Sec Form 4 Filing - PAPA JOSEPH C @ Prometheus Biosciences, Inc. - 2023-06-16

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 PAPA JOSEPH C 2. Issuer Name and Ticker or Trading Symbol Prometheus Biosciences, Inc. [ RXDX] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X __ Director _____ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) C/O PROMETHEUS BIOSCIENCES, INC., 3050 SCIENCE PARK ROAD 3. Date of Earliest Transaction (MM/DD/YY) 06/16/2023 (Street) SAN DIEGO, CA92121 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) __ X __ Form filed by One Reporting Person _____ 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 06/16/2023 D 7,278 ( 1 ) D 0 D Common Stock 06/16/2023 D 10,000 D 0 I By The Papa Family Charitable Trust ( 4 )

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 Stock Option (right to buy) $ 3.1 06/16/2023 D 15,000 ( 2 )( 3 ) 08/24/2030 Common Stock 15,000 ( 2 ) ( 3 ) 0 D Stock Option (right to buy) $ 3.7 06/16/2023 D 27,340 ( 2 )( 3 ) 12/17/2030 Common Stock 27,340 ( 2 ) ( 3 ) 0 D Stock Option (right to buy) $ 6.7 06/16/2023 D 22,652 ( 2 )( 3 ) 02/03/2031 Common Stock 22,652 ( 2 ) ( 3 ) 0 D Stock Option (right to buy) $ 36.32 06/16/2023 D 2,165 ( 2 )( 3 ) 11/13/2031 Common Stock 2,165 ( 2 ) ( 3 ) 0 D Stock Option (right to buy) $ 29.02 06/16/2023 D 22,551 ( 2 )( 3 ) 05/18/2032 Common Stock 22,551 ( 2 ) ( 3 ) 0 D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other PAPA JOSEPH C C/O PROMETHEUS BIOSCIENCES, INC. 3050 SCIENCE PARK ROAD SAN DIEGO, CA92121 X Signatures /s/ Joseph C. Papa 06/16/2023 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Includes 2,278 restricted stock units. ( 2 )Pursuant to the Agreement and Plan of Merger, dated April 15, 2023, by and among the Issuer, Merck & Co., Inc. ("Merck") and Splash Merger Sub, Inc., the Issuer became a wholly owned subsidiary of Merck upon consummation of the merger (the "Effective Time"). At the Effective Time, (a) each of the Issuer's outstanding shares of common stock was cancelled and automatically converted into the right to receive $200 in cash (the "Merger Consideration"), without interest,... (Continued in Footnote 3) ( 3 )(Continued from Footnote 2) ...(b) each of the Issuer's outstanding restricted stock units ("RSUs") was automatically cancelled and converted into the right to receive an amount in cash equal to the product of (i) the number of shares of the Issuer's common stock underlying such RSU immediately prior to the Effective Time multiplied by (ii) the Merger Consideration, without interest and (c) each of the Issuer's outstanding unexercised stock options, whether vested or unvested, was automatically cancelled and converted into the right to receive an amount in cash, without interest, equal to the product of (i) the number of shares of the Issuer's common stock underlying such option immediately prior to the Effective Time multiplied by (ii) the amount, if any, by which the Merger Consideration exceeded the exercise price per share of such option. ( 4 )The Reporting Person is a Trustee to The Papa Family Charitable Trust.

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).

** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).

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