Hemophilia APhase 2NCT03061201

A Study of Recombinant AAV2/6 Human Factor 8 Gene Therapy SB-525 (PF-07055480) in Subjects With Severe Hemophilia A

A Phase 2 study testing SB-525 (PF-07055480) in people with Hemophilia A, run by Pfizer at 22 sites in United States.

Completed

Finished. The study has ended and is not enrolling. Results may be posted on the official record.

Trial summary

The purpose of the study is to evaluate the safety, tolerability and time-course profile of FVIII activity after dosing with SB-525 (PF-07055480) Read more about this study

Who is it for?: Ages 18 years and older, men only
Conditions the study is for: Hemophilia A
What is being tested?: SB-525 (PF-07055480)
Type of treatment: Injection or infusion
Could I receive a placebo?: No, everyone receives an active treatment
How many people: 13 participants
Where: 22 sitesUnited States
Study dates: 21 Jun 2017to 16 Jul 2024
Phase: Phase 2
Are there results?: Yes, posted in the registrySummary in the doctors' view

Key requirements

Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.

Ages 18 years and older
Men only
No healthy volunteers
Adult, Older adult

Who may be able to join

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 months
Agree to use double barrier contraceptive until at least 3 consecutive semen samples are negative for AAV 2/6 after SB-525 infusion

Who cannot join

Presence of neutralizing antibodies
Current inhibitor, or history of FVIII inhibitor (except for transient low titer inhibitor detected in childhood)
History of hypersensitivity response to FVIII
History of Hepatitis B or HIV-1/2 infection
History of Hepatitis C, unless viral assays in two samples, collected at least 6 months apart, are negative
Evidence of any bleeding disorder in addition to hemophilia A

Show all 10Show fewer

Markers of hepatic inflammation or overt or occult cirrhosis
History of chronic renal disease or creatinine ≥ 1.5 mg/dL
Presence of liver mass on magnetic resonance imaging (MRI), or, positive alpha fetoprotein
Presence of > grade 2 liver fibrosis on elastography for subjects with history of treated Hepatitis C or suspicion of chronic liver disease

Trial locations and contacts

22 sites in 1 country.

City, postcode or hospital

22 sites in 1 country

United States22 sites

Emory University School of Medicine
Atlanta, Georgia, 30322
City of Hope Medical Center
Duarte, California, 91010
Arkansas Children's Hospital
Little Rock, Arkansas, 72202
University Of Miami Hospital and Clinics/Sylvester Comprehensive Cancer Center
Miami, Florida, 33136
Vanderbilt University Medical Center Clinical Research Center
Nashville, Tennessee, 37212-8646
Vanderbilt Hemostasis Treatment Clinic
Nashville, Tennessee, 37232
Vanderbilt Hemostasis-Thrombosis Clinic
Nashville, Tennessee, 37232
Hemophilia Center of Western PA
Pittsburgh, Pennsylvania, 15213
UPMC Montefiore Clinical and Translational Research Center
Pittsburgh, Pennsylvania, 15213
UPMC, Investigational Drug Service
Pittsburgh, Pennsylvania, 15213
Midtown Ambulatory Care Center
Sacramento, California, 95817
UC Davis Ambulatory Care Clinic
Sacramento, California, 95817
UC Davis Comprehensive Cancer Center
Sacramento, California, 95817
UC Davis CTSC Clinical Research Center
Sacramento, California, 95817
UC Davis Hemophilia Treatment Center
Sacramento, California, 95817
UC Davis Investigational Drug Services Pharmacy
Sacramento, California, 95817
UC Davis Medical Center
Sacramento, California, 95817
University of California, San Francisco - Investigational Drug Service (IDS) Pharmacy
San Francisco, California, 94143-0622
University of California, San Francisco - Outpatient Hematology Clinic
San Francisco, California, 94143
University of California, San Francisco -Moffitt Hospital
San Francisco, California, 94143
Washington Institute for Coagulation
Seattle, Washington, 98101
USF Health Morsani Center For Advanced Healthcare
Tampa, Florida, 33612

Other trials in United States

About this study

Official title: A PHASE 1/2, OPEN-LABEL, ADAPTIVE, DOSE-RANGING STUDY TO ASSESS THE SAFETY AND TOLERABILITY OF SB-525 (PF-07055480) (RECOMBINANT AAV2/6 HUMAN FACTOR 8 GENE THERAPY) IN ADULT SUBJECTS WITH SEVERE HEMOPHILIA A

The purpose of the study is to evaluate the safety, tolerability and time-course profile of FVIII activity after dosing with SB-525 (PF-07055480)

Read the detailed description

The proposed clinical study uses a recombinant adeno-associated virus 2/6 (AAV2/6) vector encoding the cDNA for the B-domain deleted human F8 (hF8). The secreted FVIII has the same amino acid sequence as approved recombinant anti hemophilic factors (Refacto® and Xyntha®). The SB-525 (PF-07055480) vector encodes a liver-specific promotor module and AAV2/6 exhibits liver tropism, thus providing the potential for long-term hepatic production of FVIII in hemophilia A subjects.

The constant production of FVIII after a single SB-525 (PF-07055480) administration may provide potential benefit in durable protection against bleeding and the complications thereof without lifelong repetitive IV factor replacement administration.

Conditions: Hemophilia A
Being tested: SB-525 (PF-07055480)
Medical subject headings: Hemophilia A

What participants receive

What participants receive. In a randomised study each person is assigned to one group by chance.

SB-525 (PF-07055480)Biological
Single dose of investigational product SB-525 (PF-07055480)

Study groups in NCT03061201
Study group	Role	What they receive
Sequential dose escalation	Experimental	SB-525 (PF-07055480) is administered as a single infusion Receives: Biological: SB-525 (PF-07055480)

What is being measured

The primary outcome is the main question the study is designed to answer.

Number of Participants With Adverse Events (AEs) and Serious Adverse Events (SAEs)
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.
Measured: From Baseline (1 week prior to infusion) up to 5 years post-infusion (approximately 5 Years)
Central FVIII Activity Levels by Chromogenic Assay 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.
Measured: At Year 1 (Week 52)
Central FVIII Activity Levels by Chromogenic Assay 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.
Measured: At Year 2 (Week 104)
Central FVIII Activity Levels by Chromogenic Assay 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.
Measured: At Year 3 (Week 156)
Central FVIII Activity Levels by Chromogenic Assay 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.
Measured: At Year 4 (Week 208)
Central FVIII Activity Levels by Chromogenic Assay 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.
Measured: At Year 5 (Week 260)
Central FVIII Activity Levels by One-Stage Clotting Assay 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.
Measured: At Year 1 (Week 52)
Central FVIII Activity Levels by One-Stage Clotting Assay 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.
Measured: At Year 2 (Week 104)
Central FVIII Activity Levels by One-Stage Clotting Assay 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.
Measured: At Year 3 (Week 156)
Central FVIII Activity Levels by One-Stage Clotting Assay 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.
Measured: At Year 4 (Week 208)
Central FVIII Activity Levels by One-Stage Clotting Assay 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.
Measured: At Year 5 (Week 260)
Geometric Mean of Central FVIII Activity Levels for Cohort 4 by Chromogenic Assay at Yearly Interval 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.
Measured: Year 1 (Week 9 through Week 53)
Geometric Mean of Central FVIII Activity Levels for Cohort 4 by Chromogenic Assay at Yearly Interval 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.
Measured: Year 2 (Week 54 through Week 108)
Geometric Mean of Central FVIII Activity Levels for Cohort 4 by Chromogenic Assay at Yearly Interval 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.
Measured: Year 3 (Week 109 through Week 160)
Geometric Mean of Central FVIII Activity Levels for Cohort 4 by Chromogenic Assay at Yearly Interval 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.
Measured: Year 4 (Week 161 through Week 212)
Geometric Mean of Central FVIII Activity Levels for Cohort 4 by Chromogenic Assay at Yearly Interval 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.
Measured: Year 5 (Week 213 through Week 264)
Geometric Mean of Central FVIII Activity Levels for Cohort 4 by One-Stage Clotting Assay at Yearly Interval 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.
Measured: Year 1 (Week 9 through Week 53)
Geometric Mean of Central FVIII Activity Levels for Cohort 4 by One-Stage Clotting Assay at Yearly Interval 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.
Measured: Year 2 (Week 54 through Week 108)
Geometric Mean of Central FVIII Activity Levels for Cohort 4 by One-Stage Clotting Assay at Yearly Interval 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.
Measured: Year 3 (Week 109 through Week 160)
Geometric Mean of Central FVIII Activity Levels for Cohort 4 by One-Stage Clotting Assay at Yearly Interval 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.
Measured: Year 4 (Week 161 through Week 212)
Geometric Mean of Central FVIII Activity Levels for Cohort 4 by One-Stage Clotting Assay at Yearly Interval 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.
Measured: Year 5 (Week 213 through Week 264)

Secondary outcomes (11)

Total Annualized Bleeding Rate (ABR)
Total ABR included both treated and untreated bleeding episodes. In this outcome measure total ABR for pre-screening and post-infusion are reported. Pre-screening total ABR was based on the total number of reported bleeding episodes during 12 months prior to screening visit as reported on CRF's Hemophilia A History page. Screening was 2 months before baseline. Post- infusion total ABR = number of all bleeding episodes starting 3 weeks after investigational product/ PF-07055480 (IP) infusion up to date of day before start of prophylaxis (or date of data cut or conclusion date)/ observation period in years, where observation period in years = date of day before start of prophylaxis or date of data cut or conclusion date - 3 weeks after date of IP infusion + 1)/365.25. For a participant who did not start prophylaxis the data cut date or conclusion date is used.
Measured: 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
Total ABR include both treated and untreated bleeding episodes. In this outcome measure total ABR by severity for post-infusion period is reported. Severity was categorized as mild, moderate and severe. Post- infusion total ABR = number of all bleeding episodes starting 3 weeks after IP infusion up to date of day before start of prophylaxis (or date of data cut or conclusion date)/ observation period in years, where observation period in years = date of day before start of prophylaxis or date of data cut or conclusion date - 3 weeks after date of IP infusion + 1)/365.25. For a participant who did not start prophylaxis the data cut date or conclusion date is used.
Measured: 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)
AIR was calculated and reported for pre-infusion and post-infusion. AIR for pre-infusion was calculated as, a) Excluding prophylaxis: number of FVIII replacement infusions for reasons other than prophylaxis prior to IP infusion/ ([date of IP infusion - date of screening] + 30)] *365.25, or b) number of FVIII replacement infusions for any reason prior to IP infusion/ ([date of IP infusion - date of screening] + 30)] *365.25. Screening was 2 months before baseline and baseline was approximately 1-week prior to IP infusion. AIR for post- infusion was calculated as: number of FVIII replacement infusions started at 3 weeks after IP infusion up to date of data cut or conclusion date/ number of days in the observation period for the participant in years, where observation period in years = date of data cut or conclusion date - 3 weeks after date of IP infusion + 1)/365.25.
Measured: 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)
Change From Baseline in the EuroQol, 5 Dimensions, 5 Levels (EQ-5D-5L) Index Score at Weeks 12, 24 and 52; Months 24, 36, 48 and 60
EQ-5D-5L is a standardized measure of health status developed by the EuroQol Group. It measures 5 dimensions (mobility, self-care, usual activities, pain/discomfort, and anxiety/depression) of health on a 5-point scale. Each dimension had 5 levels: 1= no problems, 2= slight problems, 3= moderate problems, 4= severe problems, and 5= extreme problems. EQ-5D-5L had 2 components: Index score and visual analogue scale (VAS). Index score was obtained, according to the health state defined by the 5 dimensions scores, from the Crosswalk Index value calculator and table lookup document under the target country population. A health state is defined by the combination of one level from each of the 5 dimensions. For this study, weights under the US population were used to obtain the Index score. Index score ranged between 0-1, where higher score indicates a better health state, and lower score indicate worse health state. Baseline was defined as the latest non-missing value before IP infusion.
Measured: Baseline; Weeks 12, 24, and 52; Months 24, 36, 48, and 60
Change From Baseline in the EQ-5D-5L- VAS Score at Week 12, 24, 52 and Month 24, 36, 48, 60
EQ-5D-5L is a standardized measure of health status developed by the EuroQol Group. It measures 5 dimensions of health on a 5-point scale including mobility, self-care, usual activities, pain/discomfort, and anxiety/depression. Each dimension is assessed with 5 levels: 1= no problems, 2= slight problems, 3= moderate problems, 4= severe problems, and 5= extreme problems. EQ-5D-5L had 2 components: Index score and VAS. EQ-5D-5L VAS: Participants were asked to indicate their current health status on a scale of 0 (worst health) to 100 (best imaginable health), higher scores signified better health status. Baseline was defined as the latest non-missing value before IP infusion.
Measured: Baseline; Weeks 12, 24, and 52; Months 24, 36, 48, and 60
Number of Participants With Positive FVIII Inhibitor Levels During the Study
Positive FVIII inhibitor was assessed using central laboratory using Nijmegen method of the Bethesda assay in an individual with no prior history of FVIII inhibitor. Inhibitor assay results >0.6 Bethesda units (BU) were considered as positive. Positive results at any timepoint were considered, even if subsequent inhibitor assessment was negative.
Measured: Baseline (one week prior to IP infusion) up to 5 years post-infusion
Peak Value of AAV2/6 (Adeno-associated Vector 2/6) Deoxyribonucleic Acid (DNA) in Plasma, Saliva, Semen, Stool and Urine
Peak (maximum) AAV2/6 vector DNA concentration (vg/mL) in plasma, saliva, semen, stool and urine were analyzed with quantitative real-time polymerase chain reaction (PCR). Participants must achieve 3 consecutive negative results for analysis for each sample.
Measured: All samples: Baseline, Day 7, Week 2, 4, 8, 12, 16, 20, 24, 28, 32, 36, 40, 44, 48, 52 and every month after Week 52 until Month 60 until 3 consecutive negative samples are obtained on a sample-type basis; additional for plasma at 12 hours post-infusion
Time to Peak Value of AAV2/6 Vector DNA in Plasma, Saliva, Semen, Stool and Urine
Time to peak (maximum) AAV2/6 vector DNA concentration (vg/mL) in plasma, saliva, urine, stool and semen were analyzed with quantitative real-time PCR. Participants must achieve 3 consecutive negative results for analysis for each sample; where negative suggests values under the limit of detection.
Measured: All samples: Baseline, Day 7, Week 2, 4, 8, 12, 16, 20, 24, 28, 32, 36, 40, 44, 48, 52 and every month after Week 52 until Month 60 until 3 consecutive negative samples are obtained on a sample-type basis; additional for plasma at 12 hours post-infusion
Time to Undetectable (Negative) Value of AAV2/6 Vector DNA in Plasma, Saliva, Semen, Stool and Urine
Time to undetectable (negative) value of AAV2/6 vector DNA concentration (vg/mL) in plasma, saliva, urine, stool and semen were analyzed with quantitative real-time PCR. Time to undetectable is defined as the number of days from IP infusion until the first of 3 consecutive specimens under the limit of detection (negative).
Measured: All samples: Baseline, Day 7, Week 2, 4, 8, 12, 16, 20, 24, 28, 32, 36, 40, 44, 48, 52 and every month after Week 52 until Month 60 until 3 consecutive negative samples are obtained on a sample-type basis; additional for plasma at 12 hours post-infusion
Time to Last of 3 Consecutive Negative Values of AAV2/6 Vector DNA in Plasma, Saliva, Semen, Stool and Urine
Time to last of 3 consecutive negative value of AAV2/6 vector DNA concentration (vg/mL) in plasma, saliva, urine, stool and semen were analyzed with quantitative real-time PCR.
Measured: All samples: Baseline, Day 7, Week 2, 4, 8, 12, 16, 20, 24, 28, 32, 36, 40, 44, 48, 52 and every month after Week 52 until Month 60 until 3 consecutive negative samples are obtained on a sample-type basis; additional for plasma at 12 hours post-infusion
Time to Last Positive Value Prior to First of 3 Consecutive Negatives of AAV2/6 Vector DNA in Plasma, Saliva, Semen, Stool and Urine
Time to last positive value prior to first of 3 consecutive negatives of AAV2/6 vector DNA concentration (vg/mL) in plasma, saliva, urine, stool and semen were analyzed with quantitative real-time PCR, where positive suggests values above the limit of detection.
Measured: All samples: Baseline, Day 7, Week 2, 4, 8, 12, 16, 20, 24, 28, 32, 36, 40, 44, 48, 52 and every month after Week 52 until Month 60 until 3 consecutive negative samples are obtained on a sample-type basis; additional for plasma at 12 hours post-infusion

Timeline

From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.

21 Jun 201716 Jul 2024

First posted23 Feb 2017
Study start21 Jun 2017
Primary completion16 Jul 2024
Study completion16 Jul 2024

Resources

Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
Posted resultsParticipant flow, outcome measures and adverse events reported by the sponsor.
Publications (2)Papers the sponsor has linked to this study.
Other trials for Hemophilia AStudies of the same condition, open and under way.
More trials run by PfizerThe sponsor's other registered studies.
What the trial phases meanHow a treatment moves from first tests in people to approval.

More details

For doctors and researchers: how the study is designed, who runs it, and its registry IDs.

Study design

Study type: Interventional
Phase: Phase 2
Primary purpose: Treatment
Allocation: Not applicable
Intervention model: Sequential
Model description: Dose selection based on safety and kinetics of circulating FVIII levels observed in previously dosed participants.
Masking: None (open label)
Enrolment: 13 participants (actual)

IDs, dates and publications

ClinicalTrials.gov ID: NCT03061201
Sponsor's protocol ID: SB-525-1603
Other IDs: C3731001
Status last verified: Sep 2025
First submitted: 15 Feb 2017
Last updated: 30 Sep 2025
Results posted: Yes, on ClinicalTrials.gov
Data monitoring committee: Yes
FDA-regulated drug: Yes
FDA-regulated device: No
Individual data sharing: Yes: Pfizer will provide access to individual de-identified participant data and related study documents (e.g. protocol, Statistical Analysis Plan (SAP), Clinical Study Report (CSR)) upon request from qualified researchers, and subject to certain criteria, conditions, and exceptions. Further details on Pfizer's data sharing criteria and process for requesting access can be found at: https://www.pfizer.com/science/clinical\_trials/trial\_data\_and\_results/data\_requests.

Publications

Leavitt AD, Konkle BA, Stine KC, Visweshwar N, Harrington TJ, Giermasz A, Arkin S, Fang A, Plonski F, Yver A, Ganne F, Agathon D, Resa MLA, Tseng LJ, Di Russo G, Cockroft BM, Cao L, Rupon J. Giroctocogene fitelparvovec gene therapy for severe hemophilia A: 104-week analysis of the phase 1/2 Alta study. Blood. 2024 Feb 29;143(9):796-806. doi: 10.1182/blood.2022018971.
PubMed 37871576
Cao L, Ledeboer A, Pan Y, Lu Y, Meyer K. Clinical enrollment assay to detect preexisting neutralizing antibodies to AAV6 with demonstrated transgene expression in gene therapy trials. Gene Ther. 2023 Feb;30(1-2):150-159. doi: 10.1038/s41434-022-00353-2. Epub 2022 Jul 1.
PubMed 35778500

Want to know more?

The sponsor has not listed a contact. The official record may have more details.

Talk to your doctor first and take this page with you. Only the study team can confirm whether you can join.

Questions to ask the study team

What is the study trying to find out?
What would I need to do, and how often would I visit?
Could I receive a placebo instead of the treatment?
What are the possible risks and benefits for me?
Will it cost me anything? Are travel or time paid for?
Can I keep seeing my own doctor during the study?
What happens when the study ends?

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Study at a glance

From the registry record, last updated by the sponsor on 30 Sep 2025. Recruitment status is as the sponsor reported it: confirm with the study team.

Official title: A PHASE 1/2, OPEN-LABEL, ADAPTIVE, DOSE-RANGING STUDY TO ASSESS THE SAFETY AND TOLERABILITY OF SB-525 (PF-07055480) (RECOMBINANT AAV2/6 HUMAN FACTOR 8 GENE THERAPY) IN ADULT SUBJECTS WITH SEVERE HEMOPHILIA A
ClinicalTrials.gov ID: NCT03061201
Acronym / sponsor ID: SB-525-1603
Conditions: Hemophilia A
Phase: Phase 2
Study type: Interventional
Recruitment status: Completed
Enrolment: 13 participants (actual)
Lead sponsor: PfizerIndustry (pharma, biotech, devices)
Study start: 21 Jun 2017 (actual)
Primary completion: 16 Jul 2024 (actual)
Study completion: 16 Jul 2024 (actual)
First posted: 23 Feb 2017 (actual)
Results: Posted 30 Sep 2025

Clinical summary

The research question as the sponsor registered it. This describes what the study plans to test, not what it found.

The purpose of the study is to evaluate the safety, tolerability and time-course profile of FVIII activity after dosing with SB-525 (PF-07055480)

Detailed description

Study design

Primary purpose: Treatment
Allocation: Not applicable
Intervention model: Sequential
Masking: None (open label)
Number of arms: 1
Model description: Dose selection based on safety and kinetics of circulating FVIII levels observed in previously dosed participants.

Arm	Type	Receives
Sequential dose escalation	Experimental	Biological: SB-525 (PF-07055480)SB-525 (PF-07055480) is administered as a single infusion

Who may qualify

Ages: 18 years and older
Sex: Male only
Healthy volunteers: Not accepted
Age groups: Adult, Older adult

Key inclusion criteria (5 listed)

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 months
Agree to use double barrier contraceptive until at least 3 consecutive semen samples are negative for AAV 2/6 after SB-525 infusion

Key exclusion criteria (10 listed)

Presence of neutralizing antibodies
Current inhibitor, or history of FVIII inhibitor (except for transient low titer inhibitor detected in childhood)
History of hypersensitivity response to FVIII
History of Hepatitis B or HIV-1/2 infection
History of Hepatitis C, unless viral assays in two samples, collected at least 6 months apart, are negative

Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.

Interventions

Intervention	Type	Arms
SB-525 (PF-07055480)Single dose of investigational product SB-525 (PF-07055480)	Biological	Sequential dose escalation

Primary outcome

Number of Participants With Adverse Events (AEs) and Serious Adverse Events (SAEs)
Time frame: 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)
Time frame: 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)
Time frame: 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)
Time frame: 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)
Time frame: 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)
Time frame: 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)
Time frame: 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)
Time frame: 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)
Time frame: 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)
Time frame: 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)
Time frame: 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)
Time frame: 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)
Time frame: 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)
Time frame: 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)
Time frame: 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)
Time frame: 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)
Time frame: 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)
Time frame: 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)
Time frame: 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)
Time frame: 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)
Time frame: 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.

11 secondary outcomes

Total Annualized Bleeding Rate (ABR)
Time frame: 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
Time frame: 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)
Time frame: 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)
Change From Baseline in the EuroQol, 5 Dimensions, 5 Levels (EQ-5D-5L) Index Score at Weeks 12, 24 and 52; Months 24, 36, 48 and 60
Time frame: Baseline; Weeks 12, 24, and 52; Months 24, 36, 48, and 60
Change From Baseline in the EQ-5D-5L- VAS Score at Week 12, 24, 52 and Month 24, 36, 48, 60
Time frame: Baseline; Weeks 12, 24, and 52; Months 24, 36, 48, and 60
Number of Participants With Positive FVIII Inhibitor Levels During the Study
Time frame: Baseline (one week prior to IP infusion) up to 5 years post-infusion
Peak Value of AAV2/6 (Adeno-associated Vector 2/6) Deoxyribonucleic Acid (DNA) in Plasma, Saliva, Semen, Stool and Urine
Time frame: All samples: Baseline, Day 7, Week 2, 4, 8, 12, 16, 20, 24, 28, 32, 36, 40, 44, 48, 52 and every month after Week 52 until Month 60 until 3 consecutive negative samples are obtained on a sample-type basis; additional for plasma at 12 hours post-infusion
Time to Peak Value of AAV2/6 Vector DNA in Plasma, Saliva, Semen, Stool and Urine
Time frame: All samples: Baseline, Day 7, Week 2, 4, 8, 12, 16, 20, 24, 28, 32, 36, 40, 44, 48, 52 and every month after Week 52 until Month 60 until 3 consecutive negative samples are obtained on a sample-type basis; additional for plasma at 12 hours post-infusion
Time to Undetectable (Negative) Value of AAV2/6 Vector DNA in Plasma, Saliva, Semen, Stool and Urine
Time frame: All samples: Baseline, Day 7, Week 2, 4, 8, 12, 16, 20, 24, 28, 32, 36, 40, 44, 48, 52 and every month after Week 52 until Month 60 until 3 consecutive negative samples are obtained on a sample-type basis; additional for plasma at 12 hours post-infusion
Time to Last of 3 Consecutive Negative Values of AAV2/6 Vector DNA in Plasma, Saliva, Semen, Stool and Urine
Time frame: All samples: Baseline, Day 7, Week 2, 4, 8, 12, 16, 20, 24, 28, 32, 36, 40, 44, 48, 52 and every month after Week 52 until Month 60 until 3 consecutive negative samples are obtained on a sample-type basis; additional for plasma at 12 hours post-infusion
Time to Last Positive Value Prior to First of 3 Consecutive Negatives of AAV2/6 Vector DNA in Plasma, Saliva, Semen, Stool and Urine
Time frame: All samples: Baseline, Day 7, Week 2, 4, 8, 12, 16, 20, 24, 28, 32, 36, 40, 44, 48, 52 and every month after Week 52 until Month 60 until 3 consecutive negative samples are obtained on a sample-type basis; additional for plasma at 12 hours post-infusion

Results and safety

Results posted to the registry on 30 Sep 2025, as reported by the sponsor. Figures are copied from the record, not re-analysed. Full results on ClinicalTrials.gov.

Participant flow

Group	Started	Completed
Cohort 1: PF-07055480 9*10^11 vg/kg	2	1
Cohort 2: PF-07055480 2*10^12 vg/kg	2	1
Cohort 3: PF-07055480 1*10^13 vg/kg	2	2
Cohort 4: PF-07055480 3*10^13 vg/kg	5	4

Primary outcome: Number of Participants With Adverse Events (AEs) and Serious Adverse Events (SAEs)

Time frame: From Baseline (1 week prior to infusion) up to 5 years post-infusion (approximately 5 Years). Count of participants. Unit: Participants

Measure	Cohort 1: PF-07055480 9*10^11 vg/kg n = 2	Cohort 2: PF-07055480 2*10^12 vg/kg n = 2	Cohort 3: PF-07055480 1*10^13 vg/kg n = 2	Cohort 4: PF-07055480 3*10^13 vg/kg n = 5
Participants With AEs	2	2	2	5
Participants With SAEs	0	2	0	1

Population analysed: Safety population included all participants enrolled in this study who received any portion of study intervention.

Primary outcome: Central FVIII Activity Levels by Chromogenic Assay at Year 1 (Week 52)

Time frame: At Year 1 (Week 52). Mean (Standard Deviation). Unit: Percentage of Normal

Measure	Cohort 1: PF-07055480 9*10^11 vg/kg n = 0	Cohort 2: PF-07055480 2*10^12 vg/kg n = 2	Cohort 3: PF-07055480 1*10^13 vg/kg n = 1	Cohort 4: PF-07055480 3*10^13 vg/kg n = 4
Value	–	0.90 (0.000)	11.90	42.60 (53.473)

Population analysed: Safety population included all participants enrolled in this study who received any portion of study intervention. Here, "Overall Number of Participants Analyzed" signifies participants evaluable for this outcome measure. For Cohort 1, both participants resumed prophylaxis regimen prior to Week 52, and were excluded from analysis as pre-specified in the Statistical Analysis Plan (SAP).

Primary outcome: Central FVIII Activity Levels by Chromogenic Assay at Year 2 (Week 104)

Time frame: At Year 2 (Week 104). Mean (Standard Deviation). Unit: Percentage of Normal

Measure	Cohort 1: PF-07055480 9*10^11 vg/kg n = 0	Cohort 2: PF-07055480 2*10^12 vg/kg n = 1	Cohort 3: PF-07055480 1*10^13 vg/kg n = 1	Cohort 4: PF-07055480 3*10^13 vg/kg n = 5
Value	–	19.30	8.25	25.44 (27.532)

Primary outcome: Central FVIII Activity Levels by Chromogenic Assay at Year 3 (Week 156)

Time frame: At Year 3 (Week 156). Mean (Standard Deviation). Unit: Percentage of Normal

Measure	Cohort 1: PF-07055480 9*10^11 vg/kg n = 0	Cohort 2: PF-07055480 2*10^12 vg/kg n = 1	Cohort 3: PF-07055480 1*10^13 vg/kg n = 1	Cohort 4: PF-07055480 3*10^13 vg/kg n = 5
Value	–	0.90	4.40	25.46 (36.998)

11 secondary outcomes are reported in the full results.

Adverse events

Time frame: From Baseline (1 week prior to infusion) up to 5 years post-infusion (approximately 5 Years). Other adverse events reported at 5% frequency or more

Group	Serious adverse events	Other adverse events	Deaths
Cohort 1: PF-07055480 9*10^11 vg/kg	0 of 2 (0%)	2 of 2 (100%)	0 of 2
Cohort 2: PF-07055480 2*10^12 vg/kg	2 of 2 (100%)	2 of 2 (100%)	0 of 2
Cohort 3: PF-07055480 1*10^13 vg/kg	0 of 2 (0%)	2 of 2 (100%)	0 of 2
Cohort 4: PF-07055480 3*10^13 vg/kg	1 of 5 (20%)	5 of 5 (100%)	0 of 5

Limitations and caveats (from the sponsor): Any untoward clinically significant changes from pre vector dosing identified on physical examinations, clinical laboratory assessments, immune parameters, liver imaging, vital signs, Electrocardiogram during the during study were captured as AEs.

Loading the posted results from ClinicalTrials.gov…

Research links

Official record on ClinicalTrials.govLast updated by the sponsor 30 Sep 2025.
Posted resultsParticipant flow, baseline, all outcome measures and adverse events.
Derived from this study: PubMed 37871576Leavitt AD, Konkle BA, Stine KC, Visweshwar N, Harrington TJ, Giermasz A, Arkin S, Fang A, Plonski F, Yver A, Ganne F, Agathon D, Resa MLA, Tseng LJ, Di Russo G, Cockroft BM, Cao L, Rupon J. Giroctocogene fitelparvovec gene therapy for severe hemophilia A: 104-week analysis of the phase 1/2 Alta study. Blood. 2024 Feb 29;143(9):796-806. doi: 10.1182/blood.2022018971.
Derived from this study: PubMed 35778500Cao L, Ledeboer A, Pan Y, Lu Y, Meyer K. Clinical enrollment assay to detect preexisting neutralizing antibodies to AAV6 with demonstrated transgene expression in gene therapy trials. Gene Ther. 2023 Feb;30(1-2):150-159. doi: 10.1038/s41434-022-00353-2. Epub 2022 Jul 1.
To obtain contact information for a study center near you, click here.Link provided by the sponsor.
Individual participant dataSharing planned: Yes. Pfizer will provide access to individual de-identified participant data and related study documents (e.g. protocol, Statistical Analysis Plan (SAP), Clinical Study Report (CSR)) upon request from qualified researchers, and subject to certain criteria, conditions, and exceptions. Further details on Pfizer's data sharing criteria and process for requesting access can be found at: https://www.pfizer.com/science/clinical_trials/trial_data_and_results/data_requests.

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Referral and contact

AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.

Pfizer CT.gov Call Center study director

Pfizer

22 sites in 1 country: see every site and its status.

Questions about this trial

What is this clinical trial studying?

A Phase 2 study testing SB-525 (PF-07055480) in people with Hemophilia A, run by Pfizer at 22 sites in United States.

The full registered description is in the About this study section and the official record.

Who may be eligible to take part?

The sponsor lists 5 inclusion and 10 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.

Is this clinical trial currently recruiting?

The record says: finished, as of the sponsor's last update on 30 Sep 2025. Status can change between updates, so confirm with the study contact before making plans.

Where is the study taking place?

The record lists 22 sites in United States. Whether a site is taking part right now should be confirmed with that site. See every site.

What are the possible benefits and risks?

They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.

What does this phase mean?

Phase 2 studies give the treatment to a larger group to see whether it has the intended effect and to keep checking safety.

Not every study follows the same path, and some studies (observational studies, device studies) have no phase.

Are results available for this study?

Yes. Results are posted in the registry (first posted 30 Sep 2025). A summary is in the For doctors view, and the full results are on ClinicalTrials.gov.

How can a doctor refer a patient or contact the research team?

The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.

What does the primary outcome measure?

Number of Participants With Adverse Events (AEs) and Serious Adverse Events (SAEs) (time frame: From Baseline (1 week prior to infusion) up to 5 years post-infusion (approximately 5 Years)). The study lists 21 primary outcomes in all. It is what the study was designed to measure, not a finding.

Where can I read the original study information?

On the ClinicalTrials.gov record for NCT03061201, which also lists 2 linked publications.

Does a listing mean the treatment is approved or proven to work?

No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.

How often is this information updated?

AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 30 Sep 2025.