Mass General Brigham, Inc holds a concentrated book of 6 stocks worth $361.1M as of Q2 2026 (disclosed Aug 7, 2026, a ~38-day 13F lag). This quarter they trimmed Ishares Msci Acwi ETF. Their largest long position is Ishares Msci Acwi ETF at 55% of the equity book. Cloning the disclosed picks since 2024 would be +11% (+5.6%/yr). That is a simulation of the disclosed long book, not audited returns.
The reported book (valued from quarter-end) returned +15.5%, a 4.8-point gap that is the cost of the ~38-day 13F disclosure lag a real follower can't avoid.
Growth of $10,000 cloning Mass General Brigham, Inc's disclosed long 13F book, rebalanced on each filing date (so it reflects each quarter's actual reporting lag, ~38 days for the latest filing, with no look-ahead), total-return basis (dividends reinvested), derived from end-of-day prices. “Their reported book” values the same picks from quarter-end, before they were public. S&P 500 is SPY total return over the same window. Excludes shorts, cash, options and non-13F holdings. Not investment advice.
Top-heavy: concentrated book
Share of the disclosed book in its largest positions. A higher top-5 share means a more concentrated, higher-conviction portfolio.
45% mapped to company sectors
Direct operating-company sectors from our SIC-based security master. ETF/fund and unclassified holdings stay visible separately; this is not ETF look-through exposure.
Estimated $ traded · quarter-end prices, no cost basis
No buys this quarter.
Other tracked managers holding the same core names as Mass General Brigham, Inc
| Manager / fund | Shared names | Their $ in those |
|---|---|---|
| FMR LLC | 6 / 6 | $3.4B |
| BlackRock, Inc. | 6 / 6 | $2.6B |
| MORGAN STANLEY | 6 / 6 | $2.3B |
| UBS Group AG | 6 / 6 | $865.9M |
| GOLDMAN SACHS GROUP INC | 6 / 6 | $549.0M |
| AMERIPRISE FINANCIAL INC | 6 / 6 | $415.2M |
| NORTHERN TRUST CORP | 6 / 6 | $408.6M |
| BANK OF AMERICA CORP /DE/ | 6 / 6 | $402.6M |
Ranked by how many of Mass General Brigham, Inc's top 6 disclosed names each fund also holds: a cross-fund conviction signal from the latest 13F of every tracked manager.
Bars show each stock's share of the portfolio. Click a row for its position history.
| # | Security | Value | Shares | % Port | Last move | History |
|---|---|---|---|---|---|---|
| 1 | Ishares TR MSCI ACWI ETF | $197.7M | 1.26M | 54.8% | ▼−42% Reduced · −894K sh | |
| 2 | Karman Hldgs Inc COM | $78.0M | 1.56M | 21.6% | —Held | |
| 3 | Revolution Medicines Inc COM | $64.4M | 344.1K | 17.8% | —Held | |
| 4 | Tango Therapeutics Inc COM | $11.1M | 354.2K | 3.1% | —Held | |
| 5 | Maze Therapeutics Inc COM | $7.2M | 240.0K | 2.0% | —Held | |
| 6 | Medline Inc COM | $2.7M | 68.4K | 0.7% | ▼−2.8% Reduced · −2K sh |
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curl -H "Authorization: Bearer YOUR_API_KEY" \ "https://arkolith.com/api/v1/funds/1678378/holdings"
Use Arkolith to show Mass General Brigham, Inc's latest holdings, largest changes, and filing provenance.
As-of date vs the date the SEC received each filing
Holdings from SEC EDGAR 13F-HR filings, updated quarterly, filed up to 45 days after quarter-end. Public domain. The book and weighting are long equity only; disclosed put/call options are listed separately and excluded from those totals. The performance line is a simulation of the disclosed long book, not an audited return.