Top-Line Data Expected in the Fourth Quarter of 2015

CAMBRIDGE, MA, USA I April 22, 2015 I Genocea Biosciences, Inc. (NASDAQ:GNCA), a biopharmaceutical company developing T cell-directed vaccines and immunotherapies, today reported that it has completed enrollment in its Phase 2a human challenge study of GEN-004, Genocea’s universal vaccine candidate for the prevention of infection by all serotypes of pneumococcus. The Company anticipates reporting top-line data from this study in the fourth quarter of 2015.

“The objective of this trial is to demonstrate proof of concept that GEN-004 can reduce the frequency, magnitude or duration of colonization of pneumococcus in the nasopharynx of healthy adults,” said Seth Hetherington, M.D., Chief Medical Officer of Genocea. “Colonization in the nasopharynx is a necessary precursor to infection by pneumococcus and success in this trial will provide further evidence of the potential of GEN-004 to control colonization and strongly position us to advance GEN-004 into further efficacy studies in 2016.”

The Phase 2a trial enrolled 98 healthy adult subjects at one site in the United Kingdom. Subjects are randomized to receive 3 doses of either placebo or GEN-004 at 100 micrograms per protein and 350 micrograms of alum adjuvant. All subjects are challenged with pneumococcus after the third dose of the assigned treatment and subsequently tested for the establishment of colonization. The current study follows positive Phase 1 results, demonstrating that GEN-004 met its safety, tolerability and immunogenicity goals, including increases in blood T helper 17 (TH17) cells, a rare cell type that provides important protective immunity at epithelial and mucosal surfaces.

For more information about this Phase 2a clinical study of GEN-004 visit www.clinicaltrials.gov.

About GEN-004

GEN-004 is a potential universal pneumococcal vaccine designed based on insights from the Company’s ATLAS™ platform. GEN-004 contains three unique pneumococcal protein antigens, SP0148, SP1912, and SP2108, shown by ATLAS™ to be associated with protective TH17 T cell responses against pneumococcus in humans. All three antigens are conserved across all sequenced serotypes of pneumococcus. ATLAS™ profiles the comprehensive spectrum of actual T cell responses mounted by humans in response to a pathogen, enabling the identification of antigen targets with which to design new vaccines and immunotherapies. For more information about GEN-004, please visit http://www.genocea.com/platform-pipeline/pipeline/gen004-for-pneumococcus/.

About pneumococcus (Streptococcus pneumoniae)

Streptococcus pneumoniae, also known as pneumococcus, is a major cause of infectious disease-related death worldwide. The World Health Organization (WHO) estimates that up to 1.6 million people, including 800,000 children, die each year globally as a result of pneumococcal infection. Pneumococcus colonizes the nasopharynx, or nose and throat, as a precursor to infection. Pneumococcus causes non-invasive pneumococcal disease (NIPD) when it spreads from the nasopharynx into the upper and lower respiratory system to cause diseases such as otitis media (ear infection) and non-bacteremic pneumonia. When it enters the bloodstream, pneumococcus can cause invasive pneumococcal disease (IPD), including life-threatening illnesses such as sepsis, meningitis and bacteremic pneumonia.

In childhood, immunity to pneumococcus is developed prior to the establishment of protective antibody responses. Scientists believe that this immunity is driven by a rare type of T cells called TH17 CD4+ T cells, which prevent establishment of disease by clearing pneumococcus from the nasopharynx.

About Genocea Biosciences, Inc.

Genocea is harnessing the power of T cell immunity to develop life-changing vaccines and immunotherapies. T cells are increasingly recognized as a critical element of protective immune responses to a wide range of diseases, but traditional discovery methods have proven unable to identify the targets of such protective immune response. Using ATLAS™, its proprietary technology platform, Genocea identifies these targets to potentially enable the rapid development of medicines to address critical patient needs. Genocea’s pipeline of clinical-stage T cell-enabled product candidates includes GEN-003 for genital herpes, GEN-004 for the prevention of infection by all serotypes of pneumococcus, and earlier-stage programs in chlamydia, genital herpes prophylaxis, malaria and cancer immunotherapies. For more information, please visit the company’s website at www.genocea.com.

SOURCE: Genocea