Long-term Safety and Efficacy Study and Dose-Escalation Substudy of PF 06838435 in Individuals With Hemophilia B

May 11, 2026 updated by: Pfizer

A FACTOR IX (FIX) GENE TRANSFER, MULTI CENTER EVALUATION OF THE LONG TERM SAFETY AND EFFICACY STUDY OF PF 06838435 AND A DOSE ESCALATION SUBSTUDY IN INDIVIDUALS WITH HEMOPHILIA B

Long-term safety and efficacy follow-up for participants with Hemophilia B who were previously treated in the C0371005 (formerly SPK-9001-101) study, and a dose-escalation sub-study evaluating safety, tolerability, and kinetics of a higher dose with long-term safety and efficacy follow-up. Participants in the substudy do not need to have participated in C0371005.

Study Overview

Status

Status

Indicates the current recruitment status or the expanded access status.
Active, not recruiting

Conditions

Conditions

The disease, disorder, syndrome, illness, or injury that is being studied. On ClinicalTrials.gov, conditions may also include other health-related issues, such as lifespan, quality of life, and health risks.

Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.

Detailed Description

Evaluation of the long-term level of persistence and potential late or delayed adverse events associated with PF-06838435 (formerly SPK-9001), assessment of the durability of the transgene expression, and determination of the effects of PF-06838435 on clinical outcomes in individuals who have previously received a single administration of PF-06838435 in the C0371005 study. Amendment 2 of this study incorporates a dose-escalation substudy to evaluate the safety, tolerability, and kinetics of a single IV infusion of PF-06838435 at a higher dose than that used in the C0371005 study. The dose-escalation participants will also be followed for long-term safety and efficacy.

Study Type

Study Type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies (including patient registries), and expanded access.
Interventional

Enrollment (Actual)

Enrollment

The number of participants in a clinical study. The "anticipated" enrollment is the target number of participants that the researchers need for the study.
21

Phase

Phase

The stage of a clinical trial studying a drug or biological product, based on definitions developed by the U.S. Food and Drug Administration (FDA). The phase is based on the study's objective, the number of participants, and other characteristics. There are five phases: Early Phase 1 (formerly listed as Phase 0), Phase 1, Phase 2, Phase 3, and Phase 4. Not Applicable is used to describe trials without FDA-defined phases, including trials of devices or behavioral interventions.
  • Phase 2

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • Australia
    • New South Wales
      • Camperdown, New South Wales, Australia, 2050
        • Royal Prince Alfred Hospital
  • Canada
    • Ontario
      • Hamilton, Ontario, Canada, L8N 3Z5
        • McMaster University Medical Centre - Hamilton Health Sciences
      • Hamilton, Ontario, Canada, L8S 3L8
        • McMaster University
    • Quebec
      • Montreal, Quebec, Canada, H4A 3J1
        • McGill University Health Center - Research Institute
      • Montreal, Quebec, Canada, H3H 2R9
        • The Research Institute of the McGill University Health Centre
  • Turkey (Türkiye)
      • Istanbul, Turkey (Türkiye), 34093
        • Istanbul Universitesi Onkoloji Enstitusu Çocuk Hematoloji Onkoloji Bilim Dali
      • Istanbul, Turkey (Türkiye), 34452
        • Istanbul University Clinical Trials Excellence Center
      • Izmir, Turkey (Türkiye), 35100
        • Ege Universitesi Tip Fakultesi Cocuk Sagligi ve Hastaliklari Anabilim Dali
  • United States
    • California
      • Sacramento, California, United States, 95817
        • UC Davis Medical Center
      • Sacramento, California, United States, 95817
        • UC Davis Comprehensive Cancer Center
      • Sacramento, California, United States, 95817
        • UC Davis Ellison Ambulatory Care Clinic
      • Sacramento, California, United States, 95817
        • UC Davis Medical Center department of Radiology
      • Sacramento, California, United States, 95817
        • UC Davis Midtown Cancer Center
      • Sacramento, California, United States, 95817
        • UC DavisHealth Main Hospital
    • Louisiana
      • Metairie, Louisiana, United States, 70001
        • LA Center for Bleeding and Clotting Disorders - Metairie
      • Metairie, Louisiana, United States, 70001
        • Tulane Lakeside Hospital
      • New Orleans, Louisiana, United States, 70112
        • Tulane University School of Medicine
      • New Orleans, Louisiana, United States, 70112
        • University Medical Center New Orleans
      • New Orleans, Louisiana, United States, 70112
        • Tulane University Clinical Translational Unit
      • New Orleans, Louisiana, United States, 70112
        • LA Center for Bleeding and Clotting Disorders
      • New Orleans, Louisiana, United States, 70112
        • Tulane University Hospitals and Clinic
      • Slidell, Louisiana, United States, 70461
        • Louisiana Center for Advanced Medicine
    • Mississippi
      • Madison, Mississippi, United States, 39110
        • Mississippi Center for Advanced Medicine
    • New York
      • New York, New York, United States, 10065
        • Weill Cornell Medicine - New York Presbyterian Hospital
    • Pennsylvania
      • Philadelphia, Pennsylvania, United States, 19104
        • The Children's Hospital of Philadelphia

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Eligibility Criteria

The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). Types of eligibility criteria include whether a study accepts healthy volunteers, has age or age group requirements, or is limited by sex.

Ages Eligible for Study

18 years to 65 years (Adult, Older Adult)

Accepts Healthy Volunteers

No

Description

This study is currently only enrolling into the dose-escalation substudy with subsequent long-term follow-up. The Eligibility Criteria for entry into the dose-escalation substudy is presented below:

Inclusion Criteria:

  1. Able to provide informed consent and comply with requirements of the study
  2. Males age 18 to 65 years with confirmed diagnosis of hemophilia B (≤2 IU/dL or ≤2% endogenous factor IX)
  3. Received ≥50 exposure days to factor IX products
  4. No measurable factor IX inhibitor as assessed by the central laboratory and have no prior history of inhibitors to factor IX protein
  5. Agree to refrain from donating sperm and either abstain from intercourse or use reliable barrier contraception until 3 consecutive semen samples are negative for vector sequences

Exclusion Criteria:

  1. Evidence of active hepatitis B or C
  2. Currently on antiviral therapy for hepatitis B or C
  3. Have significant underlying liver disease
  4. Serological evidence* of HIV-1 or HIV-2 with CD4 counts ≤200/mm3 (* participants who are HIV+ and stable with CD4 count >200/mm3 and undetectable viral load are eligible to enroll)
  5. Neutralizing antibody titers to the capsid portion of PF-06838435 above the established threshold
  6. Sensitivity to heparin or heparin induced thrombocytopenia; sensitivity to any of the study interventions, or components thereof, or drug or other allergy
  7. Previously dosed in a gene therapy research trial at any time or in an interventional clinical study within 3 months of screening visit
  8. Any concurrent clinically significant major disease or condition
  9. Unable or unwilling to comply with the study procedures

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: N/A
  • Interventional Model: Sequential Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm

Participant Group / Arm

A group or subgroup of participants in a clinical trial that receives a specific intervention/treatment, or no intervention, according to the trial's protocol.
Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.
Experimental: PF-06838435 Dose-Escalation
Single intravaneous infusion of PF-06838435. After 2 participants receive initial dose, data will be evaluated and a decision will be made to escalate or reduce the dose being evaluated, increase the number of participants receiving the dose, or stop dosing. Multiple iterations may be undertaken.
Biological: PF-06838435 (formerly SPK-9001)
Gene Therapy: A novel, bioengineered adeno-associated viral vector carrying human factor IX variant

What is the study measuring?

Primary Outcome Measures

Primary Outcome Measures

In a clinical study's protocol, the planned outcome measure that is the most important for evaluating the effect of an intervention/treatment. Most clinical studies have one primary outcome measure, but some have more than one.
Outcome Measure
Time Frame
Incidence of PF-06838435 related adverse events
Time Frame: Baseline up to Year 6
Baseline up to Year 6

Secondary Outcome Measures

Secondary Outcome Measures

In a clinical study's protocol, a planned outcome measure that is not as important as the primary outcome measure for evaluating the effect of an intervention but is still of interest. Most clinical studies have more than one secondary outcome measure.
Outcome Measure
Measure Description
Time Frame
Incidence of clinically significant changes from baseline
Time Frame: Baseline up to 52 weeks
Clinically significant changes in physical examination, vital signs, laboratory values. (to be reported as AEs, regardless of causality)
Baseline up to 52 weeks
Incidence of protocol-defined medically important events
Time Frame: Baseline up to 52 weeks
Clinical thrombotic events, FIX inhibitor development as assessed by Nijmegen Bethesda assay, Hypersensitivity reaction (eg, bronchospasm and anaphylaxis), Hepatic malignancy, Study intervention-related elevated hepatic transaminases that fail to improve or resolve, Malignancy assessed as having reasonable possibility of being related to study intervention (to be reported as SAEs).
Baseline up to 52 weeks
Immune response against AAV capsid protein and hFIX transgene
Time Frame: Baseline up to 52 weeks
Positive immune response based on peripheral blood mononuclear cell (PBMC) results by interferon gamma enzyme-linked immunospot assay (ELISPOT).
Baseline up to 52 weeks
Coagulation Clotting Assay for FIX activity levels
Time Frame: Baseline up to Year 6
Coagulation Clotting assays to assess FIX activity levels (percent of normal)
Baseline up to Year 6
Mean and standard deviation of vector-derived FIX Activity levels
Time Frame: Baseline up to 52 weeks
Mean and standard deviation of peak and steady-state FIX Activity
Baseline up to 52 weeks
Mean and standard deviation of FIX Antigen levels
Time Frame: Baseline up to 52 weeks
Mean and standard deviation of FIX Antigen levels
Baseline up to 52 weeks
Annualized bleeding rate (ABR)
Time Frame: Baseline up to Year 6
ABR (not including those for surgery)
Baseline up to Year 6
Annualized (factor FIX) infusion rate
Time Frame: Baseline up to Year 6
AIR (not including those for surgery)
Baseline up to Year 6
Total factor consumption (IU)
Time Frame: Baseline up to Year 6
total quantity of factor infused annually (not including those for surgery) as recorded on the infusion log
Baseline up to Year 6
Total number of bleeding events
Time Frame: Baseline up to Year 6
spontaneous and traumatic
Baseline up to Year 6
Haem-A-QoL
Time Frame: Baseline up to Year 6
Quality-of-life (QoL) assessment
Baseline up to Year 6
EQ-5D-5L
Time Frame: Baseline up to Year 6
Quality-of-life (QoL) assessment
Baseline up to Year 6
Brief Pain Inventory
Time Frame: Year 2 up to Year 6
Quality-of-life (QoL) assessment
Year 2 up to Year 6
McGill Pain Questionnaire
Time Frame: Baseline up to 52 weeks
Quality-of-life (QoL) assessment
Baseline up to 52 weeks

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Sponsor

The organization or person who initiates the study and who has authority and control over the study.
Pfizer

Investigators

Investigators

A researcher involved in a clinical study. Related terms include site principal investigator, site sub-investigator, study chair, study director, and study principal investigator.
  • Study Director: Pfizer CT.gov Call Center, Pfizer

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Helpful Links

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

Study Start

The actual date on which the first participant was enrolled in a clinical study. The "anticipated" study start date is the date that the researchers think will be the study start date.
June 22, 2017

Primary Completion (Estimated)

Primary Completion

The date on which the last participant in a clinical study was examined or received an intervention to collect final data for the primary outcome measure. Whether the clinical study ended according to the protocol or was terminated does not affect this date. For clinical studies with more than one primary outcome measure with different completion dates, this term refers to the date on which data collection is completed for all the primary outcome measures. The "anticipated" primary completion date is the date that the researchers think will be the primary completion date for the study.
May 29, 2029

Study Completion (Estimated)

Study Completion

The date on which the last participant in a clinical study was examined or received an intervention/treatment to collect final data for the primary outcome measures, secondary outcome measures, and adverse events (that is, the last participant's last visit). The "anticipated" study completion date is the date that the researchers think will be the study completion date.
October 25, 2029

Study Registration Dates

First Submitted

First Submitted

The date on which the study sponsor or investigator first submitted a study record to ClinicalTrials.gov. There is typically a delay of a few days between the first submitted date and the record's availability on ClinicalTrials.gov (the first posted date).
September 29, 2017

First Submitted That Met QC Criteria

First Submitted That Met QC Criteria

The date on which the study sponsor or investigator first submits a study record that is consistent with National Library of Medicine (NLM) quality control (QC) review criteria. The sponsor or investigator may need to revise and submit a study record one or more times before NLM's QC review criteria are met. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
October 6, 2017

First Posted (Actual)

First Posted

The date on which the study record was first available on ClinicalTrials.gov after National Library of Medicine (NLM) quality control (QC) review has concluded. There is typically a delay of a few days between the date the study sponsor or investigator submitted the study record and the first posted date.
October 12, 2017

Study Record Updates

Last Update Posted (Actual)

Last Update Posted

The most recent date on which changes to a study record were made available on ClinicalTrials.gov. There may be a delay between when the changes were submitted to ClinicalTrials.gov by the study's sponsor or investigator (the last update submitted date) and the last update posted date.
May 12, 2026

Last Update Submitted That Met QC Criteria

Last Update Submitted That Met QC Criteria

The most recent date on which the study sponsor or investigator submitted changes to a study record that are consistent with National Library of Medicine (NLM) quality control (QC) review criteria. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
May 11, 2026

Last Verified

Last Verified

The most recent date on which the study sponsor or investigator confirmed the information about a clinical study on ClinicalTrials.gov as accurate and current. If a study with a recruitment status of recruiting; not yet recruiting; or active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as unknown.
May 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

Other Study ID Numbers

Identifiers or ID numbers other than the NCT number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other trial registries and National Institutes of Health grant numbers.
  • C0371003
  • SPK-9001-LTFU-101 (Other Identifier: Alias Study Number)

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

YES

IPD Plan Description

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.

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

Yes

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

Clinical Trials on Hemophilia B

Clinical Trials on PF-06838435 (formerly SPK-9001)

Search Similar Trials

Sponsors and Collaborators

Medical Conditions

Drug Interventions

Conditions

Rare Diseases

Drug Interventions

Dietary Supplements

Sponsor/Collaborators

Locations

Cookie Settings

We use cookies to ensure that we give you the best experience on our website. For more details carefully read our Privacy and Cookies Policy. ...>>>You can change your preferences or withdraw your consent at any time by deleting the cookies from your website or computer as described in the policy. Please accept it and choose your preferences by ticking the corresponding boxes in the "Manage Settings" section below. Please carefully read our Terms of Service before you proceed with using any part of this website.
«Manage Settings