Merck & Co., Inc.
MX ˙ BMV ˙ US58933Y1055
SecurityMX:MRK / Merck & Co., Inc.
InstitutionCalamos Wealth Management LLC
Latest Disclosed Ownership20,812 shares
Latest Disclosed Value $ 2,503,475
Calamos Wealth Management LLC reports 7.89% increase in ownership of MRK / Merck & Co., Inc.

On May 4, 2026 - Calamos Wealth Management LLC filed a 13F-HR form disclosing ownership of 20,812 shares of Merck & Co., Inc. (MX:MRK) valued at $2,503,475 USD as of March 31, 2026. The entity filed a previous 13F-HR on January 29, 2026 disclosing 19,290 shares of Merck & Co., Inc.. This represents a change in shares of 7.89% 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)
2026-05-04 2026-03-31 13F MERCK COM 58933Y105 20,812 1,522 7.89 2,503 23.30 0.0861
2026-01-29 2025-12-31 13F MERCK COM 58933Y105 19,290 3,529 22.39 2,030 53.56 0.0700
2025-10-20 2025-09-30 13F MERCK COM 58933Y105 15,761 1,351 9.38 1,323 15.96 0.0477
2025-07-29 2025-06-30 13F MERCK COM 58933Y105 14,410 -3,630 -20.12 1,141 -29.59 0.0483
2025-04-29 2025-03-31 13F MERCK COM 58933Y105 18,040 -1,984 -9.91 1,619 -18.68 0.0807
2025-01-24 2024-12-31 13F MERCK COM 58933Y105 20,024 -119,488 -85.65 1,992 -87.43 0.0996
2024-11-12 2024-09-30 13F MERCK COM 58933Y105 139,512 17,991 14.80 15,843 5.31 0.8117
2024-07-25 2024-06-30 13F MERCK COM 58933Y105 121,521 -15,493 -11.31 15,044 -16.79 0.8016
2024-05-08 2024-03-31 13F MERCK COM 58933Y105 137,014 2,922 2.18 18,079 23.68 1.0146
2024-01-31 2023-12-31 13F MERCK COM 58933Y105 134,092 -1,139 -0.84 14,619 5.00 0.9198
2023-10-26 2023-09-30 13F MERCK COM 58933Y105 135,231 115,843 597.50 13,922 522.35 1.0552
2023-07-28 2023-06-30 13F MERCK COM 58933Y105 19,388 286 1.50 2,237 10.09 0.1640
2023-05-04 2023-03-31 13F MERCK COM 58933Y105 19,102 -605 -3.07 2,032 -7.04 0.1592
2023-01-26 2022-12-31 13F MERCK COM 58933Y105 19,707 -119 -0.60 2,186 28.06 0.1697
2022-10-24 2022-09-30 13F MERCK COM 58933Y105 19,826 7,306 58.35 1,707 49.61 0.1464
2022-08-01 2022-06-30 13F MERCK COM 58933Y105 12,520 86 0.69 1,141 11.86 0.1012
2022-05-03 2022-03-31 13F MERCK COM 58933Y105 12,434 -3,969 -24.20 1,020 -18.85 0.0762
2022-02-01 2021-12-31 13F MERCK COM 58933Y105 16,403 307 1.91 1,257 3.97 0.0919
2021-10-26 2021-09-30 13F MERCK COM 58933Y105 16,096 -439 -2.65 1,209 -5.99 0.0977
2021-07-22 2021-06-30 13F MERCK COM 58933Y105 16,535 51 0.31 1,286 1.18 0.1001
2021-04-12 2021-03-31 13F MERCK & CO. COM 58933Y105 16,484 -1,301 -7.32 1,271 -12.65 0.1048
2021-01-27 2020-12-31 13F MERCK & CO. COM 58933Y105 17,785 2,026 12.86 1,455 11.32 0.1328
2020-10-26 2020-09-30 13F MERCK & CO. COM 58933Y105 15,759 -41,014 -72.24 1,307 -70.23 0.1495
2020-07-27 2020-06-30 13F MERCK & CO. COM 58933Y105 56,773 -4,277 -7.01 4,390 -6.54 0.5478
2020-04-28 2020-03-31 13F MERCK & CO. COM 58933Y105 61,050 1,946 3.29 4,697 -12.63 0.7162
2020-01-15 2019-12-31 13F MERCK COMMON STOCK 58933Y105 59,104 930 1.60 5,376 9.78 0.6333
2019-10-21 2019-09-30 13F MERCK COMMON STOCK 58933Y105 58,174 1,222 2.15 4,897 2.55 0.6546
2019-08-07 2019-06-30 13F MERCK COMMON STOCK 58933Y105 56,952 -622 -1.08 4,775 -0.27 0.6442
2019-04-12 2019-03-31 13F MERCK COMMON STOCK 58933Y105 57,574 40,001 227.63 4,788 256.52 0.6839
2019-01-24 2018-12-31 13F MERCK COMMON STOCK 58933Y105 17,573 5,683 47.80 1,343 59.31 0.2022
2018-10-22 2018-09-30 13F MERCK COMMON STOCK 58933Y105 11,890 -337 -2.76 843 13.61 0.1050
2018-07-17 2018-06-30 13F MERCK COMMON STOCK 58933Y105 12,227 -264 -2.11 742 8.96 0.0925
2018-04-13 2018-03-31 13F MERCK COMMON STOCK 58933Y105 12,491 -84,465 -87.12 681 -87.52 0.0854
2018-02-13 2017-12-31 13F MERCK COMMON STOCK 58933Y105 96,956 -11,684 -10.75 5,456 -21.56 0.7079
2017-10-25 2017-09-30 13F MERCK COMMON STOCK 58933Y105 108,640 760 0.70 6,956 0.61 0.9639
2017-08-09 2017-06-30 13F MERCK COMMON STOCK 58933Y105 107,880 1,484 1.39 6,914 2.28 0.9783
2017-04-20 2017-03-31 13F MERCK COMMON STOCK 58933Y105 106,396 2,384 2.29 6,760 10.40 1.0106
2017-02-06 2016-12-31 13F MERCK COMMON STOCK 58933Y105 104,012 302 0.29 6,123 -5.41 0.9854
2016-11-14 2016-09-30 13F MERCK COMMON STOCK 58933Y105 103,710 3,635 3.63 6,473 12.28 1.1064
2016-07-26 2016-06-30 13F MERCK COMMON STOCK 58933Y105 100,075 4,915 5.16 5,765 14.50 1.0187
2016-04-25 2016-03-31 13F MERCK COMMON STOCK 58933Y105 95,160 8,167 9.39 5,035 9.58 0.9689
2016-02-05 2015-12-31 13F MERCK COMMON STOCK 58933Y105 86,993 1,871 2.20 4,595 9.30 0.9152
2015-11-10 2015-09-30 13F MERCK COMMON STOCK 58933Y105 85,122 2,468 2.99 4,204 -10.65 1.0091
2015-08-17 2015-06-30 13F MERCK COMMON STOCK 58933Y105 82,654 21,745 35.70 4,705 34.39 1.1113
2015-05-12 2015-03-31 13F MERCK COMMON STOCK 58933Y105 60,909 5,229 9.39 3,501 10.72 0.8749
2015-02-13 2014-12-31 13F MERCK COMMON STOCK 58933Y105 55,680 -519 -0.92 3,162 -5.07 0.9077
2014-11-14 2014-09-30 13F MERCK COMMON STOCK 58933Y105 56,199 1,430 2.61 3,331 5.15 0.9616
2014-08-14 2014-06-30 13F MERCK COMMON STOCK 58933Y105 54,769 -1,985 -3.50 3,168 -1.68 0.9035
2014-05-16 2014-03-31 13F MERCK COMMON STOCK 58933Y105 56,754 173 0.31 3,222 13.77 0.9539
2014-02-14 2013-12-31 13F MERCK COMMON STOCK 58933Y105 56,581 1,737 3.17 2,832 8.46 0.8683
2013-11-13 2013-09-30 13F MERCK COMMON STOCK 58933Y105 54,844 3,331 6.47 2,611 9.11 0.8532
2013-08-12 2013-06-30 13F MERCK COMMON STOCK 58933Y105 51,513 51,513 2,393 0.8473
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.