ISTH 2021 – Biomarin’s valrox fades again

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Biomarin’s haemophilia A gene therapy valoctocogene roxaparvovec (valrox) was already under scrutiny over fading factor VIII levels. An update yesterday from its phase 1/2 trial, presented at the ISTH meeting, will have done nothing to allay those fears. At five years FVIII levels among seven patients treated with the highest dose, 6x1013vg/kg, had dropped to a median of just 8%. Biomarin will no doubt point to the fact that among six of these patients the mean annualised bleeding rate fell by 95% over this period and that, even at five years, 86% of patients had no bleeds. But it is still unclear how long valrox’s effect might last – not ideal for a supposedly once-and-done therapy that cannot be redosed. Valrox is already in a pivotal trial, Gener8-1, and an early look also suggested fading FVIII levels at two years. Two-year results on all participants in Gener8-1 are expected in early 2022. Biomarin might then be able finally to refile valrox, which was rejected by the FDA last year. However, even if it is approved, patients might choose to hang on for something better. Evaluate Pharma sellside consensus puts valrox’s 2026 sales at $695m, down from $1.8bn in April 2020.

FVIII levels with 6e13 vg/kg dose of valrox over time: phase 1/2 results (NCT02576795)
Year Mean Median
1 64.3% 60.3%
2 36.4% 26.2%
3 32.7% 19.9%
4 24.2% 16.4%
5 11.6% 8.2%
Results all with chromogenic substrate assay. Source: company releases.

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