Endo 2022 – Voxzogo’s prospects shrink

The prospects for Biomarin’s achondroplasia therapy Voxzogo in very young children had already looked murky after a vague update earlier this year. Now the company has given – some – further details, and things are still far from clear. The results, presented in a poster at the Endo meeting, came from a phase 2 study in under-fives. Biomarin touted a placebo-adjusted 0.92cm/year increase in annualised growth velocity – below the 1.57cm/year seen in a separate trial in patients aged five and over, for whom Voxzogo is already approved. What is more, the former figure included so-called “sentinel subjects” – patients who received open-label Voxzogo at the start of each new age group cohort. Biomarin did not disclose growth velocity results for randomised patients only, suggesting that these were “less good, and/or more fraught with noise”, as Stifel analysts put it. The company did give more details of Z-scores, a measure of how much a given value deviates from the mean, used to track the growth of very small children. However, the Z-score was less impressive when only randomised patients were included. Stifel reckons the latest data are “probably enough” for label expansion, but without more information this looks tough to call.

Cross-trial comparison of Vozxogo's effect in over and under fives
  Ph2 in pts <5 (NCT04554940) Ph3 in pts ≥5 (NCT03197766)
  Randomised pts only Incl sentinel subjects 
Annualised growth velocity (cm/year) Not given 0.92 1.57
Height standard deviation score* 0.25 0.30 0.28
*This is referred to as Z-score by Biomarin. All values placebo adjusted. Source: company release & product label.

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