Developmental and reproductive safety evaluation of AV7909 anthrax vaccine candidate in rats

Evaluation of the AV7909 Anthrax Vaccine Toxicity in Sprague Dawley Rats Following Three Intramuscular Administrations

AV7909 is a next-generation anthrax vaccine under development for post-exposure prophylaxis following suspected or confirmed Bacillus anthracis exposure, when administered in conjunction with the recommended antibacterial regimen. AV7909 consists of the FDA-approved BioThrax® vaccine (anthrax vaccine adsorbed) and an immunostimulatory Toll-like receptor 9 agonist oligodeoxynucleotide adjuvant, CPG 7909. The purpose of this study was to evaluate the potential systemic and local toxicity of AV7909 when administered via repeat intramuscular injection to the right thigh muscle (biceps femoris) to male and female Sprague Dawley rats. The vaccine was administered on Days 1, 15, and 29 and the animals were assessed for treatment-related effects followed by a 2-week recovery period to evaluate the persistence or reversibility of any toxic effects. The AV7909 vaccine produced no apparent systemic toxicity based on evaluation of clinical observations, body weights, body temperature, clinical pathology, and anatomic pathology. Necrosis and inflammation were observed at the injection sites as well as in regional lymph nodes and adjacent tissues and were consistent with immune stimulation. Antibodies against B. anthracis protective antigen (PA) were detected in rats treated with the AV7909 vaccine, confirming relevance of this animal model for the assessment of systemic toxicity of AV7909. In contrast, sera of rats that received saline or soluble CPG 7909 alone were negative for anti-PA antibodies. Overall, 3 intramuscular immunizations of Sprague Dawley rats with AV7909 were well tolerated, did not induce mortality or any systemic adverse effects, and did not result in any delayed toxicity.

Developmental and reproductive safety evaluation of AV7909 anthrax vaccine candidate in rats

The AV7909 vaccine, consists of the Anthrax Vaccine Adsorbed (AVA) bulk drug substance and the immunostimulatory Toll‐like receptor 9 agonist oligodeoxynucleotide adjuvant CPG 7909. The purpose of this research was to evaluate the potential maternal, reproductive, and developmental toxicity of AV7909 in rats to support licensure for use in women of childbearing potential. Groups of first generation (F₀) female Sprague Dawley rats were dosed by intramuscular injection with water for injection, adjuvant or AV7909 at a volume of 0.5 ml/dose. Each rat received three vaccinations: 14 days prior to start of the mating period, on the first day of the mating period and on gestation day (GD) 7. There was no maternal mortality. Body weights, weight gain, and food consumption were comparable between groups. Findings in F₀ females were limited to transient injection site edema and nodules consistent with immunostimulatory effects of the vaccine and adjuvant. Administration of AV7909 did not affect mating, fertility, pregnancy, embryo‐fetal viability, growth, or morphologic development, parturition, maternal care of offspring or postnatal survival, growth, or development. There was no evidence of systemic inflammation in pregnant rats, based on evaluation of serum concentrations of the acute phase proteins alpha‐2‐macroglobulin and alpha‐1‐acid glycoprotein on GD 21. Anthrax lethal toxin‐neutralizing antibodies were detected in AV7909‐vaccinated F₀ females. The antibodies were also detected in the sera of fetuses and F₁ pups. Exposure of the fetuses and pups to maternally derived anthrax lethal toxin‐neutralizing antibodies was not associated with developmental toxicity.