Merck & Co., Inc.
MX ˙ BMV ˙ US58933Y1055
SecurityMX:MRK / Merck & Co., Inc.
InstitutionChesapeake Asset Management Llc
Latest Disclosed Ownership15,053 shares
Latest Disclosed Value $ 1,810,725
Chesapeake Asset Management Llc ownership in MRK / Merck & Co., Inc.

On May 12, 2026 - Chesapeake Asset Management Llc filed a 13F-HR form disclosing ownership of 15,053 shares of Merck & Co., Inc. (MX:MRK) valued at $1,810,725 USD as of March 31, 2026. The entity filed a previous 13F-HR on January 8, 2026 disclosing 16,166 shares of Merck & Co., Inc.. This represents a change in shares of -6.88% during the quarter.

Chesapeake Asset Management Llc 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 0 of underlying shares valued at $0 USD and put options representing 0 of underlying shares valued at $0 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)
2026-05-12 2026-03-31 13F MERCK COM 58933Y105 15,053 -1,113 -6.88 1,811 6.41 1.4367
2026-01-08 2025-12-31 13F MERCK COM 58933Y105 16,166 -984 -5.74 1,702 18.21 1.4060
2025-10-17 2025-09-30 13F MERCK & CO INC NEW COM COM 58933Y105 17,150 -8,044 -31.93 1,439 -27.83 1.2739
2025-10-15 2025-06-30 13F MERCK AND COM 58933Y105 25,194 -316 -1.24 1,994 -12.89 1.7945
2026-01-05 2025-03-31 13F MERCK & CO INC NEW COM COM 58933Y105 25,510 -3,432 -11.86 2,290 -20.49 2.1547
2026-01-05 2024-12-31 13F MERCK COM 58933Y105 28,942 40 0.14 2,879 -12.28 2.6812
2026-01-05 2024-09-30 13F MERCK & CO INC NEW COM COM 58933Y105 28,902 -2,960 -9.29 3,282 -16.78 2.8499
2026-01-05 2024-06-30 13F MERCK & CO INC NEW COM COM 58933Y105 31,862 -210 -0.65 3,945 -6.78 3.7697
2026-01-05 2024-03-31 13F MERCK COM 58933Y105 32,072 -6,919 -17.75 4,232 -0.45 4.1821
2026-01-05 2023-12-31 13F MERCK & CO INC NEW COM COM 58933Y105 38,991 259 0.67 4,251 6.60 3.7899
2026-01-05 2023-09-30 13F MERCK & CO INC NEW COM COM 58933Y105 38,732 -3,148 -7.52 3,988 -17.49 3.8656
2026-01-05 2023-06-30 13F MERCK & CO INC NEW COM COM 58933Y105 41,880 -2,794 -6.25 4,833 1.68 4.3599
2026-01-05 2023-03-31 13F MERCK & CO INC NEW COM COM 58933Y105 44,674 10,065 29.08 4,753 50.95 4.3472
2020-02-06 2019-12-31 13F MERCK COM 58933Y105 34,609 0 0.00 3,148 8.07 5.3332
2019-10-30 2019-09-30 13F MERCK COM 58933Y105 34,609 -2,653 -7.12 2,913 -6.75 5.4763
2019-08-06 2019-06-30 13F MERCK COM 58933Y105 37,262 -150 -0.40 3,124 0.39 5.1529
2019-05-09 2019-03-31 13F MERCK COM 58933Y105 37,412 -12,070 -24.39 3,112 -17.69 5.2926
2019-02-06 2018-12-31 13F MERCK COM 58933Y105 49,482 -1,285 -2.53 3,781 5.00 6.9684
2018-11-06 2018-09-30 13F MERCK COM 58933Y105 50,767 -7,335 -12.62 3,601 2.10 4.1379
2018-08-08 2018-06-30 13F MERCK COM 58933Y105 58,102 -10,470 -15.27 3,527 -5.57 4.1084
2018-05-04 2018-03-31 13F MERCK COM 58933Y105 68,572 -1,572 -2.24 3,735 -5.37 4.0036
2018-02-06 2017-12-31 13F MERCK COM 58933Y105 70,144 -3,650 -4.95 3,947 -16.47 3.8050
2017-11-06 2017-09-30 13F MERCK COM 58933Y105 73,794 -350 -0.47 4,725 -0.57 4.2583
2017-08-04 2017-06-30 13F MERCK COM 58933Y105 74,144 -756 -1.01 4,752 -0.15 4.5211
2017-05-10 2017-03-31 13F MERCK COM 58933Y105 74,900 -425 -0.56 4,759 7.33 3.9200
2017-02-06 2016-12-31 13F MERCK COM 58933Y105 75,325 -100 -0.13 4,434 -5.80 3.8432
2016-11-08 2016-09-30 13F MERCK COM 58933Y105 75,425 0 0.00 4,707 8.33 4.2610
2016-08-09 2016-06-30 13F MERCK COM 58933Y105 75,425 -8,000 -9.59 4,345 -1.56 3.5344
2016-05-10 2016-03-31 13F MERCK & CO INC COM 58933Y105 83,425 0 0.00 4,414 0.16 3.6648
2016-02-10 2015-12-31 13F MERCK & CO INC COM 58933Y105 83,425 -387 -0.46 4,407 6.47 3.3850
2015-11-13 2015-09-30 13F MERCK & CO INC COM 58933Y105 83,812 0 0.00 4,139 -13.25 3.5159
2015-08-12 2015-06-30 13F MERCK & CO INC COM 58933Y105 83,812 0 0.00 4,771 -0.98 3.5025
2015-05-12 2015-03-31 13F MERCK & CO INC COM 58933Y105 83,812 0 0.00 4,818 1.22 3.5496
2015-02-17 2014-12-31 13F MERCK & CO INC COM 58933Y105 83,812 -550 -0.65 4,760 -4.80 2.9848
2014-11-14 2014-09-30 13F MERCK & CO INC COM 58933Y105 84,362 0 0.00 5,001 2.46 3.0536
2014-08-14 2014-06-30 13F MERCK & CO INC COM 58933Y105 84,362 0 0.00 4,880 1.90 3.0328
2014-05-15 2014-03-31 13F MERCK & CO INC COM 58933Y105 84,362 14,250 20.32 4,789 36.48 3.2403
2014-02-13 2013-12-31 13F MERCK & CO INC COM 58933Y105 70,112 0 0.00 3,509 5.12 2.0766
2013-11-13 2013-09-30 13F MERCK & CO INC COM 58933Y105 70,112 -1,550 -2.16 3,338 0.27 2.2372
2013-08-09 2013-06-30 13F MERCK & CO INC COM 58933Y105 71,662 71,662 3,329 2.4047
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
(%)
2026-01-05 2023-12-31 13F CALL MERCK & CO. INC. $120 EXP 10 OPTION Call 0 -100.00 0 n/a n/a n/a
2026-01-05 2023-09-30 13F CALL MERCK & CO. INC. $120 EXP 10 OPTION Call 2 0.00 0 n/a n/a n/a
2026-01-05 2023-06-30 13F CALL MERCK & CO. INC. $115 EXP 07 OPTION Call 2 0 n/a n/a n/a
Disclosed Put 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
(%)
2026-05-12 2026-03-31 13F PUT MERCK & CO. INC. $80 EXP 01 OPTION Put 0 -100.00 0 n/a n/a n/a
2026-01-08 2025-12-31 13F PUT MERCK & CO. INC. $80 EXP 01 OPTION Put 20 0.00 0 -100.00 n/a n/a n/a
2025-10-17 2025-09-30 13F PUT MERCK & CO. INC. $70 EXP 01 OPTION Put 20 0.00 4 -70.00 n/a n/a n/a
2025-10-15 2025-06-30 13F PUT MERCK AND CO. INC. 70 EXP 01 OPTION Put 20 33.33 11 100.00 n/a n/a n/a
2026-01-05 2025-03-31 13F PUT MERCK & CO. INC. $75 EXP 01 OPTION Put 15 25.00 5 n/a n/a n/a
2026-01-05 2024-12-31 13F PUT MERCK & CO. INC. $85 EXP 02 OPTION Put 12 0 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.