Form 4 Seaport Therapeutics, For: May 04 Filed by: PureTech Health plc

May 6, 2026 7:38 PM

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).

1. Name and Address of Reporting Person ^*

PureTech Health plc

(Last)

(First)

(Middle)

6 TIDE STREET, SUITE 400

(Street)

BOSTON

02210

(City)

(State)

(Zip)

2. Issuer Name and Ticker or Trading Symbol
Seaport Therapeutics, Inc. [ SPTX ]

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

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

3. Date of Earliest Transaction (Month/Day/Year)
05/04/2026

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)
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	Code	V	Amount	(A) or (D)	Price		6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
Common Stock	05/04/2026		C		12,736,014	A	⁽¹⁾	13,038,493	I	See footnote ⁽²⁾
Common Stock	05/04/2026		C		2,681,265	A	⁽¹⁾	15,719,758	I	See footnote ⁽²⁾
Common Stock	05/04/2026		C		965,255	A	⁽¹⁾	16,685,013	I	See footnote ⁽²⁾

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)
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)	Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares	8. Price of Derivative Security (Instr. 5)		10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
Series A-1 Preferred Stock	⁽¹⁾	05/04/2026		C			40,000,000	⁽¹⁾	⁽¹⁾	Common Stock	12,736,014	$ 0	0	I	See footnote ⁽²⁾
Series A-2 Preferred Stock	⁽¹⁾	05/04/2026		C			8,421,052	⁽¹⁾	⁽¹⁾	Common Stock	2,681,265	$ 0	0	I	See footnote ⁽²⁾
Series B Preferred Stock	⁽¹⁾	05/04/2026		C			3,031,578	⁽¹⁾	⁽¹⁾	Common Stock	965,255	$ 0	0	I	See footnote ⁽²⁾

Explanation of Responses:

1. Each share of Series A-1, Series A-2 and Series B Preferred Stock (collectively, the "Preferred Stock") was convertible into Common Stock of the Issuer on a one-for-3.1407 basis at the option of the holder, and automatically converted upon the closing of the Issuer's initial public offering without payment of further consideration. The Preferred Stock had no expiration date.

2. PureTech LYT, Inc. is the record holder of all of the securities reported in this Form 4. PureTech Health LLC is the sole owner of PureTech LYT, Inc. PureTech Health plc is the sole member of PureTech Health LLC, and has the power to direct the voting and disposition of securities held by PureTech LYT, Inc. and PureTech Health LLC.

	PureTech LYT, Inc., By: /s/ Robert Lyne	05/06/2026
	** Signature of Reporting Person	Date
	PureTech Health LLC, By: /s/ Robert Lyne	05/06/2026
	** Signature of Reporting Person	Date
	PureTech Health plc, By: /s/ Robert Lyne	05/06/2026
	** 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).
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Form 4 Seaport Therapeutics, For: May 04 Filed by: PureTech Health plc

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