What Prothena Corporation plc told the SEC could break it.

Prothena's revenue is almost entirely dependent on its BMS collaboration: collaboration revenue from BMS was $9.6 million in 2025 (vs. $135.1M in 2024 and $91.3M in 2023, a 93% decline), and its future revenue hinges on BMS exercising options and achieving development/regulatory/sales milestones (up to $617.5M and $562.5M across programs) and paying tiered royalties; a slowdown, deprioritization or termination by BMS would sharply reduce Prothena's revenue.

“Collaboration revenue from BMS was $ 9.6 million, $ 135.1 million and $ 91.3 million for the year ended December 31, 2025 , 2024 and 2023, respectively.”

Prothena anticipates continued losses and may never reach profitability: it incurred a $244.1 million net loss in 2025 (after $30.1M of restructuring costs) and has a $1.3 billion accumulated deficit, so it depends on its cash, additional (potentially dilutive) capital, and the timing/receipt of milestone payments and royalties under collaborations — including up to $1.23 billion of contingent consideration from Novo Nordisk's purchase of Neotope Neuroscience — to fund operations and bring drug candidates to market.

“We incurred net lo sses of $244.1 million $122.3 million and $147.0 million for the years ended December 31, 2025, 2024, and 2023, respectively. As of December 31, 2025, we had an accumulated deficit of $1.3 billion.”

Prothena's prasinezumab (α-synuclein, Parkinson's) program depends on its License Agreement with Roche: outside the United States Prothena is solely dependent on Roche's efforts and commitments to further develop and, if approved, commercialize prasinezumab, and even in the U.S. its success depends on the Roche collaboration; if Roche terminates or breaches the agreement or its efforts are unsuccessful, Prothena's ability to generate prasinezumab revenue would be substantially harmed and it would have to build its own commercialization capability or find a new partner.

“Outside of the United States, we are solely dependent on the efforts and commitments of Roche, either directly or through third parties, to further develop and, if prasinezumab is approved by applicable regulatory authorities, commercialize prasinezumab.”

Prothena has no manufacturing capacity and depends entirely on third-party manufacturers to supply nonclinical and clinical trial supplies of all its drug candidates and any future commercial product, and it relies on limited or sole-sourced raw materials; any supply interruption, quality failure or inability to qualify an alternative source in a reasonable time could materially harm its ability to manufacture and delay development and commercialization of its drug candidates.

“We have no manufacturing capacity and depend on third-party manufacturers to supply us with nonclinical and clinical trial supplies of all of our drug candidates, and we will depend on third-party manufacturers to supply us with any drug product for commercial sale if we obtain marketing approval from the FDA, the EMA, or any other comparable regulatory authority for any of our drug candidates.”