Casdin entities boost Standard BioTools (LAB) stake with open‑market buys

Rhea-AI Filing Summary

Standard BioTools director and 10% owner entities associated with Eli Casdin reported a series of open‑market purchases of common stock. Casdin Partners Master Fund, L.P. bought 200,000 shares on August 22, 2025 at $1.2634, 200,000 shares on August 25 at a weighted average $1.2409, and 125,000 shares on August 26 at $1.2635.

After these trades, the Master Fund held 60,275,000 shares indirectly for the reporting group. Separate positions include 2,901,062 shares held directly by Eli Casdin, 13,939,637 shares held by Casdin Private Growth Equity Fund II, L.P., and 2,744,219 shares held by Casdin Private Growth Equity Fund, L.P.

Insights

Equity ownership and governance analyst

Casdin-affiliated funds increased their Standard BioTools equity stake through open‑market purchases.

Several Casdin-managed entities, which are directors and significant owners of Standard BioTools, reported open‑market purchases of common stock around $1.24–$1.26 per share. The trades were executed by Casdin Partners Master Fund, L.P., with indirect beneficial interests across related investment vehicles and Eli Casdin.

Post‑transaction, the Master Fund is shown with 60,275,000 shares, while other Casdin funds and Eli Casdin hold additional direct and indirect positions. The filing emphasizes that each reporting person only acknowledges beneficial ownership to the extent of its pecuniary interest, so actual economic exposure aligns with these disclosed interests.

SEC Form 4

FORM 4

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL

OMB Number:			3235-0287
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hours per response:			0.5

Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

Casdin Partners Master Fund, L.P.

(Last) (First) (Middle)

1350 AVENUE OF THE AMERICAS

SUITE 2600

(Street)

NEW YORK NY 10019

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
STANDARD BIOTOOLS INC. [ LAB ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

X	Director	X	10% Owner
	Officer (give title below)		Other (specify below)

3. Date of Earliest Transaction (Month/Day/Year)
08/22/2025

4. If Amendment, Date of Original Filed (Month/Day/Year)

6. Individual or Joint/Group Filing (Check Applicable Line)

	Form filed by One Reporting Person
X	Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price
Common Stock, $0.001 par value per share	08/22/2025		P		200,000	A	$1.2634	59,950,000	I	See footnote(1)
Common Stock, $0.001 par value per share	08/25/2025		P		200,000	A	$1.2409(2)	60,150,000	I	See footnote(1)
Common Stock, $0.001 par value per share	08/26/2025		P		125,000	A	$1.2635	60,275,000	I	See footnote(1)
Common Stock, $0.001 par value per share								2,901,062	D(3)
Common Stock, $0.001 par value per share								13,939,637	I	See footnote(4)
Common Stock, $0.001 par value per share								2,744,219	I	See footnote(5)

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares

1. Name and Address of Reporting Person^*

Casdin Partners Master Fund, L.P.

(Last) (First) (Middle)

1350 AVENUE OF THE AMERICAS

SUITE 2600

(Street)

NEW YORK NY 10019

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

X	Director	X	10% Owner
	Officer (give title below)		Other (specify below)

1. Name and Address of Reporting Person^*

Casdin Capital, LLC

(Last) (First) (Middle)

1350 AVENUE OF THE AMERICAS

SUITE 2600

(Street)

NEW YORK NY 10019

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

X	Director	X	10% Owner
	Officer (give title below)		Other (specify below)

1. Name and Address of Reporting Person^*

Casdin Partners GP, LLC

(Last) (First) (Middle)

1350 AVENUE OF THE AMERICAS

SUITE 2600

(Street)

NEW YORK NY 10019

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

X	Director	X	10% Owner
	Officer (give title below)		Other (specify below)

1. Name and Address of Reporting Person^*

Casdin Private Growth Equity Fund II, L.P.

(Last) (First) (Middle)

1350 AVENUE OF THE AMERICAS

SUITE 2600

(Street)

NEW YORK NY 10019

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

X	Director		10% Owner
	Officer (give title below)		Other (specify below)

1. Name and Address of Reporting Person^*

Casdin Private Growth Equity Fund II GP, LLC

(Last) (First) (Middle)

1350 AVENUE OF THE AMERICAS, SUITE 2600

(Street)

NEW YORK NY 10019

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

X	Director		10% Owner
	Officer (give title below)		Other (specify below)

1. Name and Address of Reporting Person^*

Casdin Private Growth Equity Fund, L.P.

(Last) (First) (Middle)

1350 AVENUE OF THE AMERICAS

SUITE 2600

(Street)

NEW YORK NY 10019

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

X	Director		10% Owner
	Officer (give title below)		Other (specify below)

1. Name and Address of Reporting Person^*

CASDIN PRIVATE GROWTH EQUITY FUND GP, LLC

(Last) (First) (Middle)

1350 AVENUE OF THE AMERICAS

SUITE 2600

(Street)

NEW YORK NY 10019

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

X	Director		10% Owner
	Officer (give title below)		Other (specify below)

1. Name and Address of Reporting Person^*

Casdin Eli

(Last) (First) (Middle)

1350 AVENUE OF THE AMERICAS

SUITE 2600

(Street)

NEW YORK NY 10019

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

X	Director	X	10% Owner
	Officer (give title below)		Other (specify below)

Explanation of Responses:

1. The securities are owned directly by Casdin Partners Master Fund, L.P. (the "Master Fund") and may be deemed to be indirectly beneficially owned by (i) Casdin Capital, LLC ("Casdin"), the investment adviser to the Master Fund, (ii) Casdin Partners GP, LLC (the "GP"), the general partner of the Master Fund, and (iii) Eli Casdin, the managing member of Casdin and the GP.

2. The price reported in Column 4 is a weighted average price. These shares were bought in multiple transactions within the range of $1.2311 to $1.2475. The Reporting Persons undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares bought at each separate price within the range set forth in this footnote.

3. The securities are owned directly by Eli Casdin.

4. The securities are owned directly by Casdin Private Growth Equity Fund II, L.P. (the "Equity Fund II") and may be deemed to be indirectly beneficially owned by (i) Casdin, the investment adviser to the Equity Fund II, and (ii) Eli Casdin, the managing member of Casdin.

5. The securities are owned directly by Casdin Private Growth Equity Fund, L.P. (the "Equity Fund") and may be deemed to be indirectly beneficially owned by (i) Casdin, the investment adviser to the Equity Fund, and (ii) Eli Casdin, the managing member of Casdin.

Remarks:

Eli Casdin has been deputized to represent the Reporting Persons on the board of directors of the Issuer. By virtue of Mr. Casdin's representation, for purposes of Section 16 of the Securities Exchange Act of 1934 (the "Exchange Act"), each of the Reporting Persons may be deemed directors by deputization of the Issuer. Each Reporting Person disclaims beneficial ownership in the securities reported on this Form 4 except to the extent of its pecuniary interest, if any, therein, and this report shall not be deemed to be an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or for any other purpose.

	Casdin Partners Master Fund, LP, By: Casdin Partners GP, LLC, its General Partner, By: /s/ Eli Casdin, Managing Member	08/26/2025
	Casdin Capital LLC, By: /s/ Eli Casdin, Managing Member	08/26/2025
	Casdin Partners GP LLC, By: /s/ Eli Casdin, Managing Member	08/26/2025
	Casdin Private Growth Equity Fund II, L.P., By: Casdin Private Growth Equity Fund II GP, LLC, its General Partner, By: /s/ Eli Casdin, Managing Member	08/26/2025
	Casdin Private Growth Equity Fund GP II, LLC, By: /s/ Eli Casdin, Managing Member	08/26/2025
	Casdin Private Growth Equity Fund, L.P., By: Casdin Private Growth Equity Fund II GP, LLC, its General Partner, By: /s/ Eli Casdin, Managing Member	08/26/2025
	Casdin Private Growth Equity Fund GP, LLC, By: /s/ Eli Casdin, Managing Member	08/26/2025
	/s/ Eli Casdin, Eli Casdin	08/26/2025
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.

FAQ

What insider purchases were reported for Standard BioTools (LAB) in this Form 4?

Casdin Partners Master Fund, L.P. reported three open‑market purchases of Standard BioTools common stock: 200,000 shares on August 22, 200,000 shares on August 25, and 125,000 shares on August 26, 2025, at prices around $1.24 to $1.26 per share.

Who executed the Standard BioTools (LAB) share purchases disclosed in the filing?

The purchases were executed by Casdin Partners Master Fund, L.P. The shares may be deemed indirectly beneficially owned by Casdin Capital, LLC, Casdin Partners GP, LLC, and Eli Casdin, who is the managing member of these entities, subject to each party’s pecuniary interest.

How many Standard BioTools (LAB) shares do Casdin entities hold after these transactions?

After the reported trades, Casdin Partners Master Fund, L.P. held 60,275,000 shares. Additional positions include 2,901,062 shares held directly by Eli Casdin, 13,939,637 shares held by Casdin Private Growth Equity Fund II, L.P., and 2,744,219 shares held by Casdin Private Growth Equity Fund, L.P.

At what prices did Casdin Partners Master Fund buy Standard BioTools (LAB) shares?

The Master Fund bought shares at reported prices of $1.2634 on August 22, 2025, a weighted average price of $1.2409 within a $1.2311–$1.2475 range on August 25, and $1.2635 on August 26, reflecting tightly grouped purchase levels near $1.24–$1.26 per share.

What is Eli Casdin’s role in the Standard BioTools (LAB) ownership structure?

Eli Casdin is a director and 10% owner by deputization and the managing member of several Casdin entities. He directly owns 2,901,062 shares and may be deemed to beneficially own additional shares held by Casdin-managed funds, limited to his pecuniary interests.

Do the Casdin reporting persons fully admit beneficial ownership of all LAB shares reported?

No. Each reporting person expressly disclaims beneficial ownership of the reported Standard BioTools securities except to the extent of its pecuniary interest. The Form 4 states the report should not be considered an admission of beneficial ownership for any other purpose under securities laws.