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PF-06838435/ fidanacogene elaparvovec

Phase 3

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

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

PF-06838435/ 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)

HIGHAug 11, 2026NCT03307980Status: ACTIVE_NOT_RECRUITING → COMPLETED
HIGHAug 11, 2026NCT03307980Status: ACTIVE_NOT_RECRUITING → COMPLETED

Frequently asked questions about PF-06838435/ fidanacogene elaparvovec

What is PF-06838435 used for?

PF-06838435, also known as fidanacogene elaparvovec, is an investigational gene therapy being developed for the treatment of hemophilia B. It is intended for adult males with moderately severe to severe hemophilia B. The drug is currently in Phase 3 clinical development and is not yet approved by regulatory authorities.

What does PF-06838435 target?

PF-06838435 is a gene therapy designed to deliver a functional copy of the factor IX gene to patients with hemophilia B. Hemophilia B is caused by a deficiency in factor IX, a protein essential for blood clotting. By providing the correct gene, the therapy aims to enable the body to produce factor IX and reduce bleeding episodes.

Who makes PF-06838435?

PF-06838435 is being developed by Pfizer, Inc., a multinational pharmaceutical company listed on the New York Stock Exchange under the ticker symbol PFE. Pfizer is conducting clinical trials to evaluate the safety and efficacy of this gene therapy for hemophilia B.

What phase is PF-06838435 in?

PF-06838435 is currently in Phase 3 clinical development. It has completed a Phase 2 trial and is now being evaluated in an active Phase 3 study. The drug is investigational and has not received FDA approval or any other regulatory approval for commercial use.

What clinical trials is PF-06838435 in?

PF-06838435 has been studied in two clinical trials. The first, NCT03307980, was a Phase 2 study that has been completed, involving 21 participants. The second, NCT03861273, is an active Phase 3 trial with 51 participants. Both trials are studying the drug in adult males with hemophilia B.

Is PF-06838435 the same as fidanacogene elaparvovec?

Yes, PF-06838435 is the same as fidanacogene elaparvovec. PF-06838435 is the code name used during development, while fidanacogene elaparvovec is the international nonproprietary name. Both names refer to the same investigational gene therapy for hemophilia B.