BERKELEY, Calif. & WHITEHOUSE STATION, N.J.–(EMWNews)–Dynavax Technologies Corporation (Nasdaq:DVAX) and Merck & Co., Inc.

announced today top-line immunogenicity results from a Phase 3 clinical

trial comparing HEPLISAV™, an investigational

hepatitis B virus (HBV) vaccine, to a currently marketed HBV vaccine,

Engerix-B^{® (1)}. The

study achieved its primary endpoint. HEPLISAV is being jointly developed

by Dynavax and Merck for use in adults and in patients with end stage

renal disease.

This study, called PHAST (Phase 3 HeplisAv Short-regimen Trial),

evaluated a two-dose regimen of HEPLISAV administered at 0 and 1 month

compared to a three-dose regimen of Engerix-B^®

administered at 0, 1 and 6 months. The primary endpoint was the

proportion of subjects who developed protective antibodies to hepatitis

B after administration. In PHAST, 95.1 percent of subjects who received

two doses of HEPLISAV (n=1,819) developed protective antibodies to

hepatitis B when measured at 12 weeks versus 81.1 percent of subjects

who received three doses of Engerix-B^®

(n=608) when measured at 28 weeks. The multi-center study evaluated

2,427 subjects from 11 to 55 years of age in Canada and Germany. Results

of additional analyses from this trial will be presented in the future.

As previously disclosed, the U.S. Food and Drug Administration (FDA)

placed a clinical hold on the two Investigational New Drug (IND)

Applications for HEPLISAV that is still in effect. In issuing the

clinical hold, the FDA requested a review of clinical and preclinical

safety data for HEPLISAV. Additionally, the FDA requested all available

information about a single case of Wegener’s granulomatosis reported in

this Phase 3 trial.

HEPLISAV is based on Dynavax’s proprietary

immunostimulatory sequence (ISS) that specifically targets Toll-Like

Receptor 9 (TLR9) to stimulate an innate immune response. HEPLISAV

combines ISS with HBV surface antigen (HBsAg) and is designed to enhance

the speed of protection.

Webcast Today

Dynavax will webcast a discussion of the HEPLISAV Phase 3 data along

with the company’s second quarter 2008

financial results on Tuesday, August 5, 2008 at 4:30 p.m. Eastern

Daylight Time / 1:30 p.m. Pacific Daylight Time. The webcast can be

accessed on Dynavax’s website at http://investors.dynavax.com/events.cfm.

A telephonic replay of the discussion will be available through August

19, 2008 by dialing 1-888-203-1112, access code: 4643391. International

callers can dial 1-719-457-0820, access code: 4643391.

About Dynavax

Dynavax Technologies Corporation discovers, develops, and intends to

commercialize innovative TLR9 agonist-based products to treat and

prevent infectious diseases, allergy, cancer, and chronic inflammatory

diseases using versatile, proprietary approaches that alter immune

system responses in highly specific ways. Our TLR9 agonists are based on

immunostimulatory sequences, or ISS, which are short DNA sequences that

enhance the ability of the immune system to fight disease and control

chronic inflammation. Our clinical product candidates include: HEPLISAV,

a hepatitis B vaccine partnered with Merck & Co., Inc.; a therapy for

metastatic colorectal cancer; and therapies for hepatitis B and C. Our

preclinical asthma and COPD program is partnered with AstraZeneca. The

NIH partially funds our preclinical universal influenza vaccine program

that is being coordinated with Novartis. Symphony Dynamo Inc. (SDI)

funds our colorectal cancer and hepatitis C therapeutic programs. While

the NIH and SDI provide program support, Dynavax has retained rights to

seek strategic partners for future development and commercialization.

For more information, please visit http://www.dynavax.com.

DYNAVAX Forward-Looking Statement

This press release contains “forward-looking statements.” Actual results

may differ materially from those set forth in this press release due to

the risks and uncertainties inherent in our business, including

difficulties or delays in development, initiation and completion of

clinical trials, the results of clinical trials and the impact of those

results on the initiation and completion of subsequent trials and issues

arising in the regulatory process; achieving our Merck collaborative

agreement objectives and obtaining regulatory approval for HEPLISAV; the

scope and validity of patent protection and the possibility of claims

against us based on the patent rights of others; our ability to obtain

additional financing to support our operations; and other risks detailed

in the “Risk Factors” section of our Quarterly Report on Form 10-Q. We

undertake no obligation to revise or update information herein to

reflect events or circumstances in the future, even if new information

becomes available.

About Merck

Merck & Co., Inc. is a global research-driven pharmaceutical company

dedicated to putting patients first. Established in 1891, Merck

currently discovers, develops, manufactures and markets vaccines and

medicines to address unmet medical needs. The Company devotes extensive

efforts to increase access to medicines through far-reaching programs

that not only donate Merck medicines but help deliver them to the people

who need them. Merck also publishes unbiased health information as a

not-for-profit service. For more information, visit www.merck.com.

Merck Forward-Looking Statement

This press release contains “forward-looking statements” as that term is

defined in the Private Securities Litigation Reform Act of 1995. These

statements are based on management’s current expectations and involve

risks and uncertainties, which may cause results to differ materially

from those set forth in the statements. The forward-looking statements

may include statements regarding product development, product potential

or financial performance. No forward-looking statement can be guaranteed

and actual results may differ materially from those projected. Merck

undertakes no obligation to publicly upda te any forward-looking

statement, whether as a result of new information, future events, or

otherwise. Forward-looking statements in this press release should be

evaluated together with the many uncertainties that affect Merck’s

business, particularly those mentioned in the risk factors and

cautionary statements in Item 1A of Merck’s Form 10-K for the year ended

Dec. 31, 2007, and in any risk factors or cautionary statements

contained in the Company’s periodic reports on Form 10-Q or current

reports on Form 8-K, which the Company incorporates by reference.

(1) Engerix-B^® is a

registered trademark of GlaxoSmith Kline

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