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Targeted Synthetic DMARD — Selective JAK1 Inhibitor Pregnancy: Avoid — animal teratogenicity data; effective contraception during and for ≥1 week after stopping

Filgotinib

Brand names: Jyseleca

Adult dose

Dose: 200 mg once daily
Route: Oral
Frequency: Once daily
Max: 200 mg once daily
Can be taken with or without food. Reduce to 100 mg once daily if eGFR 30–60 mL/min, age ≥75, or if using strong P-gp inhibitors. Usually used in combination with methotrexate.

Paediatric dose

Route:
Not licensed in patients under 18 years — seek specialist opinion

Dose adjustments

Renal

eGFR 30–60 mL/min: 100 mg once daily. eGFR <30 mL/min: avoid

Hepatic

Avoid in severe hepatic impairment

Clinical pearls

  • FINCH-1 trial (NEJM 2021): filgotinib 200 mg + MTX superior to placebo + MTX in RA patients with inadequate response to MTX
  • Most selective for JAK1 among approved JAK inhibitors — theoretical advantage of preserving JAK2-dependent haematopoiesis and JAK3-dependent NK cell function
  • MHRA 2023: Male fertility counselling required — filgotinib reduced sperm count in preclinical studies; MANTA and MANTA-RAY trials in men showed reversible oligozoospermia; advise men to seek advice before attempting conception
  • Class warning (all JAK inhibitors): increased risk of serious infections, MACE, VTE, and malignancy — risk-benefit assessment essential before prescribing
  • Live zoster vaccine (Shingrix): offered to eligible patients before starting — inactivated vaccine only permitted once started

Contraindications

  • Pregnancy
  • Active serious infection including TB and herpes zoster
  • eGFR <30 mL/min
  • Active/current malignancy (except non-melanoma skin cancer)
  • Severe anaemia, neutropenia or lymphopenia
  • Live vaccines

Side effects

  • Upper respiratory tract infections
  • Urinary tract infections
  • Herpes zoster reactivation — increased risk
  • Anaemia
  • Elevated lipids
  • Possible increased VTE risk (class effect — JAK inhibitors)

Interactions

  • Strong P-gp inhibitors (e.g. itraconazole, clarithromycin) — increase filgotinib levels; reduce dose to 100 mg
  • Live vaccines — contraindicated
  • Methotrexate — no significant PK interaction; FINCH-1 shows additive efficacy

Monitoring

  • FBC at baseline, at 4–8 weeks, then 3-monthly
  • LFTs at baseline, 4–8 weeks, then 3-monthly
  • Lipid profile at 12 weeks after starting
  • TB screening before initiation
  • Skin surveillance for non-melanoma skin cancer annually

Reference: BNFc; BNF 90; NICE TA676; FINCH-1 Trial (NEJM 2021); MANTA/MANTA-RAY Trials; MHRA Drug Safety Update (male fertility). Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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