SCHEDULE 13G

Amendment No. 1
INFINITY PHARMACEUTICALS INC
COMMON STOCK
Cusip #45665G303
Check the appropriate box to designate the rule pursuant to which this
Schedule is filed:
[x] Rule 13d-1(b)
[ ] Rule 13d-1(c)
[ ] Rule 13d-1(d)

Cusip #45665G303
Item 1: Reporting Person - FMR LLC
Item 2: (a)  [ ]
        (b)  [ ]
Item 4: Delaware
Item 5: 750
Item 6: 0
Item 7: 750
Item 8: 0
Item 9: 750
Item 11: 0.001%
Item 12: HC

Cusip #45665G303
Item 1: Reporting Person - Abigail P. Johnson
Item 2: (a)  [ ]
        (b)  [ ]
Item 4: United States of America
Item 5: 0
Item 6: 0
Item 7: 750
Item 8: 0
Item 9: 750
Item 11: 0.001%
Item 12: IN



Item 1(a). Name of Issuer:

INFINITY PHARMACEUTICALS INC

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

784 Memorial Drive
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:

45665G303

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

Item 4. Ownership

(a) Amount Beneficially Owned: 750

(b) Percent of Class: 0.001%

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

(i) sole power to vote or to direct the vote: 750

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

(iii) sole power to dispose or to direct the disposition of: 750

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


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).

Item 6. Ownership of More than Five Percent on Behalf of Another Person.

One or more other persons are known to 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 INFINITY PHARMACEUTICALS INC. No one other person's interest
in the COMMON STOCK of INFINITY PHARMACEUTICALS INC is more than five percent
of the total outstanding COMMON STOCK.

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.

Item 9. Notice of Dissolution of Group.

Not applicable.

Item 10. Certifications.

By signing below I certify that, to the best of my knowledge and belief,
the securities referred to above were acquired and are held in the ordinary
course of business and 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.

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.

February 13, 2019
Date

/s/ Kevin M. Meagher
Signature

Kevin M. Meagher
Duly authorized under Power of Attorney effective as of September 28, 2018, by
and on behalf of FMR LLC and its direct and indirect subsidiaries*


* This power of attorney is incorporated herein by reference to Exhibit 24 to
the Schedule 13G filed by FMR LLC on October 9, 2018, accession number:
0000315066-18-002414.


Exhibit A


Pursuant to the instructions in Item 7 of Schedule 13G, the following table
lists the identity and Item 3 classification, if applicable, of each relevant
entity that beneficially owns shares of the security class being reported on
this Schedule 13G.

Entity   ITEM 3 Classification

FMR CO., INC  IA


Abigail P. Johnson is a Director, the Chairman and the Chief Executive Officer
of FMR LLC.

Members of the Johnson family, including Abigail P. Johnson, 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.

This filing reflects the securities beneficially owned, or that may be deemed
to be beneficially owned, by FMR LLC, certain of its subsidiaries and
affiliates, and other companies (collectively, the "FMR Reporters"). This
filing does not reflect securities, if any, beneficially owned by certain
other companies whose beneficial ownership of securities is disaggregated from
that of the FMR Reporters in accordance with Securities and Exchange
Commission Release No. 34-39538 (January 12, 1998).


RULE 13d-1(k)(1) AGREEMENT

The undersigned persons, on February 13, 2019, 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 INFINITY PHARMACEUTICALS INC at
December 31, 2018.

FMR LLC

By /s/ Kevin M. Meagher
Kevin M. Meagher
Duly authorized under Power of Attorney effective as of September 28, 2018, by
and on behalf of FMR LLC and its direct and indirect subsidiaries*

Abigail P. Johnson

By /s/ Kevin M. Meagher
Kevin M. Meagher
Duly authorized under Power of Attorney effective as of September 30, 2018, by
and on behalf of Abigail P. Johnson*


* This power of attorney is incorporated herein by reference to Exhibit 24 to
the Schedule 13G filed by FMR LLC on October 9, 2018, accession number:
0000315066-18-002414.