• ClinicalTrials.gov Identifier: NCT03003533¹ (A Gene Transfer Study for Hemophilia A) and
  NCT03432520² (Long-Term Safety and Efficacy of Spark-Sponsored Gene Therapies in Males With Hemophilia A)
• A phase 1/2 study³

The status of the trial was reported on ClinicalTrials.gov¹ as follows:

• Active, not recruiting
• Last Update Posted: July 10, 2023

The key inclusion criteria were reported here^3, 4, 5 as follows:

• Male ≥18 years of age
• Plasma FVIII activity levels ≤ 2% of normal
• Have received >150 EDs to FVIII concentrates or cryoprecipitate
• <1:1 neutralizing antibodies titers to SPK200 capsid
• Experienced >10 bleeding events over the previous 12 months prior to screening
• No measurable inhibitors or history of clinically significant inhibitors

The key exclusion criteria were reported here^4, 5 as follows:

• Participated in a gene transfer trial within the last 52 weeks or in a clinical trial with an investigational product within the last 12 weeks
• Active hepatitis B or C
• Significant underlying liver disease
• Serological evidence of human immunodeficiency virus (HIV) with CD4 counts ≤200/mm3

Data regarding the utilized AAV serotype and the vector manufacturing platform were collected from here^3, 5  and summarized as follows:

• Bioengineered AAV, LK03/Spark200
• Plasmid/HEK293 cells

B domain–deleted FVIII (FVIII-SQ) with no CpG motifs in the open reading frame under the control of a liver-specific promoter^3, 5 

Data regarding the utilized expression cassette components were collected from here^3, 5 and summarized as follows:

• Liver-specific promoter consisting of a truncated transthyretin enhancer and a truncated transthyretin promoter
• The FVIII expression cassette also includes a synthetic intron sequence and a rabbit beta-globin polyA signal

Systemic – intravenous infusion³

Follow-up times were reported here^{1, 2, 3} as follows:

• Phase 1/2 study - 52 weeks follow-up¹
• Long-term study has a follow-up period of 9 years, ensuring 10 years of follow-up post-infusion²

One-stage FVIII assay (OS)³

* Participant terminated study participation due to site closure;

† Sample >208 weeks unable to be processed. Analysis includes participants with >52 weeks of follow up (n=16);
   data for two participants (#5 & #12), who lost compete transgene FVIII expression following presumed capsid immune response, are censored.

The subsequent information was extracted from here^3,* and summarized as follows:

• The initial peak FVIII expression occurred 6 - 12 weeks after vector administration across all the dose cohorts
• Pts. in the “low dose cohorts” (5e11 - 1e12 vg/kg) reached plateau FVIII activity by 12 weeks 
• Pts. in the “high dose cohorts” (1.5-2e12 vg/kg) except P6 reached plateau expression by 26 to 52 weeks

^* Data cut-off May 3, 2021; 18 participants; median efficacy follow-up 33.4 months (range 3.7 to 47.6)

Information related to ABR data was collected from here^3-4 and is summarized as follows:

     ^* Data cut-off May 3, 2021; 18 participants; median efficacy follow-up 33.4 months (range 3.7 to 47.6)
 

• 76% of participants had an ABR of <1 for treated bleeds and 90% of participants had an ABR of <1 for spontaneous bleeds

     ^† Data cut-off Oct 4, 2022; 23 participants; median efficacy follow-up: 172.1 (2-285) weeks
 

Median annualized numbers of FVIII infusions per year before and per year after vector administration were reported here^3, 4 as follows: 

    ^* Data cut-off May 3, 2021; 18 participants; median efficacy follow-up 33.4 months (range 3.7 to 47.6)
    ^† For Participants 5 & 12, the reported efficacy data were based on observations before loss of FVIII expression
 

    ^†† Data cut-off Oct 4, 2022; 23 participants; median efficacy follow-up: 172.1 (2-285) weeks
 

Information related to IRR data was collected from here^3, 4 and is summarized as follows:

• 1/24 participants (P5; 2e12 vg/kg cohort) had an infusion reaction consisting of vomiting, myalgia, back pain and pyrexia
• This IRR resolved within 72 hours outpatient antipyretic therapy

* Data cutoff Oct 4. 2022; Median range follow-up (n=24); 191 (2-285 weeks)

* There were no drug-related adverse events or serious adverse events in 5×1011 and 1×1012 vg/kg cohorts.
Data cut-off May 3, 2021; 18 participants; median safety observation period 36.6 months (range 5.5 to 50.3)

Additional Safety Information was reported in the ASH 2022 Croteau presentation^4,*  , as follows:

• No deaths, no FVIII inhibitor development, and no thrombotic events were reported in any of the 24 study participants.
• Eleven participants experienced elevated LFTs. All events were transient, asymptomatic, and resolved.
• AEs related to immunomodulatory agents were mild to moderate and reported in 8 participants
• These events included weight gain, insomnia, irritability, fatigue, hypertension, neutropenia, decreased appetite, stomach
  pain, nausea, headache, hyperactivity, hot flushes, generalized edema, acne, hypomagnesemia, and muscle cramping
• By the October 4, 2022 cutoff, all of these AEs resolved, except hypertension (n=1), headache (n=1) and nausea and stomach pain (n=1)

^* Data cutoff Oct 4. 2022; Median range follow-up (n=24); 191 (2-285 weeks)

11 participants reported ALT elevations⁴ as follows:

• Grade 1 (n=9)
• Grade 2 (n=1)^*
• Grade 3 (n=1)

^* The Grade 2 ALT elevation was deemed an SAE due to in elective hospitalization for IV steroid administration. Data cut-off Oct 4, 2022

Not reported ^3, 4

Not reported

Information regarding use and duration of steroid treatment was collected from here^3, 6 and is summarized as follows:

• In total, 17/23 Participants received corticosteroids*
• All corticosteroids were started within 12 weeks
  • Median (range) time to initiation of reactive corticosteroids (n=12) † was 9.3 (4.3- 12.1) weeks
  • Median (range) duration of treatment was 8.5 (2.0-18.0) weeks
• Corticosteroids were administered prophylactically in 5 participants 2-4 weeks following vector administration
  • The length of exposure in 4 participants was prolonged (31–49 weeks); attempted corticosteroid tapering resulted in changes associated with presumed capsid immune response in all 4 participants.
• All five participants who received prophylactic corticosteroids and four participants who received reactive corticosteroids experienced a recurrence of one or more laboratory trigger(s) potentially
  linked to a presumed capsid immune response during their corticosteroid taper

*Data cut-off June 30, 2022. A. Gray shaded rows indicate two participants (#5 & #12) who lost compete transgene FVIII expression and initiated emicizumab following presumed capsid immune response
† Dose of SPK-8011: 1 × 1012 vg/kg, n=2; 2 × 1012 vg/kg, n=5; 1.5 × 1012 vg/kg, n=5
 

2/24 participants (2e12 vg/kg cohort; Participants 5 & 12) lost expression after a presumed cellular immune response against SPK200^*, 3-4 
* Data cut-off Oct 4, 2022

None ^3-4

1. A Gene Transfer Study for Hemophilia A. Available at: https://clinicaltrials.gov/study/NCT03003533?cond=NCT03003533&viewType=T able&rank=1. NLM identifier: NCT03003533. Accessed July 31, 2023.
2. Long-Term Safety and Efficacy of Spark-Sponsored Gene Therapies in Males With Hemophilia A. Available at: https://clinicaltrials.gov/study/NCT03432520?cond=NCT03432520&rank=1.NL M identifier: NCT03432520. Accessed July 31, 2023.
3. George LA, Monahan PE, Eyster ME et al. Multiyear Factor VIII Expression after AAV Gene Transfer for Hemophilia A. N Engl J Med. 2021.18;385(21):1961-1973. Multiyear Factor VIII Expression after AAV Gene Transfer for Hemophilia A | NEJM
4. Croteau SE, Eyster ME, Tran H, et al. Long-term durable FVIII expression with improvement in bleeding rates following AAV-mediated FVIII gene transfer for hemophilia A: multiyear follow-up on the phase I/II trial of SPK-8011 [oral presentation]. Presented at The American Society of Hematology (ASH) Annual Meeting & Exposition; December 12, 2022. Long-Term Durable FVIII Expression with Improvements in Bleeding Rates Following AAV-Mediated FVIII Gene Transfer for Hemophilia A: Multiyear Follow-up on the Phase I/II Trial of SPK-8011 | Blood | American Society of Hematology (ashpublications.org)
5. George LA, Monahan PE, Eyster ME et al. Multiyear Factor VIII Expression after AAV Gene Transfer for Hemophilia A (Suppl). N Engl J Med. 2021.18;385(21):1961-1973. FINAL R2 SUPPLEMENTARY APPENDIX CLEAN no numb. 7.26.21.docx (nejm.org)
6. Evans MS, Rybka WB, Croteau SE, et al. The effects of immunomodulation with corticosteroids to manage an AAV capsid immune response in the phase I/II study of SPK-8011. Poster presented at: The American Society of Hematology (ASH) Annual Meeting & Exposition; December 12, 2022; New Orleans, LA. Abs 4779. The Effects of Immunomodulation with Corticosteroids to Manage an AAV Capsid Immune response in the Phase I/II Study of SPK-8011 | Blood | American Society of Hematology (ashpublications.org)

AAV, Adeno-associated virus; AEs, 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