As Sanofi buyout nears, Ablynx lupus drug flunks midphase trial

The study failed to detect a dose response at week 24 according to a lupus assessment score, causing it to miss its primary endpoint. (Image: Ablynx)

A phase 2 trial of Ablynx’s vobarilizumab in systemic lupus erythematosus (SLE) has missed its primary endpoint. The setback tarnishes one of the drugs Sanofi is set to acquire through its €3.9 billion ($4.8 billion) takeover of Ablynx.

Investigators enrolled 312 patients with moderate to severe, active seropositive SLE and randomized them to receive one of four doses of anti-IL-6R single-domain antibody vobarilizumab or placebo.

The study failed to detect a dose response at week 24 according to a lupus assessment score, causing it to miss its primary endpoint. Ablynx drew on multiple lupus assessments to design the composite score, which was intended to evaluate SLE disease activity in all body systems.

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Ablynx is yet to present a look at the data but the details that are available suggest vobarilizumab will struggle to bounceback in SLE. The trial was large and rigorous. And Ablynx saw no differences in the baseline characteristics of the five cohorts or other factors that could have confounded the result in its initial analysis. The Belgian biotech is still working through the full dataset.

If the phase 2 results deal a terminal blow to vobarilizumab in SLE, it will close off one opportunity for Sanofi to recoup the €3.9 billion it is set to pay for Ablynx. But the drug was never a focal point of the takeover.

With AbbVie having an option to license the drug in SLE, midphase success would likely have seen Sanofi’s returns from the program limited to fees, milestones and royalties. Ablynx has full control of the drug in rheumatoid arthritis—having been dumped by AbbVie in 2016—but Sanofi focused its rationale for the takeover on other assets, notably acquired thrombotic thrombocytopenic purpura drug caplacizumab and anti-RSV program ALX-0171.

If AbbVie turns down the chance to license vobarilizumab in SLE, Sanofi will acquire full control of a drug that failed to wow in midphase trials. Ablynx saw the rheumatoid arthritis data as supporting a move into phase 3, but AbbVie walked away, no other partner emerged and an anticipated end-of-2017 start date for the pivotal trial came and went.