Insider filing report for Changes in Beneficial Ownership
- Schedule 13G & 13D forms are used to report a party's ownership of stock which exceeds 5% of a company's total stock issue.
- Schedule 13G is a shorter version of Schedule 13D with fewer reporting requirements.
"Insiders might sell their shares for any number of reasons, but they buy them for only one: they think the price will rise"
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- Peter Lynch
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SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549 |
SCHEDULE 13D
Under the Securities Exchange Act of 1934
(Amendment No. 4)*
|
Quantum-Si Inc (Name of Issuer) |
Class A common stock, par value $0.0001 per share, Class B common stock, par value $0.0001 per share (Title of Class of Securities) |
74765K105 (CUSIP Number) |
Jonathan M. Rothberg, Ph.D. c/o Quantum-Si Incorporated, 29 Business Park Drive Branford, CT, 06405 (866) 688-7374 (Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications) |
09/09/2025 (Date of Event Which Requires Filing of This Statement) |
If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§ 240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box.


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).
SCHEDULE 13D
|
| CUSIP No. | 74765K105 |
| 1 |
Name of reporting person
ROTHBERG JONATHAN M | ||||||||
| 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)
PF | ||||||||
| 5 |
Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)
![]() | ||||||||
| 6 | Citizenship or place of organization
UNITED STATES
| ||||||||
| Number of Shares Beneficially Owned by Each Reporting Person With: |
| ||||||||
| 11 | Aggregate amount beneficially owned by each reporting person
14,276,415.00 | ||||||||
| 12 | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)
![]() | ||||||||
| 13 | Percent of class represented by amount in Row (11)
7.8 % | ||||||||
| 14 | Type of Reporting Person (See Instructions)
IN |
Comment for Type of Reporting Person:
This Reporting Person's Table is for Class A common stock. Rows 7, 9 and 11 consists of (i) 2,568,443 shares of Class A common stock of Quantum-Si Incorporated (the ''Issuer'') held by Jonathan M. Rothberg, Ph.D., (ii) stock options to purchase 543,642 shares of Class A common stock of the Issuer which are exercisable within 60 days of September 9, 2025, held by Dr. Jonathan M. Rothberg and (iii) an aggregate of 8,973,841 shares of Class A common stock of the Issuer held by entities owned by trusts created for the benefit of Dr. Jonathan Rothberg's children, including shares of Class A common stock previously distributed from 2012 JMR Trust Common, LLC. Rows 8, 10 and 11 consists of (i) 1,917,067 shares of Class A common stock of the Issuer held by 23rd Century Capital LLC, and (ii) 273,422 shares of Class A common stock of the Issuer held by Dr. Jonathan Rothberg's spouse, Bonnie E. Gould Rothberg, M.D. Row 13 is calculated based on 182,557,698 shares of Class A common stock of the Issuer outstanding as of July 31, 2025.
SCHEDULE 13D
|
| CUSIP No. | 74765K105 |
| 1 |
Name of reporting person
ROTHBERG JONATHAN M. | ||||||||
| 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)
PF | ||||||||
| 5 |
Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)
![]() | ||||||||
| 6 | Citizenship or place of organization
UNITED STATES
| ||||||||
| Number of Shares Beneficially Owned by Each Reporting Person With: |
| ||||||||
| 11 | Aggregate amount beneficially owned by each reporting person
19,937,500.00 | ||||||||
| 12 | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)
![]() | ||||||||
| 13 | Percent of class represented by amount in Row (11)
100 % | ||||||||
| 14 | Type of Reporting Person (See Instructions)
IN |
Comment for Type of Reporting Person:
This Reporting Person's Table is for Class B common stock. Rows 7, 9 and 11 consists of (i) 17,943,750 shares of Class B common stock of the Issuer held by 4C Holdings I, LLC and (ii) 1,993,750 shares of Class B common stock of the Issuer held by 4C Holdings V, LLC. Row 13 is calculated based on 19,937,500 shares of Class B common stock of the Issuer outstanding as of July 31, 2025.
SCHEDULE 13D
|
| CUSIP No. | 74765K105 |
| 1 |
Name of reporting person
23rd Century Capital 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)
PF | ||||||||
| 5 |
Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)
![]() | ||||||||
| 6 | Citizenship or place of organization
DELAWARE
| ||||||||
| Number of Shares Beneficially Owned by Each Reporting Person With: |
| ||||||||
| 11 | Aggregate amount beneficially owned by each reporting person
1,917,067.00 | ||||||||
| 12 | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)
![]() | ||||||||
| 13 | Percent of class represented by amount in Row (11)
1.05 % | ||||||||
| 14 | Type of Reporting Person (See Instructions)
OO |
Comment for Type of Reporting Person:
This Reporting Person's table is for Class A common stock. Row 13 is calculated based on 182,557,698 shares of Class A common stock of the Issuer outstanding as of July 31, 2025.
SCHEDULE 13D
|
| CUSIP No. | 74765K105 |
| 1 |
Name of reporting person
2012 JMR Trust Common, 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)
PF | ||||||||
| 5 |
Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)
![]() | ||||||||
| 6 | Citizenship or place of organization
DELAWARE
| ||||||||
| Number of Shares Beneficially Owned by Each Reporting Person With: |
| ||||||||
| 11 | Aggregate amount beneficially owned by each reporting person
| ||||||||
| 12 | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)
![]() | ||||||||
| 13 | Percent of class represented by amount in Row (11)
0 % | ||||||||
| 14 | Type of Reporting Person (See Instructions)
OO |
Comment for Type of Reporting Person:
This Reporting Person's table is for Class A common stock. Row 13 is calculated based on 182,557,698 shares of Class A common stock of the Issuer outstanding as of July 31, 2025.
SCHEDULE 13D
|
| CUSIP No. | 74765K105 |
| 1 |
Name of reporting person
4C Holdings I, 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)
PF | ||||||||
| 5 |
Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)
![]() | ||||||||
| 6 | Citizenship or place of organization
DELAWARE
| ||||||||
| Number of Shares Beneficially Owned by Each Reporting Person With: |
| ||||||||
| 11 | Aggregate amount beneficially owned by each reporting person
17,943,750.00 | ||||||||
| 12 | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)
![]() | ||||||||
| 13 | Percent of class represented by amount in Row (11)
90 % | ||||||||
| 14 | Type of Reporting Person (See Instructions)
OO |
Comment for Type of Reporting Person:
This Reporting Person's table is for Class B common stock. Row 13 is calculated based on 19,937,500 shares of Class B common stock of the Issuer outstanding as of July 31, 2025.
SCHEDULE 13D
|
| CUSIP No. | 74765K105 |
| 1 |
Name of reporting person
4C Holdings V, 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)
PF | ||||||||
| 5 |
Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)
![]() | ||||||||
| 6 | Citizenship or place of organization
DELAWARE
| ||||||||
| Number of Shares Beneficially Owned by Each Reporting Person With: |
| ||||||||
| 11 | Aggregate amount beneficially owned by each reporting person
1,993,750.00 | ||||||||
| 12 | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)
![]() | ||||||||
| 13 | Percent of class represented by amount in Row (11)
10 % | ||||||||
| 14 | Type of Reporting Person (See Instructions)
OO |
Comment for Type of Reporting Person:
This Reporting Person's table is for Class B common stock. Row 13 is calculated based on 19,937,500 shares of Class B common stock of the Issuer outstanding as of July 31, 2025.
SCHEDULE 13D
|
| Item 1. | Security and Issuer | |
| (a) | Title of Class of Securities:
Class A common stock, par value $0.0001 per share, Class B common stock, par value $0.0001 per share | |
| (b) | Name of Issuer:
Quantum-Si Inc | |
| (c) | Address of Issuer's Principal Executive Offices:
29 BUSINESS PARK DRIVE, BRANFORD,
CONNECTICUT
, 06405. | |
Item 1 Comment:
Explanatory Note Amendment No. 4 to Schedule 13D ("Amendment No. 4") amends and supplements the Schedule 13D dated June 18, 2021, as amended by Amendment No. 1 filed on September 13, 2023, Amendment No. 2 filed on September 17, 2024 and Amendment No. 3 filed on December 31, 2024 (collectively, as amended, the "Schedule 13D") relating to the Class A common stock, par value $0.0001 per share ("Class A common stock"), and Class B common stock, par value $0.0001 per share, of Quantum-Si Incorporated, a Delaware corporation. Information reported in the Schedule 13D remains in effect except to the extent that it is amended, restated or superseded by information contained in this Amendment No. 4. Capitalized terms used but not defined herein have the meanings ascribed to them in the Schedule 13D. | ||
| Item 4. | Purpose of Transaction | |
In connection with estate planning, entities owned by trusts created for the benefit of Dr. Jonathan Rothberg's children have entered into a trading plan pursuant to Rule 10b5-1 under the Securities Exchange Act of 1934, as amended (the "Plan"), a copy of which is attached hereto as Exhibit 5. Pursuant to the Plan, sales of up to 8,973,841 shares of Class A common stock may be effected during the plan sales period beginning following the cooling-off period contained in Rule 10b5-1(c) on January 14, 2026 and ending on January 14, 2027 in accordance with the terms and conditions of the Plan. The sale of shares of Class A common stock under the Plan is subject to minimum price parameters included in the Plan, and there is no assurance that any shares of Class A common stock will be sold under the Plan. | ||
| Item 7. | Material to be Filed as Exhibits. | |
Item 7 of the Schedule 13D is hereby amended by adding the following exhibit: 5. Rule 10b5-1 Trading Plan | ||
| 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.
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