Phase 3 fail prompts Ultragenyx to can muscle disease drug

A phase 3 fail wiped more than 10% off Ultragenyx's share price.

Ultragenyx has given muscle disease candidate Ace-ER the heave-ho after it failed in phase 3. The GNE myopathy trial missed its primary endpoint and all key secondary endpoints, delivering a blow to Ultragenyx as it enters a critical period for its prospects.

Investigators enrolled 89 patients with the enzyme deficiency disease and randomized them to receive either Ace-ER, an extended-release formulation of aceneuramic acid, or placebo for 48 weeks. The study monitored the change in upper extremity composite (UEC) scores for the primary endpoint. It also kept tabs on other measures of muscle strength and physical functioning for the key secondary endpoints.

Ace-ER failed to outperform placebo against any of these endpoints. The study linked Ace-ER to a 0.74 kg improvement in UEC score over placebo, a marginal gain that fell well short of statistical significance. Ultragenyx has yet to share a look at the data for the secondary endpoints, but snuffed out any hopes for the program by disclosing it failed to beat placebo against these measures.


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The clean sweep of failures prompted Ultragenyx to abandon the drug immediately, rather than go digging in the data in search of a reason to continue. Shares in Ultragenyx, which has a market cap of $2.5 billion, were down 14% in premarket trading.

The moderate decline is testament to the prospects Ultragenyx has elsewhere in its pipeline and the mixed data Ace-ER generated before entering late-phase development. 

When paired to belief in the idea of using Ace-ER to offset deficiencies in sialic acid, the positives in the phase 2 data outweighed the negatives to the extent Ultragenyx pushed ahead into phase 3. But the questions raised by the earlier inconclusive data mean the phase 3 fail is unlikely to be a big shock for many observers.

Ultragenyx’s swift decision to cut the asset loose frees it to focus on drugs for which expectations are higher. The rare disease specialist has a PDUFA date for its treatment of mucopolysaccharidosis VII in the diary for November, with a decision by authorities in Europe set to follow in the first half of next year. 

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