Spero Therapeutics, Inc. — Director's Dealing 2017

Nov 7, 2017

SEC Form 4 — Statement of Changes in Beneficial Ownership

Issuer: Spero Therapeutics, Inc. (SPRO)
CIK: 0001701108
Period of Report: 2017-11-06

Reporting Person: FORMELA JEAN FRANCOIS (Director)

Non-Derivative Transactions

Date	Security	Code	Shares	Price	A/D	Holdings After	Ownership
2017-11-06	Common Stock	C	245605	—	Acquired	288386	Indirect
2017-11-06	Common Stock	C	246272	—	Acquired	534658	Indirect
2017-11-06	Common Stock	C	328992	—	Acquired	863650	Indirect
2017-11-06	Common Stock	C	513318	—	Acquired	1376968	Indirect
2017-11-06	Common Stock	C	602589	—	Acquired	1979557	Indirect
2017-11-06	Common Stock	P	428571	$14.00	Acquired	2408128	Indirect

Derivative Transactions

Date	Security	Exercise Price	Code	Shares	A/D	Expiration	Underlying	Ownership
2017-11-06	Junior Preferred Stock	$	C	1492645	Disposed		Common Stock (245605)	Indirect
2017-11-06	Series A Preferred Stock	$	C	982906	Disposed		Common Stock (246272)	Indirect
2017-11-06	Series B Preferred Stock	$	C	1250000	Disposed		Common Stock (328992)	Indirect
2017-11-06	Series C Preferred Stock	$	C	3119633	Disposed		Common Stock (513318)	Indirect
2017-11-06	Series C Preferred Stock	$	C	3662178	Disposed		Common Stock (602589)	Indirect

Footnotes

F1: Reflects shares of the Issuer's common stock that were purchased in connection with the Issuer's initial public offering.

F2: Amount of underlying securities reflects the application of the applicable conversion ratio as set forth in the Issuer's Amended and Restated Certificate of Incorporation in effect immediately prior to the closing of the initial public offering (as adjusted by the 1-for-6.0774 reverse stock split of the Issuer's common stock effected on October 20, 2017). Each series of preferred stock was automatically converted upon the closing of the Issuer's initial public offering without payment of further consideration and had no expiration date.

F3: Shares held by Atlas Venture Fund IX, L.P. ("Atlas Venture Fund IX"). The general partner of Atlas Venture Fund IX is Atlas Venture Associates IX, L.P. ("AVA IX LP"). Atlas Venture Associates IX, LLC ("AVA IX LLC") is the general partner of AVA IX LP. Dr. Formela is a member of AVA IX LLC and disclaims beneficial ownership of such shares, except to the extent of his pecuniary interest therein, if any.

F4: Shares held by Atlas Venture Fund X, L.P. ("Atlas Venture Fund X"). The general partner of Atlas Venture Fund X is Atlas Venture Associates X, L.P. ("AVA X LP"). Atlas Venture Associates X, LLC ("AVA X LLC") is the general partner of AVA X LP. Dr. Formela is a member of AVA X LLC and disclaims beneficial ownership of such shares, except to the extent of his pecuniary interest therein, if any.