NASDAQ:PRTA

Prothena Stock Insider Trading

Healthcare > Biotechnology

Buy PRTA

*Your capital is at risk

$9.55

+0.400 (+4.37%)

At Close: Jun 23, 2026

Prothena Stock Insider Power

Based on the 100 latest insides trades, we have calculated the insider power to be negative at -63.38. In total, the insiders bought 5.32M and sold 14.38M 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)	-63.38
● Buy	5.32M shares
● Sell	14.38M shares
81% Buy Activity Moderate Positive Correlation
Buy Signal Low Confidence Jun 11, 2026 Analysis Breakdown: Signal is highly questionable due to a strongly contradictory negative Insider Power Score of -63.38. 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
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
Jun 11, 2026 Buy	Ordinary Shares, par value $0.01 per share P-Purchase	Scully William P 10 Percent Owner	10% Owner	125 000 Value: $1.02M
Jun 08, 2026 Buy	Stock Option (Right to Buy)	Isaacs Michael John General Counsel & Company Sec.	Officer	12 000 Value: $363.6K
Jun 08, 2026 Buy	Stock Option (Right to Buy)	Isaacs Michael John General Counsel & Company Sec.	Officer	8 800 Value: $466.1K
Jun 08, 2026 Buy	Stock Option (Right to Buy)	Isaacs Michael John General Counsel & Company Sec.	Officer	8 250 Value: $267.7K
Jun 08, 2026 Buy	Stock Option (Right to Buy)	Isaacs Michael John General Counsel & Company Sec.	Officer	10 000 Value: $226.0K
Jun 08, 2026 Buy	Stock Option (Right to Buy)	Isaacs Michael John General Counsel & Company Sec.	Officer	17 500 Value: $192.3K
Jun 08, 2026 Buy	Ordinary Shares, par value $0.01 per share	Isaacs Michael John General Counsel & Company Sec.	Officer	0 Value: $0
Jun 08, 2026 Buy	Stock Option (Right to Buy)	Isaacs Michael John General Counsel & Company Sec.	Officer	8 612 Value: $128.7K
Jun 08, 2026 Buy	Stock Option (Right to Buy)	Isaacs Michael John General Counsel & Company Sec.	Officer	37 500 Value: $351.0K
Jun 08, 2026 Buy	Stock Option (Right to Buy)	Isaacs Michael John General Counsel & Company Sec.	Officer	50 000 Value: $525.0K
Jun 04, 2026 Buy	Ordinary Shares, par value $0.01 per share P-Purchase	Scully William P 10 Percent Owner	10% Owner	50 000 Value: $465.3K
Jun 02, 2026 Buy	Ordinary Shares, par value $0.01 per share P-Purchase	Scully William P 10 Percent Owner	10% Owner	50 000 Value: $471.3K
May 22, 2026 Buy	Ordinary Shares, par value $0.01 per share P-Purchase	Scully William P 10 Percent Owner	10% Owner	100 000 Value: $981.3K
May 15, 2026 Buy	Stock Option (Right to Buy) A-Award	Welch Daniel G Director	Director	27 000 Value: $263.5K
May 15, 2026 Buy	Stock Option (Right to Buy) A-Award	Selkoe Dennis J. Director	Director	27 000 Value: $263.5K
May 15, 2026 Buy	Stock Option (Right to Buy) A-Award	Ekman Lars Director	Director	27 000 Value: $263.5K
May 15, 2026 Buy	Stock Option (Right to Buy) A-Award	Dunn William H. Jr. Director	Director	27 000 Value: $263.5K
May 15, 2026 Buy	Stock Option (Right to Buy) A-Award	Cooke Shane Director	Director	27 000 Value: $263.5K
May 15, 2026 Buy	Stock Option (Right to Buy) A-Award	Collier Richard T Director	Director	27 000 Value: $263.5K
May 07, 2026 Buy	Ordinary Shares, par value $0.01 per share	Scully William P 10 Percent Owner	10% Owner	0 Value: $0
May 07, 2026 Buy	Ordinary Shares, par value $0.01 per share	Scully William P 10 Percent Owner	10% Owner	0 Value: $0
May 07, 2026 Buy	Ordinary Shares, par value $0.01 per share	Scully William P 10 Percent Owner	10% Owner	0 Value: $0
Apr 10, 2026 Buy	Stock Option (Right to Buy)	Kingston Anne Evans Chief Strategy Officer	Officer	3 000 Value: $90.9K

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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