Net Power amends COO's option covering 240,000 shares

The amendment changes the post-termination exercise period while leaving the option count, $2.13 exercise price, vesting date and expiration date unchanged.

Available on EDGAR 11/06/2026 - 06:12 PM EST Accepted by SEC EDGAR 11/06/2026 - 06:12 PM EST Learn about SEC filing dates

Rhea-AI Filing Summary

Net Power Inc. President and COO Marc Horstman reported the deemed cancellation of an option covering 240,000 shares and the grant of an amended option covering the same number on November 4, 2026.

The amendment extends the period during which the vested option may be exercised following certain terminations of service. Its exercise price remains $2.13 per share; it became exercisable in full on June 2, 2026, and expires June 2, 2030. Horstman paid no consideration for the amendment.

Insider Trade Summary

2 transactions reported

Mixed 2 txns

Insider Horstman Marc

Role President and COO

Type	Security	Shares	Price	Value
Disposition	Stock Options F1, F2	240,000	$0.00	$0.00
Grant/Award	Stock Options F1, F2	240,000	$0.00	$0.00

Holdings After Transaction: Stock Options — 240,000 options (Direct)

Holdings Before and After: Stock Options, 240,000 to 240,000 options (Direct)

Footnotes (2)

1. F1. On November 4, 2026, the Issuer's board of directors approved an amendment to the stock option granted to the reporting person on June 2, 2025, which extends the period during which the vested option may be exercised following certain terminations of service. The amendment did not change the number of shares subject to the option, its exercise price, its vesting date or its expiration date, and the reporting person paid no consideration for it. The amendment is reported as the deemed cancellation of the original option and the grant of the amended option, each of which is exempt under Rule 16b-3.
2. F2. The option became exercisable in full on June 2, 2026.

Key Figures

Option deemed canceled: 240,000 shares Amended option granted: 240,000 shares Exercise price: $2.13 per share +2 more

5 metrics

Option deemed canceled 240,000 shares Stock option reported for November 4, 2026

Amended option granted 240,000 shares Stock option reported for November 4, 2026

Exercise price $2.13 per share Amended option

Exercisable in full June 2, 2026 Amended option

Expiration date June 2, 2030 Amended option

Key Terms

deemed cancellation, Rule 16b-3, exercisable in full

3 terms

deemed cancellation technical

"reported as the deemed cancellation of the original option"

Rule 16b-3 regulatory

"each of which is exempt under Rule 16b-3"

Rule 16b-3 is a Securities and Exchange Commission regulation that exempts certain routine, pre-approved transactions by company insiders from automatic liability for short-term trading profits. It acts like a safe harbor: if an insider follows a formal plan or the board approves specific transactions in advance, profits from buying and selling company stock within six months are not automatically reclaimed. Investors care because the rule clarifies when insider trades are permissible and reduces uncertainty about potential clawbacks.

exercisable in full financial

"The option became exercisable in full"

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

What did the NPWR option amendment change?

It extended the period during which Marc Horstman’s vested option could be exercised following certain terminations of service. The amendment did not change the option’s share count, exercise price, vesting date or expiration date.

AI-generated analysis. How Rhea-AI works. Not financial advice.

Form 4 Insider Transactions: What Each Field Means →

See more from StockTitan in Google Search and AI answers. Adds StockTitan as a preferred source · opens Google

Add on Google Not now

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
Estimated average burden
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^*

Horstman Marc

(Last) (First) (Middle)

C/O NET POWER INC.

11700 KATY FREEWAY, SUITE 700

(Street)

HOUSTON TEXAS 77079

(City) (State) (Zip)

UNITED STATES

(Country)

2. Issuer Name and Ticker or Trading Symbol
Net Power Inc. [ NPWR ]

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

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

2a. Foreign Trading Symbol
[NONE]

3. Date of Earliest Transaction (Month/Day/Year)
11/04/2026

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

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

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

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

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
Stock Options(1)	$2.13	11/04/2026		D			240,000	06/02/2026(2)	06/02/2030	Class A Common Stock	240,000	$0	0	D
Stock Options(1)	$2.13	11/04/2026		A		240,000		06/02/2026(2)	06/02/2030	Class A Common Stock	240,000	$0	240,000	D

Explanation of Responses:

1. On November 4, 2026, the Issuer's board of directors approved an amendment to the stock option granted to the reporting person on June 2, 2025, which extends the period during which the vested option may be exercised following certain terminations of service. The amendment did not change the number of shares subject to the option, its exercise price, its vesting date or its expiration date, and the reporting person paid no consideration for it. The amendment is reported as the deemed cancellation of the original option and the grant of the amended option, each of which is exempt under Rule 16b-3.

2. The option became exercisable in full on June 2, 2026.

	/s/ Marc Horstman	11/06/2026
	** 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.
* Form 4: SEC 1474 (03-26)