Alnylam CEO Vesting Tranche Issued; Mandatory Sell-to-Cover Reduces Holdings
Rhea-AI Filing Summary
Yvonne Greenstreet, Director and CEO of Alnylam Pharmaceuticals (ALNY), reported a mix of equity activity tied to performance compensation and tax withholding on vested awards. On 08/15/2025 she received 14,252 shares upon vesting of 30% of a performance-based stock unit awarded 03/01/2024 after a clinical milestone determination. Following that vesting, multiple automatic sales occurred on 08/18/2025 to satisfy mandatory sell-to-cover tax withholding, reducing her direct holdings from 63,200 to 56,221 shares. The filing also shows 407 shares held indirectly via a managed account and shares acquired under the company 401(k) matching program.
Positive
- Performance-based PSU vested: 14,252 shares issued upon achievement of a clinical milestone, reflecting compensation tied to operational milestones
- 401(k) match participation: 407 shares held indirectly from the issuer's 401(k) matching program, indicating use of company benefit plans
Negative
- Reduction in direct holdings: Direct beneficial ownership decreased from 63,200 to 56,221 shares following mandatory sell-to-cover sales
- Concentrated sales on one day: Multiple sell transactions on 08/18/2025 at prices from ~$447.53 to $456.00 reduced insider stake
Insights
TL;DR: Routine executive vesting and mandatory sell-to-cover sales; governance signal is standard compensation mechanics, not an extraordinary event.
The filing documents the vesting of a performance-based stock unit tranche tied to a clinical milestone, which was approved by the compensation committee on 08/15/2025 and settled as 14,252 shares. The subsequent clustered sales on 08/18/2025 are described as mandatory sell-to-cover transactions to satisfy statutory tax withholding obligations rather than discretionary disposals. Holdings moved from 63,200 to 56,221 shares directly owned, and an additional 407 shares are held indirectly via a managed account. These actions align with common executive equity compensation settlement practices and do not by themselves indicate a change in corporate strategy or confidence.
TL;DR: Insufficient impact on valuation; transactions are compensation-related and routine.
The reported sales occurred across multiple price ranges, with reported weighted-average prices noted per tranche (examples: $447.98, $449.92, $452.96, up to $456.00). The filing discloses that sales prices represent weighted averages of multiple transactions and that detailed per-transaction breakdowns are available on request. The net effect was a reduction of direct share ownership by 6,979 shares. For investors, this is an expected tax-driven liquidity event following PSU vesting and not a material change to insider ownership trends absent further context.
Insider Trade Summary
| Type | Security | Shares | Price | Value |
|---|---|---|---|---|
| Sale | Common Stock | 194 | $447.98 | $87K |
| Sale | Common Stock | 450 | $449.92 | $202K |
| Sale | Common Stock | 195 | $450.92 | $88K |
| Sale | Common Stock | 514 | $451.99 | $232K |
| Sale | Common Stock | 1,646 | $452.96 | $746K |
| Sale | Common Stock | 2,716 | $454.04 | $1.23M |
| Sale | Common Stock | 1,204 | $454.84 | $548K |
| Sale | Common Stock | 60 | $455.82 | $27K |
| Grant/Award | Common Stock | 14,252 | $0.00 | -- |
| holding | Common Stock | -- | -- | -- |
Footnotes (1)
- On March 1, 2024, the reporting person was granted a performance-based stock unit (PSU) under the 2018 Stock Incentive Plan. The shares subject to the PSU vest based on the achievement of three specified performance measures. The shares reported were issued to the reporting person upon vesting of thirty (30) percent of the shares subject to the PSU based on the achievement of a clinical milestone, as determined by The People, Culture and Compensation Committee of the Issuer Board of Directors on August 15, 2025. Represents shares automatically sold by the Company on behalf of the reporting person pursuant to a mandatory sell-to-cover provision in the award agreement required to cover minimum statutory tax withholding obligations that became due upon the vesting and settlement of a tranche of restricted stock units granted to the reporting person on March 1, 2024. The price reported represents the weighted average sales price of shares sold in multiple transactions at prices ranging from $447.53 to $448.45. The reporting person will provide to the issuer, any security holder of the issuer or the SEC staff, upon request, information regarding the number of shares sold at each price within the range. The price reported represents the weighted average sales price of shares sold in multiple transactions at prices ranging from $449.21 to $450.16. The reporting person will provide to the issuer, any security holder of the issuer or the SEC staff, upon request, information regarding the number of shares sold at each price within the range. The price reported represents the weighted average sales price of shares sold in multiple transactions at prices ranging from $450.42 to $451.39. The reporting person will provide to the issuer, any security holder of the issuer or the SEC staff, upon request, information regarding the number of shares sold at each price within the range. The price reported represents the weighted average sales price of shares sold in multiple transactions at prices ranging from $451.48 to $452.48. The reporting person will provide to the issuer, any security holder of the issuer or the SEC staff, upon request, information regarding the number of shares sold at each price within the range. The price reported represents the weighted average sales price of shares sold in multiple transactions at prices ranging from $452.49 to $453.49. The reporting person will provide to the issuer, any security holder of the issuer or the SEC staff, upon request, information regarding the number of shares sold at each price within the range. The price reported represents the weighted average sales price of shares sold in multiple transactions at prices ranging from $453.50 to $454.45. The reporting person will provide to the issuer, any security holder of the issuer or the SEC staff, upon request, information regarding the number of shares sold at each price within the range. The price reported represents the weighted average sales price of shares sold in multiple transactions at prices ranging from $454.58 to $455.55. The reporting person will provide to the issuer, any security holder of the issuer or the SEC staff, upon request, information regarding the number of shares sold at each price within the range. The price reported represents the weighted average sales price of shares sold in multiple transactions at prices ranging from $455.65 to $456.00. The reporting person will provide to the issuer, any security holder of the issuer or the SEC staff, upon request, information regarding the number of shares sold at each price within the range. Reflects shares of ALNY common stock acquired by the Reporting Person under the issuer 401(k) plan as a result of the issuer 401(k) matching contribution program.
