Announcement • 16h
Vaxcyte Doses First Participant In Phase 1 Study Evaluating VAX-A1 For The Prevention Of Disease Caused By Group A Streptococcus In Healthy Adults
Vaxcyte, Inc. announced that the first participant was dosed in the Phase 1, first-in-human study evaluating VAX-A1, the Company’s investigational prophylactic vaccine candidate for the prevention of disease caused by Group A Streptococcus (Group A Strep), in healthy adults aged 18 to 40 years. The Company expects to announce topline data from the study in the second half of 2027. The primary objective of this randomized, double-blind, placebo-controlled, dose-escalation, two-stage study is assessing the safety and tolerability of VAX-A1, along with a secondary objective of evaluating initial immunogenicity data, to support potential further advancement. The Stage 1 portion of the study is evaluating three dose levels (Low, Mid and High) compared to placebo in approximately 12 adults in a controlled, staged enrollment and dose-escalation approach. Following completion of the Stage 1 Month 1 visit, an independent Data Safety Monitoring Board (DSMB) will review unblinded safety and tolerability data. Upon DSMB approval, the Stage 2 portion of the study is expected to proceed and evaluate the same three dose levels compared to placebo in approximately 68 adults. All participants in the study will be evaluated for safety through six months following the second dose. Group A Strep is responsible for approximately 800 million new cases of illness and more than 600,000 deaths annually worldwide, with no approved vaccine and significant public health burden. About the VAX-A1 Adult Phase 1 Study: This randomized, double-blind, placebo-controlled, two-stage, dose-escalation clinical study is evaluating VAX-A1 in approximately 80 healthy adults aged 18 to 40 years. Stage 1 of the study will enroll approximately 12 participants to evaluate VAX-A1 at three dose levels (Low, Mid and High), in a controlled, staged enrollment and dose-escalation approach. Dose escalation for each cohort in Stage 1 will be based on a review of blinded safety and tolerability data by the Company’s Internal Safety Team prior to proceeding with enrolling the next cohort. Following completion of the Stage 1 Month 1 visit, an independent DSMB will review unblinded safety and tolerability data. Upon DSMB approval, Stage 2 is expected to proceed and enroll approximately 68 participants to further evaluate VAX-A1 across the same three dose levels. The study is being conducted at an investigative site in Australia, where Group A Strep has been especially problematic and where there are experienced investigator networks with expertise in Group A Strep. Participant Overview: Stage 1 (n=12): Participants will be randomized 3:1 to receive VAX-A1 or placebo across three dose levels (Low, Mid and High). Stage 2 (n=68): Participants will be randomized 1:1:1:1 to receive VAX-A1 at one of the three dose levels or placebo. All participants are expected to receive two doses administered approximately two months apart. Safety and Immunogenicity Assessments: Primary objectives include evaluation of safety and tolerability, including assessment of solicited and unsolicited adverse events, serious adverse events and adverse events of special interest. Secondary objectives include evaluation of antigen-specific immune responses to Group A Strep antigens, including serum immunoglobulin G (IgG) responses to C5a peptidase (ScpA), streptolysin O (SLO), S. pyogenes adhesion and division protein (SpyAD) and a universal polysaccharide (modified Group A carbohydrate or GACPR). Safety and tolerability will be assessed for approximately six months following the second and final vaccination. About Group A Strep: Group A Strep is one of the leading causes of bacterial infections worldwide, responsible for a broad spectrum of disease ranging from common illnesses such as strep throat and skin infections to severe invasive disease, including necrotizing fasciitis and streptococcal toxic shock syndrome, as well as immune-mediated sequelae such as acute rheumatic fever, rheumatic heart disease and post-streptococcal glomerulonephritis, a form of kidney inflammation. With an estimated 800 million new cases of illness and more than 600,000 deaths annually worldwide, Group A Strep remains a major clinical burden. The economic impact is substantial, exceeding an estimated $6 billion annually in the U.S. alone. The public health challenge associated with Group A Strep is compounded by evolving epidemiology, including increasing rates of invasive disease and the re-emergence of certain manifestations in markets with historically lower disease burden. Group A Strep also drives significant antibiotic use, especially among children, contributing to rising resistance to multiple antibiotic classes. As a result, Group A Strep contributes to the global threat of antimicrobial resistance (AMR), reinforcing the need for preventative approaches such as vaccination. About VAX-A1: VAX-A1 is a prophylactic vaccine candidate designed to provide broad protection against Group A Strep by targeting conserved antigens associated with immune evasion and virulence. The candidate incorporates three protein antigens, including C5a peptidase (ScpA), streptolysin O (SLO) and S. pyogenes adhesion and division protein (SpyAD), as well as a modified Group A carbohydrate (GACPR) designed to remove potentially cross-reactive epitopes historically associated with autoimmune complications. VAX-A1 is being developed using Vaxcyte’s cell-free protein synthesis platform, which enables precise antigen design and site-specific conjugation intended to preserve immunogenicity while avoiding problematic regions. The vaccine is designed to induce functional immune responses against conserved structures of the pathogen and disarm its defense mechanisms, providing broad, strain-independent protection. This approach is intended to address limitations of prior vaccine strategies, including antigen variability and concerns regarding autoimmune cross-reactivity.
