UNITED STATES

SECURITIES AND EXCHANGE

COMMISSION

Washington, D.C. 20549

Under the Securities Exchange Act of 1934

(Amendment No. __)

KRONOS BIO, INC.

(Name of Issuer)

Common Stock

(Title of Class of Securities)

50107A104

(CUSIP Number)

December 31, 2020

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

* The remainder of this cover page shall be filled out for a reporting person’s initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter the disclosures provided in a prior cover page.

The information required in the remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934 (“Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

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1	NAMES OF REPORTING PERSONS
	Norbert Bischofberger, Ph.D.
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
	(a)☐
	(b)☐
3	SEC USE ONLY
4	CITIZENSHIP OR PLACE OF ORGANIZATION
	United States of America
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH		5	SOLE VOTING POWER
			495,310 (1)
		6	SHARED VOTING POWER
			5,425,494 Shares (2)
		7	SOLE DISPOSITIVE POWER
			495,310 (1)
		8	SHARED DISPOSITIVE POWER
			5,425,494 Shares (2)
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
	5,920,804 Shares
10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)
	☐
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
	10.6% (3)
12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)
	IN

(1)       Includes 297,186 shares of common stock issuable within 60 days of December 31, 2020 upon the exercise of stock options held by the Reporting Person.

(2)      Includes (a) 4,370,494 shares of common stock beneficially owned by the Norbert W. & Inger A. Bischofberger Revocable Inter Vivos Trust, dtd August 29, 1994, of which Dr. Bischofberger is a trustee, (b) 263,750 shares of common stock beneficially owned by Norbert W. Bischofberger and Inger A. Bischofberger, Trustees of the David Michael Anthony Dynasty GST Exempt Trust dated April 29, 2020, of which Dr. Bischofberger is a trustee, (c) 263,750 shares of common stock beneficially owned by Norbert W. Bischofberger and Inger A. Bischofberger, Trustees of the David Michael Anthony Dynasty GST Non-Exempt Trust dated April 29, 2020, of which Dr. Bischofberger is a trustee, (d) 263,750 shares of common stock beneficially owned by Norbert W. Bischofberger and Inger A. Bischofberger, Trustees of the Irene Alisha Bischofberger Dynasty GST Exempt Trust dated April 29, 2020, of which Dr. Bischofberger is a trustee and (e) 263,750 shares of common stock beneficially owned by Norbert W. Bischofberger and Inger A. Bischofberger, Trustees of the Irene Alisha Bischofberger Dynasty GST Non-Exempt Trust dated April 29, 2020, of which Dr. Bischofberger is a trustee.

(3)      This percentage is calculated based on 56,033,504 shares of common stock outstanding as of November 16, 2020, as reported in the Issuer’s Quarterly Report on Form 10-Q filed on November 18, 2020.

1	NAMES OF REPORTING PERSONS
	Norbert W. & Inger A. Bischofberger Revocable Inter Vivos Trust, dtd August 29, 1994
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
	(a)☐
	(b)☐
3	SEC USE ONLY
4	CITIZENSHIP OR PLACE OF ORGANIZATION
	California
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH		5	SOLE VOTING POWER
			4,370,494 Shares
		6	SHARED VOTING POWER
			0 Shares
		7	SOLE DISPOSITIVE POWER
			4,370,494 Shares
		8	SHARED DISPOSITIVE POWER
			0 Shares
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
	4,370,494 Shares
10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)
	☐
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
	7.8% (1)
12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)
	OO

1	NAMES OF REPORTING PERSONS
	Norbert W. Bischofberger and Inger A. Bischofberger, Trustees of the David Michael Anthony Dynasty GST Exempt Trust dated April 29, 2020
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
	(a)☐
	(b)☐
3	SEC USE ONLY
4	CITIZENSHIP OR PLACE OF ORGANIZATION
	California
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH		5	SOLE VOTING POWER
			263,750 Shares
		6	SHARED VOTING POWER
			0 Shares
		7	SOLE DISPOSITIVE POWER
			263,750 Shares
		8	SHARED DISPOSITIVE POWER
			0 Shares
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
	263,750 Shares
10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)
	☐
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
	0.4% (1)
12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)
	OO

1	NAMES OF REPORTING PERSONS
	Norbert W. Bischofberger and Inger A. Bischofberger, Trustees of the David Michael Anthony Dynasty GST Non-Exempt Trust dated April 29, 2020
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
	(a)☐
	(b)☐
3	SEC USE ONLY
4	CITIZENSHIP OR PLACE OF ORGANIZATION
	California
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH		5	SOLE VOTING POWER
			263,750 Shares
		6	SHARED VOTING POWER
			0 Shares
		7	SOLE DISPOSITIVE POWER
			263,750 Shares
		8	SHARED DISPOSITIVE POWER
			0 Shares
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
	263,750 Shares
10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)
	☐
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
	0.4% (1)
12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)
	OO

1	NAMES OF REPORTING PERSONS
	Norbert W. Bischofberger and Inger A. Bischofberger, Trustees of the Irene Alisha Bischofberger Dynasty GST Exempt Trust dated April 29, 2020
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
	(a)☐
	(b)☐
3	SEC USE ONLY
4	CITIZENSHIP OR PLACE OF ORGANIZATION
	California
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH		5	SOLE VOTING POWER
			263,750 Shares
		6	SHARED VOTING POWER
			0 Shares
		7	SOLE DISPOSITIVE POWER
			263,750 Shares
		8	SHARED DISPOSITIVE POWER
			0 Shares
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
	263,750 Shares
10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)
	☐
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
	0.4% (1)
12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)
	OO

1	NAMES OF REPORTING PERSONS
	Norbert W. Bischofberger and Inger A. Bischofberger, Trustees of the Irene Alisha Bischofberger Dynasty GST Non-Exempt Trust dated April 29, 2020
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
	(a)☐
	(b)☐
3	SEC USE ONLY
4	CITIZENSHIP OR PLACE OF ORGANIZATION
	California
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH		5	SOLE VOTING POWER
			263,750 Shares
		6	SHARED VOTING POWER
			0 Shares
		7	SOLE DISPOSITIVE POWER
			263,750 Shares
		8	SHARED DISPOSITIVE POWER
			0 Shares
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
	263,750 Shares
10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)
	☐
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
	0.4% (1)
12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)
	OO

(1)      This percentage is calculated based on 56,033,504 shares of common stock outstanding as of November 16, 2020, as reported in the Issuer’s Quarterly Report on Form 10-Q filed on November 18, 2020.

Item 1(a).	Name of Issuer:
	Kronos Bio, Inc.

Item 1(b).	Address of Issuer’s Principal Executive Offices:
	1300 So. El Camino Real, Suite 300
	San Mateo, California 94402
Item 2(a).	Names of Persons Filing:

	Norbert Bischofberger, Ph.D.
	Norbert W. & Inger A. Bischofberger Revocable Inter Vivos Trust, dtd August 29, 1994
	Norbert W. Bischofberger and Inger A. Bischofberger, Trustees of the David Michael Anthony Dynasty GST Exempt Trust dated April 29, 2020
	Norbert W. Bischofberger and Inger A. Bischofberger, Trustees of the David Michael Anthony Dynasty GST Non-Exempt Trust dated April 29, 2020
	Norbert W. Bischofberger and Inger A. Bischofberger, Trustees of the Irene Alisha Bischofberger Dynasty GST Exempt Trust dated April 29, 2020
	Norbert W. Bischofberger and Inger A. Bischofberger, Trustees of the Irene Alisha Bischofberger Dynasty GST Non-Exempt Trust dated April 29, 2020

	Norbert Bischofberger, Ph.D.:  USA
	Norbert W. & Inger A. Bischofberger Revocable Inter Vivos Trust, dtd August 29, 1994:  California
	Norbert W. Bischofberger and Inger A. Bischofberger, Trustees of the David Michael Anthony Dynasty GST Exempt Trust dated April 29, 2020:  California
	Norbert W. Bischofberger and Inger A. Bischofberger, Trustees of the David Michael Anthony Dynasty GST Non-Exempt Trust dated April 29, 2020:  California
	Norbert W. Bischofberger and Inger A. Bischofberger, Trustees of the Irene Alisha Bischofberger Dynasty GST Exempt Trust dated April 29, 2020:  California
	Norbert W. Bischofberger and Inger A. Bischofberger, Trustees of the Irene Alisha Bischofberger Dynasty GST Non-Exempt Trust dated April 29, 2020:  California

Item 2(d).	Title of Class of Securities:
	Common Stock
Item 2(e).	CUSIP No.:
	50107A104
Item 3.	Not Applicable.
Item 4.	Ownership

The information requested hereinafter is set forth in items 5 through 9 and 11 of the cover page to this Schedule 13G.  Ownership is stated as of December 31, 2020.  This percentage is calculated based on 56,033,504 shares of common stock outstanding as of November 16, 2020, as reported in the Issuer’s Quarterly Report on Form 10-Q filed on November 18, 2020.

(1)      This percentage is calculated based on 56,033,504 shares of common stock outstanding as of November 16, 2020, as reported in the Issuer’s Quarterly Report on Form 10-Q filed on November 18, 2020.

If this statement is being filed to report the fact that as of the date hereof, the Reporting Persons have ceased to be the beneficial owner of more than five percent of the class of securities, check the following: ☐

Not applicable

Not applicable

Not applicable

Not applicable

By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect.

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Dated: April 28, 2021

Exhibit 99.1

JOINT FILING AGREEMENT

In accordance with Rule 13d-1(k) promulgated under the Securities Exchange Act of 1934, as amended, the undersigned hereby agree to the joint filing with all other Reporting Persons (as such term is defined in the Schedule 13G referred to below) on behalf of each of them of a statement on Schedule 13G (including amendments thereto) with respect to the common stock of Kronos Bio, Inc., a Delaware corporation, and that this Agreement may be included as an Exhibit to such joint filing. This Agreement may be executed in any number of counterparts all of which, taken together, shall constitute one and the same instrument.

Dated: April 28, 2021

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