# EDGAR Filing Document

**Accession Number:** 0001493463
**File Stem:** 0001193125-23-027069
**Filing Date:** 2023-2
**Character Count:** 37185
**Document Hash:** 30f49b75a39783aa081578ea7f511590
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001193125-23-027069.hdr.sgml**: 20230207

**ACCESSION NUMBER**: 0001193125-23-027069

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

**PUBLIC DOCUMENT COUNT**: 1

**FILED AS OF DATE**: 20230207

**DATE AS OF CHANGE**: 20230207

**GROUP MEMBERS**: AMIR NASHAT

**GROUP MEMBERS**: BRIAN CHEE

**GROUP MEMBERS**: BRYCE YOUNGREN

**GROUP MEMBERS**: DAVID BARRETT

**GROUP MEMBERS**: JONATHAN A. FLINT

**GROUP MEMBERS**: POLARIS VENTURE MANAGEMENT CO VI, L.L.C.

**GROUP MEMBERS**: POLARIS VENTURE PARTNERS FOUNDERS' FUND VI, L.P.

**GROUP MEMBERS**: TERRANCE G. MCGUIRE

**SUBJECT COMPANY**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** Scholar Rock Holding Corp
- **CENTRAL INDEX KEY:** 0001727196
- **STANDARD INDUSTRIAL CLASSIFICATION:** BIOLOGICAL PRODUCTS (NO DIAGNOSTIC SUBSTANCES) [2836]
- **IRS NUMBER:** 823750435
- **STATE OF INCORPORATION:** DE
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** SC 13G/A
- **SEC ACT:** 1934 Act
- **SEC FILE NUMBER:** 005-90496
- **FILM NUMBER:** 23596032

**BUSINESS ADDRESS:**
- **STREET 1:** 301 BINNEY STREET
- **STREET 2:** 3RD FLOOR
- **CITY:** CAMBRIDGE
- **STATE:** MA
- **ZIP:** 02142
- **BUSINESS PHONE:** 857-259-3860

**MAIL ADDRESS:**
- **STREET 1:** 301 BINNEY STREET
- **STREET 2:** 3RD FLOOR
- **CITY:** CAMBRIDGE
- **STATE:** MA
- **ZIP:** 02142
**FILED BY**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** Polaris Venture Partners VI, L.P.
- **CENTRAL INDEX KEY:** 0001493463
- **IRS NUMBER:** 000000000
- **STATE OF INCORPORATION:** DE
- **FISCAL YEAR END:** 1231

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

**BUSINESS ADDRESS:**
- **STREET 1:** ONE MARINA PARK DRIVE, 10TH FLOOR
- **CITY:** BOSTON
- **STATE:** MA
- **ZIP:** 02210
- **BUSINESS PHONE:** 781-290-0770

**MAIL ADDRESS:**
- **STREET 1:** ONE MARINA PARK DRIVE, 10TH FLOOR
- **CITY:** BOSTON
- **STATE:** MA
- **ZIP:** 02210

------

------

**SECURITIES AND EXCHANGE COMMISSION** 

**Washington, D.C. 20549** 

------

**Schedule 13G** 

**(Rule 13d-102)**

**INFORMATION TO BE INCLUDED IN STATEMENTS FILED** 

**PURSUANT TO RULES 13d-1 (b), (c) AND (d) AND AMENDMENTS THERETO FILED** 

**PURSUANT TO 13d-2 (b)** 

**(Amendment No. 2)** 

------

## Scholar Rock Holding Corporation
**(Name of Issuer)** 

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

**(Title of Class of Securities)** 

**80706P103** 

**(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 disclosures provided in a prior cover page.

The information required on 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).

------

(Continued on following pages)

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CUSIP #80706P103 Page 2 of 13

---

| | |
|:---|:---|
| &nbsp;&nbsp;&nbsp; 1 | &nbsp;&nbsp;&nbsp;&nbsp;NAME OF REPORTING PERSONS<br>&nbsp;&nbsp;&nbsp;&nbsp;Polaris Venture Partners VI, L.P. |
| &nbsp;&nbsp;&nbsp; 2 | &nbsp;&nbsp;&nbsp;&nbsp;CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP<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;3,823,492 (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;0 |
| &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;3,823,492 (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;0 |

---

---

| | |
|:---|:---|
| &nbsp;&nbsp;&nbsp; 9 | &nbsp;&nbsp;&nbsp;&nbsp;AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON<br>&nbsp;&nbsp;&nbsp;&nbsp;3,823,492 (1) |
| &nbsp;&nbsp;&nbsp;10 | &nbsp;&nbsp;&nbsp;&nbsp;CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES<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;7.4% (2) |
| &nbsp;&nbsp;&nbsp;12 | &nbsp;&nbsp;&nbsp;&nbsp;TYPE OF REPORTING PERSON<br>&nbsp;&nbsp;&nbsp;&nbsp;PN |

---

(1) 3,540,530 of such shares are held of record by PVP VI (as defined in Item 2(a) of the Original Schedule 13G)
and 282,962 of such shares are shares underlying a warrant issued to PVP VI and which is exercisable within 60 days of the filing of this Amendment (as defined below). PVM VI (as defined in Item 2(a) of the Original Schedule 13G), the general
partner of PVP VI, may be deemed to have voting, investment and dispositive power with respect to these securities. David Barrett, Brian Chee, Jonathan A. Flint, Terrance G. McGuire, Amir Nashat, a member of the Issuer's board of directors, and
Bryce Youngren are the managing members of PVM VI and may each be deemed to share voting, investment and dispositive power with respect to these securities.

(2) Based on 51,946,353 shares of the Issuer's Common Stock, calculated as follows (i) 51,663,391 shares of
the Issuer's Common Stock outstanding as of November 8, 2022, as reported by the Issuer in its Form 10-Q for the quarter ended September 30, 2022, filed with the US Securities and Exchange
Commission (the "Commission") on November 14, 2022 (the "Form 10-Q") plus (ii) 282,962 shares of the Issuer's Common Stock are shares underlying a warrant issued to PVP VI and
which is exercisable within 60 days of the filing of this Amendment.

------

CUSIP #80706P103 Page 3 of 13

---

| | |
|:---|:---|
| &nbsp;&nbsp;&nbsp; 1 | &nbsp;&nbsp;&nbsp;&nbsp;NAME OF REPORTING PERSONS<br>&nbsp;&nbsp;&nbsp;&nbsp;Polaris Venture Partners Founders' Fund VI, L.P. |
| &nbsp;&nbsp;&nbsp; 2 | &nbsp;&nbsp;&nbsp;&nbsp;CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP<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;223,433 (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;0 |
| &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;223,433 (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;0 |

---

---

| | |
|:---|:---|
| &nbsp;&nbsp;&nbsp; 9 | &nbsp;&nbsp;&nbsp;&nbsp;AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON<br>&nbsp;&nbsp;&nbsp;&nbsp;223,433 (1) |
| &nbsp;&nbsp;&nbsp;10 | &nbsp;&nbsp;&nbsp;&nbsp;CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES<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;0.4% (2) |
| &nbsp;&nbsp;&nbsp;12 | &nbsp;&nbsp;&nbsp;&nbsp;TYPE OF REPORTING PERSON<br>&nbsp;&nbsp;&nbsp;&nbsp;PN |

---

(1) 206,897 of such shares are held of record by PVPFF VI (as defined in Item 2(a) of the Original Schedule 13G)
and 16,536 of such shares are shares underlying a warrant issued to PVPFF VI and which is exercisable within 60 days of the filing of this Amendment. PVM VI, the general partner of PVPFF VI, may be deemed to have voting, investment and dispositive
power with respect to these securities. David Barrett, Brian Chee, Jonathan A. Flint, Terrance G. McGuire, Amir Nashat, a member of the Issuer's board of directors, and Bryce Youngren are the managing members of PVM VI and may each be deemed to
share voting, investment and dispositive power with respect to these securities.

(2) Based on 51,679,927 shares of the Issuer's Common Stock, calculated as follows (i) 51,663,391 shares of
the Issuer's Common Stock outstanding as of November 8, 2022, as reported by the Issuer in the Form 10-Q plus 16,536 shares of the Issuer's Common Stock are shares underlying a warrant issued to
PVPFF VI and which is exercisable within 60 days of the filing of this Amendment.

------

CUSIP #80706P103 Page 4 of 13

---

| | |
|:---|:---|
| &nbsp;&nbsp;&nbsp; 1 | &nbsp;&nbsp;&nbsp;&nbsp;NAME OF REPORTING PERSONS<br>&nbsp;&nbsp;&nbsp;&nbsp;Polaris Venture Management Co VI, L.L.C. |
| &nbsp;&nbsp;&nbsp; 2 | &nbsp;&nbsp;&nbsp;&nbsp;CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP<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;4,046,925 (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;0 |
| &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;4,046,925 (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;0 |

---

---

| | |
|:---|:---|
| &nbsp;&nbsp;&nbsp; 9 | &nbsp;&nbsp;&nbsp;&nbsp;AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON<br>&nbsp;&nbsp;&nbsp;&nbsp;4,046,925 (1) |
| &nbsp;&nbsp;&nbsp;10 | &nbsp;&nbsp;&nbsp;&nbsp;CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES<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;7.8% (2) |
| &nbsp;&nbsp;&nbsp;12 | &nbsp;&nbsp;&nbsp;&nbsp;TYPE OF REPORTING PERSON<br>&nbsp;&nbsp;&nbsp;&nbsp;OO |

---

(1) 3,540,530 of such shares are held of record by PVP VI, 282,962 of such shares are shares underlying a warrant
issued to PVP VI and which is exercisable within 60 days of the filing of this Amendment, 206,897 of such shares are held of record by PVPFF VI and 16,536 of such shares are shares underlying a warrant issued to PVPFF VI and which is exercisable
within 60 days of the filing of this Amendment. PVM VI, the general partner of each of PVP VI and PVPFF VI, may be deemed to have voting, investment and dispositive power with respect to these securities. David Barrett, Brian Chee, Jonathan A.
Flint, Terrance G. McGuire, Amir Nashat, a member of the Issuer's board of directors, and Bryce Youngren are the managing members of PVM VI and may each be deemed to share voting, investment and dispositive power with respect to these
securities.

(2) Based on 51,962,889 shares of the Issuer's Common Stock, calculated as follows (i) 51,663,391 shares of
the Issuer's Common Stock outstanding as of November 8, 2022, as reported by the Issuer in the Form 10-Q plus (ii) 282,962 shares of the Issuer's Common Stock are shares underlying a warrant
issued to PVP VI and which is exercisable within 60 days of the filing of this Amendment plus (iii) 16,536 shares of the Issuer's Common Stock are shares underlying a warrant issued to PVPFF VI and which is exercisable within 60 days of the
filing of this Amendment.

------

CUSIP #80706P103 Page 5 of 13

---

| | |
|:---|:---|
| &nbsp;&nbsp;&nbsp; 1 | &nbsp;&nbsp;&nbsp;&nbsp;NAME OF REPORTING PERSONS<br>&nbsp;&nbsp;&nbsp;&nbsp;David Barrett |
| &nbsp;&nbsp;&nbsp; 2 | &nbsp;&nbsp;&nbsp;&nbsp;CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP<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 |

---

---

| | | |
|:---|:---|:---|
| &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;4,046,925 (1) |
| &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;4,046,925 (1) |

---

---

| | |
|:---|:---|
| &nbsp;&nbsp;&nbsp; 9 | &nbsp;&nbsp;&nbsp;&nbsp;AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON<br>&nbsp;&nbsp;&nbsp;&nbsp;4,046,925 (1) |
| &nbsp;&nbsp;&nbsp;10 | &nbsp;&nbsp;&nbsp;&nbsp;CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES<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;7.8% (2) |
| &nbsp;&nbsp;&nbsp;12 | &nbsp;&nbsp;&nbsp;&nbsp;TYPE OF REPORTING PERSON<br>&nbsp;&nbsp;&nbsp;&nbsp;IN |

---

(1) 3,540,530 of such shares are held of record by PVP VI, 282,962 of such shares are shares underlying a warrant
issued to PVP VI and which is exercisable within 60 days of the filing of this Amendment, 206,897 of such shares are held of record by PVPFF VI and 16,536 of such shares are shares underlying a warrant issued to PVPFF VI and which is exercisable
within 60 days of the filing of this Amendment. PVM VI, the general partner of each of PVP VI and PVPFF VI, may be deemed to have voting, investment and dispositive power with respect to these securities. David Barrett, Brian Chee, Jonathan A.
Flint, Terrance G. McGuire, Amir Nashat, a member of the Issuer's board of directors, and Bryce Youngren are the managing members of PVM VI and may each be deemed to share voting, investment and dispositive power with respect to these
securities.

(2) Based on 51,962,889 shares of the Issuer's Common Stock, calculated as follows (i) 51,663,391 shares of
the Issuer's Common Stock outstanding as of November 8, 2022, as reported by the Issuer in the Form 10-Q plus (ii) 282,962 shares of the Issuer's Common Stock are shares underlying a warrant
issued to PVP VI and which is exercisable within 60 days of the filing of this Amendment plus (iii) 16,536 shares of the Issuer's Common Stock are shares underlying a warrant issued to PVPFF VI and which is exercisable within 60 days of the
filing of this Amendment.

------

CUSIP #80706P103 Page 6 of 13

---

| | |
|:---|:---|
| &nbsp;&nbsp;&nbsp; 1 | &nbsp;&nbsp;&nbsp;&nbsp;NAME OF REPORTING PERSONS<br>&nbsp;&nbsp;&nbsp;&nbsp;Brian Chee |
| &nbsp;&nbsp;&nbsp; 2 | &nbsp;&nbsp;&nbsp;&nbsp;CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP<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 |

---

---

| | | |
|:---|:---|:---|
| &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;4,046,925 (1) |
| &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;4,046,925 (1) |

---

---

| | |
|:---|:---|
| &nbsp;&nbsp;&nbsp; 9 | &nbsp;&nbsp;&nbsp;&nbsp;AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON<br>&nbsp;&nbsp;&nbsp;&nbsp;4,046,925 (1) |
| &nbsp;&nbsp;&nbsp;10 | &nbsp;&nbsp;&nbsp;&nbsp;CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES<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;7.8% (2) |
| &nbsp;&nbsp;&nbsp;12 | &nbsp;&nbsp;&nbsp;&nbsp;TYPE OF REPORTING PERSON<br>&nbsp;&nbsp;&nbsp;&nbsp;IN |

---

(1) 3,540,530 of such shares are held of record by PVP VI, 282,962 of such shares are shares underlying a warrant
issued to PVP VI and which is exercisable within 60 days of the filing of this Amendment, 206,897 of such shares are held of record by PVPFF VI and 16,536 of such shares are shares underlying a warrant issued to PVPFF VI and which is exercisable
within 60 days of the filing of this Amendment. PVM VI, the general partner of each of PVP VI and PVPFF VI, may be deemed to have voting, investment and dispositive power with respect to these securities. David Barrett, Brian Chee, Jonathan A.
Flint, Terrance G. McGuire, Amir Nashat, a member of the Issuer's board of directors, and Bryce Youngren are the managing members of PVM VI and may each be deemed to share voting, investment and dispositive power with respect to these
securities.

(2) Based on 51,962,889 shares of the Issuer's Common Stock, calculated as follows (i) 51,663,391 shares of
the Issuer's Common Stock outstanding as of November 8, 2022, as reported by the Issuer in the Form 10-Q plus (ii) 282,962 shares of the Issuer's Common Stock are shares underlying a warrant
issued to PVP VI and which is exercisable within 60 days of the filing of this Amendment plus (iii) 16,536 shares of the Issuer's Common Stock are shares underlying a warrant issued to PVPFF VI and which is exercisable within 60 days of the
filing of this Amendment.

------

CUSIP #80706P103 Page 7 of 13

---

| | |
|:---|:---|
| &nbsp;&nbsp;&nbsp; 1 | &nbsp;&nbsp;&nbsp;&nbsp;NAME OF REPORTING PERSONS<br>&nbsp;&nbsp;&nbsp;&nbsp;Jonathan A. Flint |
| &nbsp;&nbsp;&nbsp; 2 | &nbsp;&nbsp;&nbsp;&nbsp;CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP<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 |

---

---

| | | |
|:---|:---|:---|
| &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;4,046,925 (1) |
| &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;4,046,925 (1) |

---

---

| | |
|:---|:---|
| &nbsp;&nbsp;&nbsp; 9 | &nbsp;&nbsp;&nbsp;&nbsp;AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON<br>&nbsp;&nbsp;&nbsp;&nbsp;4,046,925 (1) |
| &nbsp;&nbsp;&nbsp;10 | &nbsp;&nbsp;&nbsp;&nbsp;CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES<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;7.8% (2) |
| &nbsp;&nbsp;&nbsp;12 | &nbsp;&nbsp;&nbsp;&nbsp;TYPE OF REPORTING PERSON<br>&nbsp;&nbsp;&nbsp;&nbsp;IN |

---

(1) 3,540,530 of such shares are held of record by PVP VI, 282,962 of such shares are shares underlying a warrant
issued to PVP VI and which is exercisable within 60 days of the filing of this Amendment, 206,897 of such shares are held of record by PVPFF VI and 16,536 of such shares are shares underlying a warrant issued to PVPFF VI and which is exercisable
within 60 days of the filing of this Amendment. PVM VI, the general partner of each of PVP VI and PVPFF VI, may be deemed to have voting, investment and dispositive power with respect to these securities. David Barrett, Brian Chee, Jonathan A.
Flint, Terrance G. McGuire, Amir Nashat, a member of the Issuer's board of directors, and Bryce Youngren are the managing members of PVM VI and may each be deemed to share voting, investment and dispositive power with respect to these
securities.

(2) Based on 51,962,889 shares of the Issuer's Common Stock, calculated as follows (i) 51,663,391 shares of
the Issuer's Common Stock outstanding as of November 8, 2022, as reported by the Issuer in the Form 10-Q plus (ii) 282,962 shares of the Issuer's Common Stock are shares underlying a warrant
issued to PVP VI and which is exercisable within 60 days of the filing of this Amendment plus (iii) 16,536 shares of the Issuer's Common Stock are shares underlying a warrant issued to PVPFF VI and which is exercisable within 60 days of the
filing of this Amendment.

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CUSIP #80706P103 Page 8 of 13

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| | |
|:---|:---|
| &nbsp;&nbsp;&nbsp; 1 | &nbsp;&nbsp;&nbsp;&nbsp;NAME OF REPORTING PERSONS<br>&nbsp;&nbsp;&nbsp;&nbsp;Terrance G. McGuire |
| &nbsp;&nbsp;&nbsp; 2 | &nbsp;&nbsp;&nbsp;&nbsp;CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP<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 |

---

---

| | | |
|:---|:---|:---|
| &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;4,046,925 (1) |
| &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;4,046,925 (1) |

---

---

| | |
|:---|:---|
| &nbsp;&nbsp;&nbsp; 9 | &nbsp;&nbsp;&nbsp;&nbsp;AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON<br>&nbsp;&nbsp;&nbsp;&nbsp;4,046,925 (1) |
| &nbsp;&nbsp;&nbsp;10 | &nbsp;&nbsp;&nbsp;&nbsp;CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES<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;7.8% (2) |
| &nbsp;&nbsp;&nbsp;12 | &nbsp;&nbsp;&nbsp;&nbsp;TYPE OF REPORTING PERSON<br>&nbsp;&nbsp;&nbsp;&nbsp;IN |

---

(1) 3,540,530 of such shares are held of record by PVP VI, 282,962 of such shares are shares underlying a warrant
issued to PVP VI and which is exercisable within 60 days of the filing of this Amendment, 206,897 of such shares are held of record by PVPFF VI and 16,536 of such shares are shares underlying a warrant issued to PVPFF VI and which is exercisable
within 60 days of the filing of this Amendment. PVM VI, the general partner of each of PVP VI and PVPFF VI, may be deemed to have voting, investment and dispositive power with respect to these securities. David Barrett, Brian Chee, Jonathan A.
Flint, Terrance G. McGuire, Amir Nashat, a member of the Issuer's board of directors, and Bryce Youngren are the managing members of PVM VI and may each be deemed to share voting, investment and dispositive power with respect to these
securities.

(2) Based on 51,962,889 shares of the Issuer's Common Stock, calculated as follows (i) 51,663,391 shares of
the Issuer's Common Stock outstanding as of November 8, 2022, as reported by the Issuer in the Form 10-Q plus (ii) 282,962 shares of the Issuer's Common Stock are shares underlying a warrant
issued to PVP VI and which is exercisable within 60 days of the filing of this Amendment plus (iii) 16,536 shares of the Issuer's Common Stock are shares underlying a warrant issued to PVPFF VI and which is exercisable within 60 days of the
filing of this Amendment.

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CUSIP #80706P103 Page 9 of 13

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| | |
|:---|:---|
| &nbsp;&nbsp;&nbsp; 1 | &nbsp;&nbsp;&nbsp;&nbsp;NAME OF REPORTING PERSONS<br>&nbsp;&nbsp;&nbsp;&nbsp;Amir Nashat |
| &nbsp;&nbsp;&nbsp; 2 | &nbsp;&nbsp;&nbsp;&nbsp;CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP<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 |

---

---

| | | |
|:---|:---|:---|
| &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;58,715 (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;4,046,925 (2) |
| &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;58,715 (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;4,046,925 (2) |

---

---

| | |
|:---|:---|
| &nbsp;&nbsp;&nbsp; 9 | &nbsp;&nbsp;&nbsp;&nbsp;AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON<br>&nbsp;&nbsp;&nbsp;&nbsp;4,105,640 (1)(2) |
| &nbsp;&nbsp;&nbsp;10 | &nbsp;&nbsp;&nbsp;&nbsp;CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES<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;7.9% (3) |
| &nbsp;&nbsp;&nbsp;12 | &nbsp;&nbsp;&nbsp;&nbsp;TYPE OF REPORTING PERSON<br>&nbsp;&nbsp;&nbsp;&nbsp;IN |

---

(1) Consists of (i) 7,441 shares held of record directly by Amir Nashat and (ii) 51,274 shares subject to stock
option awards that have been granted to Amir Nashat in his capacity as a director of the Issuer and that are exercisable as of or within 60 days of the filing of this Amendment.

(2) 3,540,530 of such shares are held of record by PVP VI, 282,962 of such shares are shares underlying a warrant
issued to PVP VI and which is exercisable within 60 days of the filing of this Amendment, 206,897 of such shares are held of record by PVPFF VI and 16,536 of such shares are shares underlying a warrant issued to PVPFF VI and which is exercisable
within 60 days of the filing of this Amendment. PVM VI, the general partner of each of PVP VI and PVPFF VI, may be deemed to have voting, investment and dispositive power with respect to these securities. David Barrett, Brian Chee, Jonathan A.
Flint, Terrance G. McGuire, Amir Nashat, a member of the Issuer's board of directors, and Bryce Youngren are the managing members of PVM VI and may each be deemed to share voting, investment and dispositive power with respect to these
securities.

(3) Based on 52,015,163 shares of the Issuer's Common Stock, calculated as follows: (i) 51,663,391 shares of
the Issuer's Common Stock outstanding as of November 8, 2022, as reported by the Issuer in the Form 10-Q plus (ii) 51,274 shares of the Issuer's Common Stock subject to stock option awards that
have been granted to Amir Nashat in his capacity as a director of the Issuer and that are exercisable as of or within 60 days of the filing of this Amendment plus (iii) 282,962 shares of the Issuer's Common Stock are shares underlying a warrant
issued to PVP VI and which is exercisable within 60 days of the filing of this Amendment plus (iv) 16,536 shares of the Issuer's Common Stock are shares underlying a warrant issued to PVPFF VI and which is exercisable within 60 days of the
filing of this Amendment.

------

CUSIP #80706P103 Page 10 of 13

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| | |
|:---|:---|
| &nbsp;&nbsp;&nbsp; 1 | &nbsp;&nbsp;&nbsp;&nbsp;NAME OF REPORTING PERSONS<br>&nbsp;&nbsp;&nbsp;&nbsp;Bryce Youngren |
| &nbsp;&nbsp;&nbsp; 2 | &nbsp;&nbsp;&nbsp;&nbsp;CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP<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 |

---

---

| | | |
|:---|:---|:---|
| &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;4,046,925 (1) |
| &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;4,046,925 (1) |

---

---

| | |
|:---|:---|
| &nbsp;&nbsp;&nbsp; 9 | &nbsp;&nbsp;&nbsp;&nbsp;AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON<br>&nbsp;&nbsp;&nbsp;&nbsp;4,046,925 (1) |
| &nbsp;&nbsp;&nbsp;10 | &nbsp;&nbsp;&nbsp;&nbsp;CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES<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;7.8% (2) |
| &nbsp;&nbsp;&nbsp;12 | &nbsp;&nbsp;&nbsp;&nbsp;TYPE OF REPORTING PERSON<br>&nbsp;&nbsp;&nbsp;&nbsp;IN |

---

(1) 3,540,530 of such shares are held of record by PVP VI, 282,962 of such shares are shares underlying a warrant
issued to PVP VI and which is exercisable within 60 days of the filing of this Amendment, 206,897 of such shares are held of record by PVPFF VI and 16,536 of such shares are shares underlying a warrant issued to PVPFF VI and which is exercisable
within 60 days of the filing of this Amendment. PVM VI, the general partner of each of PVP VI and PVPFF VI, may be deemed to have voting, investment and dispositive power with respect to these securities. David Barrett, Brian Chee, Jonathan A.
Flint, Terrance G. McGuire, Amir Nashat, a member of the Issuer's board of directors, and Bryce Youngren are the managing members of PVM VI and may each be deemed to share voting, investment and dispositive power with respect to these
securities.

(2) Based on 51,962,889 shares of the Issuer's Common Stock, calculated as follows (i) 51,663,391 shares of
the Issuer's Common Stock outstanding as of November 8, 2022, as reported by the Issuer in the Form 10-Q plus (ii) 282,962 shares of the Issuer's Common Stock are shares underlying a warrant
issued to PVP VI and which is exercisable within 60 days of the filing of this Amendment plus (iii) 16,536 shares of the Issuer's Common Stock are shares underlying a warrant issued to PVPFF VI and which is exercisable within 60 days of the
filing of this Amendment.

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CUSIP #80706P103 SCHEDULE 13G Page 11 of 13

<u>Introductory Note</u>: This Amendment No. 2 (the "Amendment") amends and supplements the Schedule 13G originally filed by the Reporting Persons with the Commission on February 14, 2019 and Amendment No. 1 filed with the Commission on February 11, 2022 (collectively, the "Original Schedule 13G"). Only those items that are hereby reported are amended; all other items reported in the Original Schedule 13G remain unchanged. Information given in response to each item shall be deemed incorporated by reference in all other items, as applicable. Capitalized terms not defined in this Amendment have the meanings ascribed to them in the Original Schedule 13G.

ITEM 4. <u>OWNERSHIP</u> 

The approximate percentages of Common Stock reported as beneficially owned by the Reporting Persons are based upon 51,663,391 shares of the Issuer's Common Stock outstanding as of November 8, 2022, as reported on the Form 10-Q.

The following information with respect to the ownership of the common stock of the Issuer by the Reporting Persons filing this Statement is provided as of December 31, 2022:

(a) <u>Amount beneficially owned</u>:

See Row 9 of cover page for each Reporting Person.

(b) <u>Percent of Class</u>:

See Row 11 of cover page for each Reporting Person.

(c) <u>Number of shares as to which such person has</u>:

(i) <u>Sole power to vote or to direct the vote</u>:

See Row 5 of cover page for each Reporting Person.

(ii) <u>Shared power to vote or to direct the vote</u>:

See Row 6 of cover page for each Reporting Person.

(iii) <u>Sole power to dispose or to direct the disposition of</u>:

See Row 7 of cover page for each Reporting Person.

(iv) <u>Shared power to dispose or to direct the disposition of</u>:

See Row 8 of cover page for each Reporting Person.

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CUSIP #80706P103 Page 12 of 13

<u>SIGNATURES</u> 

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.

Date: February 7, 2023

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| | |
|:---|:---|
| POLARIS VENTURE PARTNERS VI, L.P. | POLARIS VENTURE PARTNERS VI, L.P. |
| By: | Polaris Venture Management Co. VI, L.L.C. |
| By: | \* |
|  | Authorized Signatory |
| POLARIS VENTURE PARTNERS FOUNDERS' FUND VI, L.P. | POLARIS VENTURE PARTNERS FOUNDERS' FUND VI, L.P. |
| By: | Polaris Venture Management Co. VI, L.L.C. |
| By: | \* |
|  | Authorized Signatory |
| POLARIS VENTURE MANAGEMENT CO. VI, L.L.C. | POLARIS VENTURE MANAGEMENT CO. VI, L.L.C. |
| By: | \* |
|  | Authorized Signatory |
| JONATHAN A. FLINT | JONATHAN A. FLINT |
| By: | \* |
|  | Jonathan A. Flint |
| TERRANCE G. MCGUIRE | TERRANCE G. MCGUIRE |
| By: | \* |
|  | Terrance G. McGuire |
| BRYCE YOUNGREN | BRYCE YOUNGREN |
| By: | \* |
|  | Bryce Youngren |
| DAVID BARRETT | DAVID BARRETT |
| By: | \* |
|  | David Barrett |
| BRIAN CHEE | BRIAN CHEE |
| By: | \* |
|  | Brian Chee |

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CUSIP #80706P103 Page 13 of 13

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| | |
|:---|:---|
| AMIR NASHAT | AMIR NASHAT |
| By: | \* |
|  | Amir Nashat |
| \*By: | /s/ Lauren Crockett |
| Name: | Lauren Crockett |
| Title: | Attorney-in-Fact |

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[This Schedule 13G was executed pursuant to a Power of Attorney. Note that copies of the applicable Powers of Attorney are already on file with the appropriate agencies.]