Merck & Co., Inc.
MX ˙ BMV ˙ US58933Y1055
SecurityMX:MRK / Merck & Co., Inc.
InstitutionKorea Investment CORP
Latest Disclosed Ownership1,897,151 shares
Latest Disclosed Value $ 228,208,294
Korea Investment CORP ownership in MRK / Merck & Co., Inc.

On May 13, 2026 - Korea Investment CORP filed a 13F-HR form disclosing ownership of 1,897,151 shares of Merck & Co., Inc. (MX:MRK) valued at $228,208,294 USD as of March 31, 2026. The entity filed a previous 13F-HR on February 13, 2026 disclosing 2,006,037 shares of Merck & Co., Inc.. This represents a change in shares of -5.43% during the quarter.

Korea Investment CORP has a history of taking positions in derivatives of the underlying security (MRK) in the form of stock options. The firm currently holds call options representing 2,177,255 of underlying shares valued at $181,082,000 USD .

Note: prior versions of this page mistakenly stated that the share values represented the number of options, not the number of underlying shares. For more information on the data backing these reports, please see the SEC document Frequently Asked Questions About Form 13F.

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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Institutional Put/Call Ratios
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In addition to reporting standard equity and debt issues, institutions with more than 100MM assets under management must also disclose their put and call option holdings. Since put options generally indicate negative sentiment, and call options indicate positive sentiment, we can get a sense of the overall institutional sentiment by plotting the ratio of puts to calls. The chart to the right plots the historical put/call ratio for this instrument.

Using Put/Call Ratio as an indicator of investor sentiment overcomes one of the key deficiencies of using total institutional ownership, which is that a significant amount of assets under management are invested passively to track indices. Passively-managed funds do not typically buy options, so the put/call ratio indicator more closely tracks the sentiment of actively-managed funds.

MX:MRK / Merck & Co., Inc. Historical Put/Call Ratio
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 1,897,151 -108,886 -5.43 228,208 8.08 0.4728
2026-02-13 2025-12-31 13F MERCK COM 58933Y105 2,006,037 228,890 12.88 211,155 41.57 0.4157
2025-11-13 2025-09-30 13F MERCK COM 58933Y105 1,777,147 -198,111 -10.03 149,156 -4.61 0.3068
2025-08-13 2025-06-30 13F MERCK COM 58933Y105 1,975,258 2,642 0.13 156,361 -11.69 0.3479
2025-05-14 2025-03-31 13F MERCK COM 58933Y105 1,972,616 -22,734 -1.14 177,062 -10.80 0.4291
2025-02-12 2024-12-31 13F MERCK COM 58933Y105 1,995,350 -19,801 -0.98 198,497 -13.26 0.4706
2024-11-13 2024-09-30 13F MERCK COM 58933Y105 2,015,151 -161,203 -7.41 228,841 -15.07 0.5431
2024-08-13 2024-06-30 13F MERCK COM 58933Y105 2,176,354 -79,799 -3.54 269,433 -9.50 0.6788
2024-05-14 2024-03-31 13F MERCK COM 58933Y105 2,256,153 -281,282 -11.09 297,699 7.62 0.7554
2024-02-13 2023-12-31 13F MERCK COM 58933Y105 2,537,435 76,378 3.10 276,631 9.18 0.7264
2023-11-13 2023-09-30 13F MERCK COM 58933Y105 2,461,057 115,906 4.94 253,366 -6.37 0.7463
2023-08-11 2023-06-30 13F MERCK COM 58933Y105 2,345,151 136 0.01 270,607 8.47 0.7603
2023-05-12 2023-03-31 13F MERCK COM 58933Y105 2,345,015 -334,369 -12.48 249,486 -16.08 0.7264
2023-02-13 2022-12-31 13F MERCK COM 58933Y105 2,679,384 -126,866 -4.52 297,278 23.01 0.9339
2022-11-10 2022-09-30 13F MERCK COM 58933Y105 2,806,250 62,708 2.29 241,674 -3.38 0.7439
2022-08-12 2022-06-30 13F MERCK COM 58933Y105 2,743,542 55,077 2.05 250,129 13.39 0.7646
2022-05-13 2022-03-31 13F MERCK COM 58933Y105 2,688,465 725,867 36.99 220,589 46.65 0.5456
2022-02-09 2021-12-31 13F MERCK COM 58933Y105 1,962,598 -515,621 -20.81 150,414 -19.19 0.3909
2021-11-12 2021-09-30 13F MERCK COM 58933Y105 2,478,219 -937,353 -27.44 186,139 -29.93 0.5550
2021-08-12 2021-06-30 13F MERCK COM 58933Y105 3,415,572 -130,014 -3.67 265,629 -2.82 0.7608
2021-05-13 2021-03-31 13F MERCK & CO. COM 58933Y105 3,545,586 -314,728 -8.15 273,329 -13.44 0.8628
2021-02-10 2020-12-31 13F MERCK & CO. COM 58933Y105 3,860,314 240,500 6.64 315,774 5.17 0.9487
2020-11-12 2020-09-30 13F MERCK & CO. COM 58933Y105 3,619,814 -251,500 -6.50 300,264 0.30 1.0609
2020-08-12 2020-06-30 13F MERCK & CO. COM 58933Y105 3,871,314 117,990 3.14 299,369 3.67 1.0998
2020-05-14 2020-03-31 13F MERCK & CO. COM 58933Y105 3,753,324 -252,631 -6.31 288,781 -20.74 1.2676
2020-02-11 2019-12-31 13F MERCK COM 58933Y105 4,005,955 489,200 13.91 364,342 23.07 1.3284
2019-11-12 2019-09-30 13F MERCK COM 58933Y105 3,516,755 238,000 7.26 296,040 7.68 1.2514
2019-08-12 2019-06-30 13F MERCK COM 58933Y105 3,278,755 1,101,500 50.59 274,924 51.82 1.1820
2019-05-15 2019-03-31 13F MERCK CALL 58933Y105 2,177,255 73,942 3.52 181,082 12.67 0.8150
2019-02-13 2018-12-31 13F MERCK CALL 58933Y105 2,103,313 -55,900 -2.59 160,714 4.92 0.8735
2018-11-13 2018-09-30 13F MERCK CALL 58933Y105 2,159,213 -168,940 -7.26 153,175 8.39 0.7064
2018-08-13 2018-06-30 13F MERCK CALL 58933Y105 2,328,153 2,538 0.11 141,319 7.99 0.6439
2018-05-09 2018-03-31 13F MERCK COM 58933Y105 2,316,153 -9,462 -0.41 126,161 -3.59 0.5871
2018-02-12 2017-12-31 13F MERCK CALL 58933Y105 2,325,615 -244,380 -9.51 130,862 -20.48 0.5956
2017-10-25 2017-09-30 13F MERCK CALL 58933Y105 2,569,995 -84,500 -3.18 164,557 -3.27 0.7602
2017-07-31 2017-06-30 13F MERCK CALL 58933Y105 2,654,495 59,061 2.28 170,127 3.16 0.7928
2017-04-25 2017-03-31 13F MERCK CALL 58933Y105 2,595,434 2,595,434 164,914 0.8180
2017-02-13 2016-12-31 13F MERCK CALL ADDED 58933Y105 3,256,489 704,963 27.63 191,710 20.39 0.9213
2016-11-09 2016-09-30 13F MERCK CALL ADDED 58933Y105 2,551,526 201,509 8.57 159,241 17.62 0.8487
2016-08-12 2016-06-30 13F MERCK CALL ADDED 58933Y105 2,350,017 495,400 26.71 135,384 37.97 0.8061
2016-05-12 2016-03-31 13F MERCK CALL ADDED 58933Y105 1,854,617 39,000 2.15 98,127 2.32 0.7176
2016-02-01 2015-12-31 13F MERCK CALL ADDED 58933Y105 1,815,617 150,200 9.02 95,900 16.59 0.6681
2015-11-12 2015-09-30 13F MERCK NEW CALL ADDED 58933Y105 1,665,417 257,017 18.25 82,254 2.59 0.6550
2015-08-13 2015-06-30 13F MERCK NEW CALL ADDED 58933Y105 1,408,400 -177,400 -11.19 80,180 -12.04 0.6834
2015-05-11 2015-03-31 13F MERCK NEW CALL ADDED 58933Y105 1,585,800 207,000 15.01 91,152 16.41 0.7101
2015-02-12 2014-12-31 13F MERCK NEW CALL ADDED 58933Y105 1,378,800 -141,300 -9.30 78,302 -13.11 0.6427
2014-11-14 2014-09-30 13F MERCK NEW CALL ADDED 58933Y105 1,520,100 -179,800 -10.58 90,112 -8.37 0.7352
2014-08-14 2014-06-30 13F MERCK NEW CALL ADDED 58933Y105 1,699,900 -38,200 -2.20 98,339 -0.34 0.8186
2014-05-14 2014-03-31 13F MERCK NEW CALL ADDED 58933Y105 1,738,100 87,900 5.33 98,672 19.47 0.8737
2014-02-06 2013-12-31 13F MERCK NEW CALL ADDED 58933Y105 1,650,200 -242,400 -12.81 82,593 -8.34 0.7810
2013-11-07 2013-09-30 13F/A-1 MERCK NEW CALL ADDED 58933Y105 1,892,600 10,100 0.54 90,107 3.05 0.9574
2013-11-05 2013-09-30 13F MERCK NEW CALL ADDED 58933Y105 1,255,100 59,755
2013-08-08 2013-06-30 13F MERCK NEW CALL ADDED 58933Y105 1,882,500 1,882,500 87,442 1.0481
Disclosed Call Options
File
Date
Effective
Date
Form Security Class ID Opt Avg Share
Price
Shares ΔShares
(%)
Value
(x1000)
ΔValue
(%)
Prior Allocation
(%)
Allocation
(%)
ΔAllocation
(%)
Cost Basis
(x1000)
Profit
(x1000)
Return
(%)
2019-05-15 2019-03-31 13F MERCK CALL 2,177,255 3.52 181,082 12.67 n/a n/a n/a
2019-02-13 2018-12-31 13F MERCK CALL 2,103,313 -2.59 160,714 4.92 n/a n/a n/a
2018-11-13 2018-09-30 13F MERCK CALL 2,159,213 -7.26 153,175 8.39 n/a n/a n/a
2018-08-13 2018-06-30 13F MERCK CALL 2,328,153 0.11 141,319 7.99 n/a n/a n/a
2018-02-12 2017-12-31 13F MERCK CALL 2,325,615 -9.51 130,862 -20.48 n/a n/a n/a
2017-10-25 2017-09-30 13F MERCK CALL 2,569,995 -3.18 164,557 -3.27 n/a n/a n/a
2017-07-31 2017-06-30 13F MERCK CALL 2,654,495 2.28 170,127 3.16 n/a n/a n/a
2017-04-25 2017-03-31 13F MERCK CALL 2,595,434 164,914 n/a n/a n/a
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.