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Fidanacogene elaparvovec

Phase 3

Hemophilia B | Monoclonal antibody | Hematology |Pfizer, Inc.|Last Updated: Aug 11, 2026

Target and mechanism

ModalityMonoclonal antibody

Also known as PF-06838435 (formerly SPK-9001), PF-06838435

Success Probability

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Market & Valuation

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Trial Design

UNCONTROLLEDDMC
Total Trials2
Total Enrollment72

FDA Designations

No designations recorded

Clinical trial landscape

Fidanacogene elaparvovec · 2 trials · 1 indication

Phase 3 1Phase 2 1
NCT03861273A Study to Evaluate the Efficacy and Safety of Factor IX Gene Therapy With PF-06838435 in Adult Males With Moderately Severe to Severe Hemophilia BHemophilia B
ACTIVE NOT_RECRUITING51 Analytics
PHASE3ACTIVE NOT_RECRUITING
A Study to Evaluate the Efficacy and Safety of Factor IX Gene Therapy With PF-06838435 in Adult Males With Moderately Severe to Severe Hemophilia B
Hemophilia BUnlock trial analytics

Study Endpoints

Primary Endpoints

Annualized Bleeding Rate (ABR) for Total Bleeds (Treated and Untreated) From Week 12 to Month 15
Pre-infusion period: minimum of 6 months through first dose of current study, an average of 1.31 years (FIX Prophylaxis arm); Week 12 to Month 15 post infusion in current study (PF-06838435 arm)

ABR = number of total bleeding episodes on study during the given time period) \*365.25/ (Date of last day - date of first day +1) in that time period. Surgical procedures were excluded from summary/analyses. Treated Bleed: An event necessitating administration of coagulation factor within 72 hours of signs or symptoms of bleeding (protocol definition, unless specifically referring to untreated bleed). Untreated Bleed: A bleeding event not necessitating administration of coagulation factor within 72 hours of signs or symptoms of bleeding. This outcome measure compared data collected from lead-in study C0371004 and from current study C0371002. Pre-infusion period = at least 6 months of prospectively collected data while receiving FIX prophylaxis replacement therapy in lead-in study C0371004 up to dosing in current study C0371002.

Incidence of PF-06838435 related adverse events
Baseline up to Year 6

Secondary Endpoints

ABR for Treated Bleeds From Week 12 to Month 15
Pre-infusion period: minimum of 6 months through first dose of current study, an average of 1.31 years (FIX Prophylaxis arm); Week 12 to Month 15 post infusion in current study (PF-06838435 arm)
Annualized Infusion Rate (AIR) of Exogenous FIX From Week 12 to Month 15
Pre-infusion period: minimum of 6 months through first dose of current study, an average of 1.31 years (FIX Prophylaxis arm); Week 12 to Month 15 post infusion in current study (PF-06838435 arm)
Steady State Circulating Factor IX (FIX:C) From Week 12 to Month 15
Week 12 to Month 15
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Study Design & Arms

AllocationNON_RANDOMIZED
MaskingNONE
ModelSINGLE_GROUP
PurposeTREATMENT

Treatment Arms

ArmTypeDescription
PF-06838435/ fidanacogene elaparvovecEXPERIMENTAL -
PF-06838435 Dose-EscalationEXPERIMENTALSingle 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.

Interventions

NameTypeDescription
PF-06838435/ fidanacogene elaparvovecBIOLOGICALGene Therapy
PF-06838435 (formerly SPK-9001)BIOLOGICALGene Therapy: A novel, bioengineered adeno-associated viral vector carrying human factor IX variant
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Eligibility Criteria

Age Range18 Years to 65 Years
SexMALE
Healthy VolunteersNo
Study Sites67

Inclusion Criteria * Males who completed 6 months of Factor IX prophylaxis therapy during the lead-in study (C0371004) prior to providing consent at the screening visit for this study. * Documented moderately severe to severe hemophilia B (Factor IX activity \< =2%) * Previous experience with FIX t...

Countries:United StatesAustraliaBrazilCanadaFranceGermanyGreeceItalyJapanSaudi ArabiaSouth KoreaSpainSwedenTaiwanTurkey (Türkiye)United Kingdom
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Recent Changes (Last 90 Days)

MEDIUMSep 11, 2026NCT03307980TRIAL_REMOVED: changed
MEDIUMSep 11, 2026NCT03307980TRIAL_REMOVED: changed
MEDIUMSep 11, 2026NCT03307980TRIAL_REMOVED: changed
HIGHAug 11, 2026NCT03307980Status: ACTIVE_NOT_RECRUITING → COMPLETED
HIGHAug 11, 2026NCT03307980Status: ACTIVE_NOT_RECRUITING → COMPLETED