Matthew Stanton - May 10, 2021 Form 4 Insider Report for Generation Bio Co. (GBIO)

Role: CHIEF SCIENTIFIC OFFICER
Signature: /s/ Jennifer Elliott, Attorney-in-Fact
Stock symbol: GBIO
Transactions as of: May 10, 2021
Transactions value $: -$269,224
Form type: 4
Date filed: 5/12/2021, 04:05 PM
Next filing: May 28, 2021

Transactions Table

Type	Sym	Class	Transaction	Value $	Shares	Change %	* Price $	Shares After	Date	Ownership	Footnotes
transaction	GBIO	Common Stock	Options Exercise	$5.16K	+8.6K	+4.34%	$0.60^*	207K	May 10, 2021	Direct	F1
transaction	GBIO	Common Stock	Sale	-$188K	-6.2K	-3%	$30.37^*	201K	May 10, 2021	Direct	F1, F2
transaction	GBIO	Common Stock	Sale	-$65.2K	-2.1K	-1.05%	$31.03^*	198K	May 10, 2021	Direct	F1, F3
transaction	GBIO	Common Stock	Sale	-$9.66K	-300	-0.15%	$32.19^*	198K	May 10, 2021	Direct	F1
transaction	GBIO	Common Stock	Options Exercise	$103	+172	+0.09%	$0.60^*	198K	May 11, 2021	Direct	F1
transaction	GBIO	Common Stock	Options Exercise	$1.05K	+228	+0.11%	$4.59	199K	May 11, 2021	Direct	F1
transaction	GBIO	Common Stock	Sale	-$12.4K	-400	-0.2%	$31.05^*	198K	May 11, 2021	Direct	F1, F4

Derivative Securities (e.g., puts, calls, warrants, options, convertible securities)

Type	Sym	Class	Transaction	Value $	Shares	Change %	* Price $	Shares After	Date	Underlying Class	Amount	Exercise Price	Ownership	Footnotes
transaction	GBIO	Stock Option (right to buy)	Options Exercise	$0	-8.6K	-34.14%	$0.00	16.6K	May 10, 2021	Common Stock	8.6K	$0.60	Direct	F1, F5
transaction	GBIO	Stock Option (right to buy)	Options Exercise	$0	-172	-1.04%	$0.00	16.4K	May 11, 2021	Common Stock	172	$0.60	Direct	F1, F5
transaction	GBIO	Stock Option (right to buy)	Options Exercise	$0	-228	-0.21%	$0.00	108K	May 11, 2021	Common Stock	228	$4.59	Direct	F1, F6

* An asterisk sign (*) next to the price indicates that the price is likely invalid.

Explanation of Responses:

Id	Content
F1	These transactions were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on August 24, 2020.
F2	The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $29.83 to $30.82, inclusive. The reporting person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the U.S. Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in footnotes (2) through (4) of this Form 4.
F3	The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $30.86 to $31.16, inclusive.
F4	The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $31.00 to $31.16, inclusive.
F5	The option to purchase 87,584 shares of common stock was granted on January 5, 2018. The shares underlying the option vest over four years, with 25% of the shares vested on January 4, 2019 and the remaining shares vesting in equal quarterly installments thereafter.
F6	The option to purchase 108,305 shares of common stock was granted on April 2, 2018. The shares underlying the option vest over four years, with 25% of the shares vested on April 2, 2019 and the remaining shares vesting in equal quarterly installments thereafter.