UniQure edges closer to haemophilia B gene therapy OK

Dutch biotech UniQure has 12-week data for its haemophilia B gene therapy that backs up an earlier readout at six weeks, and keeps the pressure on rival Spark Therapeutics.

The updated results from a phase 2b study of AMT-061 showed sustained increases in Factor IX (FIX) clotting factor levels in all three patients dosed with the gene therapy, with an average boost of 38% and one patient showing a 51% rise. All three patients had severe haemophilia with FIX levels of less than 1% at enrolment.

UniQure thinks spontaneous bleeds decrease substantially when FIX activity is above 12% of normal, so with all three subjects in the study comfortably topping that level the results suggest AMT-061 should allow patients to reduce their use of recombinant FIX products. No patient suffered a bleed or needed FIX replacement therapy during the 12-week trial period, and importantly the results showed no sign that the efficacy of the therapy as tailing off.

UniQure has been vying to bring an effective haemophilia B therapy to market with Spark and partner Pfizer for some time, but suffered a setback when an earlier version of its candidate (AMT-060) failed to show enough potency in early testing. It subsequently swapped over to a new Factor IX construct – called Padua – that seems to have solved the potency issue. Spark/Pfizer’s SPK-9001 (fidanacogene elaparvovec) is also based on the Padua variant.

With AMT-061 and SPK-9001 both in phase 3 testing on the strength of proof-of-concept data, prospects are looking increasingly good of a one-shot therapy becoming available that could free patients from at least some of the regulator injections of FIX products they currently need to prevent breakthrough bleeding episodes.

According to the clinicaltrials.gov database, UniQure’s phase 3 trial – called HOPE-B – started recruiting its first patients last year and is due to start dosing this qyarter, with results expected in March 2020. Meanwhile, Pfizer and Spark’s phase 3 trial is due to read out in December of that year.

That gives UniQure a shot at being first to market, and the positive results sparked a 10% increase in its share price ahead of the weekend. Also in the hunt is UK-German biotech Freeline, which reported preliminary data from a phase 1/2 trial of its FLT180a candidate at last year’s American Society of Haematology (ASH) meeting

“We are extremely pleased with these updated data,” said UniQure’s chief medical officer Robert Gut (pictured below).

“The study 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,” he added.