Sec Form 4 Filing - CEDARS SINAI MEDICAL CENTER @ Prometheus Biosciences, Inc. - 2021-03-16

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 CEDARS SINAI MEDICAL CENTER 2. Issuer Name and Ticker or Trading Symbol Prometheus Biosciences, Inc. [ RXDX] 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) 8700 BEVERLY BLVD. 3. Date of Earliest Transaction (MM/DD/YY) 03/16/2021 (Street) LOS ANGELES, CA90048 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 03/16/2021 C 100,000 A 692,500 D Common Stock 03/16/2021 C 1,200,000 A 1,892,500 D Common Stock 03/16/2021 C 2,500,000 A 4,392,500 D Common Stock 03/16/2021 C 254,442 A 4,646,942 D Common Stock 03/16/2021 C 361,566 A 5,008,508 D

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 Series A Preferred Stock ( 1 ) 03/16/2021 C 1,000,000 ( 1 ) ( 1 ) Common Stock 100,000 ( 1 ) 0 D Series B Preferred Stock ( 2 ) 03/16/2021 C 12,000,000 ( 2 ) ( 2 ) Common Stock 1,200,000 ( 2 ) 0 D Series C Preferred Stock ( 3 ) 03/16/2021 C 25,000,000 ( 3 ) ( 3 ) Common Stock 2,500,000 ( 3 ) 0 D Series D-1 Preferred Stock ( 4 ) 03/16/2021 C 2,544,425 ( 4 ) ( 4 ) Common Stock 254,442 ( 4 ) 0 D Series D-2 Preferred Stock ( 5 ) 03/16/2021 C 3,615,656 ( 5 ) ( 5 ) Common Stock 361,566 ( 5 ) 0 D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other CEDARS SINAI MEDICAL CENTER 8700 BEVERLY BLVD. LOS ANGELES, CA90048 X Signatures /s/ James Laur, Vice President, Intellectual Property 03/16/2021 Signature of Reporting Person Date

Explanation of Responses:

( 1 )The shares of the Issuer's Series A Preferred Stock automatically converted into shares of the Issuer's common Stock, for no additional consideration, at a ratio of ten-for-one share, immediately prior to the consummation of the Issuer's initial public offering. ( 2 )The shares of the Issuer's Series B Preferred Stock automatically converted into shares of the Issuer's common Stock, for no additional consideration, at a ratio of ten-for-one share, immediately prior to the consummation of the Issuer's initial public offering. ( 3 )The shares of the Issuer's Series C Preferred Stock automatically converted into shares of the Issuer's common Stock, for no additional consideration, at a ratio of ten-for-one share, immediately prior to the consummation of the Issuer's initial public offering. ( 4 )The shares of the Issuer's Series D-1 Preferred Stock automatically converted into shares of the Issuer's common Stock, for no additional consideration, at a ratio of ten-for-one share, immediately prior to the consummation of the Issuer's initial public offering. ( 5 )The shares of the Issuer's Series D-2 Preferred Stock automatically converted into shares of the Issuer's common Stock, for no additional consideration, at a ratio of ten-for-one share, immediately prior to the consummation 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).

** 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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