver metastases)
• INR ≤1.5 times ULN, unless receiving therapeutic anticoagulation
• Negative pregnancy test for females of child-producing potential
• Written informed consent given

Exclusion Criteria:

• Tumours other than colorectal adenocarcinomas (within the previous 5 years) except for curatively treated non melanoma skin cancer or in situ carcinoma of the cervix
• Evidence of central nervous system metastases
• Unresolved bowel obstruction or sub-obstruction, uncontrolled Crohn's disease or ulcerative colitis
• History of cardiac disease with a New York Heart Association (NYHA) Class II or greater congestive heart failure, myocardial infarction or unstable angina in the past six (6) months prior to Day 1 of treatment and serious arrhythmias requiring medication for treatment
• Prolonged QTC interval >450 msec
• Known history of stroke or cerebrovascular accident in the past six (6) months
• Severe diarrhoea
• Chronic infection or uncontrolled serious illness causing immunodeficiency
• Any uncontrolled serious illness or medical condition
• Received mangafodipir at any time
• Welders, mine workers or other workers in occupations (current or past) where high manganese exposure is likely
• Pre-existing neurodegenerative disease (Parkinson's, Alzheimer's, Huntington's etc.) or neuromuscular disorder (Multiple sclerosis, Amyotrophic lateral sclerosis, Polio, hereditary neuromuscular disease)
• Major psychiatric disorder (major depression, psychosis)
• Participation in another clinical study with an investigational medicinal product within 1 month prior to inclusion.
• Blood manganese concentration values >18.3 μg/L at screening