Prothena (PRTA) Stock Price, News & Analysis

Company Overview

Prothena Corporation plc is a clinical-stage biotechnology company dedicated to the discovery and development of novel therapies for neurodegenerative and rare diseases driven by misfolded proteins. The company’s research focuses on immunotherapies and small molecules designed to target and clear disease-causing protein aggregates. Prothena leverages proprietary protein engineering and antibody discovery platforms to advance candidates through preclinical and clinical stages.

The company’s most advanced program is an antibody targeting aggregated alpha-synuclein for the potential treatment of Parkinson’s disease, currently in mid-stage clinical trials. Additional pipeline candidates include therapies for amyloid light chain (AL) amyloidosis and other protein misfolding disorders. Prothena collaborates with global pharmaceutical partners to further develop and commercialize its product candidates, pooling resources and expertise to accelerate research timelines.

Founded in 2012 as a spin-out from Elan Corporation, Prothena is headquartered in South San Francisco, California, with research operations in both the United States and Ireland. The company maintains a global focus, engaging regulators and trial sites across North America, Europe and Asia to support its clinical development programs. Prothena’s commitment to addressing high-unmet-need diseases is reflected in its strategic partnerships and research investments.

Prothena is led by President and Chief Executive Officer Gene Kinney, whose experience spans decades in the pharmaceutical and biotechnology sectors. Under his leadership, the company has built a multidisciplinary team of scientists, clinicians and commercial experts. Prothena’s board and management team bring deep expertise in protein science, immunology and drug development to guide the company’s mission of bringing new treatment options to patients worldwide.

Key Stats

• Today's Range: $8.10 to $8.35
• 50-Day Range: $6.22 to $8.77
• 52-Week Range: $4.32 to $22.71
• Volume: 713,676 shs
• Average Volume: 915,381 shs
• Market Capitalization: $439.25 million
• P/E Ratio: N/A
• Dividend Yield: N/A
• Price Target: $19.75
• Consensus Rating: Hold

Prothena Stock Analysis - MarketRank™

Prothena scored higher than 68% of companies evaluated by MarketBeat, and ranked 339th out of 960 stocks in the medical sector. Scores are calculated by averaging available category scores, with extra weight given to analysis and valuation.

Analyst's Opinion

• Score: 4.2 / 5
• Analyst Rating: Hold

Consensus Rating

Prothena has received a consensus rating of Hold. The company's average rating score is 2.33, and is based on 4 buy ratings, 4 hold ratings, and 1 sell rating.

Upside Potential

Prothena has a consensus price target of $19.75, representing about 142.0% upside from its current price of $8.16.

Amount of Analyst Coverage

Prothena has been the subject of 6 research reports in the past 90 days, demonstrating strong analyst interest in this stock.

Earnings and Valuation

• Score: 1.3 / 5
• Proj. Earnings Growth: Growing

Earnings Growth

Earnings for Prothena are expected to grow in the coming year, from ($4.04) to ($3.33) per share.

Price to Earnings Ratio vs. the Market

The P/E ratio of Prothena is -1.45, which means that its earnings are negative and its P/E ratio cannot be compared to companies with positive earnings.

Price to Earnings Ratio vs. Sector

The P/E ratio of Prothena is -1.45, which means that its earnings are negative and its P/E ratio cannot be compared to companies with positive earnings.

Price to Book Value per Share Ratio

Prothena has a P/B Ratio of 0.90. P/B Ratios below 1 indicate that a company could be undervalued with respect to its assets and liabilities.

Short Interest

• Score: 3.0 / 5
• Short Interest Level: Healthy

Percentage of Shares Shorted

9.34% of the float of Prothena has been sold short.

Short Interest Ratio / Days to Cover

Prothena has a short interest ratio ("days to cover") of 3.3, which is generally considered an acceptable ratio of short interest to trading volume.

Change versus previous month

Short interest in Prothena has recently decreased by 2.87%, indicating that investor sentiment is improving.

Dividend

• Score: 0.0 / 5
• Dividend Strength: N/A

Dividend Yield

Prothena does not currently pay a dividend.

Dividend Growth

Prothena does not have a long track record of dividend growth.

Sustainability and ESG

• Score: N/A
• Environmental Score: N/A

Percentage of Shares Shorted

9.34% of the float of Prothena has been sold short.

Short Interest Ratio / Days to Cover

Prothena has a short interest ratio ("days to cover") of 3.3, which is generally considered an acceptable ratio of short interest to trading volume.

Change versus previous month

Short interest in Prothena has recently decreased by 2.87%, indicating that investor sentiment is improving.

News and Social Media

• Score: 2.8 / 5
• News Sentiment: 0.99

News Sentiment

Prothena has a news sentiment score of 0.99. This score is calculated as an average of sentiment of articles about the company over the last seven days and ranges from 2 (good news) to -2 (bad news). This news sentiment score is similar to the average news sentiment of Medical companies.

News Coverage This Week

MarketBeat has tracked 12 news articles for Prothena this week, compared to 5 articles on an average week.

Search Interest

4 people have searched for PRTA on MarketBeat in the last 30 days.

MarketBeat Follows

Only 1 people have added Prothena to their MarketBeat watchlist in the last 30 days. This is a decrease of 0% compared to the previous 30 days.

Company Ownership

• Score: 1.7 / 5
• Insider Trading: N/A

Insider Buying vs. Insider Selling

In the past three months, Prothena insiders have not sold or bought any company stock.

Percentage Held by Insiders

Only 9.20% of the stock of Prothena is held by insiders.

Percentage Held by Institutions

97.08% of the stock of Prothena is held by institutions. High institutional ownership can be a signal of strong market trust in this company.

PRTA Stock Analysis - Frequently Asked Questions

How have PRTA shares performed this year?

Prothena's stock was trading at $13.85 at the beginning of 2025. Since then, PRTA shares have decreased by 41.1% and is now trading at $8.16.

How were Prothena's earnings last quarter?

Prothena Corporation plc (NASDAQ:PRTA) announced its earnings results on Monday, August, 4th. The biotechnology company reported ($1.86) EPS for the quarter, missing the consensus estimate of ($1.11) by $0.75. The biotechnology company had revenue of $4.42 million for the quarter, compared to analyst estimates of $5.36 million. Prothena had a negative trailing twelve-month return on equity of 62.17% and a negative net margin of 2,929.30%.

Who are Prothena's major shareholders?

Top institutional investors of Prothena include Armistice Capital LLC (4.15%), Federated Hermes Inc. (2.19%), Acadian Asset Management LLC (1.89%) and Geode Capital Management LLC (1.73%). Insiders that own company stock include William P Scully, Gene G Kinney, Tran Nguyen, Dennis J Selkoe, Richard T Collier, Lars Ekman, Wagner M Zago, Michael J Malecek, Karin L Walker, Hideki Garren, Carol D Karp and Brandon S Smith.
View institutional ownership trends.

How do I buy shares of Prothena?

Shares of PRTA stock can be purchased through any online brokerage account. Popular online brokerages with access to the U.S. stock market include Charles Schwab, E*TRADE, Fidelity, and Vanguard Brokerage Services.

What other stocks do shareholders of Prothena own?

Based on aggregate information from My MarketBeat watchlists, some other companies that Prothena investors own include Voyager Therapeutics (VYGR), American Water Works (AWK), Humana (HUM), Waste Connections (WCN), The RMR Group (RMR), DiamondRock Hospitality (DRH) and AU Optronics (AUOTY).

Company Calendar

• Last Earnings: 8/04/2025
• Today: 9/15/2025
• Next Earnings (Estimated): 11/11/2025
• Fiscal Year End: 12/31/2025

Industry, Sector and Symbol

• Stock Exchange: NASDAQ
• Sector: Medical
• Industry: MED - BIOMED/GENE
• Sub-Industry: Pharmaceutical Products
• Current Symbol: NASDAQ:PRTA
• CIK: 1559053
• Web: www.prothena.com
• Phone: (531) 236-2500
• Fax: 353-1902-3510
• Employees: 130
• Year Founded: N/A

Price Target and Rating

• Average Price Target for Prothena: $19.75
• High Price Target: $62.00
• Low Price Target: $6.00
• Potential Upside/Downside: +142.5%
• Consensus Rating: Hold
• Rating Score (0-4): 2.33
• Research Coverage: 9 Analysts

Profitability

• EPS (Trailing Twelve Months): ($5.64)
• Trailing P/E Ratio: N/A
• Forward P/E Ratio: N/A
• P/E Growth: N/A
• Net Income: -$122.31 million
• Net Margins: -2,929.30%
• Pretax Margin: -2,530.46%
• Return on Equity: -62.17%
• Return on Assets: -54.43%

Debt

• Debt-to-Equity Ratio: N/A
• Current Ratio: 5.68
• Quick Ratio: 5.68

Sales & Book Value

• Annual Sales: $10.34 million
• Price / Sales: 42.40
• Cash Flow: N/A
• Price / Cash Flow: N/A
• Book Value: $9.05 per share
• Price / Book: 0.90

Miscellaneous

• Outstanding Shares: 53,830,000
• Free Float: 48,878,000
• Market Cap: $438.45 million
• Optionable: Optionable
• Beta: -0.04