1. Study design
A randomized, single-center, active-controlled, double-blind, first-in-human, phase 1 study was conducted to evaluate safety, tolerability, and immunogenicity of a pentavalent meningococcal conjugate vaccine in healthy Korean adults. The study was conducted in accordance with the Good Clinical Practice Guidelines and the principles outlined in the Declaration of Helsinki. The protocols were approved by the Institutional Review Board at Seoul National University Hospital (Seoul, Republic of Korea), and all subjects provided a written consent form before enrolling in the study.
Eligible subjects were randomly assigned in a 1:1 ratio to either the test or reference drug and received a single injection of one of the two study drugs. Due to visual differences between the study drugs, unblinded site staff were designated. Unblinded clinical trial pharmacists filled all study drug into identical-appearing syringes in a secure location. Unblinded vaccinators then administered the allocated drugs to each subject. The unblinded site staff did not participate in any other procedures. After receiving the vaccination, subjects were monitored for 30 minutes for anaphylactic reaction. Clinic visits were scheduled on 7 and 28 days after vaccination, and subjects reported the duration and severity of adverse events that occurred during the period. A follow-up telephone contact was made 180 days after vaccination. During the initial 7 days following vaccination, subjects reported both solicited and unsolicited adverse events. Unsolicited adverse events were recorded through 28 days after vaccination, and serious adverse events were recorded through 180 days after vaccination.
Blood samples for immunological assessment was collected before vaccination and 28 days after vaccination. The 28-day interval was chosen based on the previous study which demonstrated that this timeframe allowed sufficient time for the formation of antibodies8,9.
2. Study drugs
The test drug was EuNmCV-5, a pentavalent meningococcal conjugate vaccine containing serogroups A, C, W-135, X, and Y, and the reference drug was MenACWY-CRM (Menveo®, GlaxoSmithKline, North Carolina, USA), a quadrivalent meningococcal conjugate vaccine containing serogroups A, C, W-135, and Y. The test drug was contained in a single vial with a liquid component comprising 10 μg of meningococcal serogroup A and 5 μg each of serogroup C, W-135, X, and Y. The reference drug was composed of two vials. The first vial contained a powder with 10 μg of meningococcal serogroup A, while the second vial contained liquid component of 5 μg each of serogroup C, W-135, X, and Y. Just before administration of the reference drug, the contents of the first vial were combined with the second vial. Both the test drug and the reference drug had polysaccharides conjugated to recombinant CRM197 protein and were administered as a single dose of 0.5 mL into the deltoid muscle.
3. Study population
A total of 60 healthy Korean male and female subjects, aged 19 to 55, were recruited for this study. A sample size of 60 was deemed appropriate for this first-in-human study to provide a descriptive evaluation of the safety, tolerability, and immunogenicity of the study drugs. This was based on the subject numbers used for a previous phase 1 vaccine study8.
Individuals with a history of meningococcal infection or in contact with a person with meningococcal infection within the last 2 weeks were excluded from the study. Individuals who had received a previous meningococcal vaccination or had been vaccinated with other vaccines within the last 4 weeks were also excluded. Additionally, individuals with any chronic medical conditions, immunodeficiency, or a history of hypersensitivity to any vaccination were excluded from participation. Those who experienced fever (≥ 38°C) within 3 days of screening or had a significant acute or chronic infection within 7 days were excluded. Individuals with positive urine drug screens, positive blood screens for hepatitis B/C, or HIV, clinically significant laboratory abnormalities (including liver function tests), and positive pregnancy tests were also excluded from the study.
4. Safety assessment
Safety and tolerability were assessed by clinical laboratory tests, physical examination, vital signs, monitoring of solicited and unsolicited adverse events. During the initial 7 days following vaccination, subjects reported solicited adverse events. Solicited adverse events included both systemic reactions (fever, headache, fatigue/malaise, nausea, vomiting, myalgia, arthralgia, chill, rash, and acute allergic reaction) and local injection-site reactions (pain, tenderness, erythema/redness, induration/swelling, and urticaria). Erythema/redness or induration/swelling were classified as life-threatening if necrosis occurred, severe if the diameter was ≥10.0 cm, moderate if 5.1-9.9 cm, and mild if ≤5.0 cm. Fever was classified as life-threatening if the temperature was > 40.0°C, severe if 39.0-40.0°C, moderate if 38.5°C-38.9°C, and mild if 38.0°C-38.4°C. Other adverse events were graded as follows: mild (no interference with normal activities), moderate (some interference with normal activities), severe (prevention of normal activities), and life-threatening.
Safety parameters included anaphylactic reaction occurring within 30 minutes post-vaccination, solicited adverse events recorded within 7 days post-vaccination, unsolicited adverse events documented within 28 days post-vaccination, and serious adverse events monitored over a 6-month period following vaccination.
5. Immunogenicity assessment
For the immunogenicity assessment, approximately 20 mL of blood was collected before vaccination (day 0) and day 28, using serum-separating tubes and stored at room temperature for a minimum of 30 minutes to a maximum of 2 hours. Blood samples were centrifuged at 4°C and 1900 g for 20 minutes. Approximately 1.0 mL of supernatant was stored at −70°C until analysis. The serum samples were tested with a rabbit complement-dependent serum bactericidal antibody (rSBA) assay. The Department of Health and Social Care at UK Health Security Agency (UKHSA, London, UK) measured the rSBA titers against five target serogroups A, C, W-135, X, and Y. The target strains in the rSBA assays were serogroup A F8238, serogroup C C11, serogroup Y s1975, serogroup W M01 240070, and serogroup X BF 2/97. The rSBA assay method was adapted as previously published10. The lower limit of quantitation (LLOQ) was set at a titer of four. Antibody titers below LLOQ were considered to be the value of half the LLOQ.
Immunogenicity parameters included the proportion of subjects with seroconversion, defined as individuals who had an increase of at least 4 times rSBA titer at day 28 (for seronegative subjects whose baseline titer is <8, a post-vaccination titer of ≥32; for seropositive subjects whose baseline titer is ≥8, a post-vaccination titer of ≥4 times the baseline titer); the proportion of subjects with seroprotective titers with an rSBA titer of ≥8 and the proportion of subjects with seroprotective titers with ≥128 at day 28; and the geometric mean titers (GMT) for each serogroup at day 28. GMT ratios (GMRs) of the test to the reference drug at day 28 were analyzed. Geometric mean fold increase (GMFI) from baseline and the corresponding geometric mean fold increase ratios (GMFRs) for each serogroup, indicating the ratio between the GMFI in the test drug and that in the reference drug were also presented.
6. Statistical analysis
Safety data were analyzed for the subjects who were administered the study drugs. Solicited and unsolicited adverse events were analyzed by the number and percentage of subjects experiencing each event.
Immunogenicity data were analyzed for the subjects who received the study drugs and for whom post-vaccination immunogenicity data were obtained, regardless of protocol deviations or non-compliance during the study. Immunogenicity parameters of each serogroup were summarized separately based on the treatment. GMTs were calculated by transforming the titers to a logarithmic scale, computing the mean on the transformed scale, then converting the mean value back to the original scale. To assess the differences in GMTs between the two study drugs, 95% confidence intervals (CIs) were computed using the normal approximation method. Additionally, t-tests were conducted on the log2-transformed titers to compare the means. Seroconversion rate and seroprotection of the two study drugs along with their 95% CIs were calculated using the normal approximation method. Seroconversion rate and seroprotection rates were compared between treatment groups using Chi-square test or Fisher’s exact test. Significance was set at p < 0.05 (two-sided). All data analyses and statistical computations were done with SAS® software version 9.4 (SAS Institute, Cary, NC, USA).