Form 4: Alnylam CEO's Stock Vesting & Tax-Related Sales

Alnylam Pharmaceuticals CEO Yvonne Greenstreet reported the vesting of performance-based stock units and subsequent tax-related sales of common stock.

Summary

• Yvonne Greenstreet, Chief Executive Officer and Director of Alnylam Pharmaceuticals, Inc. (ALNY), reported transactions involving the company's common stock.
• On October 1, 2025, Greenstreet acquired 3,860 shares of common stock upon the vesting of a performance-based stock unit (PSU) granted on February 24, 2021. This vesting was triggered by the public reporting of the initiation of a Phase 3 clinical study for an RNAi therapeutic.
• Also on October 1, 2025, Greenstreet acquired 14,252 shares of common stock from the vesting of another PSU granted on March 1, 2024. This vesting was based on the public reporting of the initiation of a Phase 3 clinical study in a prevalent indication.
• Following these acquisitions, Greenstreet's direct beneficial ownership increased to 74,333 shares.
• On October 2, 2025, a total of 8,817 shares of common stock were automatically sold by the company on Greenstreet's behalf to cover minimum statutory tax withholding obligations related to the PSU vesting.
• These sales occurred at weighted average prices ranging from $446.53 to $457.43 per share.
• After the tax-related sales, Greenstreet's direct beneficial ownership decreased to 65,409 shares.
• Additionally, 407 shares of ALNY common stock were indirectly acquired by Greenstreet through a managed account under the issuer's 401(k) plan, as a result of the company's matching contribution program.

Sentiment

Score: 6

Explanation: The vesting of performance-based stock units is a positive indicator of company progress and achievement of strategic milestones, particularly the advancement of therapeutics into Phase 3 clinical studies. The subsequent sales are non-discretionary for tax purposes, thus not reflecting a negative sentiment from management.

Positives

• The vesting of performance-based stock units indicates the achievement of significant company milestones, specifically the initiation of two distinct Phase 3 clinical studies for RNAi therapeutics.
• The initiation of Phase 3 clinical studies suggests progress in the company's drug development pipeline and potential future commercialization.

Negatives

• The disposition of 8,817 shares, while mandatory for tax purposes, represents a reduction in the executive's direct holdings.

Future Outlook

The filing reports the achievement of performance milestones related to the initiation of Phase 3 clinical studies, which are critical steps in the development and potential commercialization of new RNAi therapeutics. While the filing itself does not provide explicit forward-looking guidance, these milestones are indicative of the company's progress towards its strategic objectives.

Industry Context

The initiation of Phase 3 clinical studies is a significant event in the biotechnology and pharmaceutical industry, representing a crucial stage in drug development before potential regulatory approval and market entry. For Alnylam, a leader in RNAi therapeutics, advancing multiple candidates into Phase 3 underscores its commitment to expanding its pipeline and addressing prevalent diseases, aligning with broader industry trends of innovation in novel therapeutic modalities.

Related Party Transactions

• The reported transactions involve the Chief Executive Officer and Director of Alnylam Pharmaceuticals, Inc., Yvonne Greenstreet, and are considered insider transactions.

Stakeholder Impact

• Shareholders: The vesting of performance-based stock units, tied to the initiation of Phase 3 clinical studies, signals positive progress in the company's pipeline, which could enhance long-term shareholder value. The tax-related sales are routine and do not indicate a change in management's outlook.
• Employees: The achievement of corporate milestones, such as advancing clinical studies, can positively impact employee morale and potentially future equity compensation programs.
• Customers/Patients: The progression of RNAi therapeutics into Phase 3 studies indicates potential for new treatment options for prevalent diseases in the future.

Next Steps

• Continued progress and reporting on the Phase 3 clinical studies mentioned as triggers for PSU vesting.

Key Dates

Recommendation

The reported transactions are routine for an executive, involving the vesting of performance-based stock units and subsequent mandatory sales to cover tax obligations. They do not indicate a change in management's discretionary view of the company's prospects. The underlying performance milestones (Phase 3 initiation) are positive for the company, but this Form 4 itself does not provide new information warranting a change in investment recommendation.

Keywords

Alnylam, ALNY, Yvonne Greenstreet, Form 4, Insider Transaction, Stock Vesting, Performance Stock Units, PSU, Phase 3 Clinical Study, RNAi Therapeutic, Biotechnology, Pharmaceuticals