Hemophilia BPhase 2NCT03307980
Long-term Safety and Efficacy Study and Dose-Escalation Substudy of PF 06838435 in Individuals With Hemophilia B
A Phase 2 study testing PF-06838435 (formerly SPK-9001) in people with Hemophilia B, run by Pfizer at 25 sites in 4 countries.
Trial summary
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. Read more about this study
- Who is it for?
- Ages 18 to 65 years, men only
- Conditions the study is for
- Hemophilia B
- What is being tested?
- PF-06838435 (formerly SPK-9001)
- Type of treatment
- Injection or infusion
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 21 participants
- Where
- 25 sitesin 4 countries
- Study dates
- 22 Jun 2017to 23 Jul 2026
- Phase
- Phase 2
- Are there results?
- None posted in the registry
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 to 65 years
- Men only
- No healthy volunteers
- Adult, Older adult
Who may be able to join
- Able to provide informed consent and comply with requirements of the study
- Males age 18 to 65 years with confirmed diagnosis of hemophilia B (≤2 IU/dL or ≤2% endogenous factor IX)
- Received ≥50 exposure days to factor IX products
- No measurable factor IX inhibitor as assessed by the central laboratory and have no prior history of inhibitors to factor IX protein
- 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
Who cannot join
- Evidence of active hepatitis B or C
- Currently on antiviral therapy for hepatitis B or C
- Have significant underlying liver disease
- 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)
- Neutralizing antibody titers to the capsid portion of PF-06838435 above the established threshold
- Sensitivity to heparin or heparin induced thrombocytopenia; sensitivity to any of the study interventions, or components thereof, or drug or other allergy
Show all 9Show fewer
- Previously dosed in a gene therapy research trial at any time or in an interventional clinical study within 3 months of screening visit
- Any concurrent clinically significant major disease or condition
- Unable or unwilling to comply with the study procedures
Trial locations and contacts
25 sites in 4 countries.
25 sites in 4 countries
United States17 sites
Mississippi Center for Advanced Medicine
Madison, Mississippi, 39110
LA Center for Bleeding and Clotting Disorders - Metairie
Metairie, Louisiana, 70001
Tulane Lakeside Hospital
Metairie, Louisiana, 70001
LA Center for Bleeding and Clotting Disorders
New Orleans, Louisiana, 70112
Tulane University Clinical Translational Unit
New Orleans, Louisiana, 70112
Tulane University Hospitals and Clinic
New Orleans, Louisiana, 70112
Tulane University School of Medicine
New Orleans, Louisiana, 70112
University Medical Center New Orleans
New Orleans, Louisiana, 70112
Weill Cornell Medicine - New York Presbyterian Hospital
New York, New York, 10065
The Children's Hospital of Philadelphia
Philadelphia, Pennsylvania, 19104
UC Davis Comprehensive Cancer Center
Sacramento, California, 95817
UC Davis Ellison Ambulatory Care Clinic
Sacramento, California, 95817
UC Davis Medical Center department of Radiology
Sacramento, California, 95817
UC Davis Medical Center
Sacramento, California, 95817
UC Davis Midtown Cancer Center
Sacramento, California, 95817
UC DavisHealth Main Hospital
Sacramento, California, 95817
Louisiana Center for Advanced Medicine
Slidell, Louisiana, 70461
Canada4 sites
McMaster University Medical Centre - Hamilton Health Sciences
Hamilton, Ontario, L8N 3Z5
McMaster University
Hamilton, Ontario, L8S 3L8
The Research Institute of the McGill University Health Centre
Montreal, Quebec, H3H 2R9
McGill University Health Center - Research Institute
Montreal, Quebec, H4A 3J1
Turkey (Türkiye)3 sites
Istanbul Universitesi Onkoloji Enstitusu Çocuk Hematoloji Onkoloji Bilim Dali
Istanbul, 34093
Istanbul University Clinical Trials Excellence Center
Istanbul, 34452
Ege Universitesi Tip Fakultesi Cocuk Sagligi ve Hastaliklari Anabilim Dali
Izmir, 35100
Australia1 site
Royal Prince Alfred Hospital
Camperdown, New South Wales, 2050
About this study
Official title: 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.
Read the 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.
- Conditions
- Hemophilia B
- Being tested
- PF-06838435 (formerly SPK-9001)
- Keywords
- gene therapy, BeneGene LTE, hemophilia, SPK-9001, Factor IX, FIX
- Medical subject headings
- Hemophilia B, Hemophilia A
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
PF-06838435 (formerly SPK-9001)Biological
Gene Therapy: A novel, bioengineered adeno-associated viral vector carrying human factor IX variant
| Study group | Role | What they receive |
|---|---|---|
| PF-06838435 Dose-Escalation | Experimental | 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. Receives: Biological: PF-06838435 (formerly SPK-9001) |
What is being measured
The primary outcome is the main question the study is designed to answer.
Incidence of PF-06838435 related adverse events
Measured: Baseline up to Year 6
Secondary outcomes (14)
Incidence of clinically significant changes from baseline
Clinically significant changes in physical examination, vital signs, laboratory values. (to be reported as AEs, regardless of causality)
Measured: Baseline up to 52 weeks
Incidence of protocol-defined medically important events
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).
Measured: Baseline up to 52 weeks
Immune response against AAV capsid protein and hFIX transgene
Positive immune response based on peripheral blood mononuclear cell (PBMC) results by interferon gamma enzyme-linked immunospot assay (ELISPOT).
Measured: Baseline up to 52 weeks
Coagulation Clotting Assay for FIX activity levels
Coagulation Clotting assays to assess FIX activity levels (percent of normal)
Measured: Baseline up to Year 6
Mean and standard deviation of vector-derived FIX Activity levels
Mean and standard deviation of peak and steady-state FIX Activity
Measured: Baseline up to 52 weeks
Mean and standard deviation of FIX Antigen levels
Mean and standard deviation of FIX Antigen levels
Measured: Baseline up to 52 weeks
Annualized bleeding rate (ABR)
ABR (not including those for surgery)
Measured: Baseline up to Year 6
Annualized (factor FIX) infusion rate
AIR (not including those for surgery)
Measured: Baseline up to Year 6
Total factor consumption (IU)
total quantity of factor infused annually (not including those for surgery) as recorded on the infusion log
Measured: Baseline up to Year 6
Total number of bleeding events
spontaneous and traumatic
Measured: Baseline up to Year 6
Haem-A-QoL
Quality-of-life (QoL) assessment
Measured: Baseline up to Year 6
EQ-5D-5L
Quality-of-life (QoL) assessment
Measured: Baseline up to Year 6
Brief Pain Inventory
Quality-of-life (QoL) assessment
Measured: Year 2 up to Year 6
McGill Pain Questionnaire
Quality-of-life (QoL) assessment
Measured: Baseline up to 52 weeks
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted12 Oct 2017
- Study start22 Jun 2017
- Primary completion23 Jul 2026
- Study completion23 Jul 2026
Why it stopped: The study was terminated early due to Sponsor and participants may transition into a long-term follow-up study. The decision to terminate the trial was not based on any safety and/or efficacy concerns.
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Publications (3)Papers the sponsor has linked to this study.
- Other trials for Hemophilia BStudies 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
- This study was originally designed as a long-term follow up study for individuals dosed in Study C0371005 to evaluate the overall long-term safety, durability of transgene expression, and effect on clinical outcomes of PF-06838435 mediated gene transfer. For these individuals this study will last for 5 years providing a minimum of 6 years of follow up post vector administration. Amendment 2 of this study introduces a dose-escalation substudy to evaluate the safety, tolerability, and kinetics of a single IV infusion of PF-06838435 at a higher dose(s) than that used in the C0371005 study. For these participants this study will last for a total of 6 years post vector administration.
- Masking
- None (open label)
- Enrolment
- 21 participants (actual)
Sponsor and investigators
- Lead sponsor
- Pfizer
- Sponsor type
- Industry (pharma, biotech, devices)
- Responsible party
- Sponsor
- Investigators
- Pfizer CT.gov Call Center, Study director, Pfizer
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT03307980
- Sponsor's protocol ID
- C0371003
- Other IDs
- SPK-9001-LTFU-101
- Status last verified
- Sep 2026
- First submitted
- 29 Sep 2017
- Last updated
- 5 Oct 2026
- Results posted
- No
- 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
Samelson-Jones BJ, Rasko JEJ, Ducore JM, McGuinn CE, George LA, von Mackensen S, Borgonuovo G, Agathon D, Smith L, Wilcox LJ, Biondo F, Plonski F. Safety, efficacy, and patient-reported outcomes 6 years after fidanacogene elaparvovec in adults with hemophilia B. Blood Adv. 2026 May 26;10(10):3517-3526. doi: 10.1182/bloodadvances.2025019174.
PubMed 41734390Wojciechowski J, Gaitonde P, Hughes JH, Ravva P. Population Modeling of Factor IX Activity Following Administration of Fidanacogene Elaparvovec Gene Therapy in Participants with Hemophilia B. Clin Pharmacokinet. 2025 Oct;64(10):1531-1548. doi: 10.1007/s40262-025-01535-y. Epub 2025 Aug 1.
PubMed 40750723Rasko JEJ, Samelson-Jones BJ, George LA, Giermasz A, Ducore JM, Teitel JM, McGuinn CE, High KA, de Jong YP, Chhabra A, O'Brien A, Smith LM, Winburn I, Rupon J. Fidanacogene Elaparvovec for Hemophilia B - A Multiyear Follow-up Study. N Engl J Med. 2025 Apr 17;392(15):1508-1517. doi: 10.1056/NEJMoa2307159.
PubMed 40239068
Study at a glance
From the registry record, last updated by the sponsor on 5 Oct 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- 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
- ClinicalTrials.gov ID
- NCT03307980
- Acronym / sponsor ID
- C0371003
- Conditions
- Hemophilia B
- Keywords
- gene therapy, BeneGene LTE, hemophilia, SPK-9001, Factor IX, FIX
- Phase
- Phase 2
- Study type
- Interventional
- Recruitment status
- TerminatedReason stopped: The study was terminated early due to Sponsor and participants may transition into a long-term follow-up study. The decision to terminate the trial was not based on any safety and/or efficacy concerns.
- Enrolment
- 21 participants (actual)
- Lead sponsor
- PfizerIndustry (pharma, biotech, devices)
- Study start
- 22 Jun 2017 (actual)
- Primary completion
- 23 Jul 2026 (actual)
- Study completion
- 23 Jul 2026 (actual)
- First posted
- 12 Oct 2017 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
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.
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 design
- Primary purpose
- Treatment
- Allocation
- Not applicable
- Intervention model
- Sequential
- Masking
- None (open label)
- Number of arms
- 1
- Model description
- This study was originally designed as a long-term follow up study for individuals dosed in Study C0371005 to evaluate the overall long-term safety, durability of transgene expression, and effect on clinical outcomes of PF-06838435 mediated gene transfer. For these individuals this study will last for 5 years providing a minimum of 6 years of follow up post vector administration. Amendment 2 of this study introduces a dose-escalation substudy to evaluate the safety, tolerability, and kinetics of a single IV infusion of PF-06838435 at a higher dose(s) than that used in the C0371005 study. For these participants this study will last for a total of 6 years post vector administration.
| Arm | Type | Receives |
|---|---|---|
| PF-06838435 Dose-Escalation | Experimental | Biological: PF-06838435 (formerly SPK-9001)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. |
Who may qualify
- Ages
- 18 to 65 years
- Sex
- Male only
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (5 listed)
- Able to provide informed consent and comply with requirements of the study
- Males age 18 to 65 years with confirmed diagnosis of hemophilia B (≤2 IU/dL or ≤2% endogenous factor IX)
- Received ≥50 exposure days to factor IX products
- No measurable factor IX inhibitor as assessed by the central laboratory and have no prior history of inhibitors to factor IX protein
- 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
Key exclusion criteria (9 listed)
- Evidence of active hepatitis B or C
- Currently on antiviral therapy for hepatitis B or C
- Have significant underlying liver disease
- 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)
- Neutralizing antibody titers to the capsid portion of PF-06838435 above the established threshold
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 |
|---|---|---|
| PF-06838435 (formerly SPK-9001)Gene Therapy: A novel, bioengineered adeno-associated viral vector carrying human factor IX variant | Biological | PF-06838435 Dose-Escalation |
Primary outcome
Incidence of PF-06838435 related adverse events
Time frame: Baseline up to Year 6
14 secondary outcomes
Incidence of clinically significant changes from baseline
Time frame: Baseline up to 52 weeks
Incidence of protocol-defined medically important events
Time frame: Baseline up to 52 weeks
Immune response against AAV capsid protein and hFIX transgene
Time frame: Baseline up to 52 weeks
Coagulation Clotting Assay for FIX activity levels
Time frame: 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 FIX Antigen levels
Time frame: Baseline up to 52 weeks
Annualized bleeding rate (ABR)
Time frame: Baseline up to Year 6
Annualized (factor FIX) infusion rate
Time frame: Baseline up to Year 6
Total factor consumption (IU)
Time frame: Baseline up to Year 6
Total number of bleeding events
Time frame: Baseline up to Year 6
Haem-A-QoL
Time frame: Baseline up to Year 6
EQ-5D-5L
Time frame: Baseline up to Year 6
Brief Pain Inventory
Time frame: Year 2 up to Year 6
McGill Pain Questionnaire
Time frame: Baseline up to 52 weeks
Results and safety
The study was stopped early (reason given: The study was terminated early due to Sponsor and participants may transition into a long-term follow-up study. The decision to terminate the trial was not based on any safety and/or efficacy concerns.). Results are not available in the source record.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 5 Oct 2026.
- Derived from this study: PubMed 41734390Samelson-Jones BJ, Rasko JEJ, Ducore JM, McGuinn CE, George LA, von Mackensen S, Borgonuovo G, Agathon D, Smith L, Wilcox LJ, Biondo F, Plonski F. Safety, efficacy, and patient-reported outcomes 6 years after fidanacogene elaparvovec in adults with hemophilia B. Blood Adv. 2026 May 26;10(10):3517-3526. doi: 10.1182/bloodadvances.2025019174.
- Derived from this study: PubMed 40750723Wojciechowski J, Gaitonde P, Hughes JH, Ravva P. Population Modeling of Factor IX Activity Following Administration of Fidanacogene Elaparvovec Gene Therapy in Participants with Hemophilia B. Clin Pharmacokinet. 2025 Oct;64(10):1531-1548. doi: 10.1007/s40262-025-01535-y. Epub 2025 Aug 1.
- Derived from this study: PubMed 40239068Rasko JEJ, Samelson-Jones BJ, George LA, Giermasz A, Ducore JM, Teitel JM, McGuinn CE, High KA, de Jong YP, Chhabra A, O'Brien A, Smith LM, Winburn I, Rupon J. Fidanacogene Elaparvovec for Hemophilia B - A Multiyear Follow-up Study. N Engl J Med. 2025 Apr 17;392(15):1508-1517. doi: 10.1056/NEJMoa2307159.
- 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
25 sites in 4 countries: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Phase 2 study testing PF-06838435 (formerly SPK-9001) in people with Hemophilia B, run by Pfizer at 25 sites in 4 countries.
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 9 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: stopped early, as of the sponsor's last update on 5 Oct 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 25 sites in United States, Canada, Turkey (Türkiye), Australia. 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?
The study was stopped early (reason given: The study was terminated early due to Sponsor and participants may transition into a long-term follow-up study. The decision to terminate the trial was not based on any safety and/or efficacy concerns.). Results are not available in the source record.
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?
Incidence of PF-06838435 related adverse events (time frame: Baseline up to Year 6). 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 NCT03307980, which also lists 3 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 5 Oct 2026.