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SB-525

Phase 2

Hemophilia A | Monoclonal antibody | Hematology |Pfizer, Inc.|Last Updated: Sep 30, 2025

Success Probability

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Market & Valuation

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Trial Design

UNCONTROLLEDDMC
Total Trials1
Total Enrollment13

FDA Designations

No designations recorded

Clinical trial landscape

SB-525 · 1 trial · 1 indication

Phase 2 1
NCT03061201A Study of Recombinant AAV2/6 Human Factor 8 Gene Therapy SB-525 (PF-07055480) in Subjects With Severe Hemophilia AHemophilia A
COMPLETED13 Analytics
PHASE2COMPLETED
A Study of Recombinant AAV2/6 Human Factor 8 Gene Therapy SB-525 (PF-07055480) in Subjects With Severe Hemophilia A
Hemophilia AUnlock trial analytics

Study Endpoints

Primary Endpoints

Number of Participants With Adverse Events (AEs) and Serious Adverse Events (SAEs)
From Baseline (1 week prior to infusion) up to 5 years post-infusion (approximately 5 Years)

An AE was any untoward medical occurrence in a participant or clinical study participant, temporally associated with the use of study intervention, whether or not considered related to the study intervention. An AE can therefore be any unfavorable and unintended sign (including an abnormal laboratory finding), symptom, or disease (new or exacerbated) temporally associated with the use of study intervention. An SAE was defined as any untoward medical occurrence that, at any dose, met one or more of the criteria as follows: death, life-threatening, required inpatient hospitalization or prolongation of existing hospitalization, resulted in persistent or significant disability/incapacity, congenital anomaly/birth defect and other situations per protocol. AEs included both SAEs and all non-SAEs.

Central FVIII Activity Levels by Chromogenic Assay at Year 1 (Week 52)
At Year 1 (Week 52)

FVIII activity levels were assessed using chromogenic and one-stage clotting assay and which were analyzed in the central laboratory. In this outcome measure results by chromogenic assay are reported.

Central FVIII Activity Levels by Chromogenic Assay at Year 2 (Week 104)
At Year 2 (Week 104)

FVIII activity levels were assessed using chromogenic and one-stage clotting assay and which were analyzed in the central laboratory. In this outcome measure results by chromogenic assay are reported.

Central FVIII Activity Levels by Chromogenic Assay at Year 3 (Week 156)
At Year 3 (Week 156)

FVIII activity levels were assessed using chromogenic and one-stage clotting assay and which were analyzed in the central laboratory. In this outcome measure results by chromogenic assay are reported.

Central FVIII Activity Levels by Chromogenic Assay at Year 4 (Week 208)
At Year 4 (Week 208)

FVIII activity levels were assessed using chromogenic and one-stage clotting assay and which were analyzed in the central laboratory. In this outcome measure results by chromogenic assay are reported.

Central FVIII Activity Levels by Chromogenic Assay at Year 5 (Week 260)
At Year 5 (Week 260)

FVIII activity levels were assessed using chromogenic and one-stage clotting assay and which were analyzed in the central laboratory. In this outcome measure results by chromogenic assay are reported.

Central FVIII Activity Levels by One-Stage Clotting Assay at Year 1 (Week 52)
At Year 1 (Week 52)

FVIII activity levels were assessed using chromogenic and one-stage clotting assay and which were analyzed in the central laboratory. In this outcome measure results by one-stage clotting assay are reported.

Central FVIII Activity Levels by One-Stage Clotting Assay at Year 2 (Week 104)
At Year 2 (Week 104)

FVIII activity levels were assessed using chromogenic and one-stage clotting assay and which were analyzed in the central laboratory. In this outcome measure results by one-stage clotting assay are reported.

Central FVIII Activity Levels by One-Stage Clotting Assay at Year 3 (Week 156)
At Year 3 (Week 156)

FVIII activity levels were assessed using chromogenic and one-stage clotting assay and which were analyzed in the central laboratory. In this outcome measure results by one-stage clotting assay are reported.

Central FVIII Activity Levels by One-Stage Clotting Assay at Year 4 (Week 208)
At Year 4 (Week 208)

FVIII activity levels were assessed using chromogenic and one-stage clotting assay and which were analyzed in the central laboratory. In this outcome measure results by one-stage clotting assay are reported.

Central FVIII Activity Levels by One-Stage Clotting Assay at Year 5 (Week 260)
At Year 5 (Week 260)

FVIII activity levels were assessed using chromogenic and one-stage clotting assay and which were analyzed in the central laboratory. In this outcome measure results by one-stage clotting assay are reported.

Geometric Mean of Central FVIII Activity Levels for Cohort 4 by Chromogenic Assay at Yearly Interval 1 (Week 9 Through Week 53)
Year 1 (Week 9 through Week 53)

FVIII activity levels were analyzed in the central laboratory using chromogenic and one-stage clotting assay. In this outcome measure FVIII activity levels were assessed by chromogenic assay. As pre-specified, for each participant geometric mean of central FVIII activity levels was calculated of all eligible FVIII activity measurements for each yearly interval (for this outcome measure: Yearly Interval 1 included assessments from Week 9 through Week 53). Following this mean and standard deviation as summary statistics across all evaluable participants was calculated and is reported as data for this outcome measure.

Geometric Mean of Central FVIII Activity Levels for Cohort 4 by Chromogenic Assay at Yearly Interval 2 (Week 54 Through Week 108)
Year 2 (Week 54 through Week 108)

FVIII activity levels were analyzed in the central laboratory using chromogenic and one-stage clotting assay. In this outcome measure FVIII activity levels were assessed by chromogenic assay. As pre-specified, for each participant geometric mean of central FVIII activity levels was calculated of all eligible FVIII activity measurements for each yearly interval (for this outcome measure: Yearly Interval 2 included assessments from Week 54 through Week 108). Following this mean and standard deviation as summary statistics across all evaluable participants was calculated and is reported as data for this outcome measure.

Geometric Mean of Central FVIII Activity Levels for Cohort 4 by Chromogenic Assay at Yearly Interval 3 (Week 109 Through Week 160)
Year 3 (Week 109 through Week 160)

FVIII activity levels were analyzed in the central laboratory using chromogenic and one-stage clotting assay. In this outcome measure FVIII activity levels were assessed by chromogenic assay. As pre-specified, for each participant geometric mean of central FVIII activity levels was calculated of all eligible FVIII activity measurements for each yearly interval (for this outcome measure: Yearly Interval 3 included assessments from Week 109 through Week 160). Following this mean and standard deviation as summary statistics across all evaluable participants was calculated and is reported as data for this outcome measure.

Geometric Mean of Central FVIII Activity Levels for Cohort 4 by Chromogenic Assay at Yearly Interval 4 (Week 161 Through Week 212)
Year 4 (Week 161 through Week 212)

FVIII activity levels were analyzed in the central laboratory using chromogenic and one-stage clotting assay. In this outcome measure FVIII activity levels were assessed by chromogenic assay. As pre-specified, for each participant geometric mean of central FVIII activity levels was calculated of all eligible FVIII activity measurements for each yearly interval (for this outcome measure: Yearly Interval 4 included assessments from Week 161 through Week 212). Following this mean and standard deviation as summary statistics across all evaluable participants was calculated and is reported as data for this outcome measure.

Geometric Mean of Central FVIII Activity Levels for Cohort 4 by Chromogenic Assay at Yearly Interval 5 (Week 213 Through Week 264)
Year 5 (Week 213 through Week 264)

FVIII activity levels were analyzed in the central laboratory using chromogenic and one-stage clotting assay. In this outcome measure FVIII activity levels were assessed by chromogenic assay. As pre-specified, for each participant geometric mean of central FVIII activity levels was calculated of all eligible FVIII activity measurements for each yearly interval (for this outcome measure: Yearly Interval 5 included assessments from Week 213 through Week 264). Following this mean and standard deviation as summary statistics across all evaluable participants was calculated and is reported as data for this outcome measure.

Geometric Mean of Central FVIII Activity Levels for Cohort 4 by One-Stage Clotting Assay at Yearly Interval 1 (Week 9 Through Week 53)
Year 1 (Week 9 through Week 53)

FVIII activity levels were analyzed in the central laboratory using chromogenic and one-stage clotting assay. In this outcome measure FVIII activity levels were assessed by one-stage clotting assay. As pre-specified, for each participant geometric mean of central FVIII activity levels was calculated of all eligible FVIII activity measurements for each yearly interval (for this outcome measure: Yearly Interval 1 included assessments from Week 9 through Week 53). Following this mean and standard deviation as summary statistics across all evaluable participants was calculated and is reported as data for this outcome measure.

Geometric Mean of Central FVIII Activity Levels for Cohort 4 by One-Stage Clotting Assay at Yearly Interval 2 (Week 54 Through Week 108)
Year 2 (Week 54 through Week 108)

FVIII activity levels were analyzed in the central laboratory using chromogenic and one-stage clotting assay. In this outcome measure FVIII activity levels were assessed by one-stage clotting assay. As pre-specified, for each participant geometric mean of central FVIII activity levels was calculated of all eligible FVIII activity measurements for each yearly interval (for this outcome measure: Yearly Interval 2 included assessments from Week 54 through Week 108). Following this mean and standard deviation as summary statistics across all evaluable participants was calculated and is reported as data for this outcome measure.

Geometric Mean of Central FVIII Activity Levels for Cohort 4 by One-Stage Clotting Assay at Yearly Interval 3 (Week 109 Through Week 160)
Year 3 (Week 109 through Week 160)

FVIII activity levels were analyzed in the central laboratory using chromogenic and one-stage clotting assay. In this outcome measure FVIII activity levels were assessed by one-stage clotting assay. As pre-specified, for each participant geometric mean of central FVIII activity levels was calculated of all eligible FVIII activity measurements for each yearly interval (for this outcome measure: Yearly Interval 3 included assessments from Week 109 through Week 160). Following this mean and standard deviation as summary statistics across all evaluable participants was calculated and is reported as data for this outcome measure.

Geometric Mean of Central FVIII Activity Levels for Cohort 4 by One-Stage Clotting Assay at Yearly Interval 4 (Week 161 Through Week 212)
Year 4 (Week 161 through Week 212)

FVIII activity levels were analyzed in the central laboratory using chromogenic and one-stage clotting assay. In this outcome measure FVIII activity levels were assessed by one-stage clotting assay. As pre-specified, for each participant geometric mean of central FVIII activity levels was calculated of all eligible FVIII activity measurements for each yearly interval (for this outcome measure: Yearly Interval 4 included assessments from Week 161 through Week 212). Following this mean and standard deviation as summary statistics across all evaluable participants was calculated and is reported as data for this outcome measure.

Geometric Mean of Central FVIII Activity Levels for Cohort 4 by One-Stage Clotting Assay at Yearly Interval 5 (Week 213 Through Week 264)
Year 5 (Week 213 through Week 264)

FVIII activity levels were analyzed in the central laboratory using chromogenic and one-stage clotting assay. In this outcome measure FVIII activity levels were assessed by one-stage clotting assay. As pre-specified, for each participant geometric mean of central FVIII activity levels was calculated of all eligible FVIII activity measurements for each yearly interval (for this outcome measure: Yearly Interval 5 included assessments from Week 213 through Week 264). Following this mean and standard deviation as summary statistics across all evaluable participants was calculated and is reported as data for this outcome measure.

Secondary Endpoints

Total Annualized Bleeding Rate (ABR)
Pre-screening period: 12 months prior to screening; Post-infusion period: 3 weeks post-infusion up to date of day before start of prophylaxis or date of data cut or conclusion date, whichever was earlier (maximum up to 5 years)
Total ABR by Severity
Post-infusion period: 3 weeks post-infusion up to date of day before start of prophylaxis or date of data cut or conclusion date, whichever was earlier (maximum up to 5 years)
Annualized Infusion Rate (AIR)
Pre-infusion period: 30 days before screening up to pre-infusion (approximately up to 3.23 months); post-infusion period: 3 weeks post-infusion up to up to date of data cut or conclusion date (maximum up to 5 years)
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Study Design & Arms

AllocationNA
MaskingNONE
ModelSEQUENTIAL
PurposeTREATMENT

Treatment Arms

ArmTypeDescription
Sequential dose escalationEXPERIMENTALSB-525 (PF-07055480) is administered as a single infusion

Interventions

NameTypeDescription
SB-525 (PF-07055480)BIOLOGICALSingle dose of investigational product SB-525 (PF-07055480)
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Eligibility Criteria

Age Range18 Years to N/A
SexMALE
Healthy VolunteersNo
Study Sites22

Inclusion Criteria: * Male ≥18 years of age * Severe hemophilia A (past evidence of circulating FVIII activity of \< 1% normal) * Treated or exposed to FVIII concentrates or cryoprecipitate for at least 150 exposure days * ≥12 bleeding episodes if receiving on-demand therapy over the preceding 12 m...

Countries:United States
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Frequently asked questions about SB-525

What is SB-525 used for?

SB-525 is an investigational gene therapy being developed for the treatment of Hemophilia A. It is designed to address the underlying genetic cause of the condition. The drug is currently in Phase 2 clinical development and has been studied in a completed clinical trial.

Who makes SB-525?

SB-525 is being developed by Pfizer, Inc. (NYSE: PFE). The company is conducting clinical research on this investigational therapy for Hemophilia A. As of the latest data, SB-525 is in Phase 2 development.

What phase is SB-525 in?

SB-525 is in Phase 2 clinical development. It is an investigational drug and has not been approved by regulatory authorities. A Phase 2 clinical trial of SB-525 has been completed, and the drug remains under investigation for Hemophilia A.

What clinical trials is SB-525 in?

SB-525 has been studied in one clinical trial, identified as NCT03061201. This was a Phase 2 study titled 'A Study of Recombinant AAV2/6 Human Factor 8 Gene Therapy SB-525 (PF-07055480) in Subjects With Severe Hemophilia A.' The trial was completed and enrolled 13 male participants aged 18 years and older in the United States.

Is SB-525 the same as PF-07055480?

Yes, SB-525 is also known as PF-07055480. In clinical trial records, the drug is referred to by both names. The Phase 2 study of SB-525, NCT03061201, explicitly lists PF-07055480 as an alternative name for the investigational gene therapy.