PRTA
Prothena Corporation plc Healthcare - Biotechnology Investor Relations →
Prothena Corporation plc (PRTA) closed at $8.91 as of 2026-02-02, trading 70.5% below its 200-week moving average of $30.16. This places PRTA in the extreme value zone. The stock moved further from the line this week, up from -70.9% last week. The 14-week RSI sits at 36, indicating neutral momentum.
Over the past 637 weeks of data, PRTA has crossed below its 200-week moving average 7 times. On average, these episodes lasted 41 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 $480 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 -67.6%. The stock trades at 1.6x book value.
Share count has increased 15.4% over three years, indicating dilution.
Over the past 12.3 years, a hypothetical investment of $100 in PRTA would have grown to $32, compared to $471 for the S&P 500. PRTA has returned -8.9% annualized vs 13.4% for the index, underperforming the broader market over this period.
Free cash flow has been declining at a -100% compound annual rate. A deteriorating cash flow trend warrants extra scrutiny — the stock may be cheap for a reason.
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% | -51.7% |
| Oct 2014 | Oct 2014 | 1 | 4.8% | +143.1% | -51.5% |
| Dec 2014 | Dec 2014 | 1 | 6.8% | +267.1% | -50.9% |
| Dec 2017 | Feb 2021 | 166 | 81.5% | -72.3% | -78.3% |
| Mar 2021 | Mar 2021 | 1 | 0.5% | +43.2% | -58.3% |
| Oct 2023 | Dec 2023 | 7 | 10.4% | -57.2% | -75.1% |
| Dec 2023 | Ongoing | 111+ | 87.8% | Ongoing | -75.5% |
| Average | 41 | — | +91.3% | — |
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 Friday close, 2026-02-02