Major Prothena Investor Makes Bold New Move in the Market

Prothena shareholder William Scully increased his stake by purchasing 50,000 shares valued at $465,000 on June 5, 2026. This move follows a positive Q1 update featuring a $50M milestone from Novo Nordisk and improved cash guidance. While an analyst raised the price target due to enhanced liquidity and pipeline progress, TipRanks' AI Analyst maintains a Neutral rating citing weak profitability and cash burn risks.

New insider activity at Prothena ( (PRTA) ) has taken place on June 5, 2026.

Significant Prothena shareholder William Scully has increased his stake in the company by purchasing 50,000 shares of Prothena stock in a recent transaction, with the buy valued at $465,000, signaling a notable vote of confidence in the company’s prospects.

Prothena shares reacted to a stronger liquidity and de‑risked outlook after its Q1 update, where a $50M milestone from Novo Nordisk, better‑than‑prior 2026 cash guidance, and sharply reduced expected net loss and cash burn improved its financial runway. An analyst raised their price target mainly on this enhanced cash position, the milestone-funded pipeline progress, and advancement of key partnered Phase 3 programs, while broader sentiment still weighs persistent losses and milestone-driven revenue volatility.

Spark’s Take on PRTA Stock

According to Spark, TipRanks’ AI Analyst, PRTA is a Neutral.

The score is held back primarily by weak profitability and ongoing cash burn despite a low-debt balance sheet. Technical indicators also point to soft near-term momentum. These are partially offset by a low P/E screen and an earnings-call backdrop showing meaningful partnered pipeline advancement and a solid cash position, though with notable safety, timing, and partner-dependence risks.

To see Spark’s full report on PRTA stock,
click here.

More about Prothena

YTD Price Performance: -3.14%

Average Trading Volume: 519,105

Technical Sentiment Signal: Strong Sell

Current Market Cap: $467M