Affinivax Announces the Presentation of Phase 1 Clinical Data for its MAPS Vaccine for Streptococcus pneumoniae at IDWeek 2020

Novel pneumococcal vaccine with unprecedented 24 serotypeswas safe, well tolerated, and highly immunogenic

CAMBRIDGE, Mass., October 21, 2020Affinivax, Inc. (“Affinivax”), a clinical stage biotechnology company with its novel MAPS technology platform for vaccines and immunotherapies, today announced the presentation of initial data from a Phase 1/2 clinical trial of its lead vaccine candidate targeting Streptococcus pneumoniae (ASP3772, partnered with Astellas Pharma Inc.). Developed using Affinivax’s proprietary MAPS (multiple antigen-presenting system) technology, ASP3772 includes 24 pneumococcal serotypes, more than any other pneumococcal vaccine on the market or in clinical testing today, as well as two novel conserved pneumococcal proteins. ASP3772 is being evaluated in a  Phase 1/2 clinical study, with Phase 1 now completed in adults aged 18 to 64 and Phase 2 enrollment recently completed in adults over age 65. The poster presentation describing the Phase 1 results was presented at the 2020 IDWeek1 meeting, the joint annual meeting of the Infectious Diseases Society of America (IDSA), Society for Healthcare Epidemiology of America (SHEA), the HIV Medical Association (HIVMA), and the Pediatric Infectious Diseases Society (PIDS).

ASP3772 was observed to be safe and well tolerated in adults 18 to 64 years of age. ASP3772 exhibited robust immunogenicity to the 13 pneumococcal serotypes it shares in common with Prevnar13 as well as to an additional 11 serotypes included in ASP3772. These safety, tolerability and immunogenicity data support the continued development of ASP3772 for protection against Streptococcus pneumoniae in older adults, toddlers and infants. Enrollment has been completed in the Phase 2 clinical trial in adults over the age of 65 and data analyses are currently ongoing. The clinical development program for ASP3772 includes an ongoing Phase 1 study in healthy toddlers 12 to 15 months of age, which is expected to be followed by a planned clinical study in the infant indication. Astellas Pharma Inc. is the sponsor of the ongoing clinical trials of ASP3772, which are listed on

“We are very encouraged by the positive safety and immunogenicity data from this first clinical trial of ASP3772,” said Steven B. Brugger, CEO of Affinivax. “In addition to supporting the continued development of our novel vaccine that offers the potential for much broader protection against Streptococcus pneumoniae, these data provide the first clinical validation of our novel MAPS technology and its broader potential to target infectious diseases for which there are no vaccine or prevention strategies available today.”

ASP3772 is a novel 24-valent pneumococcal vaccine that was developed based on Affinivax’s proprietary MAPS platform, which induces comprehensive B-cell and T-cell immunity. ASP3772 targets the same pneumococcal bacterial strains as included in Prevnar13 (polysaccharides representing serotypes 1, 3, 4, 5, 6A, 6B, 7F, 9V, 14, 18C, 19A, 19F, and 23F), as well as additional pneumococcal strains that are currently most prevalent in the community (polysaccharides representing serotypes 2, 8, 9N, 10A, 11A, 12F, 15B, 17F, 20B, 22F, and 33F).  ASP3772 also includes the fusion of two novel conserved pneumococcal proteins, to which each polysaccharide is attached comprising the final 24-valent MAPS vaccine.

“When we originally conceived of the MAPS vaccine platform at Boston Children’s Hospital, little did we imagine that we would be able to make such rapid progress and complete enrollment in a Phase 1/2 clinical trial,” said Richard Malley, MD, Senior Physician in Medicine, Infectious Diseases, at Boston Children’s Hospital, Professor of Pediatrics at Harvard Medical School, and a scientific founder of Affinivax. “The speed with which ASP3772 was designed, manufactured and clinically tested is remarkable and attests to the power and versatility of the technology.”

The primary objective of the Phase 1 clinical trial in adults aged 18 to 64 was to evaluate the safety and tolerability of three different dose levels of ASP3772, compared with Prevnar13. The secondary objective was to evaluate the immunogenicity of three different dose levels of ASP3772, compared with Prevnar13. The study was a dose-escalation, first-in-human, active-controlled, observer-blinded study. The study population included healthy participants 18 to 64 years of age who had never received a pneumococcal vaccine. These participants were randomly assigned in a 3:1 ratio to receive either ASP3772 (administered intramuscularly at one of three different dose levels) or Prevnar13 (single injection). Safety and tolerability through 7 days post immunization were assessed for each cohort by the dose-escalation committee. Safety and tolerability assessments were continued through 30 days post-immunization, with safety assessments for serious adverse events and medically attended adverse events continued through 180 days post-immunization. Serum samples to measure immunoglobulin G (IgG) and opsonophagocytic activity (OPA) were collected on Day 1, before the first study immunization, and on Day 30 post-immunization.

The design of the fully-enrolled Phase 2 clinical trial in adults over the age of 65 is similar to Phase 1, with the inclusion of an additional cohort of participants to receive Pneumovax, an increase in the total number of participants enrolled in each of the cohorts, and the inclusion of an additional secondary objective to evaluate the immunogenicity of three different dose levels of ASP3772, compared with Pneumovax.

Global Impact and Management of Pneumococcal Disease

Streptococcus pneumoniae (pneumococcus) is a bacterium frequently found in the upper respiratory tract of healthy children and adults, and can cause serious infections ranging from pneumonia, meningitis, and sepsis, representing a major global health problem. The World Health Organization estimates that half a million deaths in children under 5 years old occur each year worldwide due to infection by this bacterium. In the United States, there are over 900,000 cases of pneumococcal pneumonia each year, leading to 400,000 hospitalizations with an associated 5-7% mortality rate in hospitalized patients. Streptococcus pneumoniae is the leading cause of lower respiratory infection morbidity and mortality globally, contributing to more deaths than all other etiologies combined in 2016.1 Prevnar 13, currently recommended by ACIP2 for all infants, is the top selling vaccine worldwide and the top selling product in Pfizer’s entire product portfolio, generating 2019 sales of $5.8 billion and more than $30 billion since 2015. Pneumovax, currently recommended by ACIP for all older adults, generated 2019 sales of $926 million.

About Multiple Antigen Presenting System (MAPS)

The MAPS technology platform uses proprietary chemistry that capitalizes on the specific and durable non-covalent, affinity binding between biotin and rhizavidin, a biotin-binding protein. The MAPS complex created by this affinity binding contributes to a simple, modular, and efficient approach to the development of novel vaccines and immunotherapies. Conventional vaccine conjugation technology seeks to optimize the generation of protective antibody responses mainly to polysaccharide antigens, using the protein antigen as a carrier. In contrast, a MAPS vaccine can present both the polysaccharide and the protein antigens to the host immune system to induce both a B- and T-cell immune response. This unique capability of the MAPS technology allows for the tailored development of each MAPS vaccine or immunotherapy based on the specific type of immune response desired for each pathogen and disease.

About Affinivax, Inc.

Affinivax is advancing a next generation technology platform to enable the development of vaccines and immunotherapies. Backed by investments from Viking Global Investors, Bain Capital Life Sciences, Ziff Capital Partners, and the Bill & Melinda Gates Foundation, Affinivax is focused on the most challenging bacterial infections, both improving upon existing vaccines and providing vaccines for which there are no prevention strategies available today. The company’s proprietary technology platform, called MAPS, enables the high affinity binding of protective polysaccharides and proteins in a single vaccine or immunotherapy to uniquely induce a broad and protective B and T cell immune response. The company’s lead pneumococcal vaccine candidate, ASP3772, being developed in partnership with Astellas Pharma Inc., includes 24 pneumococcal serotypes, more than any other vaccine on the market or in clinical testing today, as well as two novel conserved pneumococcal proteins. This vaccine candidate has been demonstrated to be safe and highly immunogenic in healthy adults and is currently in Phase 1/2 clinical trials. In addition to targeting Streptococcus pneumoniae, the company is advancing a pipeline of MAPS vaccines candidates targeting the most common hospital-associated infections (HAIs) in older adults, and is also extending the utility of MAPS to a range of other potential applications, including vaccines and immunotherapies targeting viral diseases and cancer. For more information, visit

Brand names

Brand names appearing in italics throughout this document are trademarks of GSK or associated companies or used under licence by the Group.

1  GBD 2016 Lower Respiratory Infections Collaborators. Estimates of the global, regional, and national morbidity, mortality, and aetiologies of lower respiratory infections in 195 countries, 1990-2016: A systematic analysis for the Global Burden of Disease Study 2016. Lancet Infect Dis. 2018 Sep 19. pii: S1473-3099(18)30310-4. doi: 10.1016/S1473-3099(18)30310-4.

The Advisory Committee on Immunization Practices (ACIP) is a committee within the United States Centers for Disease Control and Prevention that provides advice and guidance on effective control of vaccine-preventable diseases in the U.S. civilian population.

Back to Top

This links to an external website.