RXi Pharmaceuticals Reports Financial Results for the First Quarter of 2013 Acquired substantially all of OPKO Health, Inc. s siRNA assets in early 2013 Completed a private placement in March 2013 with gross proceeds of

RXi Pharmaceuticals Reports Financial

Results for the First Quarter of 2013

Acquired substantially all of OPKO Health, Inc. s siRNA assets in early 2013

Completed a private placement in March 2013 with gross proceeds of $16.4 million, led by OPKO Health, Inc. and Frost Gamma Investments Trust

Completion of enrollment in Second Phase 1 Trial for RXI-109 Program.

WESTBOROUGH, MA May 15, 2013 RXi Pharmaceuticals Corporation (OTC: RXII), a biotechnology company focused on

discovering, developing and commercializing innovative therapies addressing major unmet medical needs using RNA-targeted technologies, today reported its financial results for quarter ended March 31, 2013, and provided a business update.

The first quarter of 2013 has been a good one for RXi Pharmaceuticals, with steady progress - in line with our planning and

budget - for our research and development activities , commented Dr Geert Cauwenbergh, President and CEO of the Company. He added that, In addition to coming near the end of the Phase 1 clinical development stage

for our anti-scarring compound RXI-109, RXi Pharmaceuticals has been able to significantly strengthen its cash balance by attracting new investors in its recent financing including our largest new shareholders, OPKO Health Inc., Frost

Gamma Investments Trust and Broadfin Capital, LLC, in addition to existing investors like Tang Capital Partners, LP and RTW Investments, LLC.

Quarterly Financial Highlights

Cash and Cash Equivalents

At March 31, 2013, RXi had cash and cash equivalents of approximately $19.6 million, compared with $5.1 million at December 31, 2012.

Net Loss and Net Loss Applicable to Common Stockholders

The net loss for the three months ended March 31, 2013 was $14.4 million, including $0.6 million in non-cash share based compensation expense, compared with a net loss of $1.9 million, including $0.2

million in non-cash share based compensation expense, for the three months ended March 31, 2012. The increase in the net loss of $12.5 million was primarily attributable to a one-time charge of $12.3 million related to the fair value of common

shares issued to OPKO Health, Inc. ( OPKO ) for the purchase of substantially all of OPKO s RNAi-related assets.

applicable to common stockholders for the three months ended March 31, 2013 was $17.9 million compared with a net loss applicable to common stockholders of $1.9 million for the comparable period in 2012. The increase in net loss applicable to

common stockholders of $16.0 million was primarily attributable to the aforementioned increase in the net loss as compared to prior year and $3.5 million of dividends paid in the form of preferred stock to the Company preferred shareholders.

revenues for the three months ended March 31, 2013 was $0.1 million as compared with no revenue for the comparable period in 2012. The increase in total revenues for the three months ended March 31, 2013 was due to the recognition of work

completed on the Company s government grants during the period.

Research and Development Expense

Research and development expenses for the three months ended March 31, 2013 were $13.8 million, compared with $1.2 million for the three months ended March 31, 2012. The increase of $12.6

million is largely due to the one-time charge of $12.3 million related to the fair value of common shares issued to OPKO for the purchase of substantially all of OPKO s RNAi-related assets and an increase of $0.3 million in employee stock-based

compensation expense.

General and Administrative Expenses

General and administrative expenses for the three months ended March 31, 2013 were $0.7 million, compared with $0.8 million for the three months ended March 31, 2012. The decrease in general

administrative expenses of $0.1 million was an increase in employee stock-based compensation expense offset by a decrease in general and administrative expenses, including lower personnel costs and a decrease in the use of outside professional

services and consultants.

Preferred Stock Dividends

Accretion of Series A convertible preferred stock dividends was $3.5 million for the three months ended March 31, 2013, compared with no Series A convertible preferred stock dividends for the year

comparable period in 2012. Upon the Company s completion of the spin-off from its former parent company, Galena Biopharma, Inc., the Company issued shares of Series A convertible preferred stock to certain investors. The increase in preferred

stock dividends relates to the fair value of dividends paid to the Series A preferred stock holders during the quarterly period.

Quarter 2013 and Recent Corporate Highlights

RXi Pharmaceutical s first clinical program centers on RXI-109, a self-delivering RNAi compound (sd-rxRNA ) developed by RXi for the reduction of dermal scarring in planned surgeries. RXI-109 is designed to reduce the expression of CTGF (connective tissue growth factor), a

critical regulator of several biological pathways involved in fibrosis, including scar formation in the skin. The first clinical trial of RXI-109, initiated in June 2012, was designed to evaluate the safety and tolerability of several dose levels of

RXI-109 in humans and may provide preliminary evidence of surgical scar reduction. A second Phase 1 trial also initiated in 2012 evaluates the safety of multiple (3) administrations of RXI-109 over 2 weeks and will allow the evaluation of

RXI-109 s effect on scarring-related biomarkers. As there are currently no FDA-approved drugs to prevent scar formation, a therapeutic of this type could have great benefit for trauma and surgical patients, as a treatment during the surgical

revision of existing unsatisfactory scars, and in the treatment, removal and inhibition of keloids (scars which extend beyond the original skin injury).

About RXi Pharmaceuticals Corporation

RXi Pharmaceuticals Corporation (OTC: RXII) is a

biotechnology company focused on discovering, developing and commercializing innovative therapies based on its proprietary, next-generation RNAi platform. Therapeutics that use RNA interference, or RNAi, have great promise because of

their ability to silence, or down-regulate, the expression of a specific gene that may be overexpressed in a disease condition. Building on the pioneering work of scientific founder and Nobel Laureate Dr. Craig Mello, RXi s

first RNAi product candidate, RXI-109, which targets CTGF (connective tissue growth factor), entered into a human clinical trial in June 2012 to evaluate its safety, tolerability and potential efficacy for scar prevention. For more information,

please visit www.rxipharma.com.

Forward-Looking Statements

This press release contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. Forward-looking statements can be identified by words such as:

intend, believe, expect, may, should, designed to, will and similar references. Such statements include, but are not limited to, statements about: our ability to

successfully develop RXI-109 and our other product candidates; the timing and future success of our clinical trials with RXI-109; our expectation that we are coming near the end of the Phase 1 clinical development stage for RXI-109; and our ability

to implement cost-saving measures. Forward-looking statements are neither historical facts nor assurances of future performance. Instead they are based only on our current beliefs, expectations and assumptions regarding the future of our business,

future plans and strategies, projections, anticipated events and trends, the economy and other future conditions. Because forward-looking statements relate to the future, they are subject to inherent uncertainties, risks and changes in circumstances

that are difficult to predict and many of which are outside of our control. Our actual results and financial condition may differ materially from those indicated in the forward-looking statements. Therefore, you should not rely on any of these

forward-looking statements. Important factors that could cause our actual results and financial condition to differ materially from those indicated in the forward-looking statements include, among others: the risk that our clinical trial with

RXI-109 may not be successful in evaluating the safety and tolerability of RXI-109 or providing preliminary evidence of surgical scar reduction; the successful and timely completion of clinical studies; uncertainties regarding the regulatory

process; the availability of funds and resources to pursue our research and development projects, including our clinical trials with RXI-109; general economic conditions; and those identified under Risk Factors in the Company s most

recently filed Annual Report on Form 10-K, Quarterly Report on Form 10-Q and in other filings the Company periodically makes with the SEC. The Company does not undertake to update any of these forward-looking statements to reflect a change in its

views or events or circumstances that occur after the date of this press release.

RXi PHARMACEUTICALS CORPORATION (REGISTRANT) AND PREDECESSOR (RNAi)

(A Development Stage Company)

CONDENSED STATEMENTS OF OPERATIONS

(Amounts in thousands, except share and per share data)

RXi PHARMACEUTICALS CORPORATION (REGISTRANT)

(A Development Stage Company)

CONDENSED BALANCE SHEETS