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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. 3)1

 

MEI Pharma, Inc.

 (Name of Issuer)

Common Stock, $0.00000002 par value

 (Title of Class of Securities)

55279B202

 (CUSIP Number)

December 31, 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. 55279B202

 

  1   NAME OF REPORTING PERSON  
         
        Biotechnology Value Fund, L.P.  
  2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a) ☒
        (b) ☐
           
  3   SEC USE ONLY    
           
             
  4   CITIZENSHIP OR PLACE OF ORGANIZATION  
         
        Delaware  
NUMBER OF   5   SOLE VOTING POWER  
SHARES          
BENEFICIALLY         0 shares  
OWNED BY   6   SHARED VOTING POWER  
EACH          
REPORTING         2,869,159 (1)  
PERSON WITH   7   SOLE DISPOSITIVE POWER  
         
          0 shares  
    8   SHARED DISPOSITIVE POWER  
           
          2,869,159 (1)  
  9   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON  
         
        2,869,159 (1)  
  10   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES     ☐
       
           
  11   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)  
         
        2.5% (1)  
  12   TYPE OF REPORTING PERSON  
         
        PN  

  

(1) Includes 742,826 Shares issuable upon the exercise of certain Warrants (as defined below in Item 4).

2

CUSIP No. 55279B202

  1   NAME OF REPORTING PERSON  
         
        BVF I GP LLC  
  2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a) ☒
        (b) ☐
           
  3   SEC USE ONLY    
           
             
  4   CITIZENSHIP OR PLACE OF ORGANIZATION  
         
        Delaware  
NUMBER OF   5   SOLE VOTING POWER  
SHARES          
BENEFICIALLY         0 shares  
OWNED BY   6   SHARED VOTING POWER  
EACH          
REPORTING         2,869,159 (1)  
PERSON WITH   7   SOLE DISPOSITIVE POWER  
         
          0 shares  
    8   SHARED DISPOSITIVE POWER  
           
          2,869,159 (1)  
  9   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON  
         
        2,869,159 (1)  
  10   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES     ☐
       
           
  11   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)  
         
        2.5% (1)  
  12   TYPE OF REPORTING PERSON  
         
        OO  

  

(1) Includes 742,826 Shares issuable upon the exercise of certain Warrants.

3

CUSIP No. 55279B202

 

  1   NAME OF REPORTING PERSON  
         
        Biotechnology Value Fund II, L.P.  
  2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a) ☒
        (b) ☐
           
  3   SEC USE ONLY    
           
             
  4   CITIZENSHIP OR PLACE OF ORGANIZATION  
         
        Delaware  
NUMBER OF   5   SOLE VOTING POWER  
SHARES          
BENEFICIALLY         0 shares  
OWNED BY   6   SHARED VOTING POWER  
EACH          
REPORTING         2,120,911 (1)  
PERSON WITH   7   SOLE DISPOSITIVE POWER  
         
          0 shares  
    8   SHARED DISPOSITIVE POWER  
           
          2,120,911 (1)  
  9   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON  
         
        2,120,911 (1)  
  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% (1)  
  12   TYPE OF REPORTING PERSON  
         
        PN  

  

(1) Includes 520,707 Shares issuable upon the exercise of certain Warrants.

4

CUSIP No. 55279B202

 

  1   NAME OF REPORTING PERSON  
         
        BVF II GP LLC  
  2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a) ☒
        (b) ☐
           
  3   SEC USE ONLY    
           
             
  4   CITIZENSHIP OR PLACE OF ORGANIZATION  
         
        Delaware  
NUMBER OF   5   SOLE VOTING POWER  
SHARES          
BENEFICIALLY         0 shares  
OWNED BY   6   SHARED VOTING POWER  
EACH          
REPORTING         2,120,911 (1)  
PERSON WITH   7   SOLE DISPOSITIVE POWER  
         
          0 shares  
    8   SHARED DISPOSITIVE POWER  
           
          2,120,911 (1)  
  9   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON  
         
        2,120,911 (1)  
  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% (1)  
  12   TYPE OF REPORTING PERSON  
         
        OO  

  

(1) Includes 520,707 Shares issuable upon the exercise of certain Warrants.

5

CUSIP No. 55279B202

 

  1   NAME OF REPORTING PERSON  
         
        Biotechnology Value Trading Fund OS LP  
  2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a) ☒
        (b) ☐
           
  3   SEC USE ONLY    
           
             
  4   CITIZENSHIP OR PLACE OF ORGANIZATION  
         
        Cayman Islands  
NUMBER OF   5   SOLE VOTING POWER  
SHARES          
BENEFICIALLY         0 shares  
OWNED BY   6   SHARED VOTING POWER  
EACH          
REPORTING         391,856 (1)  
PERSON WITH   7   SOLE DISPOSITIVE POWER  
         
          0 shares  
    8   SHARED DISPOSITIVE POWER  
           
          391,856 (1)  
  9   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON  
         
        391,856 (1)  
  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% (1)  
  12   TYPE OF REPORTING PERSON  
         
        PN  

  

(1) Includes 124,074 Shares issuable upon the exercise of certain Warrants.

6

CUSIP No. 55279B202

 

  1   NAME OF REPORTING PERSON  
         
        BVF Partners OS Ltd.  
  2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a) ☒
        (b) ☐
           
  3   SEC USE ONLY    
           
             
  4   CITIZENSHIP OR PLACE OF ORGANIZATION  
         
        Cayman Islands  
NUMBER OF   5   SOLE VOTING POWER  
SHARES          
BENEFICIALLY         0 shares  
OWNED BY   6   SHARED VOTING POWER  
EACH          
REPORTING         391,856 (1)  
PERSON WITH   7   SOLE DISPOSITIVE POWER  
         
          0 shares  
    8   SHARED DISPOSITIVE POWER  
           
          391,856 (1)  
  9   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON  
         
        391,856 (1)  
  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% (1)  
  12   TYPE OF REPORTING PERSON  
         
        CO  

  

(1) Includes 124,074 Shares issuable upon the exercise of certain Warrants.

7

CUSIP No. 55279B202

 

  1   NAME OF REPORTING PERSON  
         
        BVF GP HOLDINGS LLC  
  2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a) ☒
        (b) ☐
           
  3   SEC USE ONLY    
           
             
  4   CITIZENSHIP OR PLACE OF ORGANIZATION  
         
        Delaware  
NUMBER OF   5   SOLE VOTING POWER  
SHARES          
BENEFICIALLY         0 shares  
OWNED BY   6   SHARED VOTING POWER  
EACH          
REPORTING         4,990,070 (1)  
PERSON WITH   7   SOLE DISPOSITIVE POWER  
         
          0 shares  
    8   SHARED DISPOSITIVE POWER  
           
          4,990,070 (1)  
  9   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON  
         
        4,990,070 (1)  
  10   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES     ☐
       
           
  11   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)  
         
        4.4% (1)  
  12   TYPE OF REPORTING PERSON  
         
        OO  

  

(1) Includes 1,263,533 Shares issuable upon the exercise of certain Warrants.

8

CUSIP No. 55279B202

 

  1   NAME OF REPORTING PERSON  
         
        BVF Partners L.P.  
  2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a) ☒
        (b) ☐
           
  3   SEC USE ONLY    
           
             
  4   CITIZENSHIP OR PLACE OF ORGANIZATION  
         
        Delaware  
NUMBER OF   5   SOLE VOTING POWER  
SHARES          
BENEFICIALLY         0 shares  
OWNED BY   6   SHARED VOTING POWER  
EACH          
REPORTING         5,589,315 (1)  
PERSON WITH   7   SOLE DISPOSITIVE POWER  
         
          0 shares  
    8   SHARED DISPOSITIVE POWER  
           
          5,589,315 (1)  
  9   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON  
         
        5,589,315 (1)  
  10   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES     ☐
       
           
  11   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)  
         
        4.9% (1)  
  12   TYPE OF REPORTING PERSON  
         
        PN, IA  

  

(1) Includes 1,540,153 Shares issuable upon the exercise of certain Warrants.

9

CUSIP No. 55279B202

 

  1   NAME OF REPORTING PERSON  
         
        BVF Inc.  
  2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a) ☒
        (b) ☐
           
  3   SEC USE ONLY    
           
             
  4   CITIZENSHIP OR PLACE OF ORGANIZATION  
         
        Delaware  
NUMBER OF   5   SOLE VOTING POWER  
SHARES          
BENEFICIALLY         0 shares  
OWNED BY   6   SHARED VOTING POWER  
EACH          
REPORTING         5,589,315 (1)  
PERSON WITH   7   SOLE DISPOSITIVE POWER  
         
          0 shares  
    8   SHARED DISPOSITIVE POWER  
           
          5,589,315 (1)  
  9   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON  
         
        5,589,315 (1)  
  10   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES     ☐
       
           
  11   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)  
         
        4.9% (1)  
  12   TYPE OF REPORTING PERSON  
         
        CO  

  

(1) Includes 1,540,153 Shares issuable upon the exercise of certain Warrants.

10

CUSIP No. 55279B202

 

  1   NAME OF REPORTING PERSON  
         
        Mark N. Lampert  
  2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a) ☒
        (b) ☐
           
  3   SEC USE ONLY    
           
             
  4   CITIZENSHIP OR PLACE OF ORGANIZATION  
         
        United States  
NUMBER OF   5   SOLE VOTING POWER  
SHARES          
BENEFICIALLY         0 shares  
OWNED BY   6   SHARED VOTING POWER  
EACH          
REPORTING         5,589,315 (1)  
PERSON WITH   7   SOLE DISPOSITIVE POWER  
         
          0 shares  
    8   SHARED DISPOSITIVE POWER  
           
          5,589,315 (1)  
  9   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON  
         
        5,589,315 (1)  
  10   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES     ☐
       
           
  11   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)  
         
        4.9% (1)  
  12   TYPE OF REPORTING PERSON  
         
        IN  

  

(1) Includes 1,540,153 Shares issuable upon the exercise of certain Warrants.

11

CUSIP No. 55279B202

Item 1(a).Name of Issuer:

 

MEI Pharma, Inc., a Delaware corporation (the “Issuer”).

 

Item 1(b).Address of Issuer’s Principal Executive Offices:

 

11455 El Camino Real, Suite 250

San Diego, California 92130

 

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

 

12

CUSIP No. 55279B202

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

 

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, par value $0.00000002 per share (the “Shares”)

 

Item 2(e).CUSIP Number:

 

55279B202

 

13

CUSIP No. 55279B202

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 December 31, 2020, the Reporting Persons held 1,540,153 Warrants exercisable for an aggregate of 1,540,153 Shares (the “Warrants”). The Warrants may not be exercised if, after such exercise, the Reporting Persons would beneficially own, as determined in accordance with Section 13(d) of the Securities Exchange Act of 1934, more than 9.99% of the number of Shares then issued and outstanding (the “Beneficial Ownership Limitation”). Such Warrants have an initial exercise price of $2.54 per share, subject to adjustment pursuant to the terms of the Warrants. As of the close of business on December 31, 2020, the Beneficial Ownership Limitation does not limit the exercise of the Warrants by the Reporting Persons.

 

14

CUSIP No. 55279B202

As of the close of business on December 31, 2020, (i) BVF beneficially owned 2,869,159 Shares, including 742,826 Shares issuable upon the exercise of certain Warrants, (ii) BVF2 beneficially owned 2,120,911 Shares, including 520,707 Shares issuable upon the exercise of certain Warrants and (iii) Trading Fund OS beneficially owned 391,856 Shares, including 124,074 Shares issuable upon the exercise of certain Warrants.

 

BVF GP, as the general partner of BVF, may be deemed to beneficially own the 2,869,159 Shares beneficially owned by BVF.

 

BVF2 GP, as the general partner of BVF2, may be deemed to beneficially own the 2,120,911 Shares beneficially owned by BVF2.

 

Partners OS, as the general partner of Trading Fund OS, may be deemed to beneficially own the 391,856 Shares beneficially owned by Trading Fund OS.

 

BVF GPH, as the sole member of each of BVF GP and BVF2 GP, may be deemed to beneficially own the 4,990,070 Shares beneficially owned in the aggregate by BVF and BVF2.

 

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 5,589,315 Shares beneficially owned in the aggregate by BVF, BVF2, Trading Fund OS, and certain Partners Managed accounts (the “Partners Managed Accounts”), including 207,389 Shares, which includes 152,546 Shares issuable upon the exercise of certain Warrants, held in the Partners Managed Accounts.

 

BVF Inc., as the general partner of Partners, may be deemed to beneficially own the 5,589,315 Shares beneficially owned by Partners.

 

Mr. Lampert, as a director and officer of BVF Inc., may be deemed to beneficially own the 5,589,315 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 Shares owned by another Reporting Person. BVF GP disclaims beneficial ownership of the Shares beneficially owned by BVF. BVF2 GP disclaims beneficial ownership of the Shares beneficially owned by BVF2. Partners OS disclaims beneficial ownership of the Shares beneficially owned by Trading Fund OS. BVF GPH disclaims beneficial ownership of the Shares beneficially owned by BVF and BVF2. Each of Partners, BVF Inc. and Mr. Lampert disclaims beneficial ownership of the Shares beneficially owned by BVF, BVF2, Trading Fund OS, and the Partners Managed Accounts, 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.

 

15

CUSIP No. 55279B202

(b)Percent of class:

 

The following percentages are based on a denominator which is the sum of: (i) 112,521,964 Shares outstanding as of December 16, 2020, which is the total number of Shares outstanding as reported in the Issuer’s Current Report on Form 8-K filed with the Securities and Exchange Commission (the “SEC”) on December 17, 2020 and (ii) certain or all of the 1,540,153 Shares underlying certain Warrants, as applicable.

 

As of the close of business on December 31, 2020, (i) BVF beneficially owned approximately 2.5% of the outstanding Shares, (ii) BVF2 beneficially owned approximately 1.8% of the outstanding Shares, (iii) Trading Fund OS beneficially owned less than 1% of the outstanding Shares, (iv) BVF GP may be deemed to beneficially own approximately 2.5% of the outstanding Shares, (v) BVF2 GP may be deemed to beneficially own approximately 1.8% of the outstanding Shares, (vi) Partners OS may be deemed to beneficially own less than 1% of the outstanding Shares, (vii) BVF GPH may be deemed to beneficially own approximately 4.4% of the outstanding Shares, and (viii) each of Partners, BVF Inc. and Mr. Lampert may be deemed to beneficially own approximately 4.9% of the outstanding Shares (less than 1% of the outstanding Shares are held in the Partners Managed Accounts).

 

(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.

 

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 [X].

 

16

CUSIP No. 55279B202

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 to the Amendment No. 2 to the Schedule 13G filed by the Reporting Persons with the Securities and Exchange Commission on February 14, 2020.

 

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.

 

17

CUSIP No. 55279B202

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: February 11, 2021

 

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 N. 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 N. 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 N. 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      

18