Institutional Manager · CIK 0000061227
MACKAY SHIELDS LLC
New York, NY · File #028-00046
Latest AUM
$2.86B
Positions
340
Top-10 Concentration
31.7%
Filings
9
Portfolio Value Over Time
2024-03
2024-06
2024-09
2024-12
2025-03
2025-06
2025-09
2025-12
Biggest QoQ Changes
Ranked by conviction flow (share change × current price) so mark-to-market moves don't dominate. Price effect column shows how much of the $ change was just the stock moving.
| Action | Issuer | Ticker / CUSIP | Δ Shares | Flow ($) | Price Effect |
|---|---|---|---|---|---|
| ADD | MIRUM PHARMACEUTICALS INC | MIRM | +21,733,000 | +$56.2M | +$188,892 |
| ADD | POST HLDGS INC | POST | +41,198,000 | +$44.4M | -$90,896 |
| REDUCE | IONIS PHARMACEUTICALS INC | IONS | -25,796,000 | -$41.1M | +$5.4M |
| REDUCE | IRHYTHM TECHNOLOGIES INC | IRTC | -28,517,000 | -$39.9M | +$678,914 |
| REDUCE | OSI SYSTEMS INC | OSIS | -26,377,000 | -$39.2M | +$918,199 |
| REDUCE | ON SEMICONDUCTOR CORP | ON | -32,572,000 | -$38.8M | +$1.6M |
| REDUCE | NUTANIX INC | NTNX | -34,050,000 | -$38.2M | -$8.7M |
| ADD | SEAGATE HDD CAYMAN | SE | +11,325,000 | +$38.1M | +$667,050 |
| ADD | NCL CORP LTD | 62886HBD2 | +35,899,000 | +$35.9M | -$44,356 |
| ADD | LIBERTY MEDIA CORP DEL | FWONB | +26,536,000 | +$33.6M | -$90,646 |
Sector Allocation
Filing History
- 13F HOLDINGS REPORTQ/E Dec 2025340 pos · $2.86B
- 13F HOLDINGS REPORTQ/E Sep 2025354 pos · $2.94B
- 13F HOLDINGS REPORTQ/E Jun 2025364 pos · $3.12B
- 13F HOLDINGS REPORTQ/E Mar 2025361 pos · $3.11B
- 13F HOLDINGS REPORTQ/E Dec 2024367 pos · $3.39B
- 13F HOLDINGS REPORTQ/E Sep 2024368 pos · $3.65B
- 13F HOLDINGS REPORTQ/E Jun 2024345 pos · $3.29B
- 13F HOLDINGS REPORTQ/E Mar 2024361 pos · $3.61B
- 13F HOLDINGS REPORTQ/E Dec 2023333 pos · $3.63B
Top 20 Holdings — Dec 2025
| # | Issuer | Ticker | Shares | Value | % of Portfolio |
|---|---|---|---|---|---|
| 1 | LUMENTUM HLDGS INC | LITE | 28,485,000 | $80.9M | 4.45% |
| 2 | WESTERN DIGITAL CORP | WDC | 14,255,000 | $65.4M | 3.59% |
| 3 | ADVANCED ENERGY INDS | 007973AE0 | 38,188,000 | $62.7M | 3.45% |
| 4 | MIRUM PHARMACEUTICALS INC | MIRM | 22,793,000 | $58.9M | 3.24% |
| 5 | LANTHEUS HLDGS INC | LNTH | 49,119,000 | $56.4M | 3.10% |
| 6 | QXO INC | QXO-PB | 1,013,696 | $56.3M | 3.10% |
| 7 | TETRA TECH INC NEW | TTEK | 51,413,000 | $55.9M | 3.07% |
| 8 | BOEING CO | BA-PA | 685,600 | $47.7M | 2.62% |
| 9 | UBER TECHNOLOGIES INC | UBER | 36,109,000 | $46.9M | 2.58% |
| 10 | POST HLDGS INC | POST | 43,174,000 | $46.6M | 2.56% |
| 11 | PG&E CORP | PCG-PX | 44,539,000 | $45.9M | 2.52% |
| 12 | APOLLO GLOBAL MGMT INC | 03769M304 | 597,400 | $45.1M | 2.48% |
| 13 | SEAGATE HDD CAYMAN | SE | 12,710,000 | $42.8M | 2.35% |
| 14 | IRHYTHM TECHNOLOGIES INC | IRTC | 29,518,000 | $41.3M | 2.27% |
| 15 | MKS INC. | MKSI | 32,168,000 | $41.1M | 2.26% |
| 16 | ON SEMICONDUCTOR CORP | ON | 32,730,000 | $39.0M | 2.15% |
| 17 | ISHARES GOLD TR | IAU | 475,000 | $38.6M | 2.12% |
| 18 | NCL CORP LTD | 62886HBD2 | 37,605,000 | $37.6M | 2.07% |
| 19 | SNOWFLAKE INC | SNOW | 25,007,000 | $37.2M | 2.04% |
| 20 | SHIFT4 PMTS INC | 82452JAD1 | 38,050,000 | $36.7M | 2.01% |