Model-Informed Development of a Cost-Saving Dosing Regimen for Sacituzumab Govitecan.

BACKGROUND: The antibody-drug conjugate sacituzumab govitecan is approved for metastatic triple-negative breast cancer and has shown promising results in various other types of cancer. Its costs may limit patient access to this novel effective treatment modality. OBJECTIVE: The purpose of this study was to develop an evidence-based rational dosing regimen that results in targeted drug exposure within the therapeutic range while minimizing financial toxicity, to improve treatment access. PATIENTS AND METHODS: Exposure equivalent dosing strategies were developed based on pharmacokinetic modeling and simulation by using the published pharmacokinetic model developed by the license holder. The alternative dose was based on the principle of using complete vials to prevent spillage and on the established non-linear relationship between body weight and systemic exposure. Equivalent exposure compared to the approved dosing regimen of 10 mg/kg was aimed for. Equivalent exposure was conservatively defined as calculated geometric mean ratios within the 0.9-1.11 boundaries for area under the concentration-time curve (AUC), trough concentration (Ctrough) and maximum concentration (Cmax) of the alternative dosing regimen compared to the approved dosing regimen. Since different vial sizes are available for the European Union (EU) and United States (US) market, because body weight distributions differ between these populations, we performed our analysis for both scenarios. RESULTS: Dosing regimens of sacituzumab govitecan for the EU (< 50 kg: 400 mg, 50-80 kg: 600 mg, and > 80 kg: 800 mg) and US population (< 40 kg: 360 mg, 40-65 kg: 540 mg, 65-90 kg: 720 mg, and > 90 kg: 900 mg) were developed, based on weight bands. The geometric mean ratios for all pharmacokinetic outcomes were within the predefined equivalence boundaries, while the quantity of drug used was 21.5% and 19.0% lower for the EU and US scenarios, respectively. CONCLUSIONS: With the alternative dosing proposal, an approximately 20% reduction in drug expenses for sacituzumab govitecan can be realized while maintaining an equivalent and more evenly distributed exposure throughout the body weight range, without notable increases in pharmacokinetic variability.

Quantitative systems pharmacology modeling of HER2-positive metastatic breast cancer for translational efficacy evaluation and combination assessment across therapeutic modalities.

HER2-positive (HER2+) metastatic breast cancer (mBC) is highly aggressive and a major threat to human health. Despite the significant improvement in patients' prognosis given the drug development efforts during the past several decades, many clinical questions still remain to be addressed such as efficacy when combining different therapeutic modalities, best treatment sequences, interindividual variability as well as resistance and potential coping strategies. To better answer these questions, we developed a mechanistic quantitative systems pharmacology model of the pathophysiology of HER2+ mBC that was extensively calibrated and validated against multiscale data to quantitatively predict and characterize the signal transduction and preclinical tumor growth kinetics under different therapeutic interventions. Focusing on the second-line treatment for HER2+ mBC, e.g., antibody-drug conjugates (ADC), small molecule inhibitors/TKI and chemotherapy, the model accurately predicted the efficacy of various drug combinations and dosing regimens at the in vitro and in vivo levels. Sensitivity analyses and subsequent heterogeneous phenotype simulations revealed important insights into the design of new drug combinations to effectively overcome various resistance scenarios in HER2+ mBC treatments. In addition, the model predicted a better efficacy of the new TKI plus ADC combination which can potentially reduce drug dosage and toxicity, while it also shed light on the optimal treatment ordering of ADC versus TKI plus capecitabine regimens, and these findings were validated by new in vivo experiments. Our model is the first that mechanistically integrates multiple key drug modalities in HER2+ mBC research and it can serve as a high-throughput computational platform to guide future model-informed drug development and clinical translation.

A Systematic Evaluation of Cost-Saving Dosing Regimens for Therapeutic Antibodies and Antibody-Drug Conjugates for the Treatment of Lung Cancer.

BACKGROUND: Expensive novel anticancer drugs put a serious strain on healthcare budgets, and the associated drug expenses limit access to life-saving treatments worldwide. OBJECTIVE: We aimed to develop alternative dosing regimens to reduce drug expenses. METHODS: We developed alternative dosing regimens for the following monoclonal antibodies used for the treatment of lung cancer: amivantamab, atezolizumab, bevacizumab, durvalumab, ipilimumab, nivolumab, pembrolizumab, and ramucirumab; and for the antibody-drug conjugate trastuzumab deruxtecan. The alternative dosing regimens were developed by means of modeling and simulation based on the population pharmacokinetic models developed by the license holders. They were based on weight bands and the administration of complete vials to limit drug wastage. The resulting dosing regimens were developed to comply with criteria used by regulatory authorities for in silico dose development. RESULTS: We found that alternative dosing regimens could result in cost savings that range from 11 to 28%, and lead to equivalent pharmacokinetic exposure with no relevant increases in variability in exposure. CONCLUSIONS: Dosing regimens based on weight bands and the use of complete vials to reduce drug wastage result in less expenses while maintaining equivalent exposure. The level of evidence of our proposal is the same as accepted by regulatory authorities for the approval of alternative dosing regimens of other monoclonal antibodies in oncology. The proposed alternative dosing regimens can, therefore, be directly implemented in clinical practice.

Quantitative Assessment of the Efficacy of Near-Infrared Photoimmunotherapy with Bioluminescence Imaging.

Near-infrared photoimmunotherapy (NIR-PIT) is a cell-specific cancer therapy in which antibody-photoabsorber conjugates (APCs) are activated by NIR light to induce rapid immunogenic cell death with minimal off-target effects. In preclinical settings, bioluminescence imaging (BLI) is useful to quantitatively assess the efficacy of NIR-PIT for both in vitro and in vivo experiments, especially in the early phase of testing. Here, we describe the detailed methods of the experiments for NIR-PIT and evaluation of its efficacy using BLI.

Assessment of Cell Cytotoxicity and Comet Assay on HER2/neu Positive Cell Line Due to 111In Auger Electrons as DNA-Targeting Radioimmunoconjugate.

BACKGROUND: Breast cancer Auger electron therapy is a growing field of study in radioimmunotherapy and oncology research. Trastuzumab, a high affinity-binding monoclonal antibody against HER2/neu is which is over-expressed in breast tumors, is used in radiopharmaceutical development. OBJECTIVES: In this work, the lethal effects of 111In3+, 111In-DTPA-trastuzumab and 111In-trastuzumab coupled-nuclear localizing sequence peptide (111In-DTPA-NLS-trastuzumab) on malignant cells were studied in vitro. METHODS: DTPA-NLS-trastuzumab was prepared using sulfosuccinimidyl-4-(N-maleimidomethyl) cyclohexane-1-carboxylate (sulfo-SMCC) conjugation with NLS peptide in the first step, followed by conjugation with diethylenetriaminepentaacetic acid (DTPA). Both DTPA-trastuzumab and DTPA- NLS-trastuzumab were labeled with 111In followed by purification and quality control techniques. Sk-Br-3 (a HER2/neu+ cell line), was used in the cell viability assessment assay for 111In, 111In-DTPA-trastuzumab and 111In-DTPA-NLS-trastuzumab (3.7 MBq) at 37 ºC. The cytotoxicity of the three species was studied using MTT and comet assay was utilized DNA damage detection. RESULTS: A significant radiochemical purity for 111In-DTPA-NLS-trastuzumab (99.36% ± 0.30%, ITLC) at the DTPA:antibody ratio of 6.90 ± 0.34:1, was obtained. Significant cell viability difference was found for 111In-DTPA-NLS-trastuzumab compared to the other treatments at two-time points. In addition, comet assay demonstrated significant DNA damage at 144 h using 111In-DTPA- NLS-trastuzumab. CONCLUSION: The results of cell viability and cell death using MTT assay and comet assay, respectively, demonstrate the NLS-peptide effectively facilitates 111In-trastuzumab transport into the HER2/neu positive cancer cell nuclei to impose the radiotherapeutic effects of Auger electrons on DNA leading to cell death.

Anti-HER2 monoclonal antibody based-radioimmunoconjugates: Assessment of the chelating agent influence.

In the present work, the radioimmunoconjugates 111In-DTPA-trastuzumab and 177Lu-DOTA-trastuzumab were evaluated regarding the influence of the chelating agents on the physical-chemical parameters and human epidermal growth factor receptor 2 (HER2) tumor cell binding. Data showed that both chelating agents, at predetermined molar ratios (antibody:chelator - 1:10 and 1:20), did not influence the immunoconjugates integrity, the radiolabeling process and the radiolabeled antibodies stability. However, differences were observed in the lipophilic feature between DOTA and DTPA radioimmunoconjugates and in the specific binding to SK-BR-3 tumor cells (HER2 positive). Therefore, this study showed the importance of assessing the influence of chelating agents and their molar ratios in the development process of radioimmunoconjugates.

Development and biological assessment of MMAE-trastuzumab antibody-drug conjugates (ADCs).

BACKGROUND: Trastuzumab, a humanized monoclonal antibody targeting Human Epidermal growth factor Receptor 2 (HER2), is a therapeutic option used for the treatment of patients with HER2-overexpressing breast cancers. The primary purpose of the present study was to establish a trastuzumab-based antibody drug conjugate (ADC) to enhance the biopharmaceutical profile of trastuzumab. METHODS: In this study, trastuzumab was linked to the microtubule-disrupting agent monomethyl auristatin E (MMAE) through a peptide linker. Following conjugation, MMAE-trastuzumab ADCs were characterized using SDS-PAGE, UV/VIS, and cell-based ELISA. The inhibitory effects of the ADCs were measured on MDA-MB-453 (HER2-positive cells) and HEK-293 (HER2-negative cells) using in vitro cell cytotoxicity and colony formation assays. RESULTS: Our findings showed that approximately 3.4 MMAE payloads were conjugated to trastuzumab. MMAE-trastuzumab ADCs produced six bands, including H2L2, H2L, HL, H2, H, and L in non-reducing SDS-PAGE. The conjugates exhibited the same binding ability to MDA-MB-453 as unconjugated trastuzumab. The MTT assay showed a significant improvement in the trastuzumab activity following MMAE conjugation, representing a higher antitumor activity as compared with unconjugated trastuzumab. Furthermore, ADCs were capable of potentially inhibiting colony formation in HER2-positive cells, as compared with trastuzumab. CONCLUSION: MMAE-trastuzumab ADCs represent a promising therapeutic strategy to treat HER2-positive breast cancer.

Sustained activity of novel THIOMAB antibody-antibiotic conjugate against Staphylococcus aureus in a mouse model: Longitudinal pharmacodynamic assessment by bioluminescence imaging.

Staphylococcus aureus (S. aureus) infections are a leading cause of death by an infectious agent. Survival within host phagocytic cells is one mechanism by which S. aureus evades antibiotic treatment. A novel THIOMAB™ antibody-antibiotic conjugate (TAC) strategy was developed to kill S. aureus intracellularly and mitigate the spread of infection. In this report, we used a longitudinal whole-body bioluminescence imaging method to study the antibacterial dynamics of TAC alone or in combination with vancomycin in a mouse infection model. Injections of stably luminescent S. aureus bacteria into mice resulted in exponential increases in whole body bioluminescence with a reduction in body weight and survival rate. Vancomycin, a standard-of-care antibiotic, suppressed bacterial growth in mice. However, bacterial growth rebounded in these animals once treatment was discontinued. In contrast, single dose of TAC showed rapid reduction of bioluminescence intensity, which persisted for up to 19 days. The combination of TAC and vancomycin achieved a more sustained and significantly greater reduction of bioluminescence compared with vancomycin alone. In summary, the present study showed an imaging method to longitudinally assess antibacterial drug dynamics in mice and demonstrated that TAC monotherapy or in combination with vancomycin had superior and sustained activity compared to vancomycin alone.

In Vivo Immunofluorescence Localization for Assessment of Therapeutic and Diagnostic Antibody Biodistribution in Cancer Research.

Monoclonal antibodies (mAbs) are important tools in cancer detection, diagnosis, and treatment. They are used to unravel the role of proteins in tumorigenesis, can be directed to cancer biomarkers enabling tumor detection and characterization, and can be used for cancer therapy as mAbs or antibody-drug conjugates to activate immune effector cells, to inhibit signaling pathways, or directly kill cells carrying the specific antigen. Despite clinical advancements in the development and production of novel and highly specific mAbs, diagnostic and therapeutic applications can be impaired by the complexity and heterogeneity of the tumor microenvironment. Thus, for the development of efficient antibody-based therapies and diagnostics, it is crucial to assess the biodistribution and interaction of the antibody-based conjugate with the living tumor microenvironment. Here, we describe In Vivo Immunofluorescence Localization (IVIL) as a new approach to study interactions of antibody-based therapeutics and diagnostics in the in vivo physiological and pathological conditions. In this technique, a therapeutic or diagnostic antigen-specific antibody is intravenously injected in vivo and localized ex vivo with a secondary antibody in isolated tumors. IVIL, therefore, reflects the in vivo biodistribution of antibody-based drugs and targeting agents. Two IVIL applications are described assessing the biodistribution and accessibility of antibody-based contrast agents for molecular imaging of breast cancer. This protocol will allow future users to adapt the IVIL method for their own antibody-based research applications.

Preclinical Efficacy and Safety Assessment of an Antibody-Drug Conjugate Targeting the c-RET Proto-Oncogene for Breast Carcinoma.

PURPOSE: The RET proto-oncogene has been implicated in breast cancer, and the studies herein describe the preclinical and safety assessment of an anti-RET antibody-drug conjugate (ADC) being developed for the treatment of breast cancer. EXPERIMENTAL DESIGN: RET protein expression was analyzed in breast tumor samples using tissue microarrays. The fully human anti-RET antibody (Y078) was conjugated to the DM1 and DM4 derivatives of the potent cytotoxic agent maytansine using thioether and disulfide linkers, respectively. The resulting compounds, designated Y078-DM1 and Y078-DM4, were evaluated for antitumor activity using human breast cancer cell lines and established tumor xenograft models. A single-dose, 28-day, safety study of Y078-DM1 was performed in cynomolgus monkeys. RESULTS: By immunohistochemistry, RET expression was detected in 57% of tumors (1,596 of 2,800 tumor sections) and was most common in HER2-positive and basal breast cancer subtypes. Potent in vitro cytotoxicity was achieved in human breast cancer cell lines that have expression levels comparable with those observed in breast cancer tissue samples. Dose-response studies in xenograft models demonstrated antitumor activity with both weekly and every-3-weeks dosing regimens. In cynomolgus monkeys, a single injection of Y078-DM1 demonstrated dose-dependent, reversible drug-mediated alterations in blood chemistry with evidence of on-target neuropathy. CONCLUSIONS: RET is broadly expressed in breast cancer specimens and thus represents a potential therapeutic target; Y078-DM1 and Y078-DM4 demonstrated antitumor activity in preclinical models. Optimization of the dosing schedule or an alternate cytotoxic agent with a different mechanism of action may reduce the potential risk of neuropathy. Clin Cancer Res; 21(24); 5552-62. ©2015 AACR.

Assessment of belatacept-mediated costimulation blockade through evaluation of CD80/86-receptor saturation.

BACKGROUND: The selective inhibitor of T-cell costimulation, belatacept, blocks CD28-mediated T-cell activation by binding CD80 and CD86 on antigen-presenting cells. Understanding the extent to which belatacept binds to its targets in patients may enable correlation of belatacept exposure to receptor saturation as a pharmacodynamic measure of costimulation blockade. METHODS: Flow cytometry-based receptor competition assays were developed to monitor concentration-dependent occupancy of CD80 and CD86 receptors in whole blood and dendritic cell cultures in vitro. Receptor occupancy was correlated with inhibition of mixed leukocyte reactions and clinical validation was obtained by comparing receptor saturation in whole blood from healthy volunteers and in de novo renal transplant recipients participating in studies comparing cyclosporine and belatacept-based immunosuppression. RESULTS: Belatacept saturated CD80 and CD86 receptors in whole blood and dendritic cell cultures, although the belatacept concentrations required for CD86-receptor saturation were approximately 10-fold higher than those required for CD80 saturation (IC50=0.102 microg/mL vs. 0.009 microg/mL). Primary alloresponses were inhibited at the belatacept concentration required for CD86-receptor saturation, but not at the lower concentration needed to saturate CD80. Whole blood from belatacept-treated patients had significantly lower levels of free CD86 receptors versus pretransplant levels, healthy volunteers, or cyclosporine-treated patients. CD86-receptor saturation correlated with belatacept dose/dose frequency and remained consistently more than 80%. CONCLUSIONS: These results suggest that belatacept-mediated inhibition of alloresponses involved in transplant rejection correlates with CD86 saturation, indicating that CD86-receptor occupancy may be a valid pharmacodynamic measure of costimulation blockade and provide the first direct clinical evidence that belatacept binds to one of its targets.

Cost-effectiveness modeling of abatacept versus other biologic agents in DMARDS and anti-TNF inadequate responders for the management of moderate to severe rheumatoid arthritis.

To assess the cost-effectiveness of abatacept compared to different biologic treatment strategies for moderate to severe rheumatoid arthritis based on current medical practices in Canada. A model was constructed to assess the cost-effectiveness of various biologic treatments over a 2-year time horizon, using two effectiveness endpoints: "low disease activity state" (LDAS) and "remission". Abatacept, as first biologic agent after an inadequate response to DMARDs, provides greater treatment success rate for achieving LDAS (29.4% versus 15.6%) and remission (14.8% versus 5.2%), and appears significantly more cost-effective compared to the sequential use of anti-TNF agents (p<0.001). Abatacept, as second biologic agent after an inadequate response to one anti-TNF agent, provides greater treatment success rate for achieving LDAS (17.1% versus 10.2%) and remission (7.4% versus 3.9%) and appears significantly more cost-effective compared to the sequential use of anti-TNF agents (p<0.001). Abatacept is a cost-effective strategy in patients with an inadequate response to DMARDs or to one anti-TNF agent.

Improving patient outlook in rheumatoid arthritis: experience with abatacept.

PURPOSE: To examine the importance of improving patient outlook in rheumatoid arthritis (RA) and to discuss the role of the nurse practitioner (NP) who, through the assessment of patient-reported outcomes and in acting as an advocate for the patient with the wider healthcare team, has a crucial part to play in managing the overall well-being of the patient. This article will draw on the clinical experience to date with abatacept, a first-in-class therapy that has been approved for the treatment of RA in patients with an inadequate response to either traditional disease-modifying antirheumatic drugs (DMARDs), such as methotrexate, or biological DMARDs, such as tumor necrosis factor-alpha antagonists. DATA SOURCES: A comprehensive literature search was performed using the National Library of Medicine (MEDLINE), EMBASE, and BIOSIS databases (restricted to articles posted between January 2000 and February 2007) with the search terms CTLA-4Ig, abatacept, and primary clinical trial publications in patients with RA. The clinical data are summarized in this review along with safety data presented in the prescribing information. CONCLUSIONS: Recent changes in the approach to RA treatment, particularly the advent of biological therapies, have impacted the role of the NP. The role of the NP is integral to the management of RA and in maximizing patient outcomes, through educating patients to make informed choices regarding their treatment, ensuring the safe administration of therapies and monitoring response to therapy, and in acting as an advocate for the patient within the wider healthcare team. IMPLICATIONS FOR PRACTICE: The use of more patient-centered measures of response are gaining increasing importance both in clinical trials and in clinical practice, and as such the NP has an important role in ensuring that both the physical and the psychological needs of patients are met. Clinical trials to date have shown that abatacept provides significant and clinically meaningful improvements in patient-reported outcomes, as well as demonstrating significant clinical benefits and a consistent safety profile, thus representing a valuable treatment option within the RA treatment armamentarium.

Abatacept.

PURPOSE: The pharmacology, pharmacokinetics, indications, clinical efficacy, adverse effects, drug interactions, dosing, and administration of abatacept are discussed. SUMMARY: Abatacept is the first drug in a new class of agents known as selective costimulator modulators. Abatacept has been shown to decrease tumor necrosis factor (TNF)-alpha, which is important to the inflammatory response. Abatacept inhibits T-cell function but does not deplete T cells. Activated T cells are important in the inflammatory cascade, ultimately leading to joint inflammation and irreversible structural damage. In patients with rheumatoid arthritis, there is chronic inflammation of the synovial tissue lining the joint capsule. Abatacept is indicated for reducing the signs and symptoms of moderate to severe rheumatoid arthritis in adult patients who have had an inadequate response to at least one disease-modifying antirheumatic drug. Studies in adult patients with rheumatoid arthritis have evaluated abatacept in patients with an inadequate response to either methotrexate or TNF-alpha blocking agents. One trial showed that abatacept produced a favorable six-month clinical response in patients who had previously failed to respond to anti-TNF-alpha therapy. In a study of concurrent abatacept and methotrexate therapy, the addition of abatacept produced favorable outcomes in patients who were not adequately responding to methotrexate alone. CONCLUSION: Abatacept, a newly approved agent for the treatment of rheumatoid arthritis, has shown promising results in patients who have had an inadequate response to other treatment modalities. Abatacept therapy should be reserved for patients who have failed other time-tested treatment modalities, including TNF-alpha antagonists. Results from ongoing postmarketing studies will help determine abatacept's place in therapy.

Immunoconjugates: current status and future potential.

Whilst the concepts involved in immunoconjugates go back two centuries to the ideas of Ehrlich; it was only in the early 1980s that biotechnology gave us the tools to make pure immunoconjugates, in quantities sufficient for clinical studies [Garnett, M.C. (2002) "Targeted drug conjugates: principles and progress". Advanced Drug Delivery Reviews, 53, 171-216]. The early problems with immunogenicity that antibodies encountered in the clinic were addressed, in part by chimeric antibodies and later with humanised antibodies. At this time a number of different approaches were seriously evaluated for immunoconjugates, all with significant industrial backing, particularly from the emerging biotechnology companies.

Assessment of the radiochemical design of antibodies with a metabolizable linkage for target-selective radioactivity delivery.

Interposition of a metabolizable linkage has been performed to reduce the hepatic radioactivity levels of radiolabeled antibodies. To estimate the validity of this strategy, a radioiodination reagent (HML) that provides a stable attachment for m-iodohippuric acid with proteins in plasma while facilitating rapid and selective release of the compound after lysosomal proteolysis in the liver was conjugated with a monoclonal antibody (mAb) against osteogenic sarcoma (OST7, IgG1). Radiolabeled OST7 conjugates with a plasma-labile ester bond for releasing m-iodohippuric acid (MIH), plasma-stable amide bonds for releasing radiometabolites of hepatobiliary excretion (MPH), or slow elimination rates from hepatocytes ([111In]EMCS-Bz-EDTA) were prepared with similar conjugation chemistry. The four radiolabeled OST7 conjugates were characterized both in vitro and in vivo. All the radiolabeled OST7 conjugates had similar radiochromatograms on size-exclusion HPLC and similar antigen binding affinities. While MIH-OST7 indicated accelerated clearance of radioactivity from the blood due to the release of m-iodohippurate, the rest of the three radiolabeled OST7 conjugates remained stable in serum incubation studies and had similar radioactivity elimination from the blood in vivo. When injected into normal mice, HML-OST7 demonstrated tissue-to-blood ratios of radioactivity similar to those of MIH-OST7 and significantly lower than those of the other two radiolabeled OST7 conjugates. In biodistribution studies in nude mice, both HML-OST7 and MIH-OST7 exhibited tumor-to-liver or tumor-to-intestine ratios of radioactivity higher than those of [111In]EMCS-Bz-EDTA-OST7 or MPH-OST7, respectively. HML-OST7, MPH-OST7, and [111In]EMCS-Bz-EDTA-OST7 indicated there were no changes in the radioactivity levels in the tumor between 24 and 48 h postinjection, whereas MIH-OST7 significantly decreased the radioactivity levels in the tumor at these time points. HML reduced the radioactivity levels in nontarget tissues without impairing the tumor radioactivity levels delivered by OST7. These findings indicated that the design of a radiolabeled mAb that is stable in plasma and liberates the radiometabolite of rapid urinary excretion constitutes an effective strategy for achieving target-selective radioactivity delivery.