Pfizer and Sangamo Therapeutics have reported updated follow-up results from the Phase I/II Alta clinical trial where its experimental gene therapy, giroctocogene fitelparvovec, demonstrated sustained bleeding control in moderately severe to severe haemophilia A patients.
Giroctocogene fitelparvovec is currently being developed in partnership under an international development and marketing agreement between the two companies.
Pfizer obtained the production technology and the Investigational New Drug (IND) application for gene therapy from Sangamo in 2019.
The open-label, multicentre, dose-ranging trial analysed the safety and tolerability of giroctocogene fitelparvovec in individuals with severe haemophilia A.
Findings showed that the five subjects in the highest dose 3e13vg/kg arm were found to have a mean factor VIII (FVIII) activity of 25.4% at 104 weeks.
A mean annualised bleeding rate (ABR) of 0.0 and 1.4 was reported in these subjects in the first year after dosage infusion and during the follow-up period, respectively.
Furthermore, all the events of bleeding happened after week 69 following infusion.
Two individuals had bleeding episodes that required the use of exogenous FVIII without any subjects in the highest dose arm resuming prophylaxis.
In the trial, giroctocogene fitelparvovec was found to be well-tolerated with one subject in the highest dose arm experiencing a treatment-associated serious adverse event of hypotension and fever.
Across all four cohorts, 26 treatment-related adverse events without any cases of FVIII inhibitor development and thrombotic events were observed.
In 2019, the companies reported interim data from Phase I/II Alta trial of SB-525 to treat severe haemophilia A.
Pfizer Rare Disease senior vice-president and chief scientific officer Seng Cheng said: “These latest results further suggest the potential of this investigational therapy to bring transformational benefit to eligible patients living with severe haemophilia A, if confirmed in ongoing clinical trials.”
Another Phase III AFFINE trial of giroctocogene fitelparvovec in patients with haemophilia A has completed more than half of the subject enrolment target.
This trial is currently under the US Food and Drug Administration (FDA) clinal hold due to reports of FVIII levels exceeding 150% in some subjects who received the treatment.
Haemophilia is a haematological rare disease characterised by a deficiency clotting factor VIII, a protein needed for blood clotting.
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