RXi Pharmaceuticals Strengthens NeuVax TM (E75) Patent Portfolio RXi acquires patent rights covering use of NeuVax in combination with trastuzumab (Herceptin ; Genentech/Roche); and use in low-to-intermediate HER2 breast

RXi Pharmaceuticals Strengthens NeuVax TM (E75) Patent Portfolio

Worcester, MA, July 13, 2011 RXi Pharmaceuticals Corporation (NASDAQ: RXII), a biotechnology

company focused on discovering, developing and commercializing innovative therapies addressing

major unmet medical needs using targeted biotherapeutics, announced today that it expanded its

patent portfolio with additional patents covering worldwide rights to develop and commercialize

NeuVax (E75). The patents licensed from The Henry M. Jackson Foundation for the Advancement of

Military Medicine, Inc. (HJF) cover the use of NeuVax in combination with trastuzumab (Herceptin ;

Genentech/Roche), and use in low-to-intermediate HER2 (Human Epidermal growth factor Receptor)

breast cancer patients not eligible for Herceptin therapy. These patents are added to the growing

family of patents for RXi to support the development of NeuVax in a variety of indications and

countries. NeuVax was discovered at The M. D. Anderson Cancer Center (MDACC) and licensed from

NeuVax consists of the E75 peptide derived from HER2 combined with the immune adjuvant granulocyte

macrophage-colony stimulating factor (GM-CSF). RXi recently reported Phase 2 results at the

American Society of Clinical Oncology (ASCO) annual meeting which showed NeuVax (E75), when

combined with trastuzumab in HER2 over-expressing patients, demonstrated 0% recurrence at 48

months, with an excellent safety and tolerability profile. Thus, combination of NeuVax and

trastuzumab represents a potential expansion of the market for NeuVax to HER2 3 breast cancer

patients in the adjuvant setting.

Strengthening the breadth and depth of our intellectual property portfolio is critical to building

value and the foundation of our NeuVax strategy, stated Mark J. Ahn, PhD, President and CEO. We

look forward to initiating the NeuVax Phase 3 clinical trial in breast cancer, which is targeted to

begin in the first half of 2012.

COL George E Peoples, MD, FACS, is the inventor of the two new patents and conducted the Phase 1

and Phase 2 clinical trials of NeuVax. Dr. Peoples is Director, Cancer Vaccine Development

Program; Deputy Director, United States Military Cancer Institute (USMCI); Professor, Surgery,

University of the Health Sciences; Chief, Surgical Oncology, Brooke Army Medical

Center (BAMC) and Professor (adjunct), Surgical Oncology, M. D. Anderson Cancer Center. USMCI is a

component of the Uniformed Services University of the Health Sciences, an institution of higher

learning within the Department of Defense, an agency of the U. S. Government, located in Bethesda,

NeuVax consists of the E75 peptide derived from HER2 combined with the immune adjuvant granulocyte

macrophage-colony stimulating factor (GM-CSF). Treatment with NeuVax stimulates cytotoxic (CD8 ) T

cells in a highly specific manner to target cells expressing any level of HER2. NeuVax is given as

an intradermal injection once a month for six months, followed by a booster injection once every

six months. Based on a successful Phase 2 trial, which achieved its primary endpoint of

disease-free survival (DFS), the Food and Drug Administration (FDA) granted NeuVax a Special

Protocol Assessment (SPA) for its Phase 3 PRESENT (Prevention of Recurrence in

Early-Stage, Node-Positive Breast Cancer with Low to Intermediate HER2

Expression with NeuVax Treatment) study. The trial is expected to

commence in the first half of 2012.

According to the National Cancer Institute, over 200,000 women in the U.S. are diagnosed with

breast cancer annually. Of these women, about 75% test positive for Human Epidermal growth factor

Receptor 2 (IHC 1 , 2 or 3 ). Only 25% of all breast cancer patients, those with HER2 3 disease

are eligible for Herceptin (trastuzumab; Roche-Genentech) which had revenues of over $5 billion in

2010. NeuVax targets the remaining 50% of HER2 positive patients (HER2 1 and 2 ) who achieve

remission with current standard of care, but have no available HER2 targeted adjuvant treatment

options to maintain their disease free status.

The Henry M. Jackson Foundation for the Advancement of Military Medicine, Inc. (HJF)

HJF, located in Rockville, Maryland, is a private, not-for-profit organization chartered by

Congress to support medical education and research at the Uniformed Services University of the

Health Sciences and throughout the military medical community.

About RXi Pharmaceuticals Corporation

RXi Pharmaceuticals Corporation (NASDAQ: RXII) is a biotechnology company focused on discovering,

developing and commercializing innovative therapies addressing major unmet medical needs using

targeted biotherapeutics. For more information, 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. Such statements include, but are not limited to, statements about

our and patent rights, our expectations, plans and prospects for the development of our products,

and milestones and royalties that could become payable in connection with our recent licenses.

These forward-looking

statements about future expectations, plans and prospects of the development

of the Company s products are subject to a number of risks, uncertainties and assumptions,

including 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. Actual results may differ materially from those contemplated by these forward-looking

statements. 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