UniQure’s hemophilia B gene therapy clears another clinical test

uniQure
UniQure's offices. (uniQure)

UniQure has posted 12-week data on its hemophilia B gene therapy. The update suggests FIX activity increases seen at six weeks are sustainable, giving uniQure a boost as it races Spark Therapeutics to market. 

Amsterdam-based uniQure was dogged by unfavorable comparisons to Spark’s Pfizer-partnered gene therapy throughout early development, prompting it to replace its wild-type FIX gene therapy with the FIX-Padua variant AMT-061. Six-week data from three patients released last year showed the switch had yielded to desired jump in FIX activity but left key questions unanswered.   

The 12-week data released Friday mark another step in uniQure’s efforts to answer those questions. Importantly, the effects seen at six weeks have continued and intensified as the trial has continued.

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By the 12-week cutoff, mean FIX activity had increased to 38% of normal, compared to 31% at the six-week point. The performance reflects sustained, clinically significant increases in FIX activity in all three patients, who had levels ranging from 25% to 51% at the last count. 

To put that in context, FIX activity in patients who took uniQure’s previous, wild-type gene therapy rarely topped 10%. The data are also in the same ballpark as results generated by Spark’s SPK-9001, the latest version of which triggered FIX activity levels of 38.1% to 54.5%. 

AMT-061, like SPK-9001, looks to significantly reduce, and potentially eliminate, the risk of bleeding, as would be expected at the FIX levels seen in the trials. None of the patients who received AMT-061 suffered bleeding events or required FIX replacement therapy after taking the gene therapy. All the subjects suffered spontaneous bleeds in the period preceding treatment.

With the only blot on the safety profile of AMT-061 being the slight, previously reported increase in aspartate aminotransferase—which resolved without treatment or loss of FIX activity—uniQure looks well-placed to deliver a genuine rival to Spark’s SPK-9001.

The larger pivotal programs now underway could change that picture, to either or neither of the biotechs’ benefit, but for now it remains possible that two comparably effective hemophilia B gene therapies will come to market around the same time. If that happens, small factors, such as the efficacy of AMT-061 in people with neutralizing antibodies against SPK-9001, could influence how the market shakes out.

Shares in uniQure rose 5% in premarket trading following the news. The stock is up around 50% since the publication of the six-week data on AMT-061.  

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