• ClinicalTrials.gov Identifier: NCT02484092¹
• A Phase 1/2, Open-Label, Non-Randomized, Dose-Escalation 
• Study of SPK-9001 in Subjects with Hemophilia B

• Completed*, Last Update Posted: June 16, 2020¹
• Follow up continuing on P1/2a study. P3 trial ongoing
• Last Update Posted: June 16, 2020
• Approval status: According to a supporting document⁶ on the FDA page,
  fidanacogene elaparvovec was approved by the FDA on May 20, 2024

• Male and ≥18 years of age have
• Hemophilia B with ≤2 IU/dL (≤2%) endogenous FIX activity levels as of the normal value
• Had ≥50 prior EDs to any FIX protein products    

• Have anti-AAV-Spark100 neutralizing antibody titers ≥1:5 
• Participation in a previous gene therapy research trial within the last 52 weeks

Bioengineered capsid AAV-Spark100²/ HEK293 cells

Codon-opimized FIX-Padua²

The FIX expression cassette includes:

• APOE gene hepatic-control region (APOE-HCR) enhancer and the
• Liver-specific human α1 -antitrypsin (hAAT) promoter²

Systemic³

Infusion of single vector dose as follows:

• 5e11 (10) reported here² and subsequently 
• 5e11 (15) reported here^1, 4-5

• 28 to 78 weeks as reported here²
• ≥ 52 weeks as reported here ^4-5

Further statements regarding the follow-up were collected from here⁵ and summarized as follows:

• All 15 pts. completed the phase 1/2a study for 52 weeks and were eligible to enroll in a long-term follow-up (LTFU) of ≤5 years
• As of August 2022, 8 pts, were continuing, 4 completed, and 2 discontinued the LTFU (3–6 years post vector infusion)

OS^2, 4

Sustained steady-state factor IX–R338L expression was reached within 14 weeks after vector infusion and reported by 2 publications as follows:

• Among all pts. mean (± SD) steady-state vector-based FIX coagulant activity was 33.7 ± 18.5% of the normal value²
• The mean (± SD) post-infusion steady-state FIX:C was 22.9% ± 9.9% at 1-year post vector infusion⁴ 

Peak and steady-state vector-derived circulating FIX activity levels were determined in a time frame from W12 up to W52, as reported on clinicaltrials.gov,¹ 
as follows:

• Mean (SD) peak FIX activity: 29.1 (11.63)
• steady-state level of 22.9 (9.89) % of normal

For all pts., FIX activity generally remained in the mild to normal range post infusion for up to 6 years⁵

Peaks not reported, possibly W28 based on Fig. 1²

• The ABR mean was reduced from 11.1 events per year [range, 0 to 48] before vector administration to a mean rate of 0.4 events per year [range, 0 to 4] after vector administration²
• That corresponds to 96% reduction of the mean bleeding rate per year

    ABRs for the time period of six years and data concerning further characteristics of bleeding events were reported here⁵ as follows:

    ^a At enrollment in the phase 1/2a study, the majority of patients had target joints and/or joint arthropathy at baseline
    ^b All target joints or with known arthropathy
    ^c Occurred in joints in 2 patients who also had bleeds in the 1/2a study
    ^d In 1 pt., 6 of 10 bleeds were in target joints or joints with known arthropathy and 3 bleeds were in a wrist with known carpel tunnel syndrome
    ^e In the other pt., 3 bleeds occurred over 1.7 years in the same joint that was not a target joint and did not have known arthropathy
    ^f 4 were in joints; only 1 was not in a target joint or joint with known arthropathy

The mean use of FIX concentrate in the 52 weeks before screening and after vector infusion was reduced from 2908 IU/kg [range, 0 to 8090] to 49.3 IU/kg [range, 0 to 376]²

No SAEs occurred during or after vector infusion²

AEs likely related to the study vector were taken from here² and summarized as follows:

• 1/10 pts. (P9) experienced transient grade 1 elevation of ALT level (to >2.5 X the ULN range) that was the only AE that was deemed to be likely related to the study vector
• P7 had an increase in liver-enzyme levels above baseline within the range of normal values that did not meet the criteria regarding toxic effects

No AEs related to glucocorticoid in the 2/10 pts. that took prednisone observed²
  

• 2/10 pts. with peak levels of approx. 70-140 U/L at W5 and W9 according to Fig. 2²
• 3/15 pts. were treated with corticoids for elevations in hepatic transaminases but peak level and timing not reported⁴

• 2/10 pts. with peak levels of approx. 50-80 U/L at W5 and W8 according to Fig. 2²
• 3/15 pts. with hepatic enzyme elevations, but peak levels and timings were not reported⁴

• 2/10 pts. that experienced ALT elevation had also peak values of 330 SFU/1e6 PBMCs at W6 and of 1200 SFU/1e6 PBMCs at W5²
• In the 3/15 pts. with hepatic enzyme elevation, 2 pts. were positive for capsid reactive T cells by interferon-γ ELISpot but peak values and timings were not reported (n=15)⁴

Yes, P7 and P9 received prednisone for a total of 130 and 119 days as reported in in the supplementary appendix here²

Yes, in 1/2 pts. with ALT/AST elevations + T-cell response FIX coagulant activity declined from 48% to 30% on day 56 and to 18% on day 62²

Not reported

1. A Gene Therapy Study for Hemophilia B. Available at: Study Details | A Gene Therapy Study for Hemophilia B | ClinicalTrials.gov
2. George, L.A., et al., Hemophilia B Gene Therapy with a High-Specific-Activity Factor IX Variant. N Engl J Med, 2017. 377(23): p. 2215-2227. Hemophilia B Gene Therapy with a High-Specific-Activity Factor IX Variant | NEJM
3. Nathwani, A.C., Gene therapy for hemophilia. Hematology Am Soc Hematol Educ Program, 2019. 2019(1): p. 1-8. Gene therapy for hemophilia - PMC (nih.gov) 
4. George, L.A., et al., Efficacy and Safety in 15 Hemophilia B Patients Treated with the AAV Gene Therapy Vector Fidanacogene Elaparvovec and Followed for at Least 1 Year. Blood, 2019. 134(Suppl. 1): p. 3347. Efficacy and Safety in 15 Hemophilia B Patients Treated with the AAV Gene Therapy Vector Fidanacogene Elaparvovec and Followed for at Least 1 Year | Blood | American Society of Hematology (ashpublications.org)
5. Rasko, J.E.J., et al., PATTERNS OF JOINT BLEEDS IN PATIENTS WITH HEMOPHILIA B FOLLOWING FIDANACOGENE ELAPARVOVEC ADENO-ASSOCIATED VIRUS GENE THERAPY. Haemophilia, 2023. 29. POSTER ABSTRACTS - Mulders - 2023 - Haemophilia - Wiley Online Library
6. FDA BLA Approval Document. Available at: April 25, 2024 Approval Letter - BEQVEZ (fda.gov)

AAV, Adeno-associated virus; ABR, Annualized bleeding rate; AEs, adverse events; AIR, Annualized FVIII/FIX infusion rate; ALT, alanine aminotransferase; AST, aspartate aminotransferase; CH, Chromogenic Assay; Co., cohort; DOACs, Direct oral anticoagulants; D, days; EDs, exposure days; FIX, factor IX; FIX-Padua, gain of function FIX variant; FVIII, factor VIII; gc, genome copies; HEK cells, human embryonic kidney cells; IQR, interquartile range; IRR, Infusion-related reaction; NAbs, neutralizing antibodies; OS, One-stage clotting assay; Pop., population; pt., patient/participant; pts., patients/participants; P1, Participant 1; PI, phase I; PBGD, porphobilinogen deaminase; PBMC, peripheral blood mononuclear cells; SAEs, serious adverse events; SFU, spot-forming units; TAC, tacrolimus; ULN, upper limit of normal; VCN, vector copy number; vg, vector genomes; W, weeks; WT, wild type; Y, year