Merck & Co., Inc.
MX ˙ BMV ˙ US58933Y1055
SecurityMX:MRK / Merck & Co., Inc.
InstitutionJoel Isaacson & Co., LLC
Latest Disclosed Ownership43,512 shares
Latest Disclosed Value $ 5,234,098
Joel Isaacson & Co., LLC reports 9.32% increase in ownership of MRK / Merck & Co., Inc.

On April 22, 2026 - Joel Isaacson & Co., LLC filed a 13F-HR form disclosing ownership of 43,512 shares of Merck & Co., Inc. (MX:MRK) valued at $5,234,098 USD as of March 31, 2026. The entity filed a previous 13F-HR on January 30, 2026 disclosing 39,801 shares of Merck & Co., Inc.. This represents a change in shares of 9.32% 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)
2026-04-22 2026-03-31 13F MERCK COM 58933Y105 43,512 3,711 9.32 5,234 24.95 0.1735
2026-01-30 2025-12-31 13F MERCK COM 58933Y105 39,801 1,309 3.40 4,189 29.69 0.1383
2025-10-30 2025-09-30 13F MERCK COM 58933Y105 38,492 9,828 34.29 3,231 42.35 0.1166
2025-07-23 2025-06-30 13F MERCK COM 58933Y105 28,664 -784 -2.66 2,269 -14.15 0.0923
2025-04-25 2025-03-31 13F MERCK COM 58933Y105 29,448 1,689 6.08 2,643 -4.27 0.1198
2025-01-28 2024-12-31 13F MERCK COM 58933Y105 27,759 372 1.36 2,761 -11.22 0.1245
2024-10-23 2024-09-30 13F MERCK COM 58933Y105 27,387 383 1.42 3,110 -6.97 0.1483
2024-07-24 2024-06-30 13F MERCK COM 58933Y105 27,004 2,207 8.90 3,343 2.17 0.1756
2024-04-30 2024-03-31 13F MERCK COM 58933Y105 24,797 2,966 13.59 3,272 37.48 0.1794
2024-02-12 2023-12-31 13F/A-1 MERCK COM 58933Y105 21,831 -142 -0.65 2,380 5.22 0.1461
2024-01-25 2023-12-31 13F MERCK COM 58933Y105 21,831 -142 2,380 0.1461
2023-10-24 2023-09-30 13F MERCK COM 58933Y105 21,973 683 3.21 2,262 -7.90 0.1548
2023-07-27 2023-06-30 13F MERCK COM 58933Y105 21,290 844 4.13 2,457 12.92 0.1644
2023-04-25 2023-03-31 13F MERCK COM 58933Y105 20,446 -247 -1.19 2,175 -5.23 0.1563
2023-01-27 2022-12-31 13F MERCK COM 58933Y105 20,693 1,720 9.07 2,296 40.45 0.1767
2022-10-14 2022-09-30 13F MERCK COM 58933Y105 18,973 1,150 6.45 1,634 0.55 0.1412
2022-07-15 2022-06-30 13F MERCK COM 58933Y105 17,823 893 5.27 1,625 11.53 0.1365
2022-04-21 2022-03-31 13F MERCK COM 58933Y105 16,930 24 0.14 1,457 12.42 0.1072
2022-01-19 2021-12-31 13F MERCK COM 58933Y105 16,906 -218 -1.27 1,296 0.78 0.0890
2021-10-21 2021-09-30 13F MERCK COM 58933Y105 17,124 -48 -0.28 1,286 -3.67 0.0971
2021-07-20 2021-06-30 13F MERCK COM 58933Y105 17,172 -952 -5.25 1,335 -4.44 0.1038
2021-04-23 2021-03-31 13F MERCK & CO. COM 58933Y105 18,124 -132 -0.72 1,397 -6.43 0.1225
2021-01-22 2020-12-31 13F MERCK & CO. COM 58933Y105 18,256 -20 -0.11 1,493 -1.52 0.1462
2020-10-14 2020-09-30 13F MERCK & CO. COM 58933Y105 18,276 26 0.14 1,516 7.44 0.1971
2020-07-21 2020-06-30 13F MERCK & CO. COM 58933Y105 18,250 334 1.86 1,411 2.39 0.2009
2020-04-21 2020-03-31 13F MERCK & CO. COM 58933Y105 17,916 692 4.02 1,378 -12.06 0.2399
2020-01-24 2019-12-31 13F MERCK COM 58933Y105 17,224 -330 -1.88 1,567 6.02 0.2058
2019-10-15 2019-09-30 13F MERCK COM 58933Y105 17,554 -5,823 -24.91 1,478 -24.59 0.2106
2019-07-11 2019-06-30 13F MERCK COM 58933Y105 23,377 -11,956 -33.84 1,960 -33.31 0.2853
2019-04-09 2019-03-31 13F MERCK COM 58933Y105 35,333 -854 -2.36 2,939 8.45 0.4288
2019-01-18 2018-12-31 13F MERCK COM 58933Y105 36,187 18,638 106.21 2,710 117.67 0.4294
2018-10-19 2018-09-30 13F MERCK COM 58933Y105 17,549 5 0.03 1,245 16.90 0.1957
2018-08-01 2018-06-30 13F MERCK COM 58933Y105 17,544 1,187 7.26 1,065 19.53 0.1783
2018-05-01 2018-03-31 13F MERCK COM 58933Y105 16,357 -697 -4.09 891 -7.19 0.1554
2018-01-30 2017-12-31 13F MERCK COM 58933Y105 17,054 -656 -3.70 960 -15.34 0.1666
2017-11-02 2017-09-30 13F MERCK COM 58933Y105 17,710 1,100 6.62 1,134 6.48 0.2075
2017-08-01 2017-06-30 13F MERCK COM 58933Y105 16,610 -202 -1.20 1,065 -0.28 0.2013
2017-05-05 2017-03-31 13F MERCK COM 58933Y105 16,812 209 1.26 1,068 9.31 0.2095
2017-01-23 2016-12-31 13F MERCK COM 58933Y105 16,603 1,654 11.06 977 4.72 0.1965
2016-10-25 2016-09-30 13F MERCK COM 58933Y105 14,949 397 2.73 933 11.34 0.1916
2016-07-22 2016-06-30 13F MERCK COM 58933Y105 14,552 -2,307 -13.68 838 -6.05 0.1783
2016-04-18 2016-03-31 13F MERCK COM 58933Y105 16,859 -479 -2.76 892 -2.62 0.1970
2016-01-15 2015-12-31 13F MERCK COM 58933Y105 17,338 -707 -3.92 916 2.81 0.2250
2015-10-21 2015-09-30 13F MERCK COM 58933Y105 18,045 701 4.04 891 -9.73 0.2378
2015-07-27 2015-06-30 13F MERCK COM 58933Y105 17,344 2,020 13.18 987 12.03 0.2530
2015-04-14 2015-03-31 13F MERCK & CO INC COM 58933Y105 15,324 690 4.72 881 6.02 0.2222
2015-01-09 2014-12-31 13F MERCK & CO INC COM 58933Y105 14,634 -76 -0.52 831 -4.70 0.2234
2014-10-22 2014-09-30 13F MERCK & CO INC COM 58933Y105 14,710 178 1.22 872 3.69 0.2666
2014-07-21 2014-06-30 13F MERCK & CO INC COM 58933Y105 14,532 1,862 14.70 841 16.97 0.2633
2014-04-14 2014-03-31 13F/A-1 MERCK & CO INC COM 58933Y105 12,670 -744 -5.55 719 7.15 0.2413
2014-04-11 2014-03-31 13F MERCK & CO INC COM 58933Y105 2,970 298
2014-02-12 2013-12-31 13F MERCK & CO INC COM 58933Y105 13,414 500 3.87 671 9.11 0.2436
2014-02-26 2013-09-30 13F MERCK & CO INC COM 58933Y105 12,914 5,125 65.80 615 69.89 0.2512
2014-03-03 2013-06-30 13F MERCK & CO INC COM 58933Y105 7,789 -500 -6.03 362 -1.09 0.1703
2014-03-03 2013-03-31 13F MERCK & CO INC COM 58933Y105 8,289 100 1.22 366 9.25 0.1854
2014-03-07 2012-12-31 13F MERCK & CO INC COM 58933Y105 8,189 8,189 335 0.2184
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.