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Prometheus Obtains Exclusive US Commercialization Rights for RENCAREX®

-Expands Its Oncology Franchise into the Adjuvant Treatment of Clear Cell Renal Cell Carcinoma-

San Diego, April 29, 2011 – Prometheus Laboratories Inc., a specialty pharmaceutical and diagnostic company, today announced that it has signed an exclusive agreement with WILEX AG for commercialization rights in the United States for RENCAREX® (girentuximab). RENCAREX® is a Phase III product candidate for adjuvant use in non-metastatic clear-cell renal cell cancer (ccRCC).

Under the terms of the agreement, WILEX will receive $19.0 million upfront payments and development fees plus milestone payments and royalties on U.S. net sales of RENCAREX®. In addition, Prometheus will co-fund a portion of the ongoing development of RENCAREX®. The deal terms also include an agreement whereby WILEX may be granted commercialization rights outside of the United States, including but not limited to Europe, to one of Prometheus’ marketed products or receive additional cash payments of up to $20 million.

Professor Olaf G. Wilhelm, Chief Executive Officer of WILEX, commented, “This is the deal we have been looking for, not only in financial, but also in commercial and strategic terms. We are very excited about WILEX’S new partnership with Prometheus since Prometheus has a proven track record in commercializing pharmaceutical and diagnostic products.”

“We are very pleased to enter into this partnership with WILEX as we continue to build our oncology franchise,” said Joseph M. Limber, President and Chief Executive Officer of Prometheus. “RENCAREX® is a great strategic fit with our current oncology portfolio in renal cell carcinoma. There is no product currently approved in the United States for patients who could have recurrence of ccRCC after a kidney resection. We look forward to working with WILEX to complete the development process and commercialize RENCAREX® in the United States.”

About RENCAREX®
RENCAREX® (girentuximab) is a highly specific chimeric monoclonal antibody that binds to a cell surface antigen, the CA IX-antigen, which is found on 95% of clear cell Renal Cell Carcinomas (ccRCC) and on various other solid tumors but not on healthy tissue. Approximately 208,500 new cases of kidney cancer are diagnosed each year worldwide and the most prevalent form is ccRCC. Roughly one third of the patients will die from RCC. Standard therapy for non-metastatic RCC is resection of the affected kidney (nephrectomy) followed by observation. Nevertheless, there is a high risk of disease recurrence. There is no adjuvant treatment approved by the FDA or EMA for patients after surgery. RENCAREX® is currently tested in a Phase III trial versus placebo in the adjuvant setting in 864 patients with non-metastatic clear cell renal cell cancer at high risk of recurrence after nephrectomy. WILEX expects the results from the interim analysis for efficacy of RENCAREX® in the second half of 2011. This analysis will provide critical information regarding the trial endpoint – disease-free survival – which could form the basis for the European application for marketing approval.

About Prometheus
Prometheus Laboratories Inc. is committed to improving lives through the development and commercialization of novel pharmaceutical and diagnostic products that enable physicians to provide greater individualized 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 therapeutics and diagnostics, Prometheus believes it can provide physicians with more targeted solutions to optimize care for their patients. Prometheus’ corporate offices are located in San Diego, California.

About WILEX AG
WILEX AG is a biopharmaceutical company based in Munich, Germany. Focused on oncology, the company has a broad portfolio of near-to-market therapeutic and diagnostic products for the targeted treatment and specific detection of various types of cancer. The company's therapeutic product candidates are based on antibodies and small molecules. Through its US subsidiary WILEX Inc. in Cambridge, MA, WILEX markets a portfolio of oncological biomarker tests under the brand Oncogene Science. These biomarkers can be used as companion diagnostics in clinical trials and for therapy monitoring. Furthermore, the acquisition of Heidelberg Pharma AG is set to give WILEX access to an attractive and highly promising antibody drug conjugate technology platform and a pre-clinical service business. The business model of WILEX covers the entire value chain in the oncology market and comprises research, technology, development collaboration as well as sales and marketing. WILEX's customers and partners include leading international pharmaceutical companies.

Contact:

Prometheus Laboratories Inc.

Mark Spring
Sr. Vice President, Finance & Chief Financial Officer
(858) 410-6824

or

Beth Kriegel
Vice President, Finance & Treasurer
(858) 410-2516