Who Is Buying Merck? Hedge Fund Activity in 2026
See which hedge funds are buying, selling, or holding Merck (MRK) based on latest 13F filings. 9 funds buying, institutional value $52.4B.
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Who Is Buying Merck? Hedge Fund Activity in 2026
Merck is a pharmaceutical titan whose fortunes are inextricably linked to Keytruda — the world's best-selling drug and an oncology blockbuster generating over $25 billion annually. At around $120.87 per share, MRK trades at a valuation that reflects both the enormous power of its current franchise and investor anxiety about Keytruda's patent cliff. The big question hanging over Merck is what comes after Keytruda — and hedge funds are answering with their wallets.
The latest 13F filings show one of the strongest buy signals in our tracking universe: 9 out of 17 funds are increasing their Merck positions, with several making massive additions.
Quick Answer
Across the funds we read directly from SEC filings, the largest Merck position in the Q2 2026 13Fs (period ending 30 June 2026) is Citadel Advisors at $248M (1,933,667 shares). Measured against the size of each filer's book rather than in dollars, the most concentrated holder is Citadel Advisors, where Merck is 0.1% of everything they report. Every figure here is aggregated by CUSIP from the filer's own information table with put/call rows excluded — a 13F lists options beside shares, and adding them together is what produces the inflated stakes quoted elsewhere. Filings lag roughly 45 days: this is positioning as of 30 June 2026, not today, and not investment advice.
Merck Institutional Snapshot
| Metric | Value |
|---|---|
| Funds Buying | 9 |
| Funds Selling | 4 |
| Funds Holding | 4 |
| Active Funds Tracked | 17 |
| Share Price | ~$120.87 |
A 9-to-4 buy-sell ratio makes Merck one of the most institutionally favored pharmaceutical stocks right now. The breadth and scale of the buying is particularly impressive.
Who holds Merck, and how much it matters to them
Read from each filer's Q2 2026 information table (period ending 30 June 2026).
| Fund | Position | Shares | Share of the fund's 13F book |
|---|---|---|---|
| Citadel Advisors | $248M | 1,933,667 | 0.1% of $171.84B |
| Millennium Management | $72M | 561,302 | 0.1% of $142.92B |
| Bridgewater Associates | $3.9M | 30,254 | 0.0% of $24.38B |
The last column is the one worth reading. A multi-strategy fund reporting a $100B+ book can hold a large dollar amount of Merck that means almost nothing to it, while a concentrated fund holding less in dollars may have several percent of its entire book in the name. Rankings by dollar value hide exactly that difference.
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Comparing each filer's Q1 2026 table with its Q2 2026 one, by share count — the change is what shows conviction, not the size of the position.
| Fund | Q1 2026 shares | Q2 2026 shares | Change |
|---|---|---|---|
| Bridgewater Associates | 0 | 30,254 | new position |
| Millennium Management | 1,970,691 | 561,302 | -72% |
| Citadel Advisors | 3,821,227 | 1,933,667 | -49% |
A fund absent from this table reported no Merck position in either quarter.
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FAQ
Why are hedge funds aggressively buying Merck (MRK) right now?
Funds like Appaloosa, Citadel, and Millennium are each holding $800M+ Merck positions, signaling rare alignment across fundamental, multi-strategy, and pod-based platforms. The likely thesis centers on Keytruda's continued cash generation combined with pipeline catalysts the broader market may be discounting too heavily.
What is the Keytruda patent cliff and how does it affect MRK?
Keytruda is Merck's oncology blockbuster generating over $25B annually, and its key patents begin expiring later this decade. The "patent cliff" describes the revenue risk as biosimilars enter — but institutional investors increasingly believe formulation extensions and pipeline diversification can offset much of that gap.
How important is Merck's oncology pipeline beyond Keytruda?
The pipeline includes Keytruda combination therapies, antibody-drug conjugates, and earlier-stage assets that could extend Merck's oncology franchise well past current patent expirations. Hedge funds at this scale typically aren't betting on one drug — they're modeling probability-weighted pipeline outcomes over multi-year horizons.
Why is Baker Bros reducing MRK while generalist hedge funds add?
Baker Brothers is one of the most specialized healthcare investors in the market, and their reduction stands out against the broad bullish consensus. This dissent could reflect deeper pipeline intelligence — or simply post-rally profit-taking — which is why tracking their next 13F filing is informative.
What role do Merck's vaccines and animal health businesses play in the thesis?
Beyond Keytruda, Merck operates a meaningful vaccines franchise (including Gardasil and pneumococcal candidates) and an animal health division that provides revenue diversification. Institutional buyers often cite this breadth as the reason single-product risk is overstated at current valuations.