Prometheus Launches ProOncDx Cancer Diagnostics
Three New Tests Based on Breakthrough MicroRNA Technology

San Diego, October 15, 2009 – Prometheus Laboratories Inc., a specialty pharmaceutical and diagnostic company, today announced the nationwide commercial launch of three new cancer diagnostic products: ProOnc TumorSourceDx, ProOnc SquamousDx and ProOnc MesotheliomaDx. Each of these tests is based on recently developed, highly sensitive microRNA technology.

"Prometheus has a long and successful history of providing innovative diagnostics that complement targeted therapeutics to help physicians individualize patient care," said Joseph M. Limber, President and Chief Executive Officer of Prometheus. "Now we are proud to introduce the first three products from our cancer diagnostics portfolio with the launch of ProOncDx. We believe that these highly tissue-specific tests provide more objective and quantitative results than current methods, which, may lead to more personalized treatments for patients."

ProOnc TumorSourceDx identifies the tissue-of-origin of a metastatic tumor. The test identifies 25 different tumor types, including colon, liver, brain, breast, kidney, lung, ovary, pancreas, prostate and testis, and measures the expression level of 48 microRNA biomarkers. ProOnc TumorSourceDx uses a proprietary classifier to assign a primary site to the cancer sample based on the microRNA expression in the tumor and may become a critical tool in the detection of cancer of unknown primary (CUP).

ProOnc SquamousDx classifies non-small cell lung carcinoma tumors into two histological groups: cancers of squamous histology and non-squamous cancers. The test measures the expression level of a squamous microRNA biomarker to differentiate patients that have squamous cell carcinoma of the lung from patients that have non-squamous non-small cell lung cancer.

ProOnc MesotheliomaDx is a cutting-edge molecular diagnostic test that uses microRNA to differentiate malignant pleural mesothelioma from peripheral adenocarcinoma of the lung and metastatic carcinomas involving the lung and pleura.

"MicroRNAs are small, non-coding sequences of RNA that are critically important in many biological and pathological processes," said Harvey Pass, M.D., Professor of Cardiothoracic Surgery and Director of the Division of Thoracic Surgery and Thoracic Oncology at New York University Langone Medical Center and its NYU Cancer Institute. "The sensitivity and specificity of microRNA-based diagnostics should enable clinicians to differentiate particular cancer tissues with increased confidence, which may ultimately guide medical oncologists to deliver the safest and most efficacious therapy for their patients."

For more information about ProOncDx tests, please call (877) 378-4919 or visit www.prometheusoncology.com.

Prometheus acquired exclusive U.S. rights to ProOnc TumorSourceDx, ProOnc SquamousDx and ProOnc MesotheliomaDx from Rosetta Genomics (NASDAQ: ROSG) in April 2009. The tests are offered as miRview mets, miRview squamous and miRview meso outside of the U.S. In addition, Prometheus and Rosetta are collaborating to develop two new microRNA-based gastroenterology tests.

About Prometheus
Prometheus Laboratories Inc. is a specialty pharmaceutical and diagnostic company committed to developing and commercializing novel pharmaceutical and diagnostic products to help physicians individualize patient care. Prometheus is a leader in applying the principles of personalized medicine to the diagnosis and treatment of gastrointestinal diseases and is applying these principles to oncology. Its strategy includes the marketing and delivery of pharmaceutical products complemented by proprietary diagnostic testing services. By integrating pharmaceutical products and diagnostic testing services, Prometheus believes it can address the full continuum of care, thereby providing physicians with a comprehensive solution to treat chronic diseases. Prometheus’ corporate offices are located in San Diego.

ProOnc TumorSourceDx, ProOnc SquamousDx and ProOnc MesotheliomaDx are trademarks of Prometheus Laboratories Inc. miRview mets, miRview squamous and miRview meso are trademarks of Rosetta Genomics Ltd.

Contact
Pete De Spain
Director, Investor Relations
& Corporate Communications
Prometheus Laboratories Inc.
(858) 587-4117
pdespain @prometheuslabs.com

or

John F. Kouten
Chief Executive Officer
JFK Communications, Inc.
(609) 514-5117
jfkouten @jfkhealth.com