Pentwater Reports 6.0% Stake in Blueprint Medicines (3.9M Shares)

Pentwater Capital Management LP and Matthew Halbower report beneficial ownership of 3,900,000 shares of Blueprint Medicines Corp common stock, representing 6.0% of the outstanding class based on 64,733,629 shares outstanding.

Rhea-AI Filing Summary

Pentwater Capital Management LP and Matthew Halbower report beneficial ownership of 3,900,000 shares of Blueprint Medicines Corp common stock, representing 6.0% of the outstanding class based on 64,733,629 shares outstanding. The filing states the shares are directly held by the Pentwater Funds and that voting and dispositive power over these shares is shared (no sole voting or dispositive power reported). The Investment Manager is organized in Delaware and Mr. Halbower is a U.S. citizen; the business office for the reporting persons is 1001 10th Avenue South, Suite 216, Naples, FL. The statement certifies the holdings were acquired and are held in the ordinary course of business and not for the purpose of changing control.

Positive

• Clear disclosure of a >5% stake (3,900,000 shares, 6.0%), meeting SEC reporting requirements
• Shared voting and dispositive power indicates holdings are managed at the fund level rather than concentrated in a single individual's sole authority
• Certification that holdings are in the ordinary course of business and not held to change control

Negative

• Concentrated ownership (6.0%) could influence shareholder dynamics and trading liquidity
• Limited detail on the identity and number of the specific Pentwater Funds holding the shares, reducing transparency about the ultimate investors' objectives

Insights

Securities Analyst

TL;DR: A 6% stake by an activist-capable investment manager is material and could influence shareholder dynamics even if disclosed as non-control.

Pentwater's 6.0% position in Blueprint Medicines is above the 5% reporting threshold and material to investors because it signals concentrated ownership that may affect trading liquidity and governance discussions. The filing reports shared voting and dispositive power rather than sole control, and the shares are held by managed funds rather than the manager personally. The statement's certification that the position is held in the ordinary course reduces, but does not eliminate, the potential for engagement with management or proxy activity. Investors should note the exact share count of 3,900,000 and the outstanding share base used for the calculation (64,733,629).

Corporate Governance Expert

TL;DR: Ownership structure shows fund-level holdings with shared authority; this is an important disclosure for governance monitoring.

The report clarifies that voting and disposition are exercised jointly, which is typical for fund holdings managed by an adviser. Classification codes (IA, PN for the manager; HC, IN for Mr. Halbower) indicate an investment adviser and related individual reporting. The explicit certification that the stake is not intended to change control is standard but not definitive; the presence of a >5% holder warrants attention from the company's board and governance committees regarding outreach, potential proposals, or strategic dialogue.

FAQ

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

How many Blueprint Medicines (BPMC) shares does Pentwater report owning?

The filing reports 3,900,000 shares beneficially owned, representing 6.0% of the class.

Does Pentwater have sole voting control over the BPMC shares?

No. The filing shows 0 sole voting power and 3,900,000 shares of shared voting power.

On what share count is the 6.0% ownership based?

The percentage is calculated using an outstanding share base of 64,733,629 shares as reported by the issuer.

Who are the reporting persons on the Schedule 13G for BPMC?

The reporting persons are Pentwater Capital Management LP (the Investment Manager) and Matthew Halbower (related individual).

Is the Pentwater position reported as intended to change control of Blueprint Medicines?

The filing includes a certification that the securities were acquired and are held in the ordinary course of business and not for the purpose of changing control of the issuer.

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

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Accepted by SEC EDGAR 08/14/2025 - 04:10 PM Learn about SEC filing dates

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

Blueprint Medicines Corp

(Name of Issuer)

Common Stock, par value $0.001 per share

(Title of Class of Securities)

09627Y109

(CUSIP Number)

06/30/2025

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

Rule 13d-1(b)

Rule 13d-1(c)

Rule 13d-1(d)

SCHEDULE 13G

CUSIP No. 09627Y109

1

Names of Reporting Persons

Pentwater Capital Management LP

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 3,900,000.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 3,900,000.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

3,900,000.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

6.0 %

12

Type of Reporting Person (See Instructions)

IA, PN

SCHEDULE 13G

CUSIP No. 09627Y109

1

Names of Reporting Persons

Matthew Halbower

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

UNITED STATES

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 3,900,000.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 3,900,000.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

3,900,000.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

6.0 %

12

Type of Reporting Person (See Instructions)

HC, IN

SCHEDULE 13G

Item 1.
(a)	Name of issuer: Blueprint Medicines Corp
(b)	Address of issuer's principal executive offices: 45 Sidney Street Cambridge, MA 02139
Item 2.
(a)	Name of person filing: This statement is filed by: (i) Pentwater Capital Management LP (the "Investment Manager"), a Delaware limited partnership, and the investment adviser to certain funds (the "Pentwater Funds"), with respect to the shares of common stock, par value $0.001 per share ("Common Stock") of Blueprint Medicines Corp., a Delaware corporation (the "Company") directly held by the Pentwater Funds; and (ii) Mr. Matthew Halbower ("Mr. Halbower"), the sole shareholder of MCH PWCM Holdings Inc., the general partner of the Investment Manager, with respect to the shares of Common Stock directly held by the Pentwater Funds. The foregoing persons are hereinafter sometimes collectively referred to as the "Reporting Persons." The filing of this statement should not be construed as an admission that any of the foregoing persons or any Reporting Person is, for the purposes of Section 13 of the Securities and Exchange Act of 1934, the beneficial owner of the securities reported herein.
(b)	Address or principal business office or, if none, residence: The address of the business office of each of the Reporting Persons is 1001 10th Avenue South, Suite 216, Naples, FL 34102.
(c)	Citizenship: The Investment Manager is a Delaware limited partnership. Mr. Halbower is a citizen of the United States.
(d)	Title of class of securities: Common Stock, par value $0.001 per share
(e)	CUSIP No.: 09627Y109
Item 3.	If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:
(a)	Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);
(b)	Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);
(c)	Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);
(d)	Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
(e)	An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);
(f)	An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);
(g)	A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
(h)	A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
(i)	A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);
(j)	A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J). If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J), please specify the type of institution:
(k)	Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).
Item 4.	Ownership
(a)	Amount beneficially owned: The information required by Item 4(a) is set forth in Row 9 of the cover page for each of the Reporting Persons and is incorporated herein by reference. The percentage set forth in this Schedule 13G is calculated based upon an aggregate of 64,733,629 shares of Common Stock outstanding as of June 12, 2025, as reported in the Issuer's Solicitation Statement on Schedule 14D-9, filed with the Securities and Exchange Commission on June 17, 2025.
(b)	Percent of class: 6.0%
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: The information required by Item 4(c)(i) is set forth in Row 5 of the cover page for each of the Reporting Persons and is incorporated herein by reference.
	(ii) Shared power to vote or to direct the vote: The information required by Item 4(c)(ii) is set forth in Row 6 of the cover page for each of the Reporting Persons and is incorporated herein by reference.
	(iii) Sole power to dispose or to direct the disposition of: The information required by Item 4(c)(iii) is set forth in Row 7 of the cover page for each of the Reporting Persons and is incorporated herein by reference.
	(iv) Shared power to dispose or to direct the disposition of: The information required by Item 4(c)(iv) is set forth in Row 8 of the cover page for each of the Reporting Persons and is incorporated herein by reference.
Item 5.	Ownership of 5 Percent or Less of a Class.
Item 6.	Ownership of more than 5 Percent on Behalf of Another Person.
	If any other person is known to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, such securities, a statement to that effect should be included in response to this item and, if such interest relates to more than 5 percent of the class, such person should be identified. A listing of the shareholders of an investment company registered under the Investment Company Act of 1940 or the beneficiaries of employee benefit plan, pension fund or endowment fund is not required. See Item 2(a). The Pentwater Funds have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, the shares of Common Stock reported herein.
Item 7.	Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
	Not Applicable
Item 8.	Identification and Classification of Members of the Group.
	Not Applicable
Item 9.	Notice of Dissolution of Group.
	Not Applicable

Item 10.

Certifications:

By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under ?? 240.14a-11.

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Pentwater Capital Management LP

Signature:	/s/ Matthew Halbower
Name/Title:	By: MCH PWCM Holdings Inc., General Partner, By: Matthew Halbower, Chief Executive Officer
Date:	08/14/2025

Matthew Halbower

Signature:	/s/ Matthew Halbower
Name/Title:	Matthew Halbower, Individually
Date:	08/14/2025