In accordance with regulatory requirements, Merck Serono has informed regulatory agencies in its marketing territories outside the U.S. and Japan about this serious adverse event. Study investigators and ethics committees are being notified of this PML case. Merck Serono is working diligently with the European Medicines Agency (EMEA) and other regulatory agencies to update the product information accordingly, issue a 'Dear Doctor Letter' to all dermatologists and to determine if further action is needed.

"Our primary concern is the safety of patients," said Guy Braunstein, Chief Medical Officer Merck Serono. "We have well-established systems and processes in place to monitor the safety of our medical products and to detect safety signals on an ongoing basis. Although this appears to be an isolated case among more than 46,000 patients treated with Raptiva(R) we want to ensure investigators and prescribers are made aware, so that they can make informed treatment decisions."

The case in the United States was reported to Genentech in late September as part of the company's ongoing safety monitoring and surveillance program. Based on the medical information available to date, it cannot be excluded that Raptiva(R) may have had a contributory role in the development of PML in this patient. There are no other cases of confirmed PML in patients treated with Raptiva(R). Previously, there has been a report by Genentech of a 62-year old patient treated with Raptiva in the United States who developed progressive neurologic symptoms and died of an unknown cause.

Patients who are currently on Raptiva therapy should discuss the benefits and risks of Raptiva with their physicians. It is important for patients not to change or stop treatment without first talking with their physician. Physicians are advised to follow the guidance provided in the Summary of Product Characteristics (SmPC) when switching or stopping treatment with Raptiva.

About PML PML is a rare, progressive, demyelinating disease of the central nervous system that usually leads to death or severe disability. PML is caused by activation of the John Cunningham, (JC) virus. JC virus resides in latent form in up to 80 percent of healthy adults, typically only causing PML in immunocompromised patients. The factors leading to activation of the latent infection are not fully understood, though abnormalities in T cells may be important for reactivation and PML. PML has been reported in the published literature in HIV-positive patients, as well as immunosuppressed cancer patients (including patients with hematologic malignancies), organ transplant recipients, and patients with autoimmune diseases. There are no known interventions that can reliably prevent or adequately treat PML.

About Raptiva(R) Raptiva(R) (efalizumab) is a humanized therapeutic antibody designed to selectively and reversibly block the activation, reactivation and trafficking of T-cells that are critically involved in the psoriatic skin inflammation. Raptiva(R) is designed to be administered once weekly via subcutaneous injection and can be self-administered by patients at home. Raptiva(R) received EU approval for the "Treatment of adult patients with moderate-to-severe chronic plaque psoriasis who have failed to respond to, or who have a contraindication to, or are intolerant to other systemic therapies including ciclosporine, methotrexate and PUVA". Common adverse events observed with Raptiva(R) include headache, infections (e.g., common cold), chills, pain, nausea, asthenia (weakness), and fever, which usually diminish after the initial doses. For complete information on the safety profile of Raptiva(R), the patient information leaflet should be consulted. Raptiva(R) safety data have now been accumulated from ten years of clinical development and post-marketing experience in psoriasis patients. Raptiva(R) is a medicinal product subject to medical prescription. Treatment with Raptiva(R) should be initiated by a physician specialized in dermatology. The Marketing Authorization Holder of Raptiva(R) in the European Union is Serono Europe Ltd, an affiliate of Merck Serono S.A. The full Summary of Product Characteristics (SPC) for Raptiva(R) is available on http://www.emea.europa.eu/humandocs/Humans/EPAR/raptiva/raptiva.htm

Merck Serono has the rights to develop and market Raptiva(R) worldwide outside of the United States and Japan. To date, Raptiva(R) is available in 65 countries, amongst them many countries in Europe, Latin America, Asia as well as Australia and Canada. Raptiva(R) is licensed from Genentech, Inc., and Genentech retains development and marketing rights in the United States, where Raptiva(R) has been available since November 2003. About Psoriasis Psoriasis is a T-cell mediated disease, which is characterized by abnormal cell growth of keratinocytes and chronic inflammation clinically visible as thick, red, scaly, inflamed patches and plaques. Plaque psoriasis, the most common form of the disease, is characterized by sharp-edged inflamed patches of skin ("lesions") topped with silvery white scales. Psoriasis can be limited to a few spots, typically knees and elbows, but can also involve extensive areas of the body. Although it is highly visible, psoriasis is not a contagious disease. While there are a number of medications that may help control the symptoms of psoriasis, there currently is no known permanent cure.

Merck Serono Merck Serono is the division for innovative prescription pharmaceuticals of Merck, a global pharmaceutical and chemical group. Headquartered in Geneva, Switzerland, Merck Serono discovers, develops, manufactures and markets innovative small molecules and biopharmaceuticals to help patients with unmet medical needs. Its North American business operates in the United States and Canada as EMD Serono. Merck Serono has leading brands serving patients with cancer (Erbitux(R)), multiple sclerosis (Rebif(R)), infertility (Gonal-f(R)), endocrine and cardiometabolic disorders (Glucophage(R), Concor(R), Euthyrox(R), Saizen(R), Serostim(R)), as well as psoriasis (Raptiva(R)). With an annual R&D expenditure of around EUR 1bn, Merck Serono is committed to growing its business in specialist-focused therapeutic areas including neurodegenerative diseases, oncology, fertility and endocrinology, as well as new areas potentially arising out of research and development in autoimmune and inflammatory diseases.

Merck Merck is a global pharmaceutical and chemical company with total revenues of EUR 7.1 billion in 2007, a history that began in 1668, and a future shaped by 31,946 employees in 60 countries. Its success is characterized by innovations from entrepreneurial employees. Merck's operating activities come under the umbrella of Merck KGaA, in which the Merck family holds an approximately 70% interest and free shareholders own the remaining approximately 30%. In 1917 the U.S. subsidiary Merck & Co. was expropriated and has been an independent company ever since. For more information, please visit http://www.merckserono.net or http://www.merck.de Merck Serono, 9 Chemin des Mines, 1202 Geneva, Switzerland; Media Relations, Tel.: +41-22-414-36-00