Merck & Co., Inc.
MX ˙ BMV ˙ US58933Y1055
SecurityMX:MRK / Merck & Co., Inc.
InstitutionMariner, LLC
Latest Disclosed Ownership2,795,221 shares
Latest Disclosed Value $ 336,201,673
Mariner, LLC reports 1.53% increase in ownership of MRK / Merck & Co., Inc.

On May 13, 2026 - Mariner, LLC filed a 13F-HR form disclosing ownership of 2,795,221 shares of Merck & Co., Inc. (MX:MRK) valued at $336,201,673 USD as of March 31, 2026. The entity filed a previous 13F-HR on February 13, 2026 disclosing 2,753,230 shares of Merck & Co., Inc.. This represents a change in shares of 1.53% 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)
2026-05-13 2026-03-31 13F MERCK COM 58933Y105 2,795,221 41,991 1.53 336,202 16.00 0.3925
2026-02-13 2025-12-31 13F MERCK COM 58933Y105 2,753,230 225,264 8.91 289,838 36.65 0.3451
2025-11-14 2025-09-30 13F MERCK COM 58933Y105 2,527,966 35,579 1.43 212,108 7.51 0.2741
2025-08-14 2025-06-30 13F MERCK COM 58933Y105 2,492,387 -245,786 -8.98 197,296 -19.72 0.2848
2025-05-15 2025-03-31 13F MERCK COM 58933Y105 2,738,173 943,144 52.54 245,756 37.65 0.4089
2025-02-13 2024-12-31 13F MERCK COM 58933Y105 1,795,029 121,709 7.27 178,542 -6.04 0.2998
2024-11-13 2024-09-30 13F MERCK COM 58933Y105 1,673,320 13,808 0.83 190,026 -7.51 0.3371
2024-08-13 2024-06-30 13F MERCK COM 58933Y105 1,659,512 49,073 3.05 205,458 -3.31 0.3983
2024-05-15 2024-03-31 13F MERCK COM 58933Y105 1,610,439 22,574 1.42 212,496 22.75 0.4394
2024-02-14 2023-12-31 13F MERCK COM 58933Y105 1,587,865 -7,644 -0.48 173,109 5.39 0.4105
2023-11-13 2023-09-30 13F MERCK COM 58933Y105 1,595,509 59,234 3.86 164,257 -7.34 0.4405
2023-08-11 2023-06-30 13F MERCK COM 58933Y105 1,536,275 28,102 1.86 177,265 110,690.63 0.4737
2023-05-15 2023-03-31 13F MERCK COM 58933Y105 1,508,173 61,407 4.24 160 -99.90 0.4662
2023-02-14 2022-12-31 13F MERCK COM 58933Y105 1,446,766 149,941 11.56 160,519 43.73 0.5160
2022-11-10 2022-09-30 13F MERCK COM 58933Y105 1,296,825 54,451 4.38 111,684 -1.40 0.4464
2022-08-15 2022-06-30 13F MERCK COM 58933Y105 1,242,374 75,527 6.47 113,269 18.31 0.4651
2022-05-13 2022-03-31 13F MERCK COM 58933Y105 1,166,847 -257,872 -18.10 95,740 -12.32 0.3613
2022-02-14 2021-12-31 13F MERCK COM 58933Y105 1,424,719 179,720 14.44 109,191 16.77 0.4618
2021-11-15 2021-09-30 13F MERCK COM 58933Y105 1,244,999 127,400 11.40 93,512 7.59 0.4881
2021-08-24 2021-06-30 13F MERCK COM 58933Y105 1,117,599 71,434 6.83 86,916 7.77 0.5393
2021-05-07 2021-03-31 13F MERCK & CO. COM 58933Y105 1,046,165 73,867 7.60 80,649 1.40 0.5624
2021-02-16 2020-12-31 13F MERCK & CO. COM 58933Y105 972,298 92,713 10.54 79,535 9.01 0.6101
2020-11-13 2020-09-30 13F MERCK & CO. COM 58933Y105 879,585 -10,842 -1.22 72,959 5.96 0.6869
2020-08-14 2020-06-30 13F MERCK & CO. COM 58933Y105 890,427 58,675 7.05 68,857 7.44 0.6902
2020-05-14 2020-03-31 13F MERCK & CO. COM 58933Y105 831,752 30,335 3.79 64,086 -12.08 0.8008
2020-02-13 2019-12-31 13F MERCK COM 58933Y105 801,417 29,610 3.84 72,889 12.19 0.7570
2019-11-13 2019-09-30 13F MERCK COM 58933Y105 771,807 19,305 2.57 64,971 2.97 0.7771
2019-08-14 2019-06-30 13F MERCK COM 58933Y105 752,502 55,266 7.93 63,097 31.90 0.7527
2019-05-15 2019-03-31 13F MERCK COM 58933Y105 697,236 174,903 33.48 47,838 19.88 0.6819
2019-02-13 2018-12-31 13F MERCK COM 58933Y105 522,333 429,979 465.58 39,905 509.05 0.7105
2018-11-14 2018-09-30 13F MERCK COM 58933Y105 92,354 11,807 14.66 6,552 34.02 0.1685
2018-08-14 2018-06-30 13F MERCK COM 58933Y105 80,547 15,340 23.53 4,889 37.60 0.1386
2018-05-15 2018-03-31 13F MERCK COM 58933Y105 65,207 8,896 15.80 3,553 12.15 0.1274
2018-02-09 2017-12-31 13F MERCK COM 58933Y105 56,311 15,381 37.58 3,168 20.92 0.1226
2017-11-14 2017-09-30 13F MERCK COM 58933Y105 40,930 1,440 3.65 2,620 3.48 0.1184
2017-08-11 2017-06-30 13F MERCK COM 58933Y105 39,490 -22,923 -36.73 2,532 -36.16 0.1191
2017-05-15 2017-03-31 13F MERCK COM 58933Y105 62,413 1,421 2.33 3,966 10.47 0.1727
2017-02-14 2016-12-31 13F MERCK COM 58933Y105 60,992 6,540 12.01 3,590 5.59 0.1655
2016-11-14 2016-09-30 13F MERCK COM 58933Y105 54,452 4,125 8.20 3,400 17.28 0.1643
2016-08-12 2016-06-30 13F MERCK COM 58933Y105 50,327 14,077 38.83 2,899 51.07 0.1569
2016-05-13 2016-03-31 13F MERCK & CO INC COM 58933Y105 36,250 16,709 85.51 1,919 85.95 0.1140
2016-02-16 2015-12-31 13F MERCK & CO INC COM 58933Y105 19,541 -310,140 -94.07 1,032 -93.66 0.0662
2015-11-16 2015-09-30 13F MERCK & CO INC COM 58933Y105 329,681 11,006 3.45 16,284 -10.24 0.7235
2015-08-17 2015-06-30 13F MERCK & CO INC COM 58933Y105 318,675 307,093 2,651.47 18,142 2,628.12 0.8412
2015-05-15 2015-03-31 13F MERCK & CO INC COM 58933Y105 11,582 -2,104 -15.37 665 -14.41 0.0565
2015-02-13 2014-12-31 13F MERCK & CO INC COM 58933Y105 13,686 779 6.04 777 1.57 0.0699
2014-11-13 2014-09-30 13F MERCK & CO INC COM 58933Y105 12,907 -6,516 -33.55 765 -31.94 0.0861
2014-08-21 2014-06-30 13F MERCK & CO INC COM 58933Y105 19,423 2,630 15.66 1,124 17.94 0.1246
2014-05-08 2014-03-31 13F MERCK & CO INC COM 58933Y105 16,793 -991 -5.57 953 7.08 0.1227
2014-02-14 2013-12-31 13F MERCK & CO INC COM 58933Y105 17,784 1,522 9.36 890 14.99 0.1115
2013-11-14 2013-09-30 13F MERCK & CO INC COM 58933Y105 16,262 -6,806 -29.50 774 -27.80 0.1427
2013-08-19 2013-06-30 13F MERCK & CO INC COM 58933Y105 23,068 23,068 1,072 0.2260
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.