Saphnelo (Anifrolumab)
anifrolumab-fnia
Indications
| Indication | Approved Population | Therapy Type | Status |
|---|---|---|---|
| Moderate to severe systemic lupus erythematosus (SLE) | Adults (≥18 years) receiving standard therapy | Add-on to standard therapy | FDA Approved |
Anifrolumab is the first type I interferon receptor antagonist approved for SLE. It was approved on July 30, 2021 based on efficacy data from the MUSE, TULIP-1, and TULIP-2 trials. Approximately 60–80% of adult patients with active SLE have elevated type I interferon-inducible gene expression, which is the pharmacological target of anifrolumab. Efficacy has not been evaluated in severe active lupus nephritis or severe active CNS lupus, and anifrolumab is not recommended for those settings. The 2023 EULAR recommendations and 2025 ACR guidelines both position anifrolumab alongside belimumab as a biologic option for patients with inadequate response to standard therapy.
Cutaneous lupus erythematosus (refractory): Post hoc analyses of TULIP trials showed significant improvements in cutaneous disease activity (CLASI scores). EULAR 2023 lists anifrolumab as an option for refractory cutaneous lupus. Evidence quality: Moderate (post hoc of RCTs).
Lupus nephritis: Phase 2 data (TULIP-LN) are exploratory; not FDA-approved for this indication. Evidence quality: Low.
Myositis / dermatomyositis: Case reports and small series suggest potential benefit given the role of type I IFN; clinical trials underway. Evidence quality: Very low.
Anifrolumab Dosing
| Clinical Scenario | Starting Dose | Maintenance Dose | Maximum Dose | Notes |
|---|---|---|---|---|
| Moderate-to-severe SLE — standard regimen | 300 mg IV q4wk | 300 mg IV q4wk | 300 mg q4wk | Infuse over 30 minutes through 0.2–15 μm in-line filter No loading dose required; steady state reached by Day 85 |
| Missed dose management | 300 mg IV as soon as possible | 300 mg IV q4wk | 300 mg | Maintain minimum 14-day interval between infusions Resume regular q4wk schedule thereafter |
| Patients with history of infusion reactions | 300 mg IV q4wk | 300 mg IV q4wk | 300 mg q4wk | Consider premedication (e.g., antihistamine) before infusion No dose reduction; same dose for all adult patients regardless of weight |
Withdraw 2 mL from a 50 mL or 100 mL bag of 0.9% sodium chloride, then add 2 mL (300 mg) of anifrolumab. Mix by gentle inversion — do not shake. Administer through an in-line or add-on filter (0.2–15 μm). Flush the line with 25 mL normal saline after infusion to ensure full dose delivery. Do not co-administer other medications through the same IV line. Unlike belimumab, anifrolumab is a fixed flat dose (300 mg) regardless of body weight, simplifying preparation and reducing waste.
Pharmacology
Mechanism of Action
Anifrolumab is a fully human IgG1κ monoclonal antibody that binds with high affinity and specificity to subunit 1 of the type I interferon receptor (IFNAR1). By occupying this receptor subunit, anifrolumab blocks signalling by all type I interferons (including IFN-α, IFN-β, and IFN-κ), which are key drivers of inflammation in SLE. Beyond simple competitive inhibition, anifrolumab induces internalisation and downregulation of surface IFNAR1, further reducing the cell’s capacity to respond to type I IFN stimulation. Downstream effects include suppression of IFN-responsive gene expression, inhibition of plasma cell differentiation, and normalisation of peripheral T-cell subsets. In clinical trials, the 300 mg dose achieved sustained neutralisation (≥80%) of a 21-gene type I IFN gene signature from Week 4 through Week 52, which returned to baseline within 8–12 weeks after treatment cessation.
ADME Profile
| Parameter | Value | Clinical Implication |
|---|---|---|
| Absorption | IV infusion (100% bioavailability); non-linear PK with more-than-dose-proportional AUC increases across 100–1000 mg range; steady state by Day 85; accumulation ratio 1.36 (Cmax), 2.49 (Ctrough) | Fixed flat dose (300 mg) regardless of body weight; no loading dose needed. SC formulation (Phase 1: ~87% relative bioavailability) is under FDA review |
| Distribution | Vss = 6.23 L (typical 69.1 kg patient) | Small Vd consistent with a monoclonal antibody confined primarily to the intravascular and interstitial compartments |
| Metabolism | Proteolytic degradation into peptides and amino acids; dual elimination via reticuloendothelial system and IFNAR1-mediated target-mediated drug disposition (TMDD) | No CYP involvement; no dose adjustment for hepatic impairment. Non-linear clearance means higher doses produce disproportionately greater exposure |
| Elimination | CL = 0.193 L/day (at 300 mg IV q4wk); serum concentrations undetectable in 95% of patients ~16 weeks after last dose at steady state, ~10 weeks after a single dose | Pharmacodynamic effects (IFN gene signature suppression) reverse within 8–12 weeks of stopping therapy; longer washout than conventional immunosuppressants |
Side Effects
| Adverse Effect | Incidence | Clinical Note |
|---|---|---|
| Upper respiratory tract infections (includes nasopharyngitis, pharyngitis) | 34% (vs 23% placebo) | Most common adverse reaction; significant excess over placebo reflecting type I IFN blockade and impaired mucosal antiviral defence |
| Bronchitis (includes viral bronchitis, tracheobronchitis) | 11% (vs 5.2% placebo) | More than double the placebo rate; monitor for lower respiratory tract progression |
| Adverse Effect | Incidence | Clinical Note |
|---|---|---|
| Infusion-related reactions | 9.4% (vs 7.1% placebo) | Mild-moderate; most common symptoms: headache, nausea, vomiting, fatigue, dizziness |
| Herpes zoster | 6.1% (vs 1.3% placebo) | Nearly 5-fold increase over placebo; 2 cases of disseminated disease with hospitalisation. Multidermatomal involvement reported |
| Cough | 5.0% (vs 3.2% placebo) | May be part of respiratory infection spectrum; evaluate for lower tract involvement |
| Respiratory tract infection (includes viral, bacterial) | 3.3% (vs 1.5% placebo) | Distinguish from URTI; consider chest imaging if symptoms persistent |
| Hypersensitivity reactions | 2.8% (vs 0.6% placebo) | Predominantly mild-moderate; includes angioedema (n=2 serious). Rarely led to discontinuation |
| Adverse Effect | Estimated Frequency | Typical Onset | Required Action |
|---|---|---|---|
| Serious infections (pneumonia most frequent) | 4.8% (vs 5.6% placebo) | Any time during treatment | Consider interrupting anifrolumab; treat aggressively. COVID-19 and pneumonia were most common in LTE |
| Fatal infections (including COVID-19) | 0.4% (vs 0.2% placebo) | Any time | Evaluate infection risk prior to initiation; remain vigilant throughout therapy |
| Disseminated herpes zoster | 0.4% (2/459) | Variable; weeks to months | Hospitalisation required; initiate IV antiviral therapy; consider treatment interruption |
| Anaphylaxis | Very rare (1 case in development programme at 150 mg dose) | During or shortly after infusion | Discontinue permanently; administer emergency treatment. Contraindicated after anaphylaxis |
| Angioedema | Rare (4 reports at 300 mg; 2 serious) | During or after infusion | Manage per hypersensitivity protocol; consider premedication for future doses if mild |
| Malignancy (excluding NMSC) | 0.7% (vs 0.6% placebo) | Any time | Assess individual risk before prescribing; monitor for malignancy; consider risk-benefit if malignancy develops |
Herpes zoster is the most notable safety signal distinguishing anifrolumab from placebo, with an EAIR of 6.9 vs 1.5 per 100 patient-years. The risk reflects impaired type I IFN-mediated antiviral defence. Before initiating therapy, verify varicella immunity and consider recombinant zoster vaccine (Shingrix) in eligible patients aged ≥50 years or those on immunosuppressants. Advise patients to report any new painful, blistering rashes immediately. Early antiviral therapy (valaciclovir or aciclovir) should be initiated promptly for suspected zoster.
Drug Interactions
No formal drug interaction studies have been conducted with anifrolumab. As a monoclonal antibody eliminated through proteolytic degradation and IFNAR1-mediated target-mediated drug disposition, anifrolumab does not interact with CYP450 enzymes. Population pharmacokinetic analyses confirmed no clinically meaningful effect of concomitant corticosteroids, antimalarials, immunosuppressants, NSAIDs, ACE inhibitors, or statins on anifrolumab pharmacokinetics. The primary interaction concerns relate to additive immunosuppression and vaccine interference.
Monitoring
- Infection surveillanceEvery visit
RoutineOverall infections occurred in 69.7% (vs 55.4% placebo). Screen for URI, bronchitis, pneumonia, and herpes zoster at each encounter. Consider treatment interruption for new serious infections. - Herpes zoster vigilanceEvery visit
RoutineIncidence 6.1% vs 1.3% placebo (EAIR 6.9 vs 1.5/100 PY). Ask about new rashes or pain in dermatomal distribution. Verify vaccination status before initiation. Early antiviral treatment critical for suspected cases. - Infusion monitoringDuring and after each infusion
Trigger-basedInfusion-related reactions in 9.4% (vs 7.1% placebo). Administer in settings prepared for anaphylaxis management. Monitor for headache, nausea, vomiting, dizziness. Serious hypersensitivity occurred in 0.6%. - SLE disease activityEvery 3–6 months
RoutineTrack SLEDAI-2K, BILAG, PGA, anti-dsDNA, complement C3/C4. Treatment led to numerical anti-dsDNA reductions and complement normalisation through Week 52. BICLA and SRI-4 as clinical response metrics. - Steroid taperingWeeks 8–40 per protocol
RoutinePatients on baseline OCS ≥10 mg/day should attempt tapering to ≤7.5 mg/day between Weeks 8 and 40, as demonstrated in TULIP-2 and -3. Monitor for flare during taper. - Malignancy screeningPer standard guidelines
RoutineMalignancies (including NMSC) reported in 1.3% vs 0.6% placebo. Rodent IFNAR1 blockade models showed increased carcinogenic potential. Maintain age-appropriate cancer screening.
Contraindications & Cautions
Absolute Contraindications
- History of anaphylaxis with anifrolumab-fnia: The sole absolute contraindication per the FDA label.
Relative Contraindications (Specialist Input Recommended)
- Clinically significant active infection: Avoid initiating treatment until the infection resolves or is adequately treated. Particular caution with chronic or recurrent infections given the elevated overall infection rate.
- Severe active lupus nephritis or severe active CNS lupus: Efficacy has not been evaluated; use is not recommended.
- Concomitant biologic therapy: Not studied in combination with other biologics including B-cell-targeted agents. A wash-out period of at least 5 half-lives of the prior biologic is required before starting anifrolumab.
- Known malignancy or high malignancy risk: Increased carcinogenic potential observed in rodent models of IFNAR1 blockade. Assess individual risk-benefit before prescribing.
Use with Caution
- History of recurrent infections or herpes zoster: Consider varicella immunity status and recombinant zoster vaccination before initiation.
- Geriatric patients: Only 3% (n=20) of clinical trial patients were ≥65 years; insufficient data to determine differential responses.
- Pregnancy: Monoclonal IgG antibodies cross the placenta, particularly during the third trimester. Animal studies showed no fetal harm at 28x MRHD. No adequate human data; pregnancy registry available (1-877-693-9268).
The anifrolumab prescribing information highlights warnings for serious and sometimes fatal infections (including COVID-19), increased risk of respiratory infections and herpes zoster, hypersensitivity reactions including anaphylaxis and angioedema, potential increased malignancy risk, and interference with live vaccine responses. While there is no traditional boxed warning, these warnings and precautions carry significant weight for clinical decision-making and require pre-treatment risk assessment and ongoing surveillance.
Patient Counselling
Purpose of Therapy
Anifrolumab is a biologic medicine that works by blocking type I interferon, a group of proteins that drive inflammation in lupus. It is given as an intravenous infusion every 4 weeks alongside your other lupus medications. The goal is to reduce disease activity, improve skin and joint symptoms, and potentially allow your doctors to lower your steroid dose over time. Meaningful improvements are typically assessed at 6–12 months of therapy.
How to Take
Anifrolumab is administered as a 30-minute intravenous infusion by a healthcare provider every 4 weeks. Unlike some other lupus biologics, it is a fixed dose (not based on your weight). You will be monitored during the infusion. If you miss a scheduled infusion, it should be rescheduled as soon as possible, maintaining at least 14 days between doses.
Sources
- AstraZeneca Pharmaceuticals LP. SAPHNELO (anifrolumab-fnia) prescribing information. Revised August 2024. FDA Label Primary source for all dosing, safety, pharmacokinetic, and clinical trial data in this monograph.
- European Medicines Agency. Saphnelo (anifrolumab) Summary of Product Characteristics. EMA SmPC European regulatory label including SC bioavailability data and additional PK parameters.
- Morand EF, Furie R, Tanaka Y, et al. Trial of anifrolumab in active systemic lupus erythematosus (TULIP-2). N Engl J Med. 2020;382(3):211-221. doi:10.1056/NEJMoa1912196 Pivotal Phase 3 trial establishing BICLA response (47.8% vs 31.5% placebo at Week 52) and steroid reduction benefit.
- Furie RA, Morand EF, Bruce IN, et al. Type I interferon inhibitor anifrolumab in active systemic lupus erythematosus (TULIP-1). Lancet Rheumatol. 2019;1(4):e208-e219. doi:10.1016/S2665-9913(19)30076-1 Phase 3 trial; SRI-4 primary endpoint not met (49.0% vs 43.0%), but BICLA response was 47.1% vs 30.2%.
- Furie R, Khamashta M, Merrill JT, et al. Anifrolumab, an anti-interferon-α receptor monoclonal antibody, in moderate-to-severe systemic lupus erythematosus (MUSE). Arthritis Rheumatol. 2017;69(2):376-386. doi:10.1002/art.39962 Phase 2b trial demonstrating dose-response and selecting 300 mg as optimal dose; 1000 mg offered no additional efficacy but increased herpes zoster.
- Vital EM, Merrill JT, Morand EF, et al. Anifrolumab efficacy and safety by type I interferon gene signature and target engagement: post hoc analysis of TULIP-1 and TULIP-2. Ann Rheum Dis. 2022;81(7):951-961. doi:10.1136/annrheumdis-2021-221973 Post hoc analysis showing enhanced efficacy in patients with high type I IFN gene signature and correlation between IFN neutralisation and clinical response.
- Fanouriakis A, Kostopoulou M, Andersen J, et al. EULAR recommendations for the management of systemic lupus erythematosus: 2023 update. Ann Rheum Dis. 2024;83(1):15-29. doi:10.1136/ard-2023-224762 EULAR guideline positioning anifrolumab alongside belimumab as a biologic option for patients with inadequate response to standard therapy.
- Sammaritano LR, Askanase A, Bermas BL, et al. 2025 American College of Rheumatology (ACR) guideline for the treatment of systemic lupus erythematosus. Arthritis Care Res. 2025. doi:10.1002/acr.25690 2025 ACR guideline conditionally recommending anifrolumab for moderate-to-severe cutaneous and musculoskeletal SLE refractory to standard treatment.
- Crow MK. Type I interferon in the pathogenesis of lupus. J Immunol. 2014;192(12):5459-5468. doi:10.4049/jimmunol.1002795 Seminal review of the role of type I interferons in SLE pathogenesis, providing mechanistic rationale for IFNAR blockade.
- Peng L, Oganesyan V, Wu H, et al. Molecular basis for antagonistic activity of anifrolumab, an anti-interferon-α receptor 1 antibody. MAbs. 2015;7(2):428-439. doi:10.1080/19420862.2015.1007810 Structural and functional characterisation of anifrolumab binding to IFNAR1 and receptor internalisation mechanism.
- Almquist J, Kuruvilla D, Engel S, et al. Nonlinear population pharmacokinetics of anifrolumab in healthy volunteers and patients with systemic lupus erythematosus. J Clin Pharmacol. 2022;62(9):1163-1176. doi:10.1002/jcph.2055 Population PK analysis across 5 studies establishing clearance (0.193 L/day), Vss (6.23 L), and washout predictions (~16 weeks post-discontinuation).
- Tummala R, Rouse T, Engel S, et al. Safety, tolerability and pharmacokinetics of subcutaneous and intravenous anifrolumab in healthy volunteers. Lupus Sci Med. 2018;5(1):e000252. doi:10.1136/lupus-2017-000252 Phase 1 healthy volunteer study establishing SC bioavailability (~87% of IV AUC), Tmax 4–7 days, and dose-proportional SC PK.
- Kuruvilla D, Engel S, Engel L, et al. Clinical pharmacokinetics, pharmacodynamics, and immunogenicity of anifrolumab. Clin Pharmacokinet. 2023;62(5):655-671. doi:10.1007/s40262-023-01240-8 Comprehensive review of anifrolumab PK/PD across clinical development including exposure-response relationships and immunogenicity (ADA incidence 2.6%).