UniQure's gene therapy AMT-061 continues to show sustained therapeutic levels of Factor IX activity in mid-stage haemophilia B trial

UniQure on Friday unveiled updated results from an ongoing Phase IIb study illustrating that the experimental AAV5-based gene therapy AMT-061 was associated with mean Factor IX (FIX) activity of 38 percent of normal at 12 weeks after administration in patients with severe and moderately severe haemophilia B. Chief medical officer Robert Gut commented that the study, which was presented at the European Association for Haemophilia and Allied Disorders (EAHAD) annual meeting, "demonstrates AMT-061 has the potential to increase FIX activity into the normal range and continues to be very well tolerated, with no serious adverse events reported and no patients requiring any immunosuppression therapy." 

Last November, the company announced top-line results from the same study showing that a single administration of AMT-061 was linked to mean FIX activity that was 31 percent of normal after six weeks. 

The single-arm study enrolled three patients with severe haemophilia B who received a single intravenous infusion of AMT-061 at 2x1013 vc/kg. The company noted that prior to the administration of AMT-061, all three patients showed low levels of pre-existing antibodies to AAV5, but were not excluded from the trial on that basis. FIX activity was analysed in the trial using an activated partial thromboplastin time assay. 

According to uniQure, the latest results show that the gene therapy continues to "[exceed] threshold FIX levels generally considered sufficient to eliminate or significantly reduce the risk of bleeding events." The company also reported that one of the patients achieved FIX activity that was 51 percent of normal at 12 weeks after administration, while the two other patients displayed respective increases of 48 percent after 16 weeks and 25 percent after 14 weeks.

Further, uniQure said none of the patients exhibited a material loss of FIX activity, reported any bleeding events or required FIX replacement therapy. "As previously reported, one patient experienced slight elevations in aspartate aminotransferase, which quickly resolved without any additional treatment or loss of FIX activity," the company stated, adding that no patient experienced any material elevation in alanine aminotransferase after the administration of AMT-061. UniQure indicated that patients will be followed for 52 weeks to assess FIX activity, bleeding rates and FIX replacement therapy use.

Commenting on the news, analyst Elemer Piros of Cantor Fitzgerald remarked that "with the FIX activity observed to date, we believe these patients could feel better without seeing signs of disease." Meanwhile, Chardan analyst Gbola Amusa said "we'll say it again, Phase II data point to uniQure as [a mergers and acquisitions] target," adding that the latest results "continue to support a blockbuster opportunity for AMT-061 to make haemophilia B patients phenotypically normal."

The company suggested that given the latest results, it was confident of receiving speedy approval from US regulators. AMT-061 was previously granted breakthrough therapy status by the FDA and PRIME designation by the European Medicines Agency. Last year, Pfizer and Spark Therapeutics unveiled positive early-stage data for the investigational adeno-associated virus vector SPK-9001 in patients with haemophilia B.

For related analysis, see ViewPoints: uniQure's haemophilia persistence starts to pay off.

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