BAKER BROS. ADVISORS LP 13F: Quarter-over-Quarter Portfolio Changes
BAKER BROS. ADVISORS LP reported a disclosed portfolio value of approximately $17.4 billion in its latest SEC Form 13F-HR filing for Q1 2026, up 2.0% quarter on quarter. Over the quarter, the fund initiated 7 new positions, bought more shares in 18 holdings, trimmed 6 holdings, and exited 9 positions.
BAKER BROS. ADVISORS LP's top buy was a new stake in Mirum Pharmaceuticals INC (MIRM) , equal to 0.2% of the disclosed portfolio. Its top sell was Ultragenyx Pharmaceutical in (RARE) . The fund exited the position completely after it had accounted for 0.4% of the previous portfolio.
New PositionsQ1 2026
Securities disclosed for the first time in Q1 2026 that were not present in the prior 13F-HR filing.
| Company | Ticker | Initial Portfolio Weight | History |
|---|---|---|---|
| MIRUM PHARMACEUTICALS INC | MIRM | 0.2% | Holders → |
| EVOMMUNE INC | EVMN | 0.1% | Holders → |
| AKTIS ONCOLOGY INC | AKTS | 0.1% | Holders → |
| GENERATE BIOMEDICINES INC | GENB | 0.1% | Holders → |
| COMPASS PATHWAYS PLC | CMPS | 0.1% | Holders → |
| EIKON THERAPEUTICS INC | EIKN | 0.0% | Holders → |
| VERASTEM | VSTM | 0.0% | Holders → |
Top BuysQ1 2026
Showing the top 10 buys among 18 existing positions where the fund bought more shares in Q1 2026. Ranked by portfolio-weight impact, with the percentage of additional shares shown separately.
| Company | Ticker | Portfolio Weight Change | More Shares | History |
|---|---|---|---|---|
| ENLIVEN THERAPEUTICS INC | ELVN | +0.2% | +233.5% | Holders → |
| WAVE LIFE SCIENCES LTD. | WVE | +-0.0% | +139.1% | Holders → |
| GRAIL, INC. | GRAL | +0.2% | +93.2% | Holders → |
| PRAXIS PRECISION MEDICINES I | PRAX | +1.3% | +55.6% | Holders → |
| ARCUS BIOSCIENCES INC | RCUS | +0.0% | +53.9% | Holders → |
| CRINETICS PHARMACEUTICALS IN | CRNX | +0.0% | +42.6% | Holders → |
| ALUMIS INC | ALMS | +0.2% | +28.8% | Holders → |
| CYTOMX THERAPEUTICS, INC. | CTMX | +0.0% | +17.1% | Holders → |
| DESIGN THERAPEUTICS INC | DSGN | +0.0% | +15.8% | Holders → |
| IONIS PHARMACEUTICALS INC | IONS | +0.1% | +14.3% | Holders → |
Top SellsQ1 2026
The fund's top sells among positions it retained in Q1 2026. Ranked by portfolio-weight impact. Full exits are listed separately.
| Company | Ticker | Portfolio Weight Change | Shares Sold | History |
|---|---|---|---|---|
| IMMUNOCORE HLDGS PLC | IMCR | -0.3% | 68.4% | Holders → |
| BIONTECH SE | BNTX | -0.1% | 67.5% | Holders → |
| TECTONIC THERAPEUTIC INC | TECX | -0.0% | 32.7% | Holders → |
| ROIVANT SCIENCES LTD | ROIV | 0.1% | 12.4% | Holders → |
| IMMATICS N.V | IMTX | -0.1% | 9.7% | Holders → |
| ARROWHEAD PHARMACEUTICALS INC | ARWR | -0.1% | 8.4% | Holders → |
Full ExitsQ1 2026
Positions present in the prior 13F-HR filing that no longer appear in Q1 2026.
| Company | Ticker | Last-Reported Portfolio Weight |
|---|---|---|
| ULTRAGENYX PHARMACEUTICAL IN | RARE | 0.4% |
| TERNS PHARMACEUTICALS INC | TERN | 0.2% |
| BIOCRYST PHARMACEUTICALS INC | BCRX | 0.1% |
| VENTYX BIOSCIENCES, INC. | VTYXUSD | 0.1% |
| NUVALENT INC | NUVL | 0.1% |
| 4D MOLECULAR THERAPEUTICS IN | FDMT | 0.0% |
| VIR BIOTECHNOLOGY INC | VIR | 0.0% |
| KALA BIO, INC. | KALA | 0.0% |
| ACRIVON THERAPEUTICS, INC. | ACRV | 0.0% |
Net Portfolio Value ChangeQ1 2026
- $17.1BPrior quarter
- $17.4BCurrent quarter
- +$0.3BNet delta
- +2.0%% change
Methodology & FAQ
How BAKER BROS. ADVISORS LP Quarterly Changes Are Computed
All deltas are sourced from sequential SEC Form 13F-HR filings for BAKER BROS. ADVISORS LP: each row joins the most recent filing against the immediately preceding quarterly filing for the same fund. Share-count changes reflect reported trading activity, while portfolio weights can also move because of market price changes. Portfolio weights are normalized to exclude listed options for comparability. A complete description — including how confidential treatment filings are handled — is documented in the Methodology.
What stocks did BAKER BROS. ADVISORS LP buy in Q1 2026?
In Q1 2026, BAKER BROS. ADVISORS LP initiated 7 new positions (MIRUM PHARMACEUTICALS INC (MIRM), EVOMMUNE INC (EVMN), AKTIS ONCOLOGY INC (AKTS), GENERATE BIOMEDICINES INC (GENB), COMPASS PATHWAYS PLC (CMPS), EIKON THERAPEUTICS INC (EIKN), VERASTEM (VSTM)); bought more shares of ENLIVEN THERAPEUTICS INC (ELVN), WAVE LIFE SCIENCES LTD. (WVE), GRAIL, INC. (GRAL), PRAXIS PRECISION MEDICINES I (PRAX), ARCUS BIOSCIENCES INC (RCUS) — the largest 5 of 18 adds.
What stocks did BAKER BROS. ADVISORS LP sell in Q1 2026?
In Q1 2026, BAKER BROS. ADVISORS LP fully sold 9 positions (ULTRAGENYX PHARMACEUTICAL IN (RARE), TERNS PHARMACEUTICALS INC (TERN), BIOCRYST PHARMACEUTICALS INC (BCRX), VENTYX BIOSCIENCES, INC. (VTYXUSD), NUVALENT INC (NUVL), 4D MOLECULAR THERAPEUTICS IN (FDMT), VIR BIOTECHNOLOGY INC (VIR), KALA BIO, INC. (KALA), ACRIVON THERAPEUTICS, INC. (ACRV)); reduced holdings in IMMUNOCORE HLDGS PLC (IMCR), BIONTECH SE (BNTX), TECTONIC THERAPEUTIC INC (TECX), ROIVANT SCIENCES LTD (ROIV), IMMATICS N.V (IMTX) — the largest 5 of 6 reductions.
Which positions did BAKER BROS. ADVISORS LP initiate in Q1 2026?
BAKER BROS. ADVISORS LP established 7 new positions in Q1 2026: MIRUM PHARMACEUTICALS INC (MIRM, 0.2%), EVOMMUNE INC (EVMN, 0.1%), AKTIS ONCOLOGY INC (AKTS, 0.1%), GENERATE BIOMEDICINES INC (GENB, 0.1%), COMPASS PATHWAYS PLC (CMPS, 0.1%), EIKON THERAPEUTICS INC (EIKN, 0.0%), VERASTEM (VSTM, 0.0%).
Which existing positions saw the largest allocation increases for BAKER BROS. ADVISORS LP in Q1 2026?
Of 18 existing positions with share-count increases in Q1 2026, the largest were: ENLIVEN THERAPEUTICS INC (ELVN, +0.2% weight, +233.5% shares), WAVE LIFE SCIENCES LTD. (WVE, +-0.0% weight, +139.1% shares), GRAIL, INC. (GRAL, +0.2% weight, +93.2% shares), PRAXIS PRECISION MEDICINES I (PRAX, +1.3% weight, +55.6% shares), ARCUS BIOSCIENCES INC (RCUS, +0.0% weight, +53.9% shares), CRINETICS PHARMACEUTICALS IN (CRNX, +0.0% weight, +42.6% shares), ALUMIS INC (ALMS, +0.2% weight, +28.8% shares), CYTOMX THERAPEUTICS, INC. (CTMX, +0.0% weight, +17.1% shares), DESIGN THERAPEUTICS INC (DSGN, +0.0% weight, +15.8% shares), IONIS PHARMACEUTICALS INC (IONS, +0.1% weight, +14.3% shares).
Which positions did BAKER BROS. ADVISORS LP fully exit in Q1 2026?
BAKER BROS. ADVISORS LP fully exited 9 positions in Q1 2026: ULTRAGENYX PHARMACEUTICAL IN (RARE, last-reported weight 0.4%), TERNS PHARMACEUTICALS INC (TERN, last-reported weight 0.2%), BIOCRYST PHARMACEUTICALS INC (BCRX, last-reported weight 0.1%), VENTYX BIOSCIENCES, INC. (VTYXUSD, last-reported weight 0.1%), NUVALENT INC (NUVL, last-reported weight 0.1%), 4D MOLECULAR THERAPEUTICS IN (FDMT, last-reported weight 0.0%), VIR BIOTECHNOLOGY INC (VIR, last-reported weight 0.0%), KALA BIO, INC. (KALA, last-reported weight 0.0%), ACRIVON THERAPEUTICS, INC. (ACRV, last-reported weight 0.0%).
Which existing positions saw the largest allocation reductions for BAKER BROS. ADVISORS LP in Q1 2026?
Of 6 existing positions with share-count reductions in Q1 2026, the largest were: IMMUNOCORE HLDGS PLC (IMCR, -0.3% weight, -68.4% shares), BIONTECH SE (BNTX, -0.1% weight, -67.5% shares), TECTONIC THERAPEUTIC INC (TECX, -0.0% weight, -32.7% shares), ROIVANT SCIENCES LTD (ROIV, 0.1% weight, -12.4% shares), IMMATICS N.V (IMTX, -0.1% weight, -9.7% shares), ARROWHEAD PHARMACEUTICALS INC (ARWR, -0.1% weight, -8.4% shares).
Do quarter-over-quarter 13F allocation changes constitute explicit trading signals?
No. Quarter-over-quarter changes reflect a combination of active trading and market price movement. A weight increase can result from price appreciation alone, without the manager adding shares. Share-count delta is the cleaner indicator of explicit trading activity. All deltas on this page are sourced from sequential SEC Form 13F-HR filings.