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Atlas Venture Life Science Advisors, LLC

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13F filer, CIK 1917529, CAMBRIDGE, MA

Atlas Venture Life Science Advisors, LLC reported $865,154,717 across 8 holdings for the quarter ended 2025-12-31, in a 13F-HR filed 2026-02-13.

Filed (acceptance time not in the bulk data set), ingested 13F-HR 0001104659-26-014463

Period
2025-12-31
Reported value
$865M
Holdings
8
Top 10 weight
100%
New
1
Sold out
2

Largest buys vs the previous quarter

SecurityShares changeApprox. value
GENERATION BIO COnew+827,946$4.7M

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
IRONreduced-628,742-$49.9M
SIONreduced-619,925-$25.5M
KYMRreduced-236,588-$18.4M
GENERATION BIO COexited-827,946-$5.07M
IMAexited-377,814-$3.08M

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 0001104659-26-014463, largest first. % of portfolio is the value over $865,154,717, the sum of the share positions whose value is usable for ratios (method).

SecurityHistorySharesValue% of portfolioChangeLatest eventTimeline
KYMRKYMERA THERAPEUTICS INCQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2024Q1: restricted; 2024Q2: restricted; 2024Q3: 4,896,462 shares; 2024Q4: 4,896,462 shares; 2025Q1: 4,896,462 shares; 2025Q2: 4,896,462 shares; 2025Q3: 4,896,462 shares; 2025Q4: 4,659,874 shares 4,659,874$363M41.91%-236,588Timeline
DYNDYNE THERAPEUTICS INCQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2024Q1: restricted; 2024Q2: restricted; 2024Q3: 8,020,136 shares; 2024Q4: 8,019,354 shares; 2025Q1: 9,130,465 shares; 2025Q2: 9,130,465 shares; 2025Q3: 9,130,465 shares; 2025Q4: 9,130,465 shares 9,130,465$179M20.64%0Timeline
SIONSIONNA THERAPEUTICS INCQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2024Q1: restricted; 2024Q2: restricted; 2024Q3: not reported; 2024Q4: not reported; 2025Q1: 3,694,020 shares; 2025Q2: 3,694,020 shares; 2025Q3: 3,615,527 shares; 2025Q4: 2,995,602 shares 2,995,602$123M14.24%-619,925Timeline
IRONDISC MEDICINE INCQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2024Q1: restricted; 2024Q2: restricted; 2024Q3: 2,509,456 shares; 2024Q4: 2,509,456 shares; 2025Q1: 2,384,456 shares; 2025Q2: 2,384,456 shares; 2025Q3: 2,142,617 shares; 2025Q4: 1,513,875 shares 1,513,875$120M13.9%-628,742Timeline
DAWNDAY ONE BIOPHARMACEUTICALS IQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2024Q1: restricted; 2024Q2: restricted; 2024Q3: 6,430,257 shares; 2024Q4: 6,430,257 shares; 2025Q1: 6,430,257 shares; 2025Q2: 6,430,257 shares; 2025Q3: 6,430,257 shares; 2025Q4: 6,412,560 shares 6,412,560$59.8M6.91%-17,697Timeline
KRROKORRO BIO INCQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2024Q1: restricted; 2024Q2: restricted; 2024Q3: 1,137,149 shares; 2024Q4: 1,137,149 shares; 2025Q1: 1,137,149 shares; 2025Q2: 1,137,149 shares; 2025Q3: 1,137,149 shares; 2025Q4: 1,137,149 shares 1,137,149$9.11M1.05%0Timeline
QTTBQ32 BIO INCQuarterly shares; oldest to newest; scale is this security's eight-quarter maximum; 2024Q1: restricted; 2024Q2: restricted; 2024Q3: 2,092,106 shares; 2024Q4: 2,092,106 shares; 2025Q1: 2,092,106 shares; 2025Q2: 2,092,106 shares; 2025Q3: 2,092,106 shares; 2025Q4: 2,092,106 shares 2,092,106$6.95M0.8%0Timeline
GENERATION BIO COGENERATION BIO COQuarterly 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: not reported; 2025Q3: not reported; 2025Q4: 827,946 shares 827,946$4.7M0.54%new

Sold out in Q4 2025

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

SecurityShares beforeValue beforeType
GENERATION BIO COGENERATION BIO CO827,946$5.07Mshares
IMAIMAGENEBIO INC377,814$3.08Mshares

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 0001104659-26-014463 base2026-02-13acceptance time not in the bulk data set