Prothena Corporation plc Stock Price and Value Analysis

Should you buy Prothena Corporation plc stock? (NasdaqGS:PRTA). Let's see how it does in our automated value investing analysis system.

Key Facts

Ticker: PRTA (NasdaqGS)
Current price: $8.75
Sector: Healthcare
Industry: Drug Manufacturers - General

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Hold-time calculator

Estimate how long you need to hold Prothena Corporation plc to reach your target.

Target type Target price Target total return %

Current price

Expected annual return (compound annual growth rate, CAGR)

Margin of safety (%)

Target price (Trendshare FV)

Include dividend yield
N/A

Advantages	Disadvantages	Neutral
None.	This company has wild ups and downs. This stock looks overpriced. This company is less known than others. This company is not making money.	This company pays no dividend.

Inside the PRTA Numbers

	PRTA Price (Prothena Corporation plc stock price per share)	$8.75
× PE Ratio Versus Sector The PE ratio measures the reported earnings of a company to its current stock price. While earnings are easy to manipulate on the balance sheet, this ratio gives you a sense of what buyers are willing to pay for the stock—what they believe it will do in the future. Comparing a stock's PE to the average PE of companies in its industry gives you a sense of market sentiment about the stock and how well it fares financially. It's not the only number, nor the most important, but comparing similar companies is valuable. A ratio far above or below that of its peers is significant. Industries are more specific than sectors, so companies within most industries are more similar than are companies within an industry. Be aware that the size and customers of companies are important to their prospects. Close ^[?]	PE Ratio versus Sector	2% lower than other Healthcare stocks
× PE Ratio Versus Industry The PE ratio measures the reported earnings of a company to its current stock price. While earnings are easy to manipulate on the balance sheet, this ratio gives you a sense of what buyers are willing to pay for the stock—what they believe it will do in the future. Comparing a stock's PE to the average PE of companies in its sector gives you a sense of market sentiment about the stock and how well it fares financially. It's not the only number, nor the most important, but comparing similar companies is valuable. A ratio far above or below that of its peers is significant. Be aware that sectors are very broad, with many types of companies in the same sector. Close ^[?]	PE Ratio versus Industry	65% lower than other Drug Manufacturers - General stocks
× Free Cash Flow Jitter The free cash flow jitter of a stock measures how much the company's free cash flow varies from its historical trend, on average. While it's always nice to make more money than you expected, a company with predictable free cash flow is stable and good. A company with wild swings in its free cash flow warrants further research. In general, the lower this number, the better. Close ^[?]	Free Cash Flow Jitter	50%

Recent Insider Activity

Open-market buys and sells reported by Prothena Corporation plc's officers, directors, and 10% owners on SEC Form 4. Routine transactions (tax withholding, option exercises, and stock grants) are excluded -- these are discretionary trades only.

Date	Insider	Type	Shares	Price
2025-05-06T00:00:00	EcoR1 Capital, LLC	Sell	1,984,053	$7.64
2025-05-05T00:00:00	EcoR1 Capital, LLC	Sell	977,693	$8.11
2025-05-02T00:00:00	EcoR1 Capital, LLC	Sell	3,317,938	$8.36
2025-01-14T00:00:00	SCULLY WILLIAM P	Buy	100,000	$12.79
2024-12-31T00:00:00	SCULLY WILLIAM P	Buy	1,200	$13.37
2024-12-31T00:00:00	SCULLY WILLIAM P	Buy	800	$13.39
2024-12-31T00:00:00	SCULLY WILLIAM P	Buy	30,000	$12.99
2024-12-20T00:00:00	SCULLY WILLIAM P	Buy	2,000	$15.91
2024-12-18T00:00:00	SCULLY WILLIAM P	Buy	73,436	$13.93

This stock has short interest! This means that people have shorted it.

Why does that matter? They've made a bet that price will decrease from where they bought it. Maybe there are financial problems, or maybe there's a value play.

As of the latest analysis, there are 8,196,964 shares shorted. With 36,682,343 shares available for purchase and an average trading volume over the past 10 trading days of 573,350, it would take at least 14.297 days for all of the short holders to cover their shorts.

What does this mean to you? At this volume, it'll take more than two trading weeks for shorts to cover. This may indicate a short squeeze play would work! If this stock has good fundamentals and it'll take a while for the short holders to cover, buying now could net you bigger short-term technical gains if and as the price rises.

Estimate Intrinsic Value (DCF)

Project future free cash flow and discount it back to today to compare market price vs intrinsic value. See how compound returns work over time.

📊 Intrinsic Value Calculator (DCF Method)

Calculate the present value of future cash flows to determine stock intrinsic value.

Annual Free Cash Flow ($):

Current or most recent year free cash flow (operating cash - capex)

Expected Annual Growth Rate (%):

Conservative estimate (3-7% for mature companies, 10-20% for growth)

Discount Rate (%):

Required rate of return (8-10% stable, 12-15% growth, 15%+ speculative)

Projection Period (Years):

Longer projections are less certain but may reveal more value

Terminal Value Multiple:

Exit multiple for terminal value (10-15x typical for mature companies)

Calculation Results

Total Intrinsic Value:

Discounted Cash Flows:

Terminal Value (PV):

Year	Future CF	Present Value

How to use this result: Compare the intrinsic value to the current stock price. If intrinsic value is significantly higher than market price (30-50% margin of safety), the stock may be undervalued. Remember, these are estimates based on your assumptions.

Should You Buy PRTA?

Learn how to evaluate stocks, understand expected returns, and build a value investing strategy.

See How Returns Compound →

Is Prothena Corporation plc Stock on Sale?

Based on our analysis, we believe that you should not buy Prothena Corporation plc right now. It might be a good stock to own—we just can't prove it with value analysis right now. Proceed with caution.

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Should You Buy PRTA Stock?

Does Prothena Corporation plc have a coherent story? Does it have a plan to continue to make money? Is it worth your time? Only you can decide where to go from here. Our investment guide helps you ask the right questions, including how to buy stocks. Use these research links for more information.

We don't yet have enough financial history for Prothena Corporation plc to produce a full worked example. Check back as more data becomes available, or see the current price and research links below.