Editas Medicine, Inc. — Director's Dealing 2016

Feb 9, 2016

SEC Form 4 — Statement of Changes in Beneficial Ownership

Issuer: Editas Medicine, Inc. (EDIT)
CIK: 0001650664
Period of Report: 2016-02-08

Reporting Person: VIKING GLOBAL INVESTORS LP (10% Owner)
Reporting Person: Viking Global Opportunities Illiquid Investments Sub-Master LP (10% Owner)
Reporting Person: Viking Global Opportunities Portfolio GP LLC (10% Owner)
Reporting Person: Viking Global Opportunities GP LLC (10% Owner)
Reporting Person: HALVORSEN OLE ANDREAS (10% Owner)
Reporting Person: Ott David C. (10% Owner)
Reporting Person: Sundheim Daniel S. (10% Owner)

Non-Derivative Transactions

Date	Security	Code	Shares	Price	A/D	Holdings After	Ownership
2015-02-08	Common Stock	C	1709401	—	Acquired	1709401	Indirect
2015-02-08	Common Stock	P	1000000	—	Acquired	2709401	Indirect
2015-02-08	Common Stock	P	20407	—	Acquired	2729808	Indirect
2015-02-08	Common Stock	C	1709401	—	Acquired	1709401	Direct
2015-02-08	Common Stock	P	256986	—	Acquired	256986	Direct
2015-02-08	Common Stock	P	15072	—	Acquired	15072	Direct
2015-02-08	Common Stock	P	481567	—	Acquired	481567	Direct
2015-02-08	Common Stock	P	261447	—	Acquired	261447	Direct
2015-02-08	Common Stock	P	5335	—	Acquired	266782	Direct

Derivative Transactions

Date	Security	Exercise Price	Code	Shares	A/D	Expiration	Underlying	Ownership
2016-02-08	Series B Preferred Stock	$	C	4444444	Disposed		Common Stock (1709401)	Indirect
2016-02-08	Series B Preferred Stock	$	C	4444444	Disposed		Common Stock (1709401)	Direct

Footnotes

F1: O. Andreas Halvorsen, David C. Ott and Daniel S. Sundheim are Executive Committee members of certain management entities, including Viking Global Partners LLC, the general partner of Viking Global Investors LP ("VGI"), Viking Global Performance LLC ("VGP"), Viking Long Fund GP LLC ("VLFGP") and Viking Global Opportunities GP LLC ("Opportunities GP"), the sole owner of Viking Global Opportunities Portfolio GP LLC ("Opportunities Portfolio GP"). VGI provides managerial services to various investment funds, including Viking Global Opportunities Illiquid Investments Sub-Master LP ("Opportunities Fund"), Viking Global Equities LP ("VGE"), Viking Global Equities II LP ("VGE II"), VGE III Portfolio Ltd. ("VGE III") and Viking Long Fund Master Ltd. ("VLFM," and together with VGE, VGE II, VGE III and Opportunities Fund, the "Viking Funds").

F2: VGP is the general partner of VGE and VGE II and the investment manager of VGE III. Opportunities Portfolio GP is the general partner of Opportunities Fund. VLFGP serves as the investment manager of VLFM. Each of the Viking Funds, VGI, VGP, VLFGP, Opportunities GP, Opportunities Portfolio GP, Mr. Halvorsen, Mr. Ott and Mr. Sundheim (collectively, the "Reporting Persons") may be deemed to beneficially own the shares reported on this form.

F3: VGI provides managerial services to (i) VGE, which directly holds 256,986 shares of common stock of the Issuer ("Common Stock"); (ii) VGE II, which directly holds 15,072 shares of Common Stock; (iii) VGE III, which directly holds 481,567 shares of Common Stock; (iv) VLFM, which directly holds 266,782 shares of Common Stock; and (v) Opportunities Fund, which directly holds 1,709,401 shares of Common Stock. Because of the relationship between VGI and the Viking Funds, VGI may be deemed to beneficially own the shares of Common Stock directly held by the Viking Funds.

F4: VGP is the general partner of VGE and VGE II and the investment manager of VGE III. Because of the relationships between VGP and VGE, VGE II and VGE III, respectively, VGP may be deemed to beneficially own the shares of Common Stock directly held by VGE, VGE II and VGE III.

F5: VLFGP serves as the investment manager of VLFM. Because of the relationship between VLFGP and VLFM, VLFGP may be deemed to beneficially own the shares of Common Stock directly held by VLFM.

F6: Opportunities Portfolio GP is the general partner of Opportunities Fund. Because of the relationship between Opportunities Portfolio GP and Opportunities Fund, Opportunities Portfolio GP may be deemed to beneficially own the shares of Common Stock held directly by Opportunities Fund. Opportunities GP is the sole owner of Opportunities Portfolio GP. Because of the relationship between Opportunities GP and Opportunities Portfolio GP, Opportunities GP may be deemed to beneficially own the shares of Common Stock held directly by Opportunities Fund.

F7: The Reporting Persons disclaim beneficial ownership of these securities except to the extent of their pecuniary interest therein, and the inclusion of these securities in this report shall not be deemed an admission of beneficial ownership of the reported securities for purposes of Section 16 or for any other purpose.

F8: On February 8, 2016, the 4,444,444 shares of Series B Preferred Stock held by Opportunities Fund automatically converted into 1,709,401 shares of Common Stock in connection with the Issuer's initial public offering ("IPO"). The conversion reflected an adjustment for a one-for-2.6 reverse stock split of the Common Stock.

F9: On February 8, 2016, the Viking Funds acquired an aggregate of 1,000,000 shares of Common Stock at a price of $16.00 per share in connection with the IPO. VGE acquired 256,986 shares in the IPO, VGE III acquired 481,567 shares in the IPO and VLFM acquired 261,447 shares in the IPO.

F10: On February 8, 2016, the Viking Funds acquired an aggregate of 20,407 shares of Common Stock at a purchase price of $18.00 per share in open-market transactions following the IPO. VGE II acquired 15,072 of such shares and VLFM acquired 5,335 of such shares.