This study evaluates the effectiveness and safety of infliximab in the treatment of acute pancreatitis in adults. A third of participants will receive one single dose of infliximab via infusion, another third will receive a higher dose of infliximab via infusion and the final third of participants will receive a placebo infusion.

Acute pancreatitis (AP) is an inflammatory disorder of the pancreas causing excruciating pain, gastrointestinal dysfunction and pronounced systemic inflammatory responses with circulatory and respiratory disturbances that can lead to organ failure and death.

Tumour necrosis factor alpha (TNFα) has a major role in the pathogenesis and severity of acute pancreatitis. TNFα levels rise early and remain elevated for days in human AP, proportional to severity, presenting a suitable drug target to inhibit the amplified immune responses that further damage the pancreas and drive widespread organ dysfunction.

Infliximab is a chimeric monoclonal antibody biologic drug that blocks the actions of tumor necrosis factor alpha (TNF-α) and is normally used to treat autoimmune diseases. Infliximab has been selected as it is given via intravenous infusion, which will ensure rapid bioavailability to treat AP. This is different from most other biologics, which are given subcutaneously.

This trial will determine the efficacy of early initiation of anti-TNF treatment in AP, setting new standards for trials in AP. Using a randomised, double-blind, placebo-controlled adaptive design, with two doses of a single intravenous infusion of infliximab at 5 mg/kg or 10 mg/kg (the higher dose arm was dropped on 19th May 2026, see Study Design), the trial will determine size of any effect and safety of this treatment.

Inclusion Criteria:

• Adult patients attending Accident and Emergency (A&E) at or admitted to recruiting hospitals via a GP with a new diagnosis of AP established by two of the following three criteria: (1) typical continuous upper abdominal pain; (2) amylase and/or lipase three or more times the upper limit of normal; (3) characteristic findings on abdominal imaging (if undertaken urgently by CT or MRI)
• Patients in whom trial treatment can be started within 36 hours of admission to hospital with a new diagnosis of acute pancreatitis allowing 120 min for preparation of trial medication
• Patients from whom appropriate consent is obtained (from the patient or their legal representative).

Exclusion Criteria:

• Age <18 or >85
• Patients with a bodyweight over 200 kg
• Known previous AP within the last 30 days or chronic pancreatitis
• Multiple sclerosis, systemic vasculitis, Guillain-Barré syndrome or other demyelinating disorder
• Known epilepsy
• Moderate to severe heart failure and/or coronary disease (NYHA III/IV)
• Severe respiratory conditions including cystic fibrosis, severe asthma and severe chronic obstructive pulmonary disease (COPD)
• On home oxygen or home mechanical ventilation
• Jaundice (serum bilirubin >50 µmol/L), and/or known advanced liver disease, on waiting list for liver transplantation or considered unsuitable for transplantation
• Known cancer for which chemotherapy and/or radiotherapy ongoing/completed in last 6 months
• Known haematological malignancy
• Known end-stage cancer requiring palliative care
• Known established infection prior to or suspected infection, including COVID-19, at the time of AP onset
• Known history of tuberculosis, or household contact with those with tuberculosis or opportunistic infection
• Known history of infective hepatitis
• Rare diseases or inborn errors of metabolism that significantly increase the risk of infections, including severe combined immunodeficiency (SCID) and homozygous sickle cell disease
• Known live vaccine or infectious agent within one month of admission
• Known immunosuppressive or biologic therapy within one month of admission
• Known hypersensitivity to infliximab or to inactive components of REMICADE® or to any murine proteins
• Known pregnancy or lactation at admission
• Females of childbearing potential who do not agree to use adequate contraception up to 6 months after infliximab infusion
• Known participation in investigational medicinal product study within last three months.

To ensure negotiations with Pharma and Regulatory Authorities for further trial(s) of infliximab for this indication will not be impeded.

Once the delegated research team member performs randomisation and the staff member responsible for preparation of trial medication is provided with the allocation, that latter staff member will prepare the infusion, which will be covered by an opaque sleeve and labelled for blinding.