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PF-06651600

Phase 3

Alopecia Areata | Small molecule | Dermatology |Pfizer, Inc.|Last Updated: Jul 15, 2026

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Trial Design

RandomizedDouble-BlindPLACEBO_CONTROLLEDDMC
Total Trials3
Total Enrollment1,917

FDA Designations

No designations recorded

Clinical trial landscape

PF-06651600 · 20 trials · 11 indications

Phase 3 1Phase 2 6Phase 1 13
NCT04006457Long-Term PF-06651600 for the Treatment of Alopecia AreataAlopecia Areata
COMPLETED1,057 Analytics
PHASE3COMPLETED
Long-Term PF-06651600 for the Treatment of Alopecia Areata
Alopecia AreataUnlock trial analytics

Study Endpoints

Primary Endpoints

Main Study: Number of Participants With Treatment Emergent Adverse Events (TEAEs) Until Follow-up Visit
From start of study intervention (Day 1) until follow-up visit (4 weeks after last dose in Treatment period 1) (Up to Month 40)

An AE is any untoward medical occurrence in a clinical study participant, temporally associated with the use of study intervention, whether or not considered related to the study intervention. An AE was considered treatment emergent if the event had start date on or after the first dosing date of this study.

Main Study: Number of Participants With Serious Adverse Events (SAEs) and Adverse Events (AEs) Leading to Discontinuation Until Follow-up Visit
From start of study intervention (Day 1) until follow-up visit (4 weeks after last dose in Treatment period 1) (Up to Month 40)

An AE is any untoward medical occurrence in a clinical study participant, temporally associated with the use of study intervention, whether or not considered related to the study intervention. An SAE was any untoward medical occurrence that at any dose: resulted in death; required inpatient hospitalization or prolongation of existing hospitalization; was life-threatening; resulted in persistent disability/incapacity; was a congenital anomaly/birth defect; other important medical events. AEs leading to discontinuation included participants who had an AE record that indicated that the AE caused the participant to be discontinued from the study or that action taken with study treatment was drug withdrawn.

Main Study: Number of Participants According to Categorization of Vital Signs Data Until Follow-up Visit
From start of study intervention (Day 1) until follow-up visit (4 weeks after last dose in Treatment period 1) (Up to Month 40)

Vital signs including blood pressure included systolic blood pressure (SBP) \[Millimeters of mercury, mmHg\]) and diastolic blood pressure (DBP) and pulse rate \[beats per minute (bpm)\] were measured using an automated device in a sitting position after at least 5 minutes of rest for the participant in a quiet setting without distractions. Criteria for vital sign abnormalities included: SBP\<90mmHg, DBP\<50 mmHg and pulse rate\<40mmHg.

Main Study: Number of Participants With Clinically Significant Abnormalities in Clinical Laboratory Values Until Follow-up Visit
From start of study intervention (Day 1) until follow-up visit (4 weeks after last dose in Treatment period 1) (Up to Month 40)

Criteria for laboratory abnormalities included:Hemoglobin, Hematocrit, Erythrocytes (\<0.8\*LLN); Ery. Volume, Hemoglobin,Mean Corpuscular HGB Concentration \<0.8\*LLN or \>1.5\*LLN;Reticulocytes, Leukocytes, Lymphocytes, Neutrophils, Neutrophils, Basophils, Eosinophils, Monocytes (\>1.2\*ULN), Prothrombin Time(\>1.1\*ULN).Clinical Chemistry: Bilirubin, Direct Bilirubin, Indirect Bilirubin (1.5\*ULN), Aspartate Aminotransferase, Alanine Aminotransferase, Gamma Glutamyl Transferase, Alkaline Phosphatase (\>3.0\*ULN); Albumin, Urate (\<0.8\*LLN and \>1.2\*ULN; Urea Nitrogen,Creatinine Cholesterol \>1.3\*ULN; Cholesterol \<0.8\*LLN or \>1.2\*LLN, Triglycerides,Potassium,Calcium \< 0.9x LLN \& \> 1.1x ULN; Bicarbonate, Glucose, Creatine Kinase. Urinalysis: Glucose, Ketones, Protein, Hemoglobin, Urobilinogen, Bilirubin, Nitrite \>=1; Leukocyte Erythrocytes, Leukocytes \>=20; Epithelial Cells\>=6, Hyaline Cast\>1; Bacteria\>20. Number of participants with any laboratory abnormality meeting specified criteria is included.

Vaccine Sub-study: Percentage of Participants With Tetanus Booster Response
Month 1

Booster response to tetanus toxoid was defined as: \>=4-fold rise in anti-tetanus toxoid immunoglobulin G (IgG) antibody concentration at Month 1 if the pre-vaccination concentration was \<=2.7 International Units per milliliter (IU/mL); OR \>=2-fold rise in anti-tetanus toxoid IgG antibody concentration if the pre-vaccination concentration was \>2.7 IU/mL. Two-sided 95% confidence interval (CI) was based on Clopper-Pearson exact method.

Change in Ct Values of mRNA Levels of CCL5 Gene
Baseline to Week 24

Log-fold Changes in mRNA Levels of CCL5 gene expression in skin biopsies quantified by normalized Ct values obtained by quantitative real-time PCR assay, measured at baseline and week 24. The unit of the outcome is called Ct value and it represents the number of amplification cycles to reach a level of fluorescence in the experiment. The Ct value is directly associated to the level of expression of a gene

Number of Treatment-Emergent Adverse Events
Week 48

The adverse event will be described and categorized as Treatment-emergent, Serious, abnormal in vital signals, and abnormalities in laboratory parameters.

Percentage of Participants With an Absolute Severity of Alopecia Tool (SALT) Score of Less Than or Equal to 20 at Week 24
Week 24

SALT is a quantitative assessment of AA severity based on the scalp hair loss. The SALT score can vary from 0 (normal) to 100 (severe), with higher scores representing increased severity of disease. In this outcome measure, percentage of participants with SALT score less than or equal to (\<=) 20 at week 24 were reported.

Percent Change From Baseline in Central Read Facial-Vitiligo Area Scoring Index (F-VASI) at Week 24 - Dose Ranging (DR) Period
Baseline, Week 24 (Baseline was defined as the last measurement prior to Study Day 18)

Central read F-VASI was assessed based on the facial photographs taken at the site. Central read F-VASI was calculated using a formula that included contribution of affected facial surface areas showing all 6 different depigmentation rates (0.1, 0.25, 0.5, 0.75, 0.9 and 1) with a modified method: F-VASI (central read)=Ʃ \[Affected Facial Surface Area\] × 4 × \[Depigmentation Rates\]. Face was defined as the area from the hairline on top of the forehead to the jawline at the bottom of the cheeks. F-VASI (central read) ranged from 0.000 to 4.000 by defining the affected Facial Surface Area (expressed as the value between 0.0 to 1.0) being 4% of total Body Surface Area. The higher score of F-VASI signified severer symptoms of non-segmental vitiligo. Percent change from baseline in central read F-VASI = ((post-baseline central read F-VASI - baseline central read F-VASI)/baseline central read F-VASI)×100. A negative percent change from baseline in central read F-VASI signified an improvement.

Number of Participants With Treatment Emergent Adverse Events (TEAEs) and Serious Adverse Events (SAEs) up to Week 24 - DR Period
24 weeks

Adverse Event (AE) was defined as any untoward medical occurrence in a study participant administered a product or medical device; the event did not necessarily need to have a causal relationship with the treatment or usage. An AE was considered a TEAE if the event started during the effective duration of treatment. All events that started on or after the first dosing day and time/start time, if collected, but before the last dose plus the lag time were flagged as TEAEs. SAE was defined as any untoward medical occurrence at any dose that resulted in death; was life threatening (immediate risk of death); required inpatient hospitalization or prolongation of existing hospitalization; resulted in persistent or significant disability/incapacity (substantial disruption of the ability to conduct normal life functions); resulted in congenital anomaly/birth defect; or that was considered to be an important medical event. Causality to study treatment was determined by the investigator.

Number of Participants With the TEAEs of Anaemia, Neutropenia, Thrombocytopenia and Lymphopenia - DR Period
Baseline up to Week 24

An AE was any untoward medical occurrence in a study participant administered a product or medical device; the event did not necessarily need to have a causal relationship with the treatment or usage. The abnormal test findings, clinically significant signs and symptoms of anaemia, neutropenia, thrombocytopenia and lymphopenia were reported as AEs. The clinical significance was determined by the investigator. An AE was considered a TEAE if the event started during the effective duration of treatment. All events that started on or after the first dosing day and time/start time, if collected, but before the last dose plus the lag time were flagged as TEAEs. Baseline was defined as the last measurement prior to first dosing (Day 1).

Number of Participants With Clinically Meaningful Changes From Baseline in Lipid Profile up to Week 24 - DR Period
Baseline up to Week 24

Participants had to abstain from all food and drink (except water and non-investigational products) for an 8-hour overnight fast prior to fasting lipid profile panel collection. Fasting lipid assessment included total cholesterol, low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol, and triglycerides. The clinical meaningfulness was determined by the investigator. Baseline was defined as the last measurement prior to first dosing (Day 1).

Number of Participants With Liver Function Test Values Meeting the Protocol-Specified Discontinuation Criteria - DR Period
24 weeks

Liver function tests included tests of alanine aminotransferase (ALT), aspartate aminotransferase (AST) and total bilirubin.

Number of Participants With TEAEs and SAEs - Extension (Ext) Period
24 weeks

AE was defined as any untoward medical occurrence in a study participant administered a product or medical device; the event did not necessarily need to have a causal relationship with the treatment or usage. An AE was considered a TEAE if the event started during the effective duration of treatment. All events that started on or after the first dosing day and time/start time, if collected, but before the last dose plus the lag time were flagged as TEAEs. SAE was defined as any untoward medical occurrence at any dose that resulted in death; was life threatening (immediate risk of death); requires inpatient hospitalization or prolongation of existing hospitalization; resulted in persistent or significant disability/incapacity (substantial disruption of the ability to conduct normal life functions); resulted in congenital anomaly/birth defect; or that was considered to be an important medical event. Causality to study treatment was determined by the investigator.

Number of Participants With the TEAEs of Anaemia, Neutropenia, Thrombocytopenia and Lymphopenia - Ext Period
24 weeks

An AE was any untoward medical occurrence in a study participant administered a product or medical device; the event did not necessarily need to have a causal relationship with the treatment or usage. The abnormal test findings, clinically significant signs and symptoms of anaemia, neutropenia, thrombocytopenia and lymphopenia were reported as AEs. The clinical significance was determined by the investigator. An AE was considered a TEAE if the event started during the effective duration of treatment. All events that started on or after the first dosing day and time/start time, if collected, but before the last dose plus the lag time were flagged as TEAEs.

Number of Participants With Clinically Meaningful Changes From Baseline in Lipid Profile - Ext Period
24 Weeks

Participants had to abstain from all food and drink (except water and non-investigational products) for an 8-hour overnight fast prior to fasting lipid profile panel collection. Fasting lipid assessment included total cholesterol, LDL cholesterol, HDL cholesterol, and triglycerides. The clinical meaningfulness was determined by the investigator.

Number of Participants With Liver Function Test Values Meeting the Protocol-Specified Discontinuation Criteria - Ext Period
24 weeks

Liver function tests included tests of alanine aminotransferase (ALT), aspartate aminotransferase (AST) and total bilirubin.

Percentage of Participants Achieving Greater Than or Equal to (>=) 50 Percent (%) Reduction in Simple Endoscopic Score for Crohn's Disease (SES CD50) at Week 12: Induction Period
Week 12

SES CD50 was defined as 50% improvement from baseline in SES-CD. Baseline was defined as last measurement prior to first dosing on Day 1. Following bowel segments were used for calculating SES-CD scores: Ileum, right colon(C), transverse C, left C and rectum. Each segment assessed for four domains: presence of ulcers, ulcerated surface, affected surface and presence of narrowing, each scored on a scale of 0 to 3, higher scores indicated more severe condition. Presence of ulcers score: 0=none, 1=small ulcer: (0.1-0.5 centimeter\[cm\]), 2=Large ulcer(0.5-2 cm), 3=very large ulcer(\>2 cm); ulcerated surface score: 0=none, 1=\<10%, 2=10-30% and 3=\>30%; affected surface score: 0=unaffected segment, 1=\<50%, 2=50-75% and 3=\>75%; presence of narrowing score: 0=none,1=single, can be passed, 2=multiple, can be passed and 3=cannot be passed. Total SES CD score was determined by sum of each domain score for all 5 bowel segments and ranged from 0 to 60, higher score indicating more severe disease.

Number of Participants With Laboratory Test Abnormalities During OLE Period
From start of study intervention in OLE period up to 4 weeks after last dose of study intervention (up to 56 weeks)

Pre-specified criteria for lab abnormalities included- hematology: hemoglobin(Hb), erythrocytes (ery),hematocrit:\<0.8\*lower limit of normal(LLN);reticulocytes: \<0.5\*LLN, \>1.5\*upper limit of normal(ULN); ery mean corpuscular(EMC) volume: \<0.9\*ULN, \>1.11\*ULN;EMC Hb: \<0.9\*LLN; platelets:\>1.75\*ULN; leukocytes(10\^9/L): \<0.6\*LLN,\>1.5\*ULN;lymphocyte,neutrophil(10\^9/L):\<0.8\*LLN,\>1.2\*ULN;basophil,eosinophil,monocyte(10\^9/L):\>1.2\*ULN;activated partial thromboplastin time (sec): \>1.1\*ULN. Chemistry: bilirubin(mg/dL),aspartate aminotransferase(AT),alanine AT(units per litre)\>3.0\*ULN; protein, albumin(g/dL):\<0.8\*LLN; creatinine, triglycerides (mg/dL):\>1.3\*ULN; urate(mg/dL):\>1.2\*ULN, potassium (mEq/L):\<0.9\*LLN; calcium (mg/dL): \<0.9\*LLN,\>1.1\*ULN. Urinalysis: pH\>8;urine,glucose,protein(mg/dl); ketones, nitrite, urine Hb(scalar):\>=1. Number of participants with any lab abnormality meeting pre-specified criteria are reported.

Number of Participants According to Categorization of Vital Signs During OLE Period
From start of study intervention in OLE period up to 4 weeks after last dose of study intervention (up to 56 weeks)

Vital signs including blood pressure (diastolic blood pressure \[DBP\], systolic blood pressure \[SBP\], and pulse rate \[PR\]) were measured in a supine position using automated devices. DBP included value \< 50 (millimeter of mercury \[mmHg\]), change \>=20 (mmHg) increase and change \>=20 (mmHg) decrease; SBP: value \< 90 (mmHg), change \>= 30 (mmHg) increase and change \>= 30 (mmHg) decrease; PR: value \> 120 (beats per minute \[bpm\]).

Number of Participants With Abnormal Clinically Significant Electrocardiogram Findings During OLE Period
From start of study intervention in OLE period up to 4 weeks after last dose of study intervention (up to 56 weeks)

Single twelve lead ECGs were obtained using an automated ECG machine after participant had rested quietly for at least 10 minutes in a supine position. QTc prolongations were defined as a QTc \>=480 milli second (msec) or an absolute change in QTc greater than (\>) 60 msec. Clinically significant ECG findings were determined by the investigator.

Number of Participants With Treatment Emergent Adverse Events (TEAEs) During OLE Period
From start of study intervention in OLE period up to 4 weeks after last dose of study intervention (up to 56 weeks)

An adverse event (AE) was any untoward medical occurrence in a study participant administered a study intervention; the event need not necessarily have a causal relationship with the treatment or usage. An AE was considered TEAE to a given treatment if the event started during the effective duration of treatment regardless of whether a similar event of equal or greater severity existed in the baseline period.

Number of Participants With Treatment Emergent Serious Adverse Events (TESAE) During OLE Period
From start of study intervention in OLE period up to 4 weeks after last dose of study intervention (up to 56 weeks)

A serious adverse event (SAE) was any untoward medical occurrence at any dose that: resulted in death; was life-threatening (immediate risk of death); required inpatient hospitalization or prolongation of existing hospitalization; resulted in persistent or significant disability/incapacity (substantial disruption of the ability to conduct normal life functions) or resulted in congenital anomaly/birth defect or was considered an important medical event. An SAE was considered as TESAE if the event started during the effective duration of treatment regardless of whether a similar event of equal or greater severity existed in the baseline period.

Number of Participants With Discontinuations Due to Adverse Events During OLE Period
From start of study intervention in OLE period up to 4 weeks after last dose of study intervention (up to 56 weeks)

An AE was any untoward medical occurrence in a study participant administered a study intervention; the event need not necessarily have a causal relationship with the treatment or usage. Discontinuations from study due to TEAEs were defined as participants with an AE record indicating the AE caused permanent discontinuation from the study but action taken with study treatment was not drug withdrawn. Permanent discontinuations from any study intervention due to TEAEs were defined as participants with an AE record indicating that action taken with study treatment was drug withdrawn. In this outcome measure number of participants with discontinuation from study due to AEs and permanent discontinuation from study intervention due to AEs are reported.

Change From Baseline in Simple Disease Activity Index (SDAI) Score at Week 8
Baseline, Week 8

The SDAI is the numerical sum of five outcome parameters: tender joint count (TJC) and swollen joint count (SJC) based on a 28-joint assessment, patient global assessment (PtGA) and physician global assessment (PGA) assessed on a visual analogue scale (VAS) scale ranging from 0 to 10 centimeter (cm), where higher scores=greater affection due to disease activity, and C-reactive protein (CRP) measured in terms of milligram per deciliter (mg/dL). SDAI total score= 0 to 86. SDAI greater than or equal to (\<=) 3.3 indicates disease remission, greater than (\>) 3.4 to 11 = low disease activity, \>11 to 26 = moderate disease activity, and \>26 = high disease activity.

Change From Baseline in Severity of Alopecia Tool (SALT) Score at Week 24
Baseline, Week24

SALT is a quantitative assessment of alopecia areata (AA) severity based on the scalp hair loss. Score range: 0-100%. Higher score indicates more severe disease. Change from baseline is defined as the baseline value minus the value at a specific visit. Positive change from baseline signifies an improvement. Baseline is defined as the last measurement prior to first dosing (Day 1).

Number of Participants With Treatment-emergent Adverse Events (All-causality and Treatment-related) - Single-Blind Extension (SBE) Period
Week 28 up to Week 52

An AE (non-serious and serious) was any untoward medical occurrence in a participant who received study treatment without regard to possibility of causal relationship. Any such events with initial onset or increasing in severity after the first dose of study treatment were counted as treatment-emergent Adverse Event (TEAE). Treatment-related TEAE were determined by investigators. Arms end with "withdrawal Segment" and "retreatment segment" described the same population while in different treatment segment .The reason why count on PF-06700841 differ by 1 participant is that 1 responder directly entered the retreatment segment and skipped the withdrawal segment.

Number of Participants With Treatment-emergent Adverse Events (All-causality and Treatment-related) - Cross-Over Extension (COE) Period
COE day 1 up to end of study

An AE (non-serious and serious) was any untoward medical occurrence in a participant who received study treatment without regard to possibility of causal relationship. Any such events with initial onset or increasing in severity after the first dose of study treatment were counted as treatment-emergent Adverse Event (TEAE). Treatment-related TEAE were determined by investigators.

Number of Participants With Laboratory Abnormalities During SBE Period
Week 28 up to Week 52 for non-responders and responders in the withdrawal segment, AT day 1 up to AT Week 24 for retreatment segment (AT=active treatment)

Following laboratory parameters were assessed against pre-defined abnormality criteria: hematology(Hemoglobin, Hematocrit, RBC count, Reticulocyte count, Platelet count, WBC count with differential, Total neutrophils, Eosinophils, Monocytes, Basophils, Lymphocytes); serum chemistry (BUN and Creatinine, Cystatin C, Creatine Phosphokinase, Glucose , Na+, K+, Cl ,Ca++, Total CO2, AST, ALT, Total Indirect \& Direct Bilirubin, Alkaline phosphatase, Uric acid, Albumin,Total protein, Fasting lipid Profile Panel; urinalysis(pH, Glucose, Protein, Nitrites, Leukocyte esterase, Microscopy culture);Other(HIV, HBsAg, HBcAb, HepB reflex (HbsAB), if applicable, HCVAb, Serum pregnancy test, Urine pregnancy test, FSH, QFT G or other IGRA, or PPD, EBV, CMV, HSV1, HSV2, VZV, Skin swab for herpetiform rash, Skin swab for potential drug related rash).Retest/discontinuation criteria are defined in Protocol Appendix 6.1 and 6.2 respectively.

Numbers of Participants With Specific Clinical Laboratory Abnormalities During COE Period
COE day 1 up to end of study

Following laboratory parameters were assessed against pre-defined abnormality criteria: hematology(Hemoglobin, Hematocrit, RBC count, Reticulocyte count, Platelet count, WBC count with differential, Total neutrophils, Eosinophils, Monocytes, Basophils, Lymphocytes); serum chemistry (BUN and Creatinine, Cystatin C, Creatine Phosphokinase, Glucose , Na+, K+, Cl ,Ca++, Total CO2, AST, ALT, Total Indirect \& Direct Bilirubin, Alkaline phosphatase, Uric acid, Albumin,Total protein, Fasting lipid Profile Panel; urinalysis(pH, Glucose, Protein, Nitrites, Leukocyte esterase, Microscopy culture);Other(HIV, HBsAg, HBcAb, HepB reflex (HbsAB), if applicable, HCVAb, Serum pregnancy test, Urine pregnancy test, FSH, QFT G or other IGRA, or PPD, EBV, CMV, HSV1, HSV2, VZV, Skin swab for herpetiform rash, Skin swab for potential drug related rash).Retest/discontinuation criteria are defined in Protocol Appendix 6.1 and 6.2 respectively.

Single dose: maximum observed concentration (Cmax)
0, 0.25, 0.5, 0.75, 1, 2, 4, 6, 8, 12, 16 and 24 hours after dosing on Day1
Single dose: time to reach maximum concentration (Tmax)
0, 0.25, 0.5, 0.75, 1, 2, 4, 6, 8, 12, 16 and 24 hours after dosing on Day1
Single dose: area under the concentration-time curve from time 0 to infinity (AUCinf)
0, 0.25, 0.5, 0.75, 1, 2, 4, 6, 8, 12, 16 and 24 hours after dosing on Day1
Single dose: area under the concentration-time curve from time 0 to the time of last quantifiable concentration (AUClast)
0, 0.25, 0.5, 0.75, 1, 2, 4, 6, 8, 12, 16 and 24 hours after dosing on Day1
Single dose: terminal half life (t1/2)
0, 0.25, 0.5, 0.75, 1, 2, 4, 6, 8, 12, 16 and 24 hours after dosing on Day1
Single dose:AUC24
0, 0.25, 0.5, 0.75, 1, 2, 4, 6, 8, 12, 16 and 24 hours after dosing on Day1
Single dose: mean residence time (MRT)
0, 0.25, 0.5, 0.75, 1, 2, 4, 6, 8, 12, 16 and 24 hours after dosing on Day1
Single dose: apparent volume of distribution (Vz/F)
0, 0.25, 0.5, 0.75, 1, 2, 4, 6, 8, 12, 16 and 24 hours after dosing on Day1
Single dose: apparent oral clearance (CL/F)
0, 0.25, 0.5, 0.75, 1, 2, 4, 6, 8, 12, 16 and 24 hours after dosing on Day1
Multiple Dose: Cmax
0, 0.25, 0.5, 0.75, 1, 2, 4, 6, 8, 12, 16 and 24 hours after dosing on Day10
Multiple Dose: Tmax
0, 0.25, 0.5, 0.75, 1, 2, 4, 6, 8, 12, 16 and 24 hours after dosing on Day10
Multiple Dose: AUCtau (tau = 24 hours)
0, 0.25, 0.5, 0.75, 1, 2, 4, 6, 8, 12, 16 and 24 hours after dosing on Day10
Multiple Dose: t1/2
0, 0.25, 0.5, 0.75, 1, 2, 4, 6, 8, 12, 16 and 24 hours after dosing on Day10
Multiple Dose: accumulation ratio on AUCtau (Rac)
0, 0.25, 0.5, 0.75, 1, 2, 4, 6, 8, 12, 16 and 24 hours after dosing on Day10
Multiple Dose: accumulation ratio on Cmax(Rac, Cmax)
0, 0.25, 0.5, 0.75, 1, 2, 4, 6, 8, 12, 16 and 24 hours after dosing on Day10
Multiple Dose: lowest concentration observed during the dosing interval (Cmin)
0, 0.25, 0.5, 0.75, 1, 2, 4, 6, 8, 12, 16 and 24 hours after dosing on Day10
Multiple Dose: average concentration at steady state (Cav)
0, 0.25, 0.5, 0.75, 1, 2, 4, 6, 8, 12, 16 and 24 hours after dosing on Day10
Multiple Dose: MRT
0, 0.25, 0.5, 0.75, 1, 2, 4, 6, 8, 12, 16 and 24 hours after dosing on Day10
Multiple Dose: apparent volume of distribution at steady state (Vss/F)
0, 0.25, 0.5, 0.75, 1, 2, 4, 6, 8, 12, 16 and 24 hours after dosing on Day10
Multiple Dose: CL/F
0, 0.25, 0.5, 0.75, 1, 2, 4, 6, 8, 12, 16 and 24 hours after dosing on Day10
Multiple Dose: peak trough fluctuation (PTF)
0, 0.25, 0.5, 0.75, 1, 2, 4, 6, 8, 12, 16 and 24 hours after dosing on Day10
Multiple Dose: peak trough swing (PTS)
0, 0.25, 0.5, 0.75, 1, 2, 4, 6, 8, 12, 16 and 24 hours after dosing on Day10
Multiple Dose: predicted accumulation ratio to estimate linearity (Rss)
0, 0.25, 0.5, 0.75, 1, 2, 4, 6, 8, 12, 16 and 24 hours after dosing on Day10
Number of Participants With Treatment Emergent Treatment-Related Adverse Events (AEs)
From Day1 till Day17
Number of participants with clinically significant change in vital signs from Baseline
From Day1 till Day17
Number of participants with clinically significant abnormalities in 12-lead electrocardiograms (ECGs)
From Day1 till Day17
Number of participants with clinically significant abnormalities in physical examination findings
From Day1 till Day17
Area under the plasma concentration-time profile from time zero extrapolated to infinite time (AUCinf)of PF-06651600
Day 1 pre-dose and at 0.5, 1, 1.5, 2, 3, 4, 6, 12, and 16 hrs, and Day 2, at 24 hours post-dose.
Maximum plasma PF-06651600 concentration (C max)
Day 1 pre-dose and at 0.5, 1, 1.5, 2, 3, 4, 6, 12, and 16 hrs, and Day 2, at 24 hours post-dose.
Cmax (maximum plasma concentration) of PF-06651600
Hour 0, and 0.25, 0.5, 1, 2, 3, 4, 5, 6, 8, 10, 12, 24 hours post post Period 1, Day 1, Period 2, Day 8.
AUC (Area under the curve) of PF-06651600
Hour 0, and 0.25, 0.5, 1, 2, 3, 4, 5, 6, 8, 10, 12, 24 hours post post Period 1, Day 1, Period 2, Day 8.

Area under the plasma concentration-time profile from time 0 extrapolated to infinite time.

Area Under the Curve From Time Zero to Extrapolated Infinite Time (AUCinf) for rosuvastatin
Period 1 (4 days) day 1 and period 2 (11 days) day 8 , 0 (pre-dose), 0.5, 1,2,3,4,5,6,8,10,12,16,24,36,48,and 72 hours post-dose

AUCinf = Area under the plasma concentration versus time curve (AUC) from time zero (pre-dose) to extrapolated infinite time (0-inf). It is obtained from AUC (0-t) plus AUC (t-inf).

Renal clearance (CLr) for rosuvastatin
Period 1 (4 days) day 1 and period 2 (11 days) day 8 , hours: [0-6], [6-12], [12-24], [24-48], and [48-72] post-dose

CLr = total amount of drug collected in urine (Ae) divided by area under the plasma concentration-time profile from time 0 to the time of the last quantifiable concentration (AUClast).

Area Under the Curve From Time Zero to Extrapolated Infinite Time (AUCinf) for EE
predose, 30 minutes and 1, 1.5, 2, 4, 6, 8, 12, 24, 36, 48, 72 and 96 hours post OC dose in Periods 1 and 2

30 micrograms administered as oral OC combination tablet

Area Under the Curve From Time Zero to Extrapolated Infinite Time (AUCinf) for LN
predose, 30 minutes and 1, 1.5, 2, 4, 6, 8, 12, 24, 36, 48, 72 and 96 hours post OC dose in Periods 1 and 2

150 micrograms administered as oral OC combination tablet

Area Under the Plasma Concentration-time Profile From Time 0 to 24 Hours (AUC24) for PF-06651600
Hour 0 (pre-dose) on Days 7, 8 and 9, and hour 0 (pre-dose), 0.5, 1, 2, 3, 4, 6, 8, 12, 14, 24 hours post-dose on Day 10

AUC24 of PF-06651600 pre and post dose.

Maximum Plasma Concentration (Cmax) for PF-06651600
Hour 0 (pre-dose) on Days 7, 8 and 9, and hour 0 (pre-dose), 0.5, 1, 2, 3, 4, 6, 8, 12, 14, 24 hours post-dose on Day 10

Cmax is maximum observed plasma concentration.

Number of subjects reporting overall liking of drug formulation
Baseline through 20 minutes post dose

Overall liking assesses the degree that a participant likes a drug formulation based on sensory attributes experienced by the participant after tasting a product. It is scored based on a measurement of taste questionnaire.

Percentage of subjects reporting overall liking of drug formulation
Baseline through 20 minutes post dose

Overall liking assesses the degree that a participant likes a drug formulation based on sensory attributes experienced by the participant after tasting a product. It is scored based on a measurement of taste questionnaire.

Number of subjects reporting saltiness of drug formulation
Baseline through 20 minutes post dose

Saltiness assesses the degree that a participant experienced this sensory attribute after tasting a drug formulation. It is scored based on a measurement of taste questionnaire

Percentage of subjects reporting saltiness of drug formulation
Baseline through 20 minutes post dose

Saltiness assesses the degree that a participant experienced this sensory attribute after tasting a drug formulation. It is scored based on a measurement of taste questionnaire

Number of subjects reporting bitterness of drug formulation
Baseline through 20 minutes post dose

Bitterness assesses the degree that a participant experienced this sensory attribute after tasting a drug formulation. It is scored based on a measurement of taste questionnaire

Percentage of subjects reporting bitterness of drug formulation
Baseline through 20 minutes post dose

Bitterness assesses the degree that a participant experienced this sensory attribute after tasting a drug formulation. It is scored based on a measurement of taste questionnaire

Number of subjects reporting mouth feel of drug formulation
Baseline through 20 minutes post dose

Mouth feel assesses the degree that a participant experienced this sensory attribute after tasting a drug formulation. It is scored based on a measurement of taste questionnaire

Percentage of subjects reporting mouth feel of drug formulation
Baseline through 20 minutes post dose

Mouth feel assesses the degree that a participant experienced this sensory attribute after tasting a drug formulation. It is scored based on a measurement of taste questionnaire

Number of subjects reporting sourness of drug formulation
Baseline through 20 minutes post dose

Sourness assesses the degree that a participant experienced this sensory attribute after tasting a drug formulation. It is scored based on a measurement of taste questionnaire

Percentage of subjects reporting sourness of drug formulation
Baseline through 20 minutes post dose

Sourness assesses the degree that a participant experienced this sensory attribute after tasting a drug formulation. It is scored based on a measurement of taste questionnaire

Number of subjects reporting tongue/mouth burn from drug formulation
Baseline through 20 minutes post dose

Tongue/mouth burn assesses the degree that a participant experienced this sensory attribute after tasting a drug formulation. It is scored based on a measurement of taste questionnaire

Percentage of subjects reporting tongue/mouth burn from drug formulation
Baseline through 20 minutes post dose

Tongue/mouth burn assesses the degree that a participant experienced this sensory attribute after tasting a drug formulation. It is scored based on a measurement of taste questionnaire

Number of subjects reporting formulation preference
Baseline through 20 minutes post dose

Formulation preference assesses the degree that a participant prefers a drug formulation based on sensory attributes experienced by the participant after tasting a product. It is scored based on a measurement of taste questionnaire.

Percentage of subjects reporting formulation preference
Baseline through 20 minutes post dose

Formulation preference assesses the degree that a participant prefers a drug formulation based on sensory attributes experienced by the participant after tasting a product. It is scored based on a measurement of taste questionnaire.

Single dose Area under the curve from time zero to infinity [AUC (0-inf)] of PF-06651600
0, 0.5, 1, 2, 4, 6, 8, 12, 16, 24 and 48 hours

Area under the plasma concentration versus time curve (AUC) from time zero (pre-dose) to extrapolated infinity.

Maximum observed plasma concentration of PF-06651600
0, 0.5, 1, 2, 4, 6, 8, 12, 16, 24 and 48 hours

Peak concentration of PF-06651600

single dose Area under the curve at last quantifiable infinity time of midazolam
Hour 0, 0,5, 1, 2, 4, 6, 8, 12, 16, 24 hours post-dose
Single dose Area under the Curve from time 0 to 72 hours post-dose of efavirenz
hour 0, 0,5, 1, 2, 4, 6, 8, 12, 16, 24, 48, 72 hours post-dose
Number of Participants With Treatment-Emergent Adverse Events (AEs), Serious Adverse Events (SAEs) and Discontinuation Due to AEs
Baseline up to Day 45
Change From Baseline in 12-Lead Electrocardiogram (ECG) Parameters (PR Interval, QRS interval, QT Interval, QTC Interval, heart rate)
Baseline, 1 hour post-dose on Day 1 and 10
Change From Baseline in Vital Signs (Blood Pressure, Pulse Rate, Oral Temperature)
Baseline, Day 1, 10, 12 and 28
Number of Participants With Change From Baseline in Physical Examinations
Baseline up to Day 28
Number of Participants With Laboratory Abnormalities
Baseline up to Day 28
Area Under the Curve From Time Zero to Extrapolated Infinite Time (AUCinf) for PF-06651600
0, 0.25, 0.5, 1, 2, 4, 6, 8, 12, 16, 24, 36, 48 hours post dose

Area Under the Curve From Time Zero to Extrapolated Infinite Time (AUCinf)

Area Under the Curve From Time Zero to Last Quantifiable Concentration (AUClast) for PF-06651600
0, 0.25, 0.5, 1, 2, 4, 6, 8, 12, 16, 24, 36, 48 hours post dose

Area Under the Curve From Time Zero to Last Quantifiable Concentration (AUClast)

Time to Reach Maximum Observed Plasma Concentration (Cmax) for PF-06651600
0, 0.25, 0.5, 1, 2, 4, 6, 8, 12, 16, 24, 36, 48 hours post dose

Time to Reach Maximum Observed Plasma Concentration (Cmax)

Secondary Endpoints

Main Study: Number of Participants With Treatment Emergent Adverse Events (TEAEs) Until End of Study
From start of study intervention (Day 1) until end of study
Main Study: Number of Participants With Serious Adverse Events (SAEs) and Adverse Events (AEs) Leading to Discontinuation Until End of Study
From start of study intervention (Day 1) until end of study
Main Study: Number of Participants With Clinically Significant Abnormalities in Vital Signs Until End of Study
From start of study intervention (Day 1) until end of study
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Study Design & Arms

AllocationNON_RANDOMIZED
MaskingNONE
ModelPARALLEL
PurposeTREATMENT

Treatment Arms

ArmTypeDescription
Treatment sequence 1EXPERIMENTALParticipants who did not previously receive study intervention in either study B7931005 or B7981015 will receive 200 milligrams (mg) PF-06651600, given as four 50 mg tablets once daily (QD) for 1 month, followed by 50 mg PF-06651600 tablet or capsule given QD for 59 months. Patients participating in the vaccine sub-study will receive the 2 vaccines or one of the 2 vaccines at the vaccine sub-study Day 1, which will occur at a scheduled study visit on or after the Month 9 visit and prior to or on the Month 56 visit of the main B7981032 study.
Treatment sequence 2EXPERIMENTALParticipants who previously received study intervention in either study B7931005 or B7981015 will receive 50 mg PF-06651600 tablet or capsule given QD for 59 months. Patients participating in the vaccine sub-study will receive the 2 vaccines or 1 of the 2 vaccines at the vaccine sub-study Day 1, which will occur at a scheduled study visit on or after the Month 6 visit and prior to or on the Month 56 visit of the main B7981032 study.
PF-06651600 (Ritlecitinib)EXPERIMENTAL200 mg once-daily for 8 weeks and then 100 mg once daily for the remaining 40 weeks
Sequence AEXPERIMENTALInduction dose given once daily (QD) for 4 weeks followed by maintenance dose #1 given QD for 44 weeks
Sequence BEXPERIMENTALInduction dose given QD for 4 weeks followed by maintenance dose #2 given QD for 44 weeks
Sequence CEXPERIMENTALMaintenance dose #1 given QD for 48 weeks
Sequence DEXPERIMENTALMaintenance dose #2 given QD for 48 weeks
Sequence EEXPERIMENTALMaintenance dose #3 given QD for 48 weeks
Sequence FEXPERIMENTALPlacebo given QD for 24 weeks followed by induction dose given QD for 4 weeks then maintenance dose #1 given QD for 20 weeks
Sequence GEXPERIMENTALPlacebo given QD for 24 weeks followed by maintenance dose #1 given QD for 24 weeks
Cohort 1EXPERIMENTALInduction dose 1 given once a day(QD) for 4 weeks followed by maintenance dose A given QD for 20 weeks
Cohort 2EXPERIMENTALInduction dose 2 given QD for 4 weeks followed by maintenance dose A given QD for 20 weeks
Cohort 3EXPERIMENTALMaintenance dose A given QD for 24 weeks
Cohort 4EXPERIMENTALMaintenance dose B given QD for 24 weeks
Cohort 5EXPERIMENTALMaintenance dose C given QD for 24 weeks
Cohort 6PLACEBO_COMPARATORPlacebo given QD for 24 weeks
Extension Cohort 1EXPERIMENTAL4 week drug holiday (no drug given) followed by PF-06700841 oral tablet QD for 20 weeks
Extension Cohort 2EXPERIMENTALInduction dose 1 given QD for 4 weeks followed by maintenance dose A given QD for 20 weeks in conjunction with narrow band UVB phototherapy
Extension Cohort 3EXPERIMENTALInduction dose 1 given QD for 4 weeks followed by maintenance dose A given QD for 20 weeks
Extension Cohort 4EXPERIMENTALMaintenance dose A given QD for 24 weeks
Extension Cohort 5EXPERIMENTALMaintenance dose B given QD for 24 weeks
Extension Cohort 6NO_INTERVENTIONObservation period for 24 weeks
PF-06700841 or placeboEXPERIMENTAL -
PF-06651600 or placeboEXPERIMENTAL -
PF-06651600EXPERIMENTALStudy Drug
PlaceboPLACEBO_COMPARATORPlacebo
Cohort placeboPLACEBO_COMPARATORplacebo
Treatment Sequence 3EXPERIMENTALPF-06651600 100 mg Tablets (fasted, Period 1), followed by Capsules (fasted, Period 2).
Treatment Sequence 4EXPERIMENTALPF-06651600 100 mg Capsules (fasted, Period 1), followed by Tablets (fasted, Period 2).
Rifampin and PF-06651600 DDIEXPERIMENTALIn Period 1, participants will receive a single oral 50 mg dose of PF-06651600. In Period 2, participants will receive rifampin 600 mg QD in the mornings of Day 1 to Day 7, in the morning of Day 8 participants will be administered with rifampin 600 mg 2 hour prior to administration of a single 50 mg oral dose of PF-06651600.
PF-06651600 and RosuvastatinEXPERIMENTALPeriod 1 is 4 days in length. On Day 1 of Period 1 participants will receive a single dose of Rosuvastatin 10 mg given as a tablet orally. Period 2 is 11 days in length and will immediately follow Period 1 with no washout. In Period 2, participants will be dosed with oral 200 mg PF-06651600 once-daily (QD) for 7 days. On Day 8 of Period 2, a single dose of 10 mg Rosuvastatin oral tablet will be administered following administration of the 200-mg dose of PF-06651600. Dosing with oral 200 mg PF-06651600 QD will continue until Day 10 of Period 2.
Sequence 1EXPERIMENTALIn Treatment Sequence 1, period 1, participants will be dosed with a single administration of oral contraceptive (OC). Participants will continue directly into Period 2 where they will receive PF-06651600 PO for 9 days followed by administration of a single dose of OC on the morning of Day 10.
Sequence 2EXPERIMENTALIn Treatment Sequence 2, Period 1, participants will be dosed with PF-06651600 PO QD for 9 days and administered a single dose of OC on the morning of Day 10. After a washout period of at least 10 days, participants will continue into Period 2 and will receive an additional single dose of OC.
PF-06651600 Moderate Hepatic ImpairmentEXPERIMENTALThis arm includes participants with moderate hepatic impairment who will receive oral doses of PF-06651600 30 mg on Day 1 through Day 10.
PF-06651600 Healthy participantsEXPERIMENTALThis arm includes healthy adult participants who will receive oral doses of PF-06651600 30 mg on Day 1 through Day 10.
PF-06651600 Mild Hepatic ImpairmentEXPERIMENTALThis arm is in Part 2 which will be conducted if the decision criterion to proceed to Part 2 is met. The arm includes participants with mild hepatic impairment who will receive oral doses of PF-06651600 30 mg on Day 1 through Day 10.
PF-06651600 Treatment AEXPERIMENTALActive pharmaceutical ingredient (API)solution in water
PF-06651600 Treatment BEXPERIMENTALAPI in sweetened solution
PF-06651600 Treatment CEXPERIMENTALAPI blend suspension in water
PF-06651600 Treatment DEXPERIMENTALAPI blend suspension in apple sauce
Bitrex (Registered) Treatment EOTHERPositive control for bitterness
PF-06651600 treatment armEXPERIMENTALThis arm includes two treatment periods. Period 1-Single oral dose of PF-06651600 30 mg as tablets on Day 1 followed by Period 2 in which itraconazole 200 mg (oral solution) is given for 5 days. On Day 4 of Period 2, a single oral dose of PF-06651600 30 mg is given with itraconazole
midazolam/efavirenzEXPERIMENTAL -
PF-06651600/midazolam/efavirenzEXPERIMENTAL -
Cohort 1: PF-06651600EXPERIMENTALSingle dose of PF-06651600 50 mg tablet (under fasted condition and following high fat meal) and 50 mg oral formulation (under fasted condition) to evaluate bioavailability.
Cohort 2: PF-06651600EXPERIMENTALSingle dose of PF-06651600 50 mg tablet (under fasted condition and following high fat meal) and 50 mg oral formulation (under fasted condition) to evaluate bioavailability.
Cohort 3: PF-06651600EXPERIMENTALSingle dose of PF-06651600 50 mg tablet (under fasted condition and following high fat meal) and 50 mg oral formulation (under fasted condition) to evaluate bioavailability.
Cohort 4: PF-06651600EXPERIMENTALSingle dose of PF-06651600 50 mg tablet (under fasted condition and following high fat meal) and 50 mg oral formulation (under fasted condition) to evaluate bioavailability.
Cohort 5: PF-06651600EXPERIMENTALSingle dose of PF-06651600 50 mg tablet (under fasted condition and following high fat meal) and 50 mg oral formulation (under fasted condition) to evaluate bioavailability.
Cohort 6: PF-06651600EXPERIMENTALSingle dose of PF-06651600 50 mg tablet (under fasted condition and following high fat meal) and 50 mg oral formulation (under fasted condition) to evaluate bioavailability.

Interventions

NameTypeDescription
PF-06651600DRUG50 mg oral tablets/capsules
Tetanus and diphtheria toxoids and acellular pertussis (Tdap) vaccineBIOLOGICALSingle intramuscular injection administered to patients participating in the vaccine sub-study
Meningococcal (groups A, C, W-135 and Y [ACWY]) oligosaccharide diphtheria CRM197 conjugate vaccineBIOLOGICALSingle intramuscular injection administered to patients participating in the vaccine sub-study
PF-06651600 Induction DoseDRUGOral tablets taken once daily (QD)
PF-06651600 Maintenance Dose #1DRUGOral tablets taken QD
PF-06651600 Maintenance Dose #2DRUGOral tablets taken QD
PF-06651600 Maintenance Dose #3DRUGOral tablets taken QD
PlaceboDRUGOral tablets taken QD
PF06700841DRUGOral tablet taken QD
narrow-band UVB phototherapyDEVICEPhototherapy will be combined with PF-06651600
PF-06651600 PlaceboDRUG12 weeks, followed by PF-06651600, 50 mg once daily (QD) for 52 weeks
Placebo PF-06700841DRUG12 weeks, followed by PF-06700841, 30 mg QD for 52 weeks
PF-06700841DRUG60 mg QD for 12 weeks followed by 30 mg QD for up to 52 weeks
RifampinDRUG600 mg provided as two 300 mg capsules.
RosuvastatinDRUG10 mg oral tablet
Ethinyl estradiol (EE) and levonorgestrel(LN)DRUGOral tablet containing 30 ug EE and 150 ug of LN
PF-06651600 30 mgDRUGPF-06651600 in 10 mg oral tablets will be administered on days 1 to 10.
PF-06651600 20 mgDRUGPF-06651600 in four (4) different oral formulations will be administered in different periods.
Bitrex solutionOTHERBitrex solution at 0.5 ppm will be included in the treatment sequence together with the four PF-06651600 formulations.
PF-06651600 10 mg tabletsDRUGOn Day 1 in Period 1, a single oral dose of 30 mg (3 x 10 mg tablets) will be administered. On Day 4 of Period 2, a single oral dose of 30 mg (3 x 10 mg tablets) will be administered after itraconazole.
Itraconazole Solution 200 mgDRUGItraconazole 200 mg will be administered as 20 mL (10 mg/mL) oral solution once daily on Days 1-5 in Period 2. On Day 4 of Period 2, co-administration of itraconazole 200 mg and PF-06651600 30 mg will occur. Itraconazole will be administered first followed by PF-06651600 tablets.
midazolamDRUGsingle administration of midazolam 2 mg oral solution
efavirenzDRUGsingle administration of efavirenz 50 mg capsule
Ethinyl estradiol (EE) and levonogestrel (LN)DRUGSingle dose of Oral tablet containing 30 ug EE and 150 ug of LN
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Eligibility Criteria

Age Range12 Years to N/A
SexALL
Healthy VolunteersNo
Study Sites144

Inclusion Criteria- For de novo participants and participants from Study B7931005 and B7981015 with \>30 days between first visit in B7981032 and last dose in the prior study: * Clinical diagnosis of alopecia areata (AA) with no other cause of hair loss. Androgenetic alopecia coexistent with AA is...

Countries:United StatesArgentinaAustraliaCanadaChileChinaColombiaCzechiaGermanyJapanMexicoPolandRussiaSouth KoreaSpainTaiwanUnited KingdomHungaryBelgiumItalyAustriaBosnia and HerzegovinaCroatiaGeorgiaLebanonSaudi ArabiaSerbiaSlovakiaSouth AfricaSwitzerlandTunisiaTurkey (Türkiye)UkraineUnited Arab EmiratesBulgaria
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Recent Changes (Last 90 Days)

MEDIUMAug 15, 2026NCT05549934TRIAL_REMOVED: changed
MEDIUMAug 15, 2026NCT05549934TRIAL_REMOVED: changed
MEDIUMAug 15, 2026NCT05549934TRIAL_REMOVED: changed

Frequently asked questions about PF-06651600

What is PF-06651600 used for?

PF-06651600 is an investigational small molecule being studied for the treatment of alopecia areata and moderate to severe Crohn's disease. Clinical trials have also included healthy subjects, individuals with hepatic impairment, and healthy females. It is in clinical development and is not approved by the FDA.

Who makes PF-06651600?

PF-06651600 is being developed by Pfizer, Inc., a biopharmaceutical company traded on the New York Stock Exchange under the ticker symbol PFE. Pfizer has sponsored multiple clinical trials evaluating the drug for dermatological and gastrointestinal conditions.

What phase is PF-06651600 in?

PF-06651600 has completed Phase 2 and Phase 3 clinical trials. The completed trials include Phase 2 studies in alopecia areata and Crohn's disease, as well as a Phase 3 long-term study in alopecia areata. The drug remains investigational and is not FDA approved.

What clinical trials is PF-06651600 in?

PF-06651600 has been studied in four completed clinical trials. These include NCT02974868 and NCT03732807 for alopecia areata, NCT03395184 for moderate to severe Crohn's disease, and NCT04006457, a long-term Phase 3 study for alopecia areata. All trials have been completed.

Is PF-06651600 the same as ritlecitinib?

PF-06651600 is also known as ritlecitinib. It is an investigational small molecule developed by Pfizer for conditions such as alopecia areata and Crohn's disease. The drug has been evaluated in multiple Phase 2 and Phase 3 clinical trials.