SCHEDULE 13G

Amendment No. 0
CERULEAN PHARMA INC
COMMON STOCK
Cusip #15708Q105

Cusip #15708Q105
Item 1: 	   	Reporting Person - FMR LLC
Item 4: 	   	Delaware
Item 5: 	   	0
Item 6: 	   	0
Item 7: 	   	2,431,400
Item 8: 	   	0
Item 9: 	   	2,431,400
Item 11: 	  	12.787%
Item 12: 	  	HC

Cusip #15708Q105
Item 1: 	   	Reporting Person - Edward C. Johnson 3d
Item 4: 	   	United States of America
Item 5: 	   	0
Item 6: 	   	0
Item 7: 	   	2,431,400
Item 8: 	   	0
Item 9: 	   	2,431,400
Item 11: 	  	12.787%
Item 12: 	  	IN

SCHEDULE 13G - TO BE INCLUDED IN STATEMENTS
FILED PURSUANT TO RULE 13d-1(b) or 13d-2(b)

Item 1(a). 	    	Name of Issuer:

  	  	          	CERULEAN PHARMA INC

Item 1(b). 	    	Name of Issuer's Principal Executive Offices:

  	  	          	840 MEMORIAL DRIVE5TH FLOOR
  	  	          	CAMBRIDGE, MA 02139
  	  	          	USA

Item 2(a). 	     	 Name of Person Filing:

  	   	               	 FMR LLC

Item 2(b). 	     	 Address or Principal Business Office or, if None,
Residence:

  	   	               	 245 Summer Street, Boston, Massachusetts 02210

Item 2(c). 	     	 Citizenship:

  	   	               	 Not applicable

Item 2(d). 	     	 Title of Class of Securities:

  	   	               	 COMMON STOCK

Item 2(e). 	     	 CUSIP Number:

  	   	               	 15708Q105

Item 3. 	    	This statement is filed pursuant to Rule 13d-1(b) or 13d-2(b)
and the person filing,
FMR LLC, is a parent holding company in accordance with Section 240.13d-
1(b)(ii)(G).   (Note:  See Item 7).

Item 4. 	    	Ownership

  	  	     	(a)    Amount Beneficially Owned: 	2,431,400

  	  	     	(b)    Percent of Class: 	12.787%

  	  	     	(c)    Number of shares as to which such person has:

  	  	     	       (i)    sole power to vote or to direct the vote: 	0

  	  	     	       (ii)    shared power to vote or to direct the vote: 	0

  	  	     	       (iii)    sole power to dispose or to direct the
disposition of: 	2,431,400

  	  	     	       (iv)    shared power to dispose or to direct the
disposition of: 	0

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.

  	    	     	Various persons have the right to receive or the power to
direct the receipt of dividends from, or the proceeds from the sale of, the
COMMON STOCK of CERULEAN PHARMA INC. The interest of one person, Select
Biotechnology Portfolio, an investment company registered under the
Investment Company Act of 1940, in the COMMON STOCK of CERULEAN PHARMA INC,
amounted to 1,901,400 shares or 10.000% of the total outstanding COMMON
STOCK at April 30, 2014.

Item 7. 	    	Identification and Classification of the Subsidiary Which
Acquired the Security Being Reported on By the Parent Holding Company.

  	    	     	See attached Exhibit A.

Item 8. 	    	Identification and Classification of Members of the Group.

  	    	     	Not applicable. See attached Exhibit A.

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 acquired in the ordinary course of
business and were not acquired for the purpose of and do not have the
effect of changing or influencing the control of the issuer of such
securities and were not acquired in connection with or as a participant in
any transaction having such purpose or effect.


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.

  	May 9, 2014
  	Date

  	/s/ Scott C. Goebel
  	Signature

  	Scott C. Goebel
  	 Duly authorized under Power of Attorney effective as of June 1, 2008,
by and on behalf of FMR LLC and its direct and indirect subsidiaries
SCHEDULE 13G - TO BE INCLUDED IN STATEMENTS
FILED PURSUANT TO RULE 13d-1(b) or 13d-2(b)

                The ownership of one investment company, Select
Biotechnology Portfolio, amounted to 1,901,400 shares or 10.000% of the
COMMON STOCK outstanding. Select Biotechnology Portfolio has its principal
business office at 245 Summer Street, Boston, Massachusetts 02210.



                Pursuant to the instructions in Item 7 of Schedule 13G,
Fidelity SelectCo, LLC ("SelectCo"), 1225 17th Street, Suite 1100, Denver,
Colorado 80202, a wholly-owned subsidiary of FMR LLC and an investment
adviser registered under Section 203 of the Investment Advisers Act of
1940, is the beneficial owner of 2,431,400 shares or 12.787% of the COMMON
STOCK outstanding of CERULEAN PHARMA INC ("the Company") as a result of
acting as investment adviser to various investment companies registered
under Section 8 of the Investment Company Act of 1940 (the "SelectCo
Funds").



                Edward C. Johnson 3d and FMR LLC, through its control of
SelectCo, and the SelectCo Funds each has sole power to dispose of the
2,431,400 owned by the SelectCo Funds.



                Members of the family of Edward C. Johnson 3d, Chairman of
FMR LLC, are the predominant owners, directly or through trusts, of Series
B voting common shares of FMR LLC, representing 49% of the voting power of
FMR LLC. The Johnson family group and all other Series B shareholders have
entered into a shareholders' voting agreement under which all Series B
voting common shares will be voted in accordance with the majority vote of
Series B voting common shares. Accordingly, through their ownership of
voting common shares and the execution of the shareholders' voting
agreement, members of the Johnson family may be deemed, under the
Investment Company Act of 1940, to form a controlling group with respect to
FMR LLC.



                Neither FMR LLC nor Edward C. Johnson 3d, Chairman of FMR
LLC, has the sole power to vote or direct the voting of the shares owned
directly by the Fidelity Funds, which power resides with the Funds' Boards
of Trustees. Fidelity carries out the voting of the shares under written
guidelines established by the Funds' Boards of Trustees.



                Members of the family of Edward C. Johnson 3d, Chairman of
FMR LLC, are the predominant owners, directly or through trusts, of Series
B voting common shares of FMR LLC, representing 49% of the voting power of
FMR LLC. The Johnson family group and all other Series B shareholders have
entered into a shareholders' voting agreement under which all Series B
voting common shares will be voted in accordance with the majority vote of
Series B voting common shares. Accordingly, through their ownership of
voting common shares and the execution of the shareholders' voting
agreement, members of the Johnson family may be deemed, under the
Investment Company Act of 1940, to form a controlling group with respect to
FMR LLC.


SCHEDULE 13G - TO BE INCLUDED IN STATEMENTS
FILED PURSUANT TO RULE 13d-1(b) or 13d-2(b)
RULE 13d-1(f)(1) AGREEMENT


                The undersigned persons, on May 9, 2014, agree and consent
to the joint filing on their behalf of this Schedule 13G in connection with
their beneficial ownership of the COMMON STOCK of CERULEAN PHARMA INC at
April 30, 2014.


  	FMR LLC

  	By /s/ Scott C. Goebel
  	Scott C. Goebel
  	Duly authorized under Power of Attorney effective as of June 1, 2008, by
and on behalf of FMR LLC and its direct and indirect subsidiaries

  	Edward C. Johnson 3d

  	By /s/ Scott C. Goebel
  	Scott C. Goebel
  	Duly authorized under Power of Attorney effective as of June 1, 2008, by
and on behalf of Edward C. Johnson 3d

  	Select Biotechnology Portfolio

  	By /s/ Scott C. Goebel
  	Scott C. Goebel
  	Secretary

Document-Separator. This page separates the filing documents of two
notifications.

Page   of

Exhibit A