SIGA Technologies (SIGA) CEO Diem Nguyen reports RSU grant and tax withholding

Rhea-AI Filing Summary

SIGA Technologies Chief Executive Officer Diem Nguyen reported equity compensation activity involving restricted stock units (RSUs) and common shares on March 13, 2026. Nguyen exercised RSUs into 85,045 shares of common stock upon vesting of one-third of RSUs originally granted on March 13, 2025.

As part of this vesting, 47,029 shares of common stock were withheld by the company at $5.26 per share to cover tax obligations, rather than being sold in the market. In a separate transaction the same day, Nguyen received a new grant of 272,243 RSUs, each representing a contingent right to one share of common stock that vests over three years in equal annual installments.

Following these transactions, Nguyen directly owned 138,767 shares of common stock and held 272,243 RSUs, reflecting routine compensation-related equity awards and associated tax withholding.

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

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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^*

Nguyen Diem

(Last) (First) (Middle)

C/O SIGA TECHNOLOGIES, INC.

31 EAST 62ND STREET

(Street)

NEW YORK NY 10065

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
SIGA TECHNOLOGIES INC [ SIGA ]

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

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

3. Date of Earliest Transaction (Month/Day/Year)
03/13/2026

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

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

X	Form filed by One Reporting Person
	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, par value $.0001 per share	03/13/2026		M		85,045(1)	A	$0	185,796	D
Common Stock, par value $.0001 per share	03/13/2026		F		47,029(2)	D	$5.26	138,767	D

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
Restricted Stock Units	(3)	03/13/2026		M			85,045	(3)	(3)	Common Stock, par value $.0001 per share	85,045	$0	170,092	D
Restricted Stock Units	(3)	03/13/2026		A		272,243		(3)	(3)	Common Stock, par value $.0001 per share	272,243	$0	272,243	D

Explanation of Responses:

1. Represents the acquisition of Common Stock from the vesting of one-third of the restricted stock units ("RSUs") granted on March 13, 2025.

2. Represents the withholding by the Issuer of shares of Common Stock (based on $5.26 per share, the closing stock price on March 13, 2026) to satisfy tax withholding obligations associated with the vesting of RSUs and the consequent issuance of Common Stock.

3. RSUs represent contingent rights to receive Common Stock on a one-for-one basis. The RSUs vest over three years, one-third on each of the first three anniversaries of the date of grant.

	/s/ Diem Nguyen	03/17/2026
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
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** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
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FAQ

What equity transactions did SIGA (SIGA) CEO Diem Nguyen report?

Diem Nguyen reported routine equity compensation activity, including RSU vesting into 85,045 common shares and a new grant of 272,243 RSUs. Shares were also withheld to cover taxes related to the RSU vesting and issuance.

How many SIGA common shares did Diem Nguyen receive from RSU vesting?

Nguyen acquired 85,045 SIGA common shares from the vesting of one-third of RSUs granted on March 13, 2025. These shares were issued at no cash cost as part of previously awarded equity compensation.

How many SIGA shares were withheld for taxes in this Form 4?

The issuer withheld 47,029 SIGA common shares, valued at $5.26 per share, to satisfy tax obligations from RSU vesting and related share issuance. This withholding is not an open-market sale but a tax payment mechanism.

What new RSU grant did SIGA CEO Diem Nguyen receive?

Nguyen received a new grant of 272,243 restricted stock units, each convertible into one SIGA common share. These RSUs vest over three years, in equal one-third installments on the first three anniversaries of the grant date.

What are Diem Nguyen’s SIGA share holdings after these transactions?

After the reported transactions, Nguyen held 138,767 SIGA common shares directly and 272,243 RSUs. The RSUs represent additional potential shares that may be delivered as they vest over the three-year schedule.

Do these SIGA Form 4 transactions indicate an open-market sale by the CEO?

No open-market sale is reported. Shares were acquired through RSU vesting and a new RSU grant, while 47,029 shares were withheld by the company solely to cover tax liabilities associated with the vesting.