Exhibit 99.1

The undersigned agree that this Schedule 13D, and all amendments thereto, relating to the Common Stock of Graybug Vision, Inc. shall be filed on behalf of the undersigned.

DEERFIELD MGMT III, L.P.
By: J.E. Flynn Capital III, LLC, General Partner
By:	/s/ Jonathan Isler
Name:	Jonathan Isler
Title:	Attorney-in-Fact
DEERFIELD PRIVATE DESIGN FUND III, L.P.
By: Deerfield Mgmt III, L.P., General Partner
By: J.E. Flynn Capital III, LLC, General Partner
By:	/s/ Jonathan Isler
Name:	Jonathan Isler
Title:	Attorney-in-Fact
DEERFIELD MGMT HIF, L.P.
By:  J.E. Flynn Capital HIF, LLC, General Partner
By:	/s/ Jonathan Isler
	Jonathan Isler, Attorney-In-Fact
DEERFIELD HEALTHCARE INNOVATIONS FUND, L.P.
By:  Deerfield Mgmt HIF, L.P., General Partner
By:  J.E. Flynn Capital HIF, LLC, General Partner
By:	/s/ Jonathan Isler
	Jonathan Isler, Attorney-In-Fact
DEERFIELD PARTNERS, L.P.
By:  Deerfield Mgmt, L.P., General Partner
By:  J.E. Flynn Capital, LLC, General Partner
By:	/s/ Jonathan Isler
Name:	Jonathan Isler
Title:	Attorney-in-Fact

DEERFIELD MGMT, L.P.
By:  J.E. Flynn Capital, LLC, General Partner
By:	/s/ Jonathan Isler
Name:	Jonathan Isler
Title:	Attorney-in-Fact
DEERFIELD MANAGEMENT COMPANY, L.P.
By:  Flynn Management LLC, General Partner
By:	/s/ Jonathan Isler
Name:	Jonathan Isler
Title:	Attorney-in-Fact
JAMES E. FLYNN
/s/ Jonathan Isler
Jonathan Isler, Attorney-in-Fact