Anti-BLyS Monoclonal Antibody (B-cell Inhibitor) Pregnancy: There are limited data from use in pregnant women; post-marketing pregnancy registry data are too small for definitive conclusions about a potential risk of birth defects. Besides the expected pharmacological effect (reduction of B cells), monkey studies do not indicate direct or indirect harmful effects on reproduction. Benlysta should not be used during pregnancy unless the potential benefit justifies the potential risk to the foetus. Women of childbearing potential must use effective contraception during treatment and for at least 4 months after the last treatment. Breast-feeding: it is unknown whether belimumab is excreted in human milk, but it was detected in the milk of female monkeys and maternal IgG is excreted in breast milk — decide whether to discontinue breast-feeding or the therapy. Fertility: no human data; effects on fertility have not been formally evaluated in animals.

Belimumab

Brand names: Benlysta

Belimumab is a monoclonal antibody used as add-on therapy in active autoantibody-positive systemic lupus erythematosus and in lupus nephritis.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: SLE or active lupus nephritis: 10 mg/kg on Days 0, 14 and 28, and at 4-week intervals thereafter

Route: Intravenous infusion over a 1-hour period (must be reconstituted and diluted before administration; must NOT be given as an intravenous bolus)

Frequency: Days 0, 14 and 28, then every 4 weeks

Source: UK SPC (eMC) §4.2 for Benlysta 120 mg powder for concentrate for solution for infusion (https://www.medicines.org.uk/emc/product/4679/smpc). VERBATIM: 'In patients with SLE or active lupus nephritis, the recommended dose regimen is 10 mg/kg Benlysta on Days 0, 14 and 28, and at 4-week intervals thereafter.' The unit is mg per kg of body weight per dose. INITIATION AND SUPERVISION: treatment should be initiated and supervised by a qualified physician experienced in the diagnosis and treatment of SLE, and infusions administered by a qualified healthcare professional trained to give infusion therapy, in an environment where resources for managing severe or life-threatening hypersensitivity and infusion reactions are immediately available. Patients should remain under clinical supervision for several hours following at least the first 2 infusions because of the possibility of a late-onset reaction; acute hypersensitivity symptoms have been reported several hours after the infusion and recurrence after initial treatment has been observed. PREMEDICATION: an antihistamine, with or without an antipyretic, may be administered before the infusion. INFUSION: infuse over 1 hour; the rate may be slowed or interrupted if an infusion reaction develops, and the infusion must be discontinued immediately if a potentially life-threatening adverse reaction occurs. REVIEW: the patient's condition should be evaluated continuously; in SLE, discontinuation should be considered if there is no improvement in disease control after 6 months of treatment. LUPUS NEPHRITIS: Benlysta should be used in combination with corticosteroids and mycophenolate or cyclophosphamide for induction, or mycophenolate or azathioprine for maintenance. TRANSITION TO SUBCUTANEOUS (the subcutaneous presentation has its own SPC, not retrieved here): in SLE the first subcutaneous injection should be given 1 to 4 weeks after the last intravenous dose; in lupus nephritis the first 200 mg subcutaneous dose should be given 1 to 2 weeks after the last intravenous dose, and only after the patient has completed the first 2 intravenous doses. ELDERLY: data in patients >=65 years are limited — use with caution; dose adjustment is not required. HEPATIC IMPAIRMENT: no specific studies; patients are unlikely to require dose adjustment. No maximum dose is stated in §4.2. §4.5 was not retrieved from the UK SPC in this bundle — the interaction note below is from the US BENLYSTA label §7.

Paediatric dose

Dose: 10 mg/kg

Route: Intravenous infusion over a 1-hour period (not as a bolus)

Frequency: Days 0, 14 and 28, then at 4-week intervals thereafter

Max: No maximum dose stated in the SPC

SLE only, children aged 5 years and older: 'The recommended dose regimen for children aged 5 years and older is 10 mg/kg Benlysta on Days 0, 14 and 28, and at 4-week intervals thereafter' (UK SPC §4.2, Benlysta 120 mg powder for concentrate for solution for infusion). Safety and efficacy in children aged below 5 years have not been established (no data). For LUPUS NEPHRITIS, safety and efficacy in children and adolescents below 18 years with severe active lupus nephritis have NOT been established (no data) — do not extrapolate this SLE regimen to paediatric lupus nephritis. Verify against a children's formulary before use.

Dose adjustments

Renal

Dose adjustment is not required in patients with mild, moderate or severe renal impairment on the basis of available information (studied in a limited number of SLE patients). Caution is recommended in severe renal impairment due to the lack of data.

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Paediatric weight-based calculator

Patient weight (kg)

Verify in a children's formulary

Contraindications

Hypersensitivity to the active substance or to any of the excipients

Side effects

Bacterial infections (very common); in lupus nephritis the most frequent reactions (>5%) were upper respiratory tract infection, urinary tract infection and herpes zoster
Nasopharyngitis — the most frequently reported adverse reaction in SLE (>=5% and >=1% more than placebo)
Severe or life-threatening hypersensitivity reactions and infusion reactions, including delayed onset (several hours after infusion) and recurrence after initial treatment
Severe cutaneous adverse reactions — Stevens-Johnson syndrome and toxic epidermal necrolysis have been reported
US label common reactions (>=5%): nausea, diarrhoea, pyrexia, bronchitis, insomnia, pain in extremity, depression, migraine, pharyngitis and injection site reactions (subcutaneous administration); serious infections, depression and suicidality, and malignancy are labelled warnings
Note: the UK §4.8 adverse reaction table was truncated at the source-fetch limit — this list is not complete

Interactions

No formal drug interaction studies have been performed with belimumab (US label §7)
In clinical trials belimumab was given concomitantly with corticosteroids, antimalarials, immunomodulatory and immunosuppressive agents (azathioprine, cyclophosphamide, methotrexate, mycophenolate), angiotensin pathway antihypertensives, statins and NSAIDs without evidence of a clinically meaningful effect of these on belimumab pharmacokinetics
The effect of belimumab on the pharmacokinetics of other drugs has not been evaluated
Note: the UK §4.5 section was not retrieved in this bundle

Clinical monograph

How it works

It binds and inhibits B-lymphocyte stimulator (BLyS/BAFF), reducing the survival and activity of autoreactive B cells that contribute to lupus.

Prescribing in practice

Serious infections can occur and treatment should not be started during an active severe infection; hypersensitivity and infusion or injection reactions are also recognised.
It is given by intravenous infusion or subcutaneous injection as add-on therapy to standard treatment.
It has not been studied in severe active central nervous system lupus, and psychiatric events including depression have been reported.

Monitoring

Monitor for infections, hypersensitivity and new or worsening mood or psychiatric symptoms during treatment.

Counselling the patient

Report signs of infection and any new low mood or thoughts of self-harm promptly.
Avoid live vaccines during treatment.

Evidence & guidelines

Belimumab is recommended by NICE as an add-on option in active autoantibody-positive systemic lupus erythematosus on the basis of its trial evidence.

Reference: NICE TA397; BLISS trials; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways