Phase 1, first-in-human study of TYRP1-TCB (RO7293583), a novel TYRP1-targeting CD3 T-cell engager, in metastatic melanoma: active drug monitoring to assess the impact of immune response on drug exposure

Introduction

Although checkpoint inhibitors (CPIs) have improved outcomes for patients with metastatic melanoma, those progressing on CPIs have limited therapeutic options. To address this unmet need and overcome CPI resistance mechanisms, novel immunotherapies, such as T-cell engaging agents, are being developed. The use of these agents has sometimes been limited by the immune response mounted against them in the form of anti-drug antibodies (ADAs), which is challenging to predict preclinically and can lead to neutralization of the drug and loss of efficacy.

Methods

TYRP1-TCB (RO7293583; RG6232) is a T-cell engaging bispecific (TCB) antibody that targets tyrosinase-related protein 1 (TYRP1), which is expressed in many melanomas, thereby directing T cells to kill TYRP1-expressing tumor cells. Preclinical studies show TYRP1-TCB to have potent anti-tumor activity. This first-in-human (FIH) phase 1 dose-escalation study characterized the safety, tolerability, maximum tolerated dose/optimal biological dose, and pharmacokinetics (PK) of TYRP1-TCB in patients with metastatic melanoma (NCT04551352).

Results

Twenty participants with cutaneous, uveal, or mucosal TYRP1-positive melanoma received TYRP1-TCB in escalating doses (0.045 to 0.4 mg). All participants experienced ≥1 treatment-related adverse event (TRAE); two participants experienced grade 3 TRAEs. The most common toxicities were grade 1-2 cytokine release syndrome (CRS) and rash. Fractionated dosing mitigated CRS and was associated with lower levels of interleukin-6 and tumor necrosis factor-alpha. Measurement of active drug (dual TYPR1- and CD3-binding) PK rapidly identified loss of active drug exposure in all participants treated with 0.4 mg in a flat dosing schedule for ≥3 cycles. Loss of exposure was associated with development of ADAs towards both the TYRP1 and CD3 domains. A total drug PK assay, measuring free and ADA-bound forms, demonstrated that TYRP1-TCB-ADA immune complexes were present in participant samples, but showed no drug activity in vitro.

Discussion

This study provides important insights into how the use of active drug PK assays, coupled with mechanistic follow-up, can inform and enable ongoing benefit/risk assessment for individuals participating in FIH dose-escalation trials. Translational studies that lead to a better understanding of the underlying biology of cognate T- and B-cell interactions, ultimately resulting in ADA development to novel biotherapeutics, are needed.

2022 White Paper on Recent Issues in Bioanalysis: Enzyme Assay Validation, BAV for Primary End Points, Vaccine Functional Assays, Cytometry in Tissue, LBA in Rare Matrices, Complex NAb Assays, Spectral Cytometry, Endogenous Analytes, Extracellular Vesicles Part 2 - Recommendations on Biomarkers/CDx, Flow Cytometry, Ligand-Binding Assays Development & Validation; Emerging Technologies; Critical Reagents Deep Characterization

The 16th Workshop on Recent Issues in Bioanalysis (16th WRIB) took place in Atlanta, GA, USA on September 26-30, 2022. Over 1000 professionals representing pharma/biotech companies, CROs, and multiple regulatory agencies convened to actively discuss the most current topics of interest in bioanalysis. The 16th WRIB included 3 Main Workshops and 7 Specialized Workshops that together spanned 1 week in order to allow exhaustive and thorough coverage of all major issues in bioanalysis, biomarkers, immunogenicity, gene therapy, cell therapy and vaccines. Moreover, in-depth workshops on ICH M10 BMV final guideline (focused on this guideline training, interpretation, adoption and transition); mass spectrometry innovation (focused on novel technologies, novel modalities, and novel challenges); and flow cytometry bioanalysis (rising of the 3rd most common/important technology in bioanalytical labs) were the special features of the 16th edition. As in previous years, WRIB continued to gather a wide diversity of international, industry opinion leaders and regulatory authority experts working on both small and large molecules as well as gene, cell therapies and vaccines to facilitate sharing and discussions focused on improving quality, increasing regulatory compliance, and achieving scientific excellence on bioanalytical issues. This 2022 White Paper encompasses recommendations emerging from the extensive discussions held during the workshop and is aimed to provide the bioanalytical community with key information and practical solutions on topics and issues addressed, in an effort to enable advances in scientific excellence, improved quality and better regulatory compliance. Due to its length, the 2022 edition of this comprehensive White Paper has been divided into three parts for editorial reasons. This publication (Part 2) covers the recommendations on LBA, Biomarkers/CDx and Cytometry. Part 1 (Mass Spectrometry and ICH M10) and Part 3 (Gene Therapy, Cell therapy, Vaccines and Biotherapeutics Immunogenicity) are published in volume 15 of Bioanalysis, issues 16 and 14 (2023), respectively.

Direct bioanalysis or indirect calculation of target engagement and free drug exposure: do we apply double standards?

Analysis of "free" drug/target concentrations is important to set up appropriate pharmacokinetic-pharmacodynamic models, to evaluate active-drug exposure and target engagement. Such "free-analyte" determination could be done by direct bioanalysis using an appropriate "free-analyte" assay. Development of "free" assays is often considered challenging from a technological and regulatory perspective. The application of a "total-total" approach, where the "free-analyte" concentration is determined mathematically, is considered a more convenient option. In this perspective, we examine and discuss the challenges of this "total-total" approach, from the affinity data, the importance of applying an appropriate "total" assay, the impact of additional binding partners and the variability of the total drug/target assays and their impact on the quality and variability of the final "free-analyte" dataset.

Concerted application of LC-MS and ligand binding assays to better understand exposure of a large molecule drug

AIM

A ligand-binding assay (LBA) was used to measure exposure of PRM-151, the recombinant form of human pentraxin-2 (PTX-2), a complex pentamer with multiple binding partners. However, the assay showed a lack of dose-dependent exposure in select preclinical species and it could not differentiate the infused PRM-151 from the endogenous PTX-2 in nonhuman primates.

MATERIALS & METHODS

Instead of assessing interference from its multiple binding partners, which could be time consuming and laborious, a LC-MS assay avoid of these interference was implemented to measure 'total' drug without the use of immunoaffinity capture reagents.

RESULTS & CONCLUSION

The resultant LC-MS data confirmed the original data and the lack of dose-dependent exposure is now understood to be due to the multiple and diverse targets and functions and resultant complex biodistribution rather than an assay artifact.

2017 White Paper on recent issues in bioanalysis: a global perspective on immunogenicity guidelines & biomarker assay performance (Part 3 – LBA: immunogenicity, biomarkers and PK assays)

The 2017 11th Workshop on Recent Issues in Bioanalysis took place in Los Angeles/Universal City, California, on 3–7 April 2017 with participation of close to 750 professionals from pharmaceutical/biopharmaceutical companies, biotechnology companies, contract research organizations and regulatory agencies worldwide. WRIB was once again a 5-day, week-long event – a full immersion week of bioanalysis, biomarkers and immunogenicity. As usual, it was specifically designed to facilitate sharing, reviewing, discussing and agreeing on approaches to address the most current issues of interest including both small- and large-molecule analysis involving LC–MS, hybrid ligand-binding assay (LBA)/LC–MS and LBA approaches. This 2017 White Paper encompasses recommendations emerging from the extensive discussions held during the workshop, and is aimed to provide the bioanalytical community with key information and practical solutions on topics and issues addressed, in an effort to enable advances in scientific excellence, improved quality and better regulatory compliance. Due to its length, the 2017 edition of this comprehensive White Paper has been divided into three parts for editorial reasons. This publication (Part 3) covers the recommendations for large-molecule bioanalysis, biomarkers and immunogenicity using LBA. Part 1 (LC–MS for small molecules, peptides and small molecule biomarkers) and Part 2 (hybrid LBA/LC–MS for biotherapeutics and regulatory agencies’ inputs) are published in volume 9 of Bioanalysis, issues 22 and 23 (2017), respectively.

Evaluation of the potential use of hybrid LC–MS/MS for active drug quantification applying the ‘free analyte QC concept’

Aim: Assessment of active drug exposure of biologics may be crucial for drug development. Typically, ligand-binding assay methods are used to provide free/active drug concentrations. To what extent hybrid LC–MS/MS procedures enable correct ‘active’ drug quantification is currently under consideration. Experimental & results: The relevance of appropriate extraction condition was evaluated by a hybrid target capture immuno-affinity LC–MS/MS method using total and free/active quality controls (QCs). The rapid extraction (10 min) provided correct results, whereas overnight incubation resulted in significant overestimation of the free/active drug (monclonal antibody) concentration. Conventional total QCs were inappropriate to determine optimal method conditions in contrast to free/active QCs. Conclusion: The ‘free/active analyte QC concept’ enables development of appropriate extraction conditions for correct active drug quantification by hybrid LC–MS/MS.

3-(4-Hydroxyphenyl)propionic acid: the forgotten detection substrate for ligand-binding assay-based bioanalysis

Ligand-binding assays are ideal for routine bioanalysis, but we reason that the straightforward replacement of the conventional chromogenic horseradish peroxidase substrate, 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid, of a routinely used preclinical immunoassay to detect hIgG, with the fluorogenic 3-(4-hydroxyphenyl)propionic acid would broaden the narrow dynamic range. The replacement leads to a sensitivity of 0.47 (minimum required dilution [MRD] 10) and 1.02 (MRD 50) ng/ml, and dynamic ranges of 3.3 (MRD 10) and 3.6 (MRD 50) orders of magnitude, and thereby had improved sensitivity and dynamic range compared with other conventional colorimetric ELISAs, other ligand-binding assay technologies or LC–MS assays. Improvements in sensitivity and dynamic range were achieved for the sera of horse, mice and monkeys without assay optimization.

Validation of a ligand-binding assay for active protein drug quantification following the ‘free analyte QC concept’

Aim: Active drug assays are becoming increasingly important in protein drug development. We describe the validation of a ligand-binding assay for active protein drug quantification and address practical challenges as well as regulatory implications. Results: A bioanalytical method for active protein drug quantification was successfully validated. Validation data prove that this method can be routinely used applying the commonly accepted acceptance criteria for ligand-binding assays. Conclusion: Active drug assays are a powerful tool to elucidate the pharmacokinetic/pharmacodynamic relationship as they take into consideration the influence of various matrix components, such as soluble ligand and anti-drug antibodies. However, not all aspects of the validation concept described in the guidelines for pharmacokinetic assays can be applied to active drug assays and thus regulatory guidelines should be adapted in consequence.

Leverage nonclinical development of bispecifics by translational science

Bispecific antibody constructs (Bispecifics, bsAbs) may have greater functionality compared to established monoclonal antibodies because they bind to 2 different targets or, potentially, to 2 epitopes on the same target (dual targeting). This may result in enhanced binding avidity with preferential binding to cells that express both targets or binding to targets on different cells. However, development of these next-generation biologics, including new formats, creates unique challenges due to their increased complexity. Here we review aspects of bsAbs preclinical development programs that may increase the success rates of bsAbs in clinical development.

Quantification of a bifunctional drug in the presence of an immune response: a ligand-binding assay specific for ‘active’ drug

Aim: During development of biologics, safety and efficacy assessments are often hampered by immune responses to the treatment. The raised antidrug antibodies (ADA) might interfere with the bioanalytical method and complicate result interpretation if non-fully characterized bioanalytical methods were applied. Methods: Here, we report an approach to characterize a ligand-binding assay (LBA) for the quantification of active drug exposure of a bifunctional therapeutic protein in the presence of antidrug antibodies, by correlating LBA results with those of a cell-based PK assay. Results: A clear correlation between both assays could be observed when monoclonal and polyclonal antibodies against the toxin moiety of the drug were used as ADA surrogates, and results were confirmed with human ADA-positive sera. Conclusion: The observed correlation between the LBA-based and cell-based PK assay indicated the suitability of the developed LBA for the determination of active drug exposure in the presence of an immune response.

Workshop Report: AAPS Workshop on Method Development, Validation, and Troubleshooting of Ligand-Binding Assays in the Regulated Environment

A novel format was introduced at the recent AAPS NBC Workshop on Method Development, Validation and Troubleshooting in San Diego on 18th May 2014. The workshop format was initiated by Binodh De Silva; Marie Rock and Sherri Dudal joined the initiative to develop and chair the workshop. Questions were solicited by a variety of avenues, including a Linked-In Discussion Group. Once collated and clarified, the topics covered assay development, validation, and analysis of PK, Immunogenicity, and Biomarkers with an additional topic on alternative bioanalytical technologies. A panel of experts (workshop report co-authors) was assigned to each topic to bring forward thought-provoking aspects of each topic. The format of the workshop was developed to target the needs of bioanalytical scientists with intermediate to advanced experience in the field ranging to enable robust discussion and to delve deeper into the current bioanalytical hot topics. While the new format allowed for an interactive session with the topical discussion driven by the audience members, it did not foster equal discussion time for all of the proposed topics, especially Biomarkers and alternative LBA technologies.

Interference in immunoassays to support therapeutic antibody development in preclinical and clinical studies

During preclinical and clinical studies, immunoassays are used to measure the concentration of the therapeutic antibody, anti-drug antibodies and soluble protein biomarkers. The reliability of these assays is crucial since the results are routinely used for safety assessment and dose selection. Furthermore, soluble protein biomarkers can provide information about target engagement, proof of mechanism, proof of principle and prediction of response. Study samples mostly consist of complex matrices that can exhibit considerable interference, resulting in inaccurate measurements. This perspective discusses the source of interference and strategies to mitigate or eliminate interference in immunoassays used during preclinical and clinical drug development of drugs with a focus on the development of therapeutic antibodies.

The integration of ligand binding and LC-MS-based assays into bioanalytical strategies for protein analysis

Both LBAs and LC–MS-based assays are reviewed and summarized for applications in quantitative protein analysis. A strategy for platform selection is proposed based on several factors that contribute to the complexities of bioanalysis of biologics. Protein types, multiple co-existing forms, post-translational modifications, and affinities to ADA, targets, and endogenous proteins need to be considered when selecting the most appropriate platform. Other factors, such as intended use of data, assay sensitivity, available reagents, and multiple analytes also impact on the choice of bioanalytical platform. At BMS, strategies for the seamless integration of both platforms are being implemented to provide not only PK/PD data of the molecules but also useful information of the amino acid structure and functional relationship of the proteins.

Free analyte QC concept: a novel approach to prove correct quantification of free therapeutic protein drug/biomarker concentrations

Quantification of free drug concentrations is highly challenging due to the dynamic drug–ligand equilibrium, which may result in incorrect results. Current QC concepts do not adequately cover all of the important influencing factors: the assay itself (format and procedure); the calibration concept; the sample preparation; and the sample storage. Here, we propose a ‘free analyte QC concept’ that enables quantitative testing of these four factors and, thus, provides best possible proof of correct free drug quantification. The principle of the free analyte QC concept and an example of its application for a free drug assay is described. A comparison of this novel approach with current approaches and how the new concept fits (or does not fit) with current regulatory guidelines is discussed.

Free and total biotherapeutic evaluation in chromatographic assays: interference from targets and immunogenicity

Measurement of drug concentrations is critical during drug development, supporting evaluation of safety and efficacy in the context of pharmacokinetics. Protein-based therapeutics have been historically measured by immunoassay methods. Technological advances provide new opportunities to measure these biotherapeutics using previously incompatible chromatographic techniques, such as MS. These advances are breaking down the barriers between ‘large-molecule’ and ‘small-molecule’ bioanalysis, and pushing scientists outside their comfort zones. One challenge in measuring biotherapeutic concentration is potential impact from other matrix components, such as therapeutic target or antidrug antibodies. Depending on the specific assay development objective, target interference could be either desired (favoring free measurement) or undesired (favoring total measurement). Orthogonal techniques provide additional tools to meet this challenge. The goal of this review is to introduce both small- and large-molecule bioanalytical scientists to the opportunities and challenges to consider while evaluating orthogonal methods for biotherapeutic bioanalysis.