# EDGAR Filing Document

**Accession Number:** 0001642578
**File Stem:** 0001193125-23-038310
**Filing Date:** 2023-2
**Character Count:** 32060
**Document Hash:** 66c612399a0b2eec9f26b456f88726fd
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001193125-23-038310.hdr.sgml**: 20230214

**ACCESSION NUMBER**: 0001193125-23-038310

**CONFORMED SUBMISSION TYPE**: SC 13G/A

**PUBLIC DOCUMENT COUNT**: 1

**FILED AS OF DATE**: 20230214

**DATE AS OF CHANGE**: 20230214

**GROUP MEMBERS**: FLAGSHIP V VENTURELABS RX FUND, L.P.

**GROUP MEMBERS**: FLAGSHIP VENTURES FUND IV GENERAL PARTNER LLC

**GROUP MEMBERS**: FLAGSHIP VENTURES FUND IV, L.P.

**GROUP MEMBERS**: FLAGSHIP VENTURES FUND IV-RX, L.P.

**GROUP MEMBERS**: FLAGSHIP VENTURES FUND V GENERAL PARTNER LLC

**GROUP MEMBERS**: FLAGSHIP VENTURES FUND V, L.P.

**GROUP MEMBERS**: FLAGSHIP VENTURES OPPORTUNITIES FUND I GENERAL PARTNER LLC

**GROUP MEMBERS**: FLAGSHIP VENTURES OPPORTUNITIES FUND I, L.P.

**GROUP MEMBERS**: NOUBAR B. AFEYAN, PH.D.

**SUBJECT COMPANY**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** Rubius Therapeutics, Inc.
- **CENTRAL INDEX KEY:** 0001709401
- **STANDARD INDUSTRIAL CLASSIFICATION:** BIOLOGICAL PRODUCTS (NO DIAGNOSTIC SUBSTANCES) [2836]
- **IRS NUMBER:** 042688109
- **STATE OF INCORPORATION:** DE
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** SC 13G/A
- **SEC ACT:** 1934 Act
- **SEC FILE NUMBER:** 005-90775
- **FILM NUMBER:** 23626052

**BUSINESS ADDRESS:**
- **STREET 1:** C/O VERDOLINO & LOWEY, P.C.
- **STREET 2:** 124 WASHINGTON STREET, SUITE 101
- **CITY:** FOXBORO
- **STATE:** MA
- **ZIP:** 02035
- **BUSINESS PHONE:** 617-679-9600

**MAIL ADDRESS:**
- **STREET 1:** C/O VERDOLINO & LOWEY, P.C.
- **STREET 2:** 124 WASHINGTON STREET, SUITE 101
- **CITY:** FOXBORO
- **STATE:** MA
- **ZIP:** 02035
**FILED BY**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** Flagship VentureLabs IV, LLC
- **CENTRAL INDEX KEY:** 0001642578
- **IRS NUMBER:** 461974736
- **STATE OF INCORPORATION:** DE
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** SC 13G/A

**BUSINESS ADDRESS:**
- **STREET 1:** 55 CAMBRIDGE PARKWAY, 8TH FLOOR
- **CITY:** CAMBRIDGE
- **STATE:** MA
- **ZIP:** 02143
- **BUSINESS PHONE:** 617-868-1888

**MAIL ADDRESS:**
- **STREET 1:** 55 CAMBRIDGE PARKWAY, 8TH FLOOR
- **CITY:** CAMBRIDGE
- **STATE:** MA
- **ZIP:** 02143

------

------

**UNITED STATES** 

**SECURITIES AND EXCHANGE COMMISSION** 

**WASHINGTON, D.C. 20549** 

------

**SCHEDULE 13G** 

**Under the Securities Exchange Act of 1934** 

**(Amendment No. 3)\*** 

------

## Rubius Therapeutics, Inc.
**(Name of Issuer)** 

**Common Stock, $0.001 par value per share** 

**(Title of Class of Securities)** 

**78116T 10 3** 

**(CUSIP Number)** 

**December 31, 2022** 

**(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).

------

---

| | |
|:---|:---|
| &nbsp;&nbsp;&nbsp; **1** | &nbsp;&nbsp;&nbsp;&nbsp;NAMES OF REPORTING PERSONS<br> &nbsp;&nbsp;&nbsp;&nbsp;I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)<br>&nbsp;&nbsp;&nbsp;&nbsp;Flagship VentureLabs IV LLC |
| &nbsp;&nbsp;&nbsp; **2** | &nbsp;&nbsp;&nbsp;&nbsp;CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS)<br>&nbsp;&nbsp;&nbsp;&nbsp;(a) ☐ (b) ☒ |
| &nbsp;&nbsp;&nbsp; **3** | &nbsp;&nbsp;&nbsp;&nbsp;SEC USE ONLY |
| &nbsp;&nbsp;&nbsp; **4** | &nbsp;&nbsp;&nbsp;&nbsp;CITIZENSHIP OR PLACE OF ORGANIZATION<br>&nbsp;&nbsp;&nbsp;&nbsp;Delaware |

---

---

| | | |
|:---|:---|:---|
| &nbsp;&nbsp;&nbsp; NUMBER OF<br> SHARES<br> BENEFICIALLY <br> OWNED BY<br> EACH<br> REPORTING<br> PERSON<br> WITH: | **5** | &nbsp;&nbsp;&nbsp;&nbsp;SOLE VOTING POWER<br>&nbsp;&nbsp;&nbsp;&nbsp;0 |
| &nbsp;&nbsp;&nbsp; NUMBER OF<br> SHARES<br> BENEFICIALLY <br> OWNED BY<br> EACH<br> REPORTING<br> PERSON<br> WITH: | **6** | &nbsp;&nbsp;&nbsp;&nbsp;SHARED VOTING POWER<br>&nbsp;&nbsp;&nbsp;&nbsp;5,000,000 |
| &nbsp;&nbsp;&nbsp; NUMBER OF<br> SHARES<br> BENEFICIALLY <br> OWNED BY<br> EACH<br> REPORTING<br> PERSON<br> WITH: | **7** | &nbsp;&nbsp;&nbsp;&nbsp;SOLE DISPOSITIVE POWER<br>&nbsp;&nbsp;&nbsp;&nbsp;0 |
| &nbsp;&nbsp;&nbsp; NUMBER OF<br> SHARES<br> BENEFICIALLY <br> OWNED BY<br> EACH<br> REPORTING<br> PERSON<br> WITH: | **8** | &nbsp;&nbsp;&nbsp;&nbsp;SHARED DISPOSITIVE POWER<br>&nbsp;&nbsp;&nbsp;&nbsp;5,000,000 |

---

---

| | |
|:---|:---|
| &nbsp;&nbsp;&nbsp; **9** | &nbsp;&nbsp;&nbsp;&nbsp;AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON<br>&nbsp;&nbsp;&nbsp;&nbsp;5,000,000 |
| &nbsp;&nbsp;&nbsp;**10** | &nbsp;&nbsp;&nbsp;&nbsp;CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)<br>&nbsp;&nbsp;&nbsp;&nbsp;☐ |
| &nbsp;&nbsp;&nbsp;**11** | &nbsp;&nbsp;&nbsp;&nbsp;PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9<br>&nbsp;&nbsp;&nbsp;&nbsp;5.5% |
| &nbsp;&nbsp;&nbsp;**12** | &nbsp;&nbsp;&nbsp;&nbsp;TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)<br>&nbsp;&nbsp;&nbsp;&nbsp;OO |

---

------

---

| | |
|:---|:---|
| &nbsp;&nbsp;&nbsp; **1** | &nbsp;&nbsp;&nbsp;&nbsp;NAMES OF REPORTING PERSONS<br> &nbsp;&nbsp;&nbsp;&nbsp;I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)<br>&nbsp;&nbsp;&nbsp;&nbsp;Flagship Ventures Fund IV, L.P. |
| &nbsp;&nbsp;&nbsp; **2** | &nbsp;&nbsp;&nbsp;&nbsp;CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS)<br>&nbsp;&nbsp;&nbsp;&nbsp;(a) ☐ (b) ☒ |
| &nbsp;&nbsp;&nbsp; **3** | &nbsp;&nbsp;&nbsp;&nbsp;SEC USE ONLY |
| &nbsp;&nbsp;&nbsp; **4** | &nbsp;&nbsp;&nbsp;&nbsp;CITIZENSHIP OR PLACE OF ORGANIZATION<br>&nbsp;&nbsp;&nbsp;&nbsp;Delaware |

---

---

| | | |
|:---|:---|:---|
| &nbsp;&nbsp;&nbsp; NUMBER OF<br> SHARES<br> BENEFICIALLY <br> OWNED BY<br> EACH<br> REPORTING<br> PERSON<br> WITH: | **5** | &nbsp;&nbsp;&nbsp;&nbsp;SOLE VOTING POWER<br>&nbsp;&nbsp;&nbsp;&nbsp;0 |
| &nbsp;&nbsp;&nbsp; NUMBER OF<br> SHARES<br> BENEFICIALLY <br> OWNED BY<br> EACH<br> REPORTING<br> PERSON<br> WITH: | **6** | &nbsp;&nbsp;&nbsp;&nbsp;SHARED VOTING POWER<br>&nbsp;&nbsp;&nbsp;&nbsp;20,393,593 |
| &nbsp;&nbsp;&nbsp; NUMBER OF<br> SHARES<br> BENEFICIALLY <br> OWNED BY<br> EACH<br> REPORTING<br> PERSON<br> WITH: | **7** | &nbsp;&nbsp;&nbsp;&nbsp;SOLE DISPOSITIVE POWER<br>&nbsp;&nbsp;&nbsp;&nbsp;0 |
| &nbsp;&nbsp;&nbsp; NUMBER OF<br> SHARES<br> BENEFICIALLY <br> OWNED BY<br> EACH<br> REPORTING<br> PERSON<br> WITH: | **8** | &nbsp;&nbsp;&nbsp;&nbsp;SHARED DISPOSITIVE POWER<br>&nbsp;&nbsp;&nbsp;&nbsp;20,393,593 |

---

---

| | |
|:---|:---|
| &nbsp;&nbsp;&nbsp; **9** | &nbsp;&nbsp;&nbsp;&nbsp;AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON<br>&nbsp;&nbsp;&nbsp;&nbsp;20,393,593 |
| &nbsp;&nbsp;&nbsp;**10** | &nbsp;&nbsp;&nbsp;&nbsp;CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)<br>&nbsp;&nbsp;&nbsp;&nbsp;☐ |
| &nbsp;&nbsp;&nbsp;**11** | &nbsp;&nbsp;&nbsp;&nbsp;PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9<br>&nbsp;&nbsp;&nbsp;&nbsp;22.6% |
| &nbsp;&nbsp;&nbsp;**12** | &nbsp;&nbsp;&nbsp;&nbsp;TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)<br>&nbsp;&nbsp;&nbsp;&nbsp;PN |

---

------

---

| | |
|:---|:---|
| &nbsp;&nbsp;&nbsp; **1** | &nbsp;&nbsp;&nbsp;&nbsp;NAMES OF REPORTING PERSONS<br> &nbsp;&nbsp;&nbsp;&nbsp;I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)<br>&nbsp;&nbsp;&nbsp;&nbsp;Flagship Ventures Fund IV-Rx, L.P. |
| &nbsp;&nbsp;&nbsp; **2** | &nbsp;&nbsp;&nbsp;&nbsp;CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS)<br>&nbsp;&nbsp;&nbsp;&nbsp;(a) ☐ (b) ☒ |
| &nbsp;&nbsp;&nbsp; **3** | &nbsp;&nbsp;&nbsp;&nbsp;SEC USE ONLY |
| &nbsp;&nbsp;&nbsp; **4** | &nbsp;&nbsp;&nbsp;&nbsp;CITIZENSHIP OR PLACE OF ORGANIZATION<br>&nbsp;&nbsp;&nbsp;&nbsp;Delaware |

---

---

| | | |
|:---|:---|:---|
| &nbsp;&nbsp;&nbsp; NUMBER OF<br> SHARES<br> BENEFICIALLY <br> OWNED BY<br> EACH<br> REPORTING<br> PERSON<br> WITH: | **5** | &nbsp;&nbsp;&nbsp;&nbsp;SOLE VOTING POWER<br>&nbsp;&nbsp;&nbsp;&nbsp;0 |
| &nbsp;&nbsp;&nbsp; NUMBER OF<br> SHARES<br> BENEFICIALLY <br> OWNED BY<br> EACH<br> REPORTING<br> PERSON<br> WITH: | **6** | &nbsp;&nbsp;&nbsp;&nbsp;SHARED VOTING POWER<br>&nbsp;&nbsp;&nbsp;&nbsp;3,830,402 |
| &nbsp;&nbsp;&nbsp; NUMBER OF<br> SHARES<br> BENEFICIALLY <br> OWNED BY<br> EACH<br> REPORTING<br> PERSON<br> WITH: | **7** | &nbsp;&nbsp;&nbsp;&nbsp;SOLE DISPOSITIVE POWER<br>&nbsp;&nbsp;&nbsp;&nbsp;0 |
| &nbsp;&nbsp;&nbsp; NUMBER OF<br> SHARES<br> BENEFICIALLY <br> OWNED BY<br> EACH<br> REPORTING<br> PERSON<br> WITH: | **8** | &nbsp;&nbsp;&nbsp;&nbsp;SHARED DISPOSITIVE POWER<br>&nbsp;&nbsp;&nbsp;&nbsp;3,830,402 |

---

---

| | |
|:---|:---|
| &nbsp;&nbsp;&nbsp; **9** | &nbsp;&nbsp;&nbsp;&nbsp;AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON<br>&nbsp;&nbsp;&nbsp;&nbsp;3,830,402 |
| &nbsp;&nbsp;&nbsp;**10** | &nbsp;&nbsp;&nbsp;&nbsp;CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)<br>&nbsp;&nbsp;&nbsp;&nbsp;☐ |
| &nbsp;&nbsp;&nbsp;**11** | &nbsp;&nbsp;&nbsp;&nbsp;PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9<br>&nbsp;&nbsp;&nbsp;&nbsp;4.2% |
| &nbsp;&nbsp;&nbsp;**12** | &nbsp;&nbsp;&nbsp;&nbsp;TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)<br>&nbsp;&nbsp;&nbsp;&nbsp;PN |

---

------

---

| | |
|:---|:---|
| &nbsp;&nbsp;&nbsp; **1** | &nbsp;&nbsp;&nbsp;&nbsp;NAMES OF REPORTING PERSONS<br> &nbsp;&nbsp;&nbsp;&nbsp;I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)<br>&nbsp;&nbsp;&nbsp;&nbsp;Flagship Ventures Fund IV General Partner LLC |
| &nbsp;&nbsp;&nbsp; **2** | &nbsp;&nbsp;&nbsp;&nbsp;CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS)<br>&nbsp;&nbsp;&nbsp;&nbsp;(a) ☐ (b) ☒ |
| &nbsp;&nbsp;&nbsp; **3** | &nbsp;&nbsp;&nbsp;&nbsp;SEC USE ONLY |
| &nbsp;&nbsp;&nbsp; **4** | &nbsp;&nbsp;&nbsp;&nbsp;CITIZENSHIP OR PLACE OF ORGANIZATION<br>&nbsp;&nbsp;&nbsp;&nbsp;Delaware |

---

---

| | | |
|:---|:---|:---|
| &nbsp;&nbsp;&nbsp; NUMBER OF<br> SHARES<br> BENEFICIALLY <br> OWNED BY<br> EACH<br> REPORTING<br> PERSON<br> WITH: | **5** | &nbsp;&nbsp;&nbsp;&nbsp;SOLE VOTING POWER<br>&nbsp;&nbsp;&nbsp;&nbsp;0 |
| &nbsp;&nbsp;&nbsp; NUMBER OF<br> SHARES<br> BENEFICIALLY <br> OWNED BY<br> EACH<br> REPORTING<br> PERSON<br> WITH: | **6** | &nbsp;&nbsp;&nbsp;&nbsp;SHARED VOTING POWER<br>&nbsp;&nbsp;&nbsp;&nbsp;24,223,995 |
| &nbsp;&nbsp;&nbsp; NUMBER OF<br> SHARES<br> BENEFICIALLY <br> OWNED BY<br> EACH<br> REPORTING<br> PERSON<br> WITH: | **7** | &nbsp;&nbsp;&nbsp;&nbsp;SOLE DISPOSITIVE POWER<br>&nbsp;&nbsp;&nbsp;&nbsp;0 |
| &nbsp;&nbsp;&nbsp; NUMBER OF<br> SHARES<br> BENEFICIALLY <br> OWNED BY<br> EACH<br> REPORTING<br> PERSON<br> WITH: | **8** | &nbsp;&nbsp;&nbsp;&nbsp;SHARED DISPOSITIVE POWER<br>&nbsp;&nbsp;&nbsp;&nbsp;24,223,995 |

---

---

| | |
|:---|:---|
| &nbsp;&nbsp;&nbsp; **9** | &nbsp;&nbsp;&nbsp;&nbsp;AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON<br>&nbsp;&nbsp;&nbsp;&nbsp;24,223,995 |
| &nbsp;&nbsp;&nbsp;**10** | &nbsp;&nbsp;&nbsp;&nbsp;CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)<br>&nbsp;&nbsp;&nbsp;&nbsp;☐ |
| &nbsp;&nbsp;&nbsp;**11** | &nbsp;&nbsp;&nbsp;&nbsp;PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9<br>&nbsp;&nbsp;&nbsp;&nbsp;26.8% |
| &nbsp;&nbsp;&nbsp;**12** | &nbsp;&nbsp;&nbsp;&nbsp;TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)<br>&nbsp;&nbsp;&nbsp;&nbsp;OO |

---

------

---

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

---

---

| | | |
|:---|:---|:---|
| &nbsp;&nbsp;&nbsp; NUMBER OF<br> SHARES<br> BENEFICIALLY <br> OWNED BY<br> EACH<br> REPORTING<br> PERSON<br> WITH: | **5** | &nbsp;&nbsp;&nbsp;&nbsp;SOLE VOTING POWER<br>&nbsp;&nbsp;&nbsp;&nbsp;0 |
| &nbsp;&nbsp;&nbsp; NUMBER OF<br> SHARES<br> BENEFICIALLY <br> OWNED BY<br> EACH<br> REPORTING<br> PERSON<br> WITH: | **6** | &nbsp;&nbsp;&nbsp;&nbsp;SHARED VOTING POWER<br>&nbsp;&nbsp;&nbsp;&nbsp;5,789,414 |
| &nbsp;&nbsp;&nbsp; NUMBER OF<br> SHARES<br> BENEFICIALLY <br> OWNED BY<br> EACH<br> REPORTING<br> PERSON<br> WITH: | **7** | &nbsp;&nbsp;&nbsp;&nbsp;SOLE DISPOSITIVE POWER<br>&nbsp;&nbsp;&nbsp;&nbsp;0 |
| &nbsp;&nbsp;&nbsp; NUMBER OF<br> SHARES<br> BENEFICIALLY <br> OWNED BY<br> EACH<br> REPORTING<br> PERSON<br> WITH: | **8** | &nbsp;&nbsp;&nbsp;&nbsp;SHARED DISPOSITIVE POWER<br>&nbsp;&nbsp;&nbsp;&nbsp;5,789,414 |

---

---

| | |
|:---|:---|
| &nbsp;&nbsp;&nbsp; **9** | &nbsp;&nbsp;&nbsp;&nbsp;AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON<br>&nbsp;&nbsp;&nbsp;&nbsp;5,789,414 |
| &nbsp;&nbsp;&nbsp;**10** | &nbsp;&nbsp;&nbsp;&nbsp;CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)<br>&nbsp;&nbsp;&nbsp;&nbsp;☐ |
| &nbsp;&nbsp;&nbsp;**11** | &nbsp;&nbsp;&nbsp;&nbsp;PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9<br>&nbsp;&nbsp;&nbsp;&nbsp;6.4% |
| &nbsp;&nbsp;&nbsp;**12** | &nbsp;&nbsp;&nbsp;&nbsp;TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)<br>&nbsp;&nbsp;&nbsp;&nbsp;PN |

---

------

---

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

---

---

| | | |
|:---|:---|:---|
| &nbsp;&nbsp;&nbsp; NUMBER OF<br> SHARES<br> BENEFICIALLY <br> OWNED BY<br> EACH<br> REPORTING<br> PERSON<br> WITH: | **5** | &nbsp;&nbsp;&nbsp;&nbsp;SOLE VOTING POWER<br>&nbsp;&nbsp;&nbsp;&nbsp;0 |
| &nbsp;&nbsp;&nbsp; NUMBER OF<br> SHARES<br> BENEFICIALLY <br> OWNED BY<br> EACH<br> REPORTING<br> PERSON<br> WITH: | **6** | &nbsp;&nbsp;&nbsp;&nbsp;SHARED VOTING POWER<br>&nbsp;&nbsp;&nbsp;&nbsp;5,859,414 |
| &nbsp;&nbsp;&nbsp; NUMBER OF<br> SHARES<br> BENEFICIALLY <br> OWNED BY<br> EACH<br> REPORTING<br> PERSON<br> WITH: | **7** | &nbsp;&nbsp;&nbsp;&nbsp;SOLE DISPOSITIVE POWER<br>&nbsp;&nbsp;&nbsp;&nbsp;0 |
| &nbsp;&nbsp;&nbsp; NUMBER OF<br> SHARES<br> BENEFICIALLY <br> OWNED BY<br> EACH<br> REPORTING<br> PERSON<br> WITH: | **8** | &nbsp;&nbsp;&nbsp;&nbsp;SHARED DISPOSITIVE POWER<br>&nbsp;&nbsp;&nbsp;&nbsp;5,859,414 |

---

---

| | |
|:---|:---|
| &nbsp;&nbsp;&nbsp; **9** | &nbsp;&nbsp;&nbsp;&nbsp;AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON<br>&nbsp;&nbsp;&nbsp;&nbsp;5,859,414 |
| &nbsp;&nbsp;&nbsp;**10** | &nbsp;&nbsp;&nbsp;&nbsp;CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)<br>&nbsp;&nbsp;&nbsp;&nbsp;☐ |
| &nbsp;&nbsp;&nbsp;**11** | &nbsp;&nbsp;&nbsp;&nbsp;PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9<br>&nbsp;&nbsp;&nbsp;&nbsp;6.5% |
| &nbsp;&nbsp;&nbsp;**12** | &nbsp;&nbsp;&nbsp;&nbsp;TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)<br>&nbsp;&nbsp;&nbsp;&nbsp;PN |

---

------

---

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

---

---

| | | |
|:---|:---|:---|
| &nbsp;&nbsp;&nbsp; NUMBER OF<br> SHARES<br> BENEFICIALLY <br> OWNED BY<br> EACH<br> REPORTING<br> PERSON<br> WITH: | **5** | &nbsp;&nbsp;&nbsp;&nbsp;SOLE VOTING POWER<br>&nbsp;&nbsp;&nbsp;&nbsp;0 |
| &nbsp;&nbsp;&nbsp; NUMBER OF<br> SHARES<br> BENEFICIALLY <br> OWNED BY<br> EACH<br> REPORTING<br> PERSON<br> WITH: | **6** | &nbsp;&nbsp;&nbsp;&nbsp;SHARED VOTING POWER<br>&nbsp;&nbsp;&nbsp;&nbsp;11,648,828 |
| &nbsp;&nbsp;&nbsp; NUMBER OF<br> SHARES<br> BENEFICIALLY <br> OWNED BY<br> EACH<br> REPORTING<br> PERSON<br> WITH: | **7** | &nbsp;&nbsp;&nbsp;&nbsp;SOLE DISPOSITIVE POWER<br>&nbsp;&nbsp;&nbsp;&nbsp;0 |
| &nbsp;&nbsp;&nbsp; NUMBER OF<br> SHARES<br> BENEFICIALLY <br> OWNED BY<br> EACH<br> REPORTING<br> PERSON<br> WITH: | **8** | &nbsp;&nbsp;&nbsp;&nbsp;SHARED DISPOSITIVE POWER<br>&nbsp;&nbsp;&nbsp;&nbsp;11,648,828 |

---

---

| | |
|:---|:---|
| &nbsp;&nbsp;&nbsp; **9** | &nbsp;&nbsp;&nbsp;&nbsp;AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON<br>&nbsp;&nbsp;&nbsp;&nbsp;11,648,828 |
| &nbsp;&nbsp;&nbsp;**10** | &nbsp;&nbsp;&nbsp;&nbsp;CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)<br>&nbsp;&nbsp;&nbsp;&nbsp;☐ |
| &nbsp;&nbsp;&nbsp;**11** | &nbsp;&nbsp;&nbsp;&nbsp;PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9<br>&nbsp;&nbsp;&nbsp;&nbsp;12.9% |
| &nbsp;&nbsp;&nbsp;**12** | &nbsp;&nbsp;&nbsp;&nbsp;TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)<br>&nbsp;&nbsp;&nbsp;&nbsp;OO |

---

------

---

| | |
|:---|:---|
| &nbsp;&nbsp;&nbsp; **1** | &nbsp;&nbsp;&nbsp;&nbsp;NAMES OF REPORTING PERSONS<br> &nbsp;&nbsp;&nbsp;&nbsp;I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)<br>&nbsp;&nbsp;&nbsp;&nbsp;Flagship Ventures Opportunities Fund I, L.P. |
| &nbsp;&nbsp;&nbsp; **2** | &nbsp;&nbsp;&nbsp;&nbsp;CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS)<br>&nbsp;&nbsp;&nbsp;&nbsp;(a) ☐ (b) ☒ |
| &nbsp;&nbsp;&nbsp; **3** | &nbsp;&nbsp;&nbsp;&nbsp;SEC USE ONLY |
| &nbsp;&nbsp;&nbsp; **4** | &nbsp;&nbsp;&nbsp;&nbsp;CITIZENSHIP OR PLACE OF ORGANIZATION<br>&nbsp;&nbsp;&nbsp;&nbsp;Delaware |

---

---

| | | |
|:---|:---|:---|
| &nbsp;&nbsp;&nbsp; NUMBER OF<br> SHARES<br> BENEFICIALLY <br> OWNED BY<br> EACH<br> REPORTING<br> PERSON<br> WITH: | **5** | &nbsp;&nbsp;&nbsp;&nbsp;SOLE VOTING POWER<br>&nbsp;&nbsp;&nbsp;&nbsp;0 |
| &nbsp;&nbsp;&nbsp; NUMBER OF<br> SHARES<br> BENEFICIALLY <br> OWNED BY<br> EACH<br> REPORTING<br> PERSON<br> WITH: | **6** | &nbsp;&nbsp;&nbsp;&nbsp;SHARED VOTING POWER<br>&nbsp;&nbsp;&nbsp;&nbsp;2,633,703 |
| &nbsp;&nbsp;&nbsp; NUMBER OF<br> SHARES<br> BENEFICIALLY <br> OWNED BY<br> EACH<br> REPORTING<br> PERSON<br> WITH: | **7** | &nbsp;&nbsp;&nbsp;&nbsp;SOLE DISPOSITIVE POWER<br>&nbsp;&nbsp;&nbsp;&nbsp;0 |
| &nbsp;&nbsp;&nbsp; NUMBER OF<br> SHARES<br> BENEFICIALLY <br> OWNED BY<br> EACH<br> REPORTING<br> PERSON<br> WITH: | **8** | &nbsp;&nbsp;&nbsp;&nbsp;SHARED DISPOSITIVE POWER<br>&nbsp;&nbsp;&nbsp;&nbsp;2,633,703 |

---

---

| | |
|:---|:---|
| &nbsp;&nbsp;&nbsp; **9** | &nbsp;&nbsp;&nbsp;&nbsp;AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON<br>&nbsp;&nbsp;&nbsp;&nbsp;2,633,703 |
| &nbsp;&nbsp;&nbsp;**10** | &nbsp;&nbsp;&nbsp;&nbsp;CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)<br>&nbsp;&nbsp;&nbsp;&nbsp;☐ |
| &nbsp;&nbsp;&nbsp;**11** | &nbsp;&nbsp;&nbsp;&nbsp;PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9<br>&nbsp;&nbsp;&nbsp;&nbsp;2.9% |
| &nbsp;&nbsp;&nbsp;**12** | &nbsp;&nbsp;&nbsp;&nbsp;TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)<br>&nbsp;&nbsp;&nbsp;&nbsp;PN |

---

------

---

| | |
|:---|:---|
| &nbsp;&nbsp;&nbsp; **1** | &nbsp;&nbsp;&nbsp;&nbsp;NAMES OF REPORTING PERSONS<br> &nbsp;&nbsp;&nbsp;&nbsp;I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)<br>&nbsp;&nbsp;&nbsp;&nbsp;Flagship Ventures Opportunities Fund I General Partner LLC |
| &nbsp;&nbsp;&nbsp; **2** | &nbsp;&nbsp;&nbsp;&nbsp;CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS)<br>&nbsp;&nbsp;&nbsp;&nbsp;(a) ☐ (b) ☒ |
| &nbsp;&nbsp;&nbsp; **3** | &nbsp;&nbsp;&nbsp;&nbsp;SEC USE ONLY |
| &nbsp;&nbsp;&nbsp; **4** | &nbsp;&nbsp;&nbsp;&nbsp;CITIZENSHIP OR PLACE OF ORGANIZATION<br>&nbsp;&nbsp;&nbsp;&nbsp;Delaware |

---

---

| | | |
|:---|:---|:---|
| &nbsp;&nbsp;&nbsp; NUMBER OF<br> SHARES<br> BENEFICIALLY <br> OWNED BY<br> EACH<br> REPORTING<br> PERSON<br> WITH: | **5** | &nbsp;&nbsp;&nbsp;&nbsp;SOLE VOTING POWER<br>&nbsp;&nbsp;&nbsp;&nbsp;0 |
| &nbsp;&nbsp;&nbsp; NUMBER OF<br> SHARES<br> BENEFICIALLY <br> OWNED BY<br> EACH<br> REPORTING<br> PERSON<br> WITH: | **6** | &nbsp;&nbsp;&nbsp;&nbsp;SHARED VOTING POWER<br>&nbsp;&nbsp;&nbsp;&nbsp;2,633,703 |
| &nbsp;&nbsp;&nbsp; NUMBER OF<br> SHARES<br> BENEFICIALLY <br> OWNED BY<br> EACH<br> REPORTING<br> PERSON<br> WITH: | **7** | &nbsp;&nbsp;&nbsp;&nbsp;SOLE DISPOSITIVE POWER<br>&nbsp;&nbsp;&nbsp;&nbsp;0 |
| &nbsp;&nbsp;&nbsp; NUMBER OF<br> SHARES<br> BENEFICIALLY <br> OWNED BY<br> EACH<br> REPORTING<br> PERSON<br> WITH: | **8** | &nbsp;&nbsp;&nbsp;&nbsp;SHARED DISPOSITIVE POWER<br>&nbsp;&nbsp;&nbsp;&nbsp;2,633,703 |

---

---

| | |
|:---|:---|
| &nbsp;&nbsp;&nbsp; **9** | &nbsp;&nbsp;&nbsp;&nbsp;AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON<br>&nbsp;&nbsp;&nbsp;&nbsp;2,633,703 |
| &nbsp;&nbsp;&nbsp;**10** | &nbsp;&nbsp;&nbsp;&nbsp;CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)<br>&nbsp;&nbsp;&nbsp;&nbsp;☐ |
| &nbsp;&nbsp;&nbsp;**11** | &nbsp;&nbsp;&nbsp;&nbsp;PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9<br>&nbsp;&nbsp;&nbsp;&nbsp;2.9% |
| &nbsp;&nbsp;&nbsp;**12** | &nbsp;&nbsp;&nbsp;&nbsp;TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)<br>&nbsp;&nbsp;&nbsp;&nbsp;OO |

---

------

---

| | |
|:---|:---|
| &nbsp;&nbsp;&nbsp; **1** | &nbsp;&nbsp;&nbsp;&nbsp;NAMES OF REPORTING PERSONS<br> &nbsp;&nbsp;&nbsp;&nbsp;I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)<br>&nbsp;&nbsp;&nbsp;&nbsp;Noubar B. Afeyan, Ph.D. |
| &nbsp;&nbsp;&nbsp; **2** | &nbsp;&nbsp;&nbsp;&nbsp;CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS)<br>&nbsp;&nbsp;&nbsp;&nbsp;(a) ☐ (b) ☒ |
| &nbsp;&nbsp;&nbsp; **3** | &nbsp;&nbsp;&nbsp;&nbsp;SEC USE ONLY |
| &nbsp;&nbsp;&nbsp; **4** | &nbsp;&nbsp;&nbsp;&nbsp;CITIZENSHIP OR PLACE OF ORGANIZATION<br>&nbsp;&nbsp;&nbsp;&nbsp;United States of America |

---

---

| | | |
|:---|:---|:---|
| &nbsp;&nbsp;&nbsp; NUMBER OF<br> SHARES<br> BENEFICIALLY <br> OWNED BY<br> EACH<br> REPORTING<br> PERSON<br> WITH: | **5** | &nbsp;&nbsp;&nbsp;&nbsp;SOLE VOTING POWER<br>&nbsp;&nbsp;&nbsp;&nbsp;100,000 (1) |
| &nbsp;&nbsp;&nbsp; NUMBER OF<br> SHARES<br> BENEFICIALLY <br> OWNED BY<br> EACH<br> REPORTING<br> PERSON<br> WITH: | **6** | &nbsp;&nbsp;&nbsp;&nbsp;SHARED VOTING POWER<br>&nbsp;&nbsp;&nbsp;&nbsp;38,506,526 |
| &nbsp;&nbsp;&nbsp; NUMBER OF<br> SHARES<br> BENEFICIALLY <br> OWNED BY<br> EACH<br> REPORTING<br> PERSON<br> WITH: | **7** | &nbsp;&nbsp;&nbsp;&nbsp;SOLE DISPOSITIVE POWER<br>&nbsp;&nbsp;&nbsp;&nbsp;100,000 (1) |
| &nbsp;&nbsp;&nbsp; NUMBER OF<br> SHARES<br> BENEFICIALLY <br> OWNED BY<br> EACH<br> REPORTING<br> PERSON<br> WITH: | **8** | &nbsp;&nbsp;&nbsp;&nbsp;SHARED DISPOSITIVE POWER<br>&nbsp;&nbsp;&nbsp;&nbsp;38,506,526 |

---

---

| | |
|:---|:---|
| &nbsp;&nbsp;&nbsp; **9** | &nbsp;&nbsp;&nbsp;&nbsp;AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON<br>&nbsp;&nbsp;&nbsp;&nbsp;38,606,526 (1) |
| &nbsp;&nbsp;&nbsp;**10** | &nbsp;&nbsp;&nbsp;&nbsp;CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)<br>&nbsp;&nbsp;&nbsp;&nbsp;☐ |
| &nbsp;&nbsp;&nbsp;**11** | &nbsp;&nbsp;&nbsp;&nbsp;PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9<br>&nbsp;&nbsp;&nbsp;&nbsp;42.7% |
| &nbsp;&nbsp;&nbsp;**12** | &nbsp;&nbsp;&nbsp;&nbsp;TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)<br>&nbsp;&nbsp;&nbsp;&nbsp;IN |

---

(1) Includes options to purchase 100,000 shares of Common Stock that are exercisable within 60 days of
December 31, 2022.

------

---

| | |
|:---|:---|
| **Item 1(a).** | **<u>Name of Issuer</u>:**  |

---

Rubius Therapeutics, Inc. (the "Issuer")

---

| | |
|:---|:---|
| **Item 1(b).** | **<u>Address of Issuer's Principal Executive Offices</u>:**  |

---

399 Binney Street, Suite 300, Cambridge, MA 02139

---

| | |
|:---|:---|
| **Item 2(a).** | **<u>Names of Persons Filing</u>:**  |

---

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

Flagship VentureLabs IV LLC ("VentureLabs IV")

Flagship Ventures Fund IV, L.P. ("Flagship IV Fund")

Flagship Ventures Fund IV-Rx, LP ("Flagship IV-Rx Fund")

Flagship Ventures Fund IV General Partner LLC ("Flagship IV GP")

Flagship V VentureLabs Rx Fund, L.P. ("VentureLabs Rx V")

Flagship Ventures Fund V, L.P. ("Flagship V Fund")

Flagship Ventures Fund V General Partner LLC ("Flagship V GP")

Flagship Ventures Opportunities Fund I, L.P. ("Flagship Opportunities I")

Flagship Ventures Opportunities Fund I General Partner LLC ("Flagship Opportunities GP")

Noubar B. Afeyan, Ph.D. ("Dr. Afeyan")

---

| | |
|:---|:---|
| **Item 2(b).** | **<u>Address of Principal Business Office or, if None, Residence</u>:**  |

---

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).** | **<u>Citizenship</u>:**  |

---

---

| | |
|:---|:---|
| VentureLabs IV | Delaware |
| Flagship IV Fund | Delaware |
| Flagship IV-Rx Fund | Delaware |
| Flagship IV GP | Delaware |
| VentureLabs Rx V | Delaware |
| Flagship V Fund | Delaware |
| Flagship V GP | Delaware |
| Flagship Opportunities I | Delaware |
| Flagship Opportunities GP | Delaware |
| Dr. Afeyan | United States of America |

---

---

| | |
|:---|:---|
| **Item 2(d).** | **<u>Title of Class</u> <u>of Securities</u>:**  |

---

Common Stock, $0.001 par value per share ("Common Stock").

---

| | |
|:---|:---|
| **Item 2(e).** | **<u>CUSIP Number</u>:**  |

---

78116T 10 3

------

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

Not applicable.

**Item 4.** **<u>Ownership</u>.** <br>

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 90,371,532 shares of outstanding Common Stock as of October 31, 2022, as reported in the Issuer's 10-Q filed on November 9, 2022.

Flagship IV Fund is the manager of VentureLabs IV and, as such, may be deemed to beneficially own the shares held by VentureLabs IV.

Flagship IV GP is the general partner of each of Flagship IV Fund and Flagship IV-Rx Fund, and, as such, may be deemed to beneficially own the shares beneficially owned by Flagship IV Fund and Flagship IV-Rx Fund.

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

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

Dr. Afeyan is the sole manager of Flagship Fund IV GP, Flagship Fund V GP and Flagship Opportunities GP, and as such, may be deemed to beneficially own the shares beneficially owned by VentureLabs IV, Flagship IV Fund, Flagship IV-Rx Fund, Flagship V Fund, VentureLabs Rx V Fund and Flagship Opportunities I.

Each of the Reporting Persons expressly disclaims beneficial ownership of the shares reported in this Schedule 13G except to the extent of its or his pecuniary interest in such shares.

**Item 5.** **<u>Ownership of Five Percent or Less of a Class</u>.** <br>

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.** **<u>Ownership of More than Five Percent on Behalf of Another Person</u>.** <br>

Not applicable.

**Item 7.** **<u>Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person</u>.** <br>

Not applicable.

**Item 8.** **<u>Identification and Classification of Members of the Group</u>.** <br>

Not applicable.

**Item 9.** **<u>Notice of Dissolution of Group</u>.** <br>

Not applicable.

**Item 10.** **<u>Certification</u>.** <br>

Not applicable.

------

<u>SIGNATURE</u> 

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, 2023 | Date: February 14, 2023 |
| FLAGSHIP VENTURELABS IV LLC | FLAGSHIP VENTURELABS IV LLC |
| By: | Flagship Ventures Fund IV, L.P.<br> Manager |
| By: | Flagship Ventures Fund IV General Partner LLC<br> General Partner |
| By: | /s/ Noubar B. Afeyan, Ph.D. |
|  | Noubar B. Afeyan, Ph.D. |
|  | Manager |
| FLAGSHIP VENTURES FUND IV, L.P. | FLAGSHIP VENTURES FUND IV, L.P. |
| By: | Flagship Ventures Fund IV General Partner LLC |
|  | General Partner |
| By: | /s/ Noubar B. Afeyan, Ph.D. |
|  | Noubar B. Afeyan, Ph.D. |
|  | Manager |
| FLAGSHIP VENTURES FUND IV-RX, L.P. | FLAGSHIP VENTURES FUND IV-RX, L.P. |
| By: | Flagship Ventures Fund IV General Partner LLC |
|  | General Partner |
| By: | /s/ Noubar B. Afeyan, Ph.D. |
|  | Noubar B. Afeyan, Ph.D. |
|  | Manager |
| FLAGSHIP VENTURES FUND IV GENERAL PARTNER LLC | FLAGSHIP VENTURES FUND IV GENERAL PARTNER LLC |
| By: | /s/ Noubar B. Afeyan, Ph.D. |
|  | Noubar B. Afeyan, Ph.D. |
|  | Manager |

---

------

---

| | |
|:---|:---|
| FLAGSHIP V VENTURLABS RX FUND, L.P. | FLAGSHIP V VENTURLABS 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. | 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 | FLAGSHIP VENTURES FUND V GENERAL PARTNER LLC |
| By: | /s/ Noubar B. Afeyan, Ph.D. |
|  | Noubar B. Afeyan, Ph.D. |
|  | Manager |
| FLAGSHIP VENTURES OPPORTUNITIES FUND I, L.P. | FLAGSHIP VENTURES OPPORTUNITIES FUND I, L.P. |
| By: | Flagship Ventures Opportunities Fund I General Partner LLC |
|  | General Partner |
| By: | /s/ Noubar B. Afeyan, Ph.D. |
|  | Noubar B. Afeyan, Ph.D. |
|  | Manager |
| FLAGSHIP VENTURES OPPORTUNITIES FUND I GENERAL PARTNER LLC | FLAGSHIP VENTURES OPPORTUNITIES FUND I GENERAL PARTNER LLC |
| By: | /s/ Noubar B. Afeyan, Ph.D. |
|  | Noubar B. Afeyan, Ph.D. |
|  | Manager |
| /s/ Noubar B. Afeyan, Ph.D. | /s/ Noubar B. Afeyan, Ph.D. |
| NOUBAR B. AFEYAN, PH,D. | NOUBAR B. AFEYAN, PH,D. |

---