Genocea Biosciences, Inc. announced the commencement of the dosing phase in a Phase 2b clinical trial for GEN-003 for the treatment of genital herpes. Patient screening for the trial, which was initiated in December 2015, is complete. The Company expects to report top-line viral shedding data from the immediate post-dosing observation period in mid-2016 and clinical efficacy data against potential Phase 3 study endpoints at six months after dosing in the second half of 2016.

The Phase 2b study will enroll approximately 135 subjects from nine institutions in the United States. Subjects will be randomized to one of two dose levels of GEN-003 or placebo, and receive three injections at 21-day intervals. Viral shedding rate reductions will be measured to demonstrate the activity of the new formulation.

The study will also compare GEN-003 efficacy to placebo for the clinical endpoints of: the proportion of patients who are lesion free at six and 12 months after dosing; the time to first lesion recurrence after dosing; and, the impact on percentage of days with genital herpes lesions at six and 12 months after dosing. All subjects will be followed for 12 months after the last dose. Genocea is currently conducting a Phase 2 dose optimization study with an anticipated 12-month data read out later in the first quarter of 2016.

In October, the Company announced positive results from a planned interim analysis of data collected six months after dosing. At its best performing dose of 60 µg per protein /75 µg of Matrix-M2™ adjuvant, GEN-003 demonstrated a statistically significant 58% reduction from baseline in the viral shedding rate (p<0.0001), the primary endpoint of the study. In a planned secondary analysis, the proportion of patients receiving GEN-003 who were lesion-free at six months after dosing ranged from approximately 30% to 50%, similar to results reported in clinical trials with oral antiviral therapies.

In addition, the time to first recurrence after completion of dosing showed a range of 152 days to greater than 180 days among dose groups. In a further secondary analysis measuring the impact on genital lesion rates, GEN-003 demonstrated sustained and statistically significant reductions from baseline in five of six dose groups ranging from 43% to 69%. The Phase 2 study continued to show that GEN-003 is safe and well tolerated by patients, with no serious adverse events related to the vaccine.