A Phase II, Randomized, Safety and Immunogenicity Study of a Re-Derived, Live-Attenuated Dengue Virus Vaccine in Healthy Adults

Stephen J. Thomas 0 1 Kenneth H. Eckels 0 1 Isabelle Carletti 0 1 Rafael De La Barrera 0 1 Francis Dessy 0 1 Stefan Fernandez 0 1 Robert Putnak 0 1 Jean-Francois Toussaint 0 1 Wellington Sun 0 1 Kristen Bauer 0 1 Robert V. Gibbons 0 1 Bruce L. Innis 0 1 0 Walter Reed Army Institute of Research , 503 Robert Grant Ave., Silver Spring, MD 20910 1 Viral Diseases Branch, Walter Reed Army Institute of Research, Silver Spring, Maryland; Division of Regulated Activities, Pilot Bioproduction Facility, Walter Reed Army Institute of Research , Silver Spring, Maryland; GlaxoSmithKline Vaccines, Wavre , Belgium; United States Army Medical Component-Armed Forces Research Institute for Medical Sciences , Bangkok , Thailand; GlaxoSmithKline Vaccines, King of Prussia , Pennsylvania Two formulations of a new live tetravalent dengue virus (DENV) vaccine produced using re-derived master seeds from a precursor vaccine and that same precursor vaccine as a control were compared in a placebocontrolled, randomized, observer-blind, phase II trial of 86 healthy adults. Two vaccine doses were administered 6 months apart; a third dose was offered to a subset. Symptoms and signs of dengue-like illness reported after vaccination were mild to moderate, transient, and occurred with similar frequency among recipients of the new DENV vaccine and placebo, except for rash. Neither dengue nor vaccine-related serious adverse events were reported. The first DENV vaccine dose was moderately immunogenic; the second dose increased the potency and breadth of the neutralizing antibody response. Tetravalent response rates to the new formulations were 60% and 66.7% in unprimed subjects. A third dose did not increase tetravalent antibody rates. The new DENV vaccine candidates merit additional evaluation. - INTRODUCTION Dengue, one of the worlds most prevalent and important arboviral diseases, occurs after infection by any of four antigenically distinct but serologically related dengue virus (DENV) types (DENV-1, DENV-2, DENV-3, and DENV-4). An estimated 3.6 billion people live at risk of infection in more than 120 dengue-endemic countries. Approximately 70500 million infections occur annually, resulting in over 2 million severe illnesses.1 Vaccination against DENV in conjunction with strategic vector control is considered to be the most viable longterm option for reducing the global dengue burden.25 The Walter Reed Army Institute of Research (WRAIR) in collaboration with GlaxoSmithKline Vaccines (GSK) developed a live-attenuated tetravalent dengue virus vaccine candidate comprised of four live virus strains representing each of the four DENV types attenuated by serial passage in primary dog kidney (PDK) cells.6,7 A safe, well-tolerated, and immunogenic preparation of the vaccine candidate was identified in a phase II trial conducted in the United States in adult subjects.8 The vaccine candidate was then evaluated in two phase I/II clinical trials of flavivirus-nave children in Thailand who were administered two doses 6 months apart. The first trial was an open-label study of seven seronegative children, and the second trial was a randomized study of 51 seronegative infants from 12 to 15 months of age.9,10 The vaccine safety profile was clinically acceptable in both studies. Immune responses to all four DENV types were reported in more than one-half of the infants and all of the children 1 month after the second dose. All of the above trials used lyophilized monovalent vaccines that were combined into a tetravalent preparation at the time of administration. Herein, we report the first clinical evaluation of a new WRAIR-GSK live-attenuated DENV candidate vaccine. The new candidate was prepared from re-derived vaccine strains using the same manufacturing process, except that each strain has three additional passages in fetal rhesus lung (FRhL) cells, monovalent bulks were formulated with a carbohydrate stabilizer rather than human serum albumin, and the final vaccine was lyophilized as a tetravalent product. MATERIALS AND METHODS Study design. This study was a phase II, randomized, singlecenter, observer-blind, controlled, parallel-group trial conducted in the United States. The study was designed to evaluate the safety and immunogenicity of two formulations of a new live-attenuated tetravalent DENV vaccine compared with a precursor live-attenuated tetravalent DENV vaccine and a cell culture medium placebo. The study was conducted in two stages. The first stage was an observer-blind evaluation of the above four treatment groups followed for 6 months after administration of a first vaccine dose and 3 months after administration of a second vaccine dose. Subjects were randomly allocated to treatment groups using a 1:1:1:1 ratio. The randomization was performed at GlaxoSmithKline Vaccines, Rixensart, Belgium, using a standard Statistical Analysis System (SAS) program (SAS Institute Inc., Cary, NC). During this first stage, although the vaccine preparer/ administrator was aware of some treatment assignments because of a unique method for preparation of the precursor vaccine (monovalent vials mixed into a tetravalent mixture), no volunteer or investigator was aware of treatment assignments until data collection was completed and the first-stage database was frozen for analysis. The second stage was an open-label evaluation of a subset of subjects in the two new vaccine treatment groups who consented to receive a third dose of the same formulation used for their primary immunization. The third dose was given 512 months after the second dose. The institutional review board, US Army Human Subjects Research Review Board, Office of the Surgeon General approved the study protocol and supporting documents. The study was conducted between April of 2006 and March of 2008 in accordance with the provisions of the Declaration of Helsinki, Good Clinical Practices, and US regulations. The US Army Medical Materiel Development Activity (USAMMDA) and GSK monitored the conduct of the trial and verified the data. Internal audits by separate teams from the US Army and GSK were also conducted. Written informed consent was obtained from each volunteer before the performance of any study procedures. Role of the sponsor and development partners. The study was designed by the US Army and GSK. The USAMMDA, as the sponsors representative, monitored and reported on subject safety. Investigators collected and encoded the data into a GSK database, and a GSK statistician analyzed the data according to a pre-specified and mutually approved plan. All authors had complete and unfettered access to the data, reviewed the manuscript, and can vouch for the documents accuracy and completeness. The study was jointly funded by the US Army Medical Research and Materiel Command and GSK. Vaccines. In this trial, two different formulations of a new live-attenuated tetravalent DENV vaccine designated TDEN (formulations F17 and F19) were compared with (...truncated)