Prothena Corporation plc
NASDAQ: PRTA · HEALTHCARE · BIOTECHNOLOGY
Updated 2026-06-05
Prothena Corporation plc (PRTA) Stock Valuation Analysis
Fair value estimate, historical valuation range, and quality signals for PRTA.
Valued
Valuation reasonably reflects current fundamentals. Limited margin of safety at these levels.
PRTA historical valuation range
Where current P/E sits in PRTA's own 5Y range.
PRTA intrinsic value (DCF)
DCF-based fair value estimate vs current market price.
Standard discounted cash flow models produce unreliable output for unprofitable or near-breakeven companies. Revenue-based multiples such as P/S and EV/Sales, combined with the historical valuation position above, give a more reliable read for this stock.
Intrinsic value calculated using discounted cash flow (DCF) model based on projected free cash flows, discount rate, and terminal growth assumptions. A positive margin of safety indicates the current price is below estimated fair value, providing a cushion against estimation error.
PRTA valuation signals
Quick-read green flags, caution flags, and risks based on current metrics.
P/E Ratio — History
P/S Ratio — History
Current: 7.65x
Is PRTA overvalued in 2026?
Prothena Corporation plc (PRTA) currently trades at $9.43 per share with a market capitalization of $443,432,000.00. Based on our multi-factor framework, the stock trades at a fair valuation with a Smart Value Score of 58/100. This score blends growth quality, financial health, and price attractiveness into a single institutional-grade read.
PRTA currently has no meaningful P/E ratio, which typically signals that the company is unprofitable, near breakeven, or emerging from a loss-making period. With a P/S ratio of 7.7x, the market is valuing the company primarily on its revenue rather than its earnings.
A standard DCF model does not produce reliable output for PRTA under current conditions. For unprofitable or near-breakeven companies, revenue-based multiples such as EV/Sales and historical P/S percentile are more informative than intrinsic value calculations.
Financial quality is a concern. The Piotroski F-Score of 1/9 flags weakening fundamentals that deserve closer scrutiny before the valuation case can be fully trusted.
Bottom line: PRTA trades at a fair valuation on our framework, with a Smart Value Score of 58/100. The valuation is defensible but offers no obvious bargain. Patience or a better entry price may reward disciplined buyers.
Frequently asked questions
Is PRTA overvalued?
PRTA scores 58/100 on our Smart Value Score (Grade C+), a mixed overall profile. A standard DCF is unreliable here given the profitability profile, so valuation leans on revenue-based measures like EV/Sales and the P/S percentile below.
What is PRTA's fair value?
A standard DCF is unreliable for PRTA given its current profitability profile. Revenue-based approaches like EV/Sales or the historical P/S percentile are more informative for this stock.
What P/E ratio does PRTA trade at?
PRTA does not have a meaningful P/E right now, usually a sign of unprofitability or an earnings transition. For unprofitable growth names, price-to-sales is the more useful gauge.
Is PRTA a buy based on valuation?
Our Smart Value rating for PRTA is Hold, from a Smart Value Score of 58/100 that blends growth, quality, and valuation. The profile is balanced and best suited to investors who already have a thesis. This is research to inform your decision, not personalized financial advice.
How does PRTA's valuation compare to its history?
There is not enough historical valuation data yet for a confident percentile read on PRTA.
What is PRTA's Smart Value Score?
PRTA's Smart Value Score is 58/100. It is a proprietary WallStSmart metric blending growth quality, financial health, and valuation into a single 0-100 read, and scores above 75 are rare, signaling strong multi-factor alignment.