Enhanced Delivery of SN-38 to Human Tumor Xenografts with an Anti-Trop-2-SN-38 Antibody Conjugate (Sacituzumab Govitecan)

Trop2-targeted therapy in breast cancer

Human trophoblastic cell surface antigen 2 (Trop2) is a glycoprotein, a cellular marker of trophoblastic and stem cells, and a calcium signaling transducer involved in several signaling pathways, leading to the proliferation, invasion, and metastasis of tumors. It is expressed at a low level in normal epithelial cells, but at a high level in many tumors, making it an ideal target for cancer therapy. According to previous literature, Trop2 is broadly expressed in all breast cancer subtypes, especially in triple negative breast cancer (TNBC). Several clinical trials have demonstrated the effectiveness of Trop2-targeted therapy in breast cancer. Sacituzumab govitecan (SG) is a Trop2-targeted antibody-drug conjugate (ADC) that has been approved for the treatment of metastatic TNBC and hormone receptor-positive (HR+) and human epidermal growth factor receptor 2-negative (HER2-) breast cancer. This article reviews the structure and function of Trop2, several major Trop2-targeted ADCs, other appealing novel Trop2-targeted agents and relevant clinical trials to provide a landscape of how Trop2-targeted treatments will develop in the future.

Sacituzumab Govitecan in patients with breast cancer brain metastases and recurrent glioblastoma: a phase 0 window-of-opportunity trial

Sacituzumab Govitecan (SG) is an antibody-drug conjugate that has demonstrated efficacy in patients with TROP-2 expressing epithelial cancers. In a xenograft model of intracranial breast cancer, SG inhibited tumor growth and increased mouse survival. We conducted a prospective window-of-opportunity trial (NCT03995706) at the University of Texas Health Science Center at San Antonio to examine the intra-tumoral concentrations and intracranial activity of SG in patients undergoing craniotomy for breast cancer with brain metastases (BCBM) or recurrent glioblastoma (rGBM). We enrolled 25 patients aged ≥18 years diagnosed with BCBM and rGBM to receive a single intravenous dose of SG at 10 mg/kg given one day before resection and continued on days 1 and 8 of 21-day cycles following recovery. The PFS was 8 months and 2 months for BCBM and rGBM cohorts, respectively. The OS was 35.2 months and 9.5 months, respectively. Grade≥3 AE included neutropenia (28%), hypokalemia (8%), seizure (8%), thromboembolic event (8%), urinary tract infection (8%) and muscle weakness of the lower limb (8%). In post-surgical tissue, the median total SN-38 was 249.8 ng/g for BCBM and 104.5 ng/g for rGBM, thus fulfilling the primary endpoint. Biomarker analysis suggests delivery of payload by direct release at target site and that hypoxic changes do not drive indirect release. Secondary endpoint of OS was 35.2 months for the BCBM cohort and 9.5 months for rGBM. Non-planned exploratory endpoint of ORR was 38% for BCBM and 29%, respectively. Exploratory endpoint of Trop-2 expression was observed in 100% of BCBM and 78% of rGBM tumors. In conclusion, SG was found to be well tolerated with adequate penetration into intracranial tumors and promising preliminary activity within the CNS. Trial Registration: Trial (NCT03995706) enrolled at Clinical Trials.gov as Neuro/Sacituzumab Govitecan/Breast Brain Metastasis/Glioblastoma/Ph 0: https://clinicaltrials.gov/study/NCT03995706?cond=NCT03995706 .

Opportunities and Challenges in the Development of Antibody-Drug Conjugate for Triple-Negative Breast Cancer: The Diverse Choices and Changing Needs

Triple-negative breast cancer (TNBC) is a highly heterogeneous breast cancer subtype, which is also characterized by the aggressive phenotype, high recurrence rate, and poor prognosis. Antibody-drug conjugate (ADC) is a monoclonal antibody with a cytotoxic payload connected by a linker. ADC is gaining more and more attention as a targeted anti-cancer agent. Clinical studies of emerging ADC drugs such as sacituzumab govitecan and trastuzumab deruxtecan in patients with metastatic breast cancer (including TNBC) are progressing rapidly. In view of its excellent clinical efficacy and good tolerability, Sacituzumab govitecan gained accelerated approval by the FDA for the treatment of advanced metastatic TNBC in 2020. This review discusses the treatment status and challenges in TNBC, with an emphasis on the current status of ADC development and clinical trials in TNBC and metastatic breast cancer. We also summarize the clinical experience and future exploration directions of ADC development for TNBC patients.

Antibody-Drug Conjugate Sacituzumab Govitecan Enables a Sequential TOP1/PARP Inhibitor Therapy Strategy in Patients with Breast Cancer

PURPOSE

The antibody-drug conjugate (ADC) sacituzumab govitecan (SG) comprises the topoisomerase 1 (TOP1) inhibitor (TOP1i) SN-38, coupled to a monoclonal antibody targeting trophoblast cell surface antigen 2 (TROP-2). Poly(ADP-ribose) polymerase (PARP) inhibition may synergize with TOP1i and SG, but previous studies combining systemic PARP and TOP1 inhibitors failed due to dose-limiting myelosuppression. Here, we assess the proof-of-mechanism and clinical feasibility for SG and talazoparib (TZP) employing an innovative sequential dosing schedule.

PATIENTS AND METHODS

In vitro models tested pharmacodynamic endpoints, and in a phase 1b clinical trial (NCT04039230), 30 patients with metastatic triple-negative breast cancer (mTNBC) received SG and TZP in a concurrent (N = 7) or sequential (N = 23) schedule. Outcome measures included safety, tolerability, preliminary efficacy, and establishment of a recommended phase 2 dose.

RESULTS

We hypothesized that tumor-selective delivery of TOP1i via SG would reduce nontumor toxicity and create a temporal window, enabling sequential dosing of SG and PARP inhibition. In vitro, sequential SG followed by TZP delayed TOP1 cleavage complex clearance, increased DNA damage, and promoted apoptosis. In the clinical trial, sequential SG/TZP successfully met primary objectives and demonstrated median progression-free survival (PFS) of 7.6 months without dose-limiting toxicities (DLT), while concurrent dosing yielded 2.3 months PFS and multiple DLTs including severe myelosuppression.

CONCLUSIONS

While SG dosed concurrently with TZP is not tolerated clinically due to an insufficient therapeutic window, sequential dosing of SG followed by TZP proved a viable strategy. These findings support further clinical development of the combination and suggest that ADC-based therapy may facilitate novel, mechanism-based dosing strategies.

Development of an ELISA with acidification treatment for an antibody conjugate incorporating Exatecans

The successful development of Sacituzumab Govitecan and Trastuzumab Deruxtecan has made camptothecin derivatives one of the most popular payloads for antibody-drug conjugates (ADCs). Camptothecin and its derivatives all exist in a pH-dependent equilibrium between the carboxylate and lactone forms. Such transformation may lead to differences in the ratio of the two molecular forms in calibration standards and biological matrix (bio-matrix) samples, thereby leading to inaccurate conjugated antibody results. In this study, we reported an enzyme-linked immunosorbent assay (ELISA) free of the aforementioned influence for the detection of the Exatecans-conjugated antibody (conjugated SM001) in cynomolgus monkey serum. The assay was developed by first acidifying all samples with glacial acetic acid (HAc), then performing neutralization and thereafter capturing conjugated SM001 with anti-Exatecan monoclonal antibody (mAb) and detecting it with biotinylated Nectin4 (hNectin4-Bio) and horseradish peroxidase-labeled streptavidin (SA-HRP). Results showed that all tested performance parameters met the acceptance criteria. The conjugated SM001 concentrations obtained were in parallel to but slightly lower than total antibody (TAb) throughout the pharmacokinetic (PK) study, revealing that the assay strategy implemented for conjugated SM001 measurement worked well for the elimination of interference triggered by the heterogeneous existence of the lactone and carboxylate forms of Exatecan (lactone-Exatecan and carboxylate-Exatecan).

OptimICE-RD: sacituzumab govitecan + pembrolizumab vs pembrolizumab (± capecitabine) for residual triple-negative breast cancer

Patients with early-stage triple-negative breast cancer (TNBC) with residual invasive disease after neoadjuvant therapy have a high risk of recurrence even with neoadjuvant and adjuvant treatment with pembrolizumab. Sacituzumab govitecan, a Trop-2-directed antibody-drug conjugate with a topoisomerase I inhibitor payload, improved progression-free survival (PFS) and overall survival (OS) versus chemotherapy in patients with pre-treated metastatic TNBC. Moreover, preclinical data suggest that topoisomerase I inhibitors may enhance the effects of immune checkpoint inhibitors through activation of the cGAS-STING pathway. Here we describe the international randomized phase III AFT-65/ASCENT-05/OptimICE-RD trial, which evaluates the efficacy and safety of sacituzumab govitecan plus pembrolizumab versus treatment of physician's choice (pembrolizumab ± capecitabine) among patients with early-stage TNBC with residual invasive disease after neoadjuvant therapy.Clinical Trial Registration: NCT05633654 (ClinicalTrials.gov)Other Study ID Number(s): Gilead Study ID: GS-US-595-6184Registration date: 1 December 2022Study start date: 12 December 2022Recruitment status: Recruiting.

Clinical translation of antibody drug conjugate dosing in solid tumors from preclinical mouse data

Antibody drug conjugates (ADCs) have made impressive strides in the clinic in recent years with 11 Food and Drug Administration approvals, including 6 for the treatment of patients with solid tumors. Despite this success, the development of new agents remains challenging with a high failure rate in the clinic. Here, we show that current approved ADCs for the treatment of patients with solid tumors can all show substantial efficacy in some mouse models when administered at a similar weight-based [milligrams per kilogram (mg/kg)] dosing in mice that is tolerated in the clinic. Mechanistically, equivalent mg/kg dosing results in a similar drug concentration in the tumor and a similar tissue penetration into the tumor due to the unique delivery features of ADCs. Combined with computational approaches, which can account for the complex distribution within the tumor microenvironment, these scaling concepts may aid in the evaluation of new agents and help design therapeutics with maximum clinical efficacy.

Quantifying payloads of antibody‒drug conjugates using a postcolumn infused-internal standard strategy with LC‒MS

BACKGROUND

Antibody‒drug conjugates (ADCs) are innovative biopharmaceutics consisting of a monoclonal antibody, linkers, and cytotoxic payloads. Monitoring circulating payload concentrations has the potential to identify ADC toxicity; however, accurate quantification faces challenges, including low plasma concentrations, severe matrix effects, and the absence of stable isotope-labeled internal standards (SIL-IS) for payloads and their derivatives. Previous studies used structural analogs as internal standards, but different retention times between structural analogs and target analytes may hinder effective matrix correction. Therefore, a more flexible approach is required for precise payload quantification.

RESULTS

We developed an LC‒MS/MS method incorporating a postcolumn-infused internal standard (PCI-IS) strategy for quantifying payloads and their derivatives of trastuzumab emtansine, trastuzumab deruxtecan, and sacituzumab govitecan, including DM1, MCC-DM1, DXd, SN-38, and SN-38G. Structural analogs (maytansine, Lys-MCC-DM1, and exatecan) were selected as PCI-IS candidates, and their accuracy performance was evaluated based on the percentage of samples within 80%-120% quantification accuracy. Compared to the approach without PCI-IS correction, exatecan enhanced the accuracy performance from 30-40%-100% for SN-38 and DXd, while maytansine and Lys-MCC-DM1 showed comparable accuracy for DM1 and MCC-DM1. This validated PCI-IS analytical method showed superior normalization of matrix effect in all analytes compared to the conventional internal standard approach. The clinical application of this approach showed pronounced differences in DXd and SN-38 concentrations before and after PCI-IS correction. Moreover, only DXd concentrations after PCI-IS correction were significantly higher in patients with thrombocytopenia (p = 0.037).

SIGNIFICANCE

This approach effectively addressed the issue of unavailability of SIL-IS for novel ADC payloads and provided more accurate quantification, potentially yielding more robust statistical outcomes for understanding the exposure-toxicity relationship in ADCs. It is anticipated that this PCI-IS strategy may be extrapolated to quantify payloads and derivatives in diverse ADCs, thereby providing invaluable insights into drug toxicity and fortifying patient safety in ADC usage.

Population Pharmacokinetics of Sacituzumab Govitecan in Patients with Metastatic Triple-Negative Breast Cancer and Other Solid Tumors

BACKGROUND AND OBJECTIVE

Sacituzumab govitecan (SG) is an antibody-drug conjugate composed of an antibody with affinity for Trop-2 coupled to SN-38 via hydrolyzable linker. SG is approved for patients with metastatic triple-negative breast cancer (mTNBC) who have received two or more prior chemotherapies (at least one in a metastatic setting) and for patients with pretreated hormone receptor positive (HR+)/human epidermal growth factor receptor 2 negative (HER2-) metastatic breast cancer.

METHODS

In these analyses, the pharmacokinetics of SG, free SN-38, and total antibody (tAB) were characterized using data from 529 patients with mTNBC or other solid tumors across two large clinical trials (NCT01631552; ASCENT, NCT02574455). Three population pharmacokinetic models were constructed using non-linear mixed-effects modeling; clinically relevant covariates were evaluated to assess their impact on exposure. Models for SG and tAB were developed independently whereas free SN-38 was sequentially generated via a first-order release process from SG.

RESULTS

Pharmacokinetics of the three analytes were each described by a two-compartment model with estimated body weight-based scaling exponents for clearance and volume. Typical parameter estimates for clearance and steady-state volume of distribution were 0.133 L/h and 3.68 L for SG and 0.0164 L/h and 4.26 L for tAB, respectively. Mild-to-moderate renal impairment, mild hepatic impairment, age, sex, baseline albumin level, tumor type, UGT1A1 genotype, or Trop-2 expression did not have a clinically relevant impact on exposure for any of the three analytes.

CONCLUSIONS

These analyses support the approved SG dosing regimen of 10 mg/kg as intravenous infusion on days 1 and 8 of 21-day cycles and did not identify a need for dose adjustment based on evaluated covariates or disease characteristics.

Antibody-Drug Conjugates in Triple Negative Breast Cancer

Triple negative breast cancer (TNBC) accounts for 15%-20% of all breast cancer. It is a heterogeneous breast cancer subtype with a poor prognosis. Given these negative features, there is a need for new treatment options beyond conventional chemotherapy in both the early stage and palliative setting. Impressive results have been reported with antibody-drug conjugates (ADCs) that link a cytotoxic payload to a monoclonal antibody, such as sacituzumab govitecan and trastuzumab deruxtecan, in the metastatic stage. The focus of this review is to discuss completed and ongoing trials involving ADCs in TNBC.

Improving Intracellular Delivery of an Antibody-Drug Conjugate Targeting Carcinoembryonic Antigen Increases Efficacy at Clinically Relevant Doses In Vivo

Solid tumor antibody-drug conjugates (ADC) have experienced more clinical success in the last 5 years than the previous 18-year span since the first ADC approval in 2000. While recent advances in protein engineering, linker design, and payload variations have played a role in this success, high expression and readily internalized targets have also been crucial to solid tumor therapy. However, these factors are also paradoxically connected to poor tissue penetration and lower efficacy. Previous work shows that potent ADCs can benefit from slower internalization under subsaturating doses to improve tissue penetration and increase tumor response. In contrast, faster internalization is predicted to increase efficacy under higher, tumor saturating doses. In this work, the intracellular delivery of SN-38 conjugated to an anti-carcinoembryonic antigen (anti-CEA) antibody (Ab) is increased by coadministering a noncompeting (cross-linking) anti-CEA Ab to improve efficacy in a colorectal carcinoma animal model. The SN-38 payload enables broad tumor saturation with clinically-tolerable doses, and under these saturating conditions, using a second CEA receptor cross-linking Ab yields faster internalization, which increases tumor killing efficacy. Our spheroid results show indirect bystander killing can also occur, but the more efficient direct cell killing from targeted intracellular payload release drives a greater tumor response. These results provide a strategy to increase therapeutic effectiveness with improved intracellular delivery under tumor saturating doses with the potential to expand the ADC target repertoire.

Automated high-throughput buffer exchange platform enhances rapid flow analysis of antibody drug conjugates by high resolution mass spectrometry

Antibody drug conjugates (ADCs) are an increasingly important therapeutic class of molecules for the treatment of cancer. Average drug-to-antibody ratio (DAR) and drug-load distribution are critical quality attributes of ADCs with the potential to impact efficacy and toxicity of the molecule and need to be analytically characterized and understood. Several platform methods including hydrophobic interaction chromatography (HIC) and native size-exclusion chromatography-mass spectrometry (nSEC-MS) have been developed for that purpose; however, each presents some limitations. In this work, we assessed a new sample preparation and buffer exchange platform coupled with high-resolution mass spectrometry for characterizing the drug-load and distribution of several cysteine-linked ADCs conjugated with a variety of chemotypes. Several criteria were evaluated during the optimization of the buffer exchange-mass spectrometry system performance and the data generated with the system were compared with results from nSEC-MS and HIC. The results indicated that the platform enables automated and high throughput quantitative DAR characterization for antibody-drug conjugates with high reproducibility and offers several key advantages over existing approaches that are used for chemotype-agnostic ADC characterization.

Sacituzumab govitecan plus platinum-based chemotherapy mediates significant antitumor effects in triple-negative breast, urinary bladder, and small-cell lung carcinomas

Sacituzumab govitecan (SG) is an antibody-drug conjugate composed of an anti-Trop-2-directed antibody conjugated with the topoisomerase I inhibitory drug, SN-38, via a proprietary hydrolysable linker. SG has received United States Food and Drug Administration (FDA) approval to treat metastatic triple-negative breast cancer (TNBC), unresectable locally advanced or metastatic hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative breast cancer, and accelerated approval for metastatic urothelial cancer. We investigated the utility of combining SG with platinum-based chemotherapeutics in TNBC, urinary bladder carcinoma (UBC), and small-cell lung carcinoma (SCLC). SG plus carboplatin or cisplatin produced additive growth-inhibitory effects in vitro that trended towards synergy. Immunoblot analysis of cell lysates suggests perturbation of the cell-cycle and a shift towards pro-apoptotic signaling evidenced by an increased Bax to Bcl-2 ratio and down-regulation of two anti-apoptotic proteins, Mcl-1 and survivin. Significant antitumor effects were observed with SG plus carboplatin in mice bearing TNBC or SCLC tumors compared to all controls (P < 0.0062 and P < 0.0017, respectively) and with SG plus cisplatin in UBC and SCLC tumor-bearing animals (P < 0.0362 and P < 0.0001, respectively). These combinations were well tolerated by the animals. Combining SG with platinum-based chemotherapeutics demonstrates the benefit in these indications and warrants further clinical investigation.

Postmarketing Safety of Sacituzumab Govitecan: A Pharmacovigilance Study Based on the FDA Adverse Event Reporting System

Sacituzumab govitecan is widely used for the treatment of breast cancer and urothelial carcinoma, but available information regarding adverse events (AEs) is limited. We aim to explore the AE induced by sacituzumab govitecan by mining the FDA Adverse Event Reporting System (FAERS) database. The association between sacituzumab govitecan and AEs was evaluated using the information component. A multivariate logistic regression analysis was conducted for all identified signals to explore the risk factors associated with AEs leading to hospitalization. In total, 1,884 reports related to sacituzumab govitecan were retrieved, and 114 AE signals involving 20 systems were identified. The median time for onset of AEs was ~ 6-7 days after initiating treatment with sacituzumab govitecan, with over 80% of AEs occurring within 30 days. Subgroup analysis revealed that 14 signals were reported in men and 110 in women. There were 58 signals reported in patients under 65 following the use of sacituzumab govitecan, 59 signals in patients over 65, and 31 signals were present in both groups. Multivariable analysis showed that being male and the occurrence of colitis, pneumonitis, febrile neutropenia, pyrexia, sepsis, dehydration, and diarrhea were risk factors leading to hospitalization with an area under the curve (AUC) of 0.89. Additionally, sensitivity analysis revealed that this study had good robustness. This is the first retrospective analysis based on FAERS to review the safety of sacituzumab govitecan. The results highlight the need to closely monitor adverse reactions such as neutropenia, diarrhea, colitis, and sepsis when using sacituzumab govitecan.

Development and Validation of an ADA-Tolerant Assay for Quantification of an Exatecan-Based ADC in Monkey Plasma

BACKGROUND

The development of an anti-drug antibody (ADA)-tolerant pharmacokinetic (PK) assay is important when the drug exposure is irrelevant to toxicity in the presence of ADA. We aimed to develop and validate an ADA-tolerant assay for an exatecan-based antibody-drug conjugate (ADC) in monkey plasma.

RESULTS

The assay tolerated 5.00 µg/mL of ADA at 12 µg/mL of ADC. Its accuracy and precision results satisfied the acceptance criteria. Furthermore, the assay was free from hook and matrix effects and exhibited good dilutional linearity. Additionally, the ADC in plasma samples was stable under different storage conditions.

METHOD

An ADA-tolerant ADC assay was configured with an anti-payload antibody for capture, and a drug-target protein combined with a horseradish peroxidase (HRP)-labeled antibody against a drug-target-protein tag for detection. Samples were firstly acidified to dissociate drug and ADA complexes, and to convert the carboxylate form to the lactone form of exatecan molecules; then, the ADAs in the samples were removed with a naked antibody-coated microplate. The treated samples were further incubated with coated anti-payload antibody and captured ADC molecules were quantified by the detection reagent. The developed assay was optimized and validated against regulatory guidelines.

CONCLUSIONS

The assay met both methodological and sample-related ADA tolerance requirements, and was applicable to a nonclinical study in cynomolgus monkeys.

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.

Sacituzumab Govitecan as a Second-Line Treatment in Relapsed/Refractory Metastatic Triple-Negative Breast Cancer Patients: A Systematic Review and Meta-analysis

BACKGROUND

Chemotherapy, the only treatment option for metastatic triple-negative breast cancer (mTNBC), showed decreased survival rates. Trophoblast cell surface antigen-2 (Trop-2) could be a possible target for antibody-drug conjugates (ADCs).

OBJECTIVE

Sacituzumab govitecan (SG), an anti-Trop-2 ADC for pretreating relapsed/refractory mTNBC patients, was studied to know the efficacy and safety profile of the drug in mTNBC.

METHODS

The present review searched MEDLINE (via PubMed), WHO Clinical Trial Registry, Clinical Trials.gov, and Cochrane Central Register of Controlled Trials until December 25, 2022. The studies searched comprised randomized trials and observational studies (retrospective [case-control, cross-sectional] and prospective [cohort designs]). Efficacy assessment was performed in terms of complete response (CR), partial response (PR), objective response rate (ORR), stable disease (SD), progressive disease (PD), and clinical benefit rate (CBR), and safety in terms of adverse events.

RESULTS

The overall random-effects pooled prevalence of CR was 4.9 (95% CI: 3.2-7.1), PR was 35.6 (95% CI: 31.5-39.9), ORR was 6.8 (95% CI: 5.9-7.8), SD was 8.0 (95% CI: 6.7-9.4), PD was 5.1 (95% CI: 4.1-6.3), and CBR was 13.4 (95% CI: 11.8-15.1). Adverse events associated with the drug were neutropenia, fatigue, anemia, nausea, and others.

CONCLUSION AND RELEVANCE

This is the first meta-analysis conducted in relapsed/refractory mTNBC patients and found that SG is efficacious but associated with some adverse effects that are related to exposure to the drug. The application of these results will allow clinicians to use SG in the management of patients with mTNBC.

TROP2-directed nanobody-drug conjugate elicited potent antitumor effect in pancreatic cancer

BACKGROUND

Pancreatic cancer is a highly aggressive malignancy with limited treatment options and a poor prognosis. Trophoblast cell surface antigen 2 (TROP2), a cell surface antigen overexpressed in the tumors of more than half of pancreatic cancer patients, has been identified as a potential target for antibody-drug conjugates (ADCs). Almost all reported TROP2-targeted ADCs are of the IgG type and have been poorly studied in pancreatic cancer. Here, we aimed to develop a novel nanobody-drug conjugate (NDC) targeting TROP2 for the treatment of pancreatic cancer.

RESULTS

In this study, we developed a novel TROP2-targeted NDC, HuNbTROP2-HSA-MMAE, for the treatment of TROP2-positive pancreatic cancer. HuNbTROP2-HSA-MMAE is characterized by the use of nanobodies against TROP2 and human serum albumin (HSA) and has a drug-antibody ratio of 1. HuNbTROP2-HSA-MMAE exhibited specific binding to TROP2 and was internalized into tumor cells with high endocytosis efficiency within 5 h, followed by intracellular translocation to lysosomes and release of MMAE to induce cell apoptosis in TROP2-positive pancreatic cancer cells through the caspase-3/9 pathway. In a xenograft model of pancreatic cancer, doses of 0.2 mg/kg and 1 mg/kg HuNbTROP2-HSA-MMAE demonstrated significant antitumor effects, and a dose of 5 mg/kg even eradicated the tumor.

CONCLUSION

HuNbTROP2-HSA-MMAE has desirable affinity, internalization efficiency and antitumor activity. It holds significant promise as a potential therapeutic option for the treatment of TROP2-positive pancreatic cancer.

Understanding the promising role of antibody drug conjugates in breast and ovarian cancer

A nascent category of anticancer therapeutic drugs called antibody-drug conjugates (ADCs) relate selectivity of aimed therapy using chemotherapeutic medicines with high cytotoxic power. Progressive linker technology led to the advancement of more efficacious and safer treatments. It offers neoteric as well as encouraging therapeutic strategies for treating cancer. ADCs selectively administer a medication by targeting antigens which are abundantly articulated on the membrane surface of tumor cells. Tumor-specific antigens are differently expressed in breast and ovarian cancers and can be utilized to direct ADCs. Compared to conventional chemotherapeutic drugs, this approach enables optimal tumor targeting while minimizing systemic damage. A cleavable linker improves the ADCs because it allows the toxic payload to be distributed to nearby cells that do not express the target protein, operating on assorted tumors with dissimilar cell aggregation. Presently fifteen ADCs are being studied in breast and ovarian carcinoma preclinically, and assortment of few have already undergone promising early-phase clinical trial testing. Furthermore, Phase I and II studies are investigating a wide variety of ADCs, and preliminary findings are encouraging. An expanding sum of ADCs will probably become feasible therapeutic choices as solo agents or in conjunction with chemotherapeutic agents. This review accentuates the most recent preclinical findings, pharmacodynamics, and upcoming applications of ADCs in breast and ovarian carcinoma.

Antibody-drug conjugates for urothelial carcinoma

The standard of care for advanced urothelial carcinoma includes platinum chemotherapy and immunotherapy. Antibody-drug conjugates (ADCs), originally developed for hematologic malignancies, involve potent cytotoxic agents linked to antibodies that recognize tumor-specific antigens; this rational drug design allows for more on-target efficacy, while mitigating systemic toxicity. Herein, we review the emerging landscape of ADCs in urothelial carcinoma. The anti-Nectin-4 ADC enfortumab vedotin has demonstrated efficacy in prospective studies in patients with advanced urothelial carcinoma in several settings either alone or in combination with pembrolizumab. The anti-Trop-2 ADC sacituzumab govitecan has also shown efficacy in single-armed studies. Both conjugates have full or accelerated approval from the Food and Drug Administration. Common adverse events include rash and neuropathy for enfortumab vedotin and myelosuppression and diarrhea for sacituzumab govitecan. Several anti-human epidermal growth factor receptor 2 ADCs are in clinical trials, and in localized bladder cancer, the anti-epithelial cell adhesion molecule ADC oportuzumab monatox is being studied in patients refractory to intravesical bacillus calmette-guerin therapy. Antibody-drug conjugates for urothelial carcinoma are approved and emerging as therapies for patients with advanced urothelial carcinoma, filling a prior void for treatment of progressive disease. Ongoing studies are also evaluating these agents in the neoadjuvant and adjuvant settings.

Next-generation antibody-drug conjugates for breast cancer: Moving beyond HER2 and TROP2

Antibody-drug conjugates (ADCs) have reshaped the treatment of several malignancies, including breast cancer. Two ADCs are currently approved for the treatment of each breast cancer subtype, including the HER2 targeted ADCs trastuzumab emtansine (T-DM1) and trastuzumab deruxtecan (T-DXd), and the TROP2-targeted ADC sacituzumab govitecan. Each of the ADC components (antibody, linker, and payload) plays a key role in determining the efficacy and toxicity profile of an individual ADC, and their modification can lead to major changes in the clinical profile of these agents. Leveraging the knowledge from three decades of development in the field, several novel ADCs are currently being investigated. Some approaches include targeting different antigens beyond the established HER2/TROP2, or evaluating innovative constructs, such as bispecific ADCs, ADCs with dual payload, immune-modulating ADCs, radionuclide drug conjugates, and masked ADCs, among others. In this review article we discuss the evolving landscape of novel ADCs, highlighting opportunities and challenges emerging in the field.

A new era in the treatment of urothelial carcinoma

The advances in targeted therapies, immunotherapy, and the recent emergence of antibody-drug conjugates (ADCs) herald a potential paradigm shift in treating patients with metastatic urothelial cancer. Yet, there are inherent challenges in utilizing these therapies, including the management of treatment-related toxicities. In this special Urologic Oncology: Seminars and Original Investigations issue, we review the latest developments and discuss insights into future research needs.

Mutual ATRaction: Assessing Synergy of Berzosertib with Sacituzumab Govitecan

A phase I trial of the novel combination of the ataxia telangiectasia and Rad3-related inhibitor berzosertib plus the antibody-drug conjugate sacituzumab govitecan in patients with heavily pretreatment tumors demonstrated some antitumor activity and no dose-limiting toxicities. This represents a new treatment paradigm that will be further explored in a phase II setting. See related article by Abel et al., p. 3603.

Antibody-drug conjugates (ADCs) targeting TROP-2 in lung cancer

INTRODUCTION

The advent of antibody-drug conjugates (ADCs) represents a renewed strategy in the era of precision oncology. Several epithelial tumors harbor overexpression of the trophoblast cell-surface antigen 2 (TROP-2), which represents a predictor of poor prognosis and a promising target for anticancer therapy.

AREAS COVERED

In this review, we aim to collect the available preclinical and clinical data regarding anti-TROP-2 ADCs in lung cancer obtained through extensive literature research and screening of the available abstract/posters presented at recent meetings.

EXPERT OPINION

Anti-TROP-2 ADCs represent an innovative upcoming weapon against both non-small cell lung cancer and small cell lung cancer subtypes, pending the results of several ongoing trials. The proper combination and placement of this agent throughout the lung cancer treatment pathway, the identification of potentially predictive biomarkers of benefit, as well as the optimal management and impact of peculiar toxicity (i.e. interstitial lung disease) are the next questions to be answered.

Targeting Trop-2 in cancer: Recent research progress and clinical application

The development of new antitumor drugs depends mainly upon targeting tumor cells precisely. Trophoblast surface antigen 2 (Trop-2) is a type I transmembrane glycoprotein involved in Ca2+ signaling in tumor cells. It is highly expressed in various tumor tissues than in normal tissues and represents a novel and promising molecular target for caner targeted therapy. Up to now, the mechanisms and functions associated with Trop-2 have been extensively studied in a variety of solid tumors. According to these findings, Trop-2 plays an important role in cell proliferation, apoptosis, cell adhesion, epithelial-mesenchymal transition, as well as tumorigenesis and tumor progression. In addition, Trop-2 related drugs are also being developed widely. There are a number of Trop-2 related ADC drugs that have demonstrated potent antitumor activity and are currently been studied, such as Sacituzumab Govitecan (SG) and Datopotamab Deruxtecan (Dato-Dxd). In this study, we reviewed the progress of Trop-2 research in solid tumors. We also sorted out the composition and rationale of Trop-2 related drugs and summarized the related clinical trials. Finally, we discussed the current status of Trop-2 research and expanded our perspectives on its future research directions. Importantly, we found that Trop-2 targeted ADCs have great potential for combination with other antitumor therapies. Trop-2 targeted ADCs can reprogramme tumor microenvironment through multiple signaling pathways, ultimately activating antitumor immunity.

Advances in Targeted Therapy of Breast Cancer with Antibody-Drug Conjugate

Antibody-drug conjugates (ADCs) are a potential and promising therapy for a wide variety of cancers, including breast cancer. ADC-based drugs represent a rapidly growing field of breast cancer therapy. Various ADC drug therapies have progressed over the past decade and have generated diverse opportunities for designing of state-of-the-art ADCs. Clinical progress with ADCs for the targeted therapy of breast cancer have shown promise. Off-target toxicities and drug resistance to ADC-based therapy have hampered effective therapy development due to the intracellular mechanism of action and limited antigen expression on breast tumors. However, innovative non-internalizing ADCs targeting the tumor microenvironment (TME) component and extracellular payload delivery mechanisms have led to reduced drug resistance and enhanced ADC effectiveness. Novel ADC drugs may deliver potent cytotoxic agents to breast tumor cells with reduced off-target effects, which may overcome difficulties related to delivery efficiency and enhance the therapeutic efficacy of cytotoxic cancer drugs for breast cancer therapy. This review discusses the development of ADC-based targeted breast cancer therapy and the clinical translation of ADC drugs for breast cancer treatment.

Overview of Trop-2 in Cancer: From Pre-Clinical Studies to Future Directions in Clinical Settings

Trophoblast cell surface antigen-2 (Trop-2) is a glycoprotein that was first described as a membrane marker of trophoblast cells and was associated with regenerative abilities. Trop-2 overexpression was also described in several tumour types. Nevertheless, the therapeutic potential of Trop-2 was widely recognized and clinical studies with drug–antibody conjugates have been initiated in various cancer types. Recently, these efforts have been rewarded with the approval of sacituzumab govitecan from both the Food and Drug Administration (FDA) and European Medicines Agency (EMA), for metastatic triple-negative breast cancer patients. In our work, we briefly summarize the various characteristics of cancer cells overexpressing Trop-2, the pre-clinical activities of specific inhibitors, and the role of anti-Trop-2 therapy in current clinical practice. We also review the ongoing clinical trials to provide a snapshot of the future developments of these therapies.

Antibody-Drug Conjugate Sacituzumab Govitecan Drives Efficient Tissue Penetration and Rapid Intracellular Drug Release

Antibody-drug conjugates (ADC) are a rapidly growing class of targeted cancer treatments, but the field has experienced significant challenges from their complex design. This study examined the multiscale distribution of sacituzumab govitecan (SG; Trodelvy), a recently clinically approved ADC, to clarify the mechanism(s) of efficacy given its unique design strategy. We employed a multiscale quantitative pharmacokinetic approach, including near-infrared fluorescence imaging, single-cell flow cytometry measurements, payload distribution via γH2AX pharmacodynamic staining, and a novel dual-labeled fluorescent technique to track the ADC and payload in a high trophoblast cell-surface antigen 2 expression xenograft model of gastric cancer (NCI-N87). We found that rapid release of the SN-38 payload from the hydrolysable linker inside cells imparts more DNA damage in vitro and in vivo than an ADC with a more stable enzyme cleavable linker. With SG, little to no extracellular payload release in the tumor was observed using a dual-labeled fluorescence technique, although bystander effects were detected. The high dosing regimen allowed the clinical dose to reach the majority of cancer cells, which has been linked to improved efficacy. In addition, the impact of multiple doses (day 1 and day 8) of a 21-day cycle was found to further improve tissue penetration despite not changing tumor uptake [percent injected dose per gram (%ID/g)] of the ADC. These results show increased ADC efficacy with SG can be attributed to efficient tumor penetration and intracellular linker cleavage after ADC internalization. This quantitative approach to study multiscale delivery can be used to inform the design of next-generation ADCs and prodrugs for other targets.

Preclinical profiles of SKB264, a novel anti-TROP2 antibody conjugated to topoisomerase inhibitor, demonstrated promising antitumor efficacy compared to IMMU-132

Purpose

The aim of this study was to improve the intratumoral accumulation of an antibody-drug conjugate (ADC) and minimize its off-target toxicity, SKB264, a novel anti-trophoblast antigen 2 (TROP2) ADC that was developed using 2-methylsulfonyl pyrimidine as the linker to conjugate its payload (KL610023), a belotecan-derivative topoisomerase I inhibitor. The preclinical pharmacologic profiles of SKB264 were assessed in this study.

Methods

The in vitro and in vivo pharmacologic profiles of SKB264, including efficacy, pharmacokinetics-pharmacodynamics (PK-PD), safety, and tissue distribution, were investigated using TROP2-positive cell lines, cell-derived xenograft (CDX), patient-derived xenograft (PDX) models, and cynomolgus monkeys. Moreover, some profiles were compared with IMMU-132.

Results

In vitro, SKB264 and SKB264 monoclonal antibody (mAb) had similar internalization abilities and binding affinities to TROP2. After cellular internalization, KL610023 was released and inhibited tumor cell survival. In vivo, SKB264 significantly inhibited tumor growth in a dose-dependent manner in both CDX and PDX models. After SKB264 administration, the serum or plasma concentration/exposure of SKB264 (conjugated ADC, number of payload units ≥1), total antibody (Tab, unconjugated and conjugated mAb regardless of the number of the payload units), and KL610023 in cynomolgus monkeys increased proportionally with increasing dosage from 1 to 10 mg/kg. The linker stability of SKB264 was significantly enhanced as shown by prolonged payload half-life in vivo (SKB264 vs. IMMU-132, 56.3 h vs. 15.5 h). At the same dose, SKB264's exposure in tumor tissue was 4.6-fold higher than that of IMMU-132.

Conclusions

Compared with IMMU-132, the longer half-life of SKB264 had a stronger targeting effect and better antitumor activity, suggesting the better therapeutic potential of SKB264 for treating TROP2-positive tumors.

'Why is survival with triple negative breast cancer so low? insights and talking points from preclinical and clinical research'

INTRODUCTION

Triple negative breast cancer is typically related to poor prognosis, early metastasis, and high recurrence rate. Intrinsic and extrinsic biological features of TNBC and resistance mechanisms to conventional therapies can support its aggressive behavior, characterizing TNBC how extremely heterogeneous. Novel combination strategies are under investigation, including immunotherapeutic agents, anti-drug conjugates, PARP inhibitors, and various targeting agents, exploring, in the meanwhile, possible predictive biomarkers to correctly select patients for the optimal treatment for their specific subtype.

AREAS COVERED

This article examines the main malignity characteristics across different subtype, both histological and molecular, and the resistance mechanisms, both primary and acquired, to different drugs explored in the landscape of TNBC treatment, that lead TNBC to still has high mortality rate.

EXPERT OPINION

The complexity of TNBC is not only the main reason of its aggressivity, but its heterogeneity should be exploited in terms of therapeutics opportunities, combining agents with different mechanism of action, after a correct selection by biologic or molecular biomarkers. The main goal is to understand what TNBC really is and to act selectively on its characteristics, with a personalized anticancer treatment.

Trop-2 as a Therapeutic Target in Breast Cancer

The emergence of Trop-2 as a therapeutic target has given rise to new treatment paradigms for the treatment of patients with advanced and metastatic breast cancer. Trop-2 is most highly expressed in triple negative breast cancer (TNBC), but the receptor is found across all breast cancer subtypes. With sacituzumab govitecan, the first FDA-approved, Trop-2 inhibitor, providing a survival benefit in patients with both metastatic TNBC and hormone receptor positive breast cancer, additional Trop-2 directed therapies are under investigation. Ongoing studies of combination regimens with immunotherapy, PARP inhibitors, and other targeted agents aim to further harness the effect of Trop-2 inhibition. Current investigations are also underway in the neoadjuvant and adjuvant setting to evaluate the therapeutic benefit of Trop-2 inhibition in patients with early stage disease. This review highlights the significant impact the discovery Trop-2 has had on our patients with heavily pretreated breast cancer, for whom few treatment options exist, and the future direction of novel Trop-2 targeted therapies.

Antibody-drug conjugates targeting Trop-2: Clinical developments in early breast cancer therapy

Although breast cancer has a good prognosis compared with various cancers, metastatic breast cancer has an aggressive disease course and remains incurable. Therefore, treatment of early breast cancer to prevent recurrence and metastasis is crucial. Recently, the development of anti-cancer drugs, such as targeted agents and immuno-oncology, has been accelerating. Antibody-drug conjugates (ADCs) are also building a new paradigm. Particularly, ADCs targeting Trop-2 were approved for their efficacy in metastatic triple-negative breast cancer patients who received ≥2 prior systemic therapies and showed significant results in heavily pretreated hormone receptor-positive/HER2-negative breast cancer. In this brief review, we provide an overview of ongoing clinical trials of ADCs targeting Trop-2 in early breast cancer, specifically sacituzumab govitecan.

Sacituzumab govitecan: past, present and future of a new antibody-drug conjugate and future horizon

Sacituzumab govitecan (SG) is a new antibody-drug conjugate directed against the cell-surface antigen Trop-2. Characteristics of the linker connecting the payload SN-38 to the antibody allows SG to kill tumor cells expressing Trop-2 and also the adjacent tumor cells (bystander effect). SG showed efficacy and safety in several epithelial tumors. The phase III ASCENT trial led to the approval of SG (10 mg/kg, d1,8 q3w) in patients with advanced or metastatic triple-negative breast cancer (TNBC) who have received ≥2 prior systemic therapies, including ≥1 for metastatic disease. The phase III TROPiCS-02 trial in heavily pretreated advanced hormone receptor (HR)-positive breast cancer has recently shown an improvement in progression-free survival for patients treated with SG compared to single-agent chemotherapy. The phase III post-neoadjuvant SASCIA study in early high-risk TNBC and HR-positive breast cancer is currently recruiting patients.

Carbon dots conjugated to SN38 for improved colorectal anticancer therapy

Irinotecan (CTP-11) is one of the standard therapies for colorectal cancer (CRC). CTP-11 is enzymatically converted to the hydrophobic 7-ethyl-10-hydroxycamptothecin (SN38), a one hundred-fold more active metabolite. Conjugation of hydrophobic anticancer drugs to nanomaterials is a strategy to improve their solubility, efficacy, and selectivity. Carbon dots (CDs) have garnered interest for their small sizes (<10 ​nm), low toxicity, high water solubility, and bright fluorescence. This paper describes the use of CDs to improve drug vehiculation, stability, and chemotherapeutic efficiency of SN38 through a direct intracellular uptake in CRC. The covalent conjugation of SN38 to CDs via a carbamate bond provides a CD-SN38 hybrid material for slow, sustained, and pH-responsive drug release. CD-SN38 successfully penetrates the CRC cells with a release in the nucleus affecting first the cell cycle and then the cytoskeleton. Moreover, CD-SN38 leads to a deregulation of the extracellular matrix (ECM), one of the major components of the cancer niche considered a possible target therapy for reducing the cancer progression. This work shows the combined therapeutic and imaging potential of CD-based hybrid materials for the treatment of CRC. Future efforts for targeted therapy of chronic diseases characterized by altered ECM deposition, such as chronic kidney disease and chronic allograft nephropathy in kidney transplant patients are envisaged.

Recent advances in therapeutic strategies for triple-negative breast cancer

Triple-negative breast cancer (TNBC) is the most malignant subtype of breast cancer (BC) with a poor prognosis. Current treatment options are limited to surgery, adjuvant chemotherapy and radiotherapy; however, a proportion of patients have missed the surgical window at the time of diagnosis. TNBC is a highly heterogeneous cancer with specific mutations and aberrant activation of signaling pathways. Hence, targeted therapies, such as those targeting DNA repair pathways, androgen receptor signaling pathways, and kinases, represent promising treatment options against TNBC. In addition, immunotherapy has also been demonstrated to improve overall survival and response in TNBC. In this review, we summarize recent key advances in therapeutic strategies based on molecular subtypes in TNBC.

Triple negative breast cancer: approved treatment options and their mechanisms of action

PURPOSE

Breast cancer, the most prevalent cancer worldwide, consists of 4 main subtypes, namely, Luminal A, Luminal B, HER2-positive, and Triple-negative breast cancer (TNBC). Triple-negative breast tumors, which do not express estrogen, progesterone, and HER2 receptors, account for approximately 15-20% of breast cancer cases. The lack of traditional receptor targets contributes to the heterogenous, aggressive, and refractory nature of these tumors, resulting in limited therapeutic strategies.

METHODS

Chemotherapeutics such as taxanes and anthracyclines have been the traditional go to treatment regimens for TNBC patients. Paclitaxel, docetaxel, doxorubicin, and epirubicin have been longstanding, Food and Drug Administration (FDA)-approved therapies against TNBC. Additionally, the FDA approved PARP inhibitors such as olaparib and atezolizumab to be used in combination with chemotherapies, primarily to improve their efficiency and reduce adverse patient outcomes. The immunotherapeutic Keytruda was the latest addition to the FDA-approved list of drugs used to treat TNBC.

RESULTS

The following review aims to elucidate current FDA-approved therapeutics and their mechanisms of action, shedding a light on the various strategies currently used to circumvent the treatment-resistant nature of TNBC cases.

CONCLUSION

The recent approval and use of therapies such as Trodelvy, olaparib and Keytruda has its roots in the development of an understanding of signaling pathways that drive tumour growth. In the future, the emergence of novel drug delivery methods may help increase the efficiency of these therapies whiel also reducing adverse side effects.

Sacituzumab Govitecan-hziy in Breast Cancer

Trophoblast cell-surface antigen-2 (Trop-2) is a transmembrane calcium signal transducer and its overexpression is common in many types of malignant epithelial tumors, including breast cancer (BC). Sacituzumab govitecan-hziy (SG), the anti-Trop-2 antibody-drug conjugate, resulted in a significant survival benefit over chemotherapy in patients with metastatic triple-negative breast cancer (mTNBC). The greatest efficacy was observed in those who had a medium or high Trop-2 score. However, the importance of Trop-2 as a potential predictive factor requires further research. Elderly patients also appear to benefit from treating with SG. While the early results are encouraging, the ultimate benefit of SG in patients with brain metastases has yet to be determined. Early phase studies have shown that SG is also active in hormone receptor-positive/human epidermal growth factor receptor 2-negative (HR+/HER2-) metastatic BC. The most common side effects of SG are nausea, neutropenia and diarrhea. Currently, several clinical trials are in progress with SG in monotherapy and in combination treatment for various types of BC. Taken together, SG should be considered as a new standard of care in patients with pretreated mTNBC. This review summarizes the development and highlights recent advances of the SG in BC.

Folate Decorated Multifunctional Biodegradable Nanoparticles for Gastric Carcinoma Active Targeting Theranostics

Introduction

Gastric cancer remains a major clinical issue and little progress has been made in the treatment of gastric cancer patients during recent decades. Nanoparticles provide a versatile platform for the diagnosis and treatment of gastric cancer.

Methods

We prepared 7-ethyl-10-hydroxycamptothecin (SN-38) ¹²⁵I-radiolabelled biodegradable nanoparticles with folate surface modification (¹²⁵I-SN-38-FA-NPs) as a novel nanoplatform for targeted gastric carcinoma theranostics. We characterized this system in terms of particle size, morphology, radiostability, and release properties and examined the in vitro cytotoxicity and cellular uptake properties of ¹²⁵I-SN-38-FA-NPs in MNK 7 and NCI-N7 cells. The pharmacokinetics and biodistribution of ¹²⁵I-SN-38-FA-NPs were imaged by single photon emission computer tomography (SPECT). An MNK7 tumor-bearing model were established and the in vivo antitumor activity of ¹²⁵I-SN-38-FA-NPs was evaluated.

Results

SN-38 was readily radiolabeled with ¹²⁵I and exhibited high radiostability. Poly-lactic-co-glycolic acid (PLGA) nanoparticles (NPs) were formed by solvent exchange, and displayed spherical morphology of 100 nm in diameter as characterized by dynamic light scattering (DLS) and transmission electron microscopy (TEM). A 2.5-fold greater uptake of ¹²⁵I-radiolabelled SN-38-loaded folate-decorated PLGA nanoparticles (¹²⁵I-SN-38-FA-NPs) than ¹²⁵I-radiolabelled SN-38-loaded PLGA nanoparticles (¹²⁵I-SN-38-NPs) were record in MKN7 tumor cells. NPs and folate-decorated PLGA nanoparticles (FA-NPs) also had good biocompatibility in methyl thiazolyl tetrazolium (MTT) assays. Pharmacokinetic, biodistribution and SPECT imaging studies showed that ¹²⁵I-SN-38-FA-NPs had prolonged circulation, were distributed in the reticuloendothelial system, and had high uptake in tumors with a higher tumor accumulation of ¹²⁵I-SN-38-FA-NPs than ¹²⁵I-SN-38-NPs recorded at 24 h postinjection. In vivo SN-38-FA-NPs significantly inhibited tumor growth without causing obvious side effects.

Conclusion

Folate receptor alpha (FOLR1) targeted drug-loaded nanoparticles enable SPECT imaging and chemotherapy, and provide a novel nanoplatform for gastric carcinoma active targeting theranostics.

Signaling Pathways and Natural Compounds in Triple-Negative Breast Cancer Cell Line

Triple-negative breast cancer (TNBC) is the most aggressive subtype of breast cancer, having a poor prognosis and rapid metastases. TNBC is characterized by the absence of estrogen, progesterone, and human epidermal growth receptor-2 (HER2) expressions and has a five-year survival rate. Compared to other breast cancer subtypes, TNBC patients only respond to conventional chemotherapies, and even then, with limited success. Shortages of chemotherapeutic medication can lead to resistance, pressured index therapy, non-selectivity, and severe adverse effects. Finding targeted treatments for TNBC is difficult owing to the various features of cancer. Hence, identifying the most effective molecular targets in TNBC pathogenesis is essential for predicting response to targeted therapies and preventing TNBC cell metastases. Nowadays, natural compounds have gained attention as TNBC treatments, and have offered new strategies for solving drug resistance. Here, we report a systematic review using the database from Pubmed, Science Direct, MDPI, BioScince, Springer, and Nature for articles screening from 2003 to 2022. This review analyzes relevant signaling pathways and the prospect of utilizing natural compounds as a therapeutic agent to improve TNBC treatments in the future.

The European Medicines Agency review of sacituzumab govitecan for the treatment of triple-negative breast cancer

Sacituzumab govitecan (SG) is an antineoplastic agent which combines a humanized monoclonal antibody binding to trophoblast cell surface antigen-2 (Trop-2)-expressing cancer cells, linked with cytotoxic moiety SN-38 (govitecan) with topoisomerase I inhibitor action. On 22 November 2021, a marketing authorization valid through the European Union (EU) was issued under the European Medicines Agency (EMA)’s accelerated assessment program for SG as monotherapy for the treatment of adult patients with unresectable or metastatic triple-negative breast cancer (mTNBC) who have received two or more prior systemic therapies, including at least one of them for advanced disease. The assessment was based on results from an open-label, randomized, phase III trial to evaluate the safety, tolerability, pharmacokinetics and efficacy of SG versus treatment of physician’s choice (TPC) in patients with mTNBC who received at least two prior treatments including at least one of them for advanced disease. The efficacy results in the overall population, based on mature data, showed a statistically significant improvement of SG over TPC in progression-free survival (PFS) and overall survival (OS). The median PFS was 4.8 months versus 1.7 months [hazard ratio (HR) = 0.43, n = 529; 95% CI 0.35-0.54; P < 0.0001] and the median OS was 11.8 months versus 6.9 months (HR = 0.51, n = 529; 95% CI 0.41-0.62; P < 0.0001). The most common (>30%) side effects of SG were diarrhea, neutropenia, nausea, fatigue, alopecia, anemia, constipation and vomiting. The aim of this manuscript is to summarize the scientific review of the application leading to regulatory approval in the EU.

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Trodelvy (SG) received a marketing authorization valid throughout the EU on 22 November 2021.

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SG is indicated for adults with unresectable or metastatic TBNC.

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SG is an antibody–drug conjugate considered a first-in-class medicine.

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SG prolonged OS and PFS ∼5 and 3 months, respectively, when compared to TPC.

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The most common serious side effects are febrile neutropenia and diarrhea.

Research Progress of Antibody–Drug Conjugate Therapy for Advanced Gastric Cancer

Gastric cancer is an intractable malignant tumor that has the fifth highest morbidity and the third highest mortality in the world. Even though various treatment options did much to ameliorate the prognosis of advanced gastric cancer, the survival time remained unsatisfactory. It is significant to develop new therapeutic agents to improve the long-term outcome. Antibody–drug conjugate is an innovative and potent antineoplastic drug composed of a specifically targeted monoclonal antibody, a chemical linker, and a small molecule cytotoxic payload. Powerful therapeutic efficacy and moderate toxicity are its preponderant advantages, which imply the inevitable pharmaceutical developments to meet the demand for individualized precision therapy. Nevertheless, it is unavoidable that there is a phenomenon of drug resistance in this agent. This article systematically reviewed the recent progress of antibody–drug conjugates in advanced gastric cancer therapy.

Current and emerging role of sacituzumab govitecan in the management of urothelial carcinoma

INTRODUCTION

Despite rapid advances in the treatment landscape of urothelial cancer, there is a substantial unmet need for safe and effective therapies for patients with locally advanced and metastatic urothelial cancer. Sacituzumab govitecan (SG) is an antibody-drug conjugate, consisting of a Trop-2 directed monoclonal antibody linked to SN-38, the active metabolite of irinotecan. Trop-2 is a glycoprotein overexpressed in various carcinomas, including urothelial carcinomas.

AREAS COVERED

We review the available data on SG, including mechanism of action, pharmacology, efficacy, safety, and clinical studies regarding locally advanced or metastatic urothelial cancer.

EXPERT OPINION

SG performed well in the TROPHY-U-01 phase II trial with an objective response rate of 27%. The most common adverse effects were diarrhea, nausea, fatigue, alopecia, and neutropenia, with the most common grade ≥ 3 treatment-related AEs being neutropenia, leukopenia, anemia, diarrhea, and febrile neutropenia. However, these effects were managed effectively with supportive care. SG currently has an accelerated approval for patients with locally advanced or metastatic urothelial cancer who have received platinum-based chemotherapy and either programmed cell death receptor-1 (PD-1) or programmed death-ligand 1 (PD-L1) inhibitor. Several studies are evaluating SG in urothelial cancers as single-agent or in combination with other agents.

Antibody-drug conjugates: Smart chemotherapy delivery across tumor histologies

As distinct cancer biomarkers have been discovered in recent years, a need to reclassify tumors by more than their histology has been proposed, and therapies are now tailored to treat cancers based on specific molecular aberrations and immunologic markers. In fact, multiple histology-agnostic therapies are currently adopted in clinical practice for treating patients regardless of their tumor site of origin. In parallel with this new model for drug development, in the past few years, several novel antibody-drug conjugates (ADCs) have been approved to treat solid tumors, benefiting from engineering improvements in the conjugation process and the introduction of novel linkers and payloads. With the recognition that numerous surface targets are expressed across various cancer histologies, alongside the remarkable activity of modern ADCs, this drug class has been increasingly evaluated as suitable for a histology-agnostic expansion of indication. For illustration, the anti-HER2 ADC trastuzumab deruxtecan has demonstrated compelling activity in HER2-overexpressing breast, gastric, colorectal, and lung cancer. Examples of additional novel and potentially histology-agnostic ADC targets include trophoblast cell-surface antigen 2 (Trop-2) and nectin-4, among others. In the current review article, the authors summarize the current approvals of ADCs by the US Food and Drug Administration focusing on solid tumors and discuss the challenges and opportunities posed by the multihistological expansion of ADCs.

New antibody-drug conjugates (ADCs) in breast cancer—an overview of ADCs recently approved and in later stages of development

Antibody-drug conjugates (ADCs) have changed the treatment of breast cancer (BC) in more recent years. BC is a heterogenous group of malignancies with a broad range of histopathological characteristics. ADCs represent a class of therapeutics that combines an antigen-specific antibody backbone bound to a potent cytotoxic agent (the payload), via a linker, contributing to an improved therapeutic index. Currently, three ADCs received approval by the US Food and Drug Administration (FDA) and are in routine clinical use in different treatment settings; many more ADCs are in earlier and later stages of development, and their future approval will improve treatment options for patients with advanced but potentially also early-stage BC over time. Just recently, the results of three phase 3 trials (ASCENT, TULIP, and DESTINY-Breast03) evaluating sacituzumab govitecan (SG), trastuzumab duocarmazine, and trastuzumab deruxtecan (T-DXd) in different treatment settings were presented and showed promising results. This overview focuses on the newer ADCs, including T-DXd and SG, their pharmacology, mechanisms of action, and relevant studies. In addition, the latest results from trials investigating some newer ADCs, in further stages of development are presented.

Antibody-Drug Conjugate Targets, Drugs and Linkers

Antibody-drug conjugates offer the possibility of directing powerful cytotoxic agents to a malignant tumor while sparing normal tissue. The challenge is to select an antibody target expressed exclusively or at highly elevated levels on the surface of tumor cells and either not all or at low levels on normal cells. The current review explores 78 targets that have been explored as antibody-drug conjugate targets. Some of these targets have been abandoned, 9 or more are the targets of FDA-approved drugs, and most remain active clinical interest. Antibody-drug conjugates require potent cytotoxic drug payloads, several of these small molecules are discussed, as are the linkers between the protein component and small molecule components of the conjugates. Finally, conclusions regarding the elements for the successful antibody-drug conjugate are discussed.

A New Kid on the Block: Sacituzumab Govitecan for the Treatment of Breast Cancer and Other Solid Tumors

Human trophoblast cell-surface antigen-2 (Trop-2) is a membrane glycoprotein involved in cell proliferation and motility, frequently overexpressed in epithelial tumors. Thus, it represents an attractive target for anticancer therapies. Sacituzumab govitecan (SG) is a third-generation antibody-drug conjugate, consisting of an anti-Trop-2 monoclonal antibody (hRS7), a hydrolyzable linker, and a cytotoxin (SN38), which inhibits topoisomerase 1. Specific pharmacological features, such as the high antibody to payload ratio, the ultra-toxic nature of SN38, and the capacity to kill surrounding tumor cells (the bystander effect), make SG a very promising drug for cancer treatment. Indeed, unprecedented results have been observed with SG in patients with heavily pretreated advanced triple-negative breast cancer and urothelial carcinomas, and the drug has already received approval for these indications. These results are coupled with a manageable toxicity profile, with neutropenia and diarrhea as the most frequent adverse events, mainly of grades 1-2. While several trials are exploring SG activity in different tumor types and settings, potential biomarkers of response are under investigation. Among these, Trop-2 overexpression and the presence of BRCA1/2 mutations seem to be the most promising. We review the available literature concerning SG, with a focus on its toxicity spectrum and possible biomarkers of its response.

Antibody-drug conjugates: Recent advances in linker chemistry

Antibody–drug conjugates (ADCs) are gradually revolutionizing clinical cancer therapy. The antibody–drug conjugate linker molecule determines both the efficacy and the adverse effects, and so has a major influence on the fate of ADCs. An ideal linker should be stable in the circulatory system and release the cytotoxic payload specifically in the tumor. However, existing linkers often release payloads nonspecifically and inevitably lead to off-target toxicity. This defect is becoming an increasingly important factor that restricts the development of ADCs. The pursuit of ADCs with optimal therapeutic windows has resulted in remarkable progress in the discovery and development of novel linkers. The present review summarizes the advance of the chemical trigger, linker‒antibody attachment and linker‒payload attachment over the last 5 years, and describes the ADMET properties of ADCs. This work also helps clarify future developmental directions for the linkers.

Trop-2 Therapy in Metastatic Triple-Negative Breast Cancer in Italy: Clinical Opportunity and Regulatory Pitfalls

Trop-2 is an ideal candidate for targeted therapeutics because it is a transmembrane protein with an extracellular domain overexpressed in a wide variety of tumors, and is upregulated in normal cells. Consequently, several Trop-2-targeted drugs have recently been developed for clinical use, such as anti-Trop-2 antibodies. Sacituzumab govitecan, a Trop-2-directed antibody and topoisomerase inhibitor drug conjugate, was recently approved by the Food and Drug Administration (FDA) and European Medicines Agency (EMA) for the treatment of metastatic triple-negative breast cancer and metastatic urothelial cancer. In Italy, this treatment cannot be used in clinical practice because it has not yet been approved by the Agenzia Italiana del Farmaco (AIFA, Rome, Italy). In Italy, this is not a new problem, in fact, when a new compound is approved by the U.S. and Europe, there is often a delay in its approval for use. The adoption of universal guidelines and the standardization of Trop-2 evaluation is urgently needed.

Case report of sacituzumab govitecan-hziy-induced neutropenia in a patient with metastatic triple-negative breast cancer and a uridine diphosphate glucuronosyltransferase family 1 member A1 poor metabolizer genotype

INTRODUCTION

Sacituzumab govitecan-hziy, approved in 2020 for treatment of metastatic triple-negative breast cancer, provides a new option for a population with a historically poor prognosis with standard chemotherapy. Uridine diphosphate glucuronosyltransferase family 1 member A1 poor metabolizers are at increased risk for profound neutropenia. This case discusses clinical implications of the uridine diphosphate glucuronosyltransferase family 1 member A1*28/*28 genotype in patients receiving sacituzumab govitecan-hziy.

CASE REPORT

A 38-year-old otherwise healthy pre-menopausal female of South Asian descent was diagnosed with non-metastatic, hormone receptor-positive, and human epidermal growth factor receptor 2-negative breast cancer. This was treated with neoadjuvant chemotherapy and multiple lines of subsequent therapies. Upon finding bone metastasis, an additional six lines of therapy ensued. In total, 3.5 years post-diagnosis, sacituzumab govitecan-hziy was started for disease transformation to triple-negative status.

MANAGEMENT AND OUTCOME

Sacituzumab govitecan-hziy was initiated at the Food and Drug Administration-approved 10 mg/kg/dose on days 1 and 8 of a 21-day cycle. Grade 4 neutropenia occurred after one dose. Pharmacogenomics testing identified the patient as a uridine diphosphate glucuronosyltransferase family 1 member A1*28 homozygous expressor. Sacituzumab govitecan-hziy was dose-reduced, and granulocyte colony-stimulating factor was administered due to the severity of neutropenia. The patient continued on sacituzumab govitecan-hziy until disease progression.

DISCUSSION

Sacituzumab govitecan-hziy's propensity to cause neutropenia is multifactorial. Although incidence of all-grade neutropenia from sacituzumab govitecan-hziy is elevated for uridine diphosphate glucuronosyltransferase family 1 member A1*28 homozygous expressors, this does not translate to increased risk for febrile neutropenia. Detailed guidance is lacking regarding empiric dose adjustments or prophylactic granulocyte colony-stimulating factor for these patients.¹ Currently, pre-sacituzumab govitecan-hziy pharmacogenomics testing to identify uridine diphosphate glucuronosyltransferase family 1 member A1 poor metabolizers is not recommended, and the cost-effectiveness of this approach is unclear.