Infinity Announces Closing of Public Offering and Exercise of Over-Allotment Option

  Infinity Announces Closing of Public Offering and Exercise of Over-Allotment
  Option

Business Wire

CAMBRIDGE, Mass. -- December 18, 2012

Infinity Pharmaceuticals, Inc. (NASDAQ: INFI) today announced the closing of
its previously announced underwritten registered public offering of common
stock. The total number of shares of common stock sold was 6,551,461, composed
of 5,696,923 shares of common stock initially offered and an additional
854,538 shares of common stock sold pursuant to the exercise of the
underwriters' over-allotment option, in each case at a public offering price
of $26.33 per share. All of the shares in the offering were sold by Infinity.
The gross proceeds to Infinity from the offering, before deducting
underwriting discounts and commissions and offering expenses, are
approximately $172.5 million.

The joint book-running managers for the offering were Morgan Stanley & Co. LLC
and J.P. Morgan Securities LLC. BofA Merrill Lynch and Deutsche Bank
Securities Inc. acted as co-lead managers. Additionally, Stifel Nicolaus
Weisel acted as co-manager.

The securities described above were offered by Infinity pursuant to an
automatically effective shelf registration statement that was previously filed
with the Securities and Exchange Commission (SEC). The final prospectus
supplement and accompanying prospectus related to this offering are located on
the SEC’s website, www.sec.gov. Copies of the final prospectus supplement and
accompanying prospectus may also be obtained from:

                                        
Morgan Stanley & Co. LLC                      J.P. Morgan Securities LLC
Attn: Prospectus Department                   c/o Broadridge Financial
                                              Solutions
180 Varick Street, 2nd Floor                  1155 Long Island Avenue
New York, NY 10014                            Edgewood, NY 11717
Phone: 866-718-1649                           Phone: 866-803-9204
Email: prospectus@morganstanley.com
                                              

This press release does not constitute an offer to sell or a solicitation of
an offer to buy the securities described above, nor shall there be any sale of
these securities, in any state or other jurisdiction in which such offer,
solicitation, or sale would be unlawful prior to the registration or
qualification under the securities laws of any such state or other
jurisdiction.

About Infinity Pharmaceuticals, Inc.

Infinity is an innovative drug discovery and development company seeking to
discover, develop and deliver to patients best-in-class medicines for diseases
with significant unmet need. Infinity combines proven scientific expertise
with a passion for developing novel small molecule drugs that target emerging
disease pathways. Infinity’s programs focused on the inhibition of
phosphoinositide-3-kinase and heat shock protein 90 are evidence of its
innovative approach to drug discovery and development.

Forward-Looking Statements

This press release contains forward-looking statements within the meaning of
The Private Securities Litigation Reform Act of 1995. You should not place
undue reliance on these forward-looking statements as actual results may
differ materially from those projected or implied in these forward-looking
statements. Factors that may cause such a difference include, without
limitation, risks and uncertainties relating to Infinity’s business, which can
be found in Infinity’s current report on Form 8-K filed with the SEC on
December 12, 2012, and in other filings that Infinity makes with the SEC. Any
forward-looking statements contained in this press release speak only as of
the date hereof, and Infinity anticipates that subsequent events and
developments will cause its views to change. While Infinity may elect to
update these forward-looking statements at some point in the future, Infinity
expressly disclaims any obligation to update any forward-looking statements,
whether as a result of new information, future events or otherwise.

Contact:

Infinity Pharmaceuticals, Inc.
Jaren Irene Madden, 617-453-1336
Jaren.Madden@infi.com