MG
Mass General Brigham, Inc 13F Holdings & Position Changes (Q2 2026)
Mass General Brigham, IncCIK: 0001678378
Concentrated strategySector-focusedQuality / disciplined sizing
Total reported value
$361.1M
Reporting period: 2026-06-30 · Number of holdings: 6
Mass General Brigham, Inc disclosed 6 holdings in its latest 13F filing for the period ending 2026-06-30, with total reported value of $361.1M and a quarterly turnover rate of 42.7%.
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Personality snowflake
- Concentration
- 100
- Portfolio Stability
- 42.68
- Momentum
- 50
- Sector conviction
- 100
- Diversification
- 12
- Sizing Uniformity
- 87.61
Mass General Brigham, Inc's disclosed holdings carry a Herfindahl concentration index of 0.380 — mathematically equivalent to about 3 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 1.24), 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 39% 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.
Source and citation information
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Recent moves
View source Form 13F filing on SEC.govAdd RVMD
0.0% $31.0M
Trim ACWI
-41.5% -$95.0M
Trim KRMN
0.0% -$47.1M
Add TNGX
0.0% $3.7M
Add MAZE
0.0% -$2.4K
Add MDLN
-2.8% -$432.7K
Holdings Map
New buyAddUnchangedTrim
Top 10 holdings by weight
Full holdings list this quarter
| # | Ticker | Issuer | Asset Subclass | Weight | Weight Change | Shares Change | 4Q Trend |
|---|---|---|---|---|---|---|---|
| 1 | ACWI | Ishares Msci Acwi ETF | ETF-Other | 54.76% | -7.66% | -41.51% | |
| 2 | KRMN | Karman Holdings Inc | Stock-Industrials | 21.60% | -5.07% | — | |
| 3 | RVMD | Revolution Medicines Inc | Stock-Healthcare | 17.85% | +10.71% | — | |
| 4 | TNGX | Tango Therapeutics Inc | Stock-Other | 3.07% | +1.49% | — | |
| 5 | MAZE | Maze Therapeutics Inc | Stock-Other | 1.98% | +0.45% | — | |
| 6 | MDLN | Medline Inc-cl A | Stock-Other | 0.75% | +0.08% | -2.76% |
Portfolio Performance
Performance for Q3 2026
+1.4%
Performance Last 4 Quarters
+67.4%
- Stdev
- +54.4%
- Beta
- +2.03
- Alpha
- -4.2%
- Max Drawdown
- -46.7%
- Annualized Perf
- +25.8%
- Batting Avg vs S&P
- +47.2%
- Sortino
- +1.3
- Stutzer
- +0.2
- Treynor
- +0.18
- Sterling
- +0.76
- Calmar
- +0.55
- Information Ratio
- +0.33
- Tracking Error
- +49.5%
- Stdev Down
- +28%
- Winning Months %
- +55.6%
- Losing Months %
- +44.4%
- Best 12 Months
- +84.6%
- Worst 12 Months
- -46.7%
- Efficiency Ratio
- +0.25
- Sharpe
- +0.67
- Stdev Sectors
- +4.8%
- Skewness
- +1.01
- Kurtosis
- +2.41
- Upside Potential
- +3.03
Reported value over time
Sector allocation
Sector allocation over time
Quarterly history
| Period | Holdings | Total value | Stability | Top holdings | |
|---|---|---|---|---|---|
| 2026 Q2 | 6 | $361.1M | 43 | ||
| 2026 Q1 | 6 | $468.9M | 61 | ||
| 2025 Q4 | 7 | $809.8M | 100 | ||
| 2024 Q3 | 5 | $43.6M | 0 | ||
| 2024 Q2 | 4 | $20.5M | 0 | ||
| 2024 Q1 | 5 | $57.1M | 0 | ||
| 2023 Q4 | 2 | $28.0M | 0 | ||
| 2023 Q3 | 2 | $10.8M | 0 | ||
| 2023 Q2 | 7 | $109.9M | 0 | ||
| 2023 Q1 | 6 | $128.3M | 0 | ||
| 2022 Q4 | 5 | $140.5M | 0 | ||
| 2022 Q3 | 3 | $192.3M | 0 | ||
| 2022 Q2 | 3 | $213.8M | 0 | ||
| 2022 Q1 | 5 | $235.1M | 0 | ||
| 2021 Q4 | 7 | $282.0M | 0 | ||
| 2021 Q3 | 7 | $370.6M | 0 | ||
| 2021 Q2 | 9 | $409.9M | 100 | ||
| 2021 Q1 | 3 | $639.4K | 30 | ||
| 2020 Q4 | 3 | $472.8K | 100 | ||
| 2020 Q3 | 2 | $126.2K | 97 | ||
| 2019 Q4 | 3 | $290.1K | 47 | ||
| 2019 Q3 | 3 | $436.3K | 100 | ||
| 2019 Q2 | 1 | $152.7K | 6 | ||
| 2019 Q1 | 1 | $162.3K | 12 | ||
| 2018 Q4 | 1 | $143.5K | 100 | ||
| 2017 Q4 | 1 | $30.6K | 100 | ||
| 2017 Q3 | 1 | $71.7K | 0 | ||
| 2017 Q2 | 1 | $71.6K | 84 | ||
| 2017 Q1 | 1 | $175.6K | 0 | ||
| 2016 Q4 | 1 | $174.9K | 27 | ||
| 2016 Q3 | 1 | $228.9K | 100 | ||
| 2016 Q2 | 1 | — | 100 | ||
| 2016 Q1 | 1 | $23.9K | 100 | ||
| 2015 Q4 | 1 | — | — |
Holding changes this quarter
Mass General Brigham, Inc's most significant position changes for 2026-06-30: Trim: Ishares Msci Acwi ETF (ACWI) — shares -41.51%; Trim: Medline Inc-cl A (MDLN) — shares -2.76%.
| # | Ticker | Issuer | Weight Change | Shares Change | Action |
|---|---|---|---|---|---|
| 1 | RVMD | Revolution Medicines Inc | +10.7% | — | Unchanged |
| 2 | TNGX | Tango Therapeutics Inc | +1.5% | — | Unchanged |
| 3 | MAZE | Maze Therapeutics Inc | +0.5% | — | Unchanged |
| 4 | MDLN | Medline Inc-cl A | +0.1% | -2.76% | Trim |
| 5 | KRMN | Karman Holdings Inc | -5.1% | — | Unchanged |
| 6 | ACWI | Ishares Msci Acwi ETF | -7.7% | -41.51% | Trim |
Filing History
FAQ
What is Mass General Brigham, Inc and what type of investor is it?
Mass General Brigham, Inc is an investment manager that files SEC Form 13F quarterly, disclosing its U.S. public equity holdings to regulators. As of the most recent reporting period (2026-06-30), the firm manages a tracked equity portfolio valued at approximately $361.1M, spread across 6 disclosed positions.
What are Mass General Brigham, Inc's largest equity positions?
Based on the latest 13F filing, Mass General Brigham, Inc's top holdings by market value are:
1. Ishares Msci Acwi ETF (ACWI) — $197.7M (54.8%)
2. Karman Holdings Inc (KRMN) — $78.0M (21.6%)
3. Revolution Medicines Inc (RVMD) — $64.4M (17.9%)
4. Tango Therapeutics Inc (TNGX) — $11.1M (3.1%)
5. Maze Therapeutics Inc (MAZE) — $7.2M (2.0%)
What changes did Mass General Brigham, Inc make in its most recent portfolio filing?
In the latest quarter, Mass General Brigham, Inc took a more defensive posture — trimming 2 positions and completely exiting 0 holdings. The largest of these moves: Trim: Ishares Msci Acwi ETF (ACWI) — shares -41.51%; Trim: Medline Inc-cl A (MDLN) — shares -2.76%
What sectors does Mass General Brigham, Inc focus on?
Mass General Brigham, Inc is concentrated in the following sectors based on its current disclosed equity portfolio:
• Industrials: 54.8%
• Health Care: 45.3%
Investment Profile
Mass General Brigham, Inc returned an annualized 25.8% over the trailing 36 months — underperforming the S&P 500 by 4.2 points — based on a reconstructed track record of its disclosed 13F positions, with a beta of 2.03 (more volatile than the market) and a 47% quarterly batting average against the index.
Its portfolio is concentrated and moderately active, with 54.8% of the portfolio concentrated in Industrials.
Its turnover score has risen from 0 to 43 over the past 4 quarters — a shift toward more active trading.
It has added to its RVMD position over the past two quarters (+$37.0M, now $64.4M), while trimming ACWI over the same stretch (-$455.1M, still holding $197.7M).
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