The goal of this clinical trial is to learn if dupilumab works to treat severe nephrotic syndrome in children. It will also learn about the safety of dupilumab. The main questions it aims to answer are: * Does dupilumab reduce the time to relapse of nephrotic syndrome? * What medical problems do participants have when taking dupilumab? Researchers will compare dupilumab to a placebo (a look-alike substance that contains no drug) to see if dupilumab works to treat severe nephrotic syndrome. Participants will: * Receive an injection of dupilumab or placebo (just under the skin) every 2 weeks (if ≥30kg) or every 4 weeks (if \<30kg) for 24 weeks (6 months) * Wean down their prednisolone dose after starting the injections of dupilumab or placebo * Visit the clinic once every 2 weeks for checkups and tests * Keep a nephrotic diary to record down the urine dipstick result each day, together with the dose of prednisolone taken If protein returns in participant's urine, they will have completed the study at that point. However, if the participant is found to have received the placebo, they will be offered to receive dupilumab for up to 24 weeks.
Inclusion Criteria: 1. Age between 6 years old and 18 years old at the point of recruitment with idiopathic nephrotic syndrome with disease onset between 1-18 years old 2. Steroid-dependent disease or frequently relapsing disease prior to commencement of maintenance immunosuppression 3. On oral prednisolone +/- mycophenolate or levamisole only as maintenance therapy for 6 months or more, and with inadequate disease control or steroid toxicity on therapy 4. Nephrotic relapse or partial relapse (clinical or biochemical) within the last 1 year either unprovoked or during prednisolone wean, and which responded to increase in steroids 5. In complete remission at the time of recruitment 6. Competent with, and compliant to, daily urine protein monitoring with Albustix Exclusion Criteria: 1. Pre-existing ophthalmological conditions except refractive errors, squint or mild cataract 2. Current symptoms of helminth infection or travel to endemic areas, unless helminth infection is excluded 3. eGFR (by Bedside Schwartz equation) \<60 ml/min/1.73m2 4. Received Rituximab or other B-cell depleting agents within the last 1 year 5. Biopsy proven focal segmental glomerulosclerosis 6. Known ongoing infection including HIV, Hepatitis B, Hepatitis C or tuberculosis, otherwise immunosuppressed or with frequent infections 7. Known or suspected non-compliance to medication or follow-up 8. Pregnancy or intention to become pregnant 9. Major systemic conditions, i.e. ASA Physical Status III-IV. 10. Known hypersensitivity to dupilumab or any of its excipients