Alexion Pharmaceuticals, Inc. and BridgeBio Pharma, Inc.'s subsidiary Eidos Therapeutics, Inc. announced an agreement that grants Alexion an exclusive license to develop and commercialize AG10 in Japan. AG10 is a small molecule designed to treat the root cause of transthyretin amyloidosis (ATTR) – destabilized and misfolded transthyretin (TTR) protein – by binding and stabilizing TTR in the blood. Eidos is currently evaluating AG10 in a Phase 3 study in the U.S. and Europe for ATTR cardiomyopathy (ATTR-CM) – a progressive, fatal disease caused by the accumulation of misfolded TTR amyloid in the heart – and plans to begin a Phase 3 study in ATTR polyneuropathy (ATTR-PN) – a progressive, fatal disease caused by the accumulation of misfolded TTR amyloid in the peripheral nervous system.

Under the terms of the agreement, Alexion will acquire an exclusive license for the clinical development and commercialization of AG10 in Japan. Eidos will receive an upfront payment of $25 million and an equity investment of $25 million at a premium to the market price upon deal execution, with the potential for additional Japanese-based milestone- and royalty-dependent payments. AG10 is an investigational, orally-administered small molecule designed to potently stabilize tetrameric transthyretin, or TTR, thereby halting at its outset the series of molecular events that give rise to TTR amyloidosis, or ATTR.

In a Phase 2 clinical trial in patients with symptomatic ATTR-CM, AG10 was generally well tolerated, demonstrated greater than 90% average TTR stabilization at Day 28, and increased serum TTR concentrations, a prognostic indicator of survival in a retrospective study of ATTR-CM patients, in a dose-dependent manner. AG10 was designed to mimic a naturally-occurring variant of the TTR gene (T119M) that is considered a rescue mutation because co-inheritance has been shown to prevent or ameliorate ATTR in individuals also inheriting a pathogenic, or disease-causing, mutation in the TTR gene.