Prothena (PRTA) has wrapped up FY 2025 with Q4 revenue of about US$0.02 million and a basic EPS loss of US$0.40, alongside trailing 12 month revenue of US$9.68 million and a full year basic EPS loss of US$4.53. Over recent quarters the company has seen quarterly revenue move from US$2.12 million in Q4 2024 to US$4.42 million in Q2 2025 and then US$2.42 million in Q3 2025, while quarterly basic EPS shifted from a loss of US$1.08 in Q4 2024 to a loss of US$2.34 in Q2 2025 and US$0.68 in Q3 2025. This sets the scene for a results season where investors focus squarely on how quickly those losses might narrow. With the stock trading at US$10.53, the latest numbers put the spotlight on how efficiently Prothena is converting a relatively modest revenue base into future margin potential.

See our full analysis for Prothena.

With the headline figures on the table, the next step is to see how these results line up with the widely followed growth and profitability narratives around Prothena and where those stories might need updating.

Losses stay heavy at US$244 million over 12 months

• Over the trailing 12 months to Q4 2025, Prothena recorded a net loss of US$244.1 million on US$9.7 million of revenue, with basic EPS at a loss of US$4.53.
• Consensus narrative points to future earnings potential, but these figures highlight the gap to that view:
  • Analysts expect revenue to grow about 39.2% per year and earnings to grow around 79.7% per year, yet losses have widened at roughly 33.4% per year over the past five years.
  • Birtamimab and Alzheimer’s candidates are seen as large market opportunities, but the current loss profile shows that any long term earnings growth case still rests on pipeline progress that has not yet translated into revenue.

Quarterly swings in revenue and EPS across FY 2025

• Across FY 2025, quarterly revenue moved between US$0.02 million and US$4.4 million, while quarterly net losses ranged from US$21.6 million to US$125.8 million and basic EPS losses ran from US$0.40 to US$2.34.
• Bulls lean on the partnered pipeline to argue those swings are the price of building future revenue streams:
  • Four partnered neurology and cardiology programs, including two Phase III assets and a Phase II Alzheimer’s program, are expected by bulls to feed into milestone receipts that can support margins after a current loss of US$244.1 million.
  • Guidance for another net loss of US$67 million to US$72 million in 2026 is seen by optimistic investors as a bridge to potential milestones of up to roughly US$3.0 billion, but the present volatility in quarterly revenue underlines how dependent that view is on successful trial outcomes.

Consistent swings in quarterly losses are exactly what bullish investors point to as the cost of building late stage programs that could change the earnings picture if they clear key trial readouts. 🐂 Prothena Bull Case

DCF fair value of US$126.83 vs US$10.53 share price

• The stock trades at US$10.53 with a P/B of 2.0x, compared with peer and industry averages of 2.3x and 2.5x, and a stated DCF fair value of US$126.83 that is very high relative to the current price.
• Bears question whether current losses justify any gap between price and estimated fair value:
  • Analysts’ consensus price target of US$21.00 implies a lift from today’s US$10.53 level, yet the trailing 12 month net loss of US$244.1 million and multi year loss growth of about 33.4% per year show that profitability has not yet emerged.
  • Concerns around high development costs, potential delays in programs like Birtamimab and intense competition in AL amyloidosis and neurodegeneration all sit alongside that loss profile, which makes the implied upside sensitive to how quickly earnings can move away from the current loss making base.

Cautious investors often focus on how far Prothena still needs to move from a US$244.1 million annual loss to any earnings that might support higher valuations. 🐻 Prothena Bear Case

Next Steps

To see how these results tie into long-term growth, risks, and valuation, check out the full range of community narratives for Prothena on Simply Wall St. Add the company to your watchlist or portfolio so you'll be alerted when the story evolves.

If this all feels finely balanced between risk and potential reward, that is exactly why the data matters. Act quickly, review the full picture, and weigh up whether the optimism around its 2 key rewards lines up with your own expectations through the 2 key rewards.

See What Else Is Out There

Prothena is still carrying heavy annual losses of US$244.1 million on just US$9.7 million of revenue, with quarterly results swinging sharply.

If that level of uncertainty feels uncomfortable, shift your focus toward companies with steadier profiles by checking out the 72 resilient stocks with low risk scores today to compare potential ideas.

This article by Simply Wall St is general in nature. We provide commentary based on historical data and analyst forecasts only using an unbiased methodology and our articles are not intended to be financial advice. It does not constitute a recommendation to buy or sell any stock, and does not take account of your objectives, or your financial situation. We aim to bring you long-term focused analysis driven by fundamental data. Note that our analysis may not factor in the latest price-sensitive company announcements or qualitative material. Simply Wall St has no position in any stocks mentioned.