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Ritlecitinib
Clinical data
Trade namesLitfulo
Other namesPF-06651600
AHFS/Drugs.comMonograph
MedlinePlusa624015
License data
Pregnancy
category
Routes of
administration		By mouth
ATC code
Legal status
Legal status
Identifiers
  • 1-{(2S,5R)-2-methyl-5-[(7H-pyrrolo[2,3-d]pyrimidin-4-yl)amino]piperidin-1-yl}prop-2-en-1-one
CAS Number
PubChem CID
IUPHAR/BPS
DrugBank
ChemSpider
UNII
KEGG
ChEBI
ChEMBL
Chemical and physical data
FormulaC15H19N5O
Molar mass285.351 g·mol−1
3D model (JSmol)
  • C=CC(=O)N1C[C@H](Nc2ncnc3[nH]ccc23)CC[C@@H]1C
  • InChI=1S/C15H19N5O/c1-3-13(21)20-8-11(5-4-10(20)2)19-15-12-6-7-16-14(12)17-9-18-15/h3,6-7,9-11H,1,4-5,8H2,2H3,(H2,16,17,18,19)/t10-,11+/m0/s1
  • Key:CBRJPFGIXUFMTM-WDEREUQCSA-N
  • Key:YOZLVAFWYLSRRN-VZXYPILPSA-N

Ritlecitinib, sold under the brand name Litfulo, is a medication used for the treatment of severe alopecia areata (hair loss).[6] Ritlecitinib is a kinase inhibitor which inhibits Janus kinase 3 and tyrosine kinase.[6][9][10]

The most common side effects include headache, diarrhea, acne, rashes, eczema, fever, mouth ulcers, dizziness, shingles rash, and abnormal findings in some laboratory test results.[11]

Ritlecitinib was approved for medical use in the United States in June 2023,[6][11][12] in the European Union in September 2023,[7] and in Canada in November 2023.[4]

Medical uses

[edit]

Ritlecitinib is indicated for the treatment of severe alopecia areata for individuals twelve years of age and older.[6][7]

History

[edit]

The US Food and Drug Administration (FDA) approved ritlecitinib based on evidence from a clinical trial of 718 participants with severe alopecia areata.[11] The efficacy and safety of ritlecitinib were evaluated in a randomized, double-blind, placebo controlled trial in 718 participants twelve years of age and older with alopecia areata with ≥50% scalp hair loss, including alopecia totalis and alopecia universalis.[11] The trial randomized 130 participants to ritlecitinib 50 mg once daily, 131 participants to placebo, and 457 participants to other ritlecitinib dosing regimens.[11] The safety evaluation was also supported by two placebo-controlled trials in which 80 participants were randomized to ritlecitinib 200 mg once daily for four weeks followed by 50 mg once daily and 82 participants were randomized to placebo.[11] The trial was conducted at 128 sites in 18 countries in Argentina, Australia, Canada, Chile, China, Colombia, Czech Republic, Germany, Hungary, Japan, Republic of Korea, Mexico, Poland, Russian Federation, Spain, Taiwan, the United Kingdom, and the United States.[11]

Society and culture

[edit]
[edit]

In 2023, ritlecitinib was approved for medical use in the United States,[6][11] in the European Union,[7] and in Canada.[4]

Economics

[edit]

The annual list price of ritlecitinib is US$49,000.[13]

References

[edit]

Further reading

[edit]
[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Ritlecitinib

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from Grokipedia
Ritlecitinib, sold under the brand name Litfulo, is an oral kinase inhibitor medication approved for the treatment of severe alopecia areata in adults and adolescents aged 12 years and older.[1] Developed by Pfizer, it received its first approval from the U.S. Food and Drug Administration (FDA) on June 23, 2023, and has since been approved in several other jurisdictions including the European Union, Canada, Japan, the United Kingdom, Switzerland, Singapore, Italy, and Australia as of 2025, marking it as the second JAK inhibitor approved for this indication following baricitinib.[2][3][4][5] Ritlecitinib is a covalent, irreversible inhibitor that selectively targets Janus kinase 3 (JAK3) and members of the TEC family of kinases (TEC, BTK, ITK, RLK, and BMX) by blocking ATP binding in their active sites.[1] This mechanism disrupts cytokine signaling pathways, particularly those involving JAK3, which is essential for immune cell function, thereby reducing the autoimmune attack on hair follicles characteristic of alopecia areata.[3] In clinical settings, ritlecitinib inhibits the cytolytic activity and interferon-γ production in natural killer cells and CD8+ T cells, contributing to hair regrowth.[3] The drug is administered as 50 mg capsules taken once daily, with or without food, and reaches steady-state plasma concentrations within days, exhibiting a short half-life of 1.3 to 2.3 hours.[1] Approval was based on the phase 2b/3 ALLEGRO trial, which demonstrated significant scalp hair coverage improvements in patients with severe alopecia areata after 24 weeks of treatment compared to placebo.[2] Common adverse effects include diarrhea, headache, dizziness, and acne, while serious risks involve infections, malignancies, major adverse cardiovascular events, and thrombosis, necessitating screening for tuberculosis and viral hepatitis prior to initiation.[1] Ritlecitinib is not recommended for use with other potent immunosuppressants or in patients with active infections.[1]

Pharmacology

Mechanism of action

Ritlecitinib is a small-molecule kinase inhibitor that selectively and irreversibly targets Janus kinase 3 (JAK3) and members of the TEC family of non-receptor tyrosine kinases, including BTK, ITK, TEC, TXK, and BMX.[3] In biochemical assays, it demonstrates potent inhibition of JAK3 with an IC50 of 33.1 nM, while exhibiting much lower affinity for other Janus kinases such as JAK1, JAK2, and TYK2 (IC50 > 10,000 nM).[3] This selectivity profile minimizes off-target effects, particularly on JAK2-mediated hematopoiesis, while effectively modulating immune signaling. For TEC family kinases, IC50 values (at 1 mM ATP) range from 194 nM (TXK) to 8,510 nM (ITK), with TEC at 592 nM, BMX at 606 nM, and BTK at 608 nM, supporting its dual inhibitory activity.[6] The drug exerts its effects through covalent binding to a conserved cysteine residue (Cys909 in JAK3) within the ATP-binding pocket of the kinase domain, forming a stable adduct that leads to irreversible inhibition.[7] This mechanism disrupts the kinase activity of JAK3 and TEC kinases, preventing autophosphorylation and downstream signal transduction. By targeting JAK3, ritlecitinib blocks the JAK-STAT signaling pathway, specifically inhibiting the phosphorylation and activation of signal transducer and activator of transcription (STAT) proteins in response to γ-chain cytokines such as IL-2, IL-7, IL-9, IL-15, and IL-21.[6] In immune cells, this inhibition reduces cytokine-induced proliferation and activation of T lymphocytes and natural killer (NK) cells, key players in T-cell mediated inflammatory responses.[3] The preferential inhibition of JAK3 over other family members enhances its therapeutic index by sparing broader cytokine signaling pathways, such as those involving JAK1/2 heterodimers responsible for erythropoiesis and thrombopoiesis.[7] Additionally, suppression of TEC kinases like ITK further attenuates T-cell signaling and cytotoxic functions, contributing to dampened autoimmune inflammation without broadly compromising innate immunity.[6] This targeted blockade of the JAK-STAT pathway is particularly relevant for conditions driven by dysregulated T-cell activity.

Pharmacokinetics

Ritlecitinib is rapidly absorbed after oral administration, achieving peak plasma concentrations (Tmax) within approximately 1 hour, with an absolute oral bioavailability of about 64%. A high-fat meal reduces the maximum plasma concentration (Cmax) by roughly 32% while increasing the area under the curve (AUC) by 11%; however, these changes are not considered clinically significant, and no dosage adjustments are recommended based on food intake.[1][8] The apparent volume of distribution at steady state is approximately 74 L following intravenous administration, suggesting moderate distribution into extravascular spaces. Ritlecitinib exhibits low plasma protein binding of about 14%, primarily to albumin, with a blood-to-plasma concentration ratio of 1.62.[8] Metabolism of ritlecitinib is mediated by multiple pathways, including glutathione S-transferase (GST) enzymes (such as GSTA1, GSTM1, and others) and cytochrome P450 (CYP) enzymes (notably CYP3A4 at approximately 22% and CYP2C8 at 15%), with no single route responsible for more than 25% of total clearance. The primary circulating metabolite is an inactive cysteine conjugate (M2), accounting for about 16.5% of exposure.[1][8] Elimination occurs predominantly via metabolism, with approximately 66% of the administered dose recovered in urine and 20% in feces over 7 days; less than 5% is excreted unchanged in urine. The terminal elimination half-life ranges from 1.3 to 2.3 hours, and steady-state plasma concentrations are attained by day 4 with once-daily dosing. Systemic clearance is estimated at 43.7 L/h.[1][8][9] No dosage adjustments are required for renal impairment, including severe cases (eGFR <30 mL/min/1.73 m²), as exposure increases (AUC24 by ~55%) are not deemed clinically meaningful. For hepatic impairment, no changes are needed in mild (Child-Pugh A) or moderate (Child-Pugh B) cases, where AUC24 rises by ~18.5%, but ritlecitinib is not recommended for severe hepatic impairment (Child-Pugh C). Pharmacokinetic parameters are similar across age (12–73 years), sex, body weight, and race, with no clinically relevant differences in adolescents compared to adults.[1][8]

Clinical use

Indications

Ritlecitinib is approved by the U.S. Food and Drug Administration (FDA) for the treatment of severe alopecia areata in adults and adolescents aged 12 years and older.[1] It has also been authorized by the European Medicines Agency (EMA) for the same indication in adults and adolescents from 12 years of age across the European Union member states, Iceland, Liechtenstein, and Norway, as well as by the Medicines and Healthcare products Regulatory Agency (MHRA) in the United Kingdom (November 2023) and regulatory bodies in several other countries, including Canada (November 2023), Japan (2024), and China (2024).[10][11][12] This indication targets patients with extensive scalp hair loss due to severe alopecia areata, typically defined as a Severity of Alopecia Tool (SALT) score of 50 or greater at baseline, indicating at least 50% scalp involvement.[1][13] It is particularly suited for individuals whose condition has shown inadequate response to prior therapies, such as topical or systemic corticosteroids, and is not recommended for mild alopecia areata (SALT score <50) or other hair loss disorders like androgenetic alopecia.[13][1] Efficacy for this use is demonstrated by the phase 2b/3 ALLEGRO trial (NCT03732807), where 23% of patients receiving ritlecitinib 50 mg once daily achieved ≥80% scalp hair coverage (SALT score ≤20) at week 24, compared to 1.6% on placebo.[14] Limitations of the approval include its lack of establishment for safety and efficacy in children under 12 years and its focus on scalp hair regrowth (as measured by the SALT score), though the indication includes patients with alopecia totalis or universalis if scalp involvement is ≥50%.[1]

Administration and dosage

Ritlecitinib is administered orally as capsules at a recommended dosage of 50 mg once daily, with or without food. The capsules should be swallowed whole and not crushed, split, or chewed. No loading dose is required, and treatment is typically initiated directly at this dose following appropriate baseline evaluations. If a dose is missed, it should be taken as soon as possible unless less than 8 hours remain before the next scheduled dose, in which case the missed dose is skipped and the regular schedule resumed.[1] Treatment duration is generally long-term for ongoing management of severe alopecia areata, with efficacy often assessed at 24 weeks; periodic reassessment is recommended to evaluate response and need for continuation, typically every 6-12 months. No dose titration or tapering is necessary upon discontinuation, though regrown hair may be lost upon stopping therapy.[1] Dosage adjustments are not required for patients with mild (Child-Pugh A) or moderate (Child-Pugh B) hepatic impairment, but ritlecitinib is not recommended in those with severe (Child-Pugh C) hepatic impairment due to limited data. For hematologic effects, interrupt dosing if absolute lymphocyte count (ALC) falls below 500 cells/mm³ or platelet count below 100,000/mm³, resuming at 50 mg once levels recover; permanent discontinuation is advised if platelets drop below 50,000/mm³ or if severe infection or malignancy develops. Dosage interruption or discontinuation may also be needed for other adverse events such as serious infections.[1] Prior to initiation, baseline assessments include tuberculosis evaluation, viral hepatitis screening, complete blood count (with ALC ≥500 cells/mm³ and platelets ≥100,000/mm³), liver function tests, and lipid panel; immunizations should be updated per current guidelines. Ongoing monitoring involves ALC and platelet counts at 4 weeks post-initiation and routinely thereafter, liver enzymes as clinically indicated, and lipids approximately 8-12 weeks after starting and per hyperlipidemia management guidelines.[1]

Safety profile

Adverse effects

Ritlecitinib is associated with a range of adverse effects, primarily mild to moderate in severity, as observed in clinical trials and post-marketing data. The most common adverse reactions, occurring at an incidence of ≥1% in patients treated for up to 24 weeks, include headache (10.8%), diarrhea (10.0%), acne (6.2%), rash (5.4%), urticaria (4.6%), folliculitis (3.1%), and pyrexia (3.1%).[1] These effects are generally self-limiting and do not lead to treatment discontinuation in most cases.[1] Serious adverse effects, though less frequent, include an increased risk of infections such as herpes zoster (incidence rate of 1.17 per 100 patient-years), which may require medical intervention.[1] Long-term data indicate a malignancy incidence of 0.37 per 100 patient-years (excluding non-melanoma skin cancer), consistent with class effects of Janus kinase (JAK) inhibitors.[1] Cardiovascular events, including thrombosis, carry a heightened risk as per JAK inhibitor warnings, with thromboembolic events reported at rates of 0.06 per 100 patient-years for pulmonary embolism.[1] Severe hematologic abnormalities, such as lymphopenia (absolute lymphocyte count <500 cells/mm³), occur in <0.1% of patients.[1] Long-term clinical trial data from the ALLEGRO-LT study (published 2025) indicate that 86.1% of patients experienced treatment-emergent adverse events, most of which were mild or moderate in severity, aligning with clinical trial observations.[15] Rare case reports have described neuropathic musculoskeletal pain emerging during therapy, though causality remains unestablished.[16] Management of adverse effects involves dose interruption for severe infections and adherence to vaccination recommendations prior to initiating treatment to mitigate infection risks.[1]

Contraindications and precautions

Ritlecitinib is contraindicated in patients with known hypersensitivity to the drug or any of its excipients.[1][8] In regions following European Medicines Agency guidelines, additional absolute contraindications include active serious infections such as tuberculosis, severe hepatic impairment (Child-Pugh class C), pregnancy, and breastfeeding.[8] Relative precautions are advised for patients with a history of malignancy, as Janus kinase inhibitors like ritlecitinib may increase the risk of lymphomas and other cancers; periodic skin examinations are recommended in such cases.[1][8] Caution is also warranted in individuals with cardiovascular disease due to an elevated risk of major adverse cardiovascular events (MACE), such as myocardial infarction and stroke, and thromboembolic events like pulmonary embolism; treatment should be interrupted if such events occur.[1][8] Elderly patients over 65 years require special monitoring owing to a higher susceptibility to infections.[1][8] For pregnancy, while no formal category is assigned, animal studies indicate potential fetal harm at exposures greater than those in humans, and effective contraception is recommended during treatment and for at least one week afterward; pregnancies should be reported to the manufacturer.[1][8] Prior to initiating ritlecitinib, patients should be screened for latent tuberculosis (TB) and treated if positive; therapy is not recommended during active infections, and treatment should be interrupted for serious or opportunistic infections.[1][8] Live vaccines should be avoided during treatment and for several weeks prior, with all immunizations updated according to guidelines before starting therapy.[1][8] Laboratory monitoring includes baseline and periodic assessments of absolute lymphocyte count (ALC) and platelet counts, with interruption or discontinuation if ALC falls below 500 cells/mm³ or platelets below 50,000/mm³.[1][8] In special populations, no dose adjustment is required for mild to moderate renal impairment, and the drug appears safe based on pharmacokinetic data, though it has not been studied in end-stage renal disease or renal transplant patients.[1][8] For hepatic impairment, no adjustment is needed in mild or moderate cases, but severe impairment contraindicates use per EMA guidelines.[1][8] Lactation data are limited, with the drug present in animal milk; breastfeeding is not recommended during treatment and for at least 14 hours after the last dose.[1][8]

Interactions

Drug interactions

Ritlecitinib is primarily metabolized by CYP3A, resulting in minimal pharmacokinetic interactions with CYP3A inhibitors. Coadministration with itraconazole, a strong CYP3A inhibitor, increases ritlecitinib's AUC by approximately 15%, which is not considered clinically significant, and no dose adjustment is required. Similarly, exposure changes with other strong CYP3A inhibitors, such as ketoconazole, are expected to be weak and do not necessitate dosage modifications.[8][17] In contrast, strong CYP3A inducers like rifampin decrease ritlecitinib exposure, reducing its AUC by about 44%, which may compromise efficacy. The FDA prescribing information advises against coadministration with strong CYP3A inducers due to this potential loss of therapeutic effect, while EMA guidance states no dose adjustment is needed, as the change is not considered clinically significant. A 2025 study confirms that such reductions are not clinically significant.[1][8][17] As a moderate inhibitor of CYP3A, ritlecitinib can increase exposure to CYP3A substrates, such as midazolam (AUC increased ~2.7-fold and Cmax ~1.8-fold), potentially elevating the risk of adverse reactions. Dosage adjustments and monitoring are recommended for sensitive CYP3A substrates like certain statins (e.g., simvastatin), colchicine, everolimus, or tacrolimus when used concomitantly. Ritlecitinib also moderately inhibits CYP1A2, raising AUC of substrates like caffeine (~2.7-fold) or theophylline, warranting caution and possible dose reductions for narrow therapeutic index agents. No clinically significant interactions occur with CYP2B6, CYP2C substrates, or transporters like OATP1B1 and BCRP.[1][8] Pharmacodynamic interactions arise with other immunosuppressants due to additive risks of serious infections, malignancies, and other complications. Concomitant use with other JAK inhibitors, biologic disease-modifying antirheumatic drugs (DMARDs), or potent immunosuppressants such as azathioprine, cyclosporine is not recommended, as it may heighten immunosuppression without added benefit. Caution is advised with moderate immunosuppressants like methotrexate, with close monitoring for infections.[1][18][19]

Food and other interactions

Ritlecitinib can be taken with or without food, as food does not have a clinically significant impact on its systemic exposure. Coadministration with a high-fat meal decreases the maximum plasma concentration (Cmax) by approximately 32% and increases the area under the curve (AUC) by 11%.[1] However, ritlecitinib may increase blood levels of caffeine from foods and beverages such as coffee, tea, or energy drinks, potentially exacerbating side effects like headache, dizziness, insomnia, or rapid heart rate. Patients should limit caffeine intake and monitor for these effects.[19][20] No direct pharmacokinetic interaction exists between ritlecitinib and alcohol, but both can cause overlapping side effects including headache and dizziness, which may worsen when combined. Excessive alcohol use may further increase the risk of infections due to its effects on immune function alongside ritlecitinib's immunosuppression. Moderate alcohol consumption is advised.[19][20] Current or past smoking increases the risk of malignancies, including lung cancer, and major adverse cardiovascular events (MACE) in patients taking JAK inhibitors like ritlecitinib. Smoking cessation is recommended to mitigate these risks.[1] St. John's wort, an herbal supplement, induces CYP3A enzymes and may decrease ritlecitinib exposure, reducing its efficacy; it should be avoided during treatment. Other herbal supplements lack specific interaction data, but patients should consult healthcare providers before use.[19][20] Live vaccines should be avoided during ritlecitinib treatment or shortly prior to initiation, as the drug may blunt immune responses and increase infection risk. Prior to starting therapy, patients should update all immunizations according to current guidelines.[1][19] To reduce the risk of non-melanoma skin cancers associated with JAK inhibitors, patients should limit exposure to sunlight and ultraviolet light by using broad-spectrum sunscreen, wearing protective clothing, and avoiding tanning beds. Dermatological monitoring is suggested for any skin changes.[1][21][22]

Research

Clinical trials

The ALLEGRO phase 2a trial (NCT02974868) was a dose-ranging study conducted from 2016 to 2018 involving 142 adults with severe alopecia areata, evaluating ritlecitinib and brepocitinib to assess initial efficacy for hair regrowth. In this randomized, double-blind, placebo-controlled study, the 200/50 mg dose (200 mg loading for 4 weeks followed by 50 mg once daily) showed promising results, with approximately 36% achieving ≥90% improvement in SALT score at 24 weeks, compared to placebo.[23][24] The pivotal phase 2b/3 ALLEGRO trial (NCT03732807) enrolled 718 participants, including adults and adolescents aged 12 years and older with ≥50% scalp hair loss due to alopecia areata. This randomized, double-blind, placebo-controlled study assessed ritlecitinib 50 mg and 30 mg once daily (with or without a 200 mg loading dose for the first 4 weeks), meeting the primary endpoint of proportion achieving SALT ≤20 at 24 weeks. Specifically, 23% of patients on 50 mg achieved ≥80% scalp hair coverage (SALT ≤20), compared to 1.6% on placebo. In the long-term extension up to 104 weeks, sustained response was observed in approximately 40% of responders, with continued hair regrowth maintenance in those continuing treatment. The phase 2a trial provided initial evidence, while this phase 2b/3 trial served as pivotal for approval, with long-term data from ALLEGRO-LT (NCT04006457).[25][6][26] Safety data from the ALLEGRO trials showed that approximately 2.6% of participants discontinued due to adverse events, primarily mild to moderate in severity. Adverse events occurred in 85% of ritlecitinib-treated patients, with infections reported at similar rates to placebo (detailed rates per FDA: 13.5 per 100 patient-years for 50 mg), and no new safety signals emerging beyond known class effects of Janus kinase inhibitors.[6][25] Subgroup analyses from the phase 2b/3 trials confirmed efficacy in the pediatric population aged 12-17 years, with similar proportions achieving SALT ≤20 at 24 weeks compared to adults, supporting the inclusion of adolescents in the approved indication.[27][25]

Ongoing and future studies

Recent real-world studies conducted in 2024 and 2025 have provided insights into the practical effectiveness of ritlecitinib beyond controlled trial settings. A multicenter retrospective analysis in China involving a cohort of 100 patients with alopecia areata demonstrated a 60% response rate at 12 weeks, highlighting its efficacy in diverse clinical populations. Similarly, a US multicenter study reported 70% patient satisfaction with treatment outcomes, accompanied by predominantly mild adverse effects, underscoring the drug's tolerability in everyday use.[28][29] Data from the phase 3 long-term extension study, with 2025 interim results, indicate sustained benefits and a manageable safety profile over extended periods. Among participants, 86% experienced mild adverse events, while serious events occurred in only 2% of cases. Notably, sustained hair regrowth was observed in 50% of patients at the two-year mark, building on baseline trial responses without introducing new safety concerns.[15] Several ongoing trials are exploring ritlecitinib's potential in additional contexts as of late 2025. The trial NCT06873945, spanning 2024 to 2026, is evaluating the comparative efficacy and safety of 25 mg versus 50 mg doses specifically in adolescents aged 12 and older with alopecia areata. Exploratory phase 2 investigations are also assessing its application in vitiligo and atopic dermatitis, aiming to expand indications for this JAK3/TEC inhibitor.[30][31] Future research directions emphasize comparative effectiveness and long-term safety surveillance. Studies are planned to directly compare ritlecitinib against baricitinib, given their similar efficacy profiles in indirect analyses for alopecia areata management. Additionally, ongoing monitoring initiatives focus on long-term malignancy risks, informed by pooled safety data showing low incidence rates in extended follow-up.[32][33]

History

Development

Ritlecitinib, developed by Pfizer under the investigational code name PF-06651600, emerged in the 2010s as a selective covalent inhibitor of Janus kinase 3 (JAK3) through targeted medicinal chemistry design aimed at achieving isoform-specific inhibition within the JAK family. This approach leveraged structural insights into JAK3's active site, particularly a unique cysteine residue enabling irreversible binding, to differentiate it from pan-JAK inhibitors like tofacitinib.[34] The compound was optimized for oral bioavailability and potency against JAK3-dependent signaling pathways involved in immune responses.[35] Preclinical evaluation confirmed PF-06651600's high selectivity for JAK3 and TEC family kinases (such as BTK and ITK) over other JAK isoforms and the broader kinome, as demonstrated by enzyme inhibition assays and cellular signaling studies.[36] In animal models of autoimmune conditions, including a graft-induced mouse model of alopecia areata, the inhibitor prevented hair loss onset and promoted regrowth by suppressing JAK3-mediated cytokine signaling in T cells. These findings highlighted its potential in T-cell driven inflammatory diseases while supporting an acceptable safety margin for clinical advancement.[6] Early clinical development began with phase 1 trials in healthy volunteers, initiated in late 2014 and completed by 2017, which assessed single and multiple doses up to 800 mg to characterize pharmacokinetics, safety, and tolerability.[37] These studies established a favorable profile, with rapid absorption, dose-proportional exposure, and selection of 200 mg once-daily dosing for subsequent phases based on pharmacodynamic markers of JAK3 inhibition.[36] Building on this, a phase 2a trial in patients with rheumatoid arthritis and inadequate response to methotrexate, started in 2017, demonstrated significant improvements in disease activity scores, prompting broader exploration of its anti-inflammatory effects. Signals of hair regrowth observed in early autoimmune disease studies, consistent with JAK3's role in alopecia areata pathogenesis, shifted focus toward dermatological applications.[38] Key milestones included the U.S. FDA's granting of Breakthrough Therapy Designation in September 2018 for severe alopecia areata, recognizing preliminary evidence of substantial improvement over available therapies.[39] This accelerated development, culminating in the New Drug Application submission to the FDA on June 24, 2022, supported by integrated data from earlier phases.[40]

Regulatory milestones

Ritlecitinib, marketed as Litfulo, received its first regulatory approval from the US Food and Drug Administration (FDA) on June 23, 2023, for severe alopecia areata in patients 12 years and older, based on efficacy and safety data from the phase 2b/3 ALLEGRO trials demonstrating significant scalp hair coverage improvements.[41][1] This was followed shortly by approval from Japan's Ministry of Health, Labour and Welfare on June 26, 2023, for the treatment of intractable alopecia areata involving widespread hair loss in adults and adolescents aged 12 years and older.[3] In Europe, the European Medicines Agency (EMA) granted marketing authorization on September 15, 2023, under the centralized procedure, valid across all 27 EU member states plus Iceland, Liechtenstein, and Norway, for the same indication in adults and adolescents aged 12 years and older.[10] The European Commission confirmed this approval on September 19, 2023.[4] Health Canada approved ritlecitinib on December 4, 2023, for severe alopecia areata in patients 12 years and older.[42] Additional approvals followed, including in China by the National Medical Products Administration on October 19, 2023, and in Australia by the Therapeutic Goods Administration on July 30, 2024, and Singapore by the Health Sciences Authority in July 2024.[43][44][45] By 2025, ritlecitinib had been approved in over 30 countries worldwide, including the UK (November 2023) and others in Asia, Europe, and North America, with no major new indications or expansions beyond the initial alopecia areata use.[5][46] Long-term safety data from extension studies have been incorporated into post-approval pharmacovigilance, emphasizing warnings for serious infections, malignancies, and cardiovascular events consistent with the JAK inhibitor class boxed warnings.[1] Pediatric use remains limited to those 12 years and older, with confirmed extensions in post-approval pharmacovigilance plans but no approvals for younger children as of 2025.[47][48]

Society and culture

Legal status

In the United States, ritlecitinib (marketed as Litfulo) is approved by the Food and Administration (FDA) as a prescription-only medication for the treatment of severe alopecia areata in adults and adolescents aged 12 years and older, with no controlled substance scheduling under the Controlled Substances Act.[49] It requires monitoring for infections as outlined in its prescribing information, including warnings for serious infections, malignancies, and cardiovascular events, though it is not subject to a formal Risk Evaluation and Mitigation Strategy (REMS) program.[1] Coverage is available under Medicare Part D for eligible beneficiaries as a specialty-tier prescription drug. In the European Union, ritlecitinib is authorized through the centralized procedure by the European Medicines Agency (EMA) and the European Commission for use in all member states as a restricted medical prescription medication, indicated for severe alopecia areata in adults and adolescents aged 12 years and older.[8] It is dispensed via pharmacies but requires initiation and supervision by specialists familiar with managing immunosuppressive therapies, with no controlled substance classification.[50] In Canada, ritlecitinib (Litfulo) is classified as a prescription drug by Health Canada, approved for severe alopecia areata in adults and adolescents aged 12 years and older, with no status as a controlled substance under the Controlled Drugs and Substances Act.[51] It is eligible for reimbursement through public formularies such as those under provincial drug plans, subject to prior authorization based on clinical criteria including disease severity and prior treatment failure. Ritlecitinib has also received approval in other countries, including Japan in June 2023 for intractable cases of alopecia areata involving widespread hair loss,[3] the United Kingdom in November 2023 by the Medicines and Healthcare products Regulatory Agency (MHRA),[52] and Australia in June 2025 by the Therapeutic Goods Administration (TGA).[53] Globally, ritlecitinib holds no controlled substance status in major regulatory frameworks, but access is restricted in many low-income countries primarily due to high costs and limited regulatory approvals or importation pathways, often confining availability to clinical trials or private import under compassionate use.

Commercial aspects

Ritlecitinib is marketed under the brand name Litfulo by Pfizer, with no generic versions available due to patent protection extending until approximately 2035.[54] Key intellectual property includes U.S. Patent No. 9,617,258 covering the compound, which expires on December 3, 2034.[18] Additionally, pediatric exclusivity provides further market protection until mid-2027, delaying potential generic challenges following the drug's 2023 approval.[55] In the United States, the annual list price for Litfulo is approximately $49,000 as of 2023. Pfizer offers patient assistance programs, including copay savings cards, that can reduce out-of-pocket costs to as little as $0 for eligible commercially insured patients, with maximum annual benefits ranging from $4,000 to $15,000 depending on the plan.[56] For uninsured or underinsured individuals, Pfizer RxPathways provides Litfulo at no cost to those meeting income criteria, typically up to 400% of the federal poverty level.[57] Litfulo is positioned as the second Janus kinase (JAK) inhibitor approved for severe alopecia areata, following Eli Lilly's Olumiant (baricitinib), targeting adults and adolescents aged 12 and older in a growing dermatology market.[58] Developed by Pfizer, it entered the market amid increasing demand for targeted therapies in autoimmune hair loss conditions.[2] Competition from generics or biosimilars remains unlikely in the near term, given the robust patent portfolio and recent pediatric indications that extend exclusivity.[55]

References

  1. [PDF] Litfulo - accessdata.fda.gov
  2. FDA Approves Pfizer's LITFULO™ (Ritlecitinib) for Adults and ...
  3. Ritlecitinib: First Approval - PMC - NIH
  4. [PDF] 215830Orig1s000 MULTI-DISCIPLINE REVIEW Summary Review ...
  5. Ritlecitinib in severe alopecia areata: a profile of its use
  6. [PDF] Litfulo, INN-ritlecitinib - European Medicines Agency
  7. The Pharmacokinetics, Metabolism, and Clearance Mechanisms of ...
  8. Litfulo | European Medicines Agency (EMA)
  9. [PDF] RITLECITINIB FOR ALOPECIA AREATA
  10. Long-term safety and efficacy of ritlecitinib in adults and adolescents ...
  11. [PDF] A Case Report - Kansas City University's Digital Repository
  12. Drug–drug interaction profile of ritlecitinib as perpetrator and victim ...
  13. Ritlecitinib: Uses, Interactions, Mechanism of Action | DrugBank Online
  14. Litfulo Interactions: Alcohol, Medications, and Others - Healthline
  15. Litfulo interactions: Other drugs, alcohol, and more
  16. https://litfulo.pfizerpro.com/api/vc/en/content/material/c7cf41b4-6254-4662-bb25-66fe80c92514/LITFULOritlecitinib_BoxedWarning_SafetyInfo_PrescribingInfo_PP-CIB-USA-0746.pdf
  17. https://www.goodrx.com/litfulo/what-is
  18. https://www.thelancet.com/article/S0140-6736(23
  19. Efficacy and safety of ritlecitinib in adolescents with alopecia areata
  20. Ritlecitinib in alopecia areata: A multicenter retrospective real-world ...
  21. Real-World Ritlecitinib Treatment of Severe Alopecia Areata (AA) in ...
  22. NCT06873945 | A Study of 2 Doses of Ritlecitinib in People 12 ...
  23. Efficacy and safety of oral ritlecitinib for the treatment of active ...
  24. Systematic review and indirect treatment comparisons of ritlecitinib ...
  25. A Patient Preference-Weighted Quantitative Benefit-Risk Analysis of ...
  26. Ritlecitinib (LITFULO) - Drug Hunter
  27. PF-06651600, a Dual JAK3/TEC Family Kinase Inhibitor - PubMed
  28. Efficacy and Safety of PF‐06651600 (Ritlecitinib), a Novel JAK3/TEC ...
  29. https://clinicaltrials.gov/study/NCT02309827
  30. Efficacy and Safety of PF-06651600 (Ritlecitinib), a Novel JAK3/TEC ...
  31. Pfizer Receives Breakthrough Therapy Designation from FDA for PF ...
  32. [PDF] APPLICATION NUMBER: - 215830Orig1s000 OTHER REVIEW(S)
  33. Ritlecitinib: First Approval - PubMed
  34. European Commission Approves Pfizer's LITFULO™ for ...
  35. LITFULO™ Receives Health Canada Approval, Becoming the First ...
  36. Ritlecitinib Tosylate Capsules Approved for Marketing
  37. Litfulo (ritlecitinib) | Therapeutic Goods Administration (TGA)
  38. [PDF] Australian public assessment report for LITFULO
  39. A Phase 1, Open‐Label Study of the Pharmacokinetics of Ritlecitinib ...
  40. [PDF] Litfulo Pediatric Postmarketing Pharmacovigilance Review - FDA
  41. EMEA-002451-PIP01-18-M02 - paediatric investigation plan
  42. [PDF] Litfulo (ritlecitinib) - accessdata.fda.gov
  43. [PDF] litfulo-epar-public-assessment-report_en.pdf
  44. Regulatory Decision Summary for Litfulo
  45. Generic Litfulo Availability - Drugs.com
  46. https://www.drugpatentwatch.com/p/tradename/LITFULO
  47. Savings & Support Overview | LITFULO® (ritlecitinib) | Safety Info
  48. For Patients - Pfizer RxPathways
  49. Pfizer's Newly Approved Litfulo to Take on Eli Lilly's Olumiant in ...
  50. Alopecia Market Size, Share & Trends Report, 2024 – 2032
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