Alnylam Pharmaceuticals has launched a Phase III clinical trial of lumasiran to treat primary hyperoxaluria type 1 (PH1) in paediatric patients.

Dubbed ILLUMINATE-B, the open-label, global, multi-centre Phase III trial will assess the safety and efficacy of the drug candidate in around eight patients under the age of six.

The dosing regimen in the trial will be based on the weight of the participant.

The primary endpoint of the study is the percentage decrease in urinary oxalate at six months from baseline, while key secondary and exploratory endpoints include urinary oxalate, estimated glomerular filtration rate (eGFR), safety, tolerability and quality of life.

Initial trial data is expected to be available by mid-next year.

“This study adds to our overall clinical development plan for lumasiran, led by our ILLUMINATE-A pivotal study.”

Lumasiran is an investigational RNAi therapeutic formulated for subcutaneous administration.

It is designed to target glycolate oxidase (GO) and reduce the enzyme’s hepatic levels. This leads to a decrease in the substrate required to produce oxalate, the metabolite directly linked to the PH1 pathophysiology.

Alnylam Pharmaceuticals Lumasiran programme vice-president and general manager Pritesh Gandhi said: “We are pleased to start the ILLUMINATE-B paediatric trial, an important step forward in our goal to assess the safety and efficacy of lumasiran across the PH1 age and disease severity continuum, including patients in early infancy.

“This study adds to our overall clinical development plan for lumasiran, led by our ILLUMINATE-A pivotal study with results expected by year-end 2019.”

Concurrently, the company reported positive efficacy data from the Phase II open-label extension (OLE) study that is evaluating the long-term safety and efficacy of lumasiran.

Results showed a 72% mean maximal decrease in urinary oxalate excretion compared to Phase I/II baseline values across all dose cohorts in the OLE study. At day 85, the mean reduction was observed to be 69%.

The drug candidate also led to a mean maximal reduction of 77% in urinary 24-hour oxalate:creatinine ratio relative to the Phase I/II baseline values. The mean reduction at day 85 was 70%.