SCHEDULE 13D

CUSIP No.

61225M102

1

Name of reporting person

Versant Venture Capital VI, L.P.

2

Check the appropriate box if a member of a Group (See Instructions)

(a)

(b)

3

SEC use only

4

Source of funds (See Instructions)

WC

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

Checkbox not checked

6

Citizenship or place of organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 2,236,708.00
8	Shared Voting Power 0.00
9	Sole Dispositive Power 2,236,708.00
10	Shared Dispositive Power 0.00

11

Aggregate amount beneficially owned by each reporting person

2,236,708.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

Checkbox not checked

13

Percent of class represented by amount in Row (11)

3.4 %

14

Type of Reporting Person (See Instructions)

PN

Comment for Type of Reporting Person:

All shares are held by Versant VI (as defined in Item 2(a) of the Original Schedule 13D). Versant Ventures VI GP-GP (as defined in Item 2(a) of the Original Schedule 13D) is the general partner of Versant Ventures VI GP (as defined in Item 2(a) of the Original Schedule 13D), which is the general partner of Versant VI. Each of Versant Ventures VI GP-GP and Versant Ventures VI GP may be deemed to share voting, investment and dispositive power with respect to the shares held by Versant VI. The percentage in Row 13 is based on 65,117,761 shares of the Issuer's Common Stock (as defined in Item 1 of the Original Schedule 13D) outstanding as of October 31, 2025, as set forth in the Issuer's quarterly report on Form 10-Q for the quarter ended September 30, 2025, filed with the United States Securities and Exchange Commission (the "Commission") on November 6, 2025 (the "Form 10-Q").

SCHEDULE 13D

CUSIP No.

61225M102

1

Name of reporting person

Versant Ventures VI GP, L.P.

2

Check the appropriate box if a member of a Group (See Instructions)

(a)

(b)

3

SEC use only

4

Source of funds (See Instructions)

AF

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

Checkbox not checked

6

Citizenship or place of organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 2,236,708.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 2,236,708.00

11

Aggregate amount beneficially owned by each reporting person

2,236,708.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

Checkbox not checked

13

Percent of class represented by amount in Row (11)

3.4 %

14

Type of Reporting Person (See Instructions)

PN

Comment for Type of Reporting Person:

All shares are held by Versant VI. Versant Ventures VI GP-GP is the general partner of Versant Ventures VI GP, which is the general partner of Versant VI. Each of Versant Ventures VI GP-GP and Versant Ventures VI GP may be deemed to share voting, investment and dispositive power with respect to the shares held by Versant VI. The percentage in Row 13 is based on 65,117,761 shares of the Issuer's Common Stock outstanding as of October 31, 2025, as reported by the Issuer in the Form 10-Q.

SCHEDULE 13D

CUSIP No.

61225M102

1

Name of reporting person

Versant Ventures VI GP-GP, LLC

2

Check the appropriate box if a member of a Group (See Instructions)

(a)

(b)

3

SEC use only

4

Source of funds (See Instructions)

AF

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

Checkbox not checked

6

Citizenship or place of organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 2,236,708.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 2,236,708.00

11

Aggregate amount beneficially owned by each reporting person

2,236,708.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

Checkbox not checked

13

Percent of class represented by amount in Row (11)

3.4 %

14

Type of Reporting Person (See Instructions)

OO

Comment for Type of Reporting Person:

All shares are held by Versant VI. Versant Ventures VI GP-GP is the general partner of Versant Ventures VI GP, which is the general partner of Versant VI. Each of Versant Ventures VI GP-GP and Versant Ventures VI GP may be deemed to share voting, investment and dispositive power with respect to the shares held by Versant VI. The percentage in Row 13 is based on 65,117,761 shares of the Issuer's Common Stock outstanding as of October 31, 2025, as reported by the Issuer in the Form 10-Q.

SCHEDULE 13D

CUSIP No.

61225M102

1

Name of reporting person

Versant Vantage I, L.P.

2

Check the appropriate box if a member of a Group (See Instructions)

(a)

(b)

3

SEC use only

4

Source of funds (See Instructions)

WC

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

Checkbox not checked

6

Citizenship or place of organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 1,013,361.00
8	Shared Voting Power 0.00
9	Sole Dispositive Power 1,013,361.00
10	Shared Dispositive Power 0.00

11

Aggregate amount beneficially owned by each reporting person

1,013,361.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

Checkbox not checked

13

Percent of class represented by amount in Row (11)

1.6 %

14

Type of Reporting Person (See Instructions)

PN

Comment for Type of Reporting Person:

All shares are held by Versant Vantage I (as defined in item 2(a) of the Original Schedule 13D). Versant Vantage I GP (as defined in item 2(a) of the Original Schedule 13D) is the general partner of Versant Vantage I, and Versant Vantage I GP-GP (as defined in item 2(a) of the Original Schedule 13D) is the general partner of Versant Vantage I GP. Each of Versant Vantage I GP and Versant Vantage I GP-GP share voting, investment and dispositive power over the shares held by Versant Vantage I. The percentage in Row 13 is based on 65,117,761 shares of the Issuer's Common Stock outstanding as of October 31, 2025, as reported by the Issuer in the Form 10-Q.

SCHEDULE 13D

CUSIP No.

61225M102

1

Name of reporting person

Versant Vantage I GP, L.P.

2

Check the appropriate box if a member of a Group (See Instructions)

(a)

(b)

3

SEC use only

4

Source of funds (See Instructions)

AF

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

Checkbox not checked

6

Citizenship or place of organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 1,013,361.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 1,013,361.00

11

Aggregate amount beneficially owned by each reporting person

1,013,361.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

Checkbox not checked

13

Percent of class represented by amount in Row (11)

1.6 %

14

Type of Reporting Person (See Instructions)

PN

Comment for Type of Reporting Person:

All shares are held by Versant Vantage I. Versant Vantage I GP is the general partner of Versant Vantage I, and Versant Vantage I GP-GP is the general partner of Versant Vantage I GP. Each of Versant Vantage I GP and Versant Vantage I GP-GP share voting, investment and dispositive power over the shares held by Versant Vantage I. The percentage in Row 13 is based on 65,117,761 shares of the Issuer's Common Stock outstanding as of October 31, 2025, as reported by the Issuer in the Form 10-Q.

SCHEDULE 13D

CUSIP No.

61225M102

1

Name of reporting person

Versant Vantage I GP-GP, LLC

2

Check the appropriate box if a member of a Group (See Instructions)

(a)

(b)

3

SEC use only

4

Source of funds (See Instructions)

AF

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

Checkbox not checked

6

Citizenship or place of organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 1,013,361.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 1,013,361.00

11

Aggregate amount beneficially owned by each reporting person

1,013,361.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

Checkbox not checked

13

Percent of class represented by amount in Row (11)

1.6 %

14

Type of Reporting Person (See Instructions)

OO

Comment for Type of Reporting Person:

All shares are held by Versant Vantage I. Versant Vantage I GP is the general partner of Versant Vantage I, and Versant Vantage I GP-GP is the general partner of Versant Vantage I GP. Each of Versant Vantage I GP and Versant Vantage I GP-GP share voting, investment and dispositive power over the shares held by Versant Vantage I. The percentage in Row 13 is based on 65,117,761 shares of the Issuer's Common Stock outstanding as of October 31, 2025, as reported by the Issuer in the Form 10-Q.

SCHEDULE 13D

Item 1.

Security and Issuer

(a)

Title of Class of Securities:

Common Stock, par value $0.0001 per share

(b)

Name of Issuer:

Monte Rosa Therapeutics, Inc.

(c)

Address of Issuer's Principal Executive Offices:

321 Harrison Avenue, Suite 900, Boston, MASSACHUSETTS , 02118.

Item 1 Comment:

This Amendment No. 6 (this "Amendment") amends and supplements the Schedule 13D originally filed by the Reporting Persons with the Commission on July 8, 2021, as amended by Amendment No. 1 filed with the Commission on November 9, 2023, Amendment No. 2 filed with the Commission on August 12, 2024, Amendment No. 3 filed with the Commission on September 24, 2024, Amendment No. 4 filed with the Commission on October 30, 2024, and Amendment No. 5 filed with the Commission on November 12, 2025 (collectively, the "Original Schedule 13D"). Only those items that are hereby reported are amended; all other items reported in the Original Schedule 13D 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 13D. The information reported in this Amendment is based on the Reporting Persons' holdings as of January 8, 2026. The aggregate percentage ownership of the Reporting Persons is 4.99%, calculated by taking 3,250,069 aggregate shares of Common Stock held by the Reporting Persons, which consists of (i) 2,236,708 shares of Common Stock held by Versant VI plus (ii) 1,013,361 shares of Common Stock held by Versant Vantage I and dividing it by 65,117,761 shares of Common Stock outstanding as of October 31, 2025, as reported by the Issuer in the Form 10-Q.

Item 5.

Interest in Securities of the Issuer

(a)

See Items 7-11 and 13 of the cover pages of this Amendment for each Reporting Person and the corresponding comments.

(b)

See Items 7-11 and 13 of the cover pages of this Amendment for each Reporting Person and the corresponding comments.

(c)

On November 19, 2025, Versant VI sold 15,200 shares of Common Stock at a weighted average price per share of $14.2503 for aggregate proceeds of approximately $216,605.02. On December 4, 2025, Versant VI effected a pro rata distribution without additional consideration of 500,030 shares of Common Stock to its limited partners. On December 16, 2025, Versant VI sold 10,205 shares of Common Stock at a price per share of $17.64 for aggregate proceeds of approximately $180,016.20. On January 7, 2026, Versant VI sold 572,526 shares of Common Stock at a weighted average price per share of $23.3304 for aggregate proceeds of approximately $13,357,260.59. On January 8, 2026, Versant Vantage I effected a pro rata distribution without additional consideration of 560,092 shares of Common Stock to its limited partners.

(e)

January 8, 2026

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.

Versant Venture Capital VI, L.P.

Signature:	/s/Max Eisenberg
Name/Title:	Max Eisenberg/COO of Versant Ventures VI GP-GP, LLC, the GP of Versant Ventures VI GP, L.P., the GP of Versant Venture Capital VI, L.P.
Date:	01/09/2026

Versant Ventures VI GP, L.P.

Signature:	/s/Max Eisenberg
Name/Title:	Max Eisenberg/COO of Versant Ventures VI GP-GP, LLC, the General Partner of Versant Ventures VI GP, L.P.
Date:	01/09/2026

Versant Ventures VI GP-GP, LLC

Signature:	/s/Max Eisenberg
Name/Title:	Max Eisenberg/COO
Date:	01/09/2026

Versant Vantage I, L.P.

Signature:	/s/Max Eisenberg
Name/Title:	Max Eisenberg/COO of Versant Vantage I GP-GP, LLC, the GP of Versant Vantage I GP, L.P., the GP of Versant Vantage I, L.P.
Date:	01/09/2026

Versant Vantage I GP, L.P.

Signature:	/s/Max Eisenberg
Name/Title:	Max Eisenberg/COO of Versant Vantage I GP-GP, LLC, the General Partner of Versant Vantage I GP, L.P.
Date:	01/09/2026

Versant Vantage I GP-GP, LLC

Signature:	/s/Max Eisenberg
Name/Title:	Max Eisenberg/COO
Date:	01/09/2026