Jeffrey D. Chulay

Atovaquone-Proguanil versus Mefloquine for Malaria Prophylaxis in Nonimmune Travelers: Results from a Randomized, Double-Blind Study

Concerns about the tolerability of mefloquine highlight the need for new drugs to prevent malaria. Atovaquone-proguanil (Malarone; GlaxoSmithKline) was safe and effective for prevention of falciparum malaria in lifelong residents of malaria-endemic countries, but experience in nonimmune people is limited. In a randomized, double-blind study, nonimmune travelers received malaria prophylaxis with atovaquone-proguanil (493 subjects) or mefloquine (483 subjects). Information about adverse events (AEs) and potential episodes of malaria was obtained 7, 28, and 60 days after travel. AEs were reported by an equivalent proportion of subjects who had received atovaquone-proguanil or mefloquine (71.4% versus 67.3%; difference, 4.1%; 95% confidence interval, -1.71 to 9.9). Subjects who received atovaquone-proguanil had fewer treatment-related neuropsychiatric AEs (14% versus 29%; P=.001), fewer AEs of moderate or severe intensity (10% versus 19%; P=.001), and fewer AEs that caused prophylaxis to be discontinued (1.2% versus 5.0%; P=.001), compared with subjects who received melfoquine. No confirmed diagnoses of malaria occurred in either group. Atovaquone-proguanil was better tolerated than was mefloquine, and it was similarly effective for malaria prophylaxis in nonimmune travelers.

Randomized, double-blind, Phase 1 trial of an alphavirus replicon vaccine for cytomegalovirus in CMV seronegative adult volunteers.

Development of a cytomegalovirus (CMV) vaccine is a priority. We evaluated a two component alphavirus replicon particle vaccine expressing CMV gB or a pp65/IE1 fusion protein, previously shown to induce robust antibody and cellular immune responses in mice, in a randomized, double-blind Phase 1 clinical trial in CMV seronegative subjects. Forty subjects received a lower dose (LD) or higher dose (HD) of vaccine or placebo by intramuscular or subcutaneous injection at Weeks 0, 8 and 24. The vaccine was well tolerated, with mild to moderate local reactogenicity, minimal systemic reactogenicity, and no clinically important changes in laboratory parameters. All vaccine recipients developed ex vivo, direct IFN-gamma ELISPOT responses to CMV antigens (maximal mean spot-forming cells per 10(6) PBMC in LD and HD groups of 348 and 504 for pp65, 83 and 113 for IE1, and 138 and 114 for gB), and neutralizing antibodies (maximal geometric mean titer 110 with LD and 218 with HD). Polyfunctional CD4(+) and CD8(+) T cell responses were detected by polychromatic flow cytometry. This alphavirus replicon particle vaccine was safe and induced neutralizing antibody and multifunctional T cell responses against three CMV antigens that are important targets for protective immunity.

Atovaquone-proguanil versus chloroquine-proguanil for malaria prophylaxis in non-immune travellers: a randomised, double-blind study

BACKGROUNDnChloroquine plus proguanil is widely used for malaria chemoprophylaxis despite low effectiveness in areas where multidrug-resistant malaria occurs. Studies have shown that atovaquone and proguanil hydrochloride is safe and effective for prevention of falciparum malaria in lifelong residents of malaria-endemic countries, but little is known about non-immune travellers.nnnMETHODSnIn a double-blind equivalence trial, 1083 participants travelling to a malaria-endemic area were randomly assigned to two treatment groups: atovaquone-proguanil plus placebos for chloroquine and proguanil, or chloroquine, proguanil, and placebo for atovaquone-proguanil. Follow-up was by telephone 7 and 60 days after travel and at a clinic at 28 days. Serum samples were tested for antibodies to a malaria circumsporozoite protein. Blood and serum samples of participants with a potential malaria diagnosis were tested in a reference laboratory.nnnFINDINGSn7 days after travel, at least one adverse event was reported by 311 (61%) of 511 participants who received atovaquone-proguanil and 329 (64%) of 511 who received chloroquine-proguanil. People receiving atovaquone-proguanil had a lower frequency of treatment-related gastrointestinal adverse events (59 [12%] vs 100 [20%], p=0.001), and of treatment-related adverse events of moderate or severe intensity (37 [7%] vs 56 [11%], p=0.05). There were fewer treatment-related adverse events that caused prophylaxis to be discontinued in the atovaquone-proguanil group than in the chloroquine-proguanil group (one [0.2%] vs ten [2%], p=0.015).nnnINTERPRETATIONnOverall the two preparations were similarly tolerated. However, significantly fewer adverse gastrointestinal events were observed in the atovaquone-proguanil group in than in the chloroquine-proguanil group.

Randomized, Placebo-Controlled Trial of Atovaquone/Proguanil for the Prevention of Plasmodium falciparum or Plasmodium vivax Malaria among Migrants to Papua, Indonesia

The increasing prevalence of resistance to antimalarial drugs reduces options for malaria prophylaxis. Atovaquone/proguanil (Malarone; GlaxoSmithKline) has been >95% effective in preventing Plasmodium falciparum malaria in lifelong residents of areas of holoendemicity, but data from persons without clinical immunity or who are at risk for Plasmodium vivax malaria have not been described. We conducted a randomized, double-blinded study involving 297 people from areas of nonendemicity in Indonesia who migrated to Papua (where malaria is endemic) < or =26 months before the study period. Subjects received prophylaxis with 1 Malarone tablet (250 mg of atovaquone and 100 mg of proguanil hydrochloride; n=148) or placebo (n=149) per day for 20 weeks. Hematologic and clinical chemistry values did not change significantly. The protective efficacy of atovaquone/proguanil was 84% (95% confidence interval [CI], 44%-95%) for P. vivax malaria, 96% (95% CI, 72%-99%) for P. falciparum malaria, and 93% (95% CI, 77%-98%) overall. Atovaquone/proguanil was well tolerated, safe, and effective for the prevention of drug-resistant P. vivax and P. falciparum malaria in individuals without prior malaria exposure who migrated to Papua, Indonesia.

Preconceptual Administration of an Alphavirus Replicon UL83 (pp65 Homolog) Vaccine Induces Humoral and Cellular Immunity and Improves Pregnancy Outcome in the Guinea Pig Model of Congenital Cytomegalovirus Infection

Development of a vaccine against congenital cytomegalovirus (CMV) infection is a major public health priority. We report the use of a propagation-defective, single-cycle, RNA replicon vector system, derived from an attenuated strain of the alphavirus Venezuelan equine encephalitis virus, to produce virus-like replicon particles (VRPs) expressing GP83, the guinea pig CMV (GPCMV) homolog of the human CMV pp65 phosphoprotein. Vaccination with VRP-GP83 induced antibodies and CD4(+) and CD8(+) T cell responses in GPCMV-seronegative female guinea pigs. Guinea pigs immunized with VRP-GP83 vaccine or with a VRP vaccine expressing influenza hemagglutinin (VRP-HA) were bred for pregnancy and subsequent GPCMV challenge during the early third trimester. Dams vaccinated with VRP-GP83 had improved pregnancy outcomes, compared with dams vaccinated with the VRP-HA control. For VRP-GP83-vaccinated dams, there were 28 live pups and 4 dead pups (13% mortality) among 10 evaluable litters, compared with 9 live pups and 12 dead pups (57% mortality) among 8 evaluable litters in the VRP-HA-vaccinated group (P<.001, Fishers exact test). Improved pregnancy outcome was accompanied by reductions in maternal blood viral load, measured by real-time polymerase chain reaction. These results indicate that cell-mediated immune responses directed against a CMV matrix protein can protect against congenital CMV infection and disease.

Causal prophylactic efficacy of atovaquone-proguanil (MalaroneTM) in a human challenge model

Plasmodia infect the liver for about 7 days before subsequently infecting the blood. Present prophylaxis against Plasmodium falciparum malaria employs agents that primarily kill blood stages and must be continued for 28 days after the last exposure. Atovaquone-proguanil (Malarone) is a new antimalarial agent that is licensed in 35 countries as treatment against blood-stage infection, but its components (atovaquone and proguanil) have separately been shown to be active also against liver stages. To determine whether atovaquone-proguanil is sufficiently active against liver stages to be discontinued 7 days after exposure, we challenged 16 volunteers with P. falciparum via infected mosquitoes. Twelve volunteers received atovaquone-proguanil (1 tablet daily) on the day prior to challenge, on the day of challenge, and for the next 6 days; 4 volunteers received matching placebo. All placebo volunteers demonstrated parasitaemia and malarial symptoms beginning on days 11-12 after challenge. No atovaquone-proguanil volunteer acquired malaria. Atovaquone-proguanil is the first licensed antimalarial agent that kills P. falciparum in the liver and that may be discontinued 7 days after the last exposure.

Atovaquone and proguanil hydrochloride followed by primaquine for treatment of Plasmodium vivax malaria in Thailand

Chloroquine-resistant Plasmodium vivax malaria has been reported in several geographical areas. The P. vivax life-cycle includes dormant hepatic parasites (hypnozoites) that cause relapsing malaria weeks to years after initial infection. Curative therapy must therefore target both the erythrocytic and hepatic stages of infection. Between July 1997 and June 1998, we conducted an open-label study in Thailand to evaluate the efficacy and tolerability of a sequential regimen of combination atovaquone (1000 mg) and proguanil hydrochloride (400 mg), once daily for 3 days, followed by primaquine (30 mg daily for 14 days) for treatment of vivax malaria. All 46 patients who completed the 3-day course of atovaquone-proguanil cleared their parasitaemia within 2-6 days. During a 12-week follow-up period in 35 patients, recurrent parasitaemia occurred in 2. Both recurrent episodes occurred 8 weeks after the start of therapy, consistent with relapse from persistent hypnozoites rather than recrudescence of persistent blood-stage parasites. The dosing regimen was well tolerated. Results of this trial indicate that atovaquone-proguanil followed by primaquine is safe and effective for treatment of vivax malaria.

Cellular and Humoral Immune Responses to Alphavirus Replicon Vaccines Expressing Cytomegalovirus pp65, IE1, and gB Proteins

ABSTRACT Development of vaccines against cytomegalovirus (CMV) is an important public health priority. We used a propagation-defective, single-cycle RNA replicon vector system derived from an attenuated strain of an alphavirus, Venezuelan equine encephalitis virus, to produce virus-like replicon particles (VRP) expressing various combinations of pp65, IE1, or gB proteins of human CMV. Protein expression in VRP-infected cells was highest with single-promoter replicons expressing pp65, IE1, a pp65/IE1 fusion protein, or the extracellular domain of gB and with double-promoter replicons expressing pp65 and IE1. Protein expression was lower with double- and triple-promoter replicons expressing gB, especially the full-length form of gB. BALB/c mice immunized with VRP expressing gB developed high titers of neutralizing antibody to CMV, and mice immunized with VRP expressing pp65, IE1, or a pp65/IE1 fusion protein developed robust antigen-specific T-cell responses as measured by gamma interferon enzyme-linked immunospot assay. Three overlapping immunodominant pp65 peptides contained a nine-amino-acid sequence (LGPISGHVL) that matches the consensus binding motif for a major histocompatibility complex H2-Dd T-cell epitope. These data provide the basis for further development and clinical evaluation of an alphavirus replicon vaccine for CMV expressing the pp65, IE1, and gB proteins.

Atovaquone/Proguanil Therapy for Plasmodium falciparum and Plasmodium vivax Malaria in Indonesians Who Lack Clinical Immunity

Thirty-eight of 295 subjects participating in a randomized, double-blind, placebo-controlled trial of the efficacy of daily administration of atovaquone/proguanil for malaria prevention developed malaria at some time during the 20-week prophylaxis period. These subjects (3 atovaquone/proguanil recipients and 35 placebo recipients) were treated with 4 tablets of atovaquone/proguanil per day for 3 days. Atovaquone/proguanil provided safe, well-tolerated, and effective therapy for uncomplicated malaria in nonimmune Indonesians.

Phase I Safety and Immunogenicity Evaluations of an Alphavirus Replicon HIV-1 Subtype C gag Vaccine in Healthy HIV-1-Uninfected Adults

ABSTRACT On the basis of positive preclinical data, we evaluated the safety and immunogenicity of an alphavirus replicon HIV-1 subtype C gag vaccine (AVX101), expressing a nonmyristoylated form of Gag, in two double-blind, randomized, placebo-controlled clinical trials in healthy HIV-1-uninfected adults. Escalating doses of AVX101 or placebo were administered subcutaneously to participants in the United States and Southern Africa. Because of vaccine stability issues, the first trial was halted prior to completion of all dose levels and a second trial was implemented. The second trial was also stopped prematurely due to documentation issues with the contract manufacturer. Safety and immunogenicity were evaluated through assessments of reactogenicity, reports of adverse events, and assessment of replication-competent and Venezuelan equine encephalitis (VEE) viremia. Immunogenicity was measured using the following assays: enzyme-linked immunosorbent assay (ELISA), chromium 51 (51Cr)-release cytotoxic T lymphocyte (CTL), gamma interferon (IFN-γ) ELISpot, intracellular cytokine staining (ICS), and lymphoproliferation assay (LPA). Anti-vector antibodies were also measured. AVX101 was well tolerated and exhibited only modest local reactogenicity. There were 5 serious adverse events reported during the trials; none were considered related to the study vaccine. In contrast to the preclinical data, immune responses in humans were limited. Only low levels of binding antibodies and T-cell responses were seen at the highest doses. This trial also highlighted the difficulties in developing a novel vector for HIV.