Exhibit 10.25

This Waiver (this “Waiver”), dated December 29, 2017 (the “Effective Date”), is
by and between Zafgen, Inc., a Delaware corporation (the “Company”), and Jeffrey
Hatfield (“Hatfield”), and implements waiver of certain provisions of (i) that
certain Offer Letter, dated as of October 3, 2017, by and between the Company
and Hatfield (the “Offer Letter”), and (ii) that certain Non-Qualified
Inducement Stock Option Agreement, dated as of October 9, 2017, by and between
the Company and Hatfield (the “Option Agreement”). Defined terms used but not
otherwise defined herein, shall have the meanings ascribed to such terms in the
Offer Letter or the Option Agreement, as applicable.

WHEREAS, due to the unanticipated accounting consequences associated with
including a cash runway and financing condition in the Offer Letter and Option
Agreement; and

WHEREAS, the Company’s Board of Directors believes that the stock price
performance targets are sufficient to expect that the Company will have or be
able to the obtain necessary financial resources to pursue its business plans.

NOW THERREFORE, effective as of the Effective Date, the Board of Directors has
determined to amend the Offer Letter and Option Agreement to irrevocably waive
the foregoing conditions:

 

1. Offer Letter:

 

  a. The condition in the third bullet point under the Performance
Period/Metrics heading of Appendix 1 of the Offer Letter, which reads “In order
to earn any options, the Company must also have a reasonable cash runway to
pursue its business plans, as determined by the Board”

 

  b. The condition in the second bullet point under the Payout Curve heading of
Appendix 1 of the Offer Letter, which reads “and the reasonable level of
financing has also been achieved”

 

  2. Option Agreement:

 

  a. The condition in the third bullet point of Schedule A of the Option
Agreement, which reads “In order to earn any Option Shares, the Company must
also have a reasonable cash runway to pursue its business plans, as determined
by the Board”.

 

  b. The condition in the second bullet point under the Payout Curve heading of
Appendix A of the Option Agreement, which reads “and the reasonable level of
financing has also been achieved”

The parties hereby acknowledge and agree to this Waiver:

 

ZAFGEN, INC. By:  

/s/ Peter Barrett

Name:   Peter Barrett Title:   Chairman of the Board of Directors

 

/s/ Jeffrey Hatfield

Jeffrey Hatfield