Ritlecitinib

Severe (Child-Pugh class C): Contraindicated.

Ritlecitinib May be taken with or without food. Swallow whole & do not crush/split/open.

Active serious infections (including TB). Severe hepatic impairment. Pregnancy and lactation.

Patient with chronic or recurrent infection, exposure to TB, history of serious or opportunistic infection, underlying condition that predisposes to infection; diabetes, CV risk factors, risk factors for thromboembolism (e.g. previous VTE, immobilisation), known malignancy other than successfully treated non-melanoma skin cancer or cervical cancer. Patient who has resided or travelled in areas of endemic TB or mycoses. Current or past smokers. Not recommended for use in patients with hepatitis B or C. Avoid vaccination with live or live-attenuated vaccines immediately before starting or during ritlecitinib treatment. Use of ritlecitinib in combination with other Janus kinase (JAK) inhibitors, biologic immunomodulators, ciclosporin, or other potent immunosuppressants is not recommended. Children and elderly.

Significant: Viral reactivation, including herpes virus reactivation (e.g. herpes zoster); malignancies (e.g. non-melanoma skin cancer); increased blood creatine phosphokinase, thromboembolic events (e.g. pulmonary embolism), haematologic toxicity (e.g. lymphopenia, thrombocytopenia), hypersensitivity reactions (e.g. anaphylactic reactions, urticaria, rash).
Gastrointestinal disorders: Diarrhoea.
Investigations: Increased ALT and AST.
Nervous system disorders: Dizziness, headache.
Skin and subcutaneous tissue disorders: Acne, folliculitis.
Potentially Fatal: Serious bacterial, viral, fungal and opportunistic infections (e.g. TB, appendicitis, COVID-19 infection [including pneumonia], sepsis); risk of major adverse CV events (e.g. sudden CV death, MI, stroke).

PO: Z (Teratogenicity was observed in animal studies. Contraindicated during pregnancy in some product literature. Consult product literature for specific recommendations.)

Women of childbearing potential must use effective contraception during treatment and for 1 month after the last dose.

Evaluate for the presence of TB and viral hepatitis before treatment initiation. Monitor lymphocyte and platelet counts (before treatment initiation, 4 weeks after initiation, then periodically thereafter); LFTs (at baseline and periodically thereafter). Assess for signs and symptoms of infection (during and after treatment) or viral reactivation (during treatment). Perform periodic skin examinations during treatment, particularly in patients at risk of skin cancer.

May decrease serum concentration with strong CYP3A inducers (e.g. rifampicin). May increase serum concentration with strong CYP3A inhibitors (e.g. itraconazole). May increase the serum concentrations of CYP3A substrates (e.g. midazolam, quinidine, ciclosporin, dihydroergotamine, ergotamine, pimozide, colchicine, everolimus, tacrolimus, sirolimus), CYP1A2 substrates (e.g. caffeine, tizanidine, theophylline, pirfenidone), and organic cation transporter 1 (OCT1) substrates (e.g. sumatriptan).

Description:
Mechanism of Action: Ritlecitinib is a selective and irreversible Janus kinase 3 (JAK3) inhibitor and an inhibitor of the tyrosine kinase expressed in hepatocellular carcinoma (TEC) kinase family. It blocks the adenosine triphosphate (ATP) binding site, thereby inhibiting the JAK3 and the TEC kinase family, which may result in inhibition of T cell activation. In cellular setting, ritlecitinib inhibits the cytokine-induced phosphorylation of signal transducer and activator of transcription (STAT) proteins mediated by JAK3-dependent receptors. Additionally, it inhibits the signalling of immune receptors dependent on TEC kinase family members.
Onset: Within 4-8 weeks.
Pharmacokinetics:
Absorption: Bioavailability: Approx 64%. Time to peak plasma concentration: 1 hour.
Distribution: Plasma protein binding: Approx 14%, mainly to albumin.
Metabolism: Metabolised in the liver by glutathione S-transferase, CYP3A, CYP1A2, CYP2C8 and CYP2C9.
Excretion: Via urine (approx 66%; approx 4% as unchanged drug); faeces (approx 20%). Terminal elimination half-life: 1.3-2.3 hours.

Source: National Center for Biotechnology Information. PubChem Compound Summary for CID 118115473, Ritlecitinib. https://pubchem.ncbi.nlm.nih.gov/compound/Ritlecitinib. Accessed Oct. 27, 2025.

Store below 30°C. Protect from light.

Immunosuppressants

L04AF08 - ritlecitinib ; Belongs to the class of Janus-associated kinase (JAK) inhibitors. Used as immunosuppressants.

Joint Formulary Committee. Ritlecitinib. British National Formulary [online]. London. BMJ Group and Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 11/08/2025.

Litfulo 50 mg Hard Capsules (Pfizer [Malaysia] Sdn. Bhd.). National Pharmaceutical Regulatory Agency - Ministry of Health Malaysia. https://www.npra.gov.my. Accessed 11/08/2025.

Litfulo 50 mg Hard Capsules (Pfizer Limited). MHRA. https://products.mhra.gov.uk. Accessed 11/08/2025.

Litfulo Capsule (Pfizer Laboratories Div Pfizer Inc). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed. Accessed 11/08/2025.

Ritlecitinib Tosylate. UpToDate Lexidrug, AHFS DI (Adult and Pediatric) Online. American Society of Health-System Pharmacists, Inc. Waltham, MA. UpToDate, Inc. https://online.lexi.com. Accessed 11/08/2025.

Ritlecitinib. UpToDate Lexidrug, Lexi-Drugs Multinational Online. Waltham, MA. UpToDate, Inc. https://online.lexi.com. Accessed 11/08/2025.