Type I Interferon Receptor Antagonist (Monoclonal Antibody) Pregnancy: The limited human data in pregnant women are insufficient to inform a drug-associated risk of major birth defects, miscarriage, or adverse maternal or fetal outcome. Monoclonal IgG antibodies are actively transported across the placenta as pregnancy progresses, so fetal exposure may be greater in the third trimester. No evidence of embryotoxicity or fetal malformations was seen in pregnant cynomolgus monkeys at up to approximately 28 times the exposure at the maximum recommended human dose. A pregnancy exposure registry monitors outcomes in women exposed during pregnancy.

Anifrolumab (Type I IFN Receptor Inhibitor — SLE)

Brand names: Saphnelo

Anifrolumab is a monoclonal antibody against the type I interferon receptor, used for moderate-to-severe systemic lupus erythematosus alongside standard therapy.

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: 300 mg

Route: Intravenous infusion over a 30-minute period. Vials are for intravenous use only and must be diluted: withdraw and discard 2 mL from a 50 mL or 100 mL bag of 0.9% sodium chloride injection, then add 2 mL of anifrolumab and mix by gentle inversion (do not shake). Infuse through a line containing a sterile, low-protein-binding 0.2 to 15 micron in-line or add-on filter, and flush the line afterwards to ensure the complete dose is given.

Frequency: Every 4 weeks

ALTERNATIVE SUBCUTANEOUS REGIMEN (same label): 120 mg administered as a subcutaneous injection ONCE EVERY WEEK, using the prefilled syringe or the autoinjector pen — these presentations are for subcutaneous use only. Intended for use under the guidance of a healthcare provider. MISSED DOSE — intravenous: administer as soon as possible, maintaining a minimum interval of 14 days between infusions. Subcutaneous: the patient should inject as soon as they remember, then either start a new weekly schedule from the day the missed dose was given or resume dosing on their usual day, provided a minimum interval of 3 days is kept between subcutaneous injections. PRESENTATIONS: intravenous 300 mg/2 mL (150 mg/mL) single-dose vial; subcutaneous 120 mg/0.8 mL single-dose prefilled syringe or autoinjector. PRECAUTIONS: avoid initiating treatment during an active infection and consider interrupting therapy if a new infection develops (serious and sometimes fatal infections, including COVID-19, have occurred; the risk of respiratory infections and herpes zoster is increased). Avoid live or live-attenuated vaccines. Not recommended for use with other biologic therapies. Consider individual benefit-risk in patients with known risk factors for malignancy. ELDERLY: only 3% (n=33) of the 952 patients exposed in clinical trials were 65 or over — too few to determine whether they respond differently. PAEDIATRIC: safety and efficacy in paediatric patients have not been established — no paediatric dose is stated in the source. SOURCE: no UK SPC (eMC) record was present in this bundle — the doses above are from the US prescribing information for SAPHNELO (AstraZeneca Pharmaceuticals LP, label date 2026-04-24, https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=810dc1a8-73e1-41fc-874f-2dd1d8ed1429) and must be verified against UK labelling before publication.

Dose auto-extracted from 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.

Contraindications

History of anaphylaxis with anifrolumab

Side effects

Nasopharyngitis and upper respiratory tract infections (most common, incidence at least 5%)
Bronchitis and cough
Infusion-related reactions
Herpes zoster, including reports of disseminated herpes zoster
Serious and sometimes fatal infections (including COVID-19); serious hypersensitivity reactions including anaphylaxis and angioedema; malignancy is a labelled warning

Interactions

No formal drug interaction trials have been conducted (US PI §7)
Live or live-attenuated vaccines — avoid use in patients receiving anifrolumab (US PI §5.4)
Other biologic therapies — anifrolumab is not recommended for use with other biologic therapies (US PI §5.5)

Clinical monograph

How it works

It binds subunit 1 of the type I interferon receptor (IFNAR1), blocking the activity of type I interferons that drive much of the inflammatory pathway in lupus.

Prescribing in practice

It increases susceptibility to serious infections, including respiratory infections and herpes zoster, so screen for active infection before starting.
Given by intravenous infusion under specialist supervision; watch for hypersensitivity and infusion-related reactions.
Avoid concurrent use of other biologic therapies and avoid live vaccines.

Monitoring

Monitor for signs of infection (including herpes zoster) and for hypersensitivity or infusion reactions.

Counselling the patient

Report fever, cough, or any signs of infection promptly.
Report a new painful rash or blisters, which could indicate shingles.
Ensure vaccinations, including against shingles where appropriate, are considered before starting; avoid live vaccines.

Evidence & guidelines

Use in SLE is supported by the TULIP trial programme and relevant NICE guidance; consult the SPC for detail.

Reference: Morand et al. NEJM 2020 (TULIP-2 trial); MHRA Approval Saphnelo 2022; NICE Appraisal; BSR SLE Guidelines 2023; 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