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Fairmount Funds Management LLC

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13F filer, CIK 1802528, WEST CONSHOHOCKEN, PA

Fairmount Funds Management LLC reported $1,313,784,318 across 13 holdings for the quarter ended 2025-12-31, in a 13F-HR filed 2026-02-17. Its ten largest share positions make up 92.03% of the portfolio.

Filed (acceptance time not in the bulk data set), ingested 13F-HR 0001104659-26-016303

Period
2025-12-31
Reported value
$1.31B
Holdings
13
Top 10 weight
92.03%
New
0
Sold out
4

Part of the filer group Fairmount Funds Management LLC

  • Fairmount Healthcare Fund II L.P.
  • Harwin Peter Evan
  • Kiselak Tomas
How groups are built

Largest buys vs the previous quarter

SecurityShares changeApprox. value
JBIOadded+1,333,126$20.6M
CBIOadded+1,360,000$16.1M
VRDNadded+454,545$14.1M
ZBIOadded+316,219$11.5M
IKTadded+2,500,000$5.12M

Ranked by the share change valued at this quarter's implied price (value over shares in the 13F). A position sold out is valued at the previous quarter's price, its last report.

Largest sells vs the previous quarter

SecurityShares changeApprox. value
AXSMexited-815,176-$99M
SRRKexited-1,824,031-$67.9M
ABVXexited-713,434-$60.6M
DNTHreduced-1,170,000-$48.2M
ASTRIA THERAPEUTICS INCexited-3,554,129-$25.9M

Ranked by the share change valued at this quarter's implied price (value over shares in the 13F). A position sold out is valued at the previous quarter's price, its last report.

Holdings, Q4 2025

Share positions as resolved from 13F-HR 0001104659-26-016303, largest first. % of portfolio is the value over $1,313,784,318, the sum of the share positions whose value is usable for ratios (method).

SecurityHistorySharesValue% of portfolioChangeLatest eventTimeline
COGTCOGENT BIOSCIENCES INCQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2024Q1: restricted; 2024Q2: restricted; 2024Q3: 6,225,641 shares; 2024Q4: 6,225,641 shares; 2025Q1: 6,225,641 shares; 2025Q2: 6,225,641 shares; 2025Q3: 9,003,418 shares; 2025Q4: 9,003,418 shares 9,003,418$320M24.34%0Timeline
APGEAPOGEE THERAPEUTICS INCQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2024Q1: restricted; 2024Q2: restricted; 2024Q3: 2,048,647 shares; 2024Q4: 2,048,647 shares; 2025Q1: 2,048,647 shares; 2025Q2: 2,048,647 shares; 2025Q3: 2,048,647 shares; 2025Q4: 2,048,647 shares 2,048,647$155M11.77%0Timeline
SYRESPYRE THERAPEUTICS INCQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2024Q1: restricted; 2024Q2: restricted; 2024Q3: 4,018,101 shares; 2024Q4: 4,018,101 shares; 2025Q1: 4,018,101 shares; 2025Q2: 4,018,101 shares; 2025Q3: 4,018,101 shares; 2025Q4: 4,018,101 shares 4,018,101$132M10.02%02026-10-07, 13D/A: 10,185,961 shares, 9.99% of the class, 13D/A filed 2026-10-09 Timeline
VRDNVIRIDIAN THERAPEUTICS INCQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2024Q1: restricted; 2024Q2: restricted; 2024Q3: 3,445,813 shares; 2024Q4: 3,445,813 shares; 2025Q1: 3,445,813 shares; 2025Q2: 3,459,913 shares; 2025Q3: 3,459,913 shares; 2025Q4: 3,914,458 shares 3,914,458$122M9.27%+454,545Timeline
ORKAORUKA THERAPEUTICS INCQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2024Q1: restricted; 2024Q2: restricted; 2024Q3: 3,211,922 shares; 2024Q4: 3,371,922 shares; 2025Q1: 3,371,922 shares; 2025Q2: 3,371,922 shares; 2025Q3: 3,705,262 shares; 2025Q4: 3,705,262 shares 3,705,262$112M8.55%0Timeline
DNTHDIANTHUS THERAPEUTICS INCQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2024Q1: restricted; 2024Q2: restricted; 2024Q3: 2,700,691 shares; 2024Q4: 2,700,691 shares; 2025Q1: 2,700,691 shares; 2025Q2: 2,707,191 shares; 2025Q3: 3,307,191 shares; 2025Q4: 2,137,191 shares 2,137,191$88.1M6.7%-1,170,000Timeline
ZBIOZENAS BIOPHARMA INCQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2024Q1: restricted; 2024Q2: restricted; 2024Q3: 1,892,806 shares; 2024Q4: 1,892,806 shares; 2025Q1: 1,892,806 shares; 2025Q2: 1,892,806 shares; 2025Q3: 1,892,806 shares; 2025Q4: 2,209,025 shares 2,209,025$80.2M6.11%+316,219Timeline
NUVLNUVALENT INCQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2024Q1: restricted; 2024Q2: restricted; 2024Q3: 1,687,064 shares; 2024Q4: 1,317,664 shares; 2025Q1: 727,563 shares; 2025Q2: 727,563 shares; 2025Q3: 727,563 shares; 2025Q4: 727,563 shares 727,563$73.2M5.57%0Timeline
JBIOJADE BIOSCIENCES INCQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2024Q1: restricted; 2024Q2: restricted; 2024Q3: not reported; 2024Q4: not reported; 2025Q1: not reported; 2025Q2: 3,220,368 shares; 2025Q3: 3,220,368 shares; 2025Q4: 4,553,494 shares 4,553,494$70.3M5.35%+1,333,126Timeline
ELVNENLIVEN THERAPEUTICS INCQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2024Q1: restricted; 2024Q2: restricted; 2024Q3: 3,202,798 shares; 2024Q4: 3,202,798 shares; 2025Q1: 3,202,798 shares; 2025Q2: 3,711,444 shares; 2025Q3: 3,711,444 shares; 2025Q4: 3,711,444 shares 3,711,444$57.2M4.35%0Timeline
KNSAKINIKSA PHARMACEUTICALS INTLQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2024Q1: restricted; 2024Q2: restricted; 2024Q3: 3,204,841 shares; 2024Q4: 2,194,341 shares; 2025Q1: 1,102,248 shares; 2025Q2: 1,772,839 shares; 2025Q3: 1,772,839 shares; 2025Q4: 1,319,688 shares 1,319,688$54.4M4.14%-453,151Timeline
CBIOCRESCENT BIOPHARMA INC.Quarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2024Q1: restricted; 2024Q2: restricted; 2024Q3: not reported; 2024Q4: not reported; 2025Q1: not reported; 2025Q2: 1,387,866 shares; 2025Q3: 1,387,866 shares; 2025Q4: 2,747,866 shares 2,747,866$32.6M2.48%+1,360,000Timeline
IKTINHIBIKASE THERAPEUTICS INCQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2024Q1: restricted; 2024Q2: restricted; 2024Q3: not reported; 2024Q4: 6,125,000 shares; 2025Q1: 6,125,000 shares; 2025Q2: 6,125,000 shares; 2025Q3: 6,125,000 shares; 2025Q4: 8,625,000 shares 8,625,000$17.7M1.35%+2,500,000Timeline

Sold out in Q4 2025

Positions in the previous quarter's report that this quarter's report no longer lists.

SecurityShares beforeValue beforeType
AXSMAXSOME THERAPEUTICS INC.815,176$99Mshares
SRRKSCHOLAR ROCK HLDG CORP1,824,031$67.9Mshares
ABVXABIVAX SA713,434$60.6Mshares
ASTRIA THERAPEUTICS INCASTRIA THERAPEUTICS INC3,554,129$25.9Mshares

How Q4 2025 was built

Available 13F filings of this filer for the quarter and their roles: the base report is the latest original or restatement, NEW HOLDINGS amendments filed after it are added (method).

FilingRoleAmendmentFiledAcceptedIngested
13F-HR 0001104659-26-016303 base2026-02-17acceptance time not in the bulk data set