Ritlecitinib side effects: what 1,862 FDA adverse event reports show

Ritlecitinib · Litfulo · 18 reaction terms · 351 drug–reaction co-reports · data 2026-09-14

Drug class

Kinase inhibitor

FDA label, Indications wording

Brand names

Litfulo

openFDA label

Who reports

1,862 reports · 19% serious · 3 with death outcome · 65% female

openFDA FAERS counts, all years, deduplication not applied

Used for

LITFULO is a kinase inhibitor indicated for the treatment of severe alopecia areata in adults and adolescents 12 years and older. Limitations of Use : Not recommended for use in combination with other JAK inhibitors, biologic immunomodulators, cyclosporine or other potent immunosuppressants.

FDA label, Indications and Usage

What it is

LITFULO (ritlecitinib) capsules are formulated with ritlecitinib tosylate, a kinase inhibitor. Ritlecitinib tosylate is a white to off white to pale pink solid which is freely soluble in water.

FDA label, Description section

Boxed 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.

FDA label

How to read this page. FAERS is a spontaneous-reporting system: counts are not incidence rates and a signal is not proof of causation. Each reaction below is run through an automated screen — is the term in the FDA label (known), in the indications (the disease being treated), an administrative/coding term, or none of these (unlabeled)? That screen is mechanical text matching, not a causality assessment. The 30 hand-written Bradford Hill assessments are on the causality assessment page. Not medical advice.

Causality screen of the 15 strongest signals

Labeled — boxed warning 1Labeled adverse reaction 3Reporting / coding artifact 4Lab value / disease marker 1Not in label — unassessed 6

What the badges mean

Labeled — boxed warning The term (or its clinical synonym) appears in the FDA boxed warning: causality is regulator-recognised and considered serious.
Labeled adverse reaction The exact term appears in the label's warnings or adverse-reactions sections: a known, expected effect. The FAERS signal confirms the label rather than discovering anything.
Reporting / coding artifact An administrative, monitoring or exposure term (product issue, off-label use, 'test normal', overdose...). Not a biological reaction; a high PRR here reflects how reports are coded.
Lab value / disease marker A laboratory result, investigation or disease-activity marker (antibody positive, CRP abnormal, swollen joint count) not described in the label. These usually mirror the monitored disease or testing protocol rather than a drug effect; not screened further.
Not in label — unassessed Not found in the label text, not an artifact pattern. This is a genuine candidate for a formal causality assessment (Bradford Hill / WHO-UMC); it has NOT had one here.

Strongest disproportionality signals

Flagged terms (PRR ≥ 2, χ² ≥ 4, n ≥ 10), ranked by PRR; infinite PRRs (no comparator reports) excluded. The EBGM column is a second, shrinkage-based estimate (MGPS) with its 5th percentile EB05 and the BCPNN IC025; a pair flagged by PRR alone is marked PRR-only and should be read as fragile. The strata column recomputes the PRR on serious reports only and flags pairs whose reports are unusually skewed by sex or come mostly from consumers rather than clinicians. 3 further terms are in the interactive explorer. Reaction links open the term's cross-drug page.

Show: hide coding/lab/outcome terms hide indication terms unlabeled only hide PRR-only

Reaction	Reports	PRR 95% CI · ROR · χ²/p	EBGM EB05 · IC025	Label screen	Serious-only & strata	Trial cross-check
Therapeutic product effect incomplete	134	21.4 18.2–25.2ROR 23.0 · χ² 2,587 / p <1e-300	21.3 EB05 18.4 · IC025 +4.0 3/3 methods agree	Reporting / coding artifact	serious PRR 1.8	no trial data cached
Blood creatine phosphokinase increased	33	12.7 9.1–17.8ROR 12.9 · χ² 345 / p 3e-77	12.3 EB05 8.9 · IC025 +2.9 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 17.9 · 91% clinician	no trial data cached
Hair colour changes	9	8.1 4.2–15.5ROR 8.1 · χ² 49 / p 1e-12	6.1 EB05 3.3 · IC025 +1.4 3/3 methods agree	Not in label — unassessed	–	no trial data cached
Folliculitis	7	7.6 3.6–16.0ROR 7.7 · χ² 34 / p 3e-9	5.5 EB05 2.8 · IC025 +1.1 3/3 methods agree	Labeled adverse reaction exact term	–	no trial data cached
Quality of life decreased	9	7.5 3.9–14.5ROR 7.6 · χ² 45 / p 1e-11	5.8 EB05 3.2 · IC025 +1.3 3/3 methods agree	Not in label — unassessed	serious PRR 6.1	no trial data cached
Tuberculosis	8	7.0 3.5–14.0ROR 7.0 · χ² 35 / p 1e-9	5.3 EB05 2.8 · IC025 +1.2 3/3 methods agree	Labeled — boxed warning exact term	serious PRR 21.3	no trial data cached
Therapeutic product effect decreased	26	6.6 4.5–9.7ROR 6.7 · χ² 118 / p 8e-28	6.0 EB05 4.3 · IC025 +1.9 3/3 methods agree	Reporting / coding artifact	–	no trial data cached
Acne	43	6.4 4.7–8.5ROR 6.5 · χ² 189 / p 2e-43	6.0 EB05 4.6 · IC025 +2.1 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 2.2	no trial data cached
Product prescribing error	13	6.2 3.6–10.6ROR 6.2 · χ² 51 / p 4e-13	5.2 EB05 3.2 · IC025 +1.4 3/3 methods agree	Reporting / coding artifact	serious PRR 8.9	no trial data cached
Madarosis	6	5.8 2.6–12.8ROR 5.8 · χ² 19 / p 6e-6	4.2 EB05 2.1 · IC025 +0.7 3/3 methods agree	Not in label — unassessed	–	no trial data cached
Blood triglycerides increased	9	5.7 3.0–11.0ROR 5.7 · χ² 30 / p 2e-8	4.5 EB05 2.6 · IC025 +1.1 3/3 methods agree	Lab value / disease marker	serious PRR 8.9	no trial data cached
Lymphopenia	7	5.6 2.7–11.7ROR 5.6 · χ² 22 / p 1e-6	4.3 EB05 2.2 · IC025 +0.8 3/3 methods agree	Not in label — unassessed	serious PRR 10.3	no trial data cached
Impaired quality of life	7	5.5 2.6–11.5ROR 5.5 · χ² 21 / p 2e-6	4.2 EB05 2.2 · IC025 +0.8 3/3 methods agree	Not in label — unassessed	–	no trial data cached
Therapeutic response unexpected	18	4.5 2.8–7.1ROR 4.5 · χ² 46 / p 7e-12	4.1 EB05 2.7 · IC025 +1.2 3/3 methods agree	Reporting / coding artifact	–	no trial data cached
Drug effective for unapproved indication	8	3.1 1.5–6.2ROR 3.1 · χ² 9 / p 0.001	2.7 EB05 1.5 · IC025 +0.2	Not in label — unassessed	–	no trial data cached

Trial evidence (ClinicalTrials.gov)

Trial cross-check not yet run for this drug (ClinicalTrials.gov pull covers the 800 most-reported drugs first).

Most frequently reported reactions

By raw co-report count, regardless of disproportionality. Common terms here are often the illness itself or generic outcomes.

Reaction	Reports	PRR 95% CI · ROR · χ²/p	EBGM EB05 · IC025	Label screen	Serious-only & strata	Trial cross-check
Therapeutic product effect incomplete	134	21.4 18.2–25.2ROR 23.0 · χ² 2,587 / p <1e-300	21.3 EB05 18.4 · IC025 +4.0 3/3 methods agree	Reporting / coding artifact	serious PRR 1.8	no trial data cached
Acne	43	6.4 4.7–8.5ROR 6.5 · χ² 189 / p 2e-43	6.0 EB05 4.6 · IC025 +2.1 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 2.2	no trial data cached
Blood creatine phosphokinase increased	33	12.7 9.1–17.8ROR 12.9 · χ² 345 / p 3e-77	12.3 EB05 8.9 · IC025 +2.9 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 17.9 · 91% clinician	no trial data cached
Therapeutic product effect decreased	26	6.6 4.5–9.7ROR 6.7 · χ² 118 / p 8e-28	6.0 EB05 4.3 · IC025 +1.9 3/3 methods agree	Reporting / coding artifact	–	no trial data cached
Therapeutic response unexpected	18	4.5 2.8–7.1ROR 4.5 · χ² 46 / p 7e-12	4.1 EB05 2.7 · IC025 +1.2 3/3 methods agree	Reporting / coding artifact	–	no trial data cached
Product prescribing error	13	6.2 3.6–10.6ROR 6.2 · χ² 51 / p 4e-13	5.2 EB05 3.2 · IC025 +1.4 3/3 methods agree	Reporting / coding artifact	serious PRR 8.9	no trial data cached
Blood triglycerides increased	9	5.7 3.0–11.0ROR 5.7 · χ² 30 / p 2e-8	4.5 EB05 2.6 · IC025 +1.1 3/3 methods agree	Lab value / disease marker	serious PRR 8.9	no trial data cached
Quality of life decreased	9	7.5 3.9–14.5ROR 7.6 · χ² 45 / p 1e-11	5.8 EB05 3.2 · IC025 +1.3 3/3 methods agree	Not in label — unassessed	serious PRR 6.1	no trial data cached
Hair colour changes	9	8.1 4.2–15.5ROR 8.1 · χ² 49 / p 1e-12	6.1 EB05 3.3 · IC025 +1.4 3/3 methods agree	Not in label — unassessed	–	no trial data cached
Drug effective for unapproved indication	8	3.1 1.5–6.2ROR 3.1 · χ² 9 / p 0.001	2.7 EB05 1.5 · IC025 +0.2	Not in label — unassessed	–	no trial data cached
Tuberculosis	8	7.0 3.5–14.0ROR 7.0 · χ² 35 / p 1e-9	5.3 EB05 2.8 · IC025 +1.2 3/3 methods agree	Labeled — boxed warning exact term	serious PRR 21.3	no trial data cached
Impaired quality of life	7	5.5 2.6–11.5ROR 5.5 · χ² 21 / p 2e-6	4.2 EB05 2.2 · IC025 +0.8 3/3 methods agree	Not in label — unassessed	–	no trial data cached
Lymphopenia	7	5.6 2.7–11.7ROR 5.6 · χ² 22 / p 1e-6	4.3 EB05 2.2 · IC025 +0.8 3/3 methods agree	Not in label — unassessed	serious PRR 10.3	no trial data cached
Folliculitis	7	7.6 3.6–16.0ROR 7.7 · χ² 34 / p 3e-9	5.5 EB05 2.8 · IC025 +1.1 3/3 methods agree	Labeled adverse reaction exact term	–	no trial data cached
Dermatitis atopic	6	1.4 0.6–3.0ROR 1.4 · χ² 0 / p 0.307	1.3 EB05 0.7 · IC025 -1.0 PRR-only: not supported by EBGM or IC	Labeled adverse reaction exact term	–	no trial data cached

Unlabeled candidate signals

Every screened signal with n ≥ 20 was either labeled, an indication term, or an artifact pattern — no unlabeled candidate stood out in the top signals.

Want to assess one of these properly? The runbook describes the Bradford Hill / trial-evidence workflow used on the assessment page, and handoff_top1000_signals.csv lists the strongest unassessed pairs across all drugs.

Common questions

What are the most reported side effects of Ritlecitinib?

In FDA FAERS, the most frequently co-reported reaction terms for Ritlecitinib are acne, blood creatine phosphokinase increased, blood triglycerides increased, quality of life decreased, hair colour changes, drug effective for unapproved indication. These are report counts, not rates: FAERS has no denominator, reporting is voluntary and uneven, and a term can be reported because of the illness being treated rather than the drug.

Does Ritlecitinib have an FDA boxed warning?

Yes. The current FDA label carries a boxed 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.

Do FAERS signals prove that Ritlecitinib causes these side effects?

No. A disproportionality signal (PRR, ROR) means a reaction is reported more often with this drug than with others in the database. That can reflect a real effect, but also the disease being treated, stimulated reporting after news or litigation, co-medications, or how reports are coded. Causality needs temporality, dose-response, biological plausibility, consistency across data sources and, ideally, trial or cohort evidence. This page screens each term against the FDA label and ClinicalTrials.gov results; it does not establish causation.

Sources & methods

FDA label via openFDA (set ID 1882f799-61b0-4813-965a-4910c4ae419c, effective 20260617; matched on openfda.generic_name.exact:"RITLECITINIB")
Bayesian shrinkage measures computed offline over all 1,317,300 cached pairs: BCPNN information component (IC, with Norén closed-form IC025) and MGPS empirical-Bayes geometric mean (EBGM, EB05) with a two-component gamma prior fitted by maximum marginal likelihood (α₁=0.57, β₁=0.02, α₂=1.42, β₂=0.70, w=0.17); unstratified
FAERS pair statistics from the OpenPV build of 2026-09-14 (openFDA count= aggregation, field patient.drug.openfda.generic_name.exact, 18 reaction terms, min 3 co-reports); PRR/ROR with 95% CI, chi-square with Yates correction
Serious-only and stratified counts (serious:1, patient.patientsex, primarysource.qualification) from openFDA count queries; serious-only PRR uses the drug serious report total and the term global serious total (N_serious=11,882,979); strata shown only when n ≥ 20
Seriousness and sex counts from openFDA count=serious, patient.patientsex, seriousnessdeath

Page generated 2026-10-08. Label and PubChem text are retrieved automatically and may lag the current label; always check the current prescribing information. OpenPV is a beta research tool of the Open Source Medicine Foundation.