Prothena Corporation plc
Prothena Corporation plc ( Prothena or the Company ) is a late-stage clinical biotechnology company with expertise in protein dysregulation with the potential to change the course of devastating neurodegenerative and rare peripheral amyloid diseases. Fueled by its deep scientific expertise built over decades of research, the Company is advancing a pipeline of therapeutic candidates for a number…
$8.35
-$0.15 (-1.76%)
EOD Oct 16, 2026
The business is unprofitable at the operating level (-2216.44% margin). The thesis depends entirely on whether and when it reaches sustainable profitability.
Revenue declined 92.8% YoY. Margins deteriorated 2102.1pp alongside, both lines moving the wrong way.
ROIC dropped from -22.80% to -43.11%, capital efficiency is deteriorating. Operating margin contracted 2102.1pp YoY, cost discipline may be slipping.
Price History
Valuation & Multiples
Based on TTM earnings · Diluted shares
Profitability & Returns
Revenue (TTM)
$55M
▼ -92.8% YoY
Net Income (TTM)
-$44M
▼ -99.6% YoY
Op. Margin
-101.80%
▼ -2102.1pp YoY
ROIC
-14.53%
▼ -20.3pp YoY
Cash Flow & Balance Sheet
FCF
N/A
Op. Cash Flow (TTM)
-$60M
▼ -9.0% YoY
Net Debt
-$281M
Net Cash Position
Cash & Equiv.
$288M
5Y CAGR: +62.6%
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SourceComputed from the 10-Q filed 30 Jul 2026, covering the period ending 30 Jun 2026, as reported to the SEC. Data last refreshed 19 Sept 2026. How this is calculated.
Price from market data, last close as of 16 Oct 2026. Fiscal year ends Dec. Sector medians are approximate S&P 500 benchmarks and update periodically.
Is Prothena Corporation (PRTA) overvalued?
Prothena Corporation (PRTA)'s valuation is best read against its own history, its peers, and the growth its price implies. A high multiple is not the same as overvalued: fast-growing, high-quality businesses can deserve a premium. See the general approach in how to tell if a stock is overvalued.
On quality, Prothena Corporation scores 25/100 on Intrinsiqq's quality scorecard (a lower-quality business on these measures), weighing growth, margins, returns on capital, share count, and balance-sheet strength. All figures are computed from SEC filings; read the full methodology, or see how the market compares in our US profitability statistics. This is analysis, not investment advice.
Frequently asked
Is Prothena Corporation a high-quality business?+
Prothena Corporation scores 25 out of 100 on Intrinsiqq's quality score, a weighted blend of 5 metrics each scored 0 to 100, which makes it a lower-quality business on these measures. Recent fundamentals include a -101.8% operating margin and a -14.5% return on invested capital. The score weighs revenue and free-cash-flow growth, operating margins, return on invested capital, share-count change, and balance-sheet strength, all computed from SEC filings, not opinion. Because valuation only means something relative to quality, the full metric-by-metric breakdown is on the quality scorecard.
Is Prothena Corporation a good stock to buy right now?+
That depends on valuation and quality together, not either alone. you should weigh PRTA's valuation and scores 25/100 on quality (lower-quality). A cheap price is only a bargain if the business is durable, and a premium can be justified by genuine quality, so the two questions, "is it cheap?" and "is it good?", only make sense side by side. Read the valuation against the quality scorecard, run the DCF on your own assumptions, and decide for yourself. This is analysis from SEC filings, not investment advice.
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Data sourced from SEC EDGAR filings and third-party price providers. Scores, valuations, and metrics are algorithmic estimates. This is not investment advice. See our Terms and Methodology.