Avoid the stress of overpaying for a stock or missing an opportunity by using the right tools and insights to evaluate Prothena Corporation plc before investing.

In this article, we go over a few key elements for understanding Prothena Corporation plc’s stock price such as:

• Prothena Corporation plc’s current stock price and volume
• Why Prothena Corporation plc’s stock price changed recently
• Upgrades and downgrades for PRTA from analysts
• PRTA’s stock price momentum as measured by its relative strength

About Prothena Corporation plc (PRTA)

Before we jump into Prothena Corporation plc’s stock price, history, target price and what caused it to recently dip, let’s take a look at some background.

Prothena Corporation plc, a late-stage clinical biotechnology company, focuses on discovery and development of novel therapies to treat diseases caused by protein dysregulation in the United States. Its product pipeline include Prasinezumab, an investigational humanized monoclonal antibody which is in phase 2b clinical trial, as well as phase 1 and 2 clinical trials for the treatment of parkinson’s disease and other synucleinopathies. The company also develops Coramitug, an investigational antibody, which is in phase 2 clinical trial for potential treatment of transthyretin amyloidosis; BMS-986446, an investigational antibody, which is in phase 2 clinical trial to treat Alzheimer’s disease; PRX012, an investigational antibody, which is in phase 1 clinical trial to treat Alzheimer’s disease; PRX123, a Dual Aß-Tau Vaccine, which is in preclinical trial for treating Alzheimer’s disease; and PRX019, an investigational antibody, which is in phase 1 clinical trial for the potential treatment of neurodegenerative diseases. It has a license, development, and commercialization agreement with F. Hoffmann-La Roche Ltd. and Hoffmann-La Roche Inc. to develop and commercialize antibodies that target a-synuclein, including prasinezumab; and master collaboration agreement with Bristol Myers Squibb to develop and commercialize antibodies targeting tau, TDP-43. Prothena Corporation plc was incorporated in 2012 and is based in Dublin, Ireland.

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Prothena Corporation plc’s Stock Price as of Market Close

As of December 05, 2025, 4:00 PM, CST, Prothena Corporation plc’s stock price was $11.070.

Prothena Corporation plc is down 0.81% from its previous closing price of $11.160.

During the last market session, Prothena Corporation plc’s stock traded between $10.975 and $11.480. Currently, there are approximately 53.83 million shares outstanding for Prothena Corporation plc.

Prothena Corporation plc’s trailing earnings per share are negative, so the stock does not have a meaningful P/E ratio. We suggest investors evaluate other financial metrics to understand its overall valuation.

Prothena Corporation plc Stock Price History

Prothena Corporation plc’s (PRTA) price is currently up 2.98% so far this month.

During the month of December, Prothena Corporation plc’s stock price has reached a high of $11.570 and a low of $10.140.

Over the last year, Prothena Corporation plc has hit prices as high as $17.660 and as low as $4.320. Year to date, Prothena Corporation plc’s stock is down 20.07%.

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What Caused Prothena Corporation plc Stock’s Price to Dip?

Stock prices are primarily based on seller supply and buyer demand. But have you ever wondered about what other factors affect a stock's price?

When an analyst changes their opinion of a stock by upgrading or downgrading their rating, it often leads to a sudden stock price adjustment. As of December 05, 2025, there were 0 analysts who downgraded Prothena Corporation plc’s stock and 2 analysts who upgraded over the last month.

Additionally, you'll want to evaluate Prothena Corporation plc’s financial health and valuation. Investors can use AAII's Value Grade, which combines six key valuation metrics like P/E and P/S ratios for a comprehensive analysis to conduct analysis on Prothena Corporation plc’s valuation and financial health. This approach mitigates the limitations of single-metric evaluations.

Prothena Corporation plc’s current valuation based on AAII’s Value Grade is a D, which means it is considered to be Expensive.

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Lastly, news and media coverage as well as recent press reports about the company or its industry may cause stock prices to fluctuate. You can check out the most recent news articles about Prothena Corporation plc (PRTA) by visiting AAII Stock Evaluator.

Relative Price Strength of Prothena Corporation plc

Relative price strength measures a stock's performance against the market, helping investors identify stocks that are outperforming benchmarks.

For AAII’s Momentum Grade, a weighted relative price strength is calculated. Follow this link to learn more about the Momentum Grade.

As of December 05, 2025, Prothena Corporation plc has a weighted four-quarter relative price strength of 8.15%, which translates to a Momentum Score of 79 and is considered to be Strong.

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Prothena Corporation plc Stock Price: Bottom Line

As of December 5, 2025, Prothena Corporation plc’s stock price is $11.070, which is down 0.81% from its previous closing price.

AAII advises against making stock decisions based solely on price or past returns. Instead, consider a variety of metrics, fundamentals, and analytics to evaluate a stock like Prothena Corporation plc stock prices are influenced by market supply and demand and offer just a snapshot of a company's overall health.

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