Harvard Bioscience (HBIO) CEO adds shares and holds major RSU awards

Rhea-AI Filing Summary

Harvard Bioscience Chief Executive Officer John D. Duke bought 5,000 shares of common stock in an open-market purchase at $5.01 per share on March 16, 2026, bringing his directly held common stock to 105,000 shares.

His reported holdings include 50,000 restricted stock units that vest in three equal installments on August 8, 2026, 2027 and 2028, plus 50,000 performance-based RSUs that may vest based on relative total shareholder return versus the Russell 2000 index over the period from August 8, 2025 to the earlier of July 30, 2028 or a change of control, with a maximum payout of 150% of the target RSU amount. The RSU figures have been adjusted to reflect a 10-for-1 reverse stock split on March 13, 2026.

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

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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^*

Duke John D

(Last) (First) (Middle)

C/O HARVARD BIOSCIENCE, INC.

84 OCTOBER HILL ROAD

(Street)

HOLLISTON MA 01746

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
HARVARD BIOSCIENCE INC [ HBIO ]

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)
03/16/2026

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	03/16/2026		P		5,000	A	$5.01	105,000(1)(2)	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

Explanation of Responses:

1. Includes (a) 5,000 shares of common stock purchased on March 16, 2026, (b) an award of 50,000 restricted stock units (RSUs) that will vest in three equal installments on August 8, 2026, 2027 and 2028, subject to the terms set forth in an award agreement between the Issuer and the Reporting Person and (c) an award of 50,000 RSUs with performance based vesting conditions. These RSUs will vest upon the achievement of a relative total shareholder return of the Issuer's common stock during the period from August 8, 2025 to the earlier of (i) July 30, 2028, and (ii) the date of a change of control, measured relative to the Russell2000 index, subject to the terms set forth in an award agreement between the Issuer and the Reporting Person. The target number of these RSUs that may be earned is reported above; the maximum amount is 150% of the number reported.

2. On March 13, 2026, the common stock of Harvard Bioscience, Inc. underwent a reverse stock split in a ratio of 10-for-1. The 50,000 restricted stock units referenced in Footnote 1(b) were previously reported as covering 500,000 restricted stock units and the 50,000 restricted stock units referenced in Footnote 1(c) were previously reported as covering 500,000 restricted stock units. These numbers have been adjusted to reflect the stock split that occurred on March 13, 2026.

	/s/ John D Duke	03/17/2026
	** 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.
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FAQ

What insider transaction did HBIO CEO John D. Duke report?

John D. Duke reported buying 5,000 shares of Harvard Bioscience common stock in the open market at $5.01 per share. Following this transaction, his directly held position in the company’s common stock totals 105,000 shares, according to the Form 4 disclosure.

How many Harvard Bioscience (HBIO) shares does the CEO hold after this trade?

After the reported open-market purchase, CEO John D. Duke directly holds 105,000 shares of Harvard Bioscience common stock. This amount includes the 5,000 shares purchased on March 16, 2026, as reflected in the Form 4 filing’s ownership table and accompanying footnotes.

At what price did the HBIO CEO buy additional shares on March 16, 2026?

The CEO bought 5,000 Harvard Bioscience common shares at an average price of $5.01 per share in an open-market transaction. This price is specifically reported in the Form 4, which details both the number of shares acquired and the per-share purchase price.

What restricted stock units does the HBIO CEO currently have?

John D. Duke’s holdings include 50,000 time-based RSUs vesting in three equal installments on August 8, 2026, 2027 and 2028. He also holds 50,000 performance-based RSUs that may vest based on relative total shareholder return versus the Russell 2000 index over a defined period.

How do the performance-based RSUs for HBIO’s CEO vest?

The 50,000 performance-based RSUs vest upon achieving a relative total shareholder return of Harvard Bioscience’s stock versus the Russell 2000 index between August 8, 2025 and the earlier of July 30, 2028 or a change of control. The maximum payout is 150% of the target RSU amount.

What reverse stock split affected HBIO’s reported RSU amounts?

On March 13, 2026, Harvard Bioscience common stock underwent a 10-for-1 reverse stock split. As a result, RSU awards previously reported as 500,000 units each are now reported as 50,000 units each, with all figures adjusted to reflect the split in the Form 4 footnotes.