High-affinity monoclonal antibodies against P-glycoprotein

Cancer patients treated with one anticancer agent often develop resistance to a broad spectrum of chemotherapeutic agents. This type of multiple drug resistance (MDR) is often accompanied by a decrease in drug accumulation and an increase in expression of a 170,000-Da plasma membrane glycoprotein (P-170) that can effectively pump various anticancer agents out of cytoplasm. A panel of 12 IgG1, IgG2a, or IgG2b monoclonal antibodies was generated against the extracellular portion of P-glycoprotein by immunizing mice with a human MDR1 gene-transfected BA3T3 fibroblast line. We have characterized two of the anti-P-glycoprotein monoclonal antibodies, 15D3 and 17F9, in some detail. Both antibodies immunoprecipitate a 170- to 180-kDa protein from MDR cells, but do not block binding of the known anti-P-glycoprotein antibody MRK16, suggesting that 15D3 and 17F9 bind to a different epitope on the extracellular domain of P-glycoprotein than MRK16. Scatchard analysis revealed that 15D3 and 17F9 had association constants of 1.3 and 1.1 x 10(8) M-1, respectively. 15D3 and 17F9 had little effect on MDR cell growth except for a minor inhibition of KB-V1 cells when the cells were incubated in the presence of vinblastine. Neither antibody inhibited the efflux of P-glycoprotein substrates from MDR cells. Because of their strong binding activity, these antibodies may be useful for diagnostic detection of MDR in patients undergoing chemotherapy or as targeting components of immunotherapeutic agents.

Susceptibility Provision Enhances Effective De-escalation (SPEED): utilizing rapid phenotypic susceptibility testing in Gram-negative bloodstream infections and its potential clinical impact

Objectives

We evaluated the performance and time to result for pathogen identification (ID) and antimicrobial susceptibility testing (AST) of the Accelerate Pheno™ system (AXDX) compared with standard of care (SOC) methods. We also assessed the hypothetical improvement in antibiotic utilization if AXDX had been implemented.

Methods

Clinical samples from patients with monomicrobial Gram-negative bacteraemia were tested and compared between AXDX and the SOC methods of the VERIGENE® and Bruker MALDI Biotyper® systems for ID and the VITEK® 2 system for AST. Additionally, charts were reviewed to calculate theoretical times to antibiotic de-escalation, escalation and active and optimal therapy.

Results

ID mean time was 21 h for MALDI-TOF MS, 4.4 h for VERIGENE® and 3.7 h for AXDX. AST mean time was 35 h for VITEK® 2 and 9.0 h for AXDX. For ID, positive percentage agreement was 95.9% and negative percentage agreement was 99.9%. For AST, essential agreement was 94.5% and categorical agreement was 93.5%. If AXDX results had been available to inform patient care, 25% of patients could have been put on active therapy sooner, while 78% of patients who had therapy optimized during hospitalization could have had therapy optimized sooner. Additionally, AXDX could have reduced time to de-escalation (16 versus 31 h) and escalation (19 versus 31 h) compared with SOC.

Conclusions

By providing fast and reliable ID and AST results, AXDX has the potential to improve antimicrobial utilization and enhance antimicrobial stewardship.

Nephrotoxicity of Vancomycin in Combination With Beta-Lactam Agents: Ceftolozane-Tazobactam vs Piperacillin-Tazobactam

BACKGROUND

Vancomycin (VAN)-associated acute kidney injury (AKI) is increased when VAN is combined with certain beta-lactams (BLs) such as piperacillin-tazobactam (TZP) but has not been evaluated with ceftolozane-tazobactam (C/T). Our aim was to investigate the AKI incidence of VAN in combination with C/T (VAN/C/T) compared with VAN in combination to TZP (VAN-TZP).

METHODS

We conducted a multicenter, observational, comparative study across the United States. The primary analysis was a composite outcome of AKI and risk, injury, failure, loss, end stage renal disease; Acute Kidney Injury Network; or VAN-induced nephrotoxicity according to the consensus guidelines. Multivariable logistic regression analysis was conducted to adjust for confounding variables and stratified Kaplan-Meir analysis to assess the time to nephrotoxicity between the 2 groups.

RESULTS

We included VAN/C/T (n = 90) and VAN-TZP (n = 284) at an enrollment ratio of 3:1. The primary outcome occurred in 12.2% vs 25.0% in the VAN-C/T and VAN-TZP groups, respectively (P = .011). After adjusting for confounding variables, VAN-TZP was associated with increased odds of AKI compared with VAN-C/T; with an adjusted odds ratio of 3.308 (95% confidence interval, 1.560-6.993). Results of the stratified Kaplan-Meir analysis with log-rank time-to-nephrotoxicity analysis indicate that time to AKI was significantly shorter among patients who received VAN-TZP (P = .004). Cox proportional hazards analysis demonstrated that TZP was consistent with the primary analysis (P = .001).

CONCLUSIONS

Collectively, our results suggest that the AKI is not likely to be related to tazobactam but rather to piperacillin, which is a component in VAN-TZP but not in VAN-C/T.

Identification of a cell surface protein with a role in stimulating human keratinocyte proliferation, expressed during development and carcinogenesis

In an attempt to define cell surface molecules with an important role in the development of squamous cell carcinomas (SCCs), we generated monoclonal antibodies (MoAbs) to a human keratinocyte cell line (FEP18-11-T1) capable of giving rise to SCCs in nude mice. MoAb 10G7 was selected for further study because it bound to a cell surface component preferentially expressed by this cell line as compared with normal human foreskin keratinocytes. This MoAb recognizes a cell surface protein (10G7 antigen) that is not detectable on normal keratinocytes in the foreskin in vivo, but whose expression is induced when the keratinocytes are dissociated from this tissue and placed in culture. Interestingly, the 10G7 antigen is downregulated upon keratinocyte differentiation in vitro. Consistent with its expression in hyper-proliferative epithelia in vitro, 10G7 antigen exhibited a classic oncofetal pattern of expression in vivo. Thus, although no reactivity was obtained with MoAb 10G7 in the epithelia of normal foreskin or cervical tissue, strong reactivity was detected in epithelia from genital lesions ranging from benign warts to invasive SCCs. Epidermis from developing fetal tissue also exhibited strong reactivity with MoAb 10G7. We have been able to demonstrate that this MoAb is capable of stimulating FEP18-11-T1 keratinocyte proliferation in vitro in a concentration-dependent manner in the absence of growth factors, suggesting that the 10G7 antigen may play an important role in regulating cellular proliferation during development and in carcinogenesis in epithelial tissues.

Use of Fluoroquinolones or Sulfamethoxazole-Trimethoprim Compared to Β-Lactams for Oral Step-Down Therapy in Hospitalized Patients With Uncomplicated Enterobacterales Bacteremia

BACKGROUND

Antibiotic therapy for uncomplicated Enterobacterales bacteremia from a urinary source has traditionally consisted of fluoroquinolones (FQs) and sulfamethoxazole-trimethoprim (SXT). However, adverse events associated with FQs and emerging antimicrobial resistance have led to alternative agents, specifically oral Β-lactams (OBLs), being utilized despite concern of subtherapeutic serum concentrations related to their low relative bioavailability.

OBJECTIVE

To compare efficacy of antibiotic therapies with bioavailability differences in patients with uncomplicated bacteremia from a urinary source.

METHODS

This was a retrospective study comparing clinical efficacy in hospitalized adult patients receiving OBL or FQ/SXT. Patients were required to receive at least 48 hours of appropriate intravenous antibiotic therapy and at least one dose of oral therapy. The primary outcome was all-cause hospital readmission within 30 days of discharge. Secondary outcomes included readmission with recurrent infectious etiology and readmission due to Clostridioides difficile infection.

RESULTS

Of 210 eligible patients, 91 received FQ/SXT and 119 received OBL. There was no difference between the groups in all-cause hospital readmission (FQ/SXT: 16.5%; OBL: 14.3%) (P = 0.660 [95% confidence interval, CI = -0.076, 0.120]) or readmission with recurrent bacteremia (FQ/SXT: 0%; OBL: 3.4%) (P = 0.135). There was a significant difference in repeat hospital admission with recurrent urinary tract infection (UTI) (FQ/SXT: 0%, OBL: 5.0%) (P = 0.037).

CONCLUSION AND RELEVANCE

OBLs appear to be non-inferior to FQ/SXT in the rate of all-cause hospital readmission within 30 days. However, OBLs may be associated with increased readmissions with recurrent UTI.

Measurement of an analog of insulin-like growth factor-I in blood plasma using a novel enzyme-linked immunosorbent assay

Long-Arg3-IGF-I (LR3IGF-I) is a synthetic analog of IGF-I that has much lower affinity for IGF-binding proteins than do native IGFs-I and -II. Comparisons of the effects of LR3IGF-I with those of IGFs-I and-II in in vitro and in vivo studies have proved useful in defining the functions of IGF-binding proteins. We have developed a sensitive noncompetitive nonisotopic assay of LR3IGF-I. Mouse IgG 1A7-F5-E5 binds an epitope that contains the substituted arginine3 in LR3IGF-I and was used as the solid phase antibody. The solution phase antibody was a rabbit immunoglobulin Nelson which binds to an epitope that is common to IGF-I and LR3IGF-I. The ELISA system was able to detect as little as 50 pg LR3IGF-I in 100 microliters and the native peptides IGFs-I and -II have less than 0.01% activity. Blood plasma from animals treated with pharmacologically active doses of this growth factor analog could be diluted 33.3-fold before assay, at which concentrations plasma had no significant effect on the assay. The ELISA response to LR3IGF-I was unaffected by the presence of IGF-binding proteins. The intra-assay and interassay coefficients of variation are 2.8 and 7.3% respectively. Recovery of LR3IGF-I added to blood plasma was approximately 90%. The ELISA was used to measure LR3IGF-I concentrations in plasma of cows treated with a pharmacologically active dose of this peptide and the results were compared with those obtained by a previously established LR3IGF-I RIA that requires size exclusion chromatography of plasma under acidic conditions to eliminate IGF-binding protein artefacts from the RIA. There was a positive correlation between results obtained by the two assays. The LR3IGF-I ELISA permits discrimination between the exogenous synthetic IGF-I analog and the endogenous native IGFs-I and -II in animals treated with this growth factor without the need for radioiodination of LR3IGF-I and elimination of the requirement for extraction of plasma before assay.

Evaluation of the Impact of a Student Pharmacist-Supported Program to Improve Hospital-Based Quality Measures

Background. Although previous studies have demonstrated positive impact of student pharmacists on clinical interventions, no published studies to date have demonstrated the specific impact of student pharmacists on improving National Hospital Inpatient Quality Measures (NHIQM). Objective. To evaluate the impact of a student pharmacist-supported program targeted at improving the venous thromboembolism (VTE) quality measures set forth by the NHIQM. Methods. Retrospective review of VTE quality measure compliance at a community nonteaching hospital. During this time, student pharmacists supported a VTE prophylaxis program that evaluated admitted patients for chemical or mechanical prophylaxis needs. Compliance to VTE quality measures were also evaluated by a trained medical data abstractor based on criteria given by the Joint Commission. Results. Four major NHIQM criteria for VTE were selected for evaluation. National and state averages were compared to the overall hospital averages across various timeframes. The student-supported program demonstrated consistently high performance for the VTE-1 and VTE-5 measures. Conclusion. Student pharmacists have opportunities in improving inpatient quality measures and can play a significant role in patient care through thorough evaluation and intervention.

1986. Rapid Identification and Antimicrobial Susceptibility Testing Utilizing the Accelerate Pheno™ System for Gram-Negative Bloodstream Infections and Its Potential Clinical Impact

Background

This study’s aim was to compare pathogen identification (ID) and antimicrobial susceptibility testing (AST) result turnaround times of the Accelerate Pheno™ system (AXDX) against current standard methods (SOC). Secondarily, we assessed whether its implementation for positive blood cultures (PBC) with monomicrobial Gram-negative bacilli could provide theoretical improvement in time to active and optimal antibiotic therapy.

Methods

Over 3 months, Gram-negative PBC from 114 patients, including 29 pediatric patients, were identified for the study. Blood cultures were tested on both the Verigene® and AXDX platforms in tandem after flagging positive on the BACTEC® FX system. Isolates were tested on the Bruker MALDI Biotyper® system for ID and VITEK® 2 system (GN73 cards) for AST. Patient charts were then retrospectively evaluated to calculate time to active and optimal therapy. On comparing time to results (ID and AST) for AXDX with SOC, timing calculations to mimic setup and reporting times for tests and results were included.

Results

From time of blood culture positivity, mean time to ID averaged 36.3 hours for MALDI-TOF MS, 4.5 hours for the Verigene^® system and 3.6 hours for AXDX, while the mean time to AST averaged 35.8 hours for the VITEK^® 2 system and 8.9 hours for AXDX. Thirty-nine percent (45/114) of patients were not on active therapy at time of positive blood culture. Of these, 29 were put on active therapy within a mean of 21 hours (range: 9.3 hours to 5.6 days), such that 25% of patients could have been put on active therapy sooner had AXDX AST results been available clinically for action by a physician or stewardship team. Similarly, 34 were put on optimal therapy within a mean of 1.3 days (range: 9.3 hours to 5.6 days). Thus, 30% of patients could have had therapy optimized earlier had AXDX AST results been available.

Conclusion

Overall, the Accelerate Pheno™ system is a reliable new diagnostic modality that has the potential to significantly reduce time to PBC ID and AST results, as well as time to active and optimal therapy, thus aiding in effective antimicrobial stewardship. Prospective studies evaluating the clinical impact of AXDX on patient outcomes are needed and planned.

Disclosures

J. Schneider, Accelerate Diagnostics: Investigator, kits and data management and Research support.