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

Principia Biopharma Inc.

(Name of Issuer)

Common Stock, $0.0001 par value per share

(Title of Class of Securities)

74257L108

(CUSIP Number)

August 17, 2020

(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 disclosures provided in a prior cover page.

The information required on 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. 74257L108

NAME OF REPORTING PERSON

Biotechnology Value Fund, L.P.

CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

(a) ☒

(b) ☐

SEC USE ONLY

CITIZENSHIP OR PLACE OF ORGANIZATION

Delaware

NUMBER OF

SOLE VOTING POWER

BENEFICIALLY

0 shares

OWNED BY

SHARED VOTING POWER

EACH

REPORTING

2,726,500 (1)

PERSON WITH

SOLE DISPOSITIVE POWER

0 shares

SHARED DISPOSITIVE POWER

2,726,500 (1)

AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

2,726,500 (1)

CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES

☐

PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

8.2% (1)

TYPE OF REPORTING PERSON

(1) Represents 2,726,500 Shares (defined in Item 2) underlying certain call options that are currently exercisable.

CUSIP No. 74257L108

NAME OF REPORTING PERSON

BVF I GP LLC

CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

(a) ☒

(b) ☐

SEC USE ONLY

CITIZENSHIP OR PLACE OF ORGANIZATION

Delaware

NUMBER OF

SOLE VOTING POWER

BENEFICIALLY

0 shares

OWNED BY

SHARED VOTING POWER

EACH

REPORTING

2,726,500 (1)

PERSON WITH

SOLE DISPOSITIVE POWER

0 shares

SHARED DISPOSITIVE POWER

2,726,500 (1)

AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

2,726,500 (1)

CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES

☐

PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

8.2% (1)

TYPE OF REPORTING PERSON

(1) Represents 2,726,500 Shares underlying certain call options that are currently exercisable.

CUSIP No. 74257L108

NAME OF REPORTING PERSON

Biotechnology Value Fund II, L.P.

CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

(a) ☒

(b) ☐

SEC USE ONLY

CITIZENSHIP OR PLACE OF ORGANIZATION

Delaware

NUMBER OF

SOLE VOTING POWER

BENEFICIALLY

0 shares

OWNED BY

SHARED VOTING POWER

EACH

REPORTING

2,039,000 (1)

PERSON WITH

SOLE DISPOSITIVE POWER

0 shares

SHARED DISPOSITIVE POWER

2,039,000 (1)

AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

2,039,000 (1)

CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES

☐

PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

6.1% (1)

TYPE OF REPORTING PERSON

(1) Represents 2,039,000 Shares underlying certain call options that are currently exercisable.

CUSIP No. 74257L108

NAME OF REPORTING PERSON

BVF II GP LLC

CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

(a) ☒

(b) ☐

SEC USE ONLY

CITIZENSHIP OR PLACE OF ORGANIZATION

Delaware

NUMBER OF

SOLE VOTING POWER

BENEFICIALLY

0 shares

OWNED BY

SHARED VOTING POWER

EACH

REPORTING

2,039,000 (1)

PERSON WITH

SOLE DISPOSITIVE POWER

0 shares

SHARED DISPOSITIVE POWER

2,039,000 (1)

AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

2,039,000 (1)

CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES

☐

PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

6.1% (1)

TYPE OF REPORTING PERSON

(1) Represents 2,039,000 Shares underlying certain call options that are currently exercisable.

CUSIP No. 74257L108

NAME OF REPORTING PERSON

Biotechnology Value Trading Fund OS LP

CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

(a) ☒

(b) ☐

SEC USE ONLY

CITIZENSHIP OR PLACE OF ORGANIZATION

Cayman Islands

NUMBER OF

SOLE VOTING POWER

BENEFICIALLY

0 shares

OWNED BY

SHARED VOTING POWER

EACH

REPORTING

354,700 (1)

PERSON WITH

SOLE DISPOSITIVE POWER

0 shares

SHARED DISPOSITIVE POWER

354,700 (1)

AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

354,700 (1)

CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES

☐

PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

1.1% (1)

TYPE OF REPORTING PERSON

(1) Represents 354,700 Shares underlying certain call options that are currently exercisable.

CUSIP No. 74257L108

NAME OF REPORTING PERSON

BVF Partners OS Ltd.

CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

(a) ☒

(b) ☐

SEC USE ONLY

CITIZENSHIP OR PLACE OF ORGANIZATION

Cayman Islands

NUMBER OF

SOLE VOTING POWER

BENEFICIALLY

0 shares

OWNED BY

SHARED VOTING POWER

EACH

REPORTING

354,700 (1)

PERSON WITH

SOLE DISPOSITIVE POWER

0 shares

SHARED DISPOSITIVE POWER

354,700 (1)

AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

354,700 (1)

CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES

☐

PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

1.1% (1)

TYPE OF REPORTING PERSON

(1) Represents 354,700 Shares underlying certain call options that are currently exercisable.

CUSIP No. 74257L108

NAME OF REPORTING PERSON

BVF GP HOLDINGS LLC

CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

(a) ☒

(b) ☐

SEC USE ONLY

CITIZENSHIP OR PLACE OF ORGANIZATION

Delaware

NUMBER OF

SOLE VOTING POWER

BENEFICIALLY

0 shares

OWNED BY

SHARED VOTING POWER

EACH

REPORTING

4,765,500 (1)

PERSON WITH

SOLE DISPOSITIVE POWER

0 shares

SHARED DISPOSITIVE POWER

4,765,500 (1)

AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

4,765,500 (1)

CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES

☐

PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

14.3% (1)

TYPE OF REPORTING PERSON

(1) Represents 4,765,500 Shares underlying certain call options that are currently exercisable.

CUSIP No. 74257L108

NAME OF REPORTING PERSON

BVF Partners L.P.

CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

(a) ☒

(b) ☐

SEC USE ONLY

CITIZENSHIP OR PLACE OF ORGANIZATION

Delaware

NUMBER OF

SOLE VOTING POWER

BENEFICIALLY

0 shares

OWNED BY

SHARED VOTING POWER

EACH

REPORTING

5,231,900 (1)

PERSON WITH

SOLE DISPOSITIVE POWER

0 shares

SHARED DISPOSITIVE POWER

5,231,900 (1)

AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

5,231,900 (1)

CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES

☐

PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

15.7% (1)

TYPE OF REPORTING PERSON

PN, IA

(1) Represents 5,231,900 Shares underlying certain call options that are currently exercisable.

CUSIP No. 74257L108

NAME OF REPORTING PERSON

BVF Inc.

CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

(a) ☒

(b) ☐

SEC USE ONLY

CITIZENSHIP OR PLACE OF ORGANIZATION

Delaware

NUMBER OF

SOLE VOTING POWER

BENEFICIALLY

0 shares

OWNED BY

SHARED VOTING POWER

EACH

REPORTING

5,231,900 (1)

PERSON WITH

SOLE DISPOSITIVE POWER

0 shares

SHARED DISPOSITIVE POWER

5,231,900 (1)

AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

5,231,900 (1)

CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES

☐

PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

15.7% (1)

TYPE OF REPORTING PERSON

(1) Represents 5,231,900 Shares underlying certain call options that are currently exercisable.

CUSIP No. 74257L108

NAME OF REPORTING PERSON

Mark N. Lampert

CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

(a) ☒

(b) ☐

SEC USE ONLY

CITIZENSHIP OR PLACE OF ORGANIZATION

United States

NUMBER OF

SOLE VOTING POWER

BENEFICIALLY

0 shares

OWNED BY

SHARED VOTING POWER

EACH

REPORTING

5,231,900 (1)

PERSON WITH

SOLE DISPOSITIVE POWER

0 shares

SHARED DISPOSITIVE POWER

5,231,900 (1)

AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

5,231,900 (1)

CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES

☐

PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

15.7% (1)

TYPE OF REPORTING PERSON

(1) Represents 5,231,900 Shares underlying certain call options that are currently exercisable.

CUSIP No. 74257L108

Item 1(a).

Name of Issuer:

Principia Biopharma Inc., a Delaware corporation (the “Issuer”).

Item 1(b).

Address of Issuer’s Principal Executive Offices:

220 East Grand Avenue

South San Francisco, California 94080

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”)

44 Montgomery St., 40th Floor

San Francisco, California 94104

Citizenship: Delaware

BVF I GP LLC (“BVF GP”)

44 Montgomery St., 40th Floor

San Francisco, California 94104

Citizenship: Delaware

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

44 Montgomery St., 40th Floor

San Francisco, California 94104

Citizenship: Delaware

BVF II GP LLC (“BVF2 GP”)

44 Montgomery St., 40th Floor

San Francisco, California 94104

Citizenship: Delaware

Biotechnology Value Trading Fund OS LP (“Trading Fund OS”)

PO Box 309 Ugland House

Grand Cayman, KY1-1104

Cayman Islands

Citizenship: Cayman Islands

BVF Partners OS Ltd. (“Partners OS”)

PO Box 309 Ugland House

Grand Cayman, KY1-1104

Cayman Islands

Citizenship: Cayman Islands

BVF GP Holdings LLC (“BVF GPH”)

44 Montgomery St., 40th Floor

San Francisco, California 94104

Citizenship: Delaware

BVF Partners L.P. (“Partners”)

44 Montgomery St., 40th Floor

San Francisco, California 94104

Citizenship: Delaware

CUSIP No. 74257L108

BVF Inc.

44 Montgomery St., 40th Floor

San Francisco, California 94104

Citizenship: Delaware

Mark N. Lampert (“Mr. Lampert”)

44 Montgomery St., 40th 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.”

Item 2(d).

Title of Class of Securities:

Common Stock, $0.0001 par value per share (the “Shares”).

Item 2(e).

CUSIP Number:

74257L108

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: ____

CUSIP No. 74257L108

Item 4.

Ownership

(a)

Amount beneficially owned:

The Reporting Persons hold, in the aggregate, 52,319 call options that are currently exercisable, representing 5,231,900 Shares underlying such call options.

As of the close of business on August 18, 2020, (i) BVF beneficially owned 2,726,500 Shares, representing 2,726,500 Shares underlying certain call options currently exercisable, (ii) BVF2 beneficially owned 2,039,000 Shares, representing 2,039,000 Shares underlying certain call options currently exercisable, and (iii) Trading Fund OS beneficially owned 354,700 Shares, representing 354,700 Shares underlying certain call options currently exercisable.

BVF GP, as the general partner of BVF, may be deemed to beneficially own the 2,726,500 Shares beneficially owned by BVF.

BVF2 GP, as the general partner of BVF2, may be deemed to beneficially own 2,039,000 Shares.

Partners OS, as the general partner of Trading Fund OS, may be deemed to beneficially own 354,700 Shares.

BVF GPH, as the sole member of each of BVF GP and BVF2 GP, may be deemed to beneficially own the 4,765,500 Shares beneficially owned by BVF.

Partners, as the investment manager of BVF, BVF2 and Trading Fund OS, and the sole member of Partners OS, may be deemed to beneficially own the 5,231,900 Shares beneficially owned in the aggregate by BVF, BVF2, Trading Fund OS, and a certain Partners managed account (the “Partners Managed Account”), which includes 111,700 Shares underlying certain call options that are currently exercisable that are held in the Partners Managed Account.

BVF Inc., as the general partner of Partners, may be deemed to beneficially own the 5,231,900 Shares beneficially owned by Partners.

Mr. Lampert, as a director and officer of BVF Inc., may be deemed to beneficially own the 5,231,900 Shares 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 securities owned by another Reporting Person. BVF GP disclaims beneficial ownership of the securities beneficially owned by BVF. BVF2 GP disclaims beneficial ownership of the securities beneficially owned by BVF2. Partners OS disclaims beneficial ownership of the securities beneficially owned by Trading Fund OS. BVF GPH disclaims beneficial ownership of the securities beneficially owned by BVF and BVF2. Each of Partners, BVF Inc. and Mr. Lampert disclaims beneficial ownership of the securities beneficially owned by BVF, BVF2, Trading Fund OS, and the Partners Managed Account, 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.

CUSIP No. 74257L108

(b)

Percent of class:

The following percentages are based on 33,236,216 Shares outstanding as of August 16, 2020, as disclosed in Exhibit 2.1 to the Issuer’s Current Report on Form 8-K filed with the Securities and Exchange Commission on August 17, 2020.

As of the close of business on August 18, 2020, (i) BVF beneficially owned approximately 8.2% of the outstanding Shares, (ii) BVF2 beneficially owned approximately 6.1% of the outstanding Shares, (iii) Trading Fund OS beneficially owned approximately 1.1% of the outstanding Shares, (iv) BVF GP may be deemed to beneficially own approximately 8.2% of the outstanding Shares, (v) BVF2 GP may be deemed to beneficially own approximately 6.1% of the outstanding Shares, (vi) Partners OS may be deemed to beneficially own approximately 1.1% of the outstanding Shares, (vii) BVF GPH may be deemed to beneficially own approximately 14.3% of the outstanding Shares and (viii) each of Partners, BVF Inc. and Mr. Lampert may be deemed to beneficially own approximately 15.7% of the outstanding Shares (call options representing less than 1% of the outstanding Shares are held in the Partners Managed Account).

(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.

Item 5.

Ownership of Five Percent or Less of a Class.

Not Applicable.

Item 6.

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

BVF GP, BVF GPH, Partners, BVF Inc. and Mr. Lampert share voting and dispositive power over the securities beneficially owned by BVF. BVF2 GP, BVF GPH, Partners, BVF Inc. and Mr. Lampert share voting and dispositive power over the securities beneficially owned by BVF2. Partners, BVF Inc. and Mr. Lampert share voting and dispositive power over the securities beneficially owned by Trading Fund OS and the Partners Managed Accounts.

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.

CUSIP No. 74257L108

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. 74257L108

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: August 19, 2020

BIOTECHNOLOGY VALUE FUND, L.P.		BIOTECHNOLOGY VALUE TRADING FUND OS LP

By:	BVF I GP LLC., its general partner	By:	BVF Partners L.P., its investment manager
		By:	BVF Inc., its general partner
By:	/s/ Mark N. Lampert
	Mark N. Lampert	By:	/s/ Mark N. Lampert
	Chief Executive Officer		Mark Lampert
			President

BVF I GP LLC
		BVF GP HOLDINGS LLC
By:	/s/ Mark N. Lampert
	Mark N. Lampert	By:	/s/ Mark N. Lampert
	Chief Executive Officer		Mark Lampert
			Chief Executive Officer

BIOTECHNOLOGY VALUE FUND II, L.P.
		BVF PARTNERS L.P.
By:	BVF II GP LLC, its general partner
		By:	BVF Inc., its general partner
By:	/s/ Mark N. Lampert
	Mark N. Lampert	By:	/s/ Mark N. Lampert
	Chief Executive Officer		Mark N. Lampert
			President

BVF II GP LLC
		BVF INC.
By:	/s/ Mark N. Lampert
	Mark N. Lampert	By:	/s/ Mark N. Lampert
	Chief Executive Officer		Mark Lampert
			President

BVF PARTNERS OS LTD.
		/s/ Mark N. Lampert
By:	BVF Partners L.P., its sole member	MARK N. LAMPERT
By:	BVF Inc., its general partner

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

Principia Biopharma Inc. SC 13G