PRTA
Prothena Corporation plc Healthcare - Biotechnology Investor Relations →
Prothena Corporation plc (PRTA) closed at $8.75 as of 2026-03-20, trading 70.4% below its 200-week moving average of $29.52. This places PRTA in the extreme value zone. The stock is currently moving closer to the line, down from -68.9% last week. The 14-week RSI sits at 37, indicating neutral momentum.
Trading volume is running at 1.6x of its 14-week average, which is in the normal range. The balance between buying and selling volume (0.71 ratio) is neutral — neither side is clearly dominating.
Over the past 643 weeks of data, PRTA has crossed below its 200-week moving average 7 times. On average, these episodes lasted 42 weeks. Historically, investors who bought PRTA at the start of these episodes saw an average one-year return of +91.3%.
With a market cap of $471 million, PRTA is a small-cap stock. Free cash flow yield is currently negative, meaning the company is burning cash. Return on equity stands at -63.6%. The stock trades at 1.7x book value.
Share count has increased 3.3% over three years, indicating dilution.
Over the past 12.4 years, a hypothetical investment of $100 in PRTA would have grown to $31, compared to $444 for the S&P 500. PRTA has returned -9.0% annualized vs 12.7% for the index, underperforming the broader market over this period.
Free cash flow has been declining. A deteriorating cash flow trend warrants extra scrutiny — the stock may be cheap for a reason.
Business Health
Annual financials — how the underlying business has performed over the past several years.
Cash Flow Free cash flow & net income ($M)
Revenue Annual revenue ($M) — business growth proxy
Total Debt Balance sheet debt ($M)
ROIC Return on invested capital (%)
FCF Yield Free cash flow / market cap (%) — Yartseva signal
Gross Margin Pricing power & competitive moat (%)
Shares Outstanding Buybacks vs dilution (millions)
Growth of $100: PRTA vs S&P 500
Monthly data normalized to $100 at start. Vertical dashed lines mark 200-week MA touches.
What Happens After PRTA Crosses Below the Line?
Across 7 historical episodes, buying PRTA when it crossed below its 200-week moving average produced an average return of +74.1% after 12 months (median +58.0%), compared to +12.9% for the S&P 500 over the same periods. 57% of those episodes were profitable after one year. After 24 months, the average return was +49.9% vs +26.4% for the index.
Each line shows $100 invested at the moment PRTA crossed below its 200-week MA. Bold blue = stock average. Gray dashed = S&P 500 average over same periods.
Historical Touches
PRTA has crossed below its 200-week MA 7 times with an average 1-year return of +91.3% after recovery.
| Crossed Below | Recovered | Weeks | Max Depth | 1-Year Return | Return Since Touch |
|---|---|---|---|---|---|
| Jul 2014 | Aug 2014 | 3 | 8.7% | +223.9% | -52.5% |
| Oct 2014 | Oct 2014 | 1 | 4.8% | +143.1% | -52.4% |
| Dec 2014 | Dec 2014 | 1 | 6.8% | +267.1% | -51.8% |
| Dec 2017 | Feb 2021 | 166 | 81.5% | -72.3% | -78.7% |
| Mar 2021 | Mar 2021 | 1 | 0.5% | +43.2% | -59.1% |
| Oct 2023 | Dec 2023 | 7 | 10.4% | -57.2% | -75.5% |
| Dec 2023 | Ongoing | 117+ | 87.8% | Ongoing | -75.9% |
| Average | 42 | — | +91.3% | — |
Frequently Asked Questions
Is PRTA below its 200-week moving average?
Yes. As of 2026-03-20, Prothena Corporation plc (PRTA) is trading 70.4% below its 200-week moving average of $29.52. The current price is $8.75.
What is PRTA's 200-week moving average price?
Prothena Corporation plc's 200-week moving average is $29.52 as of 2026-03-20. This is the average weekly closing price over roughly the last 4 years, and it acts as a long-term trend line. When a stock drops below this level, it can signal that the price has fallen far enough from the long-term trend to attract value-oriented investors.
What happens when PRTA drops below its 200-week moving average?
PRTA has crossed below its 200-week moving average 7 times in our data. On average, buying at that moment produced a one-year return of +91.3%. These dips have historically been decent entry points. These episodes lasted 42 weeks on average.
Is PRTA a good value right now?
Here's what our data says about PRTA as of 2026-03-20: The stock is below its 200-week moving average, which is the starting point for our analysis. The 14-week RSI is 37. Free cash flow is currently negative. Return on equity is -63.6%. Price-to-book is 1.7x. This is not a buy or sell recommendation — always do your own research.
How does PRTA compare to the S&P 500?
Over the past 12.4 years, $100 invested in PRTA would have grown to $31, compared to $444 for the S&P 500. That's -9.0% annualized vs 12.7% for the index. PRTA has underperformed the broader market over this period.
Not financial advice. This is an educational tool. Past performance does not guarantee future results. Do your own research before making investment decisions.
Data as of week of 2026-03-20