Sec Form 4 Filing - NMSIC Co-Investment Fund, L.P. @ EXAGEN INC. - 2019-09-19

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person NMSIC Co-Investment Fund, L.P. 2. Issuer Name and Ticker or Trading Symbol EXAGEN INC. [ XGN] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director X __ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) 527 DON GASPAR AVENUE 3. Date of Earliest Transaction (MM/DD/YY) 09/19/2019 (Street) SANTA FE, NM87505 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) _____ Form filed by One Reporting Person __ X __ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock 09/19/2019 X 349,823 A $ 1.84 361,897 I See footnote ( 1 ) Common Stock 09/19/2019 X 19,825 A $ 14.3235 381,722 I See footnote ( 1 ) Common Stock 09/19/2019 F 49,860 D $ 18.58 331,862 I See footnote ( 1 ) Common Stock 09/23/2019 C 2,228,500 A $ 0 2,560,362 I See footnote ( 1 )

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares Warrants $ 1.84 09/19/2019 C 280,127 ( 2 ) ( 2 ) Common Stock 280,127 $ 1.84 0 I See footnotes ( 1 ) ( 6 ) Warrants $ 1.84 09/19/2019 C 69,696 ( 3 ) ( 3 ) Common Stock 69,696 $ 1.84 0 I See footnotes ( 1 ) ( 6 ) Warrants $ 14.3235 09/19/2019 X 19,825 ( 4 ) ( 4 ) Common Stock 19,825 ( 5 ) $ 14.3235 0 I See footnotes ( 1 ) ( 6 ) Series A-3 Redeemable Convertible Preferred Stock ( 5 ) 09/23/2019 C 607,168 ( 7 ) ( 7 ) Common Stock 3,306 ( 7 ) 0 I See footnotes ( 1 ) ( 8 ) Series C Redeemable Convertible Preferred Stock ( 7 ) 09/23/2019 C 8,081,136 ( 9 ) ( 9 ) Common Stock 141,046 ( 9 ) 0 I See footnotes ( 1 ) ( 8 ) Series D Redeemable Convertible Preferred Stock ( 8 ) 09/23/2019 C 3,373,594 ( 10 ) ( 10 ) Common Stock 58,882 ( 10 ) 0 I See footnotes ( 1 ) ( 8 ) Series E Redeemable Convertible Preferred Stock ( 9 ) 09/23/2019 C 64,239,884 ( 11 ) ( 11 ) Common Stock 1,121,230 ( 11 ) 0 I See footnotes ( 1 ) ( 12 ) Series F Redeemable Convertible Preferred Stock ( 11 ) 09/23/2019 C 112,958,220 ( 13 ) ( 13 ) Common Stock 615,123 ( 13 ) 0 I See footnotes ( 1 ) ( 6 ) Series H Redeemable Convertible Preferred Stock ( 12 ) 09/23/2019 C 53,054,485 ( 14 ) ( 14 ) Common Stock 288,913 ( 14 ) 0 I See footnotes ( 1 ) ( 6 )

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other NM SIC Co-Investment Fund, L.P. 527 DON GASPAR AVENUE SANTA FE, NM87505 X NMSIC Focused LLC 527 DON GASPAR AVENUE SANTA FE, NM87505 X Sun Mountain Capital Partners LLC 527 DON GASPAR AVENUE SANTA FE, NM87505 X Signatures NMSIC Co-Investment Fund, L.P., By: Sun Mountain Capital Partners LLC, its general partner,/s/ Brian Birk, Name: Brian Birk, Title: Managing Partner, /s/ Lee Rand, Name: Lee Rand, Title: Managing Member 09/23/2019 Signature of Reporting Person Date NMSIC Focused, LLC, By: NMSIC Co-Investment Fund, L.P., its sole member, By: Sun Mountain Capital Partners LLC, its general partner, /s/ Brian Birk, Name: Brian Birk, Title: Managing Partner, /s/ Lee Rand, Name: Lee Rand, Title: Managing Member 09/23/2019 Signature of Reporting Person Date Sun Mountain Capital Partners LLC, /s/ Brian Birk, Name: Brian Birk, Title: Managing Partner, /s/ Lee Rand, Name: Lee Rand, Title: Managing Member 09/23/2019 Signature of Reporting Person Date

Explanation of Responses:

( 1 )The shares reported on this form are held of record by NMSIC Co-Investment Fund, L.P. ("NMSIC") and NMSIC Focused, LLC ("NMSIC Focused"). NMSIC is the sole member of NMSIC Focused. Sun Mountain Capital Partners LLC ("Sun Mountain") is the general partner of NMSIC. The controlling members of Sun Mountain are Brian Birk, Sally Coming and Lee Rand. As such, each of these entities and individuals may be deemed to share beneficial ownership of the shares held of record by NMSIC and NMSIC Focused. Each of Sun Mountain, Mr. Birk, Ms. Coming and Mr. Rand disclaims beneficial ownership of the securities held of record by NMSIC and NMSIC Focused. ( 2 )The warrants are currently exercisable and will expire on January 19, 2026. ( 3 )The warrants are currently exercisable and will expire on March 31, 2026. ( 4 )The warrants are currently exercisable and will terminate upon closing of the Issuer's initial public offering. ( 5 )Represents warrants that previously entitled the holders to purchase Series E Redeemable Convertible Preferred Stock, which, pursuant to their terms, were settled in shares of the Issuer's Common Stock. ( 6 )Represents securities held of record by NMSIC Focused. ( 7 )The Series A-3 Redeemable Convertible Preferred Stock (the "Series A-3") is convertible into the Issuer's Common Stock on a 183.635-for-one basis at the holder's election and has no expiration date. The Series A-3 automatically converted into Common Stock upon the closing of the Issuer's initial public offering. ( 8 )Represents securities held of record by NMSIC. ( 9 )The Series C Redeemable Convertible Preferred Stock (the "Series C") is convertible into the Issuer's Common Stock on a 57.294-for-one basis at the holder's election and has no expiration date. The Series C automatically converted into Common Stock upon the closing of the Issuer's initial public offering. ( 10 )The Series D Redeemable Convertible Preferred Stock (the "Series D") is convertible into the Issuer's Common Stock on a 57.294-for-one basis at the holder's election and has no expiration date. The Series D automatically converted into Common Stock upon the closing of the Issuer's initial public offering. ( 11 )The Series E Redeemable Convertible Preferred Stock (the "Series E") is convertible into the Issuer's Common Stock on a 57.294-for-one basis at the holder's election and has no expiration date. The Series E automatically converted into Common Stock upon the closing of the Issuer's initial public offering. ( 12 )Includes 448,921 and 672,308 shares of common stock underlying the Series E shares held by NMSIC and NMSIC Focused, respectively. ( 13 )The Series F Redeemable Convertible Preferred Stock ("Series F") is convertible into the Issuer's Common Stock on a 183.635-for-one basis at the holder's election and has no expiration date. The Series F automatically converted into Common Stock upon the closing of the Issuer's initial public offering. ( 14 )The Series H Redeemable Convertible Preferred Stock ("Series H") is convertible into the Issuer's Common Stock on a 183.635-for-one basis at the holder's election and has no expiration date. The Series H automatically converted into Common Stock upon the closing of the Issuer's initial public offering.

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).

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