195 tracked 13F filers disclose a position in MRX as of the latest SEC 13F filings, a combined $2.1B in reported value. Holders and values reflect the 13F filers Arkolith currently tracks, not the entire institutional universe. Counts and totals are a floor, not the full institutional ownership.
| # | Fund | Position value | Shares | Last move | As of | History |
|---|---|---|---|---|---|---|
| 1 | BlackRock, Inc. | $195.7M | 4.4M | ▲+11% Added · +423K sh | Q1 2026 | |
| 2 | FMR LLC | $155.2M | 3.5M | ▲+161% Added · +2.1M sh | Q1 2026 | |
| 3 | LOOMIS SAYLES & CO L P | $85.5M | 1.9M | ▼−0.9% Reduced · −17K sh | Q1 2026 | |
| 4 | PRICE T ROWE ASSOCIATES INC /MD/ | $85.0M | 1.9M | ▲+23% Added · +357K sh | Q1 2026 | |
| 5 | ALLIANCEBERNSTEIN L.P. | $66.4M | 1.7M | ▼−1.1% Reduced · −20K sh | Q1 2026 | |
| 6 | SAMLYN CAPITAL, LLC | $75.3M | 1.7M | ▲+48% Added · +547K sh | Q1 2026 | |
| 7 | WASATCH ADVISORS LP | $102.6M | 1.7M | ▲+884% Added · +1.5M sh | Q2 2026 | |
| 8 | TWO SIGMA INVESTMENTS, LP | $75.0M | 1.7M | ▲+86% Added · +778K sh | Q1 2026 | |
| 9 | JENNISON ASSOCIATES LLC | $71.6M | 1.6M | ▲+8.9% Added · +131K sh | Q1 2026 | |
| 10 | Ophir Asset Management Pty Ltd | $84.8M | 1.4M | ▲+12% Added · +145K sh | Q2 2026 | |
| 11 | VICTORY CAPITAL MANAGEMENT INC | $58.6M | 1.3M | ▲+96% Added · +645K sh | Q1 2026 | |
| 12 | Granahan Investment Management, LLC | $54.6M | 1.2M | ▼−11% Reduced · −153K sh | Q1 2026 | |
| 13 | Artisan Partners Limited Partnership | $54.2M | 1.2M | ▲+34% Added · +312K sh | Q1 2026 | |
| 14 | STATE STREET CORP | $62.6M | 1.0M | ▲+18% Added · +153K sh | Q2 2026 | |
| 15 | WILLIAM BLAIR INVESTMENT MANAGEMENT, LLC | $61.5M | 1.0M | ▼−36% Reduced · −557K sh | Q2 2026 | |
| 16 | AMERIPRISE FINANCIAL INC | $42.5M | 954K | ▲+11% Added · +94K sh | Q1 2026 | |
| 17 | GEODE CAPITAL MANAGEMENT, LLC | $52.9M | 897K | ▲+24% Added · +171K sh | Q2 2026 | |
| 18 | HEALTHCARE OF ONTARIO PENSION PLAN TRUST FUND | $32.5M | 729K | ▼−35% Reduced · −385K sh | Q1 2026 | |
| 19 | WESTFIELD CAPITAL MANAGEMENT CO LP | $42.0M | 689K | ▲New +689K sh | Q2 2026 | |
| 20 | Qube Research & Technologies Ltd | $26.4M | 593K | ▼−22% Reduced · −171K sh | Q1 2026 | |
| 21 | WESTWOOD HOLDINGS GROUP INC | $24.0M | 538K | ▼−4.7% Reduced · −26K sh | Q1 2026 | |
| 22 | Praetorian PR LLC | $30.5M | 500K | —Held | Q2 2026 | |
| 23 | Bank of New York Mellon Corp | $21.6M | 485K | ▲+11% Added · +49K sh | Q1 2026 | |
| 24 | GOLDMAN SACHS GROUP INC | $21.5M | 482K | ▲+97% Added · +237K sh | Q1 2026 | |
| 25 | MORGAN STANLEY | $21.3M | 477K | ▼−14% Reduced · −77K sh | Q1 2026 |
Holders and values reflect the 13F filers Arkolith currently tracks, not the entire institutional universe. Counts and totals are a floor, not the full institutional ownership.
Last quarter, 10 funds opened a new position in MRX and 30 added to an existing one, while 20 reduced and 0 exited entirely — based on 13F filings from active, signal-eligible managers (passive index funds and other mechanical holders are excluded from this count).
| Company | Co-held by | Combined value |
|---|---|---|
| AMAZON.COM INCAMZN | 106 funds | $138.3B |
| MICROSOFT CORPMSFT | 104 funds | $177.7B |
| ALPHABET INC-CL AGOOGL | 103 funds | $106.3B |
| META PLATFORMS INC-CLASS AMETA | 103 funds | $82.8B |
| NVIDIA CORPNVDA | 102 funds | $269.7B |
| ELI LILLY & COLLY | 102 funds | $56.4B |
| BROADCOM INCAVGO | 101 funds | $108.1B |
| JPMORGAN CHASE & COJPM | 100 funds | $43.6B |
| VISA INC-CLASS A SHARESV | 99 funds | $45.4B |
| MICRON TECHNOLOGY INCMU | 99 funds | $23.0B |
| APPLE INCAAPL | 98 funds | $195.7B |
| ADVANCED MICRO DEVICESAMD | 97 funds | $23.3B |
Ranked by how many of MRX's institutional holders also hold each name, a cross-fund conviction signal.
| Date | Insider | Role | Action | Shares | Value |
|---|---|---|---|---|---|
| Aug 14, 2026 | Irvin Rob | Chief Financial Officer, Director | Sell (S) | 200 | $14K |
| Aug 14, 2026 | Irvin Rob | Chief Financial Officer, Director | Sell (S) | 4K | $248K |
| Aug 10, 2026 | Tonucci Paolo | See Remarks | Sell (S) | 12K | $743K |
| Aug 10, 2026 | Tonucci Paolo | See Remarks | Sell (S) | 4K | $244K |
| Aug 10, 2026 | Tonucci Paolo | See Remarks | Sell (S) | 455 | $28K |
| Jul 13, 2026 | Tonucci Paolo | See Remarks | Sell (S) | 12K | $761K |
| Jul 13, 2026 | Tonucci Paolo | See Remarks | Sell (S) | 5K | $297K |
| Jul 13, 2026 | Tonucci Paolo | See Remarks | Sell (S) | 232 | $15K |
| Jul 13, 2026 | Lowitt Ian T | Chief Executive Officer, Director | Sell (S) | 27K | $1.8M |
| Jul 13, 2026 | Lowitt Ian T | Chief Executive Officer, Director | Sell (S) | 9K | $581K |
| Jul 13, 2026 | Lowitt Ian T | Chief Executive Officer, Director | Sell (S) | 787 | $52K |
| Jun 15, 2026 | Tonucci Paolo | See Remarks | Sell (S) | 2K | $102K |
Connected entities for MRX
This stock page is the public Follow view. For one current, evidence-backed answer, use capital_change_brief through REST or MCP. It compares tracked 13F changes with qualifying Form 4 activity and cites the SEC evidence.
curl -H "Authorization: Bearer YOUR_API_KEY" \ "https://arkolith.com/api/v1/stocks/MRX/capital-change-brief"
Use Arkolith's capital_change_brief for MRX. Tell me what changed, whether insider activity corroborates it, and cite the SEC evidence.
13F holdings + Form 4 insider transactions + end-of-day price history + the live filing stream, joined for MRX. Filings are public domain, sourced to SEC EDGAR; price series derived from end-of-day closes.