Prothena Corporation plc (PRTA) AI Stock Analysis

Prothena Corporation plc is a late-stage clinical biotechnology company based in Dublin, Ireland, focused on discovering and developing therapies for life-threatening diseases. Its pipeline includes Birtamimab, an investigational humanized antibody in Phase III trials for AL amyloidosis, and Prasinezumab, in Phase IIb trials for Parkinson's disease. The company is also evaluating PRX004 for Transthyretin amyloidosis, PRX005 for Alzheimer's disease, and preclinical candidates such as PRX012 and a dual A-Tau vaccine. Prothena collaborates with F. Hoffmann-La Roche Ltd. and Hoffmann-La Roche Inc. on antibodies targeting alpha-synuclein, and partners with Bristol-Myers Squibb on novel antibody therapies.

Prothena's financial results reflect significant year-to-year volatility typical of collaboration milestone revenue. Revenue reached $200.6M in FY2021 before falling to $53.9M in FY2022. It rebounded to $91.4M in FY2023 and $135.2M in FY2024, but declined 92.8% in FY2025 to $9.7M. Operating margin deteriorated from 35.9% in FY2021 to -1905.8% in FY2025, while net income shifted from $67.0M in FY2021 to -$244.1M in FY2025, producing diluted EPS of -$3.98. R&D expenses were $134.9M in FY2025. Over the trailing twelve months ending June 30, 2026, revenue stood at $54.5M, with quarterly revenue falling 77.1% year-over-year and an operating margin of -1850.2%.

As of June 30, 2026, Prothena held $288.2M in cash and short-term investments against total debt of $7.0M, resulting in net cash of $281.2M. The company maintains a current ratio of 25.05 and a debt-to-equity ratio of 0.02, with shareholders' equity of $286.9M and total assets of $302.6M. In FY2025, operating cash flow was -$163.6M and free cash flow was -$163.7M. Capital allocation was modest in FY2025, with capital expenditures of $138,000 and share buybacks of $139,000.

At a last close of $8.35, Prothena had a market capitalization of $428.7M and an enterprise value of $164.4M. Its forward P/E of 10.6x is below the 17.3x median of its US-listed Healthcare peers, while its price-to-sales multiple of 7.9x is higher than the peer median of 4.1x. The stock carries a price-to-book ratio of 1.6x and an EV-to-revenue ratio of 3.0x. Over the past year, PRTA dropped 17.2% compared to a 16.8% gain for the S&P 500 benchmark SPY, and over five years it fell 86.8% versus an 83.0% increase for SPY.

Wall Street coverage includes 2 Strong Buy, 2 Buy, 2 Hold, and 1 Sell ratings. The mean price target of $21.40 represents a 156.3% premium over the last close of $8.35. For the fiscal year ending December 31, 2026, consensus estimates project revenue of $82.7M and EPS of $0.64, representing 116.1% EPS growth. However, for the next fiscal year, analysts estimate revenue of $21.0M and EPS of -$1.31. Prothena beat EPS estimates in 2 of the last 4 quarters, and its next earnings date is November 5, 2026.

This page is an AI-written research summary of Prothena Corporation plc (PRTA). The text was generated on October 30, 2026 from Quotelinks data as of October 16, 2026 (company profile, annual results, latest balance sheet, valuation, price performance and analyst estimates). An automatic check rejects any draft that contains a figure not found in that data. It is not investment advice; verify figures on the linked tabs before making decisions.

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