Security	Date	Code	Shares	Price	A/D	Owned after	D/I	Nature of ownership
Common Stock^F1,F2,F3,F4	May 21, 2018	S	29,005	$51.1604	D	4,046,206	I	See Footnotes
Common Stock^F1,F2,F4,F5	May 21, 2018	S	1,595	$51.0589	D	4,044,611	I	See Footnotes
Common Stock^F6,F4,F5,F7	May 21, 2018	S	474	$52.13	D	4,044,137	I	See Footnotes
Common Stock^F6,F4,F7,F8	May 21, 2018	S	26	$52.13	D	4,044,111	I	See Footnotes
Common Stock^F9,F4,F8,F10	May 22, 2018	S	5,592	$50.8593	D	4,038,519	I	See Footnotes
Common Stock^{F9,F4,F10,F11}	May 22, 2018	S	308	$50.6851	D	4,038,211	I	See Footnotes
Common Stock^F4,F11,F12	May 23, 2018	S	474	$50.50	D	4,037,737	I	See Footnotes
Common Stock^F4,F12,F13	May 23, 2018	S	26	$50.50	D	4,037,711	I	See Footnotes

Table II — derivative securities

No Table II lines on this filing.

Explanation of responses

F1The price represents the weighted average price with a low of $51.00 and a high of $51.755. The Reporting Persons undertake to provide G1 Therapeutics, Inc., any security holder of G1 Therapeutics, Inc., or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in footnote 1 to this Form 4.
F10Following the reported transaction, 3,826,726 shares of the reportable securities are owned directly by HVP IV.
F11Following the reported transaction, 210,490 shares of the reportable securities are owned directly by Hatteras NC.
F12Following the reported transaction, 3,826,252 shares of the reportable securities are owned directly by HVP IV.
F13Following the reported transaction, 210,464 shares of the reportable securities are owned directly by Hatteras NC.
F2Following the reported transaction, 3,832,792 shares of the reportable securities are owned directly by Hatteras Venture Partners IV SBIC, LP ("HVP IV"). Hatteras Venture Advisors IV SBIC, LLC ("HVA IV SBIC") is the general partner of HVP IV. The securities directly held by HVP IV are indirectly held by the individual managing members of HVA IV SBIC (each, a "GP Managing Member" and collectively, the "GP Managing Members"). The GP Managing Members are John Crumpler, Clay Thorp, Ken Lee, Douglas Reed and Robert Ingram. The GP Managing Members may share voting and dispositive power over the securities directly held by HVP IV. Each GP Managing Member disclaims beneficial ownership of these securities and this report is not an admission that any GP Managing Member is a beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of his pecuniary interest therein.
F3Following the reported transaction, 212,419 shares of the reportable securities are owned directly by Hatteras NC Fund, LP ("Hatteras NC"). Hatteras Venture Advisors IV, LLC ("HVA IV") is the general partner of Hatteras NC Fund, LP. The securities directly held by Hatteras NC are indirectly held by the individual managing members of HVA IV (each, a "HVA IV Managing Member" and collectively, the "HVA IV Managing Members"). The HVA IV Managing Members are John Crumpler, Clay Thorp, Ken Lee, Douglas Reed and Robert Ingram. The HVA IV Managing Members may share voting and dispositive power over the securities directly held by HVP IV. Each HVA IV Managing Member disclaims beneficial ownership of these securities and this report is not an admission that any HVA IV Managing Member is a beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of his pecuniary interest therein.
F4995 shares of the reportable securities are owned directly by Hatteras Venture Advisors V, LLC ("HVA V"). The securities directly held by HVA V are indirectly held by the individual managing members of HVA V (each, a "Managing Member" and collectively, the "Managing Members"). The Managing Members are John Crumpler, Clay Thorp, Christy Shaffer, Douglas Reed and Robert Ingram. The Managing Members may share voting and dispositive power over the securities directly held by HVA V. Each Managing Member disclaims beneficial ownership of these securities and this report is not an admission that any Managing Member is a beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of his or her pecuniary interest therein.
F5Following the reported transaction, 210,824 shares of the reportable securities are owned directly by Hatteras NC.
F6The price represents the weighted average price with a low of $52.12 and a high of $52.14.
F7Following the reported transaction, 3,832,318 shares of the reportable securities are owned directly by HVP IV.
F8Following the reported transaction, 210,798 shares of the reportable securities are owned directly by Hatteras NC.
F9The price represents the weighted average price with a low of $50.50 and a high of $51.25.