Neutralization Activity of Anti-drug Antibodies Against a Biotherapeutic Can Be Predicted from a Comprehensive Pharmacokinetics, Pharmacodynamics, and Anti-drug Antibody Data Analysis

Historically, a neutralization antibody (NAb) assay is considered critical in immunogenicity assessment of biologic therapeutics, even with low anti-drug antibody (ADA) positive rates. In 2019, FDA new guidelines issued on immunogenicity testing acknowledged the possibility of using "a highly sensitive PD marker or an appropriately designed PK assay or both that generate data that inform clinical activity" to replace a NAb assay. In the current manuscript, we present data for PK, PD, and ADA assays which collectively succeed to replace the standalone NAb assay. The data include a total LC/MS-based PK assay, a serum neutralization antibody (SNA) assay that essentially measures pharmacodynamically functional PK and can detect NAb activity in the presence of 1:1 ratio of drug, and a highly drug-tolerant ADA assay. In addition, a model-based meta-analysis (MBMA) demonstrated that the ability of SNA assay to detect NAb at 1:1 ratio of drug is sensitive enough to monitor clinically meaningful efficacy change, which is 50% reduction of SNA titer. Our strategy of preparing a holistic data package discussed here may provide a roadmap to the community for alternatives in assaying neutralizing activity of ADA.

Evaluation of prognostic risk models for postoperative pulmonary complications in adult patients undergoing major abdominal surgery: a systematic review and international external validation cohort study

BACKGROUND

Stratifying risk of postoperative pulmonary complications after major abdominal surgery allows clinicians to modify risk through targeted interventions and enhanced monitoring. In this study, we aimed to identify and validate prognostic models against a new consensus definition of postoperative pulmonary complications.

METHODS

We did a systematic review and international external validation cohort study. The systematic review was done in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. We searched MEDLINE and Embase on March 1, 2020, for articles published in English that reported on risk prediction models for postoperative pulmonary complications following abdominal surgery. External validation of existing models was done within a prospective international cohort study of adult patients (≥18 years) undergoing major abdominal surgery. Data were collected between Jan 1, 2019, and April 30, 2019, in the UK, Ireland, and Australia. Discriminative ability and prognostic accuracy summary statistics were compared between models for the 30-day postoperative pulmonary complication rate as defined by the Standardised Endpoints in Perioperative Medicine Core Outcome Measures in Perioperative and Anaesthetic Care (StEP-COMPAC). Model performance was compared using the area under the receiver operating characteristic curve (AUROCC).

FINDINGS

In total, we identified 2903 records from our literature search; of which, 2514 (86·6%) unique records were screened, 121 (4·8%) of 2514 full texts were assessed for eligibility, and 29 unique prognostic models were identified. Nine (31·0%) of 29 models had score development reported only, 19 (65·5%) had undergone internal validation, and only four (13·8%) had been externally validated. Data to validate six eligible models were collected in the international external validation cohort study. Data from 11 591 patients were available, with an overall postoperative pulmonary complication rate of 7·8% (n=903). None of the six models showed good discrimination (defined as AUROCC ≥0·70) for identifying postoperative pulmonary complications, with the Assess Respiratory Risk in Surgical Patients in Catalonia score showing the best discrimination (AUROCC 0·700 [95% CI 0·683-0·717]).

INTERPRETATION

In the pre-COVID-19 pandemic data, variability in the risk of pulmonary complications (StEP-COMPAC definition) following major abdominal surgery was poorly described by existing prognostication tools. To improve surgical safety during the COVID-19 pandemic recovery and beyond, novel risk stratification tools are required.

FUNDING

British Journal of Surgery Society.

Novel adjuvants enhance immune responses elicited by a replication-defective human cytomegalovirus vaccine in nonhuman primates

Adjuvants have long been explored to enhance vaccine efficacy. Current adjuvants approved for human vaccines are mostly studied for their ability to improve antibody responses. There remains a need for development of novel adjuvants, especially those able to enhance cell-mediated immunity (CMI). In this preclinical study we assessed the effect of two novel adjuvants, a delta inulin microparticle Advax formulated with or without a toll-like receptor 9 (TLR9) agonist CpG oligonucleotide, and a Merck & Co., Inc., Kenilworth, NJ, USA proprietary lipid nanoparticle (LNP), on immune responses elicited by V160, an experimental replication-defective human cytomegalovirus vaccine. Adult rhesus macaques were immunized with a low dose of V160 (10 units) either alone or in combination with the adjuvants as compared to those immunized with a high dose of V160 alone (100 units). While neither adjuvant conferred a significant benefit to vaccine-elicited humoral immune responses at the dose tested, both enhanced cellular immune responses to V160, where Advax promoted both CD4⁺ and CD8⁺ T cells and LNP predominantly impacted the CD4⁺ T cell response. Transcriptome analyses of peripheral blood samples demonstrated different modes of action for these adjuvants. One day post vaccination, LNP induced upregulation of a large number of genes involved in the innate immune response similar to those triggered by viral infection. In contrast, Advax did not activate any known inflammatory pathways and did not significantly impact gene expression pattern until day 7 post administration, suggesting a unique, non-inflammatory mechanism. These data warrant further exploration of Advax and LNP as adjuvants in clinical trials for vaccines desiring to elicit both humoral and T cell responses.

1971. A Randomized, Double-Blind, Placebo-Controlled Trial to Assess the Safety and Tolerability of a Respiratory Syncytial Virus (RSV) Neutralizing Monoclonal Antibody (MK-1654) in Healthy Subjects

Background

Respiratory syncytial virus (RSV) is the most common cause of lower respiratory tract infection and hospitalization in infants. Prophylaxis for RSV infection is only recommended for the highest risk infants, leaving the majority of infants unprotected. MK-1654 is a fully human monoclonal antibody targeting the RSV fusion (F) protein with Fc domain mutations to extend half-life that is being developed to provide passive immunity against RSV in infants. The safety profile, development of anti-drug antibodies (ADAs), serum neutralizing antibody (SNA) titers, and pharmacokinetics (PK) in healthy adult volunteers receiving single-ascending doses of MK-1654 was evaluated.

Methods

In this double-blinded ongoing Phase 1 study, healthy adults of non-childbearing potential (19 to 59 years) were randomized in a 3:1 ratio to receive a single dose of MK-1654 or placebo (0.9% sodium chloride injection, USP) as a bolus intramuscular injection (IM) or in an intravenous infusion (IV) for at least 2.5 hours. Dose levels included 100 and 300 mg IM, and 300, 1,000, and 3,000 mg IV. Standard methods were used to assess safety and tolerability. Serum was tested for ADAs and RSV A SNA titers at time points up to day 120 and up to day 90, respectively. MK-1654 adult PK and estimated PK for infants will be reported separately.

Results

A total of 152 subjects (male = 117, female = 35) have been enrolled (mean age = 41 years). No deaths, serious adverse events, discontinuations due to AEs, clinically significant laboratory AEs, or dose-dependent pattern of drug-related AEs were reported. Sixty-six subjects reported 181 clinical AEs (97.8% mild and 2.2% moderate in intensity). The most common AEs (≥5%) were headache, nasal congestion, vessel puncture site hemorrhage, oropharyngeal pain, rhinorrhea and nausea. No treatment emergent ADAs have been identified through time points tested. Administration of MK-1654 resulted in a dose-dependent increase in RSV A SNA titers through Day 90 (figure). Updated safety, SNA titers and ADAs will be provided.

Conclusion

MK-1654 was generally well tolerated at doses up to 300 mg IM and up to 3,000 mg IV and resulted in a dose-dependent increase in SNA titers, reflecting biologically active MK-1654 in the serum. No treatment emergent ADAs have been observed.

Disclosures

A. Aliprantis, Merck: Employee and Shareholder, Salary and stock options. D. Wolford, Merck: Employee and Shareholder, Salary and stock options. L. Caro, Merck: Employee and Shareholder, Salary and stock options. B. Maas, Merck: Employee and Shareholder, Salary and stock options. H. Ma, Merck: Employee and Shareholder, Salary and stock options. K. Vora, Merck: Employee, Salary. D. Geng, Merck: Employee and Shareholder, Salary and stock options. R. Railkar, Merck: Employee and Shareholder, Salary and stock options. A. Lee, Merck: Employee and Shareholder, Salary and stock options. L. Sterling, Merck: Investigator, Research grant. E. Lai, Merck: Employee and Shareholder, Salary and stock options.

1384. RSV Monoclonal Antibody (MK-1654) Phase 1 Pharmacokinetics (PK) in Healthy Adults and Population PK Modeling to Support Pediatric Development

Background

Respiratory syncytial virus (RSV) is the most common cause of lower respiratory tract infection and hospitalization in infants. MK-1654 is a monoclonal antibody (mAb) being developed to prevent RSV infection in infants and is undergoing evaluation in a Phase 1 study. Incorporation of YTE mutations extend its half-life to allow for dosing once every RSV season. Preliminary Phase 1 PK results and the development of a population PK model that characterizes adult PK to predict pediatric exposures are presented here.

Methods

In this double-blinded Phase 1 study, 152 healthy males and females of nonchildbearing potential aged 19–59 years were randomized in a 3:1 ratio to receive a single dose of MK-1654 or placebo as a bolus intramuscular injection (IM) or in an intravenous infusion (IV) over 2.5 hours. Dose levels included 100 mg IM, 300 mg IM, 300 mg IV, 1,000 mg IV and 3,000 mg IV. Serial serum samples were collected to measure MK-1654 PK via a validated LC/MS assay. A noncompartmental PK analysis was conducted using preliminary data from 60 subjects up to Day 150 (900 observations). A population PK model was developed to simultaneously characterize the IM and IV adult PK data and to predict pediatric PK through allometric scaling. Pediatric MK-1654 PK was predicted for several IM doses for a typical sized infant (35 weeks gestational age at birth; 4 months chronological age at dosing; 50th percentile weight).

Results

In adults, the median time to maximum concentration observed was ~6–10 days following IM injection. The apparent half-life of MK-1654 ranged from ~70–85 days after either IM or IV doses. The estimated IM bioavailability was ~71%. C_max and AUC_{0-90 days} increased dose proportionally following IV administration. MK-1654 adult PK was best characterized using a two-compartment model with first-order elimination. IM absorption was described using a first-order rate constant with lag time. Inter-individual variability was included for clearance (CL and Q), central volume (V2), and absorption rate (Ka). The pediatric model suggested apparent terminal half-life in a typical infant is shorter than adults, likely being driven by infant growth during treatment.

Conclusion

Predicted infant PK profiles support further development of MK-1654 in children.

Disclosures

B. Maas, Merck: Employee and Shareholder, Salary and stock options. A. Aliprantis, Merck: Employee and Shareholder, Salary and stock options. D. Wolford, Merck: Employee and Shareholder, Salary and stock options. G. Fayad, Merck: Employee and Shareholder, Salary and stock options. K. Vora, Merck: Employee, Salary. D. Geng, Merck: Employee and Shareholder, Salary and stock options. H. Ma, Merck: Employee and Shareholder, Salary and stock options. L. Caro, Merck: Employee and Shareholder, Salary and stock options.

1644. A Potent Broadly Neutralizing Antibody Isolated From Human Memory B-cells Binding to Conserved Site IV on the RSV F Protein

Background

Respiratory syncytial virus (RSV) infection is a major public health burden for infants and the elderly worldwide. Currently, there are no approved vaccines and only one moderately effective marketed antibody (Synagis®) for the prevention of RSV infection in high-risk infants. Sampling the human antibody repertoire has led to the realization that the RSV fusion (F) protein in its prefusion conformation is the preferred target for potent neutralizing antibodies and thus makes the protein an attractive candidate for vaccine developers.

Methods

We report the isolation of a potent and broad RSV neutralizing monoclonal antibody (mAb), which was discovered through molecular cloning of cultured RSV postfusion F protein-baited single-sorted human memory B cells. The epitope for the mAb was mapped to RSV F protein using various methods; including X-ray crystallography, alanine scan, and RSV escape mutant generation

Results

The mAb binds to both RSV pre- and postfusion F proteins at site IV and can neutralize RSV A and B laboratory strains with subnanomolar potency, superior to that of Palivizumab. Antigenic site IV is conserved between pre- and postfusion F proteins in both RSV A and B subgroups, and sequence alignment showed that the mAb-binding site was conserved in >1,000 RSV A and B clinical isolates. In vivo cotton rat studies demonstrated protection of both the upper and lower respiratory tract of antibody-infused animals challenged with either RSV A or RSV B.

Conclusion

Overall, the fully human mAb we have isolated has great potential to be developed for passive immune-prophylaxis in infants. A prevalent view of the RSV scientific community is that RSV neutralizing mAbs in human sera primarily target the prefusion F protein and predominantly bind antigenic site Ø. In contrast, our finding demonstrates that very broad and potent RSV neutralizing mAb can also recognize sites common to pre- and postfusion F proteins. Furthermore, the RSV F antigenic site IV presents a neutralizing epitope which is highly conserved. Therefore, it is worthwhile to consider site IV, in addition to site Ø, in the design of RSV subunit vaccines.

Disclosures

K. Vora, Merck: Employee, Salary. Z. Chen, Merck: Employee, Salary. H. P. Su, Merck: Employee, Salary. A. Tang, Merck: Employee, Salary. K. Cox, merck: Employee, Salary. C. Callahan, Merck: Employee, Salary. L. Zhang, Merck: Employee, Salary. S. Patel, Merck: Employee, Salary. D. Nahas, merck: Employee, Salary. M. Citron, merck: Employee, Salary. P. Cejas, merck: Employee, Salary. R. Swoyer, Merck: Employee, Salary. B. Luo, merck: Employee, Salary. M. Eddins, Merck: Employee, Salary. J. Reid, Merck: Employee, Salary. A. Fridman, Merck: Employee, Salary. J. Galli, Merck: Employee, Salary. S. Cosmi, Merck: Independent Contractor, Salary. G. Dhanasekeran, Merck: Employee, Salary. Z. Wen, Merck: Employee, Salary. X. He, Merck: Employee, Salary. D. Wang, Merck: Employee, Salary. G. Heidecker, Merck: Employee, Salary. J. Flynn, Merck: Employee, Salary. J. Cook, merck: Employee, Salary. S. Soisson, Merck: Employee, Salary. D. Casimiro, Merck: Employee, Salary. A. Bett, Merck: Employee, Salary. W. Blair, Merck: Employee, Salary. D. Distefano, Merck: Employee, Salary. C. Haines, Merck: Employee, Salary.

Metabolic Phenotypes of Response to Vaccination in Humans

Herpes zoster (shingles) causes significant morbidity in immune compromised hosts and older adults. Whereas a vaccine is available for prevention of shingles, its efficacy declines with age. To help to understand the mechanisms driving vaccinal responses, we constructed a multiscale, multifactorial response network (MMRN) of immunity in healthy young and older adults immunized with the live attenuated shingles vaccine Zostavax. Vaccination induces robust antigen-specific antibody, plasmablasts, and CD4⁺ T cells yet limited CD8⁺ T cell and antiviral responses. The MMRN reveals striking associations between orthogonal datasets, such as transcriptomic and metabolomics signatures, cell populations, and cytokine levels, and identifies immune and metabolic correlates of vaccine immunity. Networks associated with inositol phosphate, glycerophospholipids, and sterol metabolism are tightly coupled with immunity. Critically, the sterol regulatory binding protein 1 and its targets are key integrators of antibody and T follicular cell responses. Our approach is broadly applicable to study human immunity and can help to identify predictors of efficacy as well as mechanisms controlling immunity to vaccination.

Isolation of Dengue neutralizing antibodies from single cell sorted human antigen specific memory B cell cultures (VAC11P.1107)

Monitoring antigen-specific memory B cells and the antibodies they encode is important for understanding the specificity, breadth and duration of immune response to an infection or vaccination. The antibodies isolated could further help design vaccine antigens for raising relevant protective immune responses. However, developing assays to measure and isolate antigen specific memory B cells is technically challenging due to the low frequencies of these cells that exist in the circulating blood. Here we describe a method to develop a direct flow cytometric assay for the detection of Dengue envelope-specific memory B cells using a Dengue envelope specific mouse hybridoma line. We used this flow cytometry assay and a cultured B ELISPOT assay to enumerate Dengue-envelope specific B memory cells from a cohort of Dengue seropositive donors. Furthermore, we were able to culture the single sorted Dengue-envelope specific memory B-cells and differentiate them into plasma cells using cell lines expressing CD40L. The culture supernatants were assayed for antigen binding and the ability of the antibodies to neutralize the cognate dengue virus. Moreover, we successfully isolated the heavy and light Ig sequences and expressed them recombinantly as full length antibodies to reproduce the activity seen in culture supernatants. In conclusion, we have established a robust methodology to enumerate antigen-specific memory B-cells and assay their encoded antibodies for functional characterization.

Cell-mediated immune responses to ZOSTAVAX© are characterized by a boost in polyfunctional central memory T cells (VAC4P.1115)

Herpes Zoster (HZ) is a debilitating disease caused by reactivation of latent varicella-zoster virus (VZV). ZOSTAVAX is approved for the prevention of HZ and its complications in individuals 50 years and older in many countries around the world. The mechanistic immune correlates of protection and VZV antigens responsible for induction of protective CMI are not defined. To screen for dominant VZV antigens, whole blood from subjects pre-and-post ZOSTAVAX vaccination were assessed for production of IFN-ϒ, IL-2 and, TNF-α. VZV antigens eliciting high cytokine levels were used to stimulate PBMC and intracellular cytokine staining performed. We show that the VZV antigens that led to a boost in the frequency of polyfunctional CD4+ T cells (TCD4+) were IE63>IE62>gB>ORF9>gE. Polyfunctional TCD4+ produced higher levels of cytokines than monofunctional cells, and a boost in expression of cytokines was observed, post-ZOSTAVAX. Phenotypic characterization of polyfunctional TCD4+ demonstrated that they are TCM cells. Notably, we detected ORF9-specific CD8+ T cells in 52% of subjects tested, however whether these responses are cross-functional or VZV-specific needs to be determined. Overall, these studies outline the CMI that may correlate with ZOSTAVAX protection.

Approaches for sampling human antibodies for repertoire analysis and reagent development (VAC6P.953)

Purpose: Majority of vaccines rely on Human humoral response for protection. Sampling antibody response is useful for understanding protection correlates of vaccine and isolating reagent antibodies for lifecycle management. We used 3 approaches delineated below to isolate Rubella neutralizing antibodies from plasmablast B-cells separated from human subjects recently vaccinated with MMRII vaccine. Direct B cell cloning: Plasmablast B cells isolated from donors at day 7 after vaccination were used directly as templates in the RT-PCR amplification of antibody genes. Antigen-specific Fabs were isolated following molecular cloning and ELISA screening. Deep Sequencing: RNA extracted from plasmablast B cells was used as template in RT-PCR amplification. The PCR products of antibody genes were subjected to deep sequencing, retrieved antibody VH, VL and VK sequences were rank ordered based on the frequency and, top antibody sequences in each category were expressed as Fabs and tested. Immune Library Construction/Phage Display: Antibody heavy and light chain variable regions from plasmablast B cells were cloned into bacterial phage display vectors to make immune libraries, specific Fabs were identified following bio-panning. Result: All together 25 specific antibodies against Rubella were isolated through the above approaches, the best Fab ELISA binder had an EC50 of 3.5ng/mL (0.07nM). Two of the Fabs demonstrated neutralizing activity with EC50’s of 1µg/mL (20nM) and 4µg/mL (80nM).

Evaluation of human cell mediated immune responses to VZV antigens (VAC7P.993)

Zostavax© is a safe and effective vaccine against Herpes Zoster. The precise immune correlate of protection and the corresponding VZV antigens responsible for protective immunity are not currently defined. A few key pieces of data suggest that cell mediated immune responses are more important than humoral responses in the immune control over viral re-activation from latent infection. Primarily, the majority of Herpes Zoster outbreaks occur in the aging population in which antibody titers against VZV are maintained but cell mediated immune responses wane. Additionally, individuals who are immunocompromised as a result of disease or drug treatment have difficulty controlling the virus. A group of ten viral proteins of Varicella were chosen for evaluating human cell mediated immune responses. Donor samples were recruited in the following cohorts: i; Herpes Zoster outbreak within the last 5 years, ii; Subjects age 35+ with no history of Shingles or Zostavax© vaccination, and iii subjects pre and post Zostavax© vaccination. Blood samples from these donors were stimulated with the set of VZV antigens and a panel of cytokine responses from the plasma was measured. Here we show a ranking of VZV viral protein immunogenicity from these cohorts, as well as the cytokine profiles for each. These studies will help to define the viral proteins involved in generating protective cell mediated immunity correlated with protection.

An essential role for BAFF in the normal development of B cells through a BCMA-independent pathway

The B cell activating factor BAFF (BlyS/TALL-1/zTNF4) is a tumor necrosis factor (TNF)-related ligand that promotes B cell survival and binds to three receptors (BCMA, TACI, and the recently described BAFF-R). Here we report an absolute requirement for BAFF in normal B cell development. Examination of secondary lymphoid organs from BAFF-deficient mice revealed an almost complete loss of follicular and marginal zone B lymphocytes. In contrast, mice lacking BCMA had normal-appearing B lymphocyte compartments. BAFF therefore plays a crucial role in B cell development and can function through receptors other than BCMA.

BAFF-R, a newly identified TNF receptor that specifically interacts with BAFF

B cell homeostasis has been shown to critically depend on BAFF, the B cell activation factor from the tumor necrosis factor (TNF) family. Although BAFF is already known to bind two receptors, BCMA and TACI, we have identified a third receptor for BAFF that we have termed BAFF-R. BAFF-R binding appears to be highly specific for BAFF, suggesting a unique role for this ligand-receptor interaction. Consistent with this, the BAFF-R locus is disrupted in A/WySnJ mice, which display a B cell phenotype qualitatively similar to that of the BAFF-deficient mice. Thus, BAFF-R appears to be the principal receptor for BAFF-mediated mature B cell survival.

Squamous cell carcinoma presenting as a peritonsillar abscess

Peritonsillar abscess is a rare presentation of squamous cell carcinoma of the tonsil. We report two cases illustrating the need to be aware of the possibility and reinforcing the need to send all excised tissue for histopathological diagnosis.

Acute ureteral obstruction as a complication of suprapubic catheterization

Suprapubic cystostomy catheters are an important tool for the management of patients who require urinary drainage. Although complications occur after the procedure, they are usually minor. A case of acute obstruction at the ureterovesical junction caused by a suprapubic cystostomy catheter tip is presented.