Chimerix, Inc.
January 7, 2011

Chimerix Commences CMX001 Open-Label Clinical Study for the Treatment of Life-Threatening or Serious dsDNA Viral Infections

- New Expanded Access Study Builds on CMX001 Emergency IND and Clinical Experience

RESEARCH TRIANGLE PARK, NC, JANUARY 7, 2011 - Chimerix, Inc., a pharmaceutical company developing orally-available antiviral therapeutics, today announced that patient enrollment has begun in a multicenter, open-label clinical study of CMX001 (the CMX001-350 study) for the treatment of life-threatening or serious conditions caused by double-stranded DNA (dsDNA) viruses.

Under the expanded-access protocol developed in conjunction with the U.S. Food and Drug Administration (FDA), patients will receive treatment with CMX001 for any of 12 different dsDNA viral infections, including adenovirus (AdV), herpes viruses (cytomegalovirus (CMV), herpes simplex virus (HSV) and Epstein Barr virus), polyoma viruses (BK virus and JC virus), and pox viruses. The CMX001-350 study will enroll 200 patients at major medical centers primarily in the United States.

CMX001 is being developed by Chimerix for dual-use as a broad-spectrum antiviral for the treatment of life-threatening viral infections in immunocompromised patients and as a medical countermeasure in the event of a smallpox outbreak. Chimerix is currently conducting a Phase 2 dose-defining clinical study of CMX001 in immunocompromised hematopoietic stem cell transplant patients at risk of life-threatening infection with CMV, which has enrolled over 130 patients. Additionally, the Company is initiating a Phase 2 clinical study in immunocompromised pediatric and adult hematopoietic stem cell transplant patients with AdV infections.

“Data from this open-label clinical study will be a critical component of our strategy to develop CMX001 as a broad-spectrum antiviral agent,” said Kenneth I. Moch, President and CEO of Chimerix. “We anticipate that the CMX001-350 study will provide important supportive data for our overall clinical development program.”

“CMX001 is exhibiting a favorable tolerability profile and signs of potent antiviral activity across our clinical studies, including the more than 130 Emergency INDs requested by leading investigators,” said Wendy Painter, M.D., M.P.H., Chief Medical Officer of Chimerix. “The demand for CMX001 to treat life-threatening infections continues to grow among the clinical community, and we are extremely proud to provide CMX001 under this open-label study.”

CMX001-350 Open-Label Study Design

The primary objective of the multicenter open-label study of CMX001 is to provide CMX001 to patients with immediately life-threatening or serious disease caused by any of 12 different viral infections resulting from dsDNA viruses. The open-label study is expected to enroll 200 infected adult and pediatric patients. Critically-ill patients expected to enroll in this study in the highest numbers include immunocompromised patients suffering from a variety of dsDNA infections, particularly patients undergoing solid organ transplant or hematopoietic stem cell transplant. However, the study is intended for any patient with a serious dsDNA viral disease for whom no satisfactory alternate therapy is available and who does not qualify for other CMX001 clinical studies.1

The study will evaluate the safety, tolerability and antiviral activity of CMX001. Researchers will also evaluate the activity of CMX001 through changes in clinical signs and symptoms of infection. Patients will receive CMX001 orally twice weekly for up to three months, and treatment may be extended for up to six months depending on the patient’s clinical response. Antiviral activity will be measured by changes in viral burden from baseline in an individual patient’s condition and across all patients with a given dsDNA virus. Drug pharmacokinetics and any potential signs of drug resistance will also be assessed.

The clinical design parameters of the CMX001-350 study were based in large part on Chimerix’s experiences providing CMX001 to patients under investigator-held Emergency Investigational New Drug applications (EINDs). At the request of leading physicians, Chimerix has to date provided CMX001 to more than 130 patients under EINDs or foreign equivalent at over 45 medical centers in the United States, Canada, Europe and Israel. CMX001 has been used for the treatment of life-threatening dsDNA infections where either there are no FDA-approved treatments or the patients have failed the available treatments. Patients treated with CMX001 have had infections from all five classes of dsDNA viruses that infect humans, including AdV, herpes viruses such as CMV, HSV and Epstein Barr virus, polyoma viruses such as BK virus and JC virus, and pox viruses. Data from these EIND experiences have been recently reported in a number of publications and medical conferences, and are available on the Chimerix website at www.chimerix.com.

Additional information on study objectives, enrollment criteria and patient eligibility for the CMX001-350 study is available at www.clinicaltrials.gov.

About Chimerix

Chimerix is developing novel antiviral therapeutics with the potential to transform patient care in multiple settings, including transplant, oncology, acute care and global health.

The company’s lead candidate, CMX001, is being developed as a potential broad-spectrum antiviral agent for the treatment of life-threatening dsDNA viral diseases. Clinical studies of CMX001 include an ongoing Phase 2 study of the prevention/control of cytomegalovirus (CMV) in hematopoietic stem cell transplant patients (CMX001-201), a Phase 2 study being initiated for the treatment of adenovirus (AdV) infection in pediatric and adult hematopoietic stem cell transplant patients (CMX001-202), and an Open-Label Study (CMX001-305) for the treatment of any of 12 different dsDNA viral infections, including AdV, herpes viruses such as CMV, herpes simplex virus and Epstein Barr virus, polyoma viruses such as BK virus and JC virus, and pox viruses.

Over 325 people have received CMX001 to date, including over 130 patients treated under Emergency INDs. CMX001 has been well tolerated in all studies, with a growing body of evidence of the compound’s antiviral activity in humans. CMX001 is also being developed as a medical countermeasure in the event of a smallpox outbreak. Chimerix has received significant funding from the National Institute of Allergy and Infectious Disease to develop CMX001 for smallpox.

Chimerix’s second clinical-stage antiviral compound CMX157, a potent nucleoside analogue with activity against HIV and hepatitis B, is in development for the treatment of HIV infection including those caused by multi-drug resistant viruses. CMX157 has completed Phase 1 clinical studies demonstrating that the compound is well tolerated and that the active antiviral, TFV-PP, was measurable in peripheral blood mononuclear cells (PBMCs) after a single dose and remained detectable for six days, suggesting the possibility of a convenient, once-weekly dosing regimen. CMX157’s promising safety profile and efficient conversion to the active drug in PBMCs, coupled with the potent in vitro antiviral activity across diverse drug-resistant strains of HIV, indicate that this compound may directly address several limitations of current HIV therapies.

Led by a world-class antiviral drug development team, Chimerix is also leveraging the company’s extensive chemical library to pursue new treatments for hepatitis C virus, malaria and other global public health needs.