UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
 

Schedule 13G

 

Under the Securities Exchange Act of 1934

 

(Amendment No. __)*

 

Mast Therapeutics, Inc.
(Name of Issuer)

 

Common Stock
(Title of Class of Securities)

 

576314108
(CUSIP Number)
 
June 14, 2013
(Date of Event which Requires Filing of this Statement)

 

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

 

oRule 13d-1(b)

 

xRule 13d-1(c)

 

oRule 13d-1(d)

 

*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).

 

Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB control number.

1
CUSIP No.  576314108 13G Page 2 of 10 Pages
 
1.

NAMES OF REPORTING PERSONS

 

Great Point Partners, LLC

 

I.R.S. IDENTIFICATION NO. OF ABOVE PERSON (ENTITIES ONLY):

 

37-1475292

 

2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
  (a)

£

 

  (b) £

 

3. SEC USE ONLY
   
   
4. CITIZENSHIP OR PLACE OF ORGANIZATION

USA
   
NUMBER OF SHARES

BENEFICIALLY

OWNED BY EACH

REPORTING PERSON

WITH
5.

SOLE VOTING POWER

 

0

 

6.

SHARED VOTING POWER

 

8,700,0001

 

7.

SOLE DISPOSITIVE POWER

 

0

 

8.

SHARED DISPOSITIVE POWER

 

8,700,0001

 

9.

AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

 

8,700,0001

 

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)

 

8.77%1, 2

 

12.

TYPE OF REPORTING PERSON (See Instructions)

 

IA

 

 

 

1Includes 2,900,000 shares of Common Stock issuable upon exercise of warrants owned by Biomedical Value Fund, LP, Biomedical Offshore Value Fund, Ltd., Biomedical Institutional Value Fund, LP, Class D Series of GEF-PS, LP, David J. Morrison, and WS Investments III, LLC.

 

2Based on a total of 96,265,286 shares of Common Stock outstanding, as reported by the Issuer on a prospectus supplement filed with the SEC on June 17, 2013.

 
CUSIP No.  576314108 13G Page 3 of 10 Pages
 
1.

NAMES OF REPORTING PERSONS

 

Dr. Jeffrey R. Jay, M.D.

 

I.R.S. IDENTIFICATION NO. OF ABOVE PERSON (ENTITIES ONLY):

 

2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
  (a)

£

 

  (b) £

 

3. SEC USE ONLY
   
   
4. CITIZENSHIP OR PLACE OF ORGANIZATION

USA

NUMBER OF SHARES

BENEFICIALLY

OWNED BY EACH

REPORTING PERSON

WITH
5.

SOLE VOTING POWER

 

01

 

6.

SHARED VOTING POWER

 

8,700,0001

 

7.

SOLE DISPOSITIVE POWER

 

01

 

8.

SHARED DISPOSITIVE POWER

 

8,700,0001

 

9.

AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

 

8,700,0001

 

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)

 

8.77%1, 2

 

12.

TYPE OF REPORTING PERSON (See Instructions)

 

IN

 
CUSIP No.  576314108 13G Page 4 of 10 Pages
 
1.

NAMES OF REPORTING PERSONS

 

Mr. David Kroin

 

I.R.S. IDENTIFICATION NO. OF ABOVE PERSON (ENTITIES ONLY):

 

2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
  (a)

£

 

  (b) £

 

3. SEC USE ONLY
   
   
4. CITIZENSHIP OR PLACE OF ORGANIZATION

USA

NUMBER OF SHARES

BENEFICIALLY

OWNED BY EACH

REPORTING PERSON

WITH
5.

SOLE VOTING POWER

 

0

 

6.

SHARED VOTING POWER

 

8,700,0001

 

7.

SOLE DISPOSITIVE POWER

 

0

 

8.

SHARED DISPOSITIVE POWER

 

8,700,0001

 

9.

AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

 

8,700,0001

 

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)

 

8.77%1,2

 

12.

TYPE OF REPORTING PERSON (See Instructions)

 

IN

 
CUSIP No.  576314108 13G Page 5 of 10 Pages
 

Item 1.

 

  (a) Name of Issuer
     
    Mast Therapeutics, Inc.
     
  (b) Address of Issuer’s Principal Executive Offices
     
    12390 El Camino Real, Suite 150, San Diego, CA 92130

 

Item 2.

 

  (a) Name of Person Filing
       
      Great Point Partners, LLC
      Dr. Jeffrey R. Jay, M.D.
      Mr. David Kroin
       
  The Reporting Persons have entered into a Joint Filing Agreement, dated June 24, 2013, a copy of which is filed with this Schedule 13G as Exhibit A, pursuant to which the Reporting Persons have agreed to file this statement jointly in accordance with the provisions of Rule 13d-1(k)(1) under the Act.
       
  (b) Address of Principal Business Office, or if none, Residence
       
    The address of the principal business office of each of the Reporting Persons is
       
      165 Mason Street, 3rd Floor
      Greenwich, CT 06830
       
  (c) Citizenship
       
  Great Point Partners, LLC is a limited liability company organized under the laws of the State of Delaware.  Dr. Jeffrey R. Jay, M.D. is a citizen of the United States. Mr. David Kroin is a citizen of the United States.
       
  (d) Title of Class of Securities
       
    Common Stock
       
  (e) CUSIP Number
       
    576314108

 

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:
       
    Not Applicable.
       
  (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).
 
CUSIP No.  576314108 13G Page 6 of 10 Pages
 
  (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) £ Group, in accordance with §240.13d-1(b)(1)(ii)(J).

 

Item 4. Ownership
   
  Biomedical Value Fund, L.P. (“BVF”) is the record owner of 2,227,496 shares of Common Stock (the “BVF Shares”).  Great Point Partners, LLC (“Great Point”) is the investment manager of BVF, and by virtue of such status may be deemed to be the beneficial owner of the BVF Shares.  Each of Dr. Jeffrey R. Jay, M.D. (“Dr. Jay”), as senior managing member of Great Point, and Mr. David Kroin (“Mr. Kroin”), as special managing member of Great Point, has voting and investment power with respect to the BVF Shares, and therefore may be deemed to be the beneficial owner of the BVF Shares.  In addition, BVF is the record owner of warrants to purchase 1,113,748 shares of Common Stock.
   
  Biomedical Offshore Value Fund, Ltd. (“BOVF”) is the record owner of 1,370,949 shares of Common Stock (the “BOVF Shares”).  Great Point is the investment manager of BOVF, and by virtue of such status may be deemed to be the beneficial owner of the BOVF Shares.  Each of Dr. Jay, as senior managing member of Great Point, and Mr. Kroin, as special managing member of Great Point, has voting and investment power with respect to the BOVF Shares, and therefore may be deemed to be the beneficial owner of the BOVF Shares.  In addition, BOVF is the record owner of warrants to purchase 685,475 shares of Common Stock.
   
  Biomedical Institutional Value Fund, L.P. (“BIVF”) is the record owner 806,442 shares of Common Stock (the “BIVF Shares”).  Great Point is the investment manager of BIVF, and by virtue of such status may be deemed to be the beneficial owner of the BIVF Shares.  Each of Dr. Jay, as senior managing member of Great Point, and Mr. Kroin, as special managing member of Great Point, has voting and investment power with respect to the BIVF Shares, and therefore may be deemed to be the beneficial owner of the BIVF Shares.  In addition, BIVF is the record owner of warrants to purchase 403,221 shares of Common Stock.
   
  Class D Series of GEF-PS, LP (“GEF-PS”) is the record owner of 1,143,536 shares of Common Stock (the “GEF-PS Shares”).  Great Point is the investment manager of GEF-PS, and by virtue of such status may be deemed to be the beneficial owner of the GEF-PS Shares.  Each of Dr. Jay, as senior managing member of Great Point, and Mr. Kroin, as special managing member of Great Point, has voting and investment power with respect to the GEF-PS Shares, and therefore may be deemed to be the beneficial owner of the GEF-PS Shares.  In addition, GEF-PS is the record owner of warrants to purchase 571,768 shares of Common Stock.
   
  WS Investments III, LLC (“WS”) is the record owner of 205,836 shares of Common Stock (the “WS Shares”).  Great Point is the investment manager with respect to the WS Shares, and by virtue of such status may be deemed to be the beneficial owner of the WS Shares.  Each of Dr. Jay, as senior managing member of Great Point, and Mr. Kroin, as special managing member of Great Point, has voting and investment power with respect to the WS Shares, and therefore may be deemed to be the beneficial owner of the WS Shares.  In addition, WS is is the record owner of warrants to purchase 102,918 of Common Stock.
 
CUSIP No.  576314108 13G Page 7 of 10 Pages
 
  David J. Morrison (“Morrison”) is the record owner of 45,741 shares of Common Stock (the “Morrison Shares”).  Great Point is the investment manager with respect to the Morrison Shares, and by virtue of such status may be deemed to be the beneficial owner of the Morrison Shares.  Each of Dr. Jay, as senior managing member of Great Point, and Mr. Kroin, as special managing member of Great Point, has voting and investment power with respect to the Morrison Shares, and therefore may be deemed to be the beneficial owner of the Morrison Shares.  In addition, Morrison is the record owner of warrants to purchase 22,871 shares of Common Stock.
   
  Notwithstanding the above, Great Point, Dr. Jay and Mr. Kroin disclaim beneficial ownership of the BVF Shares, the BOVF Shares, the BIVF Shares, the GEF-PS Shares, the Morrison Shares, the WS Shares, and the shares of Common Stock underlying warrants described above, except to the extent of their respective pecuniary interests.
   
  Provide the following information regarding the aggregate number and percentage of the class of securities of the issuer identified in Item 1.

 

  1. Great Point Partners, LLC
       
  (a) Amount beneficially owned:  8,700,0003
       
  (b) Percent of class:  8.77%3, 4
       
  (c) Number of shares as to which the person has:
       
    (i) Sole power to vote or to direct the vote:  - 0 -
       
    (ii) Shared power to vote or to direct the vote:  8,700,0003
       
    (iii) Sole power to dispose or to direct the disposition of: - 0 -.
       
    (iv) Shared power to dispose or to direct the disposition of:  8,700,0003

 

  2. Dr. Jeffrey R. Jay, M.D.
       
  (a) Amount beneficially owned:  8,700,0003
       
  (b) Percent of class:  8.77%3,4
       
  (c) Number of shares as to which the person has:
       
    (i) Sole power to vote or to direct the vote:  0.
       
    (ii) Shared power to vote or to direct the vote: 8,700,0003
       
    (iii) Sole power to dispose or to direct the disposition of:  0.
       
    (iv) Shared power to dispose or to direct the disposition of:  8,700,0003

 

 
3Includes 2,900,000 shares of Common Stock issuable upon exercise of warrants owned by Biomedical Value Fund, LP, Biomedical Offshore Value Fund, Ltd., Biomedical Institutional Value Fund, LP, Class D Series of GEF-PS, LP, David J. Morrison, and WS Investments III, LLC.

 

4Based on a total of 96,265,286 shares of Common Stock outstanding, as reported by the Issuer on a prospectus supplement filed with the SEC on June 17, 2013.
 
CUSIP No.  576314108 13G Page 8 of 10 Pages
 
  3. Mr. David Kroin
       
  (a) Amount beneficially owned:  8,700,0003
       
  (b) Percent of class:  8.77%3,4
       
  (c) Number of shares as to which the person has:
       
    (i) Sole power to vote or to direct the vote:  0.
       
    (ii) Shared power to vote or to direct the vote:  8,700,0003
       
    (iii) Sole power to dispose or to direct the disposition of:  0.
       
    (iv) Shared power to dispose or to direct the disposition of:  8,700,0003

 

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 each of the Reporting Persons 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:
   
  See Item 4.
   
Item 7. Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company
   
  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. Certification

 

By signing below I certify that, to the best of my 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 participant in any transaction having that purpose or effect.

 
CUSIP No.  576314108 13G Page 9 of 10 Pages
 

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.

 

Date: June 24, 2013

 

  GREAT POINT PARTNERS, LLC  
       
  By: /s/ Dr. Jeffrey R. Jay, M.D.  
    Dr. Jeffrey R. Jay, M.D.,  
    as senior managing member  
       
  /s/ Dr. Jeffrey R. Jay, M.D.  
  DR. JEFFREY R. JAY, M.D.  
       
  /s/ Mr. David Kroin  
  MR. DAVID KROIN  
 

Exhibit A

 

AGREEMENT REGARDING THE JOINT FILING OF SCHEDULE 13G

 

The undersigned hereby agree as follows:

 

(i)         Each of them is individually eligible to use the Schedule 13G to which this Exhibit is attached, and such Schedule 13G is filed on behalf of each of them; and

 

(ii)        Each of them is responsible for the timely filing of such Schedule 13G and any amendments thereto, and for the completeness and accuracy of the information concerning such person contained therein; but none of them is responsible for the completeness or accuracy of the information concerning the other persons making the filing, unless such person knows or has reason to believe that such information is inaccurate.

 

Date: June 24, 2013

 

  GREAT POINT PARTNERS, LLC  
       
  By: /s/ Dr. Jeffrey R. Jay, M.D.  
    Dr. Jeffrey R. Jay, M.D.,  
    as senior managing member  
       
  /s/ Dr. Jeffrey R. Jay, M.D.  
  DR. JEFFREY R. JAY, M.D.  
       
  /s/ Mr. David Kroin  
  MR. DAVID KROIN