NCT05128058 is a Phase 1 clinical trial of Ritlecitinib 50 mg in Healthy, sponsored by Pfizer.

Who is sponsoring NCT05128058?

NCT05128058 is sponsored by Pfizer.

What drugs are being tested in NCT05128058?

Interventions in NCT05128058: Ritlecitinib 50 mg, Ritlecitinib 200 mg.

Is NCT05128058 still recruiting?

NCT05128058 is currently completed. Last updated 13 November 2023.

Are results published for NCT05128058?

Yes — primary outcome results have been posted to ClinicalTrials.gov. See the outcomes section above for details.

Last reviewed 2023-11-13 · How we verify

NCT05128058

Name: Drug Landscape Pharmaceutical Database
Creator: Drug Landscape
Published: 2026-01-01
License: https://creativecommons.org/licenses/by/4.0/

A Target Occupancy Study With Ritlecitinib.

Completed Phase 1 Results posted Last updated 13 November 2023

What this trial tests

Phase 1 trial testing Ritlecitinib 50 mg in Healthy in 16 participants. Completed in 14 January 2022.

Timeline

22 October 2021

Primary endpoint
14 January 2022

14 January 2022

Quick facts

Lead sponsor	Pfizer
Phase	Phase 1
Status	Completed
Study type	INTERVENTIONAL
Allocation	non randomized
Design	parallel
Masking	none
Primary purpose	basic science
Enrollment	16
Start date	22 October 2021
Primary completion	14 January 2022
Estimated completion	14 January 2022
Sites	1 location across United States

Drugs / interventions tested

Ritlecitinib 50 mg (ritlecitinib-50-mg) — full drug profile →
Ritlecitinib 200 mg — full drug profile →

Conditions studied

Healthy — all drugs for Healthy →

Sponsor

Pfizer — full company profile →

Who can join

Adults 18 to 60, any sex, with Healthy. Patients with the condition only — healthy volunteers not accepted.

Results — posted to ClinicalTrials.gov

Per-arm endpoint measurements with 95% confidence intervals where reported. Source: trial results section.

Percent Target Occupancy for JAK3 Primary · -1 (pre-dose), 0 (pre-dose), 1, 2, 4, 8, 24, 48 hours post-dose

Target occupancy for janus kinase 3 (JAK3) in peripheral blood mononuclear cells (PBMCs) by ritlecitinib was investigated in human blood by chemical probe-based enrichment and liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) analysis. % TO is calculated as \[(baseline value - value at specified time point)\*100/baseline value\], where baseline value in this formula is defined as the mean of the two pre-dose measurements at Hour -1 and Hour 0 on Day 1. Since (baseline value - value at specified time point)=0 at baseline, % TO at baseline is 0.

Baseline

Group	Value	95% CI
RITLECITINIB 50 MG CAPSULE	0.00	0.0 – 0.0
RITLECITINIB 200 MG CAPSULE	0.00	0.0 – 0.0

Group	Value	95% CI
RITLECITINIB 50 MG CAPSULE	72.41	49.2 – 98.0
RITLECITINIB 200 MG CAPSULE	28.74	-5.8 – 51.1

Group	Value	95% CI
RITLECITINIB 50 MG CAPSULE	12.28	-30.1 – 39.5
RITLECITINIB 200 MG CAPSULE	64.14	54.1 – 75.0

Group	Value	95% CI
RITLECITINIB 50 MG CAPSULE	-1.39	-19.6 – 5.2
RITLECITINIB 200 MG CAPSULE	62.06	45.3 – 73.9

Group	Value	95% CI
RITLECITINIB 50 MG CAPSULE	-23.34	-49.1 – 17.7
RITLECITINIB 200 MG CAPSULE	58.76	38.9 – 65.2

24H

Group	Value	95% CI
RITLECITINIB 50 MG CAPSULE	-24.72	-58.2 – -10.2
RITLECITINIB 200 MG CAPSULE	37.08	30.2 – 53.1

48H

Group	Value	95% CI
RITLECITINIB 50 MG CAPSULE	-25.34	-51.8 – 3.7
RITLECITINIB 200 MG CAPSULE	33.44	9.4 – 52.9

Percent Target Occupancy for BTK Primary · -1 (pre-dose), 0 (pre-dose), 1, 2, 4, 8, 24, 48 hours post-dose

Target occupancy for Bruton's tyrosine kinase (BTK) in PBMCs by ritlecitinib was investigated in human blood by chemical probe-based enrichment and LC-MS/MS analysis. % TO is calculated as \[(baseline value - value at specified time point)\*100/baseline value\], where baseline value in this formula is defined as the mean of the two pre-dose measurements at Hour -1 and Hour 0 on Day 1. Since (baseline value - value at specified time point)=0 at baseline, % TO at baseline is 0.

Baseline

Group	Value	95% CI
RITLECITINIB 50 MG CAPSULE	0.00	0.0 – 0.0
RITLECITINIB 200 MG CAPSULE	0.00	0.0 – 0.0

Group	Value	95% CI
RITLECITINIB 50 MG CAPSULE	98.45	95.4 – 99.8
RITLECITINIB 200 MG CAPSULE	99.57	98.2 – 99.8

Group	Value	95% CI
RITLECITINIB 50 MG CAPSULE	96.83	92.1 – 99.2
RITLECITINIB 200 MG CAPSULE	99.37	98.6 – 99.8

Group	Value	95% CI
RITLECITINIB 50 MG CAPSULE	96.43	90.4 – 99.1
RITLECITINIB 200 MG CAPSULE	99.35	99.2 – 99.8

Group	Value	95% CI
RITLECITINIB 50 MG CAPSULE	93.52	85.3 – 97.8
RITLECITINIB 200 MG CAPSULE	99.21	97.1 – 99.5

24H

Group	Value	95% CI
RITLECITINIB 50 MG CAPSULE	83.21	76.5 – 86.3
RITLECITINIB 200 MG CAPSULE	92.13	87.0 – 95.5

48H

Group	Value	95% CI
RITLECITINIB 50 MG CAPSULE	69.86	63.3 – 76.4
RITLECITINIB 200 MG CAPSULE	82.66	75.8 – 88.1

Percent Target Occupancy for ITK Primary · -1 (pre-dose), 0 (pre-dose), 1, 2, 4, 8, 24, 48 hours post-dose

Target occupancy forIL 2 inducible T-cell kinase (ITK) in PBMCs by ritlecitinib was investigated in human blood by chemical probe-based enrichment and LC-MS/MS analysis. % TO is calculated as \[(baseline value - value at specified time point)\*100/baseline value\], where baseline value in this formula is defined as the mean of the two pre-dose measurements at Hour -1 and Hour 0 on Day 1. Since (baseline value - value at specified time point)=0 at baseline, % TO at baseline is 0.

Baseline

Group	Value	95% CI
RITLECITINIB 50 MG CAPSULE	0.00	0.0 – 0.0
RITLECITINIB 200 MG CAPSULE	0.00	0.0 – 0.0

Group	Value	95% CI
RITLECITINIB 50 MG CAPSULE	94.40	86.2 – 100.0
RITLECITINIB 200 MG CAPSULE	97.03	73.8 – 98.0

Group	Value	95% CI
RITLECITINIB 50 MG CAPSULE	67.77	42.2 – 88.4
RITLECITINIB 200 MG CAPSULE	97.06	94.5 – 98.1

Group	Value	95% CI
RITLECITINIB 50 MG CAPSULE	57.54	23.0 – 73.9
RITLECITINIB 200 MG CAPSULE	92.27	86.0 – 97.4

Group	Value	95% CI
RITLECITINIB 50 MG CAPSULE	28.76	-5.5 – 58.0
RITLECITINIB 200 MG CAPSULE	76.59	60.0 – 88.9

24H

Group	Value	95% CI
RITLECITINIB 50 MG CAPSULE	-16.77	-42.1 – 30.5
RITLECITINIB 200 MG CAPSULE	32.33	12.4 – 43.8

48H

Group	Value	95% CI
RITLECITINIB 50 MG CAPSULE	-9.87	-61.0 – 21.6
RITLECITINIB 200 MG CAPSULE	20.62	-16.0 – 44.7

Percent Target Occupancy for TXK Primary · -1 (pre-dose), 0 (pre-dose), 1, 2, 4, 8, 24, 48 hours post-dose

Target occupancy for tyrosine kinase expressed in T cells (TXK) in PBMCs by ritlecitinib was investigated in human blood by chemical probe-based enrichment and LC-MS/MS analysis. % TO is calculated as \[(baseline value - value at specified time point)\*100/baseline value\], where baseline value in this formula is defined as the mean of the two pre-dose measurements at Hour -1 and Hour 0 on Day 1. Since (baseline value - value at specified time point)=0 at baseline, % TO at baseline is 0.

Baseline

Group	Value	95% CI
RITLECITINIB 50 MG CAPSULE	0.00	0.0 – 0.0
RITLECITINIB 200 MG CAPSULE	0.00	0.0 – 0.0

Group	Value	95% CI
RITLECITINIB 50 MG CAPSULE	100.00	88.6 – 100.0
RITLECITINIB 200 MG CAPSULE	100.00	37.7 – 100.0

Group	Value	95% CI
RITLECITINIB 50 MG CAPSULE	44.97	27.1 – 66.7
RITLECITINIB 200 MG CAPSULE	100.00	100.0 – 100.0

Group	Value	95% CI
RITLECITINIB 50 MG CAPSULE	34.01	-15.8 – 52.1
RITLECITINIB 200 MG CAPSULE	100.00	87.9 – 100.0

Group	Value	95% CI
RITLECITINIB 50 MG CAPSULE	23.17	-41.0 – 60.7
RITLECITINIB 200 MG CAPSULE	82.46	63.1 – 100.0

24H

Group	Value	95% CI
RITLECITINIB 50 MG CAPSULE	-4.09	-43.4 – 31.4
RITLECITINIB 200 MG CAPSULE	49.70	33.2 – 59.7

48H

Group	Value	95% CI
RITLECITINIB 50 MG CAPSULE	-38.98	-83.7 – 17.7
RITLECITINIB 200 MG CAPSULE	20.34	1.9 – 58.8

Percent Target Occupancy for TEC Primary · -1 (pre-dose), 0 (pre-dose), 1, 2, 4, 8, 24, 48 hours post-dose

Target occupancy for tyrosine kinase expressed carcinoma (TEC) in PBMCs by ritlecitinib was investigated in human blood by chemical probe-based enrichment and LC-MS/MS analysis. % TO is calculated as \[(baseline value - value at specified time point)\*100/baseline value\], where baseline value in this formula is defined as the mean of the two pre-dose measurements at Hour -1 and Hour 0 on Day 1. Since (baseline value - value at specified time point)=0 at baseline, % TO at baseline is 0.

Baseline

Group	Value	95% CI
RITLECITINIB 50 MG CAPSULE	0.00	0.0 – 0.0
RITLECITINIB 200 MG CAPSULE	0.00	0.0 – 0.0

Group	Value	95% CI
RITLECITINIB 50 MG CAPSULE	96.50	87.4 – 100.0
RITLECITINIB 200 MG CAPSULE	100.0	96.0 – 100.0

Group	Value	95% CI
RITLECITINIB 50 MG CAPSULE	94.60	88.3 – 98.0
RITLECITINIB 200 MG CAPSULE	99.42	98.3 – 100.0

Group	Value	95% CI
RITLECITINIB 50 MG CAPSULE	94.23	90.9 – 98.3
RITLECITINIB 200 MG CAPSULE	98.78	98.1 – 100.0

Group	Value	95% CI
RITLECITINIB 50 MG CAPSULE	93.12	85.5 – 98.6
RITLECITINIB 200 MG CAPSULE	99.57	97.4 – 100.0

24H

Group	Value	95% CI
RITLECITINIB 50 MG CAPSULE	90.64	83.7 – 95.8
RITLECITINIB 200 MG CAPSULE	96.85	94.1 – 97.8

48H

Group	Value	95% CI
RITLECITINIB 50 MG CAPSULE	82.48	75.7 – 87.3
RITLECITINIB 200 MG CAPSULE	92.32	87.9 – 94.8

Percent Target Occupancy for BMX Primary · -1 (pre-dose), 0 (pre-dose), 1, 2, 4, 8, 24, 48 hours post-dose

Target occupancy for bone marrow tyrosine kinase gene in chromosome X (BMX) in PBMCs by ritlecitinib was investigated in human blood by chemical probe-based enrichment and LC-MS/MS analysis. % TO is calculated as \[(baseline value - value at specified time point) \*100/baseline value\], where baseline value in this formula is defined as the mean of the two pre-dose measurements at Hour -1 and Hour 0 on Day 1. Since (baseline value - value at specified time point)=0 at baseline, % TO at baseline is 0.

Baseline

Group	Value	95% CI
RITLECITINIB 50 MG CAPSULE	0.00	0.0 – 0.0
RITLECITINIB 200 MG CAPSULE	0.00	0.0 – 0.0

Group	Value	95% CI
RITLECITINIB 50 MG CAPSULE	67.51	-16.4 – 96.0
RITLECITINIB 200 MG CAPSULE	99.13	91.9 – 100.0

Group	Value	95% CI
RITLECITINIB 50 MG CAPSULE	85.26	68.5 – 100.0
RITLECITINIB 200 MG CAPSULE	92.53	88.7 – 100.0

Group	Value	95% CI
RITLECITINIB 50 MG CAPSULE	84.93	76.0 – 100.0
RITLECITINIB 200 MG CAPSULE	92.26	87.7 – 100.0

Group	Value	95% CI
RITLECITINIB 50 MG CAPSULE	87.08	69.9 – 95.3
RITLECITINIB 200 MG CAPSULE	92.48	85.0 – 98.7

24H

Group	Value	95% CI
RITLECITINIB 50 MG CAPSULE	68.13	51.5 – 87.9
RITLECITINIB 200 MG CAPSULE	91.32	82.1 – 97.9

48H

Group	Value	95% CI
RITLECITINIB 50 MG CAPSULE	26.50	-15.6 – 54.1
RITLECITINIB 200 MG CAPSULE	62.34	52.5 – 79.4

Maximum Observed Plasma Concentration (Cmax) of Ritlecitinib Secondary · 0 (pre-dose), 1, 2, 4, 8, 24, 48 hours post-dose

Cmax is maximum observed plasma concentration. Cmax for ritlecitinib was observed directly from data.

Group	Value	95% CI
RITLECITINIB 50 MG CAPSULE	297.1	± 51
RITLECITINIB 200 MG CAPSULE	1275	± 20

Time to Reach Maximum Observed Plasma Concentration (Tmax) of Ritlecitinib Secondary · 0 (pre-dose), 1, 2, 4, 8, 24, 48 hours post-dose

Tmax is time for Cmax. Tmax for ritlecitinib was observed directly from data as time of first occurrence.

Group	Value	95% CI
RITLECITINIB 50 MG CAPSULE	1.00	1.00 – 2.00
RITLECITINIB 200 MG CAPSULE	1.00	1.00 – 2.00

Last Quantifiable Plasma Concentration (Clast) of Ritlecitinib Secondary · 0 (pre-dose), 1, 2, 4, 8, 24, 48 hours post-dose

Clast is last quantifiable plasma concentration. Clast for ritlecitinib was observed directly from data.

Group	Value	95% CI
RITLECITINIB 50 MG CAPSULE	4.812	± 87
RITLECITINIB 200 MG CAPSULE	4.036	± 666

Average Plasma Concentration From Time 0 to 24 Hours (Cav) of Ritlecitinib Secondary · 0 (pre-dose), 1, 2, 4, 8, 24 hours post-dose

Cav is average plasma concentration from time 0 to 24 hours over the 24 hours period. Cav for ritlecitinib was calculated as area under the plasma concentration-time curve from 0 to 24 hours (AUC24) divided by 24.

Group	Value	95% CI
RITLECITINIB 50 MG CAPSULE	28.42	± 51
RITLECITINIB 200 MG CAPSULE	144.9	± 42

Area Under the Curve From Time Zero to Last Quantifiable Concentration (AUClast) of Ritlecitinib Secondary · 0 (pre-dose), 1, 2, 4, 8, 24, 48 hours post-dose

AUClast is area under the plasma concentration-time profile from time 0 to the time of the Clast. AUClast for ritlecitinib was determined using linear/log trapezoidal method.

Group	Value	95% CI
RITLECITINIB 50 MG CAPSULE	651.4	± 50
RITLECITINIB 200 MG CAPSULE	3382	± 43

Area Under the Curve From Time 0 to 24 Hours (AUC24) of Ritlecitinib Secondary · 0 (pre-dose), 1, 2, 4, 8, 24 hours post-dose

AUC24 is area under the plasma concentration-time curve from time 0 to 24 hours. AUC24 for ritlecitinib was determined using linear/log trapezoidal method.

Group	Value	95% CI
RITLECITINIB 50 MG CAPSULE	681.8	± 51
RITLECITINIB 200 MG CAPSULE	3475	± 42

Adverse events — posted to ClinicalTrials.gov

Time frame: Baseline up to 35 days after the last dose of study treatment on Day 1 (up to 35 days). Reporting threshold: 5%. Adverse-event reports describe events observed during the trial — not all are caused by the drug.

RITLECITINIB 50 MG CAPSULE

Serious: 0/8 (0%)

Deaths: 0/8

RITLECITINIB 200 MG CAPSULE

Serious: 0/8 (0%)

Deaths: 0/8

Other adverse events (6 terms — click to expand)

Reaction	System	RITLECITINIB 50 MG CAPSULE	RITLECITINIB 200 MG CAPSULE
Abdominal distension	Gastrointestinal disorders	—	—
Dyspepsia	Gastrointestinal disorders	—	—
Escherichia urinary tract infection	Infections and infestations	—	—
Gastroenteritis viral	Infections and infestations	—	—
Procedural dizziness	Injury, poisoning and procedural complications	—	—
Pain in extremity	Musculoskeletal and connective tissue disorders	—	—

Data from ClinicalTrials.gov NCT05128058 adverse events section.

Sponsor's own description

This is a phase 1, open label, two-arm study to assess target occupancy and functional inhibition of JAK3 and TEC kinases by Ritlecitinib in healthy adult participants

Publications & conference data

1 peer-reviewed publication reference this trial (live from Europe PMC):

Virtual Bioequivalence Assessment of Ritlecitinib Capsules with Incorporation of Observed Clinical Variability Using a Physiologically Based Pharmacokinetic Model.
Saadeddin A, Purohit V, Huh Y, Wong M, et al · · 2024 · cited 14× · PMID 38267790 · DOI 10.1208/s12248-024-00888-9

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Verify against primary sources

ClinicalTrials.gov — authoritative US registry record
WHO ICTRP — international registry index
EU Clinical Trials Register
Sponsor press releases (Google)

Data sources for this page

Trial protocol + status: ClinicalTrials.gov NCT05128058 (US National Library of Medicine, public domain)
Publications: Europe PMC API search by NCT ID, retrieved 10 June 2026
Drug + disease cross-links: matched in real time against Drug Landscape's normalised drug + company + condition tables
Sponsor: as reported to ClinicalTrials.gov by Pfizer
Last refreshed: 13 November 2023

Drug Landscape aggregates and links these public records for informational use only. Always verify against the primary source before clinical or regulatory decisions. Canonical URL: https://druglandscape.com/trial/NCT05128058.

Primary sources · FDA · ClinicalTrials.gov · EMA · SEC EDGAR · ChEMBL · Wikidata · full sourcing

NCT05128058

Quick facts

Drugs / interventions tested

Conditions studied

Sponsor

Who can join

Results — posted to ClinicalTrials.gov

Adverse events — posted to ClinicalTrials.gov

Sponsor's own description

Publications & conference data

Related trials

Other trials of Ritlecitinib 50 mg

Other recruiting trials for Healthy

Other Pfizer trials

Verify against primary sources