Prothena Corporation plc (PRTA)

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The chart shows the growth of an initial investment of $10,000 in Prothena Corporation plc, comparing it to the performance of the S&P 500 index or another benchmark. All prices have been adjusted for splits and dividends.

Prothena Corporation plc (PRTA) has returned 1.78% so far this year and -21.45% over the past 12 months. Over the last ten years, PRTA has returned -13.83% per year, falling short of the S&P 500 Index benchmark, which averaged 12.16% annually.

Based on dividend-adjusted daily data since Dec 21, 2012, PRTA's average daily return is +0.12%, while the average monthly return is +2.55%. At this rate, your investment would double in approximately 2.3 years.

Historically, 52% of months were positive and 48% were negative. The best month was Sep 2022 with a return of +119.9%, while the worst month was Apr 2018 at -67.3%. The longest winning streak lasted 10 consecutive months, and the longest losing streak was 4 months.

On a daily basis, PRTA closed higher 50% of trading days. The best single day was Sep 28, 2022 with a return of +87.5%, while the worst single day was Apr 23, 2018 at -68.8%.

Prothena Corporation plc has an annualized alpha of 13.85%, beta of 1.38, and R² of 0.10 versus S&P 500 Index. Calculated based on daily prices since December 24, 2012.

• This stock participated in 147.12% of S&P 500 Index downside but only 101.35% of its upside — more exposed to losses than it benefited from rallies.
• R² of 0.10 means this stock moves largely independently of S&P 500 Index — capture ratios reflect limited market correlation rather than active downside protection. Consider using a more representative benchmark.

PRTA ranks 26 for risk / return — below 26% of stocks on our site. The returns aren't fully compensating for the risk involved. This isn't necessarily a dealbreaker, but factor it into your decision — especially if you're risk-averse.

The table below present risk-adjusted performance metrics for Prothena Corporation plc (PRTA) and compare them to a chosen benchmark (S&P 500 Index).

The Drawdowns chart displays portfolio losses from any high point along the way. Drawdowns are calculated considering price movements and all distributions paid, if any.

The table below displays the maximum drawdowns of the Prothena Corporation plc. A maximum drawdown is a measure of risk, indicating the largest reduction in portfolio value due to a series of losing trades.

The maximum drawdown for the Prothena Corporation plc was 94.19%, occurring on May 27, 2025. The portfolio has not yet recovered.

The current Prothena Corporation plc drawdown is 87.68%.

The chart below shows the rolling one-month volatility.

The chart below illustrates the trends in the financial health of Prothena Corporation plc over time, highlighting three key metrics: Total Revenue, Earnings Before Interest and Taxes (EBIT), and Net Income.

The Valuation section provides an overview of how Prothena Corporation plc is priced in the market compared to other companies in the Biotechnology industry. It includes key financial ratios that help investors assess whether the stock is undervalued or overvalued.