What does CUSIP 37148K100 represent in this 13F holders report?

CUSIP 37148K100 is the security identifier for GBIO - GENERATION BIO CO. - COMMON STOCK, $0.0001 PAR VALUE used to aggregate holder disclosures.

How many institutions held GBIO - GENERATION BIO CO. - COMMON STOCK, $0.0001 PAR VALUE in Q1 2023?

85 institutional investors reported GBIO - GENERATION BIO CO. - COMMON STOCK, $0.0001 PAR VALUE for Q1 2023. Use the holders table for investor-level position and value details.

GENERATION BIO CO. - COMMON STOCK, $0.0001 PAR VALUE (GBIO)

CUSIP: 37148K100

Q1 2023 13F Holders as of 31 Mar 2023

Security type / class: Equity / COMMON STOCK, $0.0001 PAR VALUE
Total 13F shares: 57,380,158
Total 13F value: $246,742,110
Share change: +239,784
Put/Call ratio: 8.8%
SEC-reported price per share: $4.30
Number of holders: 85
Value change: +$1,739,378
Number of buys: 38
Number of sells: 54
Shares outstanding: 67,017,829

Security key

37148K100

Report period

Q1 2023

Institutions

Top holders

GBIO full security history Ownership snapshot Full 13F holder table Newer quarter: Q4 2025 Generation Bio Co. SEC filings Generation Bio Co. company facts

Broader feeds

Latest 13F filings Latest 13D/G filings Investors directory

Reporting periods

Holder history for CUSIP 37148K100

Newer quarter: Q4 2025

Recent filing periods:

Q2 2026 Q1 2026 Q4 2025

Ownership snapshot

Top reported holders of GBIO - GENERATION BIO CO. - COMMON STOCK, $0.0001 PAR VALUE (13F + 13D/G + 3/4/5)

Grouped by holder across the latest SEC ownership disclosures. Start with comparable ownership when available, then verify the linked 13F, 13D/G, or 3/4/5 evidence.

Comparable stake leader

ATLAS VENTURE ASSOCIATES ...

Disclosed value leader

Atlas Venture Life Scienc...

Comparable rows

0/15

Latest evidence

31 Dec 2022

3/4/5 13F Highest disclosed value: $32,535,983 15 rows are not safely comparable across share classes. Showing 1-6 of 15 holder rows.

Quick read

Atlas Venture Life Science Advisors, LLC has the largest disclosed position value at $32.54M.

0 of 15 rows have a safely comparable ownership percentage. Use this as a filing-backed starting point, then open the detailed table for source links, reporting role, position value, share count, and filing date.

Open SEC evidence Opens Atlas Venture Life Science Advisors, LLC's linked filing trail.

Disclosed position value Top 5

ATLAS VENTURE ASSOCIATES X, L.P. $1.2K

Atlas Venture Life Science Adviso... $32.54M

PRICE T ROWE ASSOCIATES INC /MD/ $28.54M

BlackRock Finance, Inc. $14.57M

Bellevue Group AG $14.26M

Value bars compare disclosed positions; verify each figure against the linked filing evidence.

Detailed SEC evidence table Showing 1-6 of 15 holder rows

Holder	Evidence	Ownership %	Position	12M Net Δ	As of
ATLAS VENTURE ASSOCIATES X, L.P.	3/4/5 10%+ Owner 3/4/5	— denominator unverified	$1,161 608 shares	—	27 Sep 2021
Atlas Venture Life Science Advisors, LLC	13F Company 13F	— denominator unverified	$32,535,983 8,278,876 shares	—	31 Dec 2022
PRICE T ROWE ASSOCIATES INC /MD/	13F Company 13F	— denominator unverified	$28,536,000 7,261,046 shares	—	31 Dec 2022
BlackRock Finance, Inc.	13F Company 13F	— denominator unverified	$14,572,702 3,708,067 shares	—	31 Dec 2022
Bellevue Group AG	13F Company 13F	— denominator unverified	$14,255,210 3,627,280 shares	—	31 Dec 2022
T. Rowe Price Investment Management, Inc.	13F Company 13F	— denominator unverified	$14,061,000 3,577,755 shares	—	31 Dec 2022

How to read this table

Rows are grouped by holder and ranked first by SEC-reported ownership % when it is safely comparable, then by disclosed holdings value. — indicates unavailable or non-comparable values; "mixed-class rows" means the latest filing spans non-comparable classes.

13F holder rows

Institutional holders as of Q1 2023

Investor-level positions for this CUSIP, loaded as an interactive table.

Institutions

57,380,158

Rows available

Investor	Option	Weight %	Change %	SEC-reported value	* Price	Shares	Share Change	Activity	Report Period

^* SEC-reported price is the security price as of the portfolio date and can indicate the last known price at which the security was still held. The marker flags a reported price that did not pass the local price check.

Compare Q1 2023 vs Q1 2026 Across Filers

Q1 2026 holders

Q1 2023 holders

Holder diff

Investor	Q1 2026 Shares	Q1 2023 Shares	Share Diff	Share Chg %	Q1 2026 value	Q1 2023 value	Value change	Value Chg %

Trend: ostatnie 8 kwartałów (+ wybrane okresy porównania).

Quarterly Holders Trend

Quarterly Value Trend

Quarterly Shares Trend