Vaxcyte, Inc. announced that the U.S. Food and Drug Administration (FDA) granted Breakthrough Therapy designation for VAX-24, the Company's investigational 24-valent pneumococcal conjugate vaccine (PCV) candidate for the prevention of invasive pneumococcal disease (IPD), in adults. The FDA's decision was based on positive topline results from the Phase 1/2 proof-of-concept study, which evaluated the safety, tolerability and immunogenicity of VAX-24 in adults 18-64 years of age. In the Phase 1/2 clinical study, VAX-24 met the primary safety and tolerability objectives, demonstrating a safety profile similar to Prevnar 20™ (PCV20) for all doses studied.

The study also demonstrated that VAX-24 met or exceeded the established regulatory immunogenicity standards for all 24 serotypes at the conventional 2.2mcg dose, which the Company intends to move forward into a pivotal Phase 3 program. At this dose, VAX-24 met the standard opsonophagocytic activity response non-inferiority criteria for all 20 serotypes common with PCV20, of which 16 achieved higher immune responses. The FDA's Breakthrough Therapy process is designed to expedite the development and review of drugs that are intended to treat a serious or life-threatening condition.

The designation is based upon preliminary clinical evidence indicating that the drug or vaccine may demonstrate substantial improvement over available therapies on one or more clinically significant endpoints. With Breakthrough Therapy designation, Vaxcyte will have access to all of the elements of the FDA's Fast Track program, as well as the ability to receive guidance and support from the FDA on an efficient drug development program and an organizational commitment from senior managers within the FDA. Anticipated Key Milestones Vaxcyte is advancing the clinical development of its PCV and early-stage programs with several anticipated key milestones, including: VAX-24 Adult Program Topline safety, tolerability and immunogenicity data from the Phase 2 study in adults 65 and older are anticipated in the second quarter of 2023.

Final results with the 6-month safety data from the two Phase 2 adult studies are anticipated in the first half of 2023. Following the receipt of the final safety reports from the two adult Phase 2 studies, regulatory interactions to inform the Phase 3 program are anticipated in the second half of 2023. Topline safety, tolerability and immunogenicity data from the pivotal Phase 3 non-inferiority study in adults are expected in 2025.

VAX-24 Pediatric Program The infant Investigational New Drug (IND) application submission and the Phase 2 study initiation are both anticipated in first half of 2023. Topline safety, tolerability and immunogenicity data from the infant Phase 2 study following the primary 3-dose immunization series are expected by 2025. The study design will include a primary immunization series consisting of three doses followed by a subsequent booster dose.

VAX-31 (Formerly VAX-XP) Adult Program The IND application submission for VAX-31 is anticipated in the second half of 2023. Topline safety, tolerability and immunogenicity data from a Phase 1/2 study in adults 18 years of age and older are expected in 2024. VAX-A1 Vaxcyte continues to advance the development of VAX-A1, a novel conjugate vaccine designed to prevent infections caused by Group A Strep bacteria, and further information about the anticipated timing of an IND application will be provided as the program progresses.

VAX-PG Vaxcyte nominated a final vaccine candidate for VAX-PG, its novel therapeutic vaccine designed to treat periodontal disease, in the fourth quarter of 2022 and continues to progress the program.