Palo Alto Investors LP
In its 13F for Q1 2026 (holdings as of March 31, 2026, filed May 15, 2026), Palo Alto Investors LP reported 51 stock positions worth $653.9 million. Its top holding was Insmed (INSM) at 10.4% of the portfolio, followed by Acadia Pharmaceuticals (ACAD, 9.8%) and PTC Therapeutics (PTCT, 9.6%). Compared with Q4 2025, it opened 5 new positions, sold out of 3, added to 17 and reduced 17. The biggest buy was Mirum Pharmaceuticals (MIRM, shares +108%) and the biggest sale Amicus Therapeutics (FOLD, shares −79%).
- Most Recent 13F
- Q2 2026
- Location
- PALO ALTO, CA
- CIK
- 0001306923
- Portfolio Value
- $653.9M (Q1 2026)
- SEC Filing
- 0001306923-26-000004 ↗ filed May 15, 2026
Holdings Value
Holdings 51 stocks · $653.9M
| INSM Insmed Inc. | 10.39% | 415,269 | $67.9M | Reduce -15.2% |
| ACAD Acadia Pharmaceuticals Inc. | 9.78% | 2,872,695 | $63.9M | Add +15.7% |
| PTCT PTC Therapeutics Inc. | 9.60% | 921,607 | $62.8M | Add +2.0% |
| BMRN Biomarin Pharmaceutical Inc. | 5.92% | 685,182 | $38.7M | Reduce -8.2% |
| UTHR United Therapeutics Corp. | 5.70% | 62,809 | $37.2M | Add +8.0% |
| ANAB Anaptysbio Inc. | 5.41% | 638,161 | $35.4M | Reduce -7.5% |
| MIRM Mirum Pharmaceuticals Inc. | 4.59% | 325,175 | $30.0M | Add +107.9% |
| DYN Dyne Therapeutics Inc. | 4.58% | 1,652,972 | $30.0M | Add +12.3% |
| BIIB Biogen Inc. | 3.95% | 140,719 | $25.8M | Reduce -23.3% |
| IRON Disc Medicine Inc. | 3.93% | 401,719 | $25.7M | Add +26.5% |
| IOVA Iovance Biotherapeutics Inc. | 3.41% | 6,349,563 | $22.3M | Reduce -10.8% |
| SNDX Syndax Pharmaceuticals Inc. | 3.09% | 864,986 | $20.2M | Add +8.9% |
| ANNX Annexon Inc. | 2.50% | 2,948,090 | $16.3M | Add +23.6% |
| FOLD Amicus Therapeutics Inc. | 2.46% | 1,113,045 | $16.1M | Reduce -78.6% |
| NVCR Novocure Ltd. | 2.13% | 1,280,439 | $14.0M | Reduce -1.4% |
| RARE Ultragenyx Pharmaceutical Inc. | 1.91% | 596,495 | $12.5M | Add +29.3% |
| PRTA Prothena Corp. PLC | 1.80% | 1,208,568 | $11.7M | Reduce -8.5% |
| BCAX Bicara Therapeutics Inc. | 1.67% | 550,408 | $10.9M | Add +84.3% |
| CLDX Celldex Therapeutics Inc. | 1.44% | 296,408 | $9.4M | New |
| CDNA Caredx Inc. | 1.41% | 531,870 | $9.2M | Add +11.2% |
| ALKS Alkermes PLC | 1.31% | 242,560 | $8.6M | No change |
| CMPX Compass Therapeutics Inc. | 1.23% | 1,514,504 | $8.0M | Reduce -40.2% |
| AGIO Agios Pharmaceuticals Inc. | 1.11% | 213,601 | $7.2M | Add +0.5% |
| ALGN Align Technology Inc. | 1.09% | 41,520 | $7.1M | No change |
| CAPR Capricor Therapeutics Inc. | 1.07% | 229,763 | $7.0M | Add +1.5% |
| TVTX Travere Therapeutics Inc. | 1.05% | 230,453 | $6.8M | Add +108.1% |
| TSHA Taysha Gene Therapies Inc. | 0.95% | 1,391,382 | $6.2M | Add +17.6% |
| ACRS Aclaris Therapeutics Inc. | 0.93% | 1,613,430 | $6.1M | Add +3.0% |
| DNLI Denali Therapeutics Inc. | 0.69% | 234,582 | $4.5M | Reduce -63.4% |
| XENE Xenon Pharmaceuticals Inc. | 0.46% | 51,345 | $3.0M | Reduce -46.8% |
| ORKA Oruka Therapeutics Inc. | 0.45% | 59,985 | $2.9M | No change |
| STOK Stoke Therapeutics Inc. | 0.42% | 84,631 | $2.8M | Add +17.5% |
| EW Edwards Lifesciences Corp. | 0.41% | 33,640 | $2.7M | No change |
| NBIX Neurocrine Biosciences Inc. | 0.36% | 18,117 | $2.4M | No change |
| NUVB Nuvation Bio Inc. | 0.33% | 508,846 | $2.2M | Reduce -5.4% |
| CYTK Cytokinetics Inc. | 0.32% | 32,195 | $2.1M | New |
| EHTH Ehealth Inc. | 0.29% | 1,482,797 | $1.9M | Reduce -3.2% |
| CRSP Crispr Therapeutics AG | 0.29% | 39,605 | $1.9M | Reduce -3.9% |
| BNTX Biontech SE-ADR | 0.27% | 19,614 | $1.7M | No change |
| PYXS Pyxis Oncology Inc. | 0.23% | 1,010,510 | $1.5M | Reduce -2.6% |
| VSTM Verastem Inc. | 0.20% | 246,093 | $1.3M | New |
| BCYC Bicycle Therapeutics PLC-ADR | 0.14% | 201,890 | $937K | Reduce -8.7% |
| MDGL Madrigal Pharmaceuticals Inc. | 0.14% | 1,787 | $935K | New |
| HUM Humana Inc. | 0.11% | 3,985 | $691K | No change |
| CMPS Compass Pathways PLC | 0.10% | 115,616 | $639K | No change |
| XERS Xeris Biopharma Holdings Inc. | 0.09% | 104,410 | $606K | New |
| ABEO Abeona Therapeutics Inc. | 0.07% | 108,865 | $488K | No change |
| INSP Inspire Medical Systems Inc. | 0.07% | 8,772 | $452K | No change |
| URGN Urogen Pharma Ltd. | 0.07% | 24,500 | $441K | No change |
| PRQR Proqr Therapeutics NV | 0.05% | 188,807 | $306K | No change |
| ALDX Aldeyra Therapeutics Inc. | 0.04% | 155,709 | $263K | Reduce -30.9% |
Portfolio Sells Q4 2025 → Q1 2026
| FOLD Amicus Therapeutics Inc. | Reduce -78.6% | 2.46% | −7.86 |
| GOSS Gossamer Bio Inc. | Sold out | 0.00% | −1.93 |
| INSM Insmed Inc. | Reduce -15.2% | 10.39% | −1.47 |
| DNLI Denali Therapeutics Inc. | Reduce -63.4% | 0.69% | −0.78 |
| EHTH Ehealth Inc. | Reduce -3.2% | 0.29% | −0.69 |
| CMPX Compass Therapeutics Inc. | Reduce -40.2% | 1.23% | −0.67 |
| BIIB Biogen Inc. | Reduce -23.3% | 3.95% | −0.55 |
| NUVB Nuvation Bio Inc. | Reduce -5.4% | 0.33% | −0.34 |
| BMRN Biomarin Pharmaceutical Inc. | Reduce -8.2% | 5.92% | −0.25 |
| NVCR Novocure Ltd. | Reduce -1.4% | 2.13% | −0.20 |
| XENE Xenon Pharmaceuticals Inc. | Reduce -46.8% | 0.46% | −0.15 |
| ALDX Aldeyra Therapeutics Inc. | Reduce -30.9% | 0.04% | −0.12 |
| BCYC Bicycle Therapeutics PLC-ADR | Reduce -8.7% | 0.14% | −0.07 |
| CRSP Crispr Therapeutics AG | Reduce -3.9% | 0.29% | −0.01 |
| GBIO Generation Bio Co. | Sold out | 0.00% | −0.01 |
| AKTX Akari Therapeutics PLC | Sold out | 0.00% | −0.01 |
| PRTA Prothena Corp. PLC | Reduce -8.5% | 1.80% | +0.04 |
| PYXS Pyxis Oncology Inc. | Reduce -2.6% | 0.23% | +0.06 |
| IOVA Iovance Biotherapeutics Inc. | Reduce -10.8% | 3.41% | +0.70 |
| ANAB Anaptysbio Inc. | Reduce -7.5% | 5.41% | +0.76 |
Portfolio Buys Q4 2025 → Q1 2026
| MIRM Mirum Pharmaceuticals Inc. | Add +107.9% | 4.59% | +2.87 |
| UTHR United Therapeutics Corp. | Add +8.0% | 5.70% | +1.75 |
| CLDX Celldex Therapeutics Inc. | New | 1.44% | +1.44 |
| BCAX Bicara Therapeutics Inc. | Add +84.3% | 1.67% | +0.97 |
| ANNX Annexon Inc. | Add +23.6% | 2.50% | +0.83 |
| SNDX Syndax Pharmaceuticals Inc. | Add +8.9% | 3.09% | +0.77 |
| DYN Dyne Therapeutics Inc. | Add +12.3% | 4.58% | +0.57 |
| ACAD Acadia Pharmaceuticals Inc. | Add +15.7% | 9.78% | +0.54 |
| TVTX Travere Therapeutics Inc. | Add +108.1% | 1.05% | +0.46 |
| RARE Ultragenyx Pharmaceutical Inc. | Add +29.3% | 1.91% | +0.43 |
| IRON Disc Medicine Inc. | Add +26.5% | 3.93% | +0.42 |
| CYTK Cytokinetics Inc. | New | 0.32% | +0.32 |
| AGIO Agios Pharmaceuticals Inc. | Add +0.5% | 1.11% | +0.30 |
| ACRS Aclaris Therapeutics Inc. | Add +3.0% | 0.93% | +0.27 |
| VSTM Verastem Inc. | New | 0.20% | +0.20 |
| CAPR Capricor Therapeutics Inc. | Add +1.5% | 1.07% | +0.16 |
| CDNA Caredx Inc. | Add +11.2% | 1.41% | +0.16 |
| MDGL Madrigal Pharmaceuticals Inc. | New | 0.14% | +0.14 |
| STOK Stoke Therapeutics Inc. | Add +17.5% | 0.42% | +0.10 |
| XERS Xeris Biopharma Holdings Inc. | New | 0.09% | +0.09 |
| TSHA Taysha Gene Therapies Inc. | Add +17.6% | 0.95% | +0.05 |
| PTCT PTC Therapeutics Inc. | Add +2.0% | 9.60% | +0.04 |
All Filings
| Quarter | Positions | 13F Reported Value | Top Holdings |
|---|---|---|---|
| Q2 2026Amended | 52 | $723.7M | PTCT, ACAD, INSM, MIRM, ANAB |
| Q1 2026 | 51 | $653.9M | INSM, ACAD, PTCT, BMRN, UTHR |
| Q4 2025 | 49 | $718.4M | INSM, FOLD, PTCT, ACAD, BMRN |
| Q3 2025 | 44 | $540.4M | INSM, PTCT, ACAD, FOLD, BMRN |
| Q2 2025 | 45 | $470.0M | INSM, ACAD, BMRN, FOLD, UTHR |
| Q1 2025 | 44 | $525.1M | INSM, BMRN, FOLD, ACAD, UTHR |
| Q4 2024 | 43 | $645.4M | INSM, FOLD, BMRN, UTHR, ACAD |
| Q3 2024 | 45 | $769.9M | INSM, FOLD, BMRN, UTHR, BIIB |
| Q2 2024 | 39 | $863.0M | INSM, BMRN, FOLD, UTHR, BIIB |
| Q1 2024 | 38 | $886.7M | INSM, FOLD, BMRN, BIIB, UTHR |