Phase 1 Randomized Study of a Tetravalent Dengue Purified Inactivated Vaccine in Healthy Adults in the United States

Abstract

AbstractThe safety and immunogenicity of four formulations of an investigational tetravalent dengue purified inactivated vaccine (DPIV), formulated at 1 or 4 μg with aluminum hydroxide (alum) or at 1 μg with an adjuvant system (AS01_E or AS03_B), were evaluated in a first-time-in-human, placebo-controlled, randomized, observer-blind, phase 1 trial in the continental United States. Two doses of vaccine or placebo were administered intramuscularly 4 weeks apart to 100 healthy adults 18-39 years of age, randomized 1:1:1:1:1 to receive one of four DPIV formulations or saline placebo. The response to a third dose was evaluated in a subset of nine participants remote from primary vaccination. Humoral immunogenicity was assessed using a 50% microneutralization assay. All DPIV formulations were well tolerated. No vaccine-related serious adverse events were observed through 12 months after the second vaccine dose. In all DPIV groups, geometric mean antibody titers peaked at Day 56, waned through 6 months after the second vaccine dose, and then stabilized. In the nine subjects where boosting was evaluated, a strong anamnestic response was observed. These results support continuation of the clinical development of this dengue vaccine candidate (clinicaltrials.gov: NCT01666652).

Figure 1.

Disposition of study participants and reasons for exclusion from according-to-protocol cohort for immunogenicity. 1 μg + alum indicates participants who received 1 μg/serotype/dose adjuvanted with alum; 4 μg + alum indicates participants who received 4 μg/serotype/dose adjuvanted with alum; 1 μg + AS01_E indicates participants who received 1 μg/serotype/dose adjuvanted with AS01_E; 1 μg + AS03_B indicates participants who received 1 μg/serotype/dose adjuvanted with AS03_B. N = number of participants; ATP = according-to-protocol; Ab = antibody. D56 = Day 56, (1 month post-dose 2); M7 = Month 7 (6 months post-dose 2); M13 = Month 13 (12 months post-dose 2). Dashed arrows were used between the different ATP cohorts for immunogenicity to show chronological order (D56, M7, M13), but a cohort is not embedded in the preceding one.

Figure 2.

Overall per dose incidence of any grade solicited injection site (A) and general (B) adverse events during the 7-day postvaccination period (total vaccinated cohort). 1 μg + alum indicates participants who received 1 μg/serotype/dose adjuvanted with alum; 4 μg + alum indicates participants who received 4 μg/serotype/dose adjuvanted with alum; 1 μg + AS01_E indicates participants who received 1 μg/serotype/dose adjuvanted with AS01_E; 1 μg + AS03_B indicates participants who received 1 μg/serotype/dose adjuvanted with AS03_B. Error bars indicate exact 95% confidence intervals; GI = gastrointestinal; Temperature = oral temperature ≥ 37.5°C. Intensities of each AE were scored as grades 1–3, with grade 3 fever defined as an oral body temperature ≥ 39°C, grade 3 redness and swelling defined as ≥ 101-mm diameter around the injection site, and all other grade 3 AEs defined as those events preventing normal daily activity.

Figure 3.

Geometric mean titers to dengue virus types 1–4 up to 1 year post-dose 2 (according-to-protocol cohort for immunogenicity M13). 1 μg + alum indicates participants who received 1 μg/serotype/dose adjuvanted with alum; 4 μg + alum indicates participants who received 4 μg/serotype/dose adjuvanted with alum; 1 μg + AS01_E indicates participants who received 1 μg/serotype/dose adjuvanted with AS01_E; 1 μg + AS03_B indicates participants who received 1 μg/serotype/dose adjuvanted with AS03_B. Participants with a titer below the assay cutoff of 10 were attributed a titer of 5; DENV = dengue virus type; PRE = prevaccination; D56 = Day 56 (1 month post-dose 2); M4 = Month 4 (3 months post-dose 2); M7 = Month 7 (6 months post-dose 2); M13 = Month 13 (12 months post-dose 2). Error bars indicate 95% confidence intervals.

Figure 4.

Reverse cumulative distribution curves for antibody titers to dengue virus types 1–4 at D56 (according-to-protocol cohort for immunogenicity D56). 1 μg + alum indicates participants who received 1 μg/serotype/dose adjuvanted with alum; 4 μg + alum indicates participants who received 4 μg/serotype/dose adjuvanted with alum; 1 μg + AS01_E indicates participants who received 1 μg/serotype/dose adjuvanted with AS01_E; 1 μg + AS03_B indicates participants who received 1 μg/serotype/dose adjuvanted with AS03_B. Dotted line indicates cutoff for MN50 = 10 ED₅₀; participants with a titer below the assay cutoff were attributed the arbitrary value of half the cutoff. MN50 = 50% microneutralization assay; DENV = dengue virus type.

Figure 5.

Seroconversion rates to dengue virus types 1–4 up to 1 year post-dose 2 (according-to-protocol cohort for immunogenicity M13). 1 μg + alum indicates participants who received 1 μg/serotype/dose adjuvanted with alum; 4 μg + alum indicates participants who received 4 μg/serotype/dose adjuvanted with alum; 1 μg + AS01_E indicates participants who received 1 μg/serotype/dose adjuvanted with AS01_E; 1 μg + AS03_B indicates participants who received 1 μg/serotype/dose adjuvanted with AS03_B. Monovalent, bivalent, trivalent, and tetravalent seropositivity rates are defined as the percentage of subjects who are seropositive to 1, 2, 3, and all 4 DENV types, respectively. No seroconversion was observed in the placebo group, which was therefore not shown. Not all numbers add up to 100% due to rounding. D56 = Day 56 (1 month post-dose 2); M7 = Month 7 (6 months post-dose 2); M13 = Month 13 (12 months post-dose 2).

Figure 6.

Box and whisker plot of avidity index for dengue virus types 1–4 up to 1 year post-dose 2 (adapted according-to-protocol cohort for immunogenicity). 1 μg + alum indicates participants who received 1 μg/serotype/dose adjuvanted with alum; 4 μg + alum indicates participants who received 4 μg/serotype/dose adjuvanted with alum; 1 μg + AS01_E indicates participants who received 1 μg/serotype/dose adjuvanted with AS01_E; 1 μg + AS03_B indicates participants who received 1 μg/serotype/dose adjuvanted with AS03_B. DENV = dengue virus type; PRE = prevaccination; D28 = Day 28 (1 month post-dose 1); D56 = Day 56 (1 month post-dose 2); M7 = Month 7 (6 months post-dose 2); M13 = Month 13 (12 months post-dose 2). According to the time point, the following cohorts were used to create the adapted according-to-protocol cohort for immunogenicity: for PRE, D28, D56: ATP cohort for immunogenicity D56; for M7: ATP cohort for immunogenicity M7 and for M13: ATP cohort for immunogenicity M13. Antibody avidity indices describe polyclonal antibody binding in the absence or presence of 8 M urea, as described in the Materials and Methods section. Boxes and/or whiskers with limits equal to 0 are flattened to a horizontal bar.

Figure 7.

Avidity index vs. the N antibody titers by MN50 for dengue virus serotypes 1–4 at D56 (adapted according-to-protocol cohort for immunogenicity). 1 μg + alum indicates participants who received 1 μg/serotype/dose adjuvanted with alum; 4 μg + alum indicates participants who received 4 μg/serotype/dose adjuvanted with alum; 1 μg + AS01_E indicates participants who received 1 μg/serotype/dose adjuvanted with AS01_E; 1 μg + AS03_B indicates participants who received 1 μg/serotype/dose adjuvanted with AS03_B. DENV = dengue virus serotype; D56 = Day 56 (1 month post-dose 2); Loess = nonparametric local regression fit. According to the time point, the following cohorts were used to create the adapted according-to-protocol cohort for immunogenicity D56: for PRE, D28, D56: ATP cohort for immunogenicity; for M7: ATP cohort for immunogenicity M7 and for M13: ATP cohort for immunogenicity M13.

Figure 8.

Neutralizing antibody titers to dengue virus serotypes 1–4 up to 28 days postbooster (booster according-to-protocol cohort for immunogenicity). 4 μg + alum indicates participants who received 4 μg/serotype/dose adjuvanted with alum; 1 μg + AS01_E indicates participants who received 1 μg/serotype/dose adjuvanted with AS01_E. Participants with a titer below the assay cutoff were attributed the arbitrary value of half the cutoff; DENV = dengue virus serotype; PRE = prevaccination; D56 = Day 56 (1 month post-dose 2); M7 = Month 7 (6 months post-dose 2); M13 = Month 13 (12 months post-dose 2); Pre-B = prebooster vaccination, Post-B = 28 days postbooster vaccination.