Exhibit 99.4

JOINT FILING AGREEMENT

The undersigned hereby agree that they are filing this statement jointly pursuant to Rule 13d-1(k)(1). Each of them is responsible for the timely filing of such Schedule 13D and any amendments thereto, and for the completeness and accuracy of the information concerning such person contained therein; but none of them is responsible for the completeness or accuracy of the information concerning the other persons making the filing, unless such person knows or has reason to believe that such information is inaccurate.

In accordance with Rule 13d-1(k)(1) promulgated under the Securities Exchange Act of 1934, as amended, the undersigned hereby agree to the joint filing with each other on behalf of each of them of such a statement on Schedule 13D with respect to the common stock of Decibel Therapeutics, Inc. This Joint Filing Agreement shall be included as an exhibit to such Schedule 13D.

IN WITNESS WHEREOF, the undersigned hereby execute this Joint Filing Agreement as of the 18th day of August, 2023.

Date:  August 18, 2023	REGENERON PHARMACEUTICALS, iNC.
	By:	/s/ Nouhad Husseini
	Name:	Nouhad Husseini
	Title:	Senior Vice President, Business Development and Corporate Strategy

Date:  August 18, 2023	SYMPHONY ACQUISITION SUB, INC.
	By:	/s/ Nouhad Husseini
	Name:	Nouhad Husseini
	Title:	Managing Director