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JAK1 Inhibitor (UC) Pregnancy: Contraindicated — teratogenic. Effective contraception required during treatment and for at least 1 week after stopping. MHRA warning.

Filgotinib

Brand names: Jyseleca

Adult dose

Dose: 200 mg once daily (standard); 100 mg once daily (renal impairment or concurrent strong CYP3A4 inhibitors)
Route: Oral
Frequency: Once daily
Max: 200 mg/day
UC only — CD licence was NOT granted by EMA (insufficient evidence, MANTA trial safety concerns). Standard dose 200 mg daily. Reduce to 100 mg if eGFR 30–60 mL/min or with strong CYP3A4 inhibitors. Source: BNF 90; MHRA.

Paediatric dose

Dose: Not licensed under 18 years N/A/kg
Route: Oral
Frequency: N/A
Max: N/A
Not licensed for paediatric use.

Dose adjustments

Renal

eGFR 30–60 mL/min: reduce to 100 mg once daily. eGFR <30 mL/min: not recommended.

Hepatic

Severe hepatic impairment (Child-Pugh C): not recommended.

Paediatric weight-based calculator

Not licensed for paediatric use.

Clinical pearls

  • SELECTION trial (Lancet 2021): 26.1% remission with filgotinib 200 mg vs 15.3% placebo at week 10 (UC). CD licence application rejected by EMA in 2021 — insufficient efficacy data at 200 mg dose — ONLY licensed for UC in UK/EU.
  • MANTA trial male fertility warning: MHRA issued warning that filgotinib reduces sperm count in healthy males (reversible on stopping). Male patients who wish to father children should be counselled and an alternative considered. Unique concern not shared by other JAK inhibitors — related to JAK1 specificity and testicular JAK signalling.
  • MHRA JAK class restrictions 2022 apply equally to filgotinib: use only if adequate alternative unavailable in patients aged ≥65 years, smokers, or those with CV risk factors, VTE history, or malignancy history.
  • JAK1 selectivity: filgotinib is more JAK1-selective than tofacitinib (JAK1/3) or baricitinib (JAK1/2) — theoretically lower risk of erythropoiesis suppression (JAK2) and thrombocytopenia, but class warnings still apply.
  • Hepatitis B serology mandatory pre-treatment: HBV reactivation risk. IGRA for latent TB before starting. Source: BNF 90; MHRA Drug Safety Update 2022; Feagan et al. Lancet 2021 (SELECTION).

Contraindications

  • Active serious infection (screen for TB before starting)
  • Severe renal impairment (eGFR <30 mL/min)
  • Pregnancy and breastfeeding (teratogenic — MHRA warning)
  • Males of reproductive potential who wish to father children (MANTA trial — see pearls)
  • Concurrent use with other JAK inhibitors or biologics

Side effects

  • Nasopharyngitis, upper respiratory tract infections (most common)
  • Herpes zoster reactivation (JAK class warning)
  • Anaemia, neutropenia (monitor FBC)
  • Elevated liver enzymes
  • Nausea, headache
  • MHRA JAK class warnings: MACE, VTE, malignancy, all-cause mortality — particularly in high-risk patients

Interactions

  • Strong CYP3A4 inhibitors (clarithromycin, itraconazole): increase filgotinib exposure — reduce dose to 100 mg
  • Strong CYP3A4 inducers (rifampicin): reduce filgotinib efficacy — avoid
  • Live vaccines: contraindicated during treatment and for recommended washout after stopping
  • Other JAK inhibitors or biologics: do not combine

Monitoring

  • FBC at baseline and periodically (ANC, lymphocytes, haemoglobin, platelets)
  • Liver function tests at baseline and periodically
  • Lipid profile at 12 weeks
  • Sperm count discussion and fertility counselling in males before starting
  • Infection signs throughout (TB, herpes zoster, opportunistic infections)
  • Clinical response at 8–12 weeks — discontinue if no response

Reference: BNFc; BNF 90; Feagan et al. Lancet 2021 (SELECTION); MHRA Drug Safety Update 2022 (JAK class); EMA CHMP assessment report filgotinib. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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