Electra flags Westlake BioPartners as 10% holder

Westlake BioPartners funds disclose 10% ownership in Electra Therapeutics via automatic 1:1 conversion of redeemable preferred stock at Electra’s IPO closing.

Rhea-AI Filing Summary

Electra Therapeutics, Inc. (ETRA) reports that investment funds affiliated with Westlake BioPartners are ten percent owners, with their positions reported on an initial Form 3. The funds’ common stock was acquired upon the automatic 1:1 conversion of redeemable preferred stock when Electra’s initial public offering closed, without further consideration.

The shares are held directly by Westlake BioPartners Fund I, L.P. and Westlake BioPartners Fund II, L.P., with Westlake BioPartners GP I, LLC and Westlake BioPartners GP II, LLC as their respective general partners. Beth Seidenberg, as sole managing director of both general partners, has voting and dispositive power over these shares but disclaims Section 16 beneficial ownership except to the extent of any pecuniary interest.

Insider Trade Summary

2 transactions reported

Mixed 2 txns

Insider Westlake BioPartners Fund I, L.P., Westlake BioPartners GP I, LLC, Westlake BioPartners Fund II, L.P., Westlake BioPartners GP II, LLC

Role 10% Owner | 10% Owner | 10% Owner | 10% Owner

Type	Security	Shares	Price	Value
holding	Common Stock F3, F1	--	--	--
holding	Common Stock F3, F2	--	--	--

Holdings After Transaction: Common Stock — 6,347,539 shares (Indirect, See footnote)

Footnotes (3)

1. F1. Shares held directly by Westlake BioPartners Fund I, L.P. (Fund I). The general partner of Fund I is Westlake BioPartners GP I, LLC (GP I). GP I may be deemed to share voting and dispositive power with regard to the shares held directly by Fund I. Beth Seidenberg (Seidenberg) is the sole managing director of GP I and has voting and dispositive power over the shares held by Fund I. Seidenberg disclaims Section 16 beneficial ownership of the shares reported herein except to the extent of her pecuniary interest therein, if any, and the inclusion of these shares in this report shall not be deemed an admission of beneficial ownership of any of the reported shares for purposes of Section 16 or any other purpose.
2. F2. Shares held directly by Westlake BioPartners Fund II, L.P. (Fund II). The general partner of Fund II is Westlake BioPartners GP II, LLC (GP II). GP II may be deemed to share voting and dispositive power with regard to the shares held directly by Fund II. Seidenberg is the sole managing director of GP II and has voting and dispositive power over the shares held by Fund II. Seidenberg disclaims Section 16 beneficial ownership of the shares reported herein except to the extent of her pecuniary interest therein, if any, and the inclusion of these shares in this report shall not be deemed an admission of beneficial ownership of any of the reported shares for purposes of Section 16 or any other purpose.
3. F3. Shares acquired upon the automatic conversion of redeemable preferred stock on a 1:1 basis upon the closing of the Issuer's initial public offering without the payment of further consideration. Each Reporting Person had previously waived its right to voluntarily convert such redeemable preferred stock.

Key Figures

Conversion ratio: 1:1

1 metrics

Conversion ratio 1:1 Redeemable preferred stock automatically converted into common stock upon IPO closing

Key Terms

automatic conversion, redeemable preferred stock, initial public offering, voting and dispositive power, +1 more

5 terms

automatic conversion financial

"Shares acquired upon the automatic conversion of redeemable preferred stock"

redeemable preferred stock financial

"automatic conversion of redeemable preferred stock on a 1:1 basis"

A redeemable preferred stock is an ownership share that pays a steady dividend and gives holders priority over common shareholders for dividends and bankruptcy payouts, but can be bought back by the issuing company at a predetermined price or after a set date. It matters to investors because it combines income-like stability with limited upside—think of it as a preferred seat with an exit button the issuer can press—so you gain income and safety relative to common stock but face the risk of being forced to sell back at the issuer’s chosen price.

initial public offering financial

"upon the closing of the Issuer's initial public offering"

An initial public offering (IPO) is when a private company first sells its shares to the public and becomes a stock-listed company. It matters because it allows the company to raise money from a wide range of investors, helping it grow, while giving early shareholders a way to sell some of their ownership.

voting and dispositive power financial

"may be deemed to share voting and dispositive power with regard"

Section 16 beneficial ownership regulatory

"disclaims Section 16 beneficial ownership of the shares reported"

FAQ

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

What does Electra Therapeutics (ETRA) disclose about Westlake BioPartners’ ownership in this Form 3?

Electra Therapeutics discloses that Westlake BioPartners Fund I, L.P. and Fund II, L.P. are each reporting persons as ten percent owners, holding common stock indirectly through their general partners GP I and GP II.

How did Westlake BioPartners obtain its Electra Therapeutics (ETRA) common shares?

The filing states the shares were acquired upon the automatic conversion of redeemable preferred stock into common stock on a 1:1 basis upon the closing of Electra’s initial public offering, without payment of further consideration.

Who has voting and dispositive power over the Electra Therapeutics (ETRA) shares held by the Westlake funds?

Westlake BioPartners GP I, LLC and Westlake BioPartners GP II, LLC may be deemed to share voting and dispositive power over shares held by Fund I and Fund II, respectively, with Beth Seidenberg as sole managing director exercising that power.

What does Beth Seidenberg disclaim regarding Electra Therapeutics (ETRA) shares in this Form 3?

Beth Seidenberg disclaims Section 16 beneficial ownership of the reported Electra Therapeutics shares, except to the extent of her pecuniary interest, and the inclusion of these shares is not deemed an admission of beneficial ownership for any purpose.

Were any new Electra Therapeutics (ETRA) share purchases or sales reported in this Form 3?

No purchases or sales are reported; the Form 3 describes existing holdings of common stock resulting from the automatic conversion of redeemable preferred stock at the IPO closing.

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

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Available on EDGAR 09/21/2026 - 09:01 PM Accepted by SEC EDGAR 09/21/2026 - 09:01 PM Learn about SEC filing dates

SEC Form 3

FORM 3

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

INITIAL STATEMENT OF BENEFICIAL OWNERSHIP OF SECURITIES

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:			3235-0104
Estimated average burden
hours per response:			0.5

1. Name and Address of Reporting Person^*

Westlake BioPartners Fund I, L.P.

(Last) (First) (Middle)

C/O WESTLAKE BIOPARTNERS, LLC

3075 TOWNSGATE ROAD, SUITE 140

(Street)

WESTLAKE VILLAGE CALIFORNIA 91361

(City) (State) (Zip)

UNITED STATES

(Country)

2. Date of Event Requiring Statement (Month/Day/Year)
09/21/2026

3. Issuer Name and Ticker or Trading Symbol
Electra Therapeutics, Inc. [ ETRA ]

3a. Foreign Trading Symbol

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

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

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

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 Beneficially Owned
1. Title of Security (Instr. 4)	2. Amount of Securities Beneficially Owned (Instr. 4)	3. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	4. Nature of Indirect Beneficial Ownership (Instr. 5)
Common Stock	3,527,136(3)	I	See footnote(1)
Common Stock	2,820,403(3)	I	See footnote(2)

Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 4)	2. Date Exercisable and Expiration Date (Month/Day/Year)		3. Title and Amount of Securities Underlying Derivative Security (Instr. 4)		4. Conversion or Exercise Price of Derivative Security	5. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	6. Nature of Indirect Beneficial Ownership (Instr. 5)
	Date Exercisable	Expiration Date	Title	Amount or Number of Shares

1. Name and Address of Reporting Person^*

Westlake BioPartners Fund I, L.P.

(Last) (First) (Middle)

C/O WESTLAKE BIOPARTNERS, LLC

3075 TOWNSGATE ROAD, SUITE 140

(Street)

WESTLAKE VILLAGE CALIFORNIA 91361

(City) (State) (Zip)

UNITED STATES

(Country)

Relationship of Reporting Person(s) to Issuer

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

1. Name and Address of Reporting Person^*

Westlake BioPartners GP I, LLC

(Last) (First) (Middle)

C/O WESTLAKE BIOPARTNERS, LLC

3075 TOWNSGATE ROAD, SUITE 140

(Street)

WESTLAKE VILLAGE CALIFORNIA 91361

(City) (State) (Zip)

UNITED STATES

(Country)

Relationship of Reporting Person(s) to Issuer

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

1. Name and Address of Reporting Person^*

Westlake BioPartners Fund II, L.P.

(Last) (First) (Middle)

C/O WESTLAKE BIOPARTNERS, LLC

3075 TOWNSGATE ROAD, SUITE 140

(Street)

WESTLAKE VILLAGE CALIFORNIA 91361

(City) (State) (Zip)

UNITED STATES

(Country)

Relationship of Reporting Person(s) to Issuer

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

1. Name and Address of Reporting Person^*

Westlake BioPartners GP II, LLC

(Last) (First) (Middle)

C/O WESTLAKE BIOPARTNERS, LLC

3075 TOWNSGATE ROAD, SUITE 140

(Street)

WESTLAKE VILLAGE CALIFORNIA 91361

(City) (State) (Zip)

UNITED STATES

(Country)

Relationship of Reporting Person(s) to Issuer

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

Explanation of Responses:

1. Shares held directly by Westlake BioPartners Fund I, L.P. (Fund I). The general partner of Fund I is Westlake BioPartners GP I, LLC (GP I). GP I may be deemed to share voting and dispositive power with regard to the shares held directly by Fund I. Beth Seidenberg (Seidenberg) is the sole managing director of GP I and has voting and dispositive power over the shares held by Fund I. Seidenberg disclaims Section 16 beneficial ownership of the shares reported herein except to the extent of her pecuniary interest therein, if any, and the inclusion of these shares in this report shall not be deemed an admission of beneficial ownership of any of the reported shares for purposes of Section 16 or any other purpose.

2. Shares held directly by Westlake BioPartners Fund II, L.P. (Fund II). The general partner of Fund II is Westlake BioPartners GP II, LLC (GP II). GP II may be deemed to share voting and dispositive power with regard to the shares held directly by Fund II. Seidenberg is the sole managing director of GP II and has voting and dispositive power over the shares held by Fund II. Seidenberg disclaims Section 16 beneficial ownership of the shares reported herein except to the extent of her pecuniary interest therein, if any, and the inclusion of these shares in this report shall not be deemed an admission of beneficial ownership of any of the reported shares for purposes of Section 16 or any other purpose.

3. Shares acquired upon the automatic conversion of redeemable preferred stock on a 1:1 basis upon the closing of the Issuer's initial public offering without the payment of further consideration. Each Reporting Person had previously waived its right to voluntarily convert such redeemable preferred stock.

	By: /s/ Jennifer L. Kercher, as Attorney-in-Fact	09/21/2026
	** 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 5 (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 3: SEC 1473 (03-26)