EXHIBIT 99.1

AGREEMENT

Pursuant to Rule 13d-1(k)(1) under the Securities Exchange Act of 1934, the undersigned hereby agree that only one statement containing the information required by Schedule 13D need be filed with respect to the ownership by each of the undersigned of shares of Common Stock of NanoString Technologies, Inc.

Date: March 22, 2019

CLARUS LIFESCIENCES II, L.P.
By: Clarus Ventures II GP, L.P., its general partner
By: Blackstone Clarus II L.L.C., its general partner
By: Blackstone Holdings II L.P., its managing member
By: Blackstone Holdings I/II GP Inc., its general partner
By:	/s/ John G. Finley
Name:	John G. Finley
Title:	Chief Legal Officer
CLARUS VENTURES II GP, L.P.
By: Blackstone Clarus II L.L.C., its general partner
By: Blackstone Holdings II L.P., its managing member
By: Blackstone Holdings I/II GP Inc., its general partner
By:	/s/ John G. Finley
Name:	John G. Finley
Title:	Chief Legal Officer
BLACKSTONE CLARUS II L.L.C.
By: Blackstone Holdings II L.P., its managing member
By: Blackstone Holdings I/II GP Inc., its general partner
By:	/s/ John G. Finley
Name:	John G. Finley
Title:	Chief Legal Officer
BLACKSTONE HOLDINGS II L.P.
By: Blackstone Holdings I/II GP Inc., its general partner
By:	/s/ John G. Finley
Name:	John G. Finley
Title:	Chief Legal Officer

[NanoString Technologies, Inc. – Joint Filing Agreement]

BLACKSTONE HOLDINGS I/II GP INC.
By:	/s/ John G. Finley
Name:	John G. Finley
Title:	Chief Legal Officer
THE BLACKSTONE GROUP L.P.
By: Blackstone Group Management L.L.C., its general partner
By:	/s/ John G. Finley
Name:	John G. Finley
Title:	Chief Legal Officer
BLACKSTONE GROUP MANAGEMENT L.L.C.
By:	/s/ John G. Finley
Name:	John G. Finley
Title:	Chief Legal Officer

/s/ Stephen A. Schwarzman

Stephen A. Schwarzman

[NanoString Technologies, Inc. – Joint Filing Agreement]