Gene Therapy AMT-061 Effective 6 Months After Single Dose in Hemophilia B Patients, Ongoing Phase 2b Trial Suggests

A single infusion of AMT-061, an investigational gene therapy for hemophilia B, continues to maintain clinically significant increases in clotting factor IX (FIX) up to six months after its administration, as demonstrated in all three patients enrolled in uniQure’s ongoing Phase 2b trial.

FIX activity was raised to nearly half of the levels normally found in healthy people, and none of the patients has required factor infusions or reported bleeding events so far, a press release states.

The updated data were presented at the 2019 Scientific Symposium of Hemostasis & Thrombosis Research Society, which took place May 9–11 in New Orleans, Louisiana.

The Phase 2b trial (NCT03489291) is an open-label, dose-confirmation study that enrolled three patients in the U.S. with severe hemophilia B (less than 1% of FIX activity). The first patient entered the study last year.

Participants received a single intravenous infusion of AMT-061, and over the course of one year will be monitored for FIX activity, bleeding rates, and usage of FIX replacement therapy.

AMT-061’s safety, including adverse events, will be monitored for five years after its administration.

The recently released results showed clinically significant increases in FIX that were maintained up to six months after a single shot of AMT-061. Two of the three patients achieved FIX activity within the normal range found in healthy people. FIX activity increased to 51% of normal levels in one patient, 33% in another patient, and up to 57% of the normal levels in the last patient.

This means that the patients’ mean FIX activity levels improved to 47% of what is normally found in healthy people — exceeding the levels considered enough to eliminate or significantly reduce the risk of bleeding events, the company states.

Moreover, during the six months of follow-up, no patients have reported serious adverse or thrombotic events, or developed FIX inhibitors.  

“We believe these to be striking clinical data that show AMT-061 has the potential to deliver consistent and sustained increases in Factor IX activity into the range considered normal,” said Robert Gut, MD, PhD, chief medical officer of uniQure.

“Further, AMT-061 continues to be safe and well tolerated, with no patients requiring immunosuppression related to the therapy,” he added.

Another important observation was that two of the enrolled patients, who have been responding positively to AMT-061, had been excluded from another gene therapy study because they had developed antibodies against that therapy’s viral vector.

AMT-061 is an investigational gene therapy based on the viral vector AAV5. The vector carries a genetically engineered version of clotting FIX called the Padua variant (FIX-Padua), which leads to an about eight- to nine-fold increase in FIX activity.

In 2017, AMT-061 was granted Breakthrough Therapy Designation by the U.S. Food and Drug Administration and Priority Medicines status by the European Medicines Agency.

“We are excited to share these updated data and are working hard toward our goal of making AMT-061 available to patients living with hemophilia B as rapidly as possible,” stated Matt Kapusta, CEO of uniQure. “We believe that these updated data continue to suggest that AMT-061 may be the first gene therapy able to achieve this goal, and we remain highly focused on completing enrollment in our ongoing pivotal Phase III study by the end of the year.”

uniQure is currently recruiting patients for the HOPE-B Phase 3 trial (NCT03569891) which seeks to demonstrate the effectiveness and further confirm the safety of AMT-061 in men with severe to moderately severe hemophilia B.

Patient recruitment is open at sites in the U.S., Europe, and the U.K. For more information on contacts and locations, visit the official site at clinicaltrials.gov.