Pharmacokinetics and Pharmacodynamics of Antibody-Drug Conjugates Administered via Subcutaneous and Intratumoral Routes

Fundamental properties and principal areas of focus in antibody-drug conjugates formulation development

Antibody-drug conjugates (ADCs) have emerged as a rapidly expanding class of therapeutics driven by their superior specificity and clinical efficacy. 14 out of 16 commercially approved ADCs are formulated as lyophilized forms because ADC is generally considered to be less stable than unmodified antibody. The formulation development for ADCs, particularly liquid formulation, presents unique challenges due to their intricate structural complexity, physicochemical properties, and degradation pathways. This review provides the first comprehensive analysis of formulation strategies employed in commercial ADCs. Furthermore, this review discusses the key areas of focus for ADCs throughout the formulation development workflow, spanning from the initial formulation development to the final stage of drug product manufacturing. In addition, we identify and analyze the distinctive technical challenges in ADC formulation development compared to unconjugated antibody, while proposing potential solutions to these challenges. Finally, we offer strategic perspectives on future directions in ADC formulation development to advance this promising therapeutic modality.

Meta-Analysis of Exposure-Adverse Event Relationships for Antibody-Drug Conjugates

Antibody-drug conjugates (ADCs) have become a vital class of therapeutics in oncology because of their ability to selectively deliver potent drug molecules to tumor cells. However, ADC-associated toxicities cause high failure rates in the clinic and hinder their full potential. Due to the complex structure and pharmacokinetics of ADCs, it is challenging to identify the drivers of their toxicities. Here, quantitative analysis was performed to correlate the incidence of clinical adverse events (AEs) with nine different commonly measured exposure parameters collected from study-level summary data. We considered ADC analytes for different classes of ADCs, to identify ADC analytes that are strongly associated with the AEs for ADCs. Published clinical exposure and safety data for any grade and grade ≥3 AEs from 40 publications across six ADCs and three payloads were collected and analyzed. Exposure-AE relationships were quantified using logit models, and the strength of the correlations and rank order were determined. The analysis suggests that deruxtecan ADC-related toxicities correlated most strongly with the exposure of the free payload; monomethyl auristatin E (MMAE) ADC-related toxicities correlated with the free MMAE area under the curve; and pyrrolobenzodiazepine ADC-related toxicities correlated with no specific analyte but the dose. These findings agree with the published literature and support the notion that AE profiles are often shared by ADCs that deliver the same cytotoxic payload. The exposure-AE relationships presented here, together with identification of the most informative ADC analytes, may facilitate more focused mechanistic studies on the drivers of clinical AEs and could support dosing decisions during clinical development of ADCs.

Applying Ultrasound to Mechanically and Noninvasively Sensitize Prostate Tumors to TRAIL-Mediated Apoptosis

Non-surgical and safe prostate cancer (PCa) therapies are in demand. Soluble tumor necrosis factor (TNF-α) related apoptosis inducing ligand (TRAIL), a cancer-specific drug, shows preclinical efficacy but has a short circulation half-life. This research has shown that physiological fluid shear stress activates mechanosensitive ion channels (MSCs), such as Piezo1, enhancing TRAIL-mediated apoptosis in cancer cells. Herein, noninvasive, focal ultrasound (FUS) is implemented to augment the pro-apoptotic effects of TRAIL. Using thermally safe FUS parameters, it is observed that TRAIL sensitivity increases with higher FUS pressure in PCa cells, mediated by Piezo1. This is confirmed by examining the effects of calcium chelation, MSC inhibitors, and PIEZO knockdown. In vivo, a multi-dose study with 10 min FUS exposure shows that 0 and 4-h intervals between TRAIL and FUS significantly reduce tumor burden, with an increase in apoptosis evident by enhanced cleaved-caspase 3 expression. This mechanotherapy offers a clinically translatable approach by utilizing widely available FUS technology, applicable to treat additional cancer types.

An antibody-toxin conjugate targeting CD47 linked to the bacterial toxin listeriolysin O for cancer immunotherapy

Antigen-presenting cells phagocytose tumor cells and subsequently cross-present tumor-derived antigens. However, these processes are impeded by phagocytosis checkpoints and inefficient cytosolic transport of antigenic peptides from phagolysosomes. Here, using a microbial-inspired strategy, we engineered an antibody-toxin conjugate (ATC) that targets the 'don't eat me' signal CD47 linked to the bacterial toxin listeriolysin O from the intracellular bacterium Listeria monocytogenes via a cleavable linker (CD47-LLO). CD47-LLO promotes cancer cell phagocytosis by macrophages followed by LLO release and activation to form pores on phagolysosomal membranes that enhance antigen cross-presentation of tumor-derived peptides and activate cytosolic immune sensors. CD47-LLO treatment in vivo significantly inhibited the growth of both localized and metastatic breast and melanoma tumors and improved animal survival as a monotherapy or in combination with checkpoint blockade. Together, these results demonstrate that designing ATCs to promote immune recognition of tumor cells represents a promising therapeutic strategy for treating multiple cancers.

Ligand-binding assays validated for quantitative bioanalysis of a novel antibody-drug conjugate in monkey serum and related application in a nonclinical study

BACKGROUND

Antibody-drug conjugates (ADCs) are an emerging class of targeted therapeutics and are receiving growing attention in the pharmaceutical field. Here we aimed to validate two ligand binding assays for the quantitation of GQ1001, an ADC made of Trastuzumab site-specifically conjugated with DM1, in cynomolgus monkey serum, and then apply the validated assays to a nonclinical study.

METHODS

The quantitative methods for conjugated GQ1001 and total GQ1001 were validated against regulatory guidance documents on bioanalytical method validation under a Good Laboratory Practice (GLP)-compliant environment. The validated assays were applied to a single-dose pharmacokinetic (PK) study of GQ1001 conducted in cynomolgus monkeys.

RESULTS

Both intra- and inter-assay precision and accuracy met the priori-defined acceptance criteria. Neither matrix effect nor hemolysis effect were observed, and the impact of specific interferents on the assays was evaluated. Dilution linearity was good with the expected dilution factors and no hook effect till up to 20.2 mg/mL of GQ1001 was noted. Besides, the stability of the ADC in monkey serum was found to be sufficient to cover the time required for sample storage and analysis. Furthermore, the assays demonstrated good parallelism determined with a study sample and good reproducibility acquired by incurred sample reanalysis (ISR). Using the validated assays, we obtained serum concentrations for the conjugated GQ1001 and the total GQ1001 in the single-dose PK study, and thereafter, evaluated their exposures over the dosing period.

CONCLUSIONS

All tested performance parameters of the assays met the validation acceptance criteria, which supported the application of the two assays in the nonclinical PK study and allowed the evaluation of the related PK parameters for GQ1001.

Lignin-Based Nanocarrier for Simultaneous Delivery of 131I and SN-38 in the Combined Treatment of Solid Tumors by a Nanobrachytherapy Approach

Background: The rapid rise in cancer incidence significantly augments efforts to improve cancer treatments. A multimodal approach in the nanobrachytherapy of solid tumors is one of the promising methods under investigation. This study presents a novel biocompatible lignin-based nanomaterial, loaded with cytostatic agent SN-38 and radionuclide 131I, for simultaneous radiation and chemotherapy of solid tumors by a nanobrachytherapy approach. Method: Nanoparticles of ~100 nm in size, composed of lignin alone or loaded with 10% (m/m) of SN-38 (SN-38@lignin), were synthesized using a bottom-up approach and characterized. Subsequent radiolabeling of the nanoparticles by 131I produced 131I-lignin and 131I-SN-38@lignin. Their antitumor efficiency was tested against luciferase-expressing 4T1 mouse breast cancer xenografts of ~100 mm3 size on Balb/c mice. Results: An intratumoral injection of 1.85 MBq of 131I-lignin was retained within the tumor and achieved a moderate twofold decrease in tumor size compared to the control group. Injecting SN-38@lignin containing 25 µg of SN-38 decreased tumor size 3.5-fold. The therapy using the same doses of 131I-SN-38@lignin produced the most potent antitumor effect, with tumors being 6-fold smaller and having extensive intratumoral necrosis, all of it without signs of systemic toxicity. Conclusions: These results support the intratumoral delivery of lignin-based nanomaterial carrying radioisotopes and camptothecins for effective multimodal anticancer therapy.

Key considerations based on pharmacokinetic/pharmacodynamic in the design of antibody-drug conjugates

Background

Antibody-drug conjugate (ADC) is an anticancer drug that links toxins to specifically targeted antibodies via linkers, offering the advantages of high target specificity and high cytotoxicity. However, complexity of its structural composition poses a greater difficulty for drug design studies.

Objectives

Pharmacokinetic/pharmacodynamic (PK/PD) based consideration of ADCs has increasingly become a hot research topic for optimal drug design in recent years, providing possible ideas for obtaining ADCs with desirable properties.

Methods

From the assessment of the ADC action process based on PK/PD, we introduce the main research strategies of ADCs. In addition, we investigated the strategies to solve the prominent problems of ADC in the clinic in recent years, and summarized and evaluated the specific ways to optimize various problems of ADC based on the PK/PD model from two perspectives of optimizing the structure and properties of the drugs themselves. Through the selection of target antigen, the optimization of the linker, the optimization of novel small molecule toxins as payload, the optimization of ADC, overcoming the multi-drug resistance of ADC, improving the ADC tumor penetration of ADC, surface modification of ADC and surface bystander effect of ADC provide a more comprehensive and accurate framework for designing new ADCs.

Results

We've expounded comprehensively on applying pharmacokinetics or pharmacodynamics while designing ADC to obtain higher efficacy and fewer side effects. From the ADC's PK/PD property while coming into play in vivo and the PK/PD study strategy, to specific ADC optimization methods and recommendations based on PK/PD, it has been study-approved that the PK/PD properties exert a subtle role in the development of ADC, whether in preclinical trials or clinical promotion.

Conclusion

The study of PK/PD unfolds the detailed mechanism of ADC action, making it easier to control related parameters in the process of designing ADC, limited efficacy and inevitable off-target toxicity remain a challenging bottleneck.

PK/PD Evaluation of Antibody-Drug Conjugates with Enhanced Immune Effector Functions

Optimizing the interaction between antibody (mAb)-based therapeutics and immune effector functions (EFs) offers opportunities to improve the therapeutic window of these molecules. However, the role of EFs in antibody-drug conjugate (ADC) efficacy and toxicity remains unknown, with limited studies that have investigated how modulation of EF affects the pharmacology of ADCs. This study aimed to evaluate the effect of EF modulation on ADC efficacy using trastuzumab-vc-MMAE as a model ADC. A series of ADCs with enhanced or eradicated EF were synthesized through Fc engineering of the antibody. Cell-based assays confirmed that the alteration of EFs in ADCs did not change their in vitro potency, and the conjugation of vc-MMAE did not alter the trends in EFs modulation. Pharmacokinetic/pharmacodynamic (PK/PD) studies of Fc engineered ADCs were conducted in a syngeneic mouse system. The enhancement of EFs led to lower systemic exposure, faster clearance, and potentially enhanced tissue distribution and accumulation of ADCs. ADCs with enhanced EFs demonstrated improved efficacy in the syngeneic mouse tumor model, which was quantitatively confirmed by PK/PD modeling. The model indicated that EF enhancement was synergistic for ADC efficacy, whereas the complete removal of EF was less than additive. Our study suggests that developing ADCs with enhanced EF may improve the therapeutic effectiveness of ADCs, although the effect of this modification on ADC safety and extrapolation of our findings to other ADCs necessitates further investigation.

Development of a generalized pharmacokinetic model to characterize clinical pharmacokinetics of monomethyl auristatin E-based antibody-drug conjugates

AIMS

This study aims to develop a generalized pharmacokinetic (PK) model for monomethyl auristatin E (MMAE)-based antibody-drug conjugates (ADCs) that can simultaneously capture the PK of multiple ADC analytes commonly measured in the clinic.

METHODS

A comprehensive literature review was conducted to collect PK data on MMAE-based ADCs from clinical trials. From each study, PK profiles of total antibody, the ADC, conjugated MMAE, and unconjugated MMAE, were extracted. These data were pooled and dose-normalized to evaluate the generalizability of PK across various ADCs and dose levels. Upon confirming PK generalizability, a generalized PK model for MMAE-based ADCs was developed using the entire dataset. Furthermore, exposure metrics ( C max and AUC) reported across the range of doses were combined to establish linear relationships between dose and exposure metrics for MMAE-based ADCs.

RESULTS

A total of 109 PK profiles from 18 distinct MMAE-based ADCs were gathered. The dose-normalized PK profiles supported the generalizability of PK for MMAE-based ADCs. A generalized PK model was developed, which enabled capturing the PK data for 4 ADC analytes across all collected MMAE-based ADCs. A linear relationship between dose and PK exposure metrics was established, enabling the prediction of typical exposure values across different doses for MMAE-based ADCs.

CONCLUSIONS

This study comprehensively analysed clinical PK data from different valine-citrulline (vc)-MMAE-based ADCs. The generalized PK model developed here serves as an important tool for a priori prediction of the PK for multiple ADC analytes in clinical settings and lays the foundation for establishing generalized exposure-response and exposure-toxicity correlations for MMAE-based ADCs.

Spotlight on ideal target antigens and resistance in antibody-drug conjugates: Strategies for competitive advancement

Antibody-drug conjugates (ADCs) represent a novel and promising approach in targeted therapy, uniting the specificity of antibodies that recognize specific antigens with payloads, all connected by the stable linker. These conjugates combine the best targeted and cytotoxic therapies, offering the killing effect of precisely targeting specific antigens and the potent cell-killing power of small molecule drugs. The targeted approach minimizes the off-target toxicities associated with the payloads and broadens the therapeutic window, enhancing the efficacy and safety profile of cancer treatments. Within precision oncology, ADCs have garnered significant attention as a cutting-edge research area and have been approved to treat a range of malignant tumors. Correspondingly, the issue of resistance to ADCs has gradually come to the fore. Any dysfunction in the steps leading to the ADCs' action within tumor cells can lead to the development of resistance. A deeper understanding of resistance mechanisms may be crucial for developing novel ADCs and exploring combination therapy strategies, which could further enhance the clinical efficacy of ADCs in cancer treatment. This review outlines the brief historical development and mechanism of ADCs and discusses the impact of their key components on the activity of ADCs. Furthermore, it provides a detailed account of the application of ADCs with various target antigens in cancer therapy, the categorization of potential resistance mechanisms, and the current state of combination therapies. Looking forward, breakthroughs in overcoming technical barriers, selecting differentiated target antigens, and enhancing resistance management and combination therapy strategies will broaden the therapeutic indications for ADCs. These progresses are anticipated to advance cancer treatment and yield benefits for patients.

A platform technology for ultra-long acting intratumoral therapy

Intratumoral (IT) therapy is a powerful method of controlling tumor growth, but a major unsolved problem is the rapidity that injected drugs exit tumors, limiting on-target exposure and efficacy. We have developed a generic long acting IT delivery system in which a drug is covalently tethered to hydrogel microspheres (MS) by a cleavable linker; upon injection the conjugate forms a depot that slowly releases the drug and "bathes" the tumor for long periods. We established technology to measure tissue pharmacokinetics and studied MSs attached to SN-38, a topoisomerase 1 inhibitor. When MS ~ SN-38 was injected locally, tissues showed high levels of SN-38 with a long half-life of ~ 1 week. IT MS ~ SN-38 was ~ tenfold more efficacious as an anti-tumor agent than systemic SN-38. We also propose and provide an example that long-acting IT therapy might enable safe use of two drugs with overlapping toxicities. Here, long-acting IT MS ~ SN-38 is delivered with concurrent systemic PARP inhibitor. The tumor is exposed to both drugs whereas other tissues are exposed only to the systemic drug; synergistic anti-tumor activity supported the validity of this approach. We propose use of this approach to increase efficacy and reduce toxicities of combinations of immune checkpoint inhibitors such as αCTLA-4 and αPD-1.

Pharmacokinetics and pharmacodynamics of antibody-drug conjugates for the treatment of patients with breast cancer

INTRODUCTION

Currently three antibody-drug-conjugates (ADC) are approved by the European Medicines Agency (EMA) for treatment of breast cancer (BC) patient: trastuzumab-emtansine, trastuzumab-deruxtecan and sacituzumab-govitecan. ADC are composed of a monoclonal antibody (mAb) targeting a specific antigen, a cytotoxic payload and a linker. Pharmacokinetics (PK) and pharmacodynamics (PD) distinguish ADC from conventional chemotherapy and must be understood by clinicians.

AREAS COVERED

Our review delineates the PK/PD profiles of ADC approved for the treatment of BC with insight for future development. This is an expert opinion literature review based on the EMA's Assessment Reports, enriched by a comprehensive literature search performed on Medline in August 2023.

EXPERT OPINION

All three ADC distributions are described by a two-compartment structure: tissue and serum. Payload concentration peak is immediate but remains at low concentration. The distribution varied for all ADC only with body weight. mAb will be metabolised firstly by the saturable complex formation of ADC/Tumour-Receptor and secondly by binding of FcgRs in immune cells. They are all excreted in the bile and faeces with minimal urine elimination. Dose adjustments, apart from weight, are not recommended. Novel ADC are composed of cleavable linkers with various targets/payloads with the same PK/PD properties, but novel structures of ADC are in development.

Immunotherapeutic Agents for Intratumoral Immunotherapy

Immunotherapy using systemic immune checkpoint inhibitors (ICI) and chimeric antigen receptor (CAR) T cells has revolutionized cancer treatment, but it only benefits a subset of patients. Systemic immunotherapies cause severe autoimmune toxicities and cytokine storms. Immune-related adverse events (irAEs) plus the immunosuppressive tumor microenvironment (TME) have been linked to the inefficacy of systemic immunotherapy. Intratumoral immunotherapy that increases immunotherapeutic agent bioavailability inside tumors could enhance the efficacy of immunotherapies and reduce systemic toxicities. In preclinical and clinical studies, intratumoral administration of immunostimulatory agents from small molecules to xenogeneic cells has demonstrated antitumor effects not only on the injected tumors but also against noninjected lesions. Herein, we review and discuss the results of these approaches in preclinical models and clinical trials to build the landscape of intratumoral immunotherapeutic agents and we describe how they stimulate the body's immune system to trigger antitumor immunity as well as the challenges in clinical practice. Systemic and intratumoral combination immunotherapy would make the best use of the body's immune system to treat cancers. Combining precision medicine and immunotherapy in cancer treatment would treat both the mutated targets in tumors and the weakened body's immune system simultaneously, exerting maximum effects of the medical intervention.

Optimizing the safety of antibody-drug conjugates for patients with solid tumours

Over the past 5 years, improvements in the design of antibody-drug conjugates (ADCs) have enabled major advances that have reshaped the treatment of several advanced-stage solid tumours. Considering the intended rationale behind the design of ADCs, which is to achieve targeted delivery of cytotoxic molecules by linking them to antibodies targeting tumour-specific antigens, ADCs would be expected to be less toxic than conventional chemotherapy. However, most ADCs are still burdened by off-target toxicities that resemble those of the cytotoxic payload as well as on-target toxicities and other poorly understood and potentially life-threatening adverse effects. Given the rapid expansion in the clinical indications of ADCs, including use in curative settings and various combinations, extensive efforts are ongoing to improve their safety. Approaches currently being pursued include clinical trials optimizing the dose and treatment schedule, modifications of each ADC component, identification of predictive biomarkers for toxicities, and the development of innovative diagnostic tools. In this Review, we describe the determinants of the toxicities of ADCs in patients with solid tumours, highlighting key strategies that are expected to improve tolerability and enable improvements in the treatment outcomes of patients with advanced-stage and those with early stage cancers in the years to come.