Form 4: Arcellx CFO Sells Shares Under 10b5-1 Plan

Arcellx Chief Financial Officer Michelle Gilson sold 5,946 shares of common stock in early October 2025, executed under a pre-arranged Rule 10b5-1 trading plan.

Summary

• Michelle Gilson, Chief Financial Officer of Arcellx, Inc. (ACLX), reported sales of common stock.
• The transactions were executed pursuant to a Rule 10b5-1 trading plan established on March 21, 2025.
• On October 3, 2025, 4,882 shares were sold at a weighted average price of $86.0036 per share, with prices ranging from $85.99 to $86.20.
• On October 6, 2025, an additional 1,064 shares were sold at a weighted average price of $86.2155 per share, with prices ranging from $86.05 to $86.435.
• Following these transactions, Michelle Gilson beneficially owns 13,830 shares of Arcellx common stock directly.

Sentiment

Score: 5

Explanation: The insider sales were conducted under a pre-arranged Rule 10b5-1 trading plan, which is a common practice for executives for personal financial planning and diversification, mitigating any negative sentiment typically associated with insider selling.

Positives

• The sales were conducted under a Rule 10b5-1 trading plan, indicating pre-scheduled transactions and reducing concerns about opportunistic insider selling.
• The reporting person undertakes to provide full information regarding the number of shares sold at each separate price upon request, demonstrating transparency.

Negatives

• Insider selling, even under a 10b5-1 plan, can sometimes be perceived as a lack of confidence by some investors, though this is often for personal financial planning or diversification.

Future Outlook

No forward-looking statements or guidance are provided in this Form 4 filing.

Management Comments

• "The sale of shares reported on this Form 4 was effected pursuant to a Rule 10b5-1 trading plan entered into by the Reporting Person on March 21, 2025."
• "The Reporting Person undertakes to provide upon request by the Commission staff, the issuer or a security holder of the issuer, full information regarding the number of shares sold at each separate price."

Industry Context

This filing reports a routine insider transaction and does not contain information relevant to broader industry trends or competitors.

Corporate Governance

Related Party Transactions

• This filing details an insider transaction by Michelle Gilson, the Chief Financial Officer, involving the sale of company common stock.

Stakeholder Impact

• Shareholders: Provides transparency regarding insider stock ownership changes. The sale itself represents a minor reduction in insider holdings, but the 10b5-1 plan context generally limits negative interpretations.

Next Steps

• The Reporting Person will provide full information regarding the number of shares sold at each separate price upon request by the Commission staff, the issuer, or a security holder.

Key Dates

Recommendation

The reported transactions are routine insider sales executed under a pre-established Rule 10b5-1 trading plan. Such plans are common for executives to manage personal finances and diversify holdings, and they typically do not signal a change in the company's fundamental outlook or warrant a strong buy or sell recommendation based solely on this filing. Investors should consider broader company performance and market conditions.

Keywords

Arcellx, ACLX, Insider Trading, Form 4, Stock Sale, Michelle Gilson, CFO, 10b5-1 Plan, Beneficial Ownership