Patients with a rare form for amyloidosis with polyneuropathy could soon have access to a new subsidised therapy, with the Pharmaceutical Benefits Advisory Committee supporting a PBS listing for patisiran.

The drug is a novel small interfering RNA therapy that attaches to mRNA to inhibit the mutant TTR gene that produces the transthyretin protein causing TTR-related amyloidosis.

Per the recommendation, the treatment would be available for the treatment of patients with (hereditary transthyretin-mediated) hATTR amyloidosis with polyneuropathy, (also referred to as variant ATTR amyloidosis, ATTRv).

Estimated to number about 50,000 worldwide, this population is understood to be about one-fifth the size of those with wild-type (wtATTR), and have a “high clinical need for effective treatment”, the PBAC said.

However, patisiran had shown clinical benefits in terms of delaying disease progression, reducing neuropathy symptoms, and improving health-related quality of life compared to placebo, based on the primary and secondary outcomes in the APOLLO trial over its 18-month trial period, the committee said (link here).

Branded Onpattro (Alnylam), patisiran is formulated as an IV infusion to be given every three weeks in addition to best supportive care.

Based on the APOLLO data, patisiran is dosed by weight at 0.3 mg per kg of body weight, although for patients weighing 100 kg or more, the recommended dose is fixed at 30 mg.

Patients with a body weight over 66.7 kg will require the maximum quantity of 3 vials per dose (corresponding to approximately 40% of the APOLLO trial population).

According to the PBS application, the requested restriction would be consistent with the TGA indication, hATTR amyloidosis in adult patients with stage 1 or stage 2 polyneuropathy (FAP stage 1 or 2, or PND score I, II, IIIA or IIIB), however the requested restriction would also require the hATTR amyloidosis to be confirmed by genetic testing.

Other proposed criteria include that the patient must be treated by a consultant physician with experience in the management of amyloid disorders and have stage 1 or stage 2 polyneuropathy.