Merck & Co., Inc.
MX ˙ BMV ˙ US58933Y1055
SecurityMX:MRK / Merck & Co., Inc.
InstitutionWoodline Partners LP
Latest Disclosed Ownership1,071,080 shares
Latest Disclosed Value $ 128,840,213
Woodline Partners LP reports 6.61% increase in ownership of MRK / Merck & Co., Inc.

On May 15, 2026 - Woodline Partners LP filed a 13F-HR/A form disclosing ownership of 1,071,080 shares of Merck & Co., Inc. (MX:MRK) valued at $128,840,213 USD as of March 31, 2026. The entity filed a previous 13F-HR on February 17, 2026 disclosing 1,004,699 shares of Merck & Co., Inc.. This represents a change in shares of 6.61% during the quarter.

Institutional Ownership: 13F and NPORT Filings

The Security and Class in the table below are shown exactly as filed by the investor. We do our best to track continuity of investments through acquisitions, and this will be reflected in the table as changes in names. In addition to descriptive data, performance of the investment is shown over time. To calculate quarterly performance, we first calculate cost basis of the shares purchased during the quarter, then use that to calculate gross profit. Quarterly return is Gross Profit / Starting Portfolio value.

Note that cost basis is calculated and stored in thousands, so small quarterly changes in shares frequently result in a cost basis of zero.

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Disclosed Equity Positions (from 13F/NPORT Filings)
File
Date		 Effective
Date		Form Security Class ID Avg Price
Paid (Est)		 Reported
Shares		 ΔShares ΔShares
(%)		 Reported
Value
(x1000)		 ΔValue
(%)		 Alloc
(%)		 ΔAlloc ΔAlloc (%) Cost Basis
(x1000)		 Unrealized
Gain/Loss
(x1000)
2026-05-15 2026-03-31 13F/A-1 MERCK COM 58933Y105 1,071,080 66,381 6.61 128,840 21.83 0.4872
2026-05-15 2026-03-31 13F MERCK COM 58933Y105 1,071,080 66,381 128,840 0.4870
2026-02-17 2025-12-31 13F MERCK COM 58933Y105 1,004,699 96,155 10.58 105,755 38.69 0.4098
2025-11-14 2025-09-30 13F MERCK COM 58933Y105 908,544 130,118 16.72 76,254 23.75 0.3589
2025-08-14 2025-06-30 13F MERCK COM 58933Y105 778,426 13,900 1.82 61,620 -10.21 0.3255
2025-05-15 2025-03-31 13F MERCK COM 58933Y105 764,526 33,192 4.54 68,624 -5.68 0.4463
2025-02-14 2024-12-31 13F MERCK COM 58933Y105 731,334 -117,315 -13.82 72,753 -24.51 0.4918
2024-11-14 2024-09-30 13F MERCK COM 58933Y105 848,649 137,296 19.30 96,373 9.43 0.8116
2024-08-14 2024-06-30 13F MERCK COM 58933Y105 711,353 -264,664 -27.12 88,066 -31.62 0.8406
2024-05-15 2024-03-31 13F MERCK COM 58933Y105 976,017 181,561 22.85 128,785 48.69 1.1854
2024-02-14 2023-12-31 13F MERCK COM 58933Y105 794,456 -88,044 -9.98 86,612 -4.67 0.9419
2023-11-14 2023-09-30 13F MERCK COM 58933Y105 882,500 0 0.00 90,853 -10.78 1.0651
2023-08-14 2023-06-30 13F MERCK COM 58933Y105 882,500 180,697 25.75 101,832 36.39 1.2070
2023-05-15 2023-03-31 13F MERCK COM 58933Y105 701,803 189,468 36.98 74,665 31.35 1.0158
2023-02-14 2022-12-31 13F MERCK COM 58933Y105 512,335 -466,152 -47.64 56,844 -32.54 0.7605
2022-11-14 2022-09-30 13F MERCK COM 58933Y105 978,487 412,503 72.88 84,267 63.30 1.1776
2022-08-15 2022-06-30 13F MERCK COM 58933Y105 565,984 -303,407 -34.90 51,601 -27.66 0.7952
2022-05-16 2022-03-31 13F MERCK COM 58933Y105 869,391 849,367 4,241.74 71,334 4,547.17 1.1579
2022-02-14 2021-12-31 13F MERCK COM 58933Y105 20,024 0 0.00 1,535 2.06 0.0220
2021-11-15 2021-09-30 13F MERCK COM 58933Y105 20,024 -366,870 -94.82 1,504 -95.00 0.0246
2021-08-16 2021-06-30 13F MERCK COM 58933Y105 386,894 101,539 35.58 30,089 36.78 0.5611
2021-05-17 2021-03-31 13F MERCK & CO. COM 58933Y105 285,355 285,355 21,998 0.4879
2021-02-16 2020-12-31 13F MERCK & CO. COM 58933Y105 0 -194,137 -100.00 0 -100.00
2020-11-16 2020-09-30 13F MERCK & CO. COM 58933Y105 194,137 194,137 16,104 0.5278
Legend
Shares
The total number of shares held by the institution at the end of the reporting period (the effective date). This is provided in the filing.
Value
The total value of the shares as of the effective date. This is provided in the filing.
Avg. Share Price
The weighted average share price of the shares held by the institution. We use FIFO accounting to determine this price
Class
This is the security class as indicated by the filer. There are a variety of values for this field. Common values include "EC" = equity common, "EP" - equity preferred
Allocation (%)
The percent of the institution's portfolio that this position represents. This is provided in NPORT filings. For 13F filings, we calculate it.
Change in Allocation
The change in allocation from the prior reporting period. This is calculated as current allocation - prior allocation.
Change in Allocation (%)
The percent change in allocation from the prior reporting period. This is calculated as (current allocation - prior allocation) / prior allocation.
Cost Basis
The total cost of the shares held. This is calculated as reported shares * avg. share price
Unrealized Gain/Loss
This is the market value of the position as of the effective date minus the cost basis.