Exhibit 10.53

FOURTH AMENDMENT TO EXCLUSIVE LICENSE AGREEMENT

THIS FOURTH AMENDMENT TO EXCLUSIVE LICENSE AGREEMENT (this “Fourth Amendment”) is made and entered into as of February 16, 2018 (“Fourth Amendment Date”), by and among CEDARS-SINAI MEDICAL CENTER, a California nonprofit public benefit corporation (“CSMC”), SYNTHETIC BIOLOGICS, INC., a Nevada corporation (“Synthetic” or “SYN”) and SYNTHETIC BIOMICS, INC., a Nevada corporation (“Licensee”), under the following circumstances:

NOW, THEREFORE, in consideration of the mutual promises and covenants contained herein and in the Agreement and for other good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, the parties hereby agree as follows:

1.          Recitals; Defined Terms. The parties hereby acknowledge and agree that Recital A is true and accurate. Terms not otherwise defined herein shall have the meaning ascribed to them in the Agreement.

2.          Amendments to Schedule A to the Agreement. The patents and patent applications of Appendix A below are hereby added to Schedule A of the Agreement (in the case of entries which are co-owned, CSMC’s undivided interest is added to Schedule A).

3.          Co-Owned Patent Rights. With respect to the Patent Rights that are co-owned by the parties (including the patents and patent applications listed in Appendix A below), Licensee shall be obligated to pay CSMC a Royalty (as such term is defined in the Agreement) for the duration of the term of the Agreement (as outlined in Section 6.1), regardless of co-ownership of the Patent Rights between the parties and any early termination of the Agreement in accordance with Section 6.2(f) of the Agreement.

4.          Other Provisions. This Fourth Amendment is a revision to the Agreement only; it is not a novation thereof. Except as otherwise provided herein, the terms and conditions of the Agreement shall remain in full force and effect.

5.          Further Assurances. Each of the parties hereto shall execute such further documents and instruments, and do all such further acts, as may be necessary or required in order to effectuate the intent and accomplish the purposes of this Fourth Amendment.

6.          Counterparts. This Fourth Amendment may be executed in any number of counterparts, each of which shall be deemed an original, but all of which taken together shall constitute one and the same instrument.

[Remainder of Page Intentionally Left Blank]

WITNESS WHEREOF, the parties have executed this Fourth Amendment to Exclusive License Agreement as of the Fourth Amendment Date.

Appendix A