Merck & Co., Inc., one of the world's leading research-based pharmaceutical companies, and Sirna Therapeutics, Inc., a publicly held biotechnology company and a leader in developing a new class of medicines based on RNA interference (RNAi) technology, have entered into a definitive agreement under which Merck will acquire Sirna.

Under the terms of the agreement, Merck will acquire through a merger 100 per cent of the equity of Sirna at a price of $13 per share in cash, making Sirna a wholly owned subsidiary of Merck & Co., Inc. The transaction has a cash value of approximately $1.1 billion, a Merck press release stated.

Sirna Therapeutics has been at the forefront of efforts to create RNAi-based therapeutics, medicines which could significantly alter the treatment of disease. RNAi-based therapeutics selectively catalyze the destruction of the RNA transcribed from an individual gene. This enables an entirely novel approach to discovering drugs with the potential to produce highly specific, potent, and long-lasting effects.

The acquisition of Sirna complements the cutting-edge research on RNA expression that Merck has been doing since the 2001 acquisition of Rosetta Inpharmatics, Inc. "That research has led to a deeper understanding of the biological circuits that control the activity of cells, and thus the identification of many novel targets which can now be approached through the use of RNAi-based treatments," said Alan Sachs, M.D., Ph.D., vice president at Merck's Rosetta laboratories.

"We are delighted about our agreement to acquire Sirna Therapeutics, a company that has established a leading presence in the critically important area of RNAi," said Peter S. Kim, Ph.D., president, Merck Research Laboratories. "We believe that RNAi could significantly change the way in which we go about discovering and developing drugs, and could become a new way to treat patients with unmet medical needs."

"RNAi is a powerful enabler of drug discovery in cells, in animals, and in humans. We can potentially use this technology to target the activity of genes which control the activity of cancer cells, and so produce their destruction without damaging normal cells," said Stephen H. Friend, M.D., Ph.D., executive vice president and franchise head, Oncology and Neuroscience, Merck Research Laboratories.

Sirna's lead clinical development candidate, Sirna-027, is a chemically optimized, short interfering RNA (siRNA) currently moving into Phase II development for the treatment of the wet-form of age related macular degeneration (AMD) as part of a broad collaboration with Allergan, Inc. in the area of ophthalmic diseases. In addition to the collaboration with Allergan, Sirna has established a strategic alliance with GlaxoSmithKline for the development of siRNA compounds for the treatment of respiratory diseases. Besides its external collaborations, Sirna has several programs covering a broad range of therapeutic areas, including infectious diseases, metabolism, CNS and dermatology.

"We are extremely pleased to be joining forces with one of the world's premier pharmaceutical companies. Merck's decision to acquire Sirna speaks volumes about Sirna's expertise in the field of RNAi-based therapeutics, the breadth of our intellectual property estate and talent of our scientific and management team," said Howard W. Robin, president and chief executive officer of Sirna Therapeutics. "Combining the expertise of both companies will significantly accelerate the development of RNAi-based therapeutics."

"We are excited about the opportunity to undertake the discovery and development of therapeutic siRNAs with Merck, a company that clearly recognizes the potential of this breakthrough technology," said Sirna Senior Vice President of Research and Chief Scientific Officer Barry Polisky. "Merck's commitment to the development of RNAi-based therapeutics will ensure that this novel therapeutic modality will achieve its full potential."

Sirna stockholders owning approximately 36 per cent of Sirna's outstanding shares have committed to support the transaction and have entered into voting agreements. The acquisition is subject to clearance under the Hart-Scott-Rodino Antitrust Improvements Act and approval by the stockholders of Sirna and other customary closing conditions. The two companies expect to complete the acquisition in the first quarter of 2007.

Richard N. Kender, vice president of Business Development and Corporate Licensing at Merck, noted that Merck's acquisition of Sirna "is another example of Merck delivering on its strategy of aggressively pursuing biotechnology companies that complement our considerable internal research capabilities."