Biotechnology Value Fund L P SC 13G Blueprint Medicines Corp

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13G

(Rule 13d-102)

INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT

TO RULES 13d-1(b), (c), AND (d) AND AMENDMENTS THERETO FILED

PURSUANT TO RULE 13d-2(b)

(Amendment No. )1

Blueprint Medicines Corporation

(Name of Issuer)

Common Stock, $0.001 par value

(Title of Class of Securities)

09627Y109

(CUSIP Number)

April 30, 2015

(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)

_______________

1 The remainder of this cover page shall be filled out for a reporting person’s initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter the disclosures provided in a prior cover page.

The information required in the remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934 (“Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

CUSIP NO. 09627Y109

1	NAME OF REPORTING PERSON Biotechnology Value Fund, L.P.
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP		(a) x (b) o
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 shares
	6	SHARED VOTING POWER 870,111
	7	SOLE DISPOSITIVE POWER 0 shares
	8	SHARED DISPOSITIVE POWER 870,111
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 870,111
10	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES		¨
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 3.4%
12	TYPE OF REPORTING PERSON PN

CUSIP NO. 09627Y109

1	NAME OF REPORTING PERSON Biotechnology Value Fund II, L.P.
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP		(a) x (b) o
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 shares
	6	SHARED VOTING POWER 486,809
	7	SOLE DISPOSITIVE POWER 0 shares
	8	SHARED DISPOSITIVE POWER 486,809
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 486,809
10	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES		¨
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 1.9%
12	TYPE OF REPORTING PERSON PN

CUSIP NO. 09627Y109

1	NAME OF REPORTING PERSON Investment 10, L.L.C.
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP		(a) x (b) o
3	SEC USE ONLY
4	CITIZENSHIP OR PLACE OF ORGANIZATION Illinois
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH	5	SOLE VOTING POWER 0 shares
	6	SHARED VOTING POWER 215,872
	7	SOLE DISPOSITIVE POWER 0 shares
	8	SHARED DISPOSITIVE POWER 215,872
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 215,872
10	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES		¨
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) Less than 1%
12	TYPE OF REPORTING PERSON OO

CUSIP NO. 09627Y109

1	NAME OF REPORTING PERSON MSI BVF SPV, LLC
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP		(a) x (b) o
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 shares
	6	SHARED VOTING POWER 122,616
	7	SOLE DISPOSITIVE POWER 0 shares
	8	SHARED DISPOSITIVE POWER 122,616
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 122,616
10	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES		¨
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) Less than 1%
12	TYPE OF REPORTING PERSON OO

CUSIP NO. 09627Y109

1	NAME OF REPORTING PERSON BVF Partners L.P.
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP		(a) x (b) o
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 shares
	6	SHARED VOTING POWER 1,695,408
	7	SOLE DISPOSITIVE POWER 0 shares
	8	SHARED DISPOSITIVE POWER 1,695,408
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 1,695,408
10	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES		¨
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 6.6%
12	TYPE OF REPORTING PERSON PN, IA

CUSIP NO. 09627Y109

1	NAME OF REPORTING PERSON BVF Inc.
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP		(a) x (b) o
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 shares
	6	SHARED VOTING POWER 1,695,408
	7	SOLE DISPOSITIVE POWER 0 shares
	8	SHARED DISPOSITIVE POWER 1,695,408
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 1,695,408
10	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES		¨
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 6.6%
12	TYPE OF REPORTING PERSON CO

CUSIP NO. 09627Y109

1	NAME OF REPORTING PERSON Mark N. Lampert
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP		(a) x (b) o
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 shares
	6	SHARED VOTING POWER 1,695,408
	7	SOLE DISPOSITIVE POWER 0 shares
	8	SHARED DISPOSITIVE POWER 1,695,408
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 1,695,408
10	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES		¨
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 6.6%
12	TYPE OF REPORTING PERSON IN

CUSIP NO. 09627Y109

Item 1(a).

Name of Issuer:

Blueprint Medicines Corporation, a Delaware corporation (the “Issuer”).

Item 1(b).

Address of Issuer’s Principal Executive Offices:

215 First Street

Cambridge, Massachusetts 02142

Item 2(a).

Name of Person Filing

Item 2(b).

Address of Principal Business Office or, if None, Residence

Item 2(c).

Citizenship

Biotechnology Value Fund, L.P. (“BVF”)

1 Sansome Street, 30th Floor

San Francisco, California 94104

Citizenship: Delaware

Biotechnology Value Fund II, L.P. (“BVF2”)

1 Sansome Street, 30th Floor

San Francisco, California 94104

Citizenship: Delaware

Investment 10, L.L.C. (“ILL10”)

900 North Michigan Avenue, Suite 1100

Chicago, Illinois 60611

Citizenship: Illinois

MSI BVF SPV, LLC (“MSI”)

c/o Magnitude Capital, LLC

601 Lexington Avenue, 59th Floor

New York, NY 10022

Citizenship: Delaware

BVF Partners L.P. (“Partners”)

1 Sansome Street, 30th Floor

San Francisco, California 94104

Citizenship: Delaware

BVF Inc.

1 Sansome Street, 30th Floor

San Francisco, California 94104

Citizenship: Delaware

Mark N. Lampert (“Mr. Lampert”)

1 Sansome Street, 30th Floor

San Francisco, California 94104

Citizenship: United States

Each of the foregoing is referred to as a “Reporting Person” and collectively as the “Reporting Persons.”

CUSIP NO. 09627Y109

Item 2(d).

Title of Class of Securities:

Common stock, $0.001 par value (the “Common Stock”)

Item 2(e).

CUSIP Number:

09627Y109

Item 3.

If This Statement is Filed Pursuant to Rule 13d-1(b), or 13d-2(b) or (c), Check Whether the Person Filing is a:

/x/

Not applicable.

(a)

/ /

Broker or dealer registered under Section 15 of the Exchange Act.

(b)

/ /

Bank as defined in Section 3(a)(6) of the Exchange Act.

(c)

/ /

Insurance company as defined in Section 3(a)(19) of the Exchange Act.

(d)

/ /

Investment company registered under Section 8 of the Investment Company Act.

(e)

/ /

An investment adviser in accordance with Rule 13d-1(b)(1)(ii)(E).

(f)

/ /

An employee benefit plan or endowment fund in accordance with Rule 13d-1(b)(1)(ii)(F).

(g)

/ /

A parent holding company or control person in accordance with Rule 13d-1(b)(1)(ii)(G).

(h)

/ /

A savings association as defined in Section 3(b) of the Federal Deposit Insurance Act.

(i)

/ /

A church plan that is excluded from the definition of an investment company under Section 3(c)(14) of the Investment Company Act.

(j)

/ /

Group, in accordance with Rule 13d-1(b)(1)(ii)(J).

(k)

/ /

Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K). If filing as a non-U.S. institution in accordance with Rule 240.13d-1(b)(1)(ii)(J), please specify the type of institution: ____

Item 4.

Ownership

(a)

Amount beneficially owned:

As of the close of business on May 8, 2015 (i) BVF beneficially owned 870,111 shares of Common Stock, (ii) BVF2 beneficially owned 486,809 shares of Common Stock, (iii) ILL10 beneficially owned 215,872 shares of Common Stock, and (iv) MSI beneficially owned 122,616 shares of Common Stock.

CUSIP NO. 09627Y109

Partners, as the general partner of BVF and BVF2 and the investment adviser of ILL10 and MSI may be deemed to beneficially own 1,695,408 shares of Common Stock beneficially owned in the aggregate by BVF, BVF2, ILL10 and MSI.

BVF Inc., as the general partner of Partners, may be deemed to beneficially own the 1,695,408 shares of Common Stock beneficially owned by Partners.

Mr. Lampert, as a director and officer of BVF Inc., may be deemed to beneficially own the 1,695,408 shares of Common Stock beneficially owned by BVF Inc.

The foregoing should not be construed in and of itself as an admission by any Reporting Person as to beneficial ownership of any shares of Common Stock owned by another Reporting Person. Each of Partners, BVF Inc. and Mr. Lampert disclaims beneficial ownership of the shares of Common Stock beneficially owned by BVF, BVF2, ILL10 and MSI and the filing of this statement shall not be construed as an admission that any such person or entity is the beneficial owner of any such securities.

(b)

Percent of class:

The following percentages are based on 25,831,965 shares of Common Stock outstanding, as disclosed in the Issuer’s Prospectus filed on Form 424B4 with the Securities and Exchange Commission on April 30, 2015.

As of the close of business on May 8, 2015, (i) BVF beneficially owned approximately 3.4% of the outstanding shares of Common Stock, (ii) BVF2 beneficially owned approximately 1.9% of the outstanding shares of Common Stock, (iii) ILL10 beneficially owned less than 1% of the outstanding shares of Common Stock, (iv) MSI beneficially owned less than 1% of the outstanding shares of Common Stock and (v) each of Partners, BVF Inc. and Mr. Lampert may be deemed to beneficially own approximately 6.6% of the outstanding shares of Common Stock.

(c)

Number of shares as to which such person has:

(i)

Sole power to vote or to direct the vote

See Cover Pages Items 5-9.

(ii)

Shared power to vote or to direct the vote

See Cover Pages Items 5-9.

(iii)

Sole power to dispose or to direct the disposition of

See Cover Pages Items 5-9.

(iv)

Shared power to dispose or to direct the disposition of

See Cover Pages Items 5-9.

CUSIP NO. 09627Y109

Item 5.

Ownership of Five Percent or Less of a Class.

If this statement is being filed to report the fact that as of the date hereof the reporting person has ceased to be the beneficial owner of more than five percent of the class of securities, check the following [ ].

Item 6.

Ownership of More than Five Percent on Behalf of Another Person.

Not Applicable.

Item 7.

Identification and Classification of the Subsidiary That 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.

See Exhibit 99.1.

Item 9.

Notice of Dissolution of Group.

Not Applicable.

Item 10.

Certifications.

By signing below each of the undersigned certifies that, to the best of its knowledge and belief, the securities referred to above 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.

CUSIP NO. 09627Y109

SIGNATURE

After reasonable inquiry and to the best of his knowledge and belief, each of the undersigned certifies that the information set forth in this statement is true, complete and correct.

Dated: May 8, 2015

BIOTECHNOLOGY VALUE FUND, L.P.		INVESTMENT 10, L.L.C.

By:	BVF Partners L.P., its general partner	By:	BVF Partners L.P., its investment adviser
By:	BVF Inc., its general partner	By:	BVF Inc., its general partner

By:	/s/ Mark N. Lampert	By:	/s/ Mark N. Lampert
	Mark N. Lampert		Mark N. Lampert
	President		President


BIOTECHNOLOGY VALUE FUND II, L.P.		MSI BVF SPV, LLC

By:	BVF Partners L.P., its general partner	By:	BVF Partners L.P., its investment adviser
By:	BVF Inc., its general partner	By:	BVF Inc., its general partner

By:	/s/ Mark N. Lampert	By:	/s/ Mark N. Lampert
	Mark N. Lampert		Mark N. Lampert
	President		President

		BVF INC.

BVF PARTNERS L.P.		By:	/s/ Mark N. Lampert
			Mark N. Lampert
By:	BVF Inc., its general partner		President

By:	/s/ Mark N. Lampert
	Mark N. Lampert		/s/ Mark N. Lampert
	President		MARK N. LAMPERT

Biotechnology Value Fund L P SC 13GBlueprint Medicines Corp