Pharmacokinetics and pharmacodynamics of monoclonal antibodies: concepts and lessons for drug development

Obesity and Pediatric Drug Development

There is a lack of dosing guidelines for use in obese children. Moreover, the impact of obesity on drug safety and clinical outcomes is poorly defined. The paucity of information needed for the safe and effective use of drugs in obese patients remains a problem, even after drug approval. To assess the current incorporation of obesity as a covariate in pediatric drug development, the pediatric medical and clinical pharmacology reviews under the Food and Drug Administration (FDA) Amendments Act of 2007 and the FDA Safety and Innovation Act (FDASIA) of 2012 were reviewed for obesity studies. FDA labels were also reviewed for statements addressing obesity in pediatric patients. Forty-five drugs studied in pediatric patients under the FDA Amendments Act were found to have statements and key words in the medical and clinical pharmacology reviews and labels related to obesity. Forty-four products were identified similarly with pediatric studies under FDASIA. Of the 89 product labels identified, none provided dosing information related to obesity. The effect of body mass index on drug pharmacokinetics was mentioned in only 4 labels. We conclude that there is little information presently available to provide guidance related to dosing in obese pediatric patients. Moving forward, regulators, clinicians, and the pharmaceutical industry should consider situations in drug development in which the inclusion of obese patients in pediatric trials is necessary to facilitate the safe and effective use of new drug products in the obese pediatric population.

Activatable fluorescent probes in fluorescence-guided surgery: Practical considerations

Fluorescence-guided imaging during surgery is a promising technique that is increasingly used to aid surgeons in identifying sites of tumor and surgical margins. Of the two types of fluorescent probes, always-on and activatable, activatable probes are preferred because they produce higher target-to-background ratios, thus improving sensitivity compared with always-on probes that must contend with considerable background signal. There are two types of activatable probes: 1) enzyme-reactive probes that are normally quenched but can be activated after cleavage by cancer-specific enzymes (activity-based probes) and 2) molecular-binding probes which use cancer targeting moieties such as monoclonal antibodies to target receptors found in abundance on cancers and are activated after internalization and lysosomal processing (binding-based probes). For fluorescence-guided intraoperative surgery, enzyme-reactive probes are superior because they can react quickly, require smaller dosages especially for topical applications, have limited side effects, and have favorable pharmacokinetics. Enzyme-reactive probes are easier to use, fit better into existing work flows in the operating room and have minimal toxicity. Although difficult to prove, it is assumed that the guidance provided to surgeons by these probes results in more effective surgeries with better outcomes for patients. In this review, we compare these two types of activatable fluorescent probes for their ease of use and efficacy.

Ibalizumab Targeting CD4 Receptors, An Emerging Molecule in HIV Therapy

The HIV infection is responsible for the most devastating global pandemic of the last century. More than 39 million people have died of HIV/AIDS since 1981. The development of the antiretroviral (ARV) treatment begins with the discovery of zidovudine a nucleoside reverse transcriptase inhibitor. This breakthrough was followed by other ARV drug classes and representatives. Presently, HIV treatment employs 27 ARV representatives belonging to five different classes. Despite the proven benefits of ARV treatment and its long-term control of the HIV infection, there is an increasing concern about the numerous adverse effects and resistance to current ARV drugs. Therefore, the new HIV treatment strategies focus on the development of new ARV agents with a high genetic barrier to resistance and low toxicity. Monoclonal antibodies (MAbs) belong to a new drug class with encouraging results in the treatment of cancer, autoimmune disorders and most recently against HIV infection. The advantages of using MAbs for HIV treatment are related to their antiviral effect, lack of toxicity, good resistance profile, additional synergy with other ARV drug classes and ability to restore CD4 T-cell responses. The current article is a short summary of ibalizumab, an anti-CD4 monoclonal antibody that interferes with HIV viral entry. Current studies on ibalizumab have underlined its antiviral potential, minimal adverse effects, and lack of crossed resistance with other ARV agents thus supporting its further therapeutic use in multidrug resistant HIV-infected patients.

The anti-tumor effect of RANKL inhibition in malignant solid tumors - A systematic review

At present, accumulating evidence suggests that inhibition of receptor activator of nuclear factor kappa-B ligand (RANKL) does not only induce an increase in bone mass and strength, but also has anti-tumor effects. Denosumab, an antibody targeting RANKL, is used to treat osteoporosis and to prevent skeletal related events (SREs) in patients with bone metastases originating from solid tumors. However, expression of RANKL and its receptor activator of nuclear factor kappa-B (RANK) is not solely restricted to cells involved in homeostasis of the bone and RANKL-RANK signalling appears to play a substantial role in many other processes in the body like mammary physiology, mammary tumorigenesis and the immune system. In pre-clinical models, RANKL inhibition has been shown to reduce skeletal tumor burden and distant metastases as well as to decrease mammary carcinogenesis. Clinically, RANKL inhibition improves bone-metastasis free survival in patients with prostate cancer and disease-free survival in patients with breast cancer. In addition, RANKL treatment may form a preventative strategy in patients at high risk for malignancies of the breast. Current clinical studies are evaluating the effect of denosumab on survival, the immune system and other biomarkers into a greater extent. To that purpose, a systematic review of the literature was performed and a narrative review synthesized, describing the present pre-clinical and clinical evidence of an anti-tumor effect of RANKL inhibition and the potential role of the immune system as one of the underlying mechanisms.

The body composition profile is associated with response to anti-TNF therapy in Crohn's disease and may offer an alternative dosing paradigm

BACKGROUND

Anti-tumour necrosis factor (TNF)s form a major part of therapy in Crohn's disease and have a primary nonresponse rate of 10%-30% and a secondary loss of response rate of 5% per year. Myopenia is prevalent in Crohn's disease and is measured using body composition analysis tools.

AIM

To test the hypothesis that body composition can predict outcomes of anti-TNF primary nonresponse and secondary loss of response.

METHODS

Between January 2007 and June 2012, 106 anti-TNF naïve patients underwent anti-TNF therapy for Crohn's disease with body composition parameters analysed using CT scans to estimate body fat-free mass. The outcome measures were primary nonresponse and secondary loss of response. COX-regression analysis was used with 3 year follow-up data.

RESULTS

A total of 106 patients were included for analysis with 26 (24.5%) primary nonresponders and 29 (27.4%) with secondary loss of response to anti-TNF therapy. Sex-specific cut-offs for muscle and fat were ascertained by stratification analysis. On univariate analysis, primary nonresponse was associated with low albumin (OR 0.94; 0.88-0.99, P = .04) and presence of myopenia (OR 4.69; 1.83-12.01, P = .001) when taking into account patient's medical therapy, severity of disease and body composition. On multivariate analysis, presence of myopenia was associated with primary nonresponse (OR 2.93; 1.28-6.71, P = .01). Immunomodulator therapy was associated with decreased secondary loss of response (OR 0.48; 0.23-0.98, P = .04). BMI was poorly correlated with lean body mass (r² = 0.15, P = .54).

CONCLUSIONS

In this cohort study, body composition profiles did not correlate well with BMI. Myopenia was associated with primary nonresponse with potential implications for dosing and serves as an explanation for pharmacokinetic failure.

Potential Sources of Inter-Subject Variability in Monoclonal Antibody Pharmacokinetics

Understanding inter-subject variability in drug pharmacokinetics and pharmacodynamics is important to ensure that all patients attain suitable drug exposure to achieve efficacy and avoid toxicity. Inter-subject variability in the pharmacokinetics of therapeutic monoclonal antibodies (mAbs) is generally moderate to high; however, the factors responsible for the high inter-subject variability have not been comprehensively reviewed. In this review, the extent of inter-subject variability for mAb pharmacokinetics is presented and potential factors contributing to this variability are explored and summarised. Disease status, age, sex, ethnicity, body size, genetic polymorphisms, concomitant medication, co-morbidities, immune status and multiple other patient-specific details have been considered. The inter-subject variability for mAb pharmacokinetics most likely depends on the complex interplay of multiple factors. However, studies aimed at investigating the reasons for the inter-subject variability are sparse. Population pharmacokinetic models and physiologically based pharmacokinetic models are useful tools to identify important covariates, aiding in the understanding of factors contributing to inter-subject variability. Further understanding of inter-subject variability in pharmacokinetics should aid in development of dosing regimens that are more appropriate.

Serum Adalimumab Levels Predict Successful Remission and Safe Deintensification in Inflammatory Bowel Disease Patients in Clinical Practice

BACKGROUND

Little is known about the association between the pharmacokinetic features of adalimumab (ADL) and disease outcome in patients with inflammatory bowel disease (IBD).

AIMS

To assess the association between random serum ADL levels and clinical or biochemical remission with clinical decision making in daily practice according to these levels; and to determine the cutoff value for successful dose reduction in patients with IBD treated with ADL.

METHODS

We conducted a prospective observational study of patients with IBD who received long-term maintenance therapy with ADL.

RESULTS

Data were available for 157 serum samples from 87 patients. Serum ADL levels were associated with clinical remission: median 9.2 versus 6.0 μg/mL for patients with Crohn's disease with active disease (P = 0.009) and 14.4 versus 5.2 μg/mL in patients with ulcerative colitis with active disease (P = 0.002). Serum ADL levels were 9.2 μg/mL for patients with a normal C-reactive protein value (<5 mg/L) and 5.2 μg/mL for patients with a high C-reactive protein value (P = 0.002). ADL levels were significantly associated with normal fecal calprotectin value (<80 ng/g) (10.8 versus 7.6 μg/mL, respectively, P = 0.038). Serum ADL levels were significantly associated with successful deintensification, over a 6-month period of clinical follow-up, compared with the group in which doses remained unchanged (area under the curve 0.88; 95% confidence interval, 0.81-0.95; P < 0.001), with a cutoff value for successful deintensification of 12.2 μg/mL.

CONCLUSIONS

Higher ADA levels were significantly associated with clinical and biochemical remission. Our results, which were obtained under conditions of daily clinical practice, suggest that an ADL cutoff of 12.2 μg/mL could be appropriate for successful dose reduction in patients with IBD treated with ADL.

Fixed Dosing of Monoclonal Antibodies in Oncology

Most monoclonal antibodies in oncology are administered in body-size-based dosing schedules. This is believed to correct for variability in both drug distribution and elimination between patients. However, monoclonal antibodies typically distribute to the blood plasma and extracellular fluids only, which increase less than proportionally with the increase in body weight. Elimination takes place via proteolytic catabolism, a nonspecific immunoglobulin G elimination pathway, and intracellular degradation after binding to the target. The latter is the primary route of elimination and is related to target expression levels rather than body size. Taken together, the minor effects of body size on distribution and elimination of monoclonal antibodies and their usually wide therapeutic window do not support body-size-based dosing. We evaluated effects of body weight on volume of distribution and clearance of monoclonal antibodies in oncology and show that a fixed dose for most of these drugs is justified based on pharmacokinetics. A survey of the savings after fixed dosing of monoclonal antibodies at our hospital showed that fixed dosing can reduce costs of health care, especially when pooling of preparations is not possible (which is often the case in smaller hospitals). In conclusion, based on pharmacokinetic parameters of monoclonal antibodies, there is a rationale for fixed dosing of these drugs in oncology. Therefore, we believe that fixed dosing is justified and can improve efficiency of the compounding. Moreover, drug spillage can be reduced and medication errors may become less likely.

IMPLICATIONS FOR PRACTICE

The currently available knowledge of elimination of monoclonal antibodies combined with the publicly available data from clinical trials and extensive population pharmacokinetic (PopPK) modeling justifies fixed dosing. Interpatient variation in exposure is comparable after body weight and fixed dosing and most monoclonal antibodies show relatively flat dose-response relationships. For monoclonal antibodies, this results in wide therapeutic windows and no reduced clinical efficacy after fixed dosing. Therefore, we believe that fixed dosing at a well-selected dose can increase medication safety and help in reduction of costs of health care without the loss of efficacy or safety margins.

Interactions Between Therapeutic Proteins and Small Molecules: The Shared Role of Perpetrators and Victims

Therapeutic proteins (TPs) are becoming increasingly important as therapeutic agents. A consequence of expanding their clinical indications is coadministration with well-established small-molecule drugs (sMDs), which could lead to unpredictable effects. According to the existing regulatory guidance, the development of an sMD includes the evaluation of potential drug-drug interactions (DDIs). For TPs, only a few drug interaction studies have been published. Limited clinically relevant models, long half-lives, and complex elimination pathways are among the associated difficulties.

Tumor necrosis factor inhibitors in psoriatic arthritis

INTRODUCTION

Psoriatic arthritis (PsA) is a chronic inflammatory disease that can result in significant disability. With the emergence of tumor necrosis factor inhibitors (TNFi), therapeutic outcomes in PsA have improved substantially. The clinical efficacy and the inhibition of radiographic progression demonstrated by TNFi have transformed the management of PsA. However, there is still an unmet need for a subset of patients who do not respond adequately to TNFi. Areas covered: This review provides an overview of the pharmacokinetics of TNFi, the efficacy of TNFi in PsA, and the role of immunogenicity of TNFi in the treatment of PsA. In addition, we address the use of TNFi in the setting of other medications utilized in the treatment of PsA and the potential future role of biosimilars. Expert commentary: Monoclonal antibodies exhibit complex and widely variable pharmacokinetics. The study of factors that can affect the pharmacokinetics, such as immunogenicity, is valuable to further define and understand the use of TNFi in PsA, especially in the subset of patients who do not respond adequately to these agents or lose effectiveness over time.

Golimumab for moderate to severe ulcerative colitis

Golimumab (GLM) is a subcutaneously administered human anti-tumor necrosis factor (TNF) agent that has been approved by the regulatory authorities for the treatment of moderate to severe ulcerative colitis (UC) in 2013. Areas covered: Maintained clinical remission rates up to 50% have been shown in UC patients receiving GLM, and higher GLM serum concentrations have been associated with improved clinical outcomes. Approximately 50% of UC patients do not respond to induction therapy with GLM, and up to 40% of GLM responders will lose response over time. In most patients, loss of response is associated with low serum GLM concentrations, which suggests insufficient exposure to GLM. Low GLM serum concentrations may be avoided by therapeutic drug monitoring. Expert commentary: So far, the therapeutic window for GLM has not yet been defined, but options to dose increase GLM based on therapeutic drug monitoring might result in improved clinical outcome and higher success rates.

Therapeutic Drug Monitoring of Golimumab in the Treatment of Ulcerative Colitis

Ulcerative colitis (UC) is a relapsing-remitting chronic inflammatory disorder affecting the mucosal surface in a continuous manner from the rectum through part of, or the entire, colon. Patients with severe disease and those who become refractory or intolerant to corticosteroids and/or immunosuppressants, require treatment with biologic agents that target tumor necrosis factor-α (TNF). Golimumab, a fully human monoclonal antibody, is the latest TNF antagonist to get approved for the treatment of moderate-to-severe UC. Subcutaneously administered golimumab induces and maintains clinical response, remission, and mucosal healing. Serum concentrations of golimumab are associated with response to therapy, as patients with higher drug exposure are more likely to achieve these outcomes. Since various patient and disease-related factors were shown to influence the pharmacokinetics of TNF antagonists, drug exposure may be variable over time and between patients, affecting success of therapy. A major contributing factor is immunogenicity, with development of anti-drug antibodies (ADAb) and an accelerated clearance of drug as a result. Although there is a growing body of evidence to support therapeutic drug monitoring (TDM) for infliximab and adalimumab, two other TNF antagonists, only limited data is available for golimumab. In addition, the clinically important drug exposure thresholds are not widely known, which has limited the use of TDM for golimumab in clinical practice. This review summarizes available data regarding the use of golimumab for UC, with emphasis on the pharmacokinetics, exposure-response relationship, and the role of TDM in optimizing therapy.

Is there potential for therapeutic drug monitoring of biologic agents in rheumatoid arthritis?

The use of biologics has significantly changed the management of rheumatoid arthritis over the last decade, becoming the cornerstone treatment for many patients. The current therapeutic arsenal consists of just under 10 biologic agents, with four different mechanisms of action. Several studies have demonstrated a large interindividual pharmacokinetic variability, which translates to unpredictability in clinical response among individuals. The present review focuses on the pharmacokinetics and pharmacodynamics of biologic agents approved for rheumatoid arthritis. The literature relating to their concentration-effect relationship and the use of pharmacokinetic-pharmacodynamic modelling to optimize drug regimens is analysed. Due to the scarcity and complexity of these studies, the current dosing strategy is based on clinical indexes/aspects. In general, dose individualization for biologics should be implemented increasingly in clinical practice as there is a direct benefit for treated rheumatoid arthritis patients. Moreover, there is an indirect benefit in terms of cost-effectiveness.

Drug Development of Therapeutic Monoclonal Antibodies

Monoclonal antibodies (MAbs) have become a substantial part of many pharmaceutical company portfolios. However, the development process of MAbs for clinical use is quite different than for small-molecule drugs. MAb development programs require careful interdisciplinary evaluations to ensure the pharmacology of both the MAb and the target antigen are well-understood. Selection of appropriate preclinical species must be carefully considered and the potential development of anti-drug antibodies (ADA) during these early studies can limit the value and complicate the performance and possible duration of preclinical studies. In human studies, many of the typical pharmacology studies such as renal or hepatic impairment evaluations may not be needed but the pharmacokinetics and pharmacodynamics of these agents is complex, often necessitating more comprehensive evaluation of clinical data and more complex bioanalytical assays than might be used for small molecules. This paper outlines concerns and strategies for development of MAbs from the early in vitro assessments needed through preclinical and clinical development. This review focuses on how to develop, submit, and comply with regulatory requirements for MAb therapeutics.

Use of denosumab in a dialysis patient with bone metastases from breast cancer and hepatorenal polycystic disease: a case report

Cancer patients with severe renal dysfunction represent a challenge for the physician. This is the first case report on the use of denosumab in a dialysis patient with bone metastases. We present the clinical case of a 45-year-old woman who had hepatorenal polycystic disease, diagnosed during childhood, and stage IV chronic kidney failure at the time of breast cancer diagnosis. Three years after surgery plus adjuvant hormonal therapy she suffered a further worsening of renal function, requiring dialysis, and very advanced bone metastasis in the hip with severe pain. As pamidronate was the only bone agent available in the center, she received it for 4 months (before a dialysis session), during which time the bone metastases stabilized. In March 2014, the patient switched to denosumab (which had become available in the center), and continued with hormone therapy. Seven months after denosumab initiation, the patient had almost complete pain relief, and the bone metastases exhibited radiological improvement. The tolerability was excellent, without any related adverse event. There were no changes in albumin-adjusted serum calcium, serum phosphorus, and intact parathyroid hormone, except for a transient and mild hypocalcemia at 3 months and an increase in intact parathyroid hormone levels, which required adjustment of vitamin D analog dose. Denosumab can be administered to prevent skeletal-related events in patients with bone metastasis from solid tumors and severely impaired renal function, even in those requiring dialysis. In this particular patient, the safety was good.

Optimizing Treatment with TNF Inhibitors in Inflammatory Bowel Disease by Monitoring Drug Levels and Antidrug Antibodies

BACKGROUND

Biological tumor necrosis factor (TNF) inhibitors have revolutionized the treatment of inflammatory bowel disease and redefined treatment goals to include mucosal healing. Clinicians are faced with challenges such as inadequate responses, treatment failures, side effects, and high drug costs. The objective is to review optimization of anti-TNF therapy by use of personalized treatment strategies based on circulating drug levels and antidrug antibodies (Abs), i.e. therapeutic drug monitoring (TDM). Furthermore, to outline TDM-related pitfalls and their prevention.

METHODS

Literature review.

RESULTS

Circulating anti-TNF drug trough level is a marker for the pharmacokinetics (PK) of TNF inhibitors. Because of a number of factors, including antidrug antibodies, PK varies between and within patients across time leading to variable clinical outcomes. Differences in intestinal inflammatory phenotype influencing the pharmacodynamic (PD) responses to TNF inhibitors also affect treatment outcomes. As an alternative to handling anti-TNF-treated patients by empiric strategies, TDM identifies underlying PK and PD-related reasons for treatment failure and aids decision making to secure optimal clinical and economic outcomes. Although promising, evidence does not the support use of TDM to counteract treatment failure in quiescent disease. Use of TDM is challenged by methodological biases, difficulties related to differentiation between PK and PD problems, and temporal biases due to lack of chronology between changes in PK versus symptomatic and objective disease activity manifestations. Biases can be accommodated by knowledgeable interpretation of results obtained by validated assays with clinically established thresholds, and by repeated assessments over time using complimentary techniques.

CONCLUSIONS

TDM-guided anti-TNF therapy at treatment failure has been brought from bench to bedside.

Pharmacokinetics, Pharmacodynamics, Safety, and Tolerability of ASP2408, a Potent Selective T-Cell Costimulation Modulator After Single and Multiple Ascending Doses in Healthy Volunteers and RA Patients

ASP2408 is a next-generation anti-cytotoxic T lymphocyte antigen-4 fusion protein engineered for improved CD86 binding affinity as a treatment for rheumatoid arthritis (RA). In 72 healthy subjects (n = 6/treatment), ASP2408 was administered as single ascending doses intravenously at 0.003 to 10.0 mg/kg or subcutaneously at 0.3 to 3.0 mg/kg. It showed decreased clearance and prolonged half-life with increasing doses, consistent with target-mediated disposition. The apparent bioavailability was 36.3%-56.7% across single subcutaneous doses. Sixteen RA patients (n = 8/treatment) on stable methotrexate received 3 × 3.0 mg/kg subcutaneously every 4 weeks or every 2 weeks. Similar to single-dose treatment, ASP2408 concentrations peaked 2 to 3 days postdose, with a median t1/2 of approximately 8 days. Using CD86 receptor occupancy (RO) as a mechanistic biomarker, ASP2408 demonstrated dose-dependent binding to its target. ASP2408 3.0 mg/kg subcutaneously every 4 weeks and every 2 weeks led to a mean %CD86 RO ≥ 74.7% and ≥ 81.5%, respectively, within each dosing interval. ASP2408 was well tolerated across studies with no evidence of dose-limiting toxicity or clinically significant changes in clinical laboratory test results, vital signs, or 12-lead electrocardiograms. ASP2408 elicited antidrug antibodies in the majority of patients, but with no clinical sequelae.

Classification model of amino acid sequences prone to aggregation of therapeutic proteins

Background

Total body clearance of biological drugs is for the most part dependent on the receptor mechanisms (receptor mediated clearance) and the concentration of antibodies aimed at administered drug – anti-drug-antibodies (ADA). One of the significant factors that induces the increase of ADA level after drug administration could be the aggregates present in the finished product or formed in the organism. Numerous attempts have been made to identify the sequence fragments that could be responsible for forming the aggregates – aggregate prone regions (APR).

Purpose

The aim of this study was to find physiochemical parameters specific to APR that would differentiate APR from other sequences present in therapeutic proteins.

Methods

Two groups of amino acid sequences were used in the study. The first one was represented by the sequences separated from the therapeutic proteins (n = 84) able to form APR. A control set (CS) consisted of peptides that were chosen based on 22 tregitope sequences.

Results

Classification model and four classes (A, B, C, D) of sequences were finally presented. For model validation Cooper statistics was presented.

Conclusions

The study proposes a classification model of APR. This consists in a distinction of APR from sequences that do not form aggregates based on the differences in the value of physicochemical parameters. Significant share of electrostatic parameters in relation to classification model was indicated.

Antibodies to adalimumab are associated with future inflammation in Crohn's patients receiving maintenance adalimumab therapy: a post hoc analysis of the Karmiris trial

INTRODUCTION

Data on immunogenicity to adalimumab (ADL) therapy in patients with IBD is limited. We performed additional analyses on the Karmiris cohort using the homogeneous mobility shift assay (HMSA) focusing on the inter-relationship of serum ADL concentration, antibodies-to-adalimumab (ATA), inflammatory markers and sustained response.

METHODS

536 prospectively collected serum samples were available for analysis of ADL concentration and ATA using HMSA. We studied the role of week 4 serum ADL concentration and immunomodulator (IMM) use on ATA formation with a Cox proportional hazards model. Mixed model repeated measures analysis was performed to assess the independent effects of serum ADL concentration and ATA on C-reactive protein (CRP) and response.

RESULTS

ATA was detected in 20% of patients after a median of 34 (12.4-60.5) weeks. ATA-positive samples correlated with lower serum ADL concentration (p<0.001). Cox regression modelling showed that week 4 ADL concentration of <5 µg/mL significantly increased the future risk of ATA formation (HR=25.1; 95% CI 5.6 to 111.9; p=0.0002) and that IMM co-treatment prevented ATA formation (HR=0.23; 95% CI 0.06 to 0.86; p=0.0293). Regression modelling showed a negative correlation between CRP and ADL concentration (p=0.0001) and a positive one with ATA (p=0.0186). The model revealed that both lower serum ADL concentration and ATA were independently associated with future CRP (p=0.0213 and p=0.0013 respectively). ATA positivity was associated with discontinuation of ADL because of loss or response (OR=3.04; 95% CI 1.039 to 9.093; p=0.034).

CONCLUSIONS

ATA were detected in 20% of patients. Risk of ATA formation increased with lower early serum ADL concentration and in patients not on IMM. ATA and ADL were strongly associated with higher future CRP level and discontinuation of ADL.

Pharmacokinetics and Tolerability of a Dual Variable Domain Immunoglobulin ABT-981 Against IL-1α and IL-1β in Healthy Subjects and Patients With Osteoarthritis of the Knee

The interleukin (IL)-1 family of proinflammatory cytokines are thought to play a significant role in the structural progression of osteoarthritis and its associated symptoms. IL-1α and IL-1β are 2 distinct cytokines found in the cartilage, synovial membrane, and synovial fluid of patients with osteoarthritis. The aim of these studies was to evaluate the pharmacokinetics of ABT-981, a dual variable domain immunoglobulin (DVD-Ig) capable of simultaneously binding IL-1α and IL-1β, in healthy subjects and patients with osteoarthritis of the knee. Fifty-six healthy adult subjects were randomized to receive single doses of ABT-981 intravenously (0.3, 1, 3, or 10 mg/kg), subcutaneously (0.3, 1, 3 mg/kg), or matching placebo in a 3:1 ratio. Thirty-six patients with osteoarthritis of the knee were randomized to receive 4 subcutaneous ABT-981 doses of 0.3, 1, or 3 mg/kg administered every 2 weeks, 3 subcutaneous doses of ABT-981 3 mg/kg every 4 weeks, or matching placebo in a 7:2 active:placebo ratio. ABT-981 behaved similarly to conventional monoclonal antibodies following single or multiple doses with mean maximum serum concentrations 2 to 9 days after subcutaneous doses, mean terminal half-lives of 10 to 14 days, and an absolute subcutaneous bioavailability of 46%. Exposure of ABT-981 was approximately linear following single or multiple doses every 2 weeks with monoexponential decline of terminal-phase concentrations. The most common adverse events associated with ABT-981 were diarrhea and headache in healthy subjects and injection site erythema in subjects with osteoarthritis of the knee. Decreased absolute neutrophil counts were observed in response to ABT-981 administration.

ImmunoPET Imaging of Insulin-Like Growth Factor 1 Receptor in a Subcutaneous Mouse Model of Pancreatic Cancer

The role of insulin-like growth factor-1 receptor (IGF-1R) in cancer tumorigenesis was established decades ago, yet there are limited studies evaluating the imaging and therapeutic properties of anti-IGF-1R antibodies. Noninvasive imaging of IGF-1R may allow for optimized patient stratification and monitoring of therapeutic response in patients. Herein, this study reports the development of a Zirconium-89 (⁸⁹Zr)-labeled anti-IGF-1R antibody (⁸⁹Zr-Df-1A2G11) for PET imaging of pancreatic cancer. Successful chelation and radiolabeling of the antibody resulted in a highly stable construct that could be used for imaging IGF-1R expressing tumors in vivo. Western blot and flow cytometry studies showed that MIA PaCa-2, BxPC-3, and AsPC-1 pancreatic cancer cell lines expressed high, moderate, and low levels of IGF-1R, respectively. These three pancreatic cancer cell lines were subcutaneously implanted into mice. By employing the PET imaging technique, the tumor accumulation of ⁸⁹Zr-Df-1A2G11 was found to be dependent on the level of IGF-1R expression. Tumor accumulation of ⁸⁹Zr-Df-1A2G11 was 8.24 ± 0.51, 5.80 ± 0.54, and 4.30 ± 0.42 percentage of the injected dose (%ID/g) in MIA PaCa-2, BxPC-3, and AsPC-1-derived tumor models at 120 h postinjection, respectively (n = 4). Biodistribution studies and ex vivo immunohistochemistry confirmed these findings. In addition, ⁸⁹Zr-labeled nonspecific human IgG (⁸⁹Zr-Df-IgG) displayed minimal uptake in IGF-1R positive MIA PaCa-2 tumor xenografts (3.63 ± 0.95%ID/g at 120 h postinjection; n = 4), demonstrating that ⁸⁹Zr-Df-1A2G11 accumulation was highly specific. This study provides initial evidence that our ⁸⁹Zr-labeled IGF-1R-targeted antibody may be employed for imaging a wide range of malignancies. Antibodies may be tracked in vivo for several days to weeks with ⁸⁹Zr, which may enhance image contrast due to decreased background signal. In addition, the principles outlined in this study can be employed for identifying patients that may benefit from anti-IGF-1R therapy.

How Will Evolving Future Therapies and Strategies Change How We Position the Use of Biologics in Moderate to Severely Active Inflammatory Bowel Disease

Several biological agents have been added to our armamentarium of treatment options for moderate to severely active inflammatory bowel diseases, and this number is expected to only increase in the near future. With our growing understanding of disease mechanisms and pharmacokinetics, we are now able to target several mechanisms of action to achieve key endpoints (steroid-free remission and mucosal healing) associated with improved long-term disease-related outcomes. In this context, concerns arise regarding the optimal positioning of currently available biologics and key biologics in development. In this review, we will discuss the currently available evidence for comparative effectiveness of biological agents approved for the use in moderate to severely active inflammatory bowel diseases, with a focus on practical considerations to be made when using these agents in practice. We will further review novel biological agents and small molecule inhibitors in development and discuss future opportunities through which providers may personalize treatment decisions to achieve optimal treatment outcomes.

Population pharmacokinetics and exposure-response relationship of amatuximab, an anti-mesothelin monoclonal antibody, in patients with malignant pleural mesothelioma and its application in dose selection

PURPOSE

To characterize amatuximab pharmacokinetics (PK) and the relationship of amatuximab exposure with response in patients with unresectable malignant pleural mesothelioma (MPM) receiving amatuximab with pemetrexed and cisplatin.

METHODS

A nonlinear mixed effects PK model was built using data from all of the amatuximab studies conducted to date. Patients received amatuximab alone or in combination with chemotherapy. The influence of demographic, laboratory and disease characteristics on PK parameters was assessed. Exposure-response analyses explored relationships between amatuximab exposure and overall survival (OS), progression-free survival (PFS) and safety. Alternative amatuximab dosing regimens were explored with simulations using population PK and parametric survival models.

RESULTS

Amatuximab PK was best described by a two-compartment model with parallel linear and nonlinear elimination pathways. Body weight and an antidrug antibodies reaction with the titer >64 affected volume of distribution and clearance, respectively. Exposure-response analyses demonstrated that the amatuximab exposure (C min) showed a significant effect on OS (log-rank test, P = 0.0202). For patients with amatuximab C min above the median (38.2 μg/mL), the median OS was 583 days (90 % CI 418 -NE). For patients with C min ≤ 38.2 μg/mL, the median OS was 375 days (90 % CI 325-486). The amatuximab exposure showed similar significant effect on PFS. Exposure-response analysis for adverse events did not reveal any relationship.

CONCLUSIONS

In patients with MPM, higher amatuximab exposure in combination with chemotherapy was shown to be associated with longer OS, supporting evaluation of more frequent dosing in future trials to achieve higher exposure and subsequently longer OS.

Clinical Decision Support Tools: The Evolution of a Revolution

Dashboard systems for clinical decision support integrate data from multiple sources. These systems, the newest in a long line of dose calculators and other decision support tools, utilize Bayesian approaches to fully individualize dosing using information gathered through therapeutic drug monitoring. In the treatment of inflammatory bowel disease patients with infliximab, dashboards may reduce therapeutic failures and treatment costs. The history and future development of modern Bayesian dashboard systems is described.

Pharmacokinetic Features and Presence of Antidrug Antibodies Associate With Response to Infliximab Induction Therapy in Patients With Moderate to Severe Ulcerative Colitis

BACKGROUND & AIMS

The pharmacokinetics of infliximab during induction treatment for ulcerative colitis (UC) have not been studied. We investigated serum concentrations of infliximab and the early appearance of antibodies to infliximab (ATI) during induction treatment in patients with moderate-to-severe UC.

METHODS

We performed a prospective analysis of 19 consecutive patients with moderate-severe UC (endoscopic Mayo ≥ 2) receiving induction therapy with infliximab (5 mg/kg at weeks 0, 2, and 6) at 2 centers in Amsterdam, The Netherlands, from July 2012 through March 2014. Serial serum and fecal samples were collected for 6 weeks and concentrations of infliximab, ATI, c-reactive protein (CRP), albumin, and fecal calprotectin were measured. Treatment success was defined as endoscopic response (≥ 1 point reduction in the endoscopic Mayo score) at week 8.

RESULTS

Eleven patients (58%) had an endoscopic response. The median serum concentrations of infliximab at week 6 were 8.1 μg/mL in responders (interquartile range, 3.0-13.7 μg/mL) and 2.9 μg/mL in nonresponders (interquartile range, 0.01-5.8 μg/mL) (P = .03). ATIs were detected in 7 patients as early as day 18 (median, 28 d; interquartile range, 18-42 d). Six of the 8 nonresponders tested positive for ATIs vs 1 of 11 responders (P < .01; odds ratio, 30.0; 95% CI, 2.2-406.2). Patients with a baseline concentration of CRP greater than 50 mg/L had lower drug exposure from weeks 0 to 6 (587 mg/L/d in patients with high levels of CRP vs 1361 mg/L/day in patients with low CRP; P = .001). The median area under the curve for serum concentration of infliximab during induction therapy was 1230 mg/L/d in nonresponders vs 1352 mg/L/d in responders (P = .65).

CONCLUSIONS

There is a significant difference in serum concentration of infliximab at week 6 of treatment between responders and nonresponders. Early development of ATIs during induction therapy reduces the serum concentration of infliximab and is associated with nonresponse to treatment. Patients with high baseline serum levels of CRP had lower serum concentrations of infliximab.

CLINICAL TRIAL NUMBER

NL39626.018.12.

Role of the RANK/RANKL pathway in breast cancer

The discovery of the OPG/RANK/RANKL pathway two decades ago has initiated novel insights into regulation of bone formation. More recently this pathway has been found to be also relevant in osteoclastic-independent mechanisms, mainly in mammary physiology and breast cancer. RANKL/RANK function is essential for epithelial cell proliferation and cellular survival as well as lobulo-alveolar development. The endogenous OPG functions as a soluble decoy receptor, binding the cytokine RANKL to prevent RANKL from activating its receptor RANK. The regulatory function of RANKL is one of the key factors in progesterone-induced proliferation of the breast. Progesterone has a direct action of progesterone on progesterone-receptor (PR) expressing cells but PR-negative cells are affected indirectly through RANKL-induced paracrine actions leading to proliferation of mammary epithelial PR-negative cells. RANK induces epithelial-mesenchymal transition and stemness in human mammary epithelial cells and promotes tumorigenesis and metastasis. Inhibition of the RANK/RANKL pathway using the monoclonal antibody denosumab can neutralize RANKL and inhibiting its interaction with its receptor RANK. Denosumab is currently used to treat osteoporosis and in prevention of skeletal related events in patients suffering from bone metastases due to solid tumors. As preclinical experiments suggest the RANKL/RANK pathway plays an important role in primary breast cancer development. The interference with the RANK/RANKL system could therefore serve as a potential target for prevention and treatment of breast cancer.

A comprehensive review of denosumab for bone metastasis in patients with solid tumors

BACKGROUND

Denosumab is fully human monoclonal antibody that specifically binds and inactivates receptor activator of NF-kB ligand (RANKL), an important ligand that regulates bone remodeling. In this review, we aimed to show the clinical data about denosumab treatment and discuss its advantages for the management of patients with solid tumors and bone metastasis.

SCOPE

Denosumab showed positive results in clinical studies of solid tumors with bone metastasis. PubMed database and ASCO Symposium Meeting abstracts were searched until August 2015 by using the terms 'denosumab', 'RANKL inhibitor' and 'bone metastasis'. The last search was on 21 August 2015. All resulting studies were retrieved and were also checked for related publications. Clinical trials in this review fulfilled the following criterion: inclusion of sufficient data to allow estimation of the efficacy and safety of denosumab.

FINDINGS

The effects of denosumab on skeletal-related events (SREs) were investigated in three large randomized trials: one in patients with breast cancer, one in patients with prostate cancer, and one in patients with multiple myeloma or solid tumors other than breast or prostate cancer. In the breast cancer and prostate cancer studies denosumab was non-inferior and also superior to zoledronic acid in terms of the primary outcome time to first on-study SRE. In the third study denosumab was non-inferior to zoledronic acid but was not superior to zoledronic acid in solid tumors excluding breast and prostate cancer with bone metastases. In the three studies median overall survival and disease progression rates were similar between zoledronic acid and denosumab. Denosumab has also been studied in bone loss associated with hormonal therapy in both breast and prostate cancer. Adjuvant denosumab significantly reduced the risk of clinical fracture risk by 50% in breast cancer patients and by 62% in non-metastatic prostate cancer patients treated with adjuvant aromatase inhibitors or androgen deprivation therapy. In addition, biochemical markers of bone turnover and fractures were significantly reduced in patients under denosumab treatment.

CONCLUSION

The promising outcomes in the initial trials with denosumab have shown clinical activity and a favorable safety profile in patients with solid tumors and bone metastasis. Denosumab significantly reduced treatment-related osteoporosis associated with breast and prostate cancer and was superior to zoledronic acid in prevention or delaying of SRE.

Development of bevacizumab in advanced cervical cancer: pharmacodynamic modeling, survival impact and toxicology

Historically, patients with metastatic, persistent or recurrent cervical cancer had limited therapeutic options. Despite several Phase II/III clinical trials, the combination of cisplatin and paclitaxel remained the most effective chemotherapeutic regimen. In 2014, publication of Gynecologic Oncology Group 240 represented the emergence of an alternate and effective therapeutic option. This prospective, randomized, Phase III clinical trial explored the impact of adding the antiangiogenic agent bevacizumab to two separate cytotoxic chemotherapy backbones. Importantly, the study met its primary end point, showing a survival advantage of approximately 4 months without detriment in quality of life. As such, a review of bevacizumab and its application in patients with advanced-stage cervical cancer is warranted.

Progress with anti-tumor necrosis factor therapeutics for the treatment of inflammatory bowel disease

Anti-tumor necrosis factor (TNF) therapy is a valid, effective and increasingly used option in inflammatory bowel disease management. Nevertheless, further knowledge and therapeutic indications regarding these drugs are still evolving. Anti-TNF therapy may be essential to achieve recently proposed end points, namely mucosal healing, prevention of bowel damage and prevention of patient's disability. Anti-TNF drugs are also suggested to be more effective in early disease, particularly in early Crohn's disease. Moreover, its efficacy for prevention of postoperative recurrence in Crohn's disease is still debated. Costs and adverse effects, the relevance of drug monitoring and the possibility of anti-TNF therapy withdrawal in selected patients are still debated issues. This review aimed to describe and discuss the most relevant data about the progress with anti-TNF therapy for the management of inflammatory bowel disease.

Dashboard systems: Pharmacokinetic/pharmacodynamic mediated dose optimization for monoclonal antibodies

Many marketed drugs exhibit high variability in exposure and response. While these drugs are efficacious in their approved indications, finding appropriate dose regimens for individual patients is not straightforward. Similar dose adjustment problems are also seen with drugs that have a complex relationship between exposure and response and/or a narrow therapeutic window. This is particularly true for monoclonal antibodies, where prolonged dosing at a sub-therapeutic dose can also elicit anti-drug antibodies which will further compromise safety and efficacy. Thus, finding appropriate doses quickly would represent a substantial improvement in healthcare. Dashboard systems, which are decision-support tools, offer an improved, convenient means of tailoring treatment for individual patients. This article reviews the clinical need for this approach, particularly with monoclonal antibodies, the design, development, and testing of such systems, and the likely benefits of dashboard systems in clinical practice. We focus on infliximab for reference.

Model-based clinical pharmacology profiling of ipilimumab in patients with advanced melanoma

Aim

Ipilimumab is a fully human, monoclonal antibody that blocks cytotoxic T-lymphocyte antigen-4. The objective of the present study was to characterize the clinical pharmacology profile of ipilimumab using a population pharmacokinetic (PPK) approach.

Methods

The PPK model was developed using 2095 ipilimumab serum concentration values from 499 patients with unresectable stage III or IV melanoma from four phase II studies, with ipilimumab doses ranging from 0.3 to 10 mg kg⁻¹. The structural PK model was determined by developing a base PPK model. The effect of covariates on model parameters was assessed by a full covariate model, which incorporated all pre-specified covariate-parameter relationships into the base model. The final model was developed by backward elimination, followed by exclusion of covariates determined not to be of clinical relevance to ipilimumab, and was rigorously validated against both internal and external datasets.

Results

Ipilimumab PK was linear and time-invariant, with dose-proportional exposures over the available dose range, yielding a terminal half-life of approximately 15 days. Clearance of ipilimumab increased with increasing body weight and baseline serum lactate dehydrogenase concentrations, but was not affected by age, gender, concomitant budesonide, Eastern Cooperative Oncology Group performance status or prior systemic anticancer therapy. Furthermore, ipilimumab exposure was not affected by moderate renal impairment or mild hepatic impairment.

Conclusions

Ipilimumab concentration–time data were well described by a linear, two compartment, zero order i.v. infusion model. The model confirms that a body weight-normalized dosing regimen is appropriate for ipilimumab therapy in patients with advanced melanoma.

Therapeutic drug monitoring of targeted anticancer therapy

New oral targeted anticancer therapies are revolutionizing cancer treatment by transforming previously deadly malignancies into chronically manageable conditions. Nevertheless, drug resistance, persistence of cancer stem cells, and adverse drug effects still limit their ability to stabilize or cure malignant diseases in the long term. Response to targeted anticancer therapy is influenced by tumor genetics and by variability in drug concentrations. However, despite a significant inter-patient pharmacokinetic variability, targeted anticancer drugs are essentially licensed at fixed doses. Their therapeutic use could however be optimized by individualization of their dosage, based on blood concentration measurements via the therapeutic drug monitoring (TDM). TDM can increase the probability of therapeutic responses to targeted anticancer therapies, and would help minimize the risk of major adverse reactions.

Pharmacokinetics and pharmacokinetic-pharmacodynamic relationships of monoclonal antibodies in children

Monoclonal antibodies (mAbs) constitute a therapeutically and economically important drug class with increasing use in both adult and paediatric patients. The rather complex pharmacokinetic and pharmacodynamic properties of mAbs have been extensively reviewed in adults. In children, however, limited information is currently available. This paper aims to comprehensively review published pharmacokinetic and pharmacokinetic-pharmacodynamic studies of mAbs in children. The current status of mAbs in the USA and in Europe is outlined, including a critical discussion of the dosing strategies of approved mAbs. The pharmacokinetic properties of mAbs in children are exhaustively summarised along with comparisons to reports in adults: for each pharmacokinetic process, we discuss the general principles and mechanisms of the pharmacokinetic/pharmacodynamic characteristics of mAbs, as well as key growth and maturational processes in children that might impact these characteristics. Throughout this review, considerable knowledge gaps are identified, especially regarding children-specific properties that influence pharmacokinetics, pharmacodynamics and immunogenicity. Furthermore, the large heterogeneity in the presentation of pharmacokinetic/pharmacodynamic data limited clinical inferences in many aspects of paediatric mAb therapy. Overall, further studies are needed to fully understand the impact of body size and maturational changes on drug exposure and response. To maximise future knowledge gain, we propose a 'Guideline for Best Practice' on how to report pharmacokinetic and pharmacokinetic-pharmacodynamic results from mAb studies in children which also facilitates comparisons. Finally, we advocate the use of more sophisticated modelling strategies (population analysis, physiology-based approaches) to appropriately characterise pharmacokinetic-pharmacodynamic relationships of mAbs and, thus, allow for a more rational use of mAb in the paediatric population.

Loss of Infliximab Into Feces Is Associated With Lack of Response to Therapy in Patients With Severe Ulcerative Colitis

BACKGROUND & AIMS

It is not clear why some patients with ulcerative colitis (UC) do not respond to treatment with anti-tumor necrosis factor (TNF) agents, such as infliximab. It could be that some patients have high level of inflammation, with large quantities of TNF to be neutralized by the drug. We investigated whether loss of anti-TNF agents through ulcerated intestinal mucosa reduces the efficacy of these drugs in patients with severe UC.

METHODS

We collected fecal samples from 30 consecutive patients with moderate to severely active UC during the first 2 weeks of infliximab therapy at the University of Amsterdam hospital. Infliximab concentrations were measured in serum and supernatants of fecal samples using an enzyme-linked immunosorbent assay (Sanquin Biologicals Laboratory, Amsterdam, The Netherlands). Clinical and endoscopic responses were assessed 2 and 8 weeks and 3 months after treatment began.

RESULTS

Infliximab was detected in 129 of 195 fecal samples (66%); the highest concentrations were measured in the first days after the first infusion. Patients that were clinical nonresponders at week 2 had significantly higher fecal concentrations of infliximab after the first day of treatment than patients with clinical responses (median concentration, 5.01 μg/mL in nonresponders vs 0.54 μg/mL in responders; P = .0047). We did not observe a correlation between fecal and serum concentrations of infliximab.

CONCLUSIONS

Infliximab is lost into stools of patients with UC. High fecal concentrations of infliximab in the first days after therapy begins are associated with primary nonresponse. Additional studies are needed to determine how therapeutic antibodies are lost through the intestinal mucosa and how this process affects treatment response. Clinical trial ID: NL41310.018.12.

Therapeutic Drug Monitoring of Anti-tumor Necrosis Factor Agents in Patients with Inflammatory Bowel Diseases

Anti-tumor necrosis factor (TNF) agents have radically changed the treatment of inflammatory bowel diseases. Although a significant amount of patients respond to therapy, others experience only a partial response or do not benefit at all. Although, in some cases, the mechanistic action of the anti-TNF therapy may explain such findings, we have now learned that many patients may instead suffer from inadequate dosing and drug exposure. Such heterogeneity in how patients respond to therapy may be explained by multiple pharmacodynamic variables, such as factors that alter drug clearance, including the level of systemic inflammation, the presence of antidrug antibodies, and concomitant use of immunomodulators. Multiple studies have found that low-serum anti-TNF levels are associated with active disease and that adjusting the dose in these cases may offer a therapeutic benefit. In this review, we discuss the most recent evidence on therapeutic drug monitoring in patients with inflammatory bowel disease receiving anti-TNF biological therapies.

Therapeutic Potential of Denosumab in Patients With Lung Cancer: Beyond Prevention of Skeletal Complications

Approximately up to 40% of patients with lung cancer develop bone metastasis, with 22% to 59% of them experiencing skeletal-related events (SREs), which result in an important quality of life deterioration and economic burden. Denosumab, a fully human antibody that targets the receptor activator of nuclear factor-κB (RANK) ligand (RANKL), is indicated for prevention of SREs in patients with solid tumors and has demonstrated superiority in breast and prostate cancer, and in other solid tumors, in reducing the risk of first SRE by 17% versus zoledronic acid. In the subset of patients with non-small-cell lung carcinoma (NSCLC), denosumab has also shown a positive trend to SRE risk reduction. Denosumab might have direct or indirect antitumor effects. Cancer cells produce factors that stimulate increased bone resorption by osteoclasts, which in turn release tumor growth factors into the bone microenvironment, initiating a tumor/bone vicious cycle. An increasing body of evidence suggests RANK/RANKL signaling plays a role in this tumorigenesis. Both proteins are overexpressed in different tumor types including lung cancer cells. RANK/RANKL signaling activates nuclear factor-κB pathways related to lung carcinogenesis and increases intercellular adhesion molecule 1 expression and MEK/extracellular signal-regulated kinase phosphorylation, which in turn enhances tumor cell migration. In animal NSCLC models, denosumab delayed bone metastases and reduced skeletal tumor growth. In patients with lung cancer (post hoc analysis), denosumab prolonged overall survival by 1.2 months versus zoledronic acid (P = .01). This hypothesis-generating outcome warrants further investigation and 2 studies in lung cancer are ongoing to elucidate the therapeutic potential of denosumab beyond SRE prevention.

Review article: The pharmacokinetics and pharmacodynamics of drugs used in inflammatory bowel disease treatment

BACKGROUND

The following review is a compilation of the recent advances and knowledge on the behaviour of the most frequently used compounds to treat inflammatory bowel disease in an organism.

RESULTS

It considers clinical aspects of each entity and the pharmacokinetic/pharmacodynamic relationship supported by the use of plasma monitoring, tissue concentrations, and certain aspects derived from pharmacogenetics.

Tools for predicting the PK/PD of therapeutic proteins

INTRODUCTION

Assessments of the pharmacokinetic/pharmacodynamic (PK/PD) characteristics are an integral part in the development of novel therapeutic agents. Compared with traditional small molecule drugs, therapeutic proteins possess many distinct PK/PD features that necessitate the application of modified or separate approaches for assessing their PK/PD relationships.

AREAS COVERED

In this review, the authors discuss tools that are utilized to describe and predict the PK/PD features of therapeutic proteins and that are valuable additions in the armamentarium of drug development approaches to facilitate and accelerate their successful preclinical and clinical development.

EXPERT OPINION

A variety of state-of-the-art PK/PD tools is currently being applied and has been adjusted to support the development of proteins as therapeutics, including allometric scaling approaches, target-mediated disposition models, first-in-man dose calculations, physiologically based PK models and empirical and semi-mechanistic PK/PD modeling. With the advent of the next generation of biologics including bioengineered antibody constructs being developed, these tools will need to be further refined and adapted to ensure their applicability and successful facilitation of the drug development process for these novel scaffolds.

An accelerated infliximab induction regimen reduces the need for early colectomy in patients with acute severe ulcerative colitis

BACKGROUND & AIMS

Administration of infliximab to patients with acute severe ulcerative colitis (ASUC) (rescue therapy) can reduce the rate of early colectomy (within 12 months), but long-term rates of colectomy are the same as those of the pre-biologic era for these patients. The half-life of infliximab is shorter in patients with ASUC than in patients with non-severe UC, so more frequent dosing might be required to produce a therapeutic effect.

METHODS

We performed a retrospective analysis of 50 hospitalized patients who received infliximab for steroid-refractory ASUC at a single academic center from September 2005 through 2013. In 2011 an accelerated dosing strategy for infliximab was introduced; we compared outcomes of standard and accelerated dosing regimens. One group of patients (n = 35) were placed on a standard dosing regimen for infliximab and then given the drug at 0, 2, and 6 weeks and then every 8 weeks thereafter. A second group (n = 15) were placed on an accelerated regimen and received 3 induction doses of infliximab within a median period of 24 days. Rates of colectomy were compared between the groups during induction and follow-up periods.

RESULTS

There were no differences between groups in median baseline levels of C-reactive protein, albumin, or hemoglobin. The rate of colectomy during induction therapy was significantly lower with the accelerated regimen (6.7%, 1 of 15) than with the standard regimen (40%, 14 of 35) (Fisher exact test, P = .039). The standard regimen was associated with shorter time to colectomy (log-rank test, P = .042). Among patients who completed induction therapy, subsequent need for colectomy was similar between the groups during the follow-up period. Multivariate analysis showed that factors independently associated with successful induction therapy were level of albumin (g/L) when the treatment began (P = .003) and the accelerated dosing regimen (P = .03).

CONCLUSIONS

In patients with ASUC, an accelerated infliximab induction strategy reduces the need for early colectomy. An intensified infliximab dosing strategy in response to clinical or laboratory signs of breakthrough inflammation merits consideration in prospective studies.

Simulations of site-specific target-mediated pharmacokinetic models for guiding the development of bispecific antibodies

Bispecific antibodies (BAbs) are novel constructs that are under development and show promise as new therapeutic modalities for cancer and autoimmune disorders. The aim of this study is to develop a semi-mechanistic modeling approach to elucidate the disposition of BAbs in plasma and possible sites of action in humans. Here we present two case studies that showcase the use of modeling to guide BAb development. In case one, a BAb is directed against a soluble and a membrane-bound ligand for treating systemic lupus erythematosus, and in case two, a BAb targets two soluble ligands as a potential treatment for ulcerative colitis and asthma. Model simulations revealed important differences between plasma and tissues, when evaluated for drug disposition and target suppression. Target concentrations at tissue sites and type (soluble vs membrane-bound), tissue-site binding, and binding affinity are all major determinants of BAb disposition and subsequently target suppression. For the presented case studies, higher doses and/or frequent dosing regimens are required to achieve 80 % target suppression in site specific tissue (the more relevant matrix) as compared to plasma. Site-specific target-mediated models may serve to guide the selection of first-in-human doses for new BAbs.

Prediction of the Pharmacokinetics, Pharmacodynamics, and Efficacy of a Monoclonal Antibody, Using a Physiologically Based Pharmacokinetic FcRn Model

Although advantages of physiologically based pharmacokinetic models (PBPK) are now well established, PBPK models that are linked to pharmacodynamic (PD) models to predict pharmacokinetics (PK), PD, and efficacy of monoclonal antibodies (mAbs) in humans are uncommon. The aim of this study was to develop a PD model that could be linked to a physiologically based mechanistic FcRn model to predict PK, PD, and efficacy of efalizumab. The mechanistic FcRn model for mAbs with target-mediated drug disposition within the Simcyp population-based simulator was used to simulate the pharmacokinetic profiles for three different single doses and two multiple doses of efalizumab administered to virtual Caucasian healthy volunteers. The elimination of efalizumab was modeled with both a target-mediated component (specific) and catabolism in the endosome (non-specific). This model accounted for the binding between neonatal Fc receptor (FcRn) and efalizumab (protective against elimination) and for changes in CD11a target concentration. An integrated response model was then developed to predict the changes in mean Psoriasis Area and Severity Index (PASI) scores that were measured in a clinical study as an efficacy marker for efalizumab treatment. PASI scores were approximated as continuous and following a first-order asymptotic progression model. The reported steady state asymptote (Y ss) and baseline score [Y (0)] was applied and parameter estimation was used to determine the half-life of progression (T p) of psoriasis. Results suggested that simulations using this model were able to recover the changes in PASI scores (indicating efficacy) observed during clinical studies. Simulations of both single dose and multiple doses of efalizumab concentration-time profiles as well as suppression of CD11a concentrations recovered clinical data reasonably well. It can be concluded that the developed PBPK FcRn model linked to a PD model adequately predicted PK, PD, and efficacy of efalizumab.

Role for therapeutic drug monitoring during induction therapy with TNF antagonists in IBD: evolution in the definition and management of primary nonresponse

: Primary nonresponse and primary nonremission are important limitations of tumor necrosis factor (TNF) antagonists, occurring in 10% to 40% and 50% to 80% of patients with inflammatory bowel disease, respectively. The magnitude of primary nonresponse differs between phase III clinical trials and cohort studies, indicating differences, e.g., in definition, patient population or blinding. The causes of nonresponse can be attributed to the drug (pharmacokinetics, immunogenicity), the patient (genetics, disease activity), the disease (type, location, severity), and/or the treatment strategy (dosing regimen, combination therapy). Primary nonresponse has been attributed to "non-TNF-driven disease" which is an overly simplified and potentially misleading approach to the problem. Many patients with primary nonresponse could successfully be treated with dose optimization during the induction phase or switching to another TNF antagonist. Therefore, primary nonresponse is frequently not a non-TNF-driven disease. Recent studies from rheumatoid arthritis and preliminary data from inflammatory bowel disease evaluating therapeutic drug monitoring have suggested that early measurement of drug and anti-drug antibody concentrations could help to define primary nonresponse and rationalize patient management of this problem. Moreover, a modeling approach including pharmacological parameters and patient-related covariants could potentially be predictive for response to the treatment. We describe an overview of this evolution in thinking, underpinned by previous findings, and assess the potential role of early measurement of drug and antidrug antibody concentrations in the definition and management of primary nonresponse.

Preclinical and early clinical development of GNbAC1, a humanized IgG4 monoclonal antibody targeting endogenous retroviral MSRV-Env protein

Monoclonal antibodies (mAbs) play an increasing important role in the therapeutic armamentarium against multiple sclerosis (MS), an inflammatory and degenerative disorder of the central nervous system. Most of the mAbs currently developed for MS are immunomodulators blocking the inflammatory immune process. In contrast with mAbs targeting immune function, GNbAC1, a humanized IgG4 mAb, targets the multiple sclerosis associated retrovirus envelope (MSRV-Env) protein, an upstream factor in the pathophysiology of MS. MSRV-Env protein is of endogenous retroviral origin, expressed in MS brain lesions, and it is pro-inflammatory and toxic to the remyelination process, by preventing the differentiation of oligodendrocyte precursor cells. We present the preclinical and early clinical development results of GNbAC1. The specificity of GNbAC1 for its endogenous retroviral target is described. Efficacy of different mAb versions of GNbAC1 were assessed in MSRV-Env induced experimental allergic encephalitis (EAE), an animal model of MS. Because the target MSRV-Env is not expressed in animals, no relevant animal model exists for a proper in vivo toxicological program. An off-target 2-week toxicity study in mice was thus performed, and it showed an absence of safety risk. Additional in vitro analyses showed an absence of complement or antibody-dependent cytotoxicity as well as a low level of cross-reactivity to human tissues. The first-in-man clinical study in 33 healthy subjects and a long-term clinical study in 10 MS patients showed that GNbAC1 is well tolerated in humans without induction of immunogenicity and that it induces a pharmacodynamic response on MSRV biomarkers. These initial results suggest that the mAb GNbAC1 could be a safe long-term treatment for patients with MS with a unique therapeutic mechanism of action.

Quantitative prediction of human pharmacokinetics for mAbs exhibiting target-mediated disposition

Prediction of human pharmacokinetics (PK) can be challenging for monoclonal antibodies (mAbs) exhibiting target-mediated drug disposition (TMDD). In this study, we performed a quantitative analysis of a diverse set of six mAbs exhibiting TMDD to explore translational rules that can be utilized to predict human PK. A TMDD model with rapid-binding approximation was utilized to fit PK and PD (i.e., free and/or total target levels) data, and average absolute fold error (AAFE) was calculated for each model parameter. Based on the comparative analysis, translational rules were developed and applied to a test antibody not included in the original analysis. AAFE of less than two-fold was observed between monkey and human for baseline target levels (R 0), body-weight (BW) normalized central elimination rate (K el/BW(-0.25)) and central volume (V c/BW(1.0)). AAFE of less than three-fold was estimated for the binding affinity constant (K D). The other four parameters, i.e., complex turnover rate (K int), target turnover rate (K deg), central to peripheral distribution rate constant (K pt) and peripheral to central rate constant (K tp) were poorly correlated between monkey and human. The projected human PK of test antibody based on the translation rules was in good agreement with the observed nonlinear PK. In conclusion, we recommend a TMDD model-based prediction approach that integrates in vitro human biomeasures and in vivo preclinical data using translation rules developed in this study.

A phase IIa randomised clinical study of GNbAC1, a humanised monoclonal antibody against the envelope protein of multiple sclerosis-associated endogenous retrovirus in multiple sclerosis patients

Background:

GNbAC1 is an immunoglobulin (IgG4) humanised monoclonal antibody against multiple sclerosis-associated retrovirus (MSRV)-Env, a protein of endogenous retroviral origin, expressed in multiple sclerosis (MS) lesions, which is pro-inflammatory and inhibits oligodendrocyte precursor cell differentiation.

Objective:

This is a randomised, double-blind placebo-controlled dose-escalation study followed by a six-month open-label phase to test GNbAC1 in MS patients. The primary objective was to assess GNbAC1 safety in MS patients, and the other objectives were pharmacokinetic and pharmacodynamic assessments.

Methods:

Ten MS patients were randomised into two cohorts to receive a single intravenous infusion of GNbAC1/placebo at doses of 2 or 6 mg/kg. Then all patients received five infusions of GNbAC1 at 2 or 6 mg/kg at four-week intervals in an open-label setting. Safety, brain magnetic resonance imaging (MRI), pharmacokinetics, immunogenicity, cytokines and MSRV RNA expression were studied.

Results:

All patients completed the study. GNbAC1 was well tolerated in all patients. GNbAC1 pharmacokinetics is dose-linear with mean elimination half-life of 27–37 d. Anti-GNbAC1 antibodies were not detected. Cytokine analysis did not indicate an adverse effect. MSRV-transcripts showed a decline after the start of treatment. Nine patients had stable brain lesions at MRI.

Conclusion:

The safety, pharmacokinetic profile, and pharmacodynamic responses to GNbAC1 are favourable in MS patients over a six-month treatment period.

Model-based assessment of dosing strategies in children for monoclonal antibodies exhibiting target-mediated drug disposition

Body weight/body surface area–based and/or tiered fixed dosing strategies are widely utilized for monoclonal antibodies with linear clearance to scale adult clinical doses to children. However, there is limited knowledge on whether or not body weight–based dosing strategies also yield comparable dose-concentration-response relationships in adults and children for monoclonal antibodies that exhibit target-mediated drug disposition. Our findings indicate that it is important to interpret pharmacokinetics information in a pharmacokinetics/pharmacodynamics context as similar systemic drug exposure in adults and children may not be reflective of the corresponding target occupancy. They further indicate that BW-based dosing is superior to fixed dosing for the same target concentration, whereas the opposite holds true for the same target amount in adults and children. Michaelis-Menten approximations yielded similar profiles compared to the full target-mediated drug disposition model for all simulation scenarios and may be used to guide the selection of appropriate dosing regimens in children.