Patisiran Benefits ATTR Amyloidosis With Cardiomyopathy: APOLLO-B

September 08, 2022

The RNA interference (RNAi) therapeutic, patisiran (Onpattro;  Alnylam), showed a statistically significant and clinically meaningful benefit on functional capacity, as measured by the 6-minute walk test (6-MWT) compared with placebo, in the treatment of transthyretin-mediated amyloidosis with cardiomyopathy, in the APOLLO-B trial.

The study also met its first secondary endpoint, demonstrating a statistically significant and clinically meaningful benefit on health status and quality of life.

These positive results were announced today at the 18th International Symposium on Amyloidosis, which is being held in Heidelberg, Germany.

The company had announced positive top-line results from the trial a few weeks ago. But, today was the first formal presentation of the results.

Transthyretin-mediated (ATTR) amyloidosis is a rare, rapidly progressive, debilitating disease caused by misfolded transthyretin (TTR) proteins which accumulate as amyloid fibrils in multiple tissues including the nerves, heart, and gastrointestinal tract.

There are two different types of ATTR amyloidosis: hereditary ATTR (hATTR) amyloidosis, caused by a TTR gene variant, and wild-type ATTR (wtATTR) amyloidosis, which occurs without a TTR gene variant. hATTR amyloidosis affects approximately 50,000 people worldwide, whereas wtATTR amyloidosis is estimated to affect 200,000-300,000 people worldwide.

Patisiran is an intravenously administered RNAi therapeutic that is approved in the United States and Canada for the treatment of the polyneuropathy of hATTR amyloidosis in adults. It is also approved in the European Union, Switzerland, Brazil, and Japan for a similar indication. It is designed to target and silence TTR messenger RNA, thereby reducing the production of TTR protein before it is made. Reducing the pathogenic protein leads to a reduction in amyloid deposits in tissues.

"The results of the APOLLO-B phase 3 study are impressive, as I believe they underscore the potential for patisiran to provide a benefit on functional capacity and quality of life in patients living with ATTR amyloidosis with cardiomyopathy. Furthermore, these results were seen after only 12 months of treatment," said Mathew Maurer, MD, Arnold and Arlene Goldstein Professor of Cardiology at Columbia University Irving Medical Center, in an Alnylam press release.

"The cardiac manifestations associated with ATTR amyloidosis can have a devastating impact on patients' lives and current treatment options are limited. With the rapidly progressive nature of the disease, there is a significant need for treatments like patisiran, which has the potential to be a new option for patients and physicians to treat the cardiomyopathy of ATTR amyloidosis," Maurer added

APOLLO-B is a phase 3, randomized, double-blind study evaluating the effects of patisiran on functional capacity and quality of life in patients with ATTR amyloidosis with cardiomyopathy. The study enrolled 360 adult patients with ATTR amyloidosis (hereditary or wild-type) with cardiomyopathy who were randomly assigned 1:1 to receive 0.3 mg/kg of patisiran or placebo intravenously administered every 3 weeks over a 12-month treatment period. After 12 months, all patients will receive patisiran in an open-label extension.

Results at 12 months, reported by Alnylam, found that the primary endpoint, the 6-MWT, showed a median change from baseline of -8.15 m for the patisiran group and -21.34 m for the placebo group, a significant difference favoring patisiran.

The first secondary endpoint was health status and quality of life, as measured by the Kansas City Cardiomyopathy Questionnaire Overall Summary score. This showed a mean change from baseline of +0.300 for the patisiran group and -3.408 for the placebo group, a significant difference favoring patisiran.

Secondary composite outcome endpoints did not achieve statistical significance.

A nonsignificant result (win ratio, 1.27; P = .0574) was found on the secondary composite endpoint of all-cause mortality, frequency of cardiovascular events, and change from baseline in 6-MWT over 12 months compared with placebo.

The final two composite endpoints were not powered for statistical significance, given the sample size and short duration of the study — all-cause mortality and frequency of all-cause hospitalizations and urgent heart failure visits in patients not on tafamidis at baseline (hazard ratio [HR], 0.997) and in the overall study population (HR, 0.883).

Patisiran achieved a rapid and sustained reduction in serum TTR levels, with a mean percent reduction from baseline in serum TTR reduction of 87% at month 12.

A beneficial effect on the exploratory endpoint, NT-proBNP, a measure of cardiac stress, was observed in the patisiran arm, with a 20% reduction in the adjusted geometric mean fold change from baseline compared with placebo.

Patisiran also demonstrated an encouraging safety and tolerability profile, including no cardiac safety concerns relative to placebo, during the 12-month treatment period, Alnylam reports.

The majority of adverse events were mild or moderate in severity. Treatment emergent adverse events in the patisiran group included infusion-related reactions, arthralgia, and muscle spasms.

In the safety analysis, there were five deaths (2.8%) observed in patisiran-treated patients and eight deaths (4.5%) observed in the placebo group.

Pushkal Garg, MD, chief medical officer at Alnylam said: "We believe these data validate the therapeutic hypothesis that TTR silencing by an RNAi therapeutic may be an effective approach to treating cardiomyopathy of both wild-type and hereditary ATTR amyloidosis."

Alnylam plans to file a supplemental new drug application for patisiran as a potential treatment for ATTR amyloidosis with cardiomyopathy in the United States in late 2022.

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