A Safety and Immunogenicity Trial of Boost-2867 Vaccine, Via Intranasal and Intramuscular Routes

This phase 1 clinical trial will evaluate the safety, reactogenicity, and immunogenicity of Boost-2867, given intramuscular (IM) with or without adjuvant or intranasal (IN) without adjuvant, as a booster dose to previously vaccinated healthy adults. Each of the study sites will be assigned to enroll either only participants who will receive IM administration (up to 5 sites) or only participants who will receive IN administration (up to 5 sites); no site will administer both IM and IN study product administrations. Within the IM and IN Arms the cohorts will be sequentially enrolled. The study is designed as a non-randomized, open-label, dose-escalation clinical trial evaluating one dose level of Boost-2867 without adjuvant administered IM, three dose levels of Boost-2867 with adjuvant administered IM, and three dose levels of Boost-2867 without adjuvant administered IN. A sample size of 140 participants (20 participants per dose cohort) is anticipated. To evaluate for early safety signals for this first-in-human trial, study product administration of participants enrolled for IM administration and those enrolled for IN administration will proceed in a staged fashion. For Cohorts 1 (IM administration without adjuvant) and 5 (IN administration), which may be enrolled and dosed concurrently, 3 sentinel participants under 50 years of age will be enrolled in each Cohort over at least 2 days. For each of those Cohorts independently, a safety review of halting rules and clinical safety data through at least Day 8 will be conducted by the Protocol Safety Review Team (PSRT) prior to enrollment of the remainder of the cohort. Enrollment, dosing, and safety oversight for IM Cohorts 2, 3, and 4 will proceed in the same fashion as Cohort 1, except that sentinel enrollment need not be spaced over at least 2 days. Similarly, for IN Cohorts 6 and 7, enrollment and safety oversight will proceed in the same fashion as Cohort 5, except that sentinel enrollment need not be spaced over at least 2 days. The primary objectives are: 1) To evaluate the safety and reactogenicity of a single IM injection of three different antigen dose levels (5, 15, and 50 microgram) of Boost-2867 with Alhydrogel (R) (alum) and CpG 7909 adjuvants, and a single injection of 50 microgram Boost-2867 without adjuvant, in previously vaccinated healthy adults. 2) To evaluate the safety and reactogenicity of a single IN administration of three different antigen dose levels (20, 50, and 125 microgram) of Boost-2867 without adjuvant in previously vaccinated healthy adults. The secondary objectives are: 1) To evaluate the systemic anti-Spike humoral immune responses of a single IM or IN administration of Boost-2867. 2) To evaluate nasal mucosal immunoglobulin A (IgA) and immunoglobulin G (IgG) responses after IM and IN administration.