Safety and efficacy results of simulated post-exposure prophylaxis with human immune globulin (HRIG; KEDRAB) co-administered with active vaccine in healthy subjects: a comparative phase 2/3 trial

Immunogenicity and Safety of a Purified Vero Rabies Vaccine-Serum Free, Compared With 2 Licensed Vaccines, in a Simulated Rabies Post-Exposure Regimen in Healthy Adults in France: A Randomized, Controlled, Phase 3 Trial

BACKGROUND

A next-generation Vero cell rabies vaccine (PVRV-NG2) was developed using the same Pitman-Moore strain as in the licensed purified Vero cell vaccine (PVRV; Verorab) and the human diploid cell vaccine (HDCV; Imovax Rabies®).

METHODS

This dual-center, modified, double-blind, phase 3 study evaluated the immunogenic non-inferiority and safety of PVRV-NG2 with and without concomitant intramuscular human rabies immunoglobulin (HRIG) versus PVRV + HRIG and HDCV + HRIG in a simulated post-exposure prophylaxis (PEP) regimen. Healthy adults ≥18 years old (N = 640) were randomized 3:1:1:1 to PVRV-NG2 + HRIG, PVRV + HRIG, HDCV + HRIG, or PVRV-NG2 alone (administered as single vaccine injections on days [D] 0, D3, D7, D14, and 28, with HRIG on D0 in applicable groups). Rabies virus neutralizing antibodies (RVNA) titers were assessed pre- (D0) and post-vaccination (D14, D28, and D42) using the rapid fluorescent focus inhibition test. Non-inferiority, based on the proportion of participants achieving RVNA titers ≥0.5 IU/mL (primary objective), was demonstrated if the lower limit of the 95% CI of the difference in proportions between PVRV-NG2 + HRIG and PVRV + HRIG/HDCV + HRIG was >-5% at D28. Safety was assessed up to 6 months after the last injection.

RESULTS

Non-inferiority of PVRV-NG2 + HRIG compared with PVRV + HRIG and HDCV + HRIG was demonstrated. Nearly all participants (99.6%, PVRV-NG2 + HRIG; 100%, PVRV + HRIG; 98.7%, HDCV + HRIG; 100%, PVRV-NG2 alone) achieved RVNA titers ≥0.5 IU/mL at D28. Geometric mean titers were similar between groups with concomitant HRIG administration at all time points. Safety profiles were similar between PVRV-NG2 and comparator vaccines.

CONCLUSIONS

In a simulated PEP setting, PVRV-NG2 + HRIG showed comparable immunogenicity and safety to current standard-of-care vaccines.

CLINICAL TRIALS REGISTRATION

NCT03965962.

A phase 2b, Randomized, double blinded comparison of the safety and efficacy of the monoclonal antibody mixture SYN023 and human rabies immune globulin in patients exposed to rabies

BACKGROUND

SYN023 is an anti-rabies monoclonal antibody mixture administered as part of post-exposure prophylaxis regimens. The rabies virus neutralizing antibody (RVNA) concentration generally accepted as an adequate immune response to vaccination is ≥ 0.5 IU/mL.

METHODS

Within 54 h of potential rabies exposure, 448 patients in two risk substrata of WHO Category III exposure were randomized to receive either 0.3 mg/kg SYN023 or 0.133 mL/kg human rabies immunoglobulin (HRIG) injected in and around the wound site(s) plus a course of rabies vaccination. Patients were followed for safety and absence of rabies for ≥ 365 days.

RESULTS

GMT RVNA was higher with SYN023 throughout the 2-week post-treatment period. In the primary analysis group (n = 368), 99.4 % of SYN023 recipients versus 4.5 % of HRIG recipients had protective RVNA levels on Day 4. On Day 8, 98.1 % SYN023 versus 12.2 % HRIG recipients were protected. The SYN023:HRIG ratio of geometric mean titer of RVNA (RVNA GMTs) on Day 8 (19.42) exceeded the 10 % superiority margin (P < 0.0001) indicating higher Day 8 RVNA with SYN023. On Day 99, the SYN023:HRIG RVNA GMT ratio (0.66) was below the non-inferiority margin of 20 % (P = 0.9485) suggesting some moderation of vaccine immune response by SYN023 relative to HRIG. The ratio of percent SYN023:HRIG recipients achieving RVNA ≥ 0.5 IU/mL on Day 99 (0.98) met the non-inferiority margin of 20 % (P = 0.013) indicating anti-rabies immune response with SYN023 was non-inferior to HRIG despite this effect. There were no probable/confirmed rabies cases in any patient. Study regimens were well tolerated.

CONCLUSIONS

SYN023 provided higher RVNA than HRIG soon after rabies exposure. By Day 99 post-treatment, GM RVNA with SYN023 was lower than HRIG, however, the percent of SYN023 recipients with a protective response was not inferior at this time point. No rabies cases were reported in the study. The SYN023 safety profile was acceptable.

CLINICALTRIALS

gov ID: NCT03961555.

Safety and immunogenicity of a serum-free purified Vero rabies vaccine in comparison with the rabies human diploid cell vaccine (HDCV; Imovax® Rabies) administered in a simulated rabies post-exposure regimen in healthy adults

A new generation, serum-free, antibiotic-free, purified Vero rabies vaccine (PVRV-NG; Sanofi) has been developed based on the same Pitman-Moore viral strain used for the currently licensed purified Vero cell rabies vaccine (PVRV; Verorab®, Sanofi) and human diploid cell vaccine (HDCV; Imovax® Rabies, Sanofi). PVRV-NG has demonstrated a satisfactory safety profile and induces robust immune responses, with non-inferiority demonstrated versus PVRV when given as a three-dose pre-exposure prophylaxis (PrEP) regimen in healthy children and adults. Here, we evaluated the safety and immunogenic non-inferiority of PVRV-NG compared to HDCV when administered as simulated post-exposure prophylaxis (PEP), with concomitant administration of human rabies immunoglobulin (HRIG), in healthy adults in the USA. Participants were vaccinated according to the 5-dose Essen intramuscular regimen (4-week, 1-injection site regimen, with a single dose given on days 0, 3, 7, 14 and 28) for PEP, with concomitant HRIG administered on day 0. Rabies virus neutralising antibodies (RVNA) were evaluated on days 0, 14, 28 and 42. Non-inferiority of PVRV-NG compared with HDCV was shown if the lower limit of the 95 % confidence interval (CI) for the difference in seroconversion rates (RVNA titers ≥ 0.5 IU/mL on day 14) between PVRV-NG and HDCV was above the non-inferiority margin of -5 %. Safety was evaluated after each vaccination and monitored throughout the study. The difference in seroconversion rate between the PVRV-NG and HDCV groups was -2.8 % (95 % CI, -8.08 to 4.20), indicating that non-inferiority was not demonstrated. The seroconversion rate was < 99 % in both study groups on day 14. There were no major safety concerns identified, and PVRV-NG demonstrated a similar safety profile to HDCV.

Safety and immunogenicity of three dose levels of an investigational, highly purified Vero cell rabies vaccine: A randomized, controlled, observer-blinded, Phase II study with a simulated post-exposure regimen in healthy adults

A serum-free, highly purified rabies vaccine produced in Vero cells is under development. The initial formulation, PVRV-NG, was evaluated in five Phase II studies and subsequently reformulated (PVRV-NG2). This multicenter, observer-blinded Phase II study investigated the safety and immune response of three different doses (antigen content) of PVRV-NG2 versus a licensed human diploid cell rabies vaccine (HDCV; Imovax rabies®). Healthy adults (N = 320) were randomized to receive PVRV-NG2 (low, medium, or high dose), PVRV-NG, or HDCV (2:2:2:1:1 ratio), according to a five-dose Essen simulated post-exposure regimen (Days [D] 0, 3, 7, 14, and 28). All participants received human rabies immunoglobulin intramuscularly on D0. Immunogenicity was assessed at D0, 14, 28, 42, and 6 months after the final injection using the rapid fluorescent focus inhibition test. Seroconversion rates were calculated as the percentage of participants achieving rabies virus neutralizing antibody titers ≥0.5 IU/mL. All analyses were descriptive. At each timepoint, geometric mean titers (GMTs) increased with antigen content (measured using an enzyme-linked immunosorbent assay). High-dose PVRV-NG2 GMTs were the highest at all timepoints, medium-dose PVRV-NG2 GMTs were similar to those with HDCV, and low-dose PVRV-NG2 GMTs were similar to PVRV-NG. The safety profile of PVRV-NG2 was comparable to PVRV-NG; however, fewer injection site reactions were reported with PVRV-NG2 or PVRV-NG (range 36.7-47.5%) than with HDCV (61.5%). This study demonstrated a dose-effect of antigen content at all timepoints. As post-exposure prophylaxis, the safety and immunogenicity profiles of the high-dose PVRV-NG2 group compared favorably with HDCV. Clinicaltrials.gov number: NCT03145766.

Safety and clinical efficacy of human rabies immunoglobulin in post exposure prophylaxis for category III animal exposures

The human rabies immunoglobulin (HRIG) is a life-saving immune biological essential for all category III animal exposures. It provides neutralizing antibodies at the site of exposure until the body can produce vaccine-mediated antibodies. We conducted this study to determine the safety and clinical efficacy of an HRIG being used presently for post-exposure prophylaxis (PEP) and to strengthen the existing evidence for its further usage. We conducted a prospective cohort study in 123 subjects with category III animal exposures at the KIMS Hospital and Research Center, Bangalore, India. Post-exposure prophylaxis (PEP) with wound toilet, a single application of HRIG, and a full course of anti-rabies vaccination were provided to all the study subjects. The volume of HRIG was calculated according to the body weight, and all the wounds were infiltrated as was anatomically feasible. All the study subjects were followed up for immediate and delayed adverse events (AE), both local and systemic. Subsequently, all the subjects were followed up for 6 months to demonstrate the clinical efficacy of PEP. The incidence of AEs was 11.4% including local pain, erythema, itching, headache, body ache, fever, and malaise. All AEs were mild and subsided without any complications. All the study subjects were healthy and alive after 6 months following the administration of HRIG, along with a full course of anti-rabies vaccine. Our study provides evidence of safety and clinical efficacy of HRIG for category III animal exposures and supports its continued usage.

Inhibitory effect of concomitantly administered rabies immunoglobulins on the immunogenicity of commercial and candidate human rabies vaccines in hamsters

The World Health Organization protocol for rabies post-exposure prophylaxis (PEP) recommends extensive wound washing, immediate vaccination, and administration of rabies immunoglobulin (RIG) in severe category III exposures. Some studies have shown that RIG can interfere with rabies vaccine immunogenicity to some extent. We investigated the interference of RIG on a next generation highly purified Vero cell rabies vaccine candidate (PVRV-NG) versus standard-of-care vaccines in a previously described hamster model. The interference of either human (h) or equine (e) RIG on the immune response elicited by PVRV-NG, Verorab^® (purified Vero cell rabies vaccine, PVRV), and Imovax^® Rabies (human diploid cell rabies vaccine; HDCV) was evaluated using the 4-dose Essen PEP regimen. The anti-rabies seroneutralizing titers and specific serum IgM titers were measured by fluorescent antibody virus neutralization test and enzyme-linked immunosorbent assay, respectively, for the vaccines administered with or without RIG. The RIG interference on PVRV-NG, observed transiently at Day 7, was similar to that on PVRV and tended to be lower than that on HDCV using both read-outs. In summary, the results generated in the hamster model showed that RIG induced similar or less interference on PVRV-NG than the standard-of-care vaccines.

Headache After Vaccination: An Update on Recent Clinical Trials and Real-World Reporting

PURPOSE OF REVIEW

The aim of this review is to characterize headache as a vaccine adverse event (VAE) in clinical trials.

RECENT FINDINGS

Of the recent phase III vaccine RCTs (non-COVID-19), 53 studies reported on headache (13 infectious agents). The median rate (interquartile range) of headache was 15.6% (IQR: 9.6-37.6%). Of these, 24.5% of the RCTs reported headache greater in the vaccine group compared to the placebo/control group. In the herpes zoster vaccination trials, headache was more common in all active groups: median rate 33.9% (IQR: 29.7-40.5%) as compared to placebo: median rate 17.7% (IQR: 15.4-23.8%). Influenza and HPV vaccination trials were the 2nd and 3rd most common to have headache as a VAE. Of the 6 widely distributed COVID-19 vaccinations, median rate of post-vaccination headache was 39% (IQR: 28-50%). Headache is a common VAE in vaccine trials. Standardized grading methods, predictors of persistence, and treatment regimens are warranted.

Rabies virus neutralizing activity, pharmacokinetics, and safety of the monoclonal antibody mixture SYN023 in combination with rabies vaccination: Results of a phase 2, randomized, blinded, controlled trial

BACKGROUND

SYN023-002 is a randomized, blinded, controlled study comparing rabies virus neutralizing activity (RVNA) and safety of SYN023, a monoclonal anti-rabies antibody mixture, to human-serum derived anti-rabies immunoglobulin (RIG) when administered with commercially available vaccines to healthy adult volunteers.

METHODS

Participants were randomized among 4 treatment groups (SYN023 + Imovax, SYN023 + RabAvert, HyperRab + Imovax, HyperRab + RabAvert). On Day 0, subjects received 1 dose of RIG (0.3 mg/kg SYN023 or 20 IU/mL HyperRab) and their first of 5 vaccine doses. The primary objective was to compare cumulative RVNA between SYN023 and HyperRab recipients. Secondary objectives were to compare safety and to assess SYN023 pharmacokinetics and immunogenicity.

RESULTS

All 164 randomized subjects initiated treatment and were included in safety analyses. At least 34 subjects/treatment group received all treatment and had complete RVNA results, thus were included in the primary endpoint analysis. Mean RVNAs were approximately ten-fold higher in SYN023 recipients compared to HyperRab recipients until Day 14. From Day 14 onwards, mean RVNA was lower in SYN023 recipients, but remained above the RVNA level widely considered adequate (≥0.5 IU/mL) through Day 112 (study end). The point estimate of the cumulative RVNA (83.22% SYN023/HyperRab), but not the lower CI bound (90% CI: 66.06%, 104.83%), fell within the protocol-defined similarity margin. Each RIG + vaccine regimen appeared safe with mostly mild AEs and no serious or severe related events observed. Except injection site pain (22% HyperRab recipients vs. 6% SYN023 recipients), treatment-related AEs incidences were similar between RIGs. Anti-SYN023 antibodies were observed but had no apparent effects on PK or safety.

CONCLUSIONS

SYN023 administered with commercially available vaccines provides adequate antibody coverage beginning earlier than other commercially available RIGs with an acceptable safety profile. Some suppression of vaccine response occurred, but RVNA levels ≥ 0.5 IU/mL were maintained throughout the relevant period.

REGISTRATION

ClinicalTrials.gov #NCT02956746.

FUNDING

Synermore biologics.

Perspectives on passive antibody therapy and peptide-based vaccines against emerging pathogens like SARS-CoV-2

The current epidemic of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is raising awareness of the need to act faster when dealing with new pathogens. Exposure to an emerging pathogen generates an antibody response that can be used for preventing and treating the infection. These antibodies might have a high specificity to a target, few side effects, and are useful in the absence of an effective vaccine for treating immunocompromised individuals. The approved antibodies against the receptor-binding domain (RBD) of the viral spike protein of SARS-CoV-2 (e.g., regdanvimab, bamlanivimab, etesevimab, and casirivimab/imdevimab) have been selected from the antibody repertoire of B cells from convalescent patients using flow cytometry, next-generation sequencing, and phage display. This encourages use of these techniques especially phage display, because it does not require expensive types of equipment and can be performed on the lab bench, thereby making it suitable for labs with limited resources. Also, the antibodies in blood samples from convalescent patients can be used to screen pre-made peptide libraries to identify epitopes for vaccine development. Different types of vaccines against SARS-CoV-2 have been developed, including inactivated virus vaccines, mRNA-based vaccines, non-replicating vector vaccines, and protein subunits. mRNA vaccines have numerous advantages over existing vaccines, such as efficacy, ease of manufacture, safety, and cost-effectiveness. Additionally, epitope vaccination may constitute an attractive strategy to induce high levels of antibodies against a pathogen and phages might be used as immunogenic carriers of such peptides. This is a point worth considering further, as phage-based vaccines have been shown to be safe in clinical trials and phages are easy to produce and tolerate high temperatures. In conclusion, identification of the antibody repertoire of recovering patients, and the epitopes they recognize, should be an attractive alternative option for developing therapeutic and prophylactic antibodies and vaccines against emerging pathogens.

Safety and efficacy of rabies immunoglobulin in pediatric patients with suspected exposure

Rabies is a deadly viral zoonosis with global disease burden. Following exposure to a rabid animal, post-exposure prophylaxis (PEP) is the standard of care for unvaccinated persons. Despite the large proportion of pediatric cases, limited safety and efficacy data exist for use in pediatric patients. We report the safety, efficacy, and immunogenicity of a phase 4, prospective, 2-center, open-label, single-arm clinical trial evaluating human rabies immunoglobulin (HRIG150; KEDRAB 150 IU/mL) as part of PEP in patients (aged <17) with suspected or confirmed rabies exposure, where PEP was indicated. Thirty participants received 20 IU/kg HRIG150 infiltrated into the detectable wound site(s), with any remainder injected intramuscularly, concomitantly with the first of a 4-dose series (days 0, 3, 7, and 14) of rabies vaccine. Rabies virus neutralizing antibody (RVNA) titers and tolerability were assessed on day 14 following administration. Participant safety was monitored for 84 days. No serious adverse events, rabies infections, or deaths were recorded. Twenty-one participants (70.0%) experienced a total of 57 treatment-emergent adverse events (TEAEs) within 14 days following administration. Twelve participants (40.0%) experienced a total of 13 adverse events deemed treatment related. All TEAEs were mild in severity. On day 14, 28 participants (93.3%) had RVNA levels of ≥0.5 IU/mL (mean±standard deviation: 18.89 ± 31.61). These results demonstrate that HRIG150 is well tolerated and effective in pediatric patients as a component of PEP. To the authors' knowledge, this study is the first to establish pediatric safety and efficacy of HRIG in the US.

Antibody response to SARS-Co-V-2, diagnostic and therapeutic implications

The immune response against SARS-CoV-2 is comprised of both cellular and humoral arms. While current diagnostic methods are mainly based on PCR, they suffer from insensitivity. Therefore, antibody-based serological tests are being developed to achieve higher sensitivity and specificity. Current efforts in treating SARS-CoV-2 infection include blocking of viral entry into the host cells, prohibiting viral replication and survival in the host cells, or reducing the exaggerated host immune response. Administration of convalescent plasma containing anti-viral antibodies was proposed to improve the outcome in severe cases. In this paper, we review some of the aspects associated with the development of antibodies against SARS-CoV-2 and their potential use for improved diagnosis and therapy.