Merck & Co., Inc.
PERIOD 2026-Q1 · SOURCE: SEC EDGAR (PUBLIC)
Holdings as of the 2026-Q1 13F-HR filing. 13F is disclosed up to 45 days after quarter-end.
What a 13F does — and does not — show
These figures come from Form 13F, a quarterly filing that large US institutional managers must submit to the SEC. It is a useful window, but a partial and lagged one, so read it carefully:
- It is a snapshot, up to 45 days old. A 13F shows what a manager held on the last day of a quarter, filed up to 45 days later — the fund may have traded since.
- Long US-listed stocks only. It excludes short positions, cash, bonds, most derivatives, and non-US or private holdings, so it is not the fund’s whole portfolio.
- Reported 13F value is not assets under management. Every share and concentration figure below is a percentage of the reported 13F value only — not the firm’s total assets.
- It describes, it does not recommend. A large or long-held position is not an endorsement, and none of this is investment advice.
Concentration
Share of reported portfolio value. Long US-listed equity positions as filed; percentages are of reported 13F value, which excludes shorts, cash, non-US and private holdings.
| Tier | Reported value | Share |
|---|---|---|
| Top position | $117M | 33.6% |
| Top 5 | $311M | 88.9% |
| Top 10 | $348M | 99.7% |
Top holdings
| # | Security | Shares | Reported value | % of value |
|---|---|---|---|---|
| 1 | MRNA MODERNA INC added | 2,308,190 | $117M | 33.6% |
| 2 | PSNL PERSONALIS INC trimmed | 14,044,943 | $89M | 25.6% |
| 3 | KYMR KYMERA THERAPEUTICS INC added | 772,165 | $64M | 18.4% |
| 4 | TRDA ENTRADA THERAPEUTICS INC added | 1,739,768 | $22M | 6.3% |
| 5 | EIKN EIKON THERAPEUTICS INC new | 1,666,666 | $18M | 5.0% |
| 6 | AKTS AKTIS ONCOLOGY INC new | 952,844 | $17M | 4.9% |
| 7 | ALEC ALECTOR INC added | 3,545,719 | $8M | 2.2% |
| 8 | STRO SUTRO BIOPHARMA INC added | 272,351 | $7M | 1.9% |
| 9 | EVAXION BIOTECH A/S trimmed | 1,214,126 | $5M | 1.3% |
| 10 | VRDN VIRIDIAN THERAPEUTICS INC trimmed | 93,414 | $2M | 0.5% |
| 11 | XLO XILIO THERAPEUTICS INC | 105,982 | $891K | 0.3% |
| 12 | CARM CARISMA THERAPEUTICS INC | 1,473,240 | $48K | 0.0% |
Sector mix
Reported 13F value by sector, as a share of reported portfolio value. Sectors come from company reference data joined to each holding. 37% of this value is not classified to a sector and is excluded from the mix. Long US-listed equity positions as filed.
| Sector | Reported value | Share |
|---|---|---|
| Healthcare | $221M | 63.2% |
How this filer invests
Reproducible measures computed from the positions in this filer’s own 13F filings — not from any outside estimate.
How concentrated the book is
Across 14 reported positions. Shares are of reported 13F value (long US-listed equity), which is not the firm’s total assets. The concentration index (HHI) is the sum of each position’s squared weight — higher means a book concentrated in fewer names.
How much the book turned over
Between the 2025-Q4 and 2026-Q1 filings, on the stable identity of each holding (share classes combined). New positions and exits are counted by presence; adds and trims by reported value, so a stock split does not read as a change.
Long-term holdings vs. higher turnover
Of its 14 largest reported positions, 11 have appeared in its 5 most recent consecutive quarterly filings (more than a year), and 3 are more recent. This filer reads as a longer-term holder: most of its largest positions have persisted for more than a year.
Notable sizing changes among its long-held positions:
- EVAXUSD — share count increased 124%
- XLO — share count reduced 93%
- STRO — share count reduced 90%
Directional only, measured over the filer’s largest reported positions across the quarters we track. 13F is a quarter-end snapshot, so a name can be held continuously yet slip in and out of the largest positions; this is a starting question, not a verdict.
Quarter-over-quarter changes
What changed between the 2025-Q4 and 2026-Q1 13F filings. New positions and exits reflect the tracked snapshot; adds and trims are measured on reported value (split-invariant), and moves under $0.25M are omitted as noise.
Between the 2025-Q4 and 2026-Q1 filings, this filer opened its largest new position in EIKN, added most to MRNA, and trimmed PSNL the most. This describes what the 13F reported — not a recommendation.
New positions 2
- EIKN$18M
- AKTS$17M
Largest adds
- MRNA$49M
- KYMR$4M
- TRDA$4M
- STRO$4M
- ALEC$2M
Largest trims
- PSNL$22M
- EVAXUSD$1M
- VRDN$1M
Portfolio trend
Reported 13F value and position count by filing quarter (independent scales).
Frequently asked
What does Merck & Co., Inc. own?
Merck & Co., Inc. reported 14 long US-listed equity positions worth $349M in its 2026-Q1 13F filing. The largest positions and their reported values are listed above.
What changed in Merck & Co., Inc.'s portfolio last quarter?
The quarter-over-quarter section lists new positions, exits, and the largest adds and trims versus the prior filing, measured on reported value.
Where does this data come from?
Holdings are parsed from SEC Form 13F-HR filings on EDGAR (public filings). 13F is disclosed up to 45 days after quarter-end and reflects long US-listed equity positions only. Informational, not investment advice.
About 13F filings
A Form 13F is a quarterly disclosure that institutional investment managers with over $100 million in US-listed equities must file with the SEC. In plain English: it is a snapshot of the long stock positions a fund held at the end of a quarter. It is filed up to 45 days after quarter-end, so it is backward-looking — the manager may have traded since — and it covers long US-listed equities only, not short positions, cash, or private holdings. Reading a 13F tells you what a manager owned, not whether you should own it.