PEN

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UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

February 25, 2026 Date of Report (Date of earliest event reported)

Penumbra, Inc. (Exact name of registrant as specified in its charter)

Delaware001-3755705-0605598 (State or other jurisdiction of incorporation or organization)(Commission File No.)(I.R.S. employer identification number)

One Penumbra Place Alameda, CA 94502 (Address of principal executive offices, including zip code)

(510) 748-3200 (Registrant’s telephone number, including area code)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligations of the registrant under any of the following provisions: ☐Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425) ☐Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12) ☐Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b)) ☐Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:

Title of each classTrading SymbolName of each exchange on which registered Common Stock, Par value $0.001 per sharePENThe New York Stock Exchange

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter). Emerging growth company ☐ If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. o

Item 2.02.Results of Operations and Financial Condition.

On February 25, 2026, Penumbra, Inc. issued a press release announcing financial results for the fourth fiscal quarter and year ended December 31, 2025. A copy of the press release is furnished as Exhibit 99.1 to this Current Report on Form 8-K and is incorporated herein by reference.

The information furnished on this Current Report on Form 8-K, including the attached exhibit, shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference into any other filing under the Securities Act of 1933, as amended, or the Exchange Act, regardless of any general incorporation language in such a filing, except as expressly set forth by specific reference in such a filing.

Item 9.01.Financial Statements and Exhibits.

(d) Exhibits.

Exhibit Number Description 99.1 Press release of Penumbra, Inc. dated February 25, 2026. 104Cover Page Interactive Data File (formatted as Inline Extensible Business Reporting Language).

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

Penumbra, Inc.

Date: February 25, 2026By:/s/ Maggie Yuen Maggie Yuen Chief Financial Officer

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UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d)

of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): January 14, 2026

Penumbra, Inc.

(Exact Name of Registrant as Specified in Its Charter)

Delaware 001-37557 05-0605598

(State or Other Jurisdiction of Incorporation) (Commission File Number) (I.R.S. Employer Identification Number)

One Penumbra Place

Alameda, CA 94502

(Address of Principal Executive Offices)

(510) 748-3200

Registrant’s Telephone Number, Including Area Code

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

☒Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:

Title of each class Trading Symbol(s) Name of each exchange on which registered

Common Stock, Par value $0.001 per share PEN The New York Stock Exchange

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

Emerging growth company ☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Item 1.01.Entry Into a Material Definitive Agreement.

Agreement and Plan of Merger

On January 14, 2026, Penumbra, Inc., a Delaware corporation (the “Company”), entered into an Agreement and Plan of Merger (the “Merger Agreement”) among the Company, Boston Scientific Corporation, a Delaware corporation (“Parent”), and Pinehurst Merger Sub, Inc., a Delaware corporation and a wholly owned subsidiary of Parent (“Merger Sub”), pursuant to which Merger Sub will merge with and into the Company (the “Merger”), with the Company surviving as a wholly owned subsidiary of Parent. Capitalized terms used but not defined herein shall the meanings given to them in the Merger Agreement.

Merger Consideration

Subject to the terms and conditions set forth in the Merger Agreement, at the effective time of the Merger (the “Effective Time”), each share of common stock of the Company, par value $0.001 per share (collectively, the “Common Shares”) outstanding immediately prior to the Effective Time (but excluding Canceled Shares and Dissenting Shares) would be canceled and converted automatically into the right to receive, at the election of the holder thereof in accordance with, and subject to the terms, conditions and procedures set forth in Article II of the Merger Agreement, the following consideration (the “Merger Consideration”), in each case, without interest: (i) for each Common Share with respect to which an election to receive shares of common stock, par value $0.01 per share, of Parent (the “Parent Shares” and such election, a “Stock Election”) has been effectively made and not revoked, 3.8721 fully paid and non-assessable Parent Shares (the “Stock Consideration”); (ii) for each Common Share with respect to which an election to receive cash (a “Cash Election”) has been effectively made and not revoked, $374.00 in cash, without interest (the “Cash Consideration”); and (iii) for each Common Share other than Common Share as to which a Stock Election or a Cash Election has been effectively made and not revoked, the right to receive such Merger Consideration as is determined in accordance with Article II of the Merger Agreement, in each case of (i) through (iii) above, subject to the proration adjustments set forth in Section 2.02 of the Merger Agreement, such that the total number of Common Shares that shall be entitled to receive the Cash Consideration shall be equal to 73.26% of the aggregate number of Common Shares issued and outstanding immediately prior to the Effective Time (other than Cancelled Shares and Dissenting Shares), and the total number of Common Shares that shall be entitled to receive the Stock Consideration shall be equal to 26.74% of the aggregate number of Common Shares issued and outstanding immediately prior to the Effective Time (other than Cancelled Shares and Dissenting S

pen-202511050001321732FALSE00013217322025-11-052025-11-05

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

November 5, 2025 Date of Report (Date of earliest event reported)

Penumbra, Inc. (Exact name of registrant as specified in its charter)

Delaware001-3755705-0605598 (State or other jurisdiction of incorporation or organization)(Commission File No.)(I.R.S. employer identification number)

One Penumbra Place Alameda, CA 94502 (Address of principal executive offices, including zip code)

(510) 748-3200 (Registrant’s telephone number, including area code)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligations of the registrant under any of the following provisions: ☐Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425) ☐Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12) ☐Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b)) ☐Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:

Title of each classTrading SymbolName of each exchange on which registered Common Stock, Par value $0.001 per sharePENThe New York Stock Exchange

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter). Emerging growth company ☐ If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. o

Item 2.02.Results of Operations and Financial Condition.

On November 5, 2025, Penumbra, Inc. issued a press release announcing financial results for the third fiscal quarter ended September 30, 2025. A copy of the press release is furnished as Exhibit 99.1 to this Current Report on Form 8-K and is incorporated herein by reference.

The information furnished on this Current Report on Form 8-K, including the attached exhibit, shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference into any other filing under the Securities Act of 1933, as amended, or the Exchange Act, regardless of any general incorporation language in such a filing, except as expressly set forth by specific reference in such a filing.

Item 9.01.Financial Statements and Exhibits.

(d) Exhibits.

Exhibit Number Description 99.1 Press release of Penumbra, Inc. dated November 5, 2025. 104Cover Page Interactive Data File (formatted as Inline Extensible Business Reporting Language).

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

Penumbra, Inc.

Date: November 5, 2025By:/s/ Maggie Yuen Maggie Yuen Chief Financial Officer