FDA Grants Fast Track to Coramitug for ATTR-CM, Supporting Amyloid-Clearing Phase 3 Trial

The US Food and Drug Administration (FDA) has granted Fast Track Designation to coramitug (PRX004) for the treatment of transthyretin amyloid cardiomyopathy (ATTR-CM).¹

Announced on April 27, 2026, by Prothena Corporation and its licensing partner Novo Nordisk, this designation covers the investigational humanized monoclonal antibody targeting misfolded transthyretin (TTR) currently under evaluation in the Phase 3 CLEOPATTRA trial. Fast Track Designation is intended by the FDA to facilitate development and expedite review of therapies addressing serious conditions with unmet medical need.¹

The clinical relevance of this designation lies in the therapeutic gap coramitug aims to fill. Unlike approved TTR stabilizers and RNA-targeting agents, which slow further amyloid deposition or reduce TTR production, coramitug is designed to actively clear existing amyloid deposits from cardiac tissue, a mechanism not currently represented in the approved treatment landscape for ATTR-CM.¹

"We are pleased that the FDA has granted Fast Track Designation for coramitug, a recognition that reflects both the seriousness of ATTR-CM and the significant unmet need that remains for people living with this life-threatening disease, despite standard of care," Michelle Lim-Watson, MPH, Associate Portfolio Vice President, Cardiovascular Disease and Rare Diseases, U.S. R&D, Novo Nordisk, said in a statement.¹

Trial and Regulatory Overview

Coramitug is being evaluated in the ongoing Phase 3 CLEOPATTRA trial, enrolling approximately 1,280 participants with ATTR-CM. Primary completion is expected in 2029. The trial is sponsored by Novo Nordisk, which acquired full worldwide rights to Prothena's ATTR amyloidosis pipeline in July 2021.²

Supporting the Phase 3 program, Phase 2 data have demonstrated that coramitug 60 mg/kg significantly reduced and improved N-terminal pro-B-type natriuretic peptide (NT-proBNP) from baseline in patients with ATTR-CM. Notably, more than 80% of participants in that trial were already receiving standard-of-care therapy at baseline, which is a clinically important context suggesting potential additive benefit. Compared with placebo, coramitug was also associated with improvements in multiple echocardiographic parameters of cardiac function and was reported to be well-tolerated.³

Clinical Context and Unmet Need

ATTR-CM is a progressive, life-threatening cardiomyopathy caused by the deposition of misfolded TTR amyloid fibrils in the myocardium. The disease is increasingly recognized as underdiagnosed and associated with significant morbidity and mortality, including heart failure and arrhythmia. Approved therapies, including the TTR stabilizer tafamidis and the RNA silencers patisiran and vutrisiran, reduce the rate of disease progression but do not eliminate established amyloid deposits. This mechanistic limitation leaves a clinically meaningful gap for patients who present with substantial existing cardiac amyloid burden.

Mechanism of Action and Drug Background

Coramitug is a humanized monoclonal antibody engineered to bind specifically to misfolded, non-native forms of TTR - including both deposited amyloid and circulating non-native TTR monomers - without disrupting the normal, functional TTR tetramer. Its proposed mechanism involves antibody-mediated phagocytosis to promote amyloid clearance and prevent further organ deposition. This depleter approach is mechanistically distinct from existing approved agents and, according to the developers, may hold potential both as monotherapy and in combination with stabilizers or production-reducing agents.^1,2,3

Interpretive Framing

The FDA Fast Track Designation reflects regulatory acknowledgment of ATTR-CM's severity and the incomplete efficacy of current treatments; however, it does not constitute a finding of safety or efficacy for coramitug. Phase 2 findings, while encouraging, were generated in a relatively small population, and the magnitude and durability of NT-proBNP reduction and echocardiographic improvement require confirmation in the adequately powered Phase 3 setting.

Limitations and Next Steps

The CLEOPATTRA trial's expected primary completion of 2029 means definitive efficacy and safety data remain several years away. The Phase 2 dataset, though supportive, has not been independently replicated, and long-term tolerability data in a broader ATTR-CM population are not yet available. Whether amyloid clearance translates into hard cardiovascular outcomes, such as reduction in all-cause mortality or cardiovascular hospitalization, remains the central unanswered clinical question.^2,3

References

1. Prothena. Prothena Announces Novo Nordisk Obtains Fast Track Designation from the US FDA for Coramitug (PRX004) in ATTR Amyloidosis with Cardiomyopathy. April 27, 2026. Accessed April 28, 2026. https://ir.prothena.com/investors/press-releases/news-details/2026/Prothena-Announces-Novo-Nordisk-Obtains-Fast-Track-Designation-from-the-U-S--FDA-for-Coramitug-PRX004-in-ATTR-Amyloidosis-with-Cardiomyopathy/default.aspx#:~:text=%E2%80%9CWe%20are%20pleased%20that%20the,Lim%2DWatson%2C%20Associate%20Portfolio%20Vice
2. Novo Nordisk A/S. CLEOPATTRA: A Research Study to Look at the Effects of Treatment With a Medicine Called Coramitug (NNC6019-0001) in People With Heart Failure Due to Transthyretin Amyloid (ATTR) Amyloidosis (CLEOPATTRA). ClinicalTrials.gov Identifier: NCT07207811. Updated April 27, 2026. Accessed April 28, 2026. https://clinicaltrials.gov/study/NCT07207811
3. Fontana M, García-Pavía P, Grogan M, et al. Coramitug, a humanized monoclonal antibody for the treatment of transthyretin amyloid cardiomyopathy: A phase 2, randomized, Multicenter, double-blind, placebo-controlled trial. Circulation. 2026;153(4):214-225. doi:10.1161/circulationaha.125.077304