Trial design and participants
In this single centre randomised controlled trial patients with biopsy proven primary membranous nephropathy were recruited to receive tacrolimus in combination with mycophenolate mofetil or tacrolimus alone. Inclusion criteria were: patients 18–80 years old; idiopathic membranous nephropathy on renal biopsy and with no evidence of an underlying cause; proteinuria defined by urinary protein: creatinine ratio (uPCR) > 100 mg/ mmol with hypoalbuminaemia defined by serum albumin < 35 g/l or uPCR > 300 mg/ mmol with normal serum albumin, despite 3 months treatment with maximum tolerated dose of angiotensin enzyme inhibitors (ACEI) or angiotensin II receptor blockers (ARB).
We excluded patients with membranous nephropathy secondary to other causes: positivity for Hepatitis B, C or HIV; malignancy; untreated infection. We also excluded pregnant or breastfeeding females and those planning a pregnancy or using unreliable contraception.
All patients were screened for malignancy with CT scan of the chest, abdomen and pelvis.
Eligible patients were randomly assigned to receive either tacrolimus (TAC group) or tacrolimus in combination with mycophenolate mofetil (TAC/MMF group). All patients remained on supportive therapy including ACEI and ARB, diuretics, statins and anticoagulation. Those assigned to the TAC group received an initial dose of 2 mg twice daily titrated to achieve whole blood levels of 5–12 ng/ml. Those assigned to the TAC/MMF group also received MMF 500 mg twice daily titrated to achieve blood mycophenolic acid (MPA) levels of 1.5–3.0 mg/L.
Patients were initially treated for 1 year. Remission of proteinuria was defined as complete (CR) when uPCR was less than 30 mg/mmol and partial (PR) if uPCR decreased by more than 50% but remained above 30 mg/mmol and less than 300 mg/mmol. Patients not obtaining complete or partial remission within 12 months were withdrawn from the trial. Once patients were in remission for 12 months the MMF was stopped in the TAC/MMF group and tacrolimus gradually withdrawn over 6 months in both groups. Maximum duration of therapy prior to treatment withdrawal was 24 months.
Patients were seen weekly until stable and established on adequate levels of immunosuppressive agents, and then monthly until remission achieved. Blood and urine samples were collected at each visit. Full blood count, biochemical profile, drug levels and proteinuria were measured. The study was conducted via the glomerulonephritis clinic at the Imperial College Healthcare NHS Trust, Hammersmith hospital, London. Data were collected in paper case report forms and progress of the trial was reported to and monitored by the West London Renal and Transplant Glomerulonephritis Research Group at Hammersmith Hospital, on a monthly basis.
Randomisation was performed by the clinical coordinating team participating in the trial; allocation concealment was performed by enclosing assignments in sequentially numbered, opaque, sealed envelopes.
The trial was sponsored by the Imperial College Healthcare NHS Trust and supported by the National Institute for Health Research Imperial Biomedical Research Centre. The trial was monitored by the Joint Research Compliance Office. Ethics approval was obtained by the London Hampstead REC. Trial registration: EudraCT Number 2008–001009-41.
Sample size
The sample size was based on the primary end point, time to relapse, and compared using a 1-sided log rank test assuming a 1% drop out rate and a 50% survival rate in the tacrolimus group and a 95% survival rate in the tacrolimus and MMF group with an alpha level of 0.05 and 80% power. The initial sample size was 32; this was increased to 40 in 2013 by a substantial amendment to the trial approved by the London Hampstead REC and MHRA to compensate for the higher than expected dropout rate.