PRESS RELEASE: Merck Licenses SNALP Technology from Protiva

MERCK LICENSES SNALP TECHNOLOGY FROM PROTIVA

Protiva to Receive One-Time Payment with Potential Milestone and Royalty Payments as Part of Broader Agreement

VANCOUVER, BRITISH COLUMBIA--(October 16, 2007)

Protiva Biotherapeutics Inc. today reported that it has granted Merck & Co., Inc. a non-exclusive license to Protiva's SNALP (Stable Nucleic Acid-Lipid Particles) technology for ongoing research and development of therapeutics in the emerging field of RNA interference (RNAi).

Under the terms of the broader agreement Protiva will receive a one-time payment from Merck with the potential for milestone and royalty payments based upon the developmental progress of future RNAi-based product candidates. In addition, Protiva has agreed to cease all litigation between Protiva and Sirna Therapeutics Inc, a wholly owned subsidiary of Merck, including the removal of a preliminary injunction granted by the Superior Court of California in March 2007. Financial details were not disclosed.

Protiva's President and CEO Dr. Mark Murray said, "Merck's licensing of our 'SNALP' technology is an important validation of the skill of our scientific team and our leadership position in the siRNA delivery space. Protiva is moving forward with financial strength and a continued focus on the development of new therapeutic products and business alliances."

"We are pleased to have licensed Protiva's SNALP technology," said Alan Sachs M.D. Ph.D., vice president of RNA Therapeutics for Merck. "This technology can now be used to advance Merck's RNAi-based therapeutic development programs."

RNAi, which relies on the use of specifically designed short interfering RNA (siRNA) molecules, is a technology with the potential to fundamentally change how we treat serious human diseases such as cancer, HIV, influenza, Ebola virus infections and metabolic conditions such as high cholesterol. Dr. Andrew Fire and Dr. Craig Mello, the pioneers of RNAi, were awarded the Nobel Prize for Physiology or Medicine in 2006 for their discovery about how genes are controlled within living cells. Today, RNAi represents one of the most promising and rapidly advancing fields in biology and drug development.

About Protiva

Founded in 2001, Protiva Biotherapeutics Inc. is focused on the development of nucleic acid based pharmaceutical products to fight serious human diseases, such as cancer, influenza (including H5N1), Ebola, inflammatory diseases and other chronic viral infections. Protiva's proprietary Stable Nucleic-Acid Lipid Particle (SNALP) technology is an encapsulation and delivery system for nucleic acid payloads, such as short interfering RNA (siRNA), to target cells. It represents a breakthrough in the field of RNA interference.

Protiva is headquartered in Vancouver, BC with offices in Seattle, Washington. For more information, visit www.protivabio.com [1].