Agreement

Sirna Therapeutics and Targeted Genetics Form Huntington's Disease Collaboration

- Agreement Pairs Leaders in RNA Interference (RNAi) and AAV-Based Delivery Technologies

BOULDER, Colo. and SEATTLE, Jan. 11 -- Sirna Therapeutics, Inc. (Nasdaq: RNAI) and Targeted Genetics Corporation (Nasdaq: TGEN) today announced that they have established a collaboration to develop a novel therapy for the treatment of Huntington's Disease (HD), an incurable neurodegenerative disorder. The collaboration significantly advances Sirna's HD program by using Targeted Genetics' adeno-associated virus (AAV) delivery platform to develop an HD product.

The focus of the collaboration will be the development of a therapeutic short interfering RNA (siRNA) targeting the gene that encodes the Huntington's Disease protein. The siRNA will be expressed from an AAV-vector. RNAi is a mechanism used by cells to regulate the expression of genes and replication of viruses. The RNA interference mechanism uses siRNA to induce the destruction of target RNA using naturally occurring cellular protein machinery. Sirna's scientific advisor and collaborator, Dr. Beverly Davidson at the University of Iowa, has published data demonstrating that the delivery of siRNA using an AAV vector efficiently inhibited gene expression in an animal model of spinocerebellar ataxia 1 (SCA1), a member of a class of inherited human neurodegenerative diseases that includes Huntington's Disease (Nature Medicine 10:816-820 [2004]).

"There are no treatments for Huntington's Disease, and we believe that vector expressed RNAi-based approaches may have significant potential in slowing or halting disease progression," said Howard Robin, President and Chief Executive Officer at Sirna. "Dr. Davidson's work using AAV vectors to deliver siRNA for the treatment of related neurodegenerative disorders is quite promising. Through the collaboration announced today we are gaining access to Targeted Genetics' extensive capabilities in the development, clinical testing and manufacture of AAV-based products. We are excited to explore the potential of AAV-RNAi therapies for Huntington's Disease, and are very pleased to be working with the leading AAV-based product development company."

"We are excited to continue expanding our AAV-based gene delivery platform into the area of RNA interference by working with Sirna, the leading company developing this innovative technology," said H. Stewart Parker, President and Chief Executive Officer of Targeted Genetics. "This collaboration is consistent with our strategy to leverage our gene delivery capabilities beyond gene replacement. Shutting down the production of disease-causing proteins by delivering expressed RNAi sequences complements the other applications of our technologies: providing a functional copy of the gene deficient in cystic fibrosis, delivering a gene encoding a therapeutic protein for rheumatoid arthritis and stimulating the immune system using a DNA-based vaccine against HIV."

Under the terms of the agreement, development costs and revenue from partnering and sales of products developed under the col