Sana Biotechnology (SANA) SC 13G/A Sana Biotechnology / Flagship Ventures Fund V ownership change

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

SCHEDULE 13G

Under the Securities Exchange Act of 1934

(Amendment No. 1)*

Sana Biotechnology, Inc.

(Name of Issuer)

Common Stock, $0.0001 par value per share

(Title of Class of Securities)

799566104

(CUSIP Number)

December 31, 2023

(Date of Event Which Requires Filing of this Statement)

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

☐ Rule 13d-1(b)

☐ Rule 13d-1(c)

☒ Rule 13d-1(d)

* 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).

CUSIP No. 799566104 Page 2 of 14 Pages

1	NAMES OF REPORTING PERSONS  I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)  Flagship V VentureLabs Rx Fund, L.P.
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS)  (a) ☐  (b) ☒
3	SEC USE ONLY
4	CITIZENSHIP OR PLACE OF ORGANIZATION  Delaware

NUMBER OF SHARES  BENEFICIALLY  OWNED BY EACH REPORTING PERSON WITH:	5	SOLE VOTING POWER  0
	6	SHARED VOTING POWER  1,035,208
	7	SOLE DISPOSITIVE POWER  0
	8	SHARED DISPOSITIVE POWER  1,035,208

9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON  1,035,208
10	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)  ☐
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9  0.5%
12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)  PN

CUSIP No. 799566104 Page 3 of 14 Pages

1	NAMES OF REPORTING PERSONS  I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)  Flagship Ventures Fund V, L.P.
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS)  (a) ☐  (b) ☒
3	SEC USE ONLY
4	CITIZENSHIP OR PLACE OF ORGANIZATION  Delaware

NUMBER OF SHARES  BENEFICIALLY  OWNED BY EACH REPORTING PERSON WITH:	5	SOLE VOTING POWER  0
	6	SHARED VOTING POWER  8,057,470
	7	SOLE DISPOSITIVE POWER  0
	8	SHARED DISPOSITIVE POWER  8,057,470

9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON  8,057,470
10	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)  ☐
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9  4.1%
12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)  PN

CUSIP No. 799566104 Page 4 of 14 Pages

1	NAMES OF REPORTING PERSONS  I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)  Flagship Ventures Fund V General Partner LLC
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS)  (a) ☐  (b) ☒
3	SEC USE ONLY
4	CITIZENSHIP OR PLACE OF ORGANIZATION  Delaware

NUMBER OF SHARES  BENEFICIALLY  OWNED BY EACH REPORTING PERSON WITH:	5	SOLE VOTING POWER  0
	6	SHARED VOTING POWER  9,092,678
	7	SOLE DISPOSITIVE POWER  0
	8	SHARED DISPOSITIVE POWER  9,092,678

9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON  9,092,678
10	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)  ☐
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9  4.6%
12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)  OO

CUSIP No. 799566104 Page 5 of 14 Pages

1	NAMES OF REPORTING PERSONS  I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)  Flagship VentureLabs V LLC
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS)  (a) ☐  (b) ☒
3	SEC USE ONLY
4	CITIZENSHIP OR PLACE OF ORGANIZATION  Delaware

NUMBER OF SHARES  BENEFICIALLY  OWNED BY EACH REPORTING PERSON WITH:	5	SOLE VOTING POWER  0
	6	SHARED VOTING POWER  8,615,337
	7	SOLE DISPOSITIVE POWER  0
	8	SHARED DISPOSITIVE POWER  8,615,337

9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON  8,615,337
10	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)  ☐
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9  4.4%
12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)  OO

CUSIP No. 799566104 Page 6 of 14 Pages

1	NAMES OF REPORTING PERSONS  I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)  VentureLabs V Manager LLC
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS)  (a) ☐  (b) ☒
3	SEC USE ONLY
4	CITIZENSHIP OR PLACE OF ORGANIZATION  Delaware

NUMBER OF SHARES  BENEFICIALLY  OWNED BY EACH REPORTING PERSON WITH:	5	SOLE VOTING POWER  0
	6	SHARED VOTING POWER  8,615,337
	7	SOLE DISPOSITIVE POWER  0
	8	SHARED DISPOSITIVE POWER  8,615,337

9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON  8,615,337
10	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)  ☐
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9  4.4%
12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)  OO

CUSIP No. 799566104 Page 7 of 14 Pages

1	NAMES OF REPORTING PERSONS  I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)  Flagship Pioneering Fund VI, L.P.
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS)  (a) ☐  (b) ☒
3	SEC USE ONLY
4	CITIZENSHIP OR PLACE OF ORGANIZATION  Delaware

NUMBER OF SHARES  BENEFICIALLY  OWNED BY EACH REPORTING PERSON WITH:	5	SOLE VOTING POWER  0
	6	SHARED VOTING POWER  7,293,841
	7	SOLE DISPOSITIVE POWER  0
	8	SHARED DISPOSITIVE POWER  7,293,841

9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON  7,293,841
10	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)  ☐
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9  3.7%
12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)  PN

CUSIP No. 799566104 Page 8 of 14 Pages

1	NAMES OF REPORTING PERSONS  I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)  Flagship Pioneering Fund VI General Partner LLC
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS)  (a) ☐  (b) ☒
3	SEC USE ONLY
4	CITIZENSHIP OR PLACE OF ORGANIZATION  Delaware

NUMBER OF SHARES  BENEFICIALLY  OWNED BY EACH REPORTING PERSON WITH:	5	SOLE VOTING POWER  0
	6	SHARED VOTING POWER  7,293,841
	7	SOLE DISPOSITIVE POWER  0
	8	SHARED DISPOSITIVE POWER  7,293,841

9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON  7,293,841
10	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)  ☐
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9  3.7%
12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)  OO

CUSIP No. 799566104 Page 9 of 14 Pages

1	NAMES OF REPORTING PERSONS  I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)  Flagship Pioneering, Inc.
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS)  (a) ☐  (b) ☒
3	SEC USE ONLY
4	CITIZENSHIP OR PLACE OF ORGANIZATION  Delaware

NUMBER OF SHARES  BENEFICIALLY  OWNED BY EACH REPORTING PERSON WITH:	5	SOLE VOTING POWER  0
	6	SHARED VOTING POWER  15,909,178
	7	SOLE DISPOSITIVE POWER  0
	8	SHARED DISPOSITIVE POWER  15,909,178

9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON  15,909,178
10	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)  ☐
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9  8.1%
12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)  CO

CUSIP No. 799566104 Page 10 of 14 Pages

1	NAMES OF REPORTING PERSONS  I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)  Noubar B. Afeyan, Ph.D.
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS)  (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  581,695 (1)
	6	SHARED VOTING POWER  25,001,856
	7	SOLE DISPOSITIVE POWER  581,695 (1)
	8	SHARED DISPOSITIVE POWER  25,001,856

9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON  25,583,551
10	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)  ☐
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9  13.0%
12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)  IN

(1) Consists of (i) 21,641 shares held directly by Dr. Afeyan, (ii) 20,606 shares held through a trust for the benefit of Dr. Afeyan’s children and (iii) 539,448 shares held by VENBA Holdings LLC, an estate planning entity of which Dr. Afeyan is the sole manager.

CUSIP No. 799566104 Page 11 of 14 Pages

Item 1(a). Name of Issuer:

Sana Biotechnology, Inc. (the “Issuer”)

Item 1(b). Address of Issuer’s Principal Executive Offices:

188 East Blaine Street, Sute 400

Seattle, WA 98102

Item 2(a). Names of Persons Filing:

The names of the persons filing this report (collectively, the “Reporting Persons”) are:

Flagship V VentureLabs Rx Fund, L.P. (“Flagship Fund V Rx”)

Flagship Ventures Fund V, L.P. (“Flagship Fund V”)

Flagship Ventures Fund V General Partner LLC (“Flagship V GP”)

Flagship VentureLabs V LLC (“VentureLabs V”)

VentureLabs V Manager LLC (“VentureLabs V Manager”)

Flagship Pioneering Fund VI, L.P. (“Flagship Fund VI”)

Flagship Pioneering Fund VI General Partner LLC (“Flagship Fund VI GP”)

Flagship Pioneering, Inc. (“Flagship Pioneering”)

Noubar B. Afeyan, Ph.D. (“Dr. Afeyan”)

Item 2(b). Address of Principal Business Office or, if None, Residence:

The address of the principal business office of each of the Reporting Persons is:

c/o Flagship Pioneering Inc.

55 Cambridge Parkway, Suite 800E

Cambridge, Massachusetts 02142

Item 2(c). Citizenship:

Flagship Fund V Rx	Delaware
Flagship Fund V	Delaware
Flagship V GP	Delaware
VentureLabs V	Delaware
VentureLabs V Manager	Delaware
Flagship Fund VI	Delaware
Flagship Fund VI GP	Delaware
Flagship Pioneering	Delaware
Dr. Afeyan	United States of America

Item 2(d). Title of Class of Securities:

Common Stock, $0.0001 par value per share (“Common Stock”).

Item 2(e). CUSIP Number:

799566104

CUSIP No. 799566104 Page 12 of 14 Pages

Item 3. If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:

Not applicable.

Item 4. Ownership.

The information required by this item with respect to each Reporting Person is set forth in Rows 5 through 9 and 11 of the cover page to this Schedule 13G. The ownership percentages reported are based on 197,133,208 shares of Common Stock outstanding as of October 31, 2023, as reported by the Issuer in its Quarterly Report on Form 10-Q filed with the Securities and Exchange Commission on November 8, 2023.

Flagship V GP is the general partner of each of Flagship Fund V and Flagship Fund V Rx, and, as such, may be deemed to beneficially own the shares held directly by each of Flagship Fund V and Flagship Fund V Rx.

VentureLabs V Manager is the manager of VentureLabs V, and, as such, may be deemed to beneficially own the shares held directly by VentureLabs V.

Flagship Fund VI GP is the general partner of Flagship Fund VI and, as such, may be deemed to beneficially own the shares held directly by Flagship Fund VI.

Flagship Pioneering is the manager of each of VentureLabs V Manager and Flagship Fund VI GP and, as such, may be deemed to beneficially own the shares beneficially owned by each of VentureLabs V Manager and Flagship Fund VI GP.

Dr. Afeyan is the sole manager of Flagship Fund V GP and the Chief Executive Officer, sole stockholder and director of Flagship Pioneering and, as such, may be deemed to beneficially own shares beneficially owned by each of Flagship Fund V GP and Flagship Pioneering.

Item 5. Ownership of Five Percent or Less of a Class.

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 ☐.

Item 6. Ownership of More than Five Percent on Behalf of Another Person.

Not applicable.

Item 7. Identification and Classification of the SubsidiaryWhich Acquired the Security Being Reported on by the Parent Holding Company or Control Person.

Not applicable.

Item 8. Identification and Classification of Members of the Group.

Not applicable.

Item 9. Notice of Dissolution of Group.

Not applicable.

Item 10. Certification.

Not applicable.

Material Filed as Exhibits.

CUSIP No. 799566104 Page 13 of 14 Pages

SIGNATURE

After reasonable inquiry and to the best of its knowledge and belief, each of the undersigned certifies that the information set forth in this statement is true, complete and correct.

Date: February 14, 2024

FLAGSHIP V VENTURELABS RX FUND, L.P.
By:	Flagship Ventures Fund V General Partner LLC
	General Partner
	By:	/s/ Noubar B. Afeyan, Ph.D.
		Noubar B. Afeyan, Ph.D.
		Manager
FLAGSHIP VENTURES FUND V, L.P.
By:	Flagship Ventures Fund V General Partner LLC
	General Partner
	By:	/s/ Noubar B. Afeyan, Ph.D.
		Noubar B. Afeyan, Ph.D.
		Manager
FLAGSHIP VENTURES FUND V GENERAL PARTNER LLC
	By:	/s/ Noubar B. Afeyan, Ph.D.
		Noubar B. Afeyan, Ph.D.
		Manager
FLAGSHIP VENTURELABS V LLC
By:	VentureLabs V Manager LLC General Partner
	By: Flagship Pioneering, Inc., Manager
	By:	/s/ Noubar B. Afeyan, Ph.D.
		Noubar B. Afeyan, Ph.D.
		Chief Executive Officer

CUSIP No. 799566104 Page 14 of 14 Pages

VENTURELABS V MANAGER LLC
By:	Flagship Pioneering, Inc. Manager
	By:	/s/ Noubar B. Afeyan, Ph.D.
		Noubar B. Afeyan, Ph.D.
		Chief Executive Officer
FLAGSHIP PIONEERING FUND VI, L.P.
By:	Flagship Pioneering Fund VI General Partner, LLC General Partner
	By:	Flagship Pioneering, Inc. Manager
	By:	/s/ Noubar B. Afeyan, Ph.D.
		Noubar B. Afeyan, Ph.D. Chief Executive Officer
FLAGSHIP PIONEERING FUND VI GENERAL PARTNER, LLC
By: Flagship Pioneering, Inc. Manager
	By:	/s/ Noubar B. Afeyan, Ph.D.
		Noubar B. Afeyan, Ph.D. Chief Executive Officer
FLAGSHIP PIONEERING, INC.
	By:	/s/ Noubar B. Afeyan, Ph.D.
		Noubar B. Afeyan, Ph.D.
		Chief Executive Officer
	/s/ Noubar B. Afeyan, Ph.D.
	Noubar B. Afeyan, Ph.D.