Anthrax Vaccine Clinical Trial to Assess Dose Reduction and Route Change

This study is a 43-month prospective, randomized, double-blind, placebo-controlled comparison of immunogenicity and reactogenicity elicited by BioThrax given by different routes of administration (SQ versus IM) and dosing regimens (as many as 8 doses versus as few as 4 doses). Sterile saline is used as the placebo where doses are dropped in regimens using AVA, and in the all-placebo study group.

This study is conducted among a total of 1564 healthy adult men and women (18 to 61 years of age) at five sites in the United States. Participants were randomized into one of 6 study groups with 260 participants per group. One group receives BioThrax given as currently licensed (SQ with 6 doses followed by annual boosters); another group is given placebo IM (130 participants) or SQ (130 participants) in the currently licensed dosing regimen. The four other groups receive BioThrax IM in modified dosing regimens; placebo is given when a dose of BioThrax is omitted from the licensed dosing regimen. There are a total of 25 required visits for this study, during which all participants receive an injection of vaccine or placebo (8 injections total), have a blood sample drawn (16 or 17 total), and have an in-clinic examination for adverse events (22 total).

Immunogenicity is assessed by assaying 16 serial blood samples obtained from all participants and a 17th sample from a subset of participants before vaccination and at other specified times. Total anti-protective antigen IgG antibody (anti-PA IgG) is quantified using a standardized and validated enzyme-linked immunosorbent assay (ELISA); the primary study endpoints are 4-fold rise in antibody titer and antibody concentration relative to the pre-vaccination titers or assay reactivity threshold. A subset of serum samples is also assayed in an in vitro toxin neutralization assay (TNA) to measure the functional activity of anti-BioThrax antibodies. The kinetics of the immune response to BioThrax are examined at 3 time points in the study and blood samples from a subset of participants will be further tested in correlates of protection and immunogenetics substudies. All adverse events (AEs), including vaccine reactogenicity, are actively monitored. While all AEs will be ascertained among study participants, several endpoints will be defined based on the likelihood of their occurrence and/or their clinical importance. Of primary interest is the occurrence of local AEs such as warmth, tenderness, itching, pain, arm motion limitation, erythema, induration, nodule, and bruise. Systemic AEs such as fever, fatigue, muscle ache, headache, temperature, and painful axillary adenopathy are also evaluated.

This study is expected to provide the basis for consideration of change in route of BioThrax administration from SQ to IM and reduction in number of vaccine doses required for primary and booster immunization.

There is an interim analysis of data collected through each participant's first 7 months of this study for consideration in changing the route of BioThrax administration from SQ to IM, and elimination of the 2 week vaccine priming dose.

At the end of the study, the Sponsor will present the entire results of the trial to FDA for consideration in elimination of additional doses from the licensed BioThrax schedule. At that time, the Sponsor will also supplement these data with results from parallel non-human primate challenge studies and additional research on immunologic correlates of protection.

• Anthrax Vaccine Adsorbed (Biological), also known as AVA, BioThrax
• Saline injection (Biological)

Primary outcomes

• Local AEs [4 weeks after each injection]: warmth, tenderness, itching, pain, arm motion limitation, erythema, induration, nodule, and bruise. The number of injections analyzable varies for each event based on the presence or absence of reported data.
• Systemic AEs [4 weeks after each injection]: Fatigue, Muscle Ache, Headache, Fever, Tender Axillary Lymphnode The number of injections analyzable varies for each event based on the presence or absence of reported data.
• Anti-protective Antigen IgG Geometric Mean Concentration [4 weeks after the m1, m6 and m42 injections]: Geometric mean of the Anti-PA IgG Concentration measured in μg/mL. The lower limit of quantification (LLOQ) is 3.7, results below the LLOQ have been replaced by 1/2 LLOQ (1.85) before taking the geometric mean.
• Anti-protective Antigen IgG Geometric Mean Titer [4 weeks after the m1, m6 and m42 injections]: Geometric mean of the Dilutional Titer. The Dilutional Titer is the reciprocal of the dilution at which the anti-PA IgG response reaches a threshold. The lower limit of quantification (LLOQ) is 58, results below the LLOQ have been replaced by 1/2 LLOQ (29) before taking the geometric mean.
• 4-fold Rise in Anti-protective Antigen IgG Titer Response [4 weeks after the m1, m6 and m42 injections]: Percent of participants who achieved a 4-fold or greater rise in anti-PA IgG Titer relative to the pre-vaccination level at month 0. The Dilutional Titer is the reciprocal of the dilution at which the anti-PA IgG response reaches a threshold. The lower limit of quantification (LLOQ) is 58, results below the LLOQ have been replaced by LLOQ (58) before calculating the fold response. Thus the lowest titer that can achieve 4-fold rise is 4*58 = 232.

Secondary outcomes

• TNA ED50 Titer [4 weeks after the m1, m6 and m42 injections]: Geometric mean of the ED50. The ED50 is the reciprocal of the dilution at which patient serum neutralizes 50% of a dose of anthrax lethal toxin (ED50). The lower limit of quantification (LLOQ) for this assay is 36, results below the LLOQ have been replaced with 1/2 LLOQ (18) before taking the geometric mean. Note that this secondary endpoint was only performed on \~47% of the participants.

Sex: All, ages: 18 Years to 61 Years, accepts healthy volunteers

Inclusion Criteria:

Read/sign Informed Consent Document; Female or male, 18 to 61 years old (up to 62nd birthday); Females must agree to exercise adequate birth control from the time of the screening procedures to one month after the last vaccination; willingness/ability to return for all follow-up visits and blood collections for the duration of the study; ability to understand/comply with planned study procedures; agree to complete the Participant Diary (Appendix G) and to report concomitant medications and AEs during the study period; thave two intact upper arms with sufficient subcutaneous and intramuscular tissue in the deltoid regions for vaccine administration.Potential participants with a history of the following conditions remain eligible for study enrollment: gestational diabetes; treated, controlled, uncomplicated hypertension; treated hypo- or hyperthyroidism; cured nonmetastatic cancer; disease-free for 5 years (excluding hematologic malignancies); localized skin cancer, resected (including squamous cell and basal cell carcinomas, participants with a history of melanoma must be disease-free for 5 years); exercise-induced bronchospasm; mild asthma: use of inhalers only for control of symptoms is acceptable (Persons who have required hospitalization for asthma within the previous 2 years or those who require chronic or frequent oral/parenteral steroids will not be eligible; use of low to medium doses of inhaled steroids; history of coronary artery disease, asymptomatic (NYHA Function Class I), on a stable medical regimen. Persons meeting these criteria must be at least 2 years post-myocardial infarction, cardiac bypass surgery, and/or percutaneous coronary intervention (e.g., angioplasty, stent placement, etc) in order to qualify. Persons with a history of cardiac disease must be under the care of a physician.

Exclusion Criteria:

Prior history of anthrax or immunization against anthrax; Known allergy to aluminum hydroxide, formaldehyde, benzethonium chloride, or latex; Pregnant/plans to become pregnant for duration of study/does not agree to use adequate birth control from the time of screening procedures to one month after last vaccination; Used cytotoxic therapy in previous 5 years; Cardiovascular disease with significant likelihood of progression over 5 years; Moderate to severe asthma, chronic obstructive pulmonary disease, other significant pulmonary disease; using high doses of inhaled steroids; Clinically recognized hepatic or renal insufficiency; Inflammatory, vasculitic, or rheumatic disease including systemic lupus erythematosis, polymyalgia rheumatica and rheumatoid arthritis, scleroderma; Known HIV, hepatitis B or hepatitis C infection; Other conditions known to produce or be associated with immune suppression; Neuropathy or other evolving neurologic condition; Unstable/moderate to severe mental illness; Ongoing drug abuse/dependence (including alcohol); Seizure disorder; Active malignancy or history of metastatic or hematologic malignancy; current diabetes; Anyone who plans to receive within 60 days of study entry: cytotoxic therapy, experimental products, a live vaccine outside this trial, immunosuppressive therapy, parenteral immunoglobulin or blood products; Anyone who plans to receive an inactivated vaccine outside this trial within 42 days after study entry;: experimental products, a live vaccine outside this trial, immunosuppressive therapy; Anyone who received an inactivated vaccine outside this trial within 14 days prior to study entry, parenteral immunoglobulin or blood products within three months of study. In addition to conditions listed above, temporary exclusion would result from moderate or severe illness and/or oral temperature >100.4˚F within 3 days of injection or chronic condition that, in opinion of investigator, would render injection unsafe or would interfere with evaluations.

Participant flow

Outcome results

• Local AEs (Primary), Number, injections: SQ Females 500; IM Female 344; SQ Males 186; IM Male 189
• Systemic AEs (Primary), Number, injections: SQ Females 118; IM Female 278; SQ Males 69; IM Male 182
• Anti-protective Antigen IgG Geometric Mean Concentration (Primary), Geometric mean, μg/ml: Anthrax Vaccine Adsorbed 8-SQ 94.3 (82.1 to 108.3); Anthrax Vaccine Adsorbed 8-IM 84.5 (73.7 to 96.8); Anthrax Vaccine Adsorbed 7-IM NA (NA to NA); Anthrax Vaccine Adsorbed 5-IM NA (NA to NA); Anthrax Vaccine Adsorbed 4-IM NA (NA to NA); Anthrax Vaccine Adsorbed 754-IM 46.4 (42.2 to 51.0); Saline Placebo IM or SQ 1.9 (1.9 to 2.0)
• TNA ED50 Titer (Secondary), Geometric mean, ED50 Dilutional Titer: Anthrax Vaccine Adsorbed 8-SQ 229.1 (190.9 to 274.9); Anthrax Vaccine Adsorbed 8-IM 240.8 (196.5 to 295.2); Anthrax Vaccine Adsorbed 7-IM NA (NA to NA); Anthrax Vaccine Adsorbed 5-IM NA (NA to NA); Anthrax Vaccine Adsorbed 4-IM NA (NA to NA); Anthrax Vaccine Adsorbed 754-IM 165.5 (146.2 to 187.4); Saline Placebo IM or SQ 18.0 (18.0 to 18.0)
• Anti-protective Antigen IgG Geometric Mean Titer (Primary), Geometric mean, Dilutional Titer: Anthrax Vaccine Adsorbed 8-SQ 1048.5 (913.1 to 1204.1); Anthrax Vaccine Adsorbed 8-IM 934.8 (815.6 to 1071.3); Anthrax Vaccine Adsorbed 7-IM NA (NA to NA); Anthrax Vaccine Adsorbed 5-IM NA (NA to NA); Anthrax Vaccine Adsorbed 4-IM NA (NA to NA); Anthrax Vaccine Adsorbed 754-IM 514.6 (468.1 to 565.7); Saline Placebo IM or SQ 29.7 (28.7 to 30.6)
• 4-fold Rise in Anti-protective Antigen IgG Titer Response (Primary), Number, % of participants with ≥4-fold rise: Anthrax Vaccine Adsorbed 8-SQ 94.9 (91.3 to 97.3); Anthrax Vaccine Adsorbed 8-IM 91.9 (87.6 to 95.0); Anthrax Vaccine Adsorbed 7-IM NA (NA to NA); Anthrax Vaccine Adsorbed 5-IM NA (NA to NA); Anthrax Vaccine Adsorbed 4-IM NA (NA to NA); Anthrax Vaccine Adsorbed 754-IM 78.8 (75.6 to 81.8); Saline Placebo IM or SQ 0.4 (0.01 to 2.3)

Adverse events

Time frame: The observation period for Solicited AEs and Other AEs was 14 days post-injection for the first two injections, and 28 days for all subsequent injections. Serious Adverse Event (SAE) data were collected and reported to FDA as they occurred.

Serious adverse events by term

77 more terms not shown.

Other adverse events by term

Limitations and caveats: The study was not statistically powered to identify very rare SAEs.

• Marano N, Plikaytis BD, Martin SW, Rose C, Semenova VA, Martin SK, Freeman AE, Li H, Mulligan MJ, Parker SD, Babcock J, Keitel W, El Sahly H, Poland GA, Jacobson RM, Keyserling HL, Soroka SD, Fox SP, Stamper JL, McNeil MM, Perkins BA, Messonnier N, Quinn CP; Anthrax Vaccine Research Program Working Group. Effects of a reduced dose schedule and intramuscular administration of anthrax vaccine adsorbed on immunogenicity and safety at 7 months: a randomized trial. JAMA. 2008 Oct 1;300(13):1532-43. doi: 10.1001/jama.300.13.1532. PMID 18827210
• Results publication: Wright JG, Plikaytis BD, Rose CE, Parker SD, Babcock J, Keitel W, El Sahly H, Poland GA, Jacobson RM, Keyserling HL, Semenova VA, Li H, Schiffer J, Dababneh H, Martin SK, Martin SW, Marano N, Messonnier NE, Quinn CP. Effect of reduced dose schedules and intramuscular injection of anthrax vaccine adsorbed on immunological response and safety profile: a randomized trial. Vaccine. 2014 Feb 12;32(8):1019-28. doi: 10.1016/j.vaccine.2013.10.039. Epub 2013 Dec 25. PMID 24373307
• Results publication: Quinn CP, Sabourin CL, Schiffer JM, Niemuth NA, Semenova VA, Li H, Rudge TL, Brys AM, Mittler RS, Ibegbu CC, Wrammert J, Ahmed R, Parker SD, Babcock J, Keitel W, Poland GA, Keyserling HL, El Sahly H, Jacobson RM, Marano N, Plikaytis BD, Wright JG. Humoral and Cell-Mediated Immune Responses to Alternate Booster Schedules of Anthrax Vaccine Adsorbed in Humans. Clin Vaccine Immunol. 2016 Apr 4;23(4):326-38. doi: 10.1128/CVI.00696-15. Print 2016 Apr. PMID 26865594
• Results publication: Falola MI, Wiener HW, Wineinger NE, Cutter GR, Kimberly RP, Edberg JC, Arnett DK, Kaslow RA, Tang J, Shrestha S. Genomic copy number variants: evidence for association with antibody response to anthrax vaccine adsorbed. PLoS One. 2013 May 31;8(5):e64813. doi: 10.1371/journal.pone.0064813. Print 2013. PMID 23741398
• Results publication: Pajewski NM, Parker SD, Poland GA, Ovsyannikova IG, Song W, Zhang K, McKinney BA, Pankratz VS, Edberg JC, Kimberly RP, Jacobson RM, Tang J, Kaslow RA. The role of HLA-DR-DQ haplotypes in variable antibody responses to anthrax vaccine adsorbed. Genes Immun. 2011 Sep;12(6):457-65. doi: 10.1038/gene.2011.15. Epub 2011 Mar 3. PMID 21368772

• Jennifer Wright, DVM, Principal investigator, Centers for Disease Control and Prevention