Single domain antibody-scFv conjugate targeting amyloid ß and TfR penetrates the blood-brain barrier and interacts with amyloid ß.

Neurodegenerative diseases such as Alzheimer's disease (AD) pose substantial challenges to patients and health-care systems, particularly in countries with aging populations. Immunotherapies, including the marketed antibodies lecanemab (Leqembi®) and donanemab (KisunlaTM), offer promise but face hurdles due to limited delivery across the blood-brain barrier (BBB). This limitation necessitates high doses, resulting in increased costs and a higher risk of side effects. This study explores transferrin receptor (TfR)-binding camelid single-domain antibodies (VHHs) for facilitated brain delivery. We developed and evaluated fusion proteins (FPs) combining VHHs with human IgG Fc domains or single-chain variable fragments (scFvs) of the anti-amyloid-beta (Aß) antibody 3D6. In vitro assessments showed varying affinities of the FPs for TfR. In vivo evaluations indicated that specific VHH-Fc and VHH-scFv fusions reached significant brain concentrations, emphasizing the importance of optimal TfR binding affinities. The VHH-scFv fusions were further investigated in mouse models with Aß pathology, showing higher retention compared to wild-type mice without Aß pathology. Our findings suggest that these novel VHH-based FPs hold potential for therapeutic and diagnostic applications in AD, providing a strategy to overcome BBB limitations and enhance brain targeting of antibody-based treatments. Furthermore, our results suggest that a given bispecific TfR-binding fusion format has a window of "optimal" affinity where parenchymal delivery is adequate, while blood pharmacokinetics aligns with the desired application of the fusion protein.

A general perspective for the conduct of radiolabelled distribution, metabolism, and excretion studies for antibody-drug conjugates.

Antibody-drug conjugates (ADCs) are a class of biopharmaceuticals that combine the specificity of monoclonal antibodies (mAbs) with the cytotoxicity of small molecule drugs. 15 ADCs have been approved by regulatory authorities up to now, mainly for indications in oncology, however, this review paper will only focus on the 13 ADCs that have been approved by either the FDA or EMA.ADME (Absorption, Distribution, Metabolism, and Excretion) studies are essential for the development of small molecule drugs to evaluate their disposition properties. These studies help to select drug candidates, determine the optimal dosing regimen and help to identify potential safety concerns for the drug of interest in human. Tissue distribution studies are also important as they facilitate the understanding of the efficacy and safety for parent drug and its metabolites in preclinical and clinical studies.For biologics, ADME studies are usually not required. In this paper, we review the existing approval packages and literature for approved ADCs to determine the extent of ADME studies performed as part of ADC registration packages.We conclude that ADME studies are recommended for the development of ADCs if new linkers and payloads are used that have never been used in humans before as these studies provide valuable information on the pharmacokinetic properties, optimal dosing regimen, and potential safety concerns. However, for the development of ADCs with established linker payload combinations, radiolabelled ADME studies may not be necessary if the distribution, metabolism and excretion properties have been described before. Clinical radiolabelled ADME studies are not recommended where patients are treated for life threating diseases like for indications in oncology.

A modelling approach to compare ADC deconjugation and systemic elimination rates of individual drug-load species using native ADC LC-MS data from human plasma.

Native liquid chromatography mass spectrometry (LC-MS) is a commonly used approach for intact analysis of inter-chain cysteine conjugated antibody-drug conjugates (ADCs). Coupling native LC-MS with affinity capture provides a platform for intact ADC analysis from in vivo samples and characterisation of individual drug load species, specifically the impact of drug linker deconjugation, hydrolysis, and differential clearance in a biological system.This manuscript describes data generated from native LC-MS analysis of ADCs from human plasma, both in vitro incubations and clinical samples. It also details the pharmacokinetic (PK) model built to specifically characterise the disposition of individual drug load species from MMAE and MMAF interchain cysteine conjugated ADCs.In vitro deconjugation and hydrolysis rates were similar across both ADCs. Differential clearance of higher loaded species in vivo was pronounced for the MMAE conjugated ADC, while systemic elimination after accounting for deconjugation was similar across drug loads for the MMAF conjugated ADC. This is the first report of affinity capture native LC-MS analysis, and subsequent modelling of deconjugation, hydrolysis and clearance rates of individual drug load species using clinical data from cysteine conjugated ADCs.

Use of stable isotope labeled (SIL) antibodies in cassette dosing to improve pharmacokinetics screening efficiency of ADCs with novel cytotoxic payloads.

Stable isotope labelling by amino acids in cell culture (SILAC) is an established technique used in quantitative mass spectrometry (MS)-based proteomics. SILAC is also used to generate stable isotope labelled (SIL) antibodies for internal standards (IS) used in LC-MS/MS bioassays to improve quantitative robustness.Total antibody (TAb) is measured to evaluate pharmacokinetics (PK) of antibody drug conjugate (ADC) candidates measured by either ligand binding (LBA) or LC-MS/MS. Herein, we describe an application of SILAC, where multiple SIL combinations of an antibody are used for cassette dosing and PK evaluation.Our preclinical studies demonstrate SILAC-labelled ADC therapeutics did not alter antibody PK. Furthermore, with cassette dosing SIL antibodies exhibited comparable exposure to discretely administered unlabelled test articles in rats.In addition, SIL antibodies were conjugated to cytotoxic payloads to create SIL ADCs and cassette dosed in a cynomolgus monkey PK study and SIL ADCs yielded comparable PK results to discrete dosed unlabelled ADCs.In conclusion, SIL antibodies used with a cassette dosing strategy increases PK screening throughput of ADC candidates in preclinical species. Additionally, cassette dosing strategy further facilitates the responsible use of laboratory animals to achieve the three-Rs (Replacement, Reduction, and Refinement).

Molecular Imaging of p53 in Mouse Models of Cancer Using a Radiolabeled Antibody TAT Conjugate with SPECT.

Mutations of p53 protein occur in over half of all cancers, with profound effects on tumor biology. We present the first-to our knowledge-method for noninvasive visualization of p53 in tumor tissue in vivo, using SPECT, in 3 different models of cancer. Methods: Anti-p53 monoclonal antibodies were conjugated to the cell-penetrating transactivator of transcription (TAT) peptide and a metal ion chelator and then radiolabeled with 111In to allow SPECT imaging. 111In-anti-p53-TAT conjugates were retained longer in cells overexpressing p53-specific than non-p53-specific 111In-mIgG (mouse IgG from murine plasma)-TAT controls, but not in null p53 cells. Results: In vivo SPECT imaging showed enhanced uptake of 111In-anti-p53-TAT, versus 111In-mIgG-TAT, in high-expression p53R175H and medium-expression wild-type p53 but not in null p53 tumor xenografts. The results were confirmed in mice bearing genetically engineered KPC mouse-derived pancreatic ductal adenocarcinoma tumors. Imaging with 111In-anti-p53-TAT was possible in KPC mice bearing spontaneous p53R172H pancreatic ductal adenocarcinoma tumors. Conclusion: We demonstrate the feasibility of noninvasive in vivo molecular imaging of p53 in tumor tissue using a radiolabeled TAT-modified monoclonal antibody.

Preclinical Evaluation of STI-8811, a Novel Antibody-Drug Conjugate Targeting BCMA for the Treatment of Multiple Myeloma.

Treatment for patients with multiple myeloma has experienced rapid development and improvement in recent years; however, patients continue to experience relapse, and multiple myeloma remains largely incurable. B-cell maturation antigen (BCMA) has been widely recognized as a promising target for treatment of multiple myeloma due to its exclusive expression in B-cell linage cells and its critical role in the growth and survival of malignant plasma cells. Here, we introduce STI-8811, a BCMA-targeting antibody-drug conjugate (ADC) linked to an auristatin-derived duostatin payload via an enzymatically cleavable peptide linker, using our proprietary C-lock technology. STI-8811 exhibits target-specific binding activity and rapid internalization, leading to G2/M cell-cycle arrest, caspase 3/7 activation, and apoptosis in BCMA-expressing tumor cells in vitro. Soluble BCMA (sBCMA) is shed by multiple myeloma cells into the blood and increases with disease progression, competing for ADC binding and reducing its efficacy. We report enhanced cytotoxic activity in the presence of high levels of sBCMA compared with a belantamab mafodotin biosimilar (J6M0-mcMMAF). STI-8811 demonstrated greater in vivo activity than J6M0-mcMMAF in solid and disseminated multiple myeloma models, including tumor models with low BCMA expression and/or in large solid tumors representing soft-tissue plasmacytomas. In cynomolgus monkeys, STI-8811 was well tolerated, with toxicities consistent with other BCMA-targeting ADCs with auristatin payloads in clinical studies. STI-8811 has the potential to outperform current clinical candidates with lower toxicity and higher activity under conditions found in patients with advanced disease. Significance: STI-8811 is a BCMA-targeting ADC carrying a potent auristatin derivative. We report unique binding properties which maintain potent cytotoxic activity under sBCMA-high conditions that hinder the clinical efficacy of current BCMA-targeting ADC candidates. Beyond disseminated models of multiple myeloma, we observed efficacy in solid tumor models of plasmacytomas with low and heterogenous BCMA expressions at a magnitude and duration of response exceeding that of clinical comparators.

Structure-Activity Relationship of Antibody-Oligonucleotide Conjugates: Evaluating Bioconjugation Strategies for Antibody-Phosphorodiamidate Morpholino Oligomer Conjugates for Drug Development.

Antibody-oligonucleotide conjugates (AOCs) are promising treatments for Duchenne muscular dystrophy (DMD). They work via induction of exon skipping and restoration of dystrophin protein in skeletal and heart muscles. The structure-activity relationships (SARs) of AOCs comprising antibody-phosphorodiamidate morpholino oligomers (PMOs) depend on several aspects of their component parts. We evaluate the SAR of antimouse transferrin receptor 1 antibody (αmTfR1)-PMO conjugates: cleavable and noncleavable linkers, linker location on the PMO, and the impact of drug-to-antibody ratios (DARs) on plasma pharmacokinetics (PK), oligonucleotide delivery to tissues, and exon skipping. AOCs containing a stable linker with a DAR9.7 were the most effective PMO delivery vehicles in preclinical studies. We demonstrate that αmTfR1-PMO conjugates induce dystrophin protein restoration in the skeletal and heart muscles of mdx mice. Our results show that αmTfR1-PMO conjugates are a potentially effective approach for the treatment of DMD.

Locally unlocks prodrugs by radiopharmaceutical in tumor for cancer therapy.

Chemotherapy is the first-line treatment for cancer, but its systemic toxicity can be severe. Tumor-selective prodrug activation offers promising opportunities to reduce systemic toxicity. Here, we present a strategy for activating prodrugs using radiopharmaceuticals. This strategy enables the targeted release of chemotherapeutic agents due to the high tumor-targeting capability of radiopharmaceuticals. [18F]FDG (2-[18F]-fluoro-2-deoxy-D-glucose), one of the most widely used radiopharmaceuticals in clinics, can trigger Pt(IV) complex for controlled release of axial ligands in tumors, it might be mediated by hydrated electrons generated by water radiolysis resulting from the decay of radionuclide 18F. Its application offers the controlled release of fluorogenic probes and prodrugs in living cells and tumor-bearing mice. Of note, an OxaliPt(IV) linker is designed to construct an [18F]FDG-activated antibody-drug conjugate (Pt-ADC). Sequential injection of Pt-ADC and [18F]FDG efficiently releases the toxin in the tumor and remarkably suppresses the tumor growth. Radiotherapy is booming as a perturbing tool for prodrug activation, and we find that [18F]FDG is capable of deprotecting various radiotherapy-removable protecting groups (RPGs). Our results suggest that tumor-selective radiopharmaceutical may function as a trigger, for developing innovative prodrug activation strategies with enhanced tumor selectivity.

On the shoulder of ADC: The development of 124I-IMMU-132, an iodine-124-labelled Trop-2-targeting molecular probe for micro-PET imaging.

BACKGROUND: Trop-2 is closely related to the development and progression of a variety of tumours and poor prognosis. This study aimed to construct an iodine-124 (124I)-labelled antibody-drug conjugate (ADC) positron emission tomography (PET) probe which could noninvasively image Trop-2 in vivo, providing an important method for the diagnosis of tumours with high Trop-2 expression in clinical practice and monitoring their treatment. METHODS: In this study, a novel Trop-2-targeting molecular probe, 124I-IMMU-132, was constructed to better reveal the expression of Trop-2. The targeting and binding abilities of the probe to Trop-2-positive tumours were investigated in Capan-1/MDA-MB-468/Mcf-7 cells and their animal models. RESULTS: The constructed 124I-IMMU-132 probe maintained both reliable radiochemical characteristics and binding affinity (Kd = 2.200 nmol/L). The uptake of the probe by Trop-2-positive Capan-1/MDA-MB-468 cells increased in a time-dependent manner. The probe bound specifically to Capan-1/MDA-MB-468 tumours in vivo. The SUVmax Tumour/muscle ratio gradually increased with time, from 4.30 ± 0.55-10.78 ± 1.80 (p < 0.01) in the Capan-1 model and from 8.84 ± 0.95-32.20 ± 2.9 (p < 0.001) in the MDA-MB-468 model. The biodistribution and pharmacokinetics of 124I-IMMU-132 in a mouse model were consistent with the imaging results, and the dosimetry estimation in humans was acceptable. CONCLUSIONS: 124I-IMMU-132 PET is a promising imaging technique for delineating Trop-2-positive tumours. It has great potential in early diagnosis and targeted selection of patients that could benefit from its application.

Beyond cytotoxic potency: disposition features required to design ADC payload.

1. Antibody-drug conjugates (ADCs) have demonstrated impressive clinical usefulness in treating several types of cancer, with the notion of widening of the therapeutic index of the cytotoxic payload through the minimisation of the systemic toxicity. Therefore, choosing the most appropriate payload molecule is a particularly important part of the early design phase of ADC development, especially given the highly competitive environment ADCs find themselves in today.2. The focus of the current review is to describe critical attributes/considerations needed in the discovery and ultimately development of cytotoxic payloads in support of ADC design. In addition to potency, several key dispositional characteristics including solubility, permeability and bystander effect, pharmacokinetics, metabolism, and drug-drug interactions, are described as being an integral part of the integrated activities required in the design of clinically safe and useful ADC therapeutic agents.

Antibody-Drug Conjugates in the Pipeline for Treatment of Melanoma: Target and Pharmacokinetic Considerations.

Melanoma is an aggressive, rapidly developing form of skin cancer that affects about 22 per 100,000 individuals. Treatment options for melanoma patients are limited and typically involve surgical excision of moles and chemotherapy. Survival has been improved in recent years through targeted small molecule inhibitors and antibody-based immunotherapies. However, the long-term side effects that arise from taking chemotherapies can negatively impact the lives of patients because they lack specificity and impact healthy cells along with the cancer cells. Antibody-drug conjugates are a promising new class of drugs for the treatment of melanoma. This review focuses on the development of antibody-drug conjugates for melanoma and discusses the existing clinical trials of antibody-drug conjugates and their use as a melanoma treatment. So far, the antibody-drug conjugates have struggled from efficacy problems, with modest effects at best, leading many to be discontinued for melanoma. At the same time, conjugates such as AMT-253, targeting melanoma cell adhesion molecule, and mecbotamab vedotin  targeting AXL receptor tyrosine kinase, are among the most exciting for melanoma treatment in the future.

Imaging with [89Zr]Zr-DFO-SC16.56 anti-DLL3 antibody in patients with high-grade neuroendocrine tumours of the lung and prostate: a phase 1/2, first-in-human trial.

BACKGROUND: Delta-like ligand 3 (DLL3) is aberrantly expressed on the surface of small-cell lung cancer (SCLC) and neuroendocrine prostate cancer cells. We assessed the safety and feasibility of the DLL3-targeted imaging tracer [89Zr]Zr-DFO-SC16.56 (composed of the anti-DLL3 antibody SC16.56 conjugated to p-SCN-Bn-deferoxamine [DFO] serving as a chelator for zirconium-89) in patients with neuroendocrine-derived cancer. METHODS: We conducted an open-label, first-in-human study of immunoPET-CT imaging with [89Zr]Zr-DFO-SC16.56. The study was done at Memorial Sloan Kettering Cancer Center, New York, NY, USA. Patients aged 18 years or older with a histologically verified neuroendocrine-derived malignancy and an Eastern Cooperative Oncology Group performance status of 0-2 were eligible. An initial cohort of patients with SCLC (cohort 1) received 37-74 MBq [89Zr]Zr-DFO-SC16.56 as a single intravenous infusion at a total mass dose of 2·5 mg and had serial PET-CT scans at 1 h, day 1, day 3, and day 7 post-injection. The primary outcomes of phase 1 of the study (cohort 1) were to estimate terminal clearance half-time, determine whole organ time-integrated activity coefficients, and assess the safety of [89Zr]Zr-DFO-SC16.56. An expansion cohort of additional patients (with SCLC, neuroendocrine prostate cancer, atypical carcinoid tumours, and non-small-cell lung cancer; cohort 2) received a single infusion of [89Zr]Zr-DFO-SC16.56 at the same activity and mass dose as in the initial cohort followed by a single PET-CT scan 3-6 days later. Retrospectively collected tumour biopsy samples were assessed for DLL3 by immunohistochemistry. The primary outcome of phase 2 of the study in cohort 2 was to determine the potential association between tumour uptake of the tracer and intratumoural DLL3 protein expression, as determined by immunohistochemistry. This study is ongoing and is registered with ClinicalTrials.gov, NCT04199741. FINDINGS: Between Feb 11, 2020, and Jan 30, 2023, 12 (67%) men and six (33%) women were enrolled, with a median age of 64 years (range 23-81). Cohort 1 included three patients and cohort 2 included 15 additional patients. Imaging of the three patients with SCLC in cohort 1 showed strong tumour-specific uptake of [89Zr]Zr-DFO-SC16.56 at day 3 and day 7 post-injection. Serum clearance was biphasic with an estimated terminal clearance half-time of 119 h (SD 31). The highest mean absorbed dose was observed in the liver (1·83 mGy/MBq [SD 0·36]), and the mean effective dose was 0·49 mSv/MBq (SD 0·10). In cohort 2, a single immunoPET-CT scan on day 3-6 post-administration could delineate DLL3-avid tumours in 12 (80%) of 15 patients. Tumoural uptake varied between and within patients, and across anatomical sites, with a wide range in maximum standardised uptake value (from 3·3 to 66·7). Tumour uptake by [89Zr]Zr-DFO-SC16.56 was congruent with DLL3 immunohistochemistry in 15 (94%) of 16 patients with evaluable tissue. Two patients with non-avid DLL3 SCLC and neuroendocrine prostate cancer by PET scan showed the lowest DLL3 expression by tumour immunohistochemistry. One (6%) of 18 patients had a grade 1 allergic reaction; no grade 2 or worse adverse events were noted in either cohort. INTERPRETATION: DLL3 PET-CT imaging of patients with neuroendocrine cancers is safe and feasible. These results show the potential utility of [89Zr]Zr-DFO-SC16.56 for non-invasive in-vivo detection of DLL3-expressing malignancies. FUNDING: National Institutes of Health, Prostate Cancer Foundation, and Scannell Foundation.

Can we do better with Mylotarg? Model-based assessment of opportunities to improve therapeutic index.

Late-stage clinical trial failures increase the overall cost and risk of bringing new drugs to market. Determining the pharmacokinetic (PK) drivers of toxicity and efficacy in preclinical studies and early clinical trials supports quantitative optimization of drug schedule and dose through computational modeling. Additionally, this approach permits prioritization of lead candidates with better PK properties early in development. Mylotarg is an antibody-drug conjugate (ADC) that attained U.S. Food and Drug Administration (FDA) approval under a fractionated dosing schedule after 17 years of clinical trials, including a 10-year period on the market resulting in hundreds of fatal adverse events. Although ADCs are often considered lower risk for toxicity due to their targeted nature, off-target activity and liberated payload can still constrain dosing and drive clinical failure. Under its original schedule, Mylotarg was dosed infrequently at high levels, which is typical for ADCs because of their long half-lives. However, our PK modeling suggests that these regimens increase maximum plasma concentration (Cmax)-related toxicities while producing suboptimal exposures to the target receptor. Our analysis demonstrates that the benefits of dose fractionation for Mylotarg tolerability should have been obvious early in the drug's clinical development and could have curtailed the proliferation of ineffective Phase III studies. We also identify schedules likely to be even more efficacious without compromising on tolerability. Alternatively, a longer-circulating Mylotarg formulation could obviate the need for dose fractionation, allowing superior patient convenience. Early-stage PK optimization through quantitative modeling methods can accelerate clinical development and prevent late-stage failures.

Imaging and Monitoring HER2 Expression in Tumors during HER2 Antibody-Drug Conjugate Therapy Utilizing a Radiolabeled Site-Specific Single-Domain Antibody Probe: 68Ga-NODAGA-SNA004-GSC.

The overexpression of HER2 is pivotal in the initiation and progression of breast cancer. Developing HER2-targeted radiotracers is crucial for noninvasive assessment of HER2 expression, patient selection for HER2-targeted therapy, monitoring treatment response, and identifying resistance. Here, we reported a nonsite-specific coupled radiotracer, 68Ga-NOTA-SNA004-His6, and a site-specific coupled radiotracer, 68Ga-NODAGA-SNA004-GSC, based on a novel HER2 nanobody, SNA004. Both radiotracers exhibited high affinity, specific targeting, and rapid clearance in vitro and in vivo. Additionally, these tracers and trastuzumab showed noncompetitive binding to HER2. Compared to 68Ga-NOTA-SNA004-His6, 68Ga-NODAGA-SNA004-GSC demonstrated significantly reduced renal and liver uptake. PET/CT imaging with 68Ga-NODAGA-SNA004-GSC sensitively detected the responsiveness of various tumor models to trastuzumab and its antibody-drug conjugates (ADCs). Overall, the site-specific coupled radiotracer 68Ga-NODAGA-SNA004-GSC offered significant advantages in biodistribution and signal-to-noise ratio, making it a valuable tool for monitoring HER2 expression levels before, during, and after trastuzumab and ADC treatment.

Time-varying brentuximab vedotin pharmacokinetics and weight-based dosing in paediatric patients despite lower exposure in those aged 2 to <6 and 6-11 years.

AIMS: We studied the pharmacokinetics and exposure-response relationships of the brentuximab vedotin (BV) antibody-drug conjugate (ADC) and unconjugated monomethyl auristatin E in haematologic malignancies. METHODS: This population pharmacokinetic analysis included data from five adult and three paediatric studies. Exposures in virtual adult and paediatric populations following BV 1.8 mg/kg (maximum 180 mg) intravenously every 3 weeks were simulated. Clinical endpoints included overall response rate, grade ≥2 peripheral neuropathy (PN) and grade ≥3 neutropenia. RESULTS: BV ADC exhibited linear pharmacokinetics, well-described by a three-compartment model, with body weight being the only significant covariate for exposure. Monomethyl auristatin E exhibited time-varying formation rate. Simulated steady-state BV ADC exposures in patients aged 12 to <18 years were similar to those of adult patients, but 23%-38% lower in patients aged 2 to <12 years. Despite lower exposure, clinical activity was observed with BV 1.8 mg/kg every 3 weeks in those aged 2 to <12 years (overall response rate: 2 to <12 years, 60%; 12 to <18 years, 43%). In adult, but not paediatric patients, increased BV ADC exposures were associated with grade ≥2 PN and grade ≥3 neutropenia occurrence. CONCLUSIONS: BV pharmacokinetics in adult and paediatric patients were consistent. BV ADC exposures were lower in patients aged 2 to <12 years vs. ≥12 years, but no apparent clinically relevant differences in efficacy, grade ≥2 PN or grade ≥3 neutropenia were observed. These data support body weight-based dosing of BV in patients irrespective of age; thus, dose adjustment in those 2 to <12 years does not appear warranted.

Safety, Efficacy, and Pharmacokinetics of SHR-A1811, a Human Epidermal Growth Factor Receptor 2-Directed Antibody-Drug Conjugate, in Human Epidermal Growth Factor Receptor 2-Expressing or Mutated Advanced Solid Tumors: A Global Phase I Trial.

PURPOSE: SHR-A1811 is an antibody-drug conjugate composed of an anti-human epidermal growth factor receptor 2 (HER2) antibody trastuzumab, a cleavable linker, and a topoisomerase I inhibitor payload. We assessed the safety, tolerability, antitumor activity, and pharmacokinetics of SHR-A1811 in heavily pretreated HER2-expressing or mutated advanced solid tumors. METHODS: This global, multi-center, first-in-human, phase I trial was conducted at 33 centers. Patients who had HER2-expressing or mutated unresectable, advanced, or metastatic solid tumors and were refractory or intolerant to standard therapies were enrolled. SHR-A1811 was administered intravenously at doses ranging from 1.0 to 8.0 mg/kg once every 3 weeks. The primary end points were dose-limiting toxicity, safety, and the recommended phase II dose. RESULTS: From September 7, 2020, to February 27, 2023, 307 patients who had undergone a median of three (IQR, 2-5) previous treatment regimens in the metastatic setting received SHR-A1811 treatment. As of data cutoff (February 28, 2023), one patient from the 6.4 mg/kg group experienced dose-limiting toxicities (pancytopenia and colitis). The most common grade 3 or higher adverse events (AEs) included decreased neutrophil count (119 [38.8%]) and decreased WBC count (70 [22.8%]). Interstitial lung disease occurred in only eight (2.6%) patients. Serious AEs and deaths occurred in 70 (22.8%) and 13 (4.2%) patients, respectively. SHR-A1811 led to objective responses in 59.9% (184/307) of all patients, 76.3% (90/118) of HER2-positive breast cancer, 60.4% (55/91) of HER2 low-expressing breast cancer, and 45.9% (39/85 with evaluable tumor responses) of the 98 nonbreast tumors. CONCLUSION: SHR-A1811 exhibited acceptable tolerability, promising antitumor activity, and a favorable pharmacokinetic profile in heavily pretreated advanced solid tumors. The recommended phase II dose of 4.8 or 6.4 mg/kg was selected for various tumor types.

Development and validation of bioanalytical assays for the quantification of 9MW2821, a nectin-4-targeting antibody-drug conjugate.

We designed and developed 9MW2821, an anti-Nectin-4 antibody-drug conjugate (ADC) with an enzymatically cleavable valine-citrulline linker and monomethyl auristatin E (MMAE) as the payload. Four bioanalytical assays for total antibodies, conjugated antibodies, conjugated payload, and free payload were then developed and validated for the comprehensive evaluation of the multiple drug forms of 9MW2821. Specific sandwich enzyme-linked immunosorbent assays were used to quantify total antibodies and conjugated antibody, showing good drug-to-antibody ratio (DAR) tolerance. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to determine free MMAE, and conjugated MMAE was quantified using a combination of ligand-binding assay (LBA) and LC-MS/MS. Based on these four assays, we studied the serum stability and monkey pharmacokinetic profiles of 9MW2821, and the in vivo DAR of 9MW2821 was calculated and dynamically monitored. In conclusion, we developed and validated series of bioanalytical assays to quantify multiple forms of 9MW2821, a new ADC, and used the assays to evaluate the serum stability and monkey pharmacokinetic characteristics. The results indicate good linker stability and suggest that the developed assays can be further used in clinical settings.

Unlocking the Potential: Biomarkers of Response to Antibody-Drug Conjugates.

Antibody-drug conjugates (ADCs) have reshaped the cancer treatment landscape across a variety of different tumor types. ADCs' peculiar pharmacologic design combines the cytotoxic properties of chemotherapeutic agents with the selectivity of targeted therapies. At present, the approval of many ADCs used in clinical practice has not always been biomarker-driven. Indeed, predicting ADCs' activity and toxicity through the demonstration of specific biomarkers is still a great unmet need, and the identification of patients who can derive significant benefit from treatment with ADCs may often be uncertain. With the lack of robust predictive biomarkers to anticipate primary, intrinsic resistance to ADCs and no consolidated biomarkers to aid in the early identification of treatment resistance (ie, acquired resistance), the determination of precise biologic mechanisms of ADC activity and safety becomes priority in the quest for better patient-centric outcomes. Of great relevance, whether the target antigen expression is a determinant of ADCs' primary activity is still to be clarified, and available data remain quite controversial. Antigen expression assessment is typically performed on tissue biopsy, hence only providing information on a specific tumor site, therefore unable to capture heterogeneous patterns of tumor antigen expression. Quantifying the expression of the target antigen across all tumor sites would help better understand tumor heterogeneity, whereas molecularly characterizing tumor-intrinsic features over time might provide information on resistance mechanisms. In addition, toxicity can represent a critical concern, since most ADCs have a safety profile that resembles that of chemotherapies, with often unique adverse events requiring special management, possibly because of the differential in pharmacokinetics between the small-molecule agent versus payload of a similar class (eg, deruxtecan conjugate-related interstitial lung disease). As such, the identification of robust predictive biomarkers of safety and activity of ADCs has the potential to improve patient selection and enrich the population of patients most likely to derive a substantial clinical benefit, especially in those disease settings where different ADCs happen to be approved in competing clinical indications, with undefined biomarkers to make precise decision making and unclear data on how to sequence ADCs. At this point, the identification of clinically actionable biomarkers in the space of ADCs remains a top research priority.

Development of Peptide Paratope Mimics Derived from the Anti-ROR1 Antibody and Long-Acting Peptide-Drug Conjugates for Targeted Cancer Therapy.

Antibody-based targeted therapy in cancer faces a challenge due to uneven antibody distribution in solid tumors, hindering effective drug delivery. We addressed this by developing peptide mimetics with nanomolar-range affinity for Receptor Tyrosine Kinase-Like Orphan Receptor 1 (ROR1) using computational methods. These peptides showed both specific targeting and deep penetration in vitro and in vivo. Additionally, we created peptide-drug conjugates (PDCs) by linking targeting peptides to toxin drugs via various linkers and enhancing their in vivo half-life with fatty side chains for albumin binding. The antitumor candidate II-3 displayed exceptional affinity (KD = 1.72 × 10-9 M), internalization efficiency, anticancer potency (IC50 = 0.015 ± 0.002 µM), and pharmacokinetics (t1/2 = 2.6 h), showcasing a rational approach for designing PDCs with favorable tissue distribution and strong tumor penetration.

Disitamab vedotin, a HER2-directed antibody-drug conjugate, in patients with HER2-overexpression and HER2-low advanced breast cancer: a phase I/Ib study.

BACKGROUND: Disitamab vedotin (DV; RC48-ADC) is an antibody-drug conjugate comprising a human epidermal growth factor receptor 2 (HER2)-directed antibody, linker and monomethyl auristatin E. Preclinical studies have shown that DV demonstrated potent antitumor activity in preclinical models of breast, gastric, and ovarian cancers with different levels of HER2 expression. In this pooled analysis, we report the safety and efficacy of DV in patients with HER2-overexpression and HER2-low advanced breast cancer (ABC). METHODS: In the phase I dose-escalation study (C001 CANCER), HER2-overexpression ABC patients received DV at doses of 0.5-2.5 mg/kg once every two weeks (Q2W) until unacceptable toxicity or progressive disease. The dose range, safety, and pharmacokinetics (PK) were determined. The phase Ib dose-range and expansion study (C003 CANCER) enrolled two cohorts: HER2-overexpression ABC patients receiving DV at doses of 1.5-2.5 mg/kg Q2W, with the recommended phase 2 dose (RP2D) determined, and HER2-low ABC patients receiving DV at doses of 2.0 mg/kg Q2W to explore the efficacy and safety of DV in HER2-low ABC. RESULTS: Twenty-four patients with HER2-overexpression ABC in C001 CANCER, 46 patients with HER2-overexpression ABC and 66 patients with HER2-low ABC in C003 CANCER were enrolled. At 2.0 mg/kg RP2D Q2W, the confirmed objective response rates were 42.9% (9/21; 95% confidence interval [CI]: 21.8%-66.0%) and 33.3% (22/66; 95% CI: 22.2%-46.0%), with median progression-free survival (PFS) of 5.7 months (95% CI: 5.3-8.4 months) and 5.1 months (95% CI: 4.1-6.6 months) for HER2-overexpression and HER2-low ABC, respectively. Common (≥5%) grade 3 or higher treatment-emergent adverse events included neutrophil count decreased (17.6%), gamma-glutamyl transferase increased (13.2%), asthenia (11.0%), white blood cell count decreased (9.6%), peripheral neuropathy such as hypoesthesia (5.9%) and neurotoxicity (0.7%), and pain (5.9%). CONCLUSION: DV demonstrated promising efficacy in HER2-overexpression and HER2-low ABC, with a favorable safety profile at 2.0 mg/kg Q2W.