Amendment No. 1 to Commercial Supply Agreement, dated February 16, 2018, by and between the Registrant and Catalent Pharma Solutions, LLC

Exhibit 10.21

EXECUTION VERSION

Confidential Materials omitted and filed separately with the

Securities and Exchange Commission. Double asterisks denote omissions.

FIRST AMENDMENT TO THE COMMERCIAL SUPPLY AGREEMENT

This First Amendment to Commercial Supply Agreement (the “First Amendment”) is made as of  February 16,  2018 ("First Amendment Effective Date") by and between Kala Pharmaceutical Inc. a Delaware corporation with offices located at 100 Beaver Street, #201, Waltham, Massachusetts 202453 USA ("Client") and Catalent Pharma Solutions, LLC, a Delaware corporation with offices located at 14 Schoolhouse Road, Somerset, New Jersey 08873 ("Catalent").  Each of Client and Catalent may be referred to as a Party, and collectively as the Parties.

WHEREAS, the Parties entered into a Commercial  Supply Agreement dated June 27, 2016 (the "Agreement"), pursuant to which Catalent provides services to Client;  and

WHEREAS, the Parties wish to amend certain terms of the Agreement;

NOW, THEREFORE, in consideration of the mutual promises contained herein, and for good and valuable consideration, the receipt and sufficiency thereof are hereby acknowledged, the Parties do hereby agree as follows:

IN WITNESS WHEREOF, the Parties hereto have duly executed this First Amendment as of the First Amendment Effective Date.

ATTACHMENT C

UNIT PRICING, FEES AND MINIMUM REQUIREMENT

Commercial pricing for 1st year surgical products at smaller batches:

1 Packaging will consist of wrap around label, individual carton and insert

2 The minimum for a sublotted batch will be [**] percent ([**]%) of total units in a Batch.

*Any Units purchased by Client for resale shall count towards the Minimum Requirement, even if purchased by Client prior to Minimum Requirement Year 1.