Response Genetics Expands Proprietary ResponseDX: Lung™ and ResponseDX: Colon™ Genetic Tests to Include Additional Patented Biomarkers Associated With Chemotherapy Response

Business Wire, April 30, 2009

Company Also Announces a Run Rate of More Than 700 ResponseDX™ Tests Ordered per Quarter, an Approximate 40 Percent Increase Over the Previous Quarter

LOS ANGELES -- Response Genetics Inc. (Nasdaq:RGDX), a company focused on the development and sale of molecular diagnostic tests for cancer, today announced that it has expanded its ResponseDX: Lung™ genetic test panel to assess thymidylate synthase (TS), the expression of which is associated with sensitivity to pemetrexed, a drug used to treat non-small cell lung cancer (NSCLC). The company also announced the inclusion of EGF receptor (EGFR) gene expression to its ResponseDX: Colon™ genetic test panel, providing additional sensitivity to the widely used chemotherapy combination irinotecan, fluorouracil and folinic acid (FOLFIRI). Both proprietary ResponseDX™ panels are available nationwide through the company’s expanded national sales force.

As described in the NCCN 2009 Clinical Practice Guidelines in Oncology NSCLC, ERCC1, RRM1, EGFR and KRAS genes are highlighted as predictive and prognostic biomarkers in this hard-to-treat form of lung cancer.1 The ResponseDX: Lung™ genetic test panel is believed to be the only test that assesses all of these genes and has been validated by prospective clinical trials.2,3

By assessing mutations and expression levels across multiple genes, the ResponseDX™ panel test may help physicians tailor treatment to their patients and potentially help improve outcomes and reduce risk.

“This approach is the future and the future is now,” said David R. Gandara, M.D., professor of medicine, associate director of clinical research and director of the Thoracic Oncology Program, University of California Davis Cancer Center, and a director of Response Genetics.

“We are pleased with the market acceptance of the ResponseDX™ tests, which is now at a run rate of more than 700 tests ordered per quarter, an approximate 40 percent increase over the previous quarter,” said Kathleen Danenberg, Response Genetics president and CEO. “As a company, Response Genetics is committed to expanding its existing ResponseDX™ tests and developing new ones as we identify genes that correlate with therapeutic benefit. The addition of TS and EGFR to our ResponseDX: Lung™ and ResponseDX: Colon™ genetic tests, respectively, should increase their applicability by giving physicians even more information about which cancer treatments are most likely to benefit their patients.”

Approximately 160,000 colon cancer patients and 200,000 non-small lung cancer patients may benefit from these tests per year in the United States.

About ResponseDX™ Tests

Response Genetics has developed PCR-based genetic tests — ResponseDX: Lung™ and ResponseDX: Colon™ — to help physicians with therapeutic treatment decisions for patients with non-small cell lung cancer (NSCLC) and colorectal cancer (CRC). The proprietary ResponseDX™ panels include three key genes: excision repair cross-complementing factor 1 (ERCC1), thymidylate synthase (TS) and epidermal growth factor receptor (EGFR). These tests also include the analysis of K-ras (KRAS) gene mutations, which are a strong predictor of non-response to and no benefit from EGFR inhibitors. Response Genetics’ KRAS mutation analysis provides one of the fastest turnaround times in the industry and accurate results on the smallest biopsies. The benefit for patients is that, in many cases, no tissue samples other than the pre-treatment diagnostic biopsy will be required for the biomarker analysis. Using ResponseDX™ testing, clinicians may make better treatment decisions by adopting a cost-effective panel approach.

About Response Genetics, Inc.

Response Genetics, Inc. (“RGI”) (the “Company”) (Nasdaq:RGDX) is focused on the development and sale of molecular diagnostic tests for cancer. RGI’s technologies enable extraction and analysis of genetic information from genes derived from tumor samples stored as formalin-fixed and paraffin-embedded specimens. In addition to diagnostic testing services, RGI generates revenue from the sales of its proprietary analytical pharmacogenomic testing services of clinical trial specimens to the pharmaceutical industry. The Company was founded in 1999 and its principal headquarters are located in Los Angeles, California. For more information, please visit www.responsegenetics.com.

Forward-Looking Statement Notice

Except for the historical information contained herein, this press release and the statements of representatives of RGI related thereto contain or may contain, among other things, certain forward-looking statements, within the meaning of the Private Securities Litigation Reform Act of 1995.