FIRST ADDENDUM TO STANDARD INDUSTRIAL/COMMERCIAL MULTI-TENANT LEASE - NET DATED FEBRUARY 27, 2020 BY AND BETWEEN RGS PROPERTIES, AS LESSOR AND EXAGEN DIAGNOSTICS, INC., AS LESSEE, FOR THE PREMISES LOCATED AT 1261 LIBERTY WAY, SUITE A, CALIFORNIA....

Exhibit 10.4

FIRST ADDENDUM TO STANDARD INDUSTRIAL/COMMERCIAL MULTI-TENANT LEASE - NET DATED FEBRUARY 27, 2020 BY AND BETWEEN RGS PROPERTIES, AS LESSOR AND EXAGEN DIAGNOSTICS, INC., AS LESSEE, FOR THE PREMISES LOCATED AT 0000 XXXXXXX XXX, XXXXX X, XXXXXXXXXX.

Lessor and Lessee mutually agree to amend the lease as follows:

Parties (1.1):

Lessee has changed their name and shall be referred to as Exagen Inc., a Delaware Corporation

Paragraph 1.3 (Term):

The Lease Term will be extended to the new Expiration Date of April 30, 2027

Paragraph 50 (Rent Schedule):

Base Rent shall be as follows:

Dates			Base Rent
February 1, 2026 - April 30, 2027			$14,750.63 per month

All other terms and conditions of the existing Lease shall remain in full force and effect.

This addendum shall automatically expire if not executed by Lessee on or before Friday October 15, 2021.

AGREED AND ACCEPTED:

LESSOR:						LESSEE:
RGS Properties						Exagen Inc., a Delaware Corporation
By: /s/ Xxxxx Xxxxx						By: /s/ Xxx Xxxxx
By: /s/ Xxxx Xxxxx						Xxx Xxxxx
Date: 10/19/2021						Title: CEO
						Date: 10/12/2021