A Phase 2, Randomized, Double-blind, Multi-dose, Dose Finding Study to Evaluate the Safety, Tolerability and Immunogenicity of AFX3772 Compared with PCVs in Healthy Infants

This project is a Phase 2, randomized, double-blind, multi-dose, dose-finding clinical study designed to evaluate AFX3772 compared with currently used pneumococcal conjugate vaccines (PCVs) in healthy infants. The study's principal aims are to assess safety, tolerability and immunogenicity across multiple dose levels in the target population. As a dose-finding effort in Phase 2, the trial seeks to identify one or more dose regimens of AFX3772 that yield acceptable safety and tolerability profiles while eliciting immune responses at least comparable to those produced by established PCVs. The randomized, double-blind design ensures that allocation to study arms is unbiased and that clinical assessments of safety and reactogenicity are conducted without knowledge of treatment assignment, minimizing assessment bias and strengthening the reliability of observed outcomes.

In this study framework, participants are healthy infants who will receive either AFX3772 at varying dose levels or comparator PCVs according to the trial's randomization schema. Safety evaluation will focus on immediate reactogenicity, adverse events, and any medically significant clinical findings following vaccination, with tolerability assessed by solicited and unsolicited symptoms as captured per protocol. Immunogenicity endpoints will measure vaccine-induced immune responses to defined pneumococcal antigens included in AFX3772 and in the comparator PCVs, enabling direct comparison of humoral responses across treatment groups and dose levels. Because the trial is multi-dose, investigators can evaluate both the magnitude and the durability of immune responses after the primary series and any scheduled booster doses, as applicable within the protocol.

The dose-finding nature of the study emphasizes the identification of an optimal balance between immunogenic potency and safety/tolerability. Data emerging from this Phase 2 investigation will inform dose selection for subsequent larger efficacy or registrational trials and will support judgments about whether AFX3772 merits further clinical development relative to existing PCV options. The randomized, double-blind design and inclusion of an active comparator strengthen comparative interpretation, facilitating assessments of whether AFX3772 can achieve non-inferior or superior immunogenicity while maintaining an acceptable safety profile in the sensitive infant population.