PowderMed’s therapeutic DNA vaccine for chronic hepatitis B enters phase I clinical trials in patients

The study will primarily evaluate the safety and tolerability of the HBV immunotherapeutic, pdpSC18, administered by PMED™, PowderMed’s needle-free delivery technology, in patients with chronic hepatitis B infection, both in combination with lamivudine and as monotherapy. Additionally, assessments of immunogenicity and clinical response will be made.

Worldwide HBV affects 350 million people and there are no commercially available therapeutic vaccines for the treatment of chronic HBV infection. Chronic infection occurs in 98% of newborn children infected by vertical transmission from the mother (the most common means of transmission in Asia-Pacific), and in 5% of individuals infected after 2 years of age. About 25% of these patients will progress to cirrhosis and 20% of this subgroup will develop hepatocellular carcinoma – one of the most common cancers worldwide.

Welcoming this study and the potential for a novel therapeutic vaccine to HBV, Dr Antonio Bertoletti, of the Center for Molecular Medicine, Singapore, said:

“Patients with chronic hepatitis B show a state of relative hypo-responsiveness of HBV-specific T cells compared with that demonstrated in patients who control the virus replication after acute infection. Therapeutic induction and/or activation of the T-cell response for HBV core and surface proteins may have the potential to control infection. It has been shown that Hepatitis B surface (HBsAg) and core antigen (HBcAg) induces envelope-and core specific CD4+ and CD8+ T-cell responses and that the response against the Hepatitis B core antigen (HBcAg), is often associated with viral control. The combination of these two genes in PowderMed’s pdpSC18 HBV therapeutic DNA vaccine, thus provides a potential mechanism to both clear the virus via the CD8+ response and to overcome unresponsiveness in chronically infected patients via the CD4+ response.”

This Phase I, First Time in Human Study will enrol patients at seven sites in SE Asia (Singapore, Taiwan, Hong Kong) and the USA. Since the immunological response and hepatic tolerability of the hepatitis B immunotherapeutic would be expected to differ considerably between non-infected subjects and subjects with active hepatitis B disease, the Phase I clinical study will enrol subjects with active hepatitis B disease in order to specifically address both safety and immunogenicity in the most predictive manner possible. Each subject will participate in the study for a period of up to 27 weeks, plus a 4-week run-in and screening period. Allowing for the planned safety reviews between dosing cohorts and a 4-month recruitment window, results can be expected during 2007.

Commenting on the trial, Dr John Beadle, PowderMed’s Chief Medical Officer, said:

“Given the limitations of the currently available treatment regimens for chronic Hepatitis B, a regimen, either as a monotherapy or combination, that could provide enhanced clearance of virus, seroconversion, a reduction in resistant strains or a reduction in post-treatment exacerbations of hepatitis would be highly desirable. The concept of a novel DNA therapeutic vaccine to boost the immune response to the virus and promote viral clearance is thus an attractive and timely novel therapeutic strategy in an area of substantial unmet medical need.”

Phase I clinical trials of a prophylactic DNA Vaccine containing only the HBsAg gene (pPWRG7128) in 95 subjects, showed that vaccination via PMED™ was generally well tolerated both locally and systemically, and resulted in seroprotective levels of antibodies and measurable cell-mediated immune responses.