CIK: 0001678378
Total reported value
$468.9M
Reporting period: 2026-03-31 · Number of holdings: 6
Mass General Brigham, Inc disclosed 6 holdings in its latest 13F filing for the period ending 2026-03-31, with total reported value of $468.9M and a quarterly turnover rate of 60.5%.
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Mass General Brigham, Inc's disclosed holdings carry a Herfindahl concentration index of 0.466 — mathematically equivalent to about 2 equally-sized positions, well below its 6 actual disclosed holdings. That gap points to a strategy built around a small core of high-conviction bets rather than broad diversification.
Position sizes vary widely across the portfolio (a coefficient of variation of 1.47), with a handful of outsized bets alongside many smaller positions.
No strong tilt toward either adding to existing winners or initiating outsized new positions was observed in the latest reported quarter.
Sector classification currently covers about 34% of this portfolio's disclosed value; the remainder includes holdings (e.g. unmapped tickers, options, or other security types) not yet covered by our sector mapping.
Trim ACWI
-53.3% -$360.1M
Add KRMN
0.0% $10.7M
Add RVMD
0.0% $6.1M
Add TNGX
0.0% $4.3M
Add MDLN
+167.6% $2.0M
Add MAZE
0.0% -$2.8M
| # | Ticker | Issuer | Asset Subclass | Weight | Weight Change | Shares Change | 4Q Trend |
|---|---|---|---|---|---|---|---|
| 1 | ACWI | Ishares Msci Acwi ETF | ETF-Other | 62.42% | -18.20% | -53.33% | |
| 2 | KRMN | Karman Holdings INC | Stock-Industrials | 26.67% | +12.56% | — | |
| 3 | RVMD | Revolution Medicines INC | Stock-Healthcare | 7.14% | +3.76% | — | |
| 4 | TNGX | Tango Therapeutics INC | Stock-Other | 1.58% | +1.19% | — | |
| 5 | MAZE | Maze Therapeutics INC | Stock-Other | 1.53% | +0.30% | — | |
| 6 | MDLN | Medline Inc-cl A | Stock-Other | 0.67% | +0.53% | +167.58% |
Performance for Q3 2026
-0.3%
Performance Last 4 Quarters
-0.6%
| Period | Holdings | Total value | Stability | Top holdings |
|---|---|---|---|---|
| 2026-03-31 | 6 | $468.9M | 61 | |
| 2025-12-31 | 7 | $809.8M | 100 | |
| 2024-09-30 | 5 | $43.6M | 0 | |
| 2024-06-30 | 4 | $20.5M | 0 | |
| 2024-03-31 | 5 | $57.1M | 0 | |
| 2023-12-31 | 2 | $28.0M | 0 | |
| 2023-09-30 | 2 | $10.8M | 0 | |
| 2023-06-30 | 7 | $109.9M | 0 | |
| 2023-03-31 | 6 | $128.3M | 0 | |
| 2022-12-31 | 5 | $140.5M | 0 | |
| 2022-09-30 | 3 | $192.3M | 0 | |
| 2022-06-30 | 3 | $213.8M | 0 | |
| 2022-03-31 | 5 | $235.1M | 0 | |
| 2021-12-31 | 7 | $282.0M | 0 | |
| 2021-09-30 | 7 | $370.6M | 0 | |
| 2021-06-30 | 9 | $409.9M | 100 | |
| 2021-03-31 | 3 | $639.4K | 30 | |
| 2020-12-31 | 3 | $472.8K | 100 | |
| 2020-09-30 | 2 | $126.2K | 97 | |
| 2019-12-31 | 3 | $290.1K | 47 | |
| 2019-09-30 | 3 | $436.3K | 100 | |
| 2019-06-30 | 1 | $152.7K | 6 | |
| 2019-03-31 | 1 | $162.3K | 12 | |
| 2018-12-31 | 1 | $143.5K | 100 | |
| 2017-12-31 | 1 | $30.6K | 100 | |
| 2017-09-30 | 1 | $71.7K | 0 | |
| 2017-06-30 | 1 | $71.6K | 84 | |
| 2017-03-31 | 1 | $175.6K | 0 | |
| 2016-12-31 | 1 | $174.9K | 27 | |
| 2016-09-30 | 1 | $228.9K | 100 | |
| 2016-06-30 | 1 | — | 100 | |
| 2016-03-31 | 1 | $23.9K | 100 | |
| 2015-12-31 | 1 | — | — |
Mass General Brigham, Inc's most significant position changes for 2026-03-31: Sold out: Rubrik Inc-a (RBRK); Trim: Ishares Msci Acwi ETF (ACWI) — shares -53.33%; Add: Medline Inc-cl A (MDLN) — shares +167.58%.
| # | Ticker | Issuer | Weight Change | Shares Change | Action |
|---|---|---|---|---|---|
| 1 | KRMN | Karman Holdings INC | +12.6% | — | Unchanged |
| 2 | RVMD | Revolution Medicines INC | +3.8% | — | Unchanged |
| 3 | TNGX | Tango Therapeutics INC | +1.2% | — | Unchanged |
| 4 | MDLN | Medline Inc-cl A | +0.5% | +167.58% | Add |
| 5 | MAZE | Maze Therapeutics INC | +0.3% | — | Unchanged |
| 6 | ACWI | Ishares Msci Acwi ETF | -18.2% | -53.33% | Trim |
| 7 | RBRK | Rubrik Inc-a | — | EXIT | Sold out |
| Period | Filed | Type | EDGAR |
|---|---|---|---|
| 2026-03-31 | 2026-05-05 | 13F-HR | View on EDGAR |
| 2025-12-31 | 2026-01-27 | 13F-HR | View on EDGAR |
| 2024-09-30 | 2024-10-16 | 13F-HR | View on EDGAR |
| 2024-06-30 | 2024-07-31 | 13F-HR | View on EDGAR |
| 2024-03-31 | 2024-04-04 | 13F-HR | View on EDGAR |
| 2023-12-31 | 2024-01-24 | 13F-HR | View on EDGAR |
| 2023-09-30 | 2023-10-23 | 13F-HR | View on EDGAR |
| 2023-06-30 | 2023-07-21 | 13F-HR | View on EDGAR |
| 2023-03-31 | 2023-04-05 | 13F-HR | View on EDGAR |
| 2022-12-31 | 2023-01-19 | 13F-HR | View on EDGAR |
| 2022-09-30 | 2022-10-19 | 13F-HR | View on EDGAR |
| 2022-06-30 | 2022-07-27 | 13F-HR | View on EDGAR |
| 2022-03-31 | 2022-04-15 | 13F-HR | View on EDGAR |
| 2021-12-31 | 2022-01-19 | 13F-HR | View on EDGAR |
| 2021-09-30 | 2021-10-08 | 13F-HR | View on EDGAR |
| 2021-06-30 | 2021-07-19 | 13F-HR | View on EDGAR |
| 2021-03-31 | 2021-04-12 | 13F-HR | View on EDGAR |
| 2020-12-31 | 2021-02-08 | 13F-HR | View on EDGAR |
| 2020-09-30 | 2020-10-23 | 13F-HR | View on EDGAR |
| 2019-12-31 | 2020-01-15 | 13F-HR | View on EDGAR |
| 2019-09-30 | 2019-10-30 | 13F-HR | View on EDGAR |
| 2019-06-30 | 2019-07-29 | 13F-HR | View on EDGAR |
| 2019-03-31 | 2019-04-18 | 13F-HR | View on EDGAR |
| 2018-12-31 | 2019-01-30 | 13F-HR | View on EDGAR |
| 2017-12-31 | 2018-01-24 | 13F-HR | View on EDGAR |
| 2017-09-30 | 2018-01-24 | 13F-HR | View on EDGAR |
| 2017-06-30 | 2017-08-24 | 13F-HR | View on EDGAR |
| 2017-03-31 | 2017-05-04 | 13F-HR | View on EDGAR |
| 2016-12-31 | 2017-02-01 | 13F-HR | View on EDGAR |
| 2016-09-30 | 2016-10-27 | 13F-HR | View on EDGAR |
| 2016-06-30 | 2016-08-17 | 13F-HR | View on EDGAR |
| 2016-03-31 | 2016-08-17 | 13F-HR | View on EDGAR |
| 2015-12-31 | 2016-08-04 | 13F-HR | View on EDGAR |
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