Last reviewed 2026-04-20 · How we verify

Litfulo (ritlecitinib)

Litfulo works by blocking the activity of a specific enzyme called tyrosine-protein kinase ITK/TSK.

At a glance

Mechanism of action

LITFULO is kinase inhibitor. Ritlecitinib irreversibly inhibits Janus kinase (JAK3) and the tyrosine kinase expressed in hepatocellular carcinoma (TEC) kinase family by blocking the adenosine triphosphate (ATP) binding site. In cellular settings, ritlecitinib inhibits cytokine induced STAT phosphorylation mediated by JAK3-dependent receptors. Additionally, ritlecitinib inhibits signaling of immune receptors dependent on TEC kinase family members. The relevance of inhibition of specific JAK or TEC family enzymes to therapeutic effectiveness is not currently known.

Approved indications

• Alopecia areata

Boxed warnings

• WARNING: SERIOUS INFECTIONS, MORTALITY, MALIGNANCY, MAJOR ADVERSE CARDIOVASCULAR EVENTS (MACE), and THROMBOSIS WARNING: SERIOUS INFECTIONS, MORTALITY, MALIGNANCY, MAJOR ADVERSE CARDIOVASCULAR EVENTS (MACE), and THROMBOSIS See full prescribing information for complete boxed warning. • Increased risk of serious bacterial, fungal, viral, and opportunistic infections that may lead to hospitalization or death, including tuberculosis (TB). Interrupt treatment if serious infection occurs until the infection is controlled. LITFULO should not be given to patients with active tuberculosis. Test for latent TB before and during therapy; start treating latent TB prior to use. Monitor all patients for active TB during treatment, even patients with initial negative, latent TB test. ( 5.1 ). Monitor all patients for signs and symptoms of infection during and after treatment with LITFULO. ( 5.1 ) • Higher rate of all-cause mortality, including sudden cardiovascular death with another Janus kinase inhibitor (JAK) vs. TNF blockers in rheumatoid arthritis (RA) patients. LITFULO is not approved for use in RA patients. ( 5.2 ) • Malignancies were reported in patients treated with LITFULO ( 5.3 ). Higher rate of lymphomas and lung cancers with another JAK inhibitor vs. TNF blockers in RA patients. • Higher rate of MACE (defined as cardiovascular death, myocardial infarction, and stroke) with another JAK inhibitor vs. TNF blockers in RA patients. ( 5.4 ). • Thrombosis has occurred in patients treated with LITFULO. Increased incidence of pulmonary embolism, venous and arterial thrombosis with another JAK inhibitor vs. TNF blockers. ( 5.5 ) • Increased risk of serious bacterial, fungal, viral and opportunistic infections leading to hospitalization or death, including tuberculosis (TB). Interrupt treatment if serious infection occurs until the infection is controlled. LITFULO should not be given to patients with active tuberculosis. Test for latent TB before and during therapy; treat latent TB prior to use. Monitor all patients for active TB during treatment, even patients with initial negative, latent TB test. ( 5.1 ) • Higher rate of all-cause mortality, including sudden cardiovascular death with another Janus kinase inhibitor (JAK) vs. TNF blockers in rheumatoid arthritis (RA) patients. LITFULO is not approved for use in RA patients. ( 5.2 ) • Malignancies have occurred in patients treated with LITFULO [see Warnings and Precautions (5.3) ] . Higher rate of lymphomas and lung cancers with another JAK inhibitor vs. TNF blockers in RA patients. ( 5.3 ) • Higher rate of MACE (defined as cardiovascular death, myocardial infarction, and stroke) with another JAK inhibitor vs. TNF blockers in RA patients. ( 5.4 ) • Thrombosis has occurred in patients treated with LITFULO. Increased incidence of pulmonary embolism, venous and arterial thrombosis with another JAK inhibitor vs. TNF blockers. ( 5.5 )

Common side effects

• Headache
• Diarrhea
• Acne
• Rash
• Urticaria
• Folliculitis
• Pyrexia
• Dermatitis atopic
• Dizziness
• Blood creatine phosphokinase increased
• Herpes zoster
• Red blood cell count decreased

Key clinical trials

• A 104-Week Study of Ritlecitinib Oral Capsules in Adults With Nonsegmental Vitiligo (Active and Stable) Tranquillo 2 (PHASE3)
• Combination Approach With Ritlecitinib and nbUVB Compared to Ritlecitinib Alone for Treating Vitiligo (PHASE2)
• A 52-Week Study of Ritlecitinib Oral Capsules in Adults and Adolescents With Nonsegmental Vitiligo (Active and Stable) Tranquillo (PHASE3)
• Long-Term PF-06651600 for the Treatment of Alopecia Areata (PHASE3)
• Characterization And Clinical Outcomes of AA Patients Treated With Ritlecitinib
• Utilization and Effectiveness of Ritlecitinib in a Real-World Population With Severe AA in the US
• Ritlecitinib (PF-06651600) in Participants With Chronic Spontaneous Urticaria (PHASE2)
• A 16-Week Study to Learn About the Study Medicine Called Ritlecitinib in Adults With Long Lasting Painful Red Skin Lumps, Known by the Medical Term, Hidradenitis Suppurativa, or HS. (PHASE2)

Patents

Primary sources

Every claim on this page is sourced from regulatory or scientific primary sources. See our editorial policy for full methodology.

Competitive intelligence

For the full competitive landscape — auto-detected comparators, recent regulatory actions across the set, upcoming PDUFA, patent timeline, sponsor landscape:

• Litfulo CI brief — competitive landscape report
• Litfulo updates RSS · CI watch RSS
• Pfizer portfolio CI