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JAK3/TEC kinase inhibitor Pregnancy: Available data from clinical trials in pregnant women are insufficient to identify a drug-associated risk of major birth defects, miscarriage or other adverse maternal or fetal outcomes. In animal reproduction studies, oral administration to pregnant rats and rabbits during organogenesis caused fetotoxicity and fetal malformations at exposures 49 and 55 times the maximum recommended human dose respectively. A pregnancy exposure registry exists.

Ritlecitinib

Brand names: Litfulo

Ritlecitinib is an oral, selective Janus kinase 3 (JAK3) and TEC-family kinase inhibitor used for severe alopecia areata in adolescents and adults.

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: 50 mg
Route: Oral (capsules, swallowed whole with or without food; do not crush, split or chew)
Frequency: Once daily
PRIOR TO INITIATION: evaluate for tuberculosis infection (initiation is not recommended in patients with active TB; for latent TB, or a negative latent TB test in patients at high risk, start preventive therapy before initiation); screen for viral hepatitis in accordance with clinical guidelines (initiation is not recommended in patients with hepatitis B or hepatitis C); do not initiate if the absolute lymphocyte count (ALC) is <500/mm3 or the platelet count is <100,000/mm3; update immunisations according to current immunisation guidelines and avoid live vaccines during or shortly prior to treatment. Missed dose: administer as soon as possible unless it is less than 8 hours before the next dose, in which case skip the missed dose, then resume the regular schedule. Hepatic impairment: not recommended in patients with severe (Child-Pugh C) hepatic impairment. TREATMENT INTERRUPTION/DISCONTINUATION: discontinue if the platelet count is <50,000/mm3; interrupt if ALC is <500/mm3 and restart once the ALC returns above this value. ALC and platelet counts are recommended before initiation, at 4 weeks after initiation, and thereafter according to routine patient management. A temporary treatment interruption of less than 6 weeks is not expected to result in significant loss of regrown scalp hair. Elderly: no dose adjustment is required for patients 65 years of age and over, but caution should be used because of the higher incidence of infections in the elderly. Paediatric: safety and effectiveness for alopecia areata have been established in patients aged 12 years and older (the same 50 mg once-daily dose was used in the trials); safety and efficacy have NOT been established under 12 years of age. No per-kg paediatric dose is stated — verify paediatric use against a children's formulary. This is US labelling; a UK SPC was not retrieved.

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

  • Known hypersensitivity to ritlecitinib or any of its excipients

Side effects

  • Headache
  • Diarrhoea
  • Acne
  • Rash and urticaria
  • Folliculitis
  • Also reported: pyrexia, atopic dermatitis, dizziness, increased blood creatine phosphokinase, herpes zoster, decreased red blood cell count and stomatitis

Interactions

  • Certain CYP3A substrates — ritlecitinib is a CYP3A inhibitor and increases their exposure; consider additional monitoring and dosage adjustment where small concentration changes may lead to serious adverse reactions
  • Certain CYP1A2 substrates — ritlecitinib is a CYP1A2 inhibitor and increases their exposure; consider additional monitoring and dosage adjustment where small concentration changes may lead to serious adverse reactions
  • Strong CYP3A inducers — coadministration is not recommended
  • Live vaccines — avoid during or shortly prior to treatment

Clinical monograph

How it works

It irreversibly inhibits JAK3 and TEC kinases, dampening cytokine and cytotoxic T-cell signalling implicated in the autoimmune attack on hair follicles.

Prescribing in practice

  • As a JAK inhibitor it carries class warnings for serious infection, venous thromboembolism, major adverse cardiovascular events and malignancy, so assess risk before and during treatment per the MHRA class review.
  • Screen for active and latent tuberculosis and viral hepatitis, and ensure age-appropriate vaccinations are up to date before starting.
  • Avoid live vaccines during treatment and review concurrent immunosuppression.

Monitoring

Monitor full blood count, lipids and liver function and remain alert for signs of infection, thrombosis or malignancy during treatment.

Counselling the patient

  • Report fever, persistent cough or other signs of infection promptly.
  • Seek urgent care for symptoms of blood clots such as leg swelling, chest pain or breathlessness.
  • Hair regrowth may take several months and benefit may be lost if treatment is stopped.

Evidence & guidelines

Efficacy in severe alopecia areata was demonstrated in the phase 2b/3 ALLEGRO programme.

Reference: NICE TA958; MHRA JAKi class; SmPC; 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).

Related

Curated clinical cross-links plus same-class fallbacks.

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