UniQure says AMT-061 gene therapy increases FIX activity in haemophilia B mid-stage study

uniQure on Thursday announced top-line results from a Phase IIb study of AMT-061 for the treatment of patients with severe and moderately severe haemophilia B, with the gene therapy achieving sustained levels of Factor IX (FIX) activity at six weeks after a single administration. The company said that it expects to initiate dosing in the pivotal Phase III HOPE-B trial of AMT-061 in the first quarter of 2019. Shares in uniQure jumped as much as 50 percent on the news. 

The Phase IIb study enrolled three patients with severe haemophilia who received a single intravenous infusion of AMT-061 at 2x1013 vc/kg. Results showed that six weeks after administration, mean FIX activity for the three patients was 31 percent of normal, which uniQure said "exceeding threshold FIX levels generally considered sufficient to significantly reduce the risk of bleeding events."  

According to the company, the first patient achieved FIX activity of 37 percent of normal at 10 weeks after administration, while it was 23 percent of normal at eight weeks in the second subject and 30 percent of normal at six weeks after administration in the third participant. uniQure indicated that patients will be followed for 52 weeks to examine the effects of AMT-061 on FIX activity, bleeding rates and the use of FIX replacement therapy, with patients also monitored for five years to evaluate the safety of the therapy.  

uniQure chief medical officer Robert Gut, who noted that the drugmaker was "pleased" with the results, stated "based on the long-term FIX data from our Phase I/II trial of AMT-060, where we saw FIX activity levels continue to increase beyond the levels achieved at six to ten weeks, we are hopeful that we will continue to see similar trends in these patients." 

The news comes after Pfizer and Spark Therapeutics unveiled positive early-stage clinical data for the investigational adeno-associated virus vector SPK-9001 in patients with haemophilia B. Leerink analyst Joseph Schwartz previously estimated that if uniQure observed FIX levels of 20 percent to 35 percent for the three patients, it would be "on-track to matching SPK-9001's profile." 

Meanwhile, in the HOPE-B study, uniQure plans to enrol about 50 adults with severe or moderately severe haemophilia B, who will receive a single dose of AMT-061 after a six-month lead-in period. The company said that the primary endpoint of the study will be the FIX activity level, while secondary endpoints will include annualised bleed rates, annualised FIX replacement therapy use and safety.  

uniQure explained that AMT-061 features an AAV5 vector carrying a gene cassette with the Padua variant of FIX, which reportedly provides a gain of function compared with wild-type FIX protein, which was featured in AMT-060. The experimental treatment has been awarded breakthrough therapy status by the FDA and PRIME designation by the European Medicines Agency. 

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