CUSIP No. 98887Q104 SCHEDULE 13G Page 1 of 1 Page

EXHIBIT 1

AGREEMENT AS TO JOINT FILING OF SCHEDULE 13G

The undersigned hereby agree that the Schedule 13G relating to the common stock of Zai Lab Limited., and any further amendments thereto, to which this Agreement as to Joint Filing of Schedule 13G is attached as an exhibit is filed on behalf of each of them pursuant to and in accordance with the provisions of Rule 13d-1(k) under the Securities Exchange Act of 1934, as amended.

Date: February 14, 2018

Sequoia Capital CV IV Holdco, Ltd.
	By:	Sequoia Capital China Venture Fund IV, L.P.
		its Sole Member
	By:	SC China Venture IV Management, L.P.
		its General Partner
	By:	SC China Holding Limited
		its General Partner
	By:	/s/ Neil Nanpeng Shen Neil Nanpeng Shen, Authorized Signatory
Sequoia Capital China Venture Fund IV, L.P.
	By:	SC China Venture IV Management, L.P.
		its General Partner
	By:	SC China Holding Limited
		its General Partner
	By:	/s/ Neil Nanpeng Shen Neil Nanpeng Shen, Authorized Signatory
SC China Venture IV Management, L.P.
	By:	SC China Holding Limited
		its General Partner
	By:	/s/ Neil Nanpeng Shen Neil Nanpeng Shen, Authorized Signatory
SCC Growth I Holdco A, Ltd.
	By:	Sequoia Capital China Growth Fund I, LP
		its Sole Member
	By:	Sequoia Capital China Growth Fund Management I, L.P.
		its General Partner
	By:	SC China Holding Limited
		its General Partner
	By:	/s/ Neil Nanpeng Shen Neil Nanpeng Shen, Authorized Signatory
Sequoia Capital China Growth Fund I, LP
	By:	Sequoia Capital China Growth Fund Management I, L.P.
		its General Partner
	By:	SC China Holding Limited
		its General Partner
	By:	/s/ Neil Nanpeng Shen Neil Nanpeng Shen, Authorized Signatory
Sequoia Capital China Growth Fund Management I, L.P.
	By:	SC China Holding Limited
		its General Partner
	By:	/s/ Neil Nanpeng Shen Neil Nanpeng Shen, Authorized Signatory
SC China Holding Limited
	By:	/s/ Neil Nanpeng Shen Neil Nanpeng Shen, Authorized Signatory
SNP China Enterprises Limited
	By:	/s/ Neil Nanpeng Shen Neil Nanpeng Shen, Authorized Signatory
Neil Nanpeng Shen
	By:	/s/ Neil Nanpeng Shen
		Neil Nanpeng Shen