Who owns MRX
Which tracked institutional funds hold MRX, how they are positioned, and who is buying versus exiting — from SEC Form 13F-HR filings. See MRX company fundamentals →
Ownership as of the 2026-Q2 13F filings (latest filed 2026-09-22). 13F is disclosed up to 45 days after quarter-end, so the most recent quarter fills in over the following weeks.
How the tape is positioned
97 tracked funds added or opened MRX while 50 trimmed or exited it between 2026-Q1 and 2026-Q2 — the tape is split. When large holders disagree on a name, the funds moving first are sometimes ahead of the story.
A prompt to read the filings, not a verdict. 13F is a quarter-end snapshot disclosed up to 45 days late; a fund adds or exits for mandate, benchmark, and timing reasons that have nothing to do with a view on the stock. This is a starting question, not a signal to trade.
Conviction spread
MRX’s largest tracked holder by dollar value, FMR LLC, sizes it at 0.0% of its own reported 13F book, while the median holder sizes it at 0.0% of theirs — a 0.0pp gap the other way — the median holder sizes MRX more heavily than its largest holder by dollar value does.
Book-share is each fund’s reported value in MRX divided by its whole reported 13F book, so it is comparable across funds of different sizes and is unaffected by stock splits. A higher share means a fund has committed more of its book to the name — a starting question about conviction, not a verdict or a signal to trade.
Institutional & insider positioning
Between 2026-Q1 and 2026-Q2, across 205 tracked filers holding MRX, 137 increased or opened the position and 100 reduced or closed it; over the same quarter, open-market insider Form 4s were net sales.
This fuses two public signals for the same quarter — how tracked institutions changed their positions and whether insiders bought or sold in the open market. It describes what was filed; it is a starting question, not a verdict or a signal to trade.
New buyers & exits
Funds opening or closing a position in MRX between the 2026-Q1 and 2026-Q2 13F filings, and the largest changes among funds holding it in both. New buyers and exits are counted on fund presence (split-invariant); adds and trims are measured on reported value.
New buyers 16
- WESTFIELD CAPITAL MANAGEMENT CO LP$42M
- TUDOR INVESTMENT CORP ET AL$23M
- MML INVESTORS SERVICES, LLC$16M
- TimesSquare Capital Management, LLC$13M
- ARGENT CAPITAL MANAGEMENT LLC$3M
- Uniplan Investment Counsel, Inc.$3M
Full exits 31
- Grandeur Peak Global Advisors, LLC$59M
- Artisan Partners Limited Partnership$54M
- Allspring Global Investments Holdings, LLC$39M
- Deltroit Asset Management (UK) LLP$20M
- SEI INVESTMENTS CO$16M
- T. Rowe Price Investment Management, Inc.$15M
Largest adds
- PRICE T ROWE ASSOCIATES INC /MD/$215M
- FMR LLC$172M
- WASATCH ADVISORS LP$95M
- BlackRock, Inc.$84M
- MORGAN STANLEY$50M
- ALLIANCEBERNSTEIN L.P.$50M
Largest trims
- JENNISON ASSOCIATES LLC$35M
- WESTWOOD HOLDINGS GROUP INC$24M
- BALYASNY ASSET MANAGEMENT L.P.$11M
- WILLIAM BLAIR INVESTMENT MANAGEMENT, LLC$8M
- VOLORIDGE INVESTMENT MANAGEMENT, LLC$8M
- JPMORGAN CHASE & CO$6M
Institutional holders
One row per tracked fund, most shares held first (every row is from one quarter; reported value breaks ties). “% of value” is the fund’s share of this security’s tracked institutional value — not of shares outstanding.
| Fund | Shares | Reported value | % of value | Quarter |
|---|---|---|---|---|
| FMR LLC added | 5,368,485 | $327M | 9.9% | 2026-Q2 |
| PRICE T ROWE ASSOCIATES INC /MD/ added | 4,923,341 | $300M | 9.1% | 2026-Q2 |
| BlackRock, Inc. added | 4,594,149 | $280M | 8.5% | 2026-Q2 |
| Capital International Investors trimmed | 3,264,364 | $199M | 6.0% | 2026-Q2 |
| ALLIANCEBERNSTEIN L.P. added | 2,600,436 | $116M | 3.5% | 2026-Q2 |
| WASATCH ADVISORS LP added | 1,683,061 | $103M | 3.1% | 2026-Q2 |
| LOOMIS SAYLES & CO L P trimmed | 1,626,702 | $99M | 3.0% | 2026-Q2 |
| SAMLYN CAPITAL, LLC trimmed | 1,483,250 | $90M | 2.7% | 2026-Q2 |
| Invesco Ltd. added | 1,404,552 | $86M | 2.6% | 2026-Q2 |
| Ophir Asset Management Pty Ltd added | 1,391,511 | $85M | 2.6% | 2026-Q2 |
| TWO SIGMA INVESTMENTS, LP trimmed | 1,335,436 | $81M | 2.5% | 2026-Q2 |
| VICTORY CAPITAL MANAGEMENT INC trimmed | 1,291,337 | $79M | 2.4% | 2026-Q2 |
| Granahan Investment Management, LLC added | 1,254,283 | $76M | 2.3% | 2026-Q2 |
| MORGAN STANLEY added | 1,169,722 | $71M | 2.2% | 2026-Q2 |
| ROYCE & ASSOCIATES LP trimmed | 1,111,339 | $68M | 2.0% | 2026-Q2 |
| HEALTHCARE OF ONTARIO PENSION PLAN TRUST FUND added | 1,043,286 | $61M | 1.9% | 2026-Q2 |
| STATE STREET CORP added | 1,026,731 | $63M | 1.9% | 2026-Q2 |
| WILLIAM BLAIR INVESTMENT MANAGEMENT, LLC trimmed | 1,009,199 | $62M | 1.9% | 2026-Q2 |
| AMERIPRISE FINANCIAL INC trimmed | 904,162 | $55M | 1.7% | 2026-Q2 |
| GEODE CAPITAL MANAGEMENT, LLC added | 897,253 | $53M | 1.6% | 2026-Q2 |
| WELLINGTON MANAGEMENT GROUP LLP added | 775,023 | $47M | 1.4% | 2026-Q2 |
| WESTFIELD CAPITAL MANAGEMENT CO LP new | 688,665 | $42M | 1.3% | 2026-Q2 |
| JENNISON ASSOCIATES LLC trimmed | 604,393 | $37M | 1.1% | 2026-Q2 |
| VANGUARD PORTFOLIO MANAGEMENT LLC added | 569,895 | $35M | 1.0% | 2026-Q2 |
| GOLDMAN SACHS GROUP INC added | 551,753 | $34M | 1.0% | 2026-Q2 |
| FRANKLIN RESOURCES INC added | 538,128 | $33M | 1.0% | 2026-Q2 |
| Praetorian PR LLC | 500,000 | $30M | 0.9% | 2026-Q2 |
| NEW YORK STATE COMMON RETIREMENT FUND added | 469,510 | $29M | 0.9% | 2026-Q2 |
| FEDERATED HERMES, INC. added | 464,935 | $28M | 0.9% | 2026-Q2 |
| Qube Research & Technologies Ltd trimmed | 449,433 | $27M | 0.8% | 2026-Q2 |
| NORGES BANK added | 429,800 | $26M | 0.8% | 2026-Q2 |
| Nuveen, LLC added | 419,120 | $26M | 0.8% | 2026-Q2 |
| ALGERT GLOBAL LLC added | 411,697 | $25M | 0.8% | 2026-Q2 |
| Walleye Capital LLC added | 408,016 | $25M | 0.8% | 2026-Q2 |
| TUDOR INVESTMENT CORP ET AL added | 372,910 | $23M | 0.7% | 2026-Q2 |
| Bank of New York Mellon Corp trimmed | 367,225 | $22M | 0.7% | 2026-Q2 |
| NORTHERN TRUST CORP added | 354,764 | $22M | 0.7% | 2026-Q2 |
| Swedbank AB added | 354,440 | $22M | 0.7% | 2026-Q2 |
| Russell Investments Group, Ltd. added | 347,067 | $21M | 0.6% | 2026-Q2 |
| GLENMEDE TRUST CO NA trimmed | 295,517 | $18M | 0.5% | 2026-Q2 |
| BANK OF AMERICA CORP /DE/ trimmed | 291,285 | $18M | 0.5% | 2026-Q2 |
| MANUFACTURERS LIFE INSURANCE COMPANY, THE trimmed | 289,033 | $18M | 0.5% | 2026-Q2 |
| THORNBURG INVESTMENT MANAGEMENT INC trimmed | 275,027 | $17M | 0.5% | 2026-Q2 |
| INTRINSIC EDGE CAPITAL MANAGEMENT LLC added | 272,776 | $17M | 0.5% | 2026-Q2 |
| MML INVESTORS SERVICES, LLC added | 262,551 | $16M | 0.5% | 2026-Q2 |
| Alyeska Investment Group, L.P. added | 244,695 | $15M | 0.5% | 2026-Q2 |
| JPMORGAN CHASE & CO trimmed | 242,209 | $14M | 0.4% | 2026-Q2 |
| BNP PARIBAS FINANCIAL MARKETS added | 241,071 | $15M | 0.4% | 2026-Q2 |
| Hudson Bay Capital Management LP added | 228,742 | $14M | 0.4% | 2026-Q2 |
| Creative Planning added | 220,288 | $13M | 0.4% | 2026-Q2 |
| GLOBEFLEX CAPITAL L P | 212,125 | $13M | 0.4% | 2026-Q2 |
| TimesSquare Capital Management, LLC new | 211,722 | $13M | 0.4% | 2026-Q2 |
| RAYMOND JAMES FINANCIAL INC added | 210,293 | $13M | 0.4% | 2026-Q2 |
| RENAISSANCE TECHNOLOGIES LLC added | 180,087 | $11M | 0.3% | 2026-Q2 |
| CHARLES SCHWAB INVESTMENT MANAGEMENT INC added | 171,846 | $10M | 0.3% | 2026-Q2 |
| Legal & General Group Plc added | 158,207 | $10M | 0.3% | 2026-Q2 |
| SUSQUEHANNA FUNDAMENTAL INVESTMENTS, LLC added | 155,555 | $9M | 0.3% | 2026-Q2 |
| PRINCIPAL FINANCIAL GROUP INC added | 154,597 | $9M | 0.3% | 2026-Q2 |
| COMMONWEALTH OF PENNSYLVANIA PUBLIC SCHOOL EMPLS RETRMT SYS added | 135,005 | $8M | 0.2% | 2026-Q2 |
| STATE OF WISCONSIN INVESTMENT BOARD trimmed | 130,828 | $8M | 0.2% | 2026-Q2 |
| UBS Group AG trimmed | 128,477 | $8M | 0.2% | 2026-Q2 |
| Calamos Advisors LLC added | 125,108 | $8M | 0.2% | 2026-Q2 |
| Moody Aldrich Partners LLC trimmed | 109,733 | $7M | 0.2% | 2026-Q2 |
| MOODY NATIONAL BANK TRUST DIVISION added | 91,388 | $6M | 0.2% | 2026-Q2 |
| CITIGROUP INC added | 90,104 | $5M | 0.2% | 2026-Q2 |
| Boston Partners added | 80,278 | $5M | 0.1% | 2026-Q2 |
| Engle Capital Management, L.P. trimmed | 79,037 | $5M | 0.1% | 2026-Q2 |
| RHUMBLINE ADVISERS added | 77,995 | $5M | 0.1% | 2026-Q2 |
| WELLS FARGO & COMPANY/MN added | 77,128 | $5M | 0.1% | 2026-Q2 |
| RENAISSANCE GROUP LLC trimmed | 75,675 | $5M | 0.1% | 2026-Q2 |
| MARSHALL WACE, LLP trimmed | 74,677 | $5M | 0.1% | 2026-Q2 |
| BALYASNY ASSET MANAGEMENT L.P. trimmed | 68,815 | $4M | 0.1% | 2026-Q2 |
| EPACRIA CAPITAL PARTNERS, LLC | 65,400 | $4M | 0.1% | 2026-Q2 |
| DEUTSCHE BANK AG\ added | 64,890 | $4M | 0.1% | 2026-Q2 |
| Mariner, LLC added | 62,216 | $4M | 0.1% | 2026-Q2 |
| PRUDENTIAL FINANCIAL INC added | 61,420 | $4M | 0.1% | 2026-Q2 |
| Squarepoint Ops LLC trimmed | 56,688 | $3M | 0.1% | 2026-Q2 |
| Trexquant Investment LP added | 55,286 | $3M | 0.1% | 2026-Q2 |
| Quantinno Capital Management LP added | 53,603 | $3M | 0.1% | 2026-Q2 |
| ARGENT CAPITAL MANAGEMENT LLC new | 50,858 | $3M | 0.1% | 2026-Q2 |
| VANGUARD FIDUCIARY TRUST CO added | 50,292 | $3M | 0.1% | 2026-Q2 |
| Uniplan Investment Counsel, Inc. new | 45,412 | $3M | 0.1% | 2026-Q2 |
| AQR CAPITAL MANAGEMENT LLC added | 40,329 | $2M | 0.1% | 2026-Q2 |
| MetLife Investment Management, LLC added | 36,337 | $2M | 0.1% | 2026-Q2 |
| Orion Porfolio Solutions, LLC added | 31,744 | $2M | 0.1% | 2026-Q2 |
| VOLORIDGE INVESTMENT MANAGEMENT, LLC trimmed | 30,567 | $2M | 0.1% | 2026-Q2 |
| MIRAE ASSET GLOBAL ETFS HOLDINGS Ltd. added | 28,673 | $2M | 0.1% | 2026-Q2 |
| Sidoxia Capital Management, LLC added | 27,155 | $2M | 0.0% | 2026-Q2 |
| Y-Intercept (Hong Kong) Ltd added | 26,909 | $2M | 0.0% | 2026-Q2 |
| Massar Capital Management, LP trimmed | 25,991 | $2M | 0.0% | 2026-Q2 |
| Jain Global LLC added | 25,298 | $2M | 0.0% | 2026-Q2 |
| ROYAL BANK OF CANADA added | 21,303 | $1M | 0.0% | 2026-Q2 |
| Militia Capital Management LLC trimmed | 20,000 | $1M | 0.0% | 2026-Q2 |
| Police & Firemen's Retirement System of New Jersey added | 18,365 | $1M | 0.0% | 2026-Q2 |
| Aquatic Capital Management LLC trimmed | 17,662 | $1M | 0.0% | 2026-Q2 |
| Genesee Capital Advisors, LLC new | 17,623 | $1M | 0.0% | 2026-Q2 |
| TOTH FINANCIAL ADVISORY CORP new | 17,000 | $1M | 0.0% | 2026-Q2 |
| CIBC WORLD MARKET INC. trimmed | 14,881 | $907K | 0.0% | 2026-Q2 |
| FORMULA GROWTH LTD new | 13,700 | $835K | 0.0% | 2026-Q2 |
Ownership over time
Tracked institutional holder count and total shares held by filing quarter (independent scales). The curated-era tail and any mid-ingest latest quarter are handled honestly — a partial quarter is not drawn as a collapse.
Reading this table
Funds hold the same stock for different reasons — an index fund “holds” almost everything, an active manager sizes a name to a mandate and a benchmark, and each fund entered at its own price and time. Because 13F is filed up to 45 days after quarter-end, every row is a backward-looking snapshot; a manager may have traded since. Share-class siblings (a company’s A and C shares) are rolled up to one line so a dual-class name is never double-counted. Compare like-for-like. A large holder is not an endorsement, and a fund exiting is not a warning — this is a starting question, not a verdict.
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 covers long US-listed equities only — not short positions, options, cash, or private holdings — and the funds shown are the large sample we track, not the complete 13F universe.