NASDAQ:PRTA

Prothena Stock Insider Trading

Healthcare > Biotechnology

Buy PRTA

*Your capital is at risk

$8.12

-0.290 (-3.45%)

At Close: Jul 31, 2026

Prothena Stock Insider Power

Based on the 100 latest insides trades, we have calculated the insider power to be negative at -61.90. In total, the insiders bought 5.35M and sold 13.25M PRTA shares in the last 100 trades. The insider score can be negative despite buy/sell ratio being positive. The score focuses on the quality of the trades.

Insider Power (Last 100 transactions)	-61.90
● Buy	5.35M shares
● Sell	13.25M shares
81% Buy Activity Moderate Positive Correlation
Buy Signal Low Confidence Jul 28, 2026 Analysis Breakdown: Signal is highly questionable due to a strongly contradictory negative Insider Power Score of -61.9. Partially supported by a positive historical correlation. Confidence increased due to high data reliability score of 100. Supported by overwhelming buy-side pressure (81% buys).

Historical Insider Trades

Date	Type	Person	Role	Amount
Jul 29, 2026 Sell	Ordinary Shares, par value $0.01 per share S-Sale	Isaacs Michael John General Counsel & Company Sec.	Officer	8 386 Value: $71.1K
Jul 29, 2026 Sell	Ordinary Shares, par value $0.01 per share S-Sale	Kingston Anne Evans Chief Strategy Officer	Officer	7 662 Value: $64.9K
Jul 28, 2026 Sell	Ordinary Shares, par value $0.01 per share F-InKind	Isaacs Michael John General Counsel & Company Sec.	Officer	4 694 Value: $40.2K
Jul 28, 2026 Sell	Ordinary Shares, par value $0.01 per share F-InKind	Kingston Anne Evans Chief Strategy Officer	Officer	3 498 Value: $29.9K
Jul 28, 2026 Buy	Restricted Stock Units M-Exempt	Kinney Gene G. President And CEO	CEO / President	84 000 Value: $719.0K
Jul 28, 2026 Sell	Ordinary Shares, par value $0.01 per share D-Return	Kinney Gene G. President And CEO	CEO / President	84 000 Value: $719.0K
Jul 28, 2026 Buy	Ordinary Shares, par value $0.01 per share M-Exempt	Kinney Gene G. President And CEO	CEO / President	84 000 Value: $719.0K
Jul 28, 2026 Buy	Restricted Stock Units M-Exempt	Zago Wagner M. Chief Scientific Officer	Officer	51 000 Value: $436.6K
Jul 28, 2026 Sell	Ordinary Shares, par value $0.01 per share D-Return	Zago Wagner M. Chief Scientific Officer	Officer	51 000 Value: $436.6K
Jul 28, 2026 Buy	Ordinary Shares, par value $0.01 per share M-Exempt	Zago Wagner M. Chief Scientific Officer	Officer	51 000 Value: $436.6K
Jul 28, 2026 Buy	Ordinary Shares, par value $0.01 per share M-Exempt	Walker Karin L Chief Accounting Officer	Officer	15 000 Value: $128.4K
Jul 28, 2026 Sell	Ordinary Shares, par value $0.01 per share D-Return	Walker Karin L Chief Accounting Officer	Officer	15 000 Value: $128.4K
Jul 28, 2026 Buy	Restricted Stock Units M-Exempt	Walker Karin L Chief Accounting Officer	Officer	15 000 Value: $128.4K
Jul 28, 2026 Buy	Ordinary Shares, par value $0.01 per share M-Exempt	Swanson Chad J. Chief Development Officer	Officer	51 000 Value: $436.6K
Jul 28, 2026 Sell	Ordinary Shares, par value $0.01 per share D-Return	Swanson Chad J. Chief Development Officer	Officer	40 800 Value: $349.2K
Jul 28, 2026 Sell	Ordinary Shares, par value $0.01 per share F-InKind	Swanson Chad J. Chief Development Officer	Officer	3 467 Value: $29.7K
Jul 28, 2026 Buy	Restricted Stock Units M-Exempt	Swanson Chad J. Chief Development Officer	Officer	51 000 Value: $436.6K
Jul 28, 2026 Buy	Ordinary Shares, par value $0.01 per share M-Exempt	Smith Brandon S. Chief Operating Officer	C-Suite Officer	78 000 Value: $667.7K
Jul 28, 2026 Sell	Ordinary Shares, par value $0.01 per share D-Return	Smith Brandon S. Chief Operating Officer	C-Suite Officer	78 000 Value: $667.7K
Jul 28, 2026 Buy	Restricted Stock Units M-Exempt	Smith Brandon S. Chief Operating Officer	C-Suite Officer	78 000 Value: $667.7K
Jul 28, 2026 Buy	Ordinary Shares, par value $0.01 per share M-Exempt	Nguyen Tran Chief Strategy Officer And CFO	C-Suite Officer	57 000 Value: $487.9K
Jul 28, 2026 Sell	Ordinary Shares, par value $0.01 per share D-Return	Nguyen Tran Chief Strategy Officer And CFO	C-Suite Officer	57 000 Value: $487.9K
Jul 28, 2026 Buy	Restricted Stock Units M-Exempt	Nguyen Tran Chief Strategy Officer And CFO	C-Suite Officer	57 000 Value: $487.9K
Jun 16, 2026 Buy	Ordinary Shares, par value $0.01 per share P-Purchase	Scully William P 10 Percent Owner	10% Owner	20 000 Value: $158.0K
Jun 15, 2026 Sell	Ordinary Shares, par value $0.01 per share G-Gift	Scully William P 10 Percent Owner	10% Owner	325 000 Value: $0

About Insider Power

Insider Power is a proprietary algorithm developed by StockInvest.us to evaluate the significance of insider transactions. The calculation considers the size, type, and timing of transactions, as well as the insider’s role within the company.

It is important to note that, in general, there is little to no correlation between insider transactions and short-term stock price movements. In one of our studies, only 0.22%^* of stocks with insider activity showed a measurable correlation — and even then, it was unclear whether the effect was caused by insider actions or simply by the stock’s broader trend.

While our algorithms are designed to highlight potentially meaningful signals, these cannot be regarded as statistically significant on their own. Insider trading activity should therefore be seen as informative rather than as direct trading guidance. The Insider Power metric was created to present this information in a clearer and more accessible way, helping investors better understand the possible context of insider activity.

* October 6th, 2025 - Tested on 5562 stocks

ABOUT PROTHENA CORPORATION PLC

Prothena Corporation plc, a late-stage clinical company, focuses on discovery and development of novel therapies for life-threatening diseases in the United States. The company is involved in developing Birtamimab, an investigational humanized antibody that is in Phase III clinical trial for the treatment of AL amyloidosis; Prasinezumab, a humanized monoclonal antibody, which is in Phase IIb clinical trial for the treatment of Parkinson's disease...

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