Prothena Corporation plc presented the first peer‑reviewed Phase 2 data for its ATTR‑cardiomyopathy antibody, coramitug, during a late‑breaking session at the American Heart Association Scientific Sessions on November 10, 2025. The data were simultaneously published in the journal Circulation, providing the scientific community with the earliest evidence of coramitug’s efficacy and safety profile.
The Phase 2 study demonstrated a depleter mechanism that removes deposited amyloid while sparing native transthyretin, a feature that distinguishes coramitug from existing stabilizers and gene‑silencing therapies. The results confirm that the antibody can clear both tissue‑bound and circulating non‑native TTR, addressing the underlying pathology of transthyretin amyloid cardiomyopathy (ATTR‑CM) and offering a potential disease‑modifying treatment option.
Prothena’s partnership with Novo Nordisk, which acquired worldwide rights to the ATTR pipeline in July 2021, is a key driver of the program’s commercial prospects. The company is eligible for up to $1.2 billion in milestone payments, of which $100 million has already been earned. Novo Nordisk has launched the Phase 3 CLEOPATTRA trial, positioning coramitug for a potential regulatory submission once the trial reaches its primary endpoints.
The ATTR amyloidosis market is estimated at $3‑$5 billion, with competitors such as Pfizer’s tafamidis and emerging gene‑therapy candidates. Coramitug’s unique mechanism and the partnership with a global cardiology leader give Prothena a differentiated foothold in this high‑need, high‑value space. The Phase 2 data strengthen the company’s pipeline narrative and enhance its attractiveness to investors focused on late‑stage, partnered assets.
Management emphasized the significance of the milestone, stating, “We are pleased with the advancement of our late‑stage partnered clinical programs.” The data, coupled with the ongoing Phase 3 trial, reinforce Prothena’s strategy of leveraging partner expertise to accelerate development while preserving upside potential through milestone payments and future royalties.
Beyond ATTR, Prothena continues to advance other programs, including Alzheimer’s disease candidates PRX012 and BMS‑986446 and a Parkinson’s disease antibody in collaboration with Roche. The company’s Q3 2025 earnings—net loss of $36.5 million and revenue of $2.42 million—missed analyst revenue estimates but met EPS expectations, underscoring the company’s focus on pipeline progress over short‑term revenue growth.
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