Update shared on 04 Dec 2025
Fair value Increased 11%Analysts have lifted their fair value estimate for Prothena by about $2 per share, citing stronger long term revenue growth expectations from its partnered pipeline, lucrative royalty and milestone economics, and a robust catalyst calendar that they believe offers substantial upside potential.
Analyst Commentary
Recent adjustments to Prothena's valuation reflect a growing conviction that the company’s partnered programs and associated economics could materially enhance long term growth, though execution and timing risks remain key variables for investors.
Bullish Takeaways
- Bullish analysts highlight that the significant increase in price target reflects greater confidence in the commercial potential of the partnered pipeline and its ability to support a premium valuation multiple.
- The anticipated stream of net sales royalties and milestone payments is viewed as an attractive, relatively capital efficient revenue source that can scale meaningfully as partnered assets progress and launch.
- A dense, catalyst rich 12 month period is expected to provide multiple opportunities for value inflection, with positive readouts or partnership developments potentially justifying further upside to current targets.
- Stronger long term revenue growth assumptions, based on expanded indications and higher probability of success for key programs, are seen as improving visibility into durable top line expansion.
Bearish Takeaways
- Bearish analysts caution that a sizable portion of the valuation now embeds optimistic expectations for future milestones and royalties, which could prove difficult to achieve if clinical timelines slip or data underperforms.
- Reliance on partners for late stage development and commercialization introduces execution risk outside of Prothena’s direct control, potentially impacting the timing and magnitude of expected cash flows.
- The catalyst heavy outlook increases event risk in both directions, and any negative or inconclusive data could lead to a rapid reassessment of growth assumptions and target price support.
- Some investors may question whether the recent target increase overshoots near term fundamentals, leaving limited margin of safety if market sentiment toward biotech or partnered models weakens.
What's in the News
- Presented new preclinical data on CYTOPE, a novel drug delivery modality that enables cytosolic delivery of macromolecules to the brain and periphery, at Neuroscience 2025. The data highlighted its potential to target previously undruggable intracellular disease pathways (Company announcement, Society for Neuroscience 2025).
- Reported preclinical ALS data showing that systemically administered TDP 43 CYTOPE reached the brain, localized to intracellular pTDP 43 pathology, and significantly reduced pTDP 43 aggregates and associated RNA dysregulation in mouse models and human neuronal systems (Company announcement).
- Announced publication of Phase 2 data for coramitug (formerly PRX004), a potential first in class amyloid depleter antibody for ATTR cardiomyopathy, in the American Heart Association journal Circulation. The results were also featured in a late breaking session at AHA Scientific Sessions 2025 (AHA Scientific Sessions, Circulation).
- Highlighted advancement of coramitug into the Phase 3 CLEOPATTRA trial led by Novo Nordisk. Under the collaboration, Prothena is eligible for up to $1.2 billion in milestones, including additional clinical milestone payments tied to trial enrollment targets (Company announcement, Novo Nordisk collaboration).
- Scheduled a Special or Extraordinary Shareholders Meeting for November 19, 2025 in Dublin to seek approval for a reduction of company capital to create distributable reserves and to address any additional business that may come before the meeting (Company notice of meeting).
Valuation Changes
- Fair Value Estimate has risen modestly from $18.33 to $20.33 per share, reflecting higher long term revenue expectations from the partnered pipeline.
- Discount Rate has increased slightly from 7.39% to 7.44%, indicating a marginally higher assumed risk profile in the valuation model.
- Revenue Growth has been raised significantly from 74.7% to 90.9%, underscoring more optimistic assumptions for long term top line expansion.
- Net Profit Margin has edged down from 17.0% to 16.0%, suggesting slightly more conservative expectations for long term profitability.
- Future P/E multiple has been reduced from 112.7x to 101.7x, implying a somewhat lower valuation multiple despite the stronger growth outlook.
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