Milatuzumab-SN-38 conjugates for the treatment of CD74+ cancers

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.

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.

Macrophage Migration Inhibitory Factor (MIF) and D-Dopachrome Tautomerase (DDT): Pathways to Tumorigenesis and Therapeutic Opportunities

Discovered as inflammatory cytokines, MIF and DDT exhibit widespread expression and have emerged as critical mediators in the response to infection, inflammation, and more recently, in cancer. In this comprehensive review, we provide details on their structures, binding partners, regulatory mechanisms, and roles in cancer. We also elaborate on their significant impact in driving tumorigenesis across various cancer types, supported by extensive in vitro, in vivo, bioinformatic, and clinical studies. To date, only a limited number of clinical trials have explored MIF as a therapeutic target in cancer patients, and DDT has not been evaluated. The ongoing pursuit of optimal strategies for targeting MIF and DDT highlights their potential as promising antitumor candidates. Dual inhibition of MIF and DDT may allow for the most effective suppression of canonical and non-canonical signaling pathways, warranting further investigations and clinical exploration.

Therapy for Hormone Receptor-Positive, Human Epidermal Growth Receptor 2-Negative Metastatic Breast Cancer Following Treatment Progression via CDK4/6 Inhibitors: A Literature Review

Endocrine therapy (ET) with a cyclin-dependent kinase 4/6 inhibitor (CDK4/6i) is currently the first-line standard treatment for most patients with hormone receptor-positive (HR+) and human epidermal growth receptor 2-negative (HER2-) metastatic or advanced breast cancer. However, the majority of tumors response to and eventually develop resistance to CDK4/6is. The mechanisms of resistance are poorly understood, and the optimal postprogression treatment regimens and their sequences continue to evolve in the rapidly changing treatment landscape. In this review, we generally summarize the mechanisms of resistance to CDK4/6is and ET, and describe the findings from clinical trials using small molecule inhibitors, antibody-drug conjugates and immunotherapy, providing insights into how these novel strategies may reverse treatment resistance, and discussing how some have not translated into clinical benefit. Finally, we provide rational treatment strategies based on the current emerging evidence.

In Silico Approach to Molecular Profiling of the Transition from Ovarian Epithelial Cells to Low-Grade Serous Ovarian Tumors for Targeted Therapeutic Insights

This paper aims to elucidate the differentially coexpressed genes, their potential mechanisms, and possible drug targets in low-grade invasive serous ovarian carcinoma (LGSC) in terms of the biologic continuity of normal, borderline, and malignant LGSC. We performed a bioinformatics analysis, integrating datasets generated using the GPL570 platform from different studies from the GEO database to identify changes in this transition, gene expression, drug targets, and their relationships with tumor microenvironmental characteristics. In the transition from ovarian epithelial cells to the serous borderline, the FGFR3 gene in the "Estrogen Response Late" pathway, the ITGB2 gene in the "Cell Adhesion Molecule", the CD74 gene in the "Regulation of Cell Migration", and the IGF1 gene in the "Xenobiotic Metabolism" pathway were upregulated in the transition from borderline to LGSC. The ERBB4 gene in "Proteoglycan in Cancer", the AR gene in "Pathways in Cancer" and "Estrogen Response Early" pathways, were upregulated in the transition from ovarian epithelial cells to LGSC. In addition, SPP1 and ITGB2 genes were correlated with macrophage infiltration in the LGSC group. This research provides a valuable framework for the development of personalized therapeutic approaches in the context of LGSC, with the aim of improving patient outcomes and quality of life. Furthermore, the main goal of the current study is a preliminary study designed to generate in silico inferences, and it is also important to note that subsequent in vitro and in vivo studies will be necessary to confirm the results before considering these results as fully reliable.

Crosstalk of nervous and immune systems in pancreatic cancer

Pancreatic cancer is a highly malignant tumor known for its extremely low survival rate. The combination of genetic disorders within pancreatic cells and the tumor microenvironment contributes to the emergence and progression of this devastating disease. Extensive research has shed light on the nature of the microenvironmental cells surrounding the pancreatic cancer, including peripheral nerves and immune cells. Peripheral nerves release neuropeptides that directly target pancreatic cancer cells in a paracrine manner, while immune cells play a crucial role in eliminating cancer cells that have not evaded the immune response. Recent studies have revealed the intricate interplay between the nervous and immune systems in homeostatic condition as well as in cancer development. In this review, we aim to summarize the function of nerves in pancreatic cancer, emphasizing the significance to investigate the neural-immune crosstalk during the advancement of this malignant cancer.

Therapeutic Oligonucleotides: An Outlook on Chemical Strategies to Improve Endosomal Trafficking

The potential of oligonucleotide therapeutics is undeniable as more than 15 drugs have been approved to treat various diseases in the liver, central nervous system (CNS), and muscles. However, achieving effective delivery of oligonucleotide therapeutics to specific tissues still remains a major challenge, limiting their widespread use. Chemical modifications play a crucial role to overcome biological barriers to enable efficient oligonucleotide delivery to the tissues/cells of interest. They provide oligonucleotide metabolic stability and confer favourable pharmacokinetic/pharmacodynamic properties. This review focuses on the various chemical approaches implicated in mitigating the delivery problem of oligonucleotides and their limitations. It highlights the importance of linkers in designing oligonucleotide conjugates and discusses their potential role in escaping the endosomal barrier, a bottleneck in the development of oligonucleotide therapeutics.

Immunotherapy in hematologic malignancies: achievements, challenges and future prospects

The immune-cell origin of hematologic malignancies provides a unique avenue for the understanding of both the mechanisms of immune responsiveness and immune escape, which has accelerated the progress of immunotherapy. Several categories of immunotherapies have been developed and are being further evaluated in clinical trials for the treatment of blood cancers, including stem cell transplantation, immune checkpoint inhibitors, antigen-targeted antibodies, antibody-drug conjugates, tumor vaccines, and adoptive cell therapies. These immunotherapies have shown the potential to induce long-term remission in refractory or relapsed patients and have led to a paradigm shift in cancer treatment with great clinical success. Different immunotherapeutic approaches have their advantages but also shortcomings that need to be addressed. To provide clinicians with timely information on these revolutionary therapeutic approaches, the comprehensive review provides historical perspectives on the applications and clinical considerations of the immunotherapy. Here, we first outline the recent advances that have been made in the understanding of the various categories of immunotherapies in the treatment of hematologic malignancies. We further discuss the specific mechanisms of action, summarize the clinical trials and outcomes of immunotherapies in hematologic malignancies, as well as the adverse effects and toxicity management and then provide novel insights into challenges and future directions.

Antibody-Drug Conjugates in Gynecologic Cancer

The present article reviews the current evidence for antibody-drug conjugates (ADCs) in gynecologic cancer. ADCs consist of a highly selective monoclonal antibody for a tumor-associated antigen and a potent cytotoxic payload conjugated through a linker. Overall, the toxicity profiles of ADCs are manageable. Ocular toxicity is a known class effect of some ADCs and is managed with prophylactic corticosteroid and vasoconstrictor eye drops as well as dose interruptions/holds and dose modifications. In ovarian cancer, mirvetuximab soravtansine, an ADC targeting alpha-folate receptor (FRα), received US Food and Drug Administration (FDA) accelerated approval in November 2022 after data from the single-arm phase III SORAYA trial. A second ADC targeting FRα, STRO-002, received FDA fast track designation in August 2021. Multiple studies with upifitamab rilsodotin, an ADC comprising a NaPi2B-binding antibody, are underway. In cervical cancer, tisotumab vedotin, an ADC-targeting tissue factor, received FDA accelerated approval in September 2021 after the phase II innovaTV 204 trial. Tisotumab vedotin in combination with chemotherapy and other targeted agents is currently being evaluated. Although there are no currently approved ADCs for endometrial cancer, there are many under active evaluation, including mirvetuximab soravtansine. Trastuzumab-deruxtecan (T-DXd), an ADC targeting human epidermal growth factor receptor 2 (HER2), is currently approved for HER2-positive and HER2-low breast cancer and shows promise in endometrial cancer. Like all anticancer treatments, the decision for a patient to undergo therapy with an ADC is a personal choice that balances the potential benefits with the side effects and requires thorough and compassionate support of their physician and care team and shared decision making.

Recent advances in SN-38 drug delivery system

DNA topoisomerase I plays a key role in lubricatingthe wheels of DNA replication or RNA transcription through breaking and reconnecting DNA single-strand. It is widely known that camptothecin and its derivatives (CPTs) have inhibitory effects on topoisomerases I, and have obtained some clinical benefits in cancer treatment. The potent cytotoxicity makes 7-ethyl-10-hydroxycamptothecin (SN-38) become a brilliant star among these derivatives. However, some undesirable physical and chemical properties of this compound, including poor solubility and stability, seriously hinder its effective delivery to tumor sites. In recent years, strategies to alleviate these defects have aroused extensive research interest. By focusing on the loading mechanism, basic nanodrug delivery systems with SN-38 loaded, like nanoparticles, liposomes and micelles, are demonstrated here. Additionally, functionalized nanodrug delivery systems of SN-38 including prodrug and active targeted nanodrug delivery systems and delivery systems designed to overcome drug resistance are also reviewed. At last, challenges for future research in formulation development and clinical translation of SN-38 drug delivery system are discussed.

Payload diversification: a key step in the development of antibody-drug conjugates

Antibody-drug conjugates (ADCs) is a fast moving class of targeted biotherapeutics that currently combines the selectivity of monoclonal antibodies with the potency of a payload consisting of cytotoxic agents. For many years microtubule targeting and DNA-intercalating agents were at the forefront of ADC development. The recent approval and clinical success of trastuzumab deruxtecan (Enhertu^®) and sacituzumab govitecan (Trodelvy^®), two topoisomerase 1 inhibitor-based ADCs, has shown the potential of conjugating unconventional payloads with differentiated mechanisms of action. Among future developments in the ADC field, payload diversification is expected to play a key role as illustrated by a growing number of preclinical and clinical stage unconventional payload-conjugated ADCs. This review presents a comprehensive overview of validated, forgotten and newly developed payloads with different mechanisms of action.

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.

Targeted therapies and checkpoint inhibitors in sarcoma

Sarcomas are defined as a group of mesenchymal malignancies with over 100 heterogeneous subtypes. As a rare and difficult to diagnose entity, micrometastasis is already present at the time of diagnosis in many cases. Current treatment practice of sarcomas consists mainly of surgery, (neo)adjuvant chemo- and/or radiotherapy. Although the past decade has shown that particular genetic abnormalities can promote the development of sarcomas, such as translocations, gain-of-function mutations, amplifications or tumor suppressor gene losses, these insights have not led to established alternative treatment strategies so far. Novel therapeutic concepts with immunotherapy at its forefront have experienced some remarkable success in different solid tumors while their impact in sarcoma remains limited. In this review, the most common immunotherapy strategies in sarcomas, such as immune checkpoint inhibitors, targeted therapy and cytokine therapy are concisely discussed. The programmed cell death (PD)-1/PD-1L axis and apoptosis-inducing cytokines, such as TNF-related apoptosis-inducing ligand (TRAIL), have not yielded the same success like in other solid tumors. However, in certain sarcoma subtypes, e.g. liposarcoma or undifferentiated pleomorphic sarcoma, encouraging results in some cases when employing immune checkpoint inhibitors in combination with other treatment options were found. Moreover, newer strategies such as the targeted therapy against the ancient cytokine macrophage migration inhibitory factor (MIF) may represent an interesting approach worth investigation in the future.

Development of therapeutic antibodies for the treatment of diseases

Since the first monoclonal antibody drug, muromonab-CD3, was approved for marketing in 1986, 165 antibody drugs have been approved or are under regulatory review worldwide. With the approval of new drugs for treating a wide range of diseases, including cancer and autoimmune and metabolic disorders, the therapeutic antibody drug market has experienced explosive growth. Monoclonal antibodies have been sought after by many biopharmaceutical companies and scientific research institutes due to their high specificity, strong targeting abilities, low toxicity, side effects, and high development success rate. The related industries and markets are growing rapidly, and therapeutic antibodies are one of the most important research and development areas in the field of biology and medicine. In recent years, great progress has been made in the key technologies and theoretical innovations provided by therapeutic antibodies, including antibody-drug conjugates, antibody-conjugated nuclides, bispecific antibodies, nanobodies, and other antibody analogs. Additionally, therapeutic antibodies can be combined with technologies used in other fields to create new cross-fields, such as chimeric antigen receptor T cells (CAR-T), CAR-natural killer cells (CAR-NK), and other cell therapy. This review summarizes the latest approved or in regulatory review therapeutic antibodies that have been approved or that are under regulatory review worldwide, as well as clinical research on these approaches and their development, and outlines antibody discovery strategies that have emerged during the development of therapeutic antibodies, such as hybridoma technology, phage display, preparation of fully human antibody from transgenic mice, single B-cell antibody technology, and artificial intelligence-assisted antibody discovery.

SN-38 Sensitizes BRCA-Proficient Ovarian Cancers to PARP Inhibitors through Inhibiting Homologous Recombination Repair

As a multifunctional protein posttranslational modification enzyme in eukaryotic cells, Poly-ADP-ribose polymerase (PARP) acts as a DNA damage sensor, which helps to repair DNA damage through recruiting repair proteins to the DNA break sites. PARP inhibitors offer a significant clinical benefit for ovarian cancer with BRCA1/2 mutations. However, the majority of ovarian cancer patients harbor wild-type (WT) BRCA1/2 status, which narrows its clinical application. Here, we identified a small compound, SN-38, a CPT analog, which sensitizes BRCA-proficient ovarian cancer cells to PARP inhibitor treatment by inhibiting homologous recombination (HR) repair. SN-38 treatment greatly enhanced PARP inhibitor olaparib induced DNA double-strand breaks (DSBs) and DNA replication stress. Meanwhile, the combination of SN-38 and olaparib synergistically induced apoptosis in ovarian cancer. Furthermore, combination administration of SN-38 and olaparib induced synergistic antitumor efficacy in an ovarian cancer xenograft model in vivo. Therefore, our study provides a novel therapeutic strategy to optimize PARP inhibitor therapy for patients with BRCA-proficient ovarian cancer.

Perineural invasion-associated biomarkers for tumor development

Perineural invasion (PNI) is the process of neoplastic invasion of peripheral nerves and is considered to be the fifth mode of cancer metastasis. PNI has been detected in head and neck tumors and pancreatic, prostate, bile duct, gastric, and colorectal cancers. It leads to poor prognostic outcomes and high local recurrence rates. Despite the increasing number of studies on PNI, targeted therapeutic modalities have not been proposed. The identification of PNI-related biomarkers would facilitate the non-invasive and early diagnosis of cancers, the establishment of prognostic panels, and the development of targeted therapeutic approaches. In this review, we compile information on the molecular mediators involved in PNI-associated cancers. The expression and prognostic significance of molecular mediators and their receptors in PNI-associated cancers are analyzed, and the possible mechanisms of action of these mediators in PNI are explored, as well as the association of cells in the microenvironment where PNI occurs.

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.

Potential of antibody-drug conjugates (ADCs) for cancer therapy

The primary purpose of ADCs is to increase the efficacy of anticancer medications by minimizing systemic drug distribution and targeting specific cells. Antibody conjugates (ADCs) have changed the way cancer is treated. However, because only a tiny fraction of patients experienced long-term advantages, current cancer preclinical and clinical research has been focused on combination trials. The complex interaction of ADCs with the tumor and its microenvironment appear to be reliant on the efficacy of a certain ADC, all of which have significant therapeutic consequences. Several clinical trials in various tumor types are now underway to examine the potential ADC therapy, based on encouraging preclinical results. This review tackles the potential use of ADCs in cancer therapy, emphasizing the essential processes underlying their positive therapeutic impacts on solid and hematological malignancies. Additionally, opportunities are explored to understand the mechanisms of ADCs action, the mechanism of resistance against ADCs, and how to overcome potential resistance following ADCs administration. Recent clinical findings have aroused interest, leading to a large increase in the number of ADCs in clinical trials. The rationale behind ADCs, as well as their primary features and recent research breakthroughs, will be discussed. We then offer an approach for maximizing the potential value that ADCs can bring to cancer patients by highlighting key ideas and distinct strategies.

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.

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.

Analysis of patients without and with an initial triple-negative breast cancer diagnosis in the phase 3 randomized ASCENT study of sacituzumab govitecan in metastatic triple-negative breast cancer

PURPOSE

Sacituzumab govitecan (SG) is an antibody-drug conjugate composed of an anti-Trop-2 antibody coupled to SN-38 via a proprietary hydrolyzable linker. In the ASCENT study, SG improved survival versus single-agent treatment of physician's choice (TPC) in pre-treated metastatic triple-negative breast cancer (mTNBC). Hormone/HER2 receptor changes are common, particularly at relapse/metastasis. This subanalysis assessed outcomes in patients who did/did not have TNBC at initial diagnosis, before enrollment.

METHODS

TNBC diagnosis was only required at study entry. Patients with mTNBC refractory/relapsing after ≥ 2 prior chemotherapies were randomized 1:1 to receive SG or TPC. Primary endpoint was progression-free survival (PFS) in patients without brain metastases.

RESULTS

Overall, 70/235 (30%) and 76/233 (33%) patients who received SG and TPC, respectively, did not have TNBC at initial diagnosis. Clinical benefit with SG versus TPC was observed in this subset. Median PFS was 4.6 versus 2.3 months (HR 0.48; 95% CI 0.32-0.72), median overall survival was 12.4 versus 6.7 months (HR 0.44; 95% CI 0.30-0.64), and objective response rate (ORR) was 31% versus 4%; those who also received prior CDK4/6 inhibitors had ORRs of 21% versus 5%. Efficacy and safety for patients with TNBC at initial diagnosis were generally similar to those who did not present with TNBC at initial diagnosis.

CONCLUSION

Patients without TNBC at initial diagnosis had improved clinical outcomes and a manageable safety profile with SG, supporting SG as a treatment option for mTNBC regardless of subtype at initial diagnosis. Subtype reassessment in advanced breast cancer allows for optimal treatment. Clinical trial registration number NCT02574455, registered October 12, 2015.

Engineered protein nanodrug as an emerging therapeutic tool

Functional proteins are the most versatile macromolecules. They can be obtained by extraction from natural sources or by genetic engineering technologies. The outstanding selectivity, specificity, binding activity, and biocompatibility endow engineered proteins with outstanding performance for disease therapy. Nevertheless, their stability is dramatically impaired in blood circulation, hindering clinical translations. Thus, many strategies have been developed to improve the stability, efficacy, bioavailability, and productivity of therapeutic proteins for clinical applications. In this review, we summarize the recent progress in the fabrication and application of therapeutic proteins. We first introduce various strategies for improving therapeutic efficacy via bioengineering and nanoassembly. Furthermore, we highlight their diverse applications as growth factors, nanovaccines, antibody-based drugs, bioimaging molecules, and cytokine receptor antagonists. Finally, a summary and perspective for the future development of therapeutic proteins are presented.

Cellular-Resolution Imaging of Bystander Payload Tissue Penetration from Antibody-Drug Conjugates

After several notable clinical failures in early generations, antibody-drug conjugates (ADCs) have made significant gains with seven new FDA-approvals within the last 3 years. These successes have been driven by a shift towards mechanistically informed ADC design, where the payload, linker, drug-to-antibody ratio, and conjugation are increasingly tailored to a specific target and clinical indication. However, fundamental aspects needed for design, such as payload distribution, remain incompletely understood. Payloads are often classified as 'bystander' or 'non-bystander' depending on their ability to diffuse out of targeted cells into adjacent cells that may be antigen negative or more distant from tumor vessels, helping to overcome heterogeneous distribution. Seven of the eleven FDA-approved ADCs employ these bystander payloads, but the depth of penetration and cytotoxic effects as a function of physicochemical properties and mechanism of action have not been fully characterized. Here, we utilized tumor spheroids and pharmacodynamic marker staining to quantify tissue penetration of the three major classes of agents: microtubule inhibitors, DNA-damaging agents, and topoisomerase inhibitors. PAMPA data and co-culture assays were performed to compare to the 3D tissue culture data. The results demonstrate a spectrum in bystander potential and tissue penetration depending on the physicochemical properties and potency of the payload. Generally, directly targeted cells show a greater response even with bystander payloads, consistent with the benefit of deeper ADC penetration. These results are compared to computational simulations to help scale the data from in vitro and preclinical animal models to the clinic.

Synthesis and evaluation of highly releasable and structurally stable antibody-SN-38-conjugates

Camptothecins, traditional chemotherapy drugs, have been clinically used in antibody-drug conjugates (ADCs), which refreshes the recognition that ADCs preferably incorporate highly potent payloads. However, SN-38, active metabolite of irinotecan from camptothecins, tended to be incorporated into ADCs with an unstable acid sensitive bond, not with the widely used Cathepsin B (CTSB) sensitive bond, which may pose the risk of off-target. Herein, we reported a novel strategy to construct highly releasable and structurally stable SN-38-conjugates, in which CTSB linkers directly connected to the 10-OH group through ether bond, not to the common 20-OH group of lactones of SN-38. In this paper, rapid release of SN-38 was skillfully demonstrated by utilizing the fluorescence properties of SN-38. The SN-38-ether-ADC displayed highly stable serum stability with the half-life over 10 days. Moreover, the drug-antibody-ratio (DAR) of ADC could be elevated to 7.1 through the introduction of polyethylene glycol (PEG) moieties without aggregation. The optimized ADC exhibited potent in vitro activities up to 5.5 nM, comparable to SN-38. Moreover, this ADC group significantly delayed tumor growth in vivo. In conclusion, the novel strategy has the potential to promote the development of SN38-ADCs and enrich the conjugation approaches for hydroxyl-bearing payloads.

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.

Antibody drug conjugates in gastrointestinal cancer: From lab to clinical development

The antibody-drug conjugates (ADCs) are one the fastest growing biotherapeutics in oncology and are still in their infancy in gastrointestinal (GI) cancer for clinical applications to improve patient survival. The ADC based approach is developed with tumor specific antigen, antibody carrying cytotoxic agents to precisely target and deliver chemotherapeutics at the tumor site. To date, 11 ADCs have been approved by US-FDA, and more than 80 are in the clinical development phase for different oncological indications. However, The ADCs based therapies in GI cancers are still far from having high-efficient clinical outcomes. The limited success of these ADCs and lessons learned from the past are now being used to develop a newer generation of ADC against GI cancers. In this review, we did a comprehensive assessment of the key components of ADCs, including tumor marker, antibody, cytotoxic payload, and linkage strategy, with a focus on technical improvement and some future trends in the pipeline for clinical translation. The various preclinical and clinical ADCs used in gastrointestinal malignancies, their target, composition and bioconjugation, along with preclinical and clinical outcomes, are discussed. The emphasis is also given to new generation ADCs employing novel mAb, payload, linker, and bioconjugation methods are also included.

Therapeutic roles of antibody drug conjugates (ADCs) in relapsed/refractory lymphomas

Relapsed or refractory lymphoma is commonly treated with combination chemoimmunotherapy and cellular immunotherapy. Modest response rates and associated toxicities are obstacles to achieving durable remission using traditional cytotoxic chemotherapy, especially in frail patients with advanced disease. Antibody drug conjugates represent a new class of novel targeted agents with significant improvement in therapeutic efficacy in the treatment of lymphomas. Several of these agents, which offer improved targeting, greater potency, and better therapeutic index over traditional chemotherapy, are changing the treatment landscape for lymphomas and other hematological malignancies. Despite the therapeutic potential of these agents, the delivery and release of cytotoxic agents to malignant cells through the combination of a monoclonal antibody, payload, and linker represents a complex design challenge. This article reviews the clinical data on currently available antibody drug conjugates and the ongoing development of novel antibody drug conjugates. Antibody drug conjugates constitute an important armamentarium for treatment of lymphomas and their evolving roles in the treatment spectrum are discussed.

Predictive Platforms of Bond Cleavage and Drug Release Kinetics for Macromolecule–Drug Conjugates

Macromolecule–drug conjugates (MDCs) occupy a critical niche in modern pharmaceuticals that deals with the assembly and combination of a macromolecular carrier, a drug cargo, and a linker toward the creation of effective therapeutics. Macromolecular carriers such as synthetic biocompatible polymers and proteins are often exploited for their inherent ability to improve drug circulation, prevent off-target drug cytotoxicity, and widen the therapeutic index of drugs. One of the most significant challenges in MDC design involves tuning their drug release kinetics to achieve high spatiotemporal precision. This level of control requires a thorough qualitative and quantitative understanding of the bond cleavage event. In this review, we highlight specific research findings that emphasize the importance of establishing a precise structure–function relationship for MDCs that can be used to predict their bond cleavage and drug release kinetic parameters.

Role of Atypical Chemokines and Chemokine Receptors Pathways in the Pathogenesis of COPD

Chronic obstructive pulmonary disease (COPD) represents a heightened inflammatory response in the lung generally resulting from tobacco smoking-induced recruitment and activation of inflammatory cells and/or activation of lower airway structural cells. Several mediators can modulate activation and recruitment of these cells, particularly those belonging to the chemokines (conventional and atypical) family. There is emerging evidence for complex roles of atypical chemokines and their receptors (such as high mobility group box 1 (HMGB1), antimicrobial peptides, receptor for advanced glycosylation end products (RAGE) or toll-like receptors (TLRs)) in the pathogenesis of COPD, both in the stable disease and during exacerbations. Modulators of these pathways represent potential novel therapies for COPD and many are now in preclinical development. Inhibition of only a single atypical chemokine or receptor may not block inflammatory processes because there is redundancy in this network. However, there are many animal studies that encourage studies for modulating the atypical chemokine network in COPD. Thus, few pharmaceutical companies maintain a significant interest in developing agents that target these molecules as potential antiinflammatory drugs. Antibody-based (biological) and small molecule drug (SMD)-based therapies targeting atypical chemokines and/or their receptors are mostly at the preclinical stage and their progression to clinical trials is eagerly awaited. These agents will most likely enhance our knowledge about the role of atypical chemokines in COPD pathophysiology and thereby improve COPD management.

Rapid Progress in Immunotherapies for Multiple Myeloma: An Updated Comprehensive Review

Despite rapid advances in treatment approaches of multiple myeloma (MM) over the last two decades via proteasome inhibitors (PIs), immunomodulatory drugs (IMiDs), and monoclonal antibodies (mAbs), their efficacies are limited. MM still remains incurable, and the majority of patients shortly relapse and eventually become refractory to existing therapies due to the genetic heterogeneity and clonal evolution. Therefore, the development of novel therapeutic strategies with different mechanisms of action represents an unmet need to achieve a deep and highly durable response as well as to improve patient outcomes. The antibody-drug conjugate (ADC), belanatmab mafadotin, which targets B cell membrane antigen (BCMA) on plasma cells, was approved for the treatment of MM in 2020. To date, numerous immunotherapies, including bispecific antibodies, such as bispecific T cell engager (BiTE), the duobody adoptive cellular therapy using a dendritic cell (DC) vaccine, autologous chimeric antigen (CAR)-T cells, allogeneic CAR-natural killer (NK) cells, and checkpoint inhibitors have been developed for the treatment of MM, and a variety of clinical trials are currently underway or are expected to be planned. In the future, the efficacy of combination approaches, as well as allogenic CAR-T or NK cell therapy, will be examined, and promising results may alter the treatment paradigm of MM. This is a comprehensive review with an update on the most recent clinical and preclinical advances with a focus on results from clinical trials in progress with BCMA-targeted immunotherapies and the development of other novel targets in MM. Future perspectives will also be discussed.

CD74+ macrophages are associated with favorable prognosis and immune contexture in hepatocellular carcinoma

CD74 was initially thought to participate mainly in antigen presentation as an MHC class II chaperone. Recent studies have shown that CD74 plays an important role within the cell and throughout the immune system in a wide spectrum of neoplasms. However, the role of CD74 in hepatocellular carcinoma (HCC) remains elusive. In this study, HCC tissues from Zhongshan Hospital and data from The Cancer Genome Atlas (TCGA) were obtained and analyzed. Immunohistochemistry, flow cytometry, and single-cell RNA sequencing (scRNA-seq) were performed to detect the characteristics of CD74⁺ cells and explore their impact on the tumor microenvironment (TME) of HCC. Our data revealed that stromal CD74⁺ cell enrichment was associated with favorable prognosis in patients with HCC. CD74 was abundant in a large portion of HCC specimens and prominently distributed on stromal macrophages. scRNA-seq data also indicated that the pathways related to immune response were significantly upregulated in CD74⁺ macrophages. High infiltration of CD74⁺ macrophages was associated with increased infiltration of CD8⁺ cytotoxic T lymphocytes (CTLs) with enhanced effector functions in HCC. Besides, blocking CD74 weakened the antitumor activity and proliferation ability of CD8⁺ CTLs in HCC. Our findings highlight the critical role of CD74 in HCC. New drugs and antibodies targeting CD74 may be effective strategies for HCC therapy.

CD74 promotes perineural invasion of cancer cells and mediates neuroplasticity via the AKT/EGR-1/GDNF axis in pancreatic ductal adenocarcinoma

Perineural invasion (PNI) is a common feature of pancreatic ductal adenocarcinoma (PDAC) and is one of the important causes of local recurrence in resected pancreatic cancer, but the molecular mechanism remains largely unexplored. Here, we used immunohistochemistry staining to determine the expression of CD74. Then the in vivo PNI model, in vitro neuroplasticity assay, cell proliferation assay, wound healing and Transwell-based invasion assay were performed to examine the function of CD74 in pancreatic cancer cell lines. ChIP assay and Luciferase reporter assay were used to illustrate the mechanism underlying CD74 induced GDNF expression. We confirmed that the expression level of CD74 was an independent predictor of PNI and poor prognosis for PDAC. Moreover, we found that upregulation of CD74 on PDAC enhanced its migration and invasive capabilities and potentiated the secretion of neurotrophic factor GDNF to promote the neuroplasticity. Mechanistically, CD74 promoted GDNF production via the AKT/EGR-1/GDNF axis in PDAC. Taken together, our findings suggest a supportive role of CD74 in the PNI of PDAC, and deepen our understanding of how cancer cells promote neuroplasticity in the microenvironment of PDAC.

Sacituzumab govitecan, a Trop-2-directed antibody-drug conjugate, for patients with epithelial cancer: final safety and efficacy results from the phase I/II IMMU-132-01 basket trial

BACKGROUND

Sacituzumab govitecan (SG), a trophoblast cell surface antigen-2 (Trop-2)-directed antibody-drug conjugate, has demonstrated antitumor efficacy and acceptable tolerability in a phase I/II multicenter trial (NCT01631552) in patients with advanced epithelial cancers. This report summarizes the safety data from the overall safety population (OSP) and efficacy data, including additional disease cohorts not published previously.

PATIENTS AND METHODS

Patients with refractory metastatic epithelial cancers received intravenous SG (8, 10, 12, or 18 mg/kg) on days 1 and 8 of 21-day cycles until disease progression or unacceptable toxicity. Endpoints for the OSP included safety and pharmacokinetic parameters with investigator-evaluated objective response rate (ORR per RECIST 1.1), duration of response, clinical benefit rate, progression-free survival, and overall survival evaluated for cohorts (n > 10 patients) of small-cell lung, colorectal, esophageal, endometrial, pancreatic ductal adenocarcinoma, and castrate-resistant prostate cancer.

RESULTS

In the OSP (n = 495, median age 61 years, 68% female; UGT1A1∗28 homozygous, n = 46; 9.3%), 41 (8.3%) permanently discontinued treatment due to adverse events (AEs). Most common treatment-related AEs were nausea (62.6%), diarrhea (56.2%), fatigue (48.3%), alopecia (40.4%), and neutropenia (57.8%). Most common treatment-related serious AEs (n = 75; 15.2%) were febrile neutropenia (4.0%) and diarrhea (2.8%). Grade ≥3 neutropenia and febrile neutropenia occurred in 42.4% and 5.3% of patients, respectively. Neutropenia (all grades) was numerically more frequent in UGT1A1∗28 homozygotes (28/46; 60.9%) than heterozygotes (69/180; 38.3%) or UGT1A1∗1 wild type (59/177; 33.3%). There was one treatment-related death due to an AE of aspiration pneumonia. Partial responses were seen in endometrial cancer (4/18, 22.2% ORR) and small-cell lung cancer (11/62, 17.7% ORR), and one castrate-resistant prostate cancer patient had a complete response (n = 1/11; 9.1% ORR).

CONCLUSIONS

SG demonstrated a toxicity profile consistent with previous published reports. Efficacy was seen in several cancer cohorts, which validates Trop-2 as a broad target in solid tumors.

MIF inhibition as a strategy for overcoming resistance to immune checkpoint blockade therapy in melanoma

Immune checkpoint blockade (ICB) has demonstrated an impressive outcome in patients with metastatic melanoma, yet, durable complete response; even with Ipilimumab/Nivolumab combo are under 30%. Primary and acquired resistance in response to ICB is commonly due to a tumor immune escape mechanism dictated by the tumor microenvironment (TME). Macrophage Migratory Inhibition Factor (MIF) has emerged as an immunosuppressive factor secreted in the TME. We have previously demonstrated that blockade of the MIF-CD74 signaling on macrophages and dendritic cells restored the anti-tumor immune response against melanoma. Here, we report that inhibition of the MIF-CD74 axis combined with ipilimumab could render resistant melanoma to better respond to anti-CTLA-4 treatment. We provide evidence that blocking the MIF-CD74 signaling potentiates CD8+ T-cells infiltration and drives pro-inflammatory M1 conversion of macrophages in the TME. Furthermore, MIF inhibition resulted in reprogramming the metabolic pathway by reducing lactate production, HIF-1α and PD-L1 expression in the resistant melanoma cells. Melanoma patient data extracted from the TCGA database supports the hypothesis that high MIF expression strongly correlates with poor response to ICB therapy. Our findings provide a rationale for combining anti-CTLA-4 with MIF inhibitors as a potential strategy to overcome resistance to ICB therapy in melanoma, turning a "cold" tumor into a "hot" one mediated by the activation of innate immunity and reprogramming of tumor metabolism and reduced PD-L1 expression in melanoma cells.

Making smart drugs smarter: The importance of linker chemistry in targeted drug delivery

Smart drugs, such as antibody-drug conjugates, for targeted therapy rely on the ability to deliver a warhead to the desired location and to achieve activation at the same site. Thus, designing a smart drug often requires proper linker chemistry for tethering the warhead with a vehicle in such a way that either allows the active drug to retain its potency while being tethered or ensures release and thus activation at the desired location. Recent years have seen much progress in the design of new linker activation strategies. Herein, we review the recent development of chemical strategies used to link the warhead with a delivery vehicle for preferential cleavage at the desired sites.

Sacituzumab govitecan in previously treated hormone receptor-positive/HER2-negative metastatic breast cancer: final results from a phase I/II, single-arm, basket trial

BACKGROUND

Trophoblast cell-surface antigen-2 (Trop-2) is expressed in epithelial cancers, including hormone receptor-positive (HR+) metastatic breast cancer (mBC). Sacituzumab govitecan (SG; Trodelvy®) is an antibody-drug conjugate composed of a humanized anti-Trop-2 monoclonal antibody coupled to SN-38 at a high drug-to-antibody ratio via a unique hydrolyzable linker that delivers SN-38 intracellularly and in the tumor microenvironment. SG was granted accelerated FDA approval for metastatic triple-negative BC treatment in April 2020.

PATIENTS AND METHODS

We analyzed a prespecified subpopulation of patients with HR+/human epidermal growth factor receptor 2-negative (HER2-) HR+/HER2- mBC from the phase I/II, single-arm trial (NCT01631552), who received intravenous SG (10 mg/kg) and whose disease progressed on endocrine-based therapy and at least one prior chemotherapy for mBC. End points included objective response rate (ORR; RECIST version 1.1) assessed locally, duration of response (DOR), clinical benefit rate, progression-free survival (PFS), overall survival (OS), and safety.

RESULTS

Fifty-four women were enrolled between 13 February 2015 and 1 June 2017. Median (range) age was 54 (33-79) years and all received at least two prior lines of therapy for mBC. At data cut-off (1 March 2019), 12 patients were still alive. Key grade ≥3 treatment-related toxicities included neutropenia (50.0%), anemia (11.1%), and diarrhea (7.4%). Two patients discontinued treatment due to treatment-related adverse events. No treatment-related deaths occurred. At a median follow-up of 11.5 months, the ORR was 31.5% [95% confidence interval (CI), 19.5%-45.6%; 17 partial responses]; median DOR was 8.7 months (95% CI 3.7-12.7), median PFS was 5.5 months (95% CI 3.6-7.6), and median OS was 12 months (95% CI 9.0-18.2).

CONCLUSIONS

SG shows encouraging activity in patients with pretreated HR+/HER2- mBC and a predictable, manageable safety profile. Further evaluation in a randomized phase III trial (TROPiCS-02) is ongoing (NCT03901339).

TRIAL REGISTRATION

ClinicalTrials.gov NCT01631552; https://clinicaltrials.gov/ct2/show/NCT01631552.

Antibody-Drug Conjugates: The New Frontier of Chemotherapy

In recent years, antibody-drug conjugates (ADCs) have become promising antitumor agents to be used as one of the tools in personalized cancer medicine. ADCs are comprised of a drug with cytotoxic activity cross-linked to a monoclonal antibody, targeting antigens expressed at higher levels on tumor cells than on normal cells. By providing a selective targeting mechanism for cytotoxic drugs, ADCs improve the therapeutic index in clinical practice. In this review, the chemistry of ADC linker conjugation together with strategies adopted to improve antibody tolerability (by reducing antigenicity) are examined, with particular attention to ADCs approved by the regulatory agencies (the U.S. Food and Drug Administration (FDA) and the European Medicines Agency (EMA)) for treating cancer patients. Recent developments in engineering Immunoglobulin (Ig) genes and antibody humanization have greatly reduced some of the problems of the first generation of ADCs, beset by problems, such as random coupling of the payload and immunogenicity of the antibody. ADC development and clinical use is a fast, evolving area, and will likely prove an important modality for the treatment of cancer in the near future.

Loss of BAP1 expression is associated with an immunosuppressive microenvironment in uveal melanoma, with implications for immunotherapy development

Immunotherapy using immune checkpoint inhibitors (ICIs) induces durable responses in many metastatic cancers. Metastatic uveal melanoma (mUM), typically occurring in the liver, is one of the most refractory tumours to ICIs and has dismal outcomes. Monosomy 3 (M3), polysomy 8q, and BAP1 loss in primary uveal melanoma (pUM) are associated with poor prognoses. The presence of tumour‐infiltrating lymphocytes (TILs) within pUM and surrounding mUM – and some evidence of clinical responses to adoptive TIL transfer – strongly suggests that UMs are indeed immunogenic despite their low mutational burden. The mechanisms that suppress TILs in pUM and mUM are unknown. We show that BAP1 loss is correlated with upregulation of several genes associated with suppressive immune responses, some of which build an immune suppressive axis, including HLA‐DR, CD38, and CD74. Further, single‐cell analysis of pUM by mass cytometry confirmed the expression of these and other markers revealing important functions of infiltrating immune cells in UM, most being regulatory CD8⁺ T lymphocytes and tumour‐associated macrophages (TAMs). Transcriptomic analysis of hepatic mUM revealed similar immune profiles to pUM with BAP1 loss, including the expression of IDO1. At the protein level, we observed TAMs and TILs entrapped within peritumoural fibrotic areas surrounding mUM, with increased expression of IDO1, PD‐L1, and β‐catenin (CTNNB1), suggesting tumour‐driven immune exclusion and hence the immunotherapy resistance. These findings aid the understanding of how the immune response is organised in BAP1⁻ mUM, which will further enable functional validation of detected biomarkers and the development of focused immunotherapeutic approaches. © 2020 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Sacituzumab govitecan, a novel, third-generation, antibody-drug conjugate (ADC) for cancer therapy

INTRODUCTION

We describe a new, third-generation of antibody-drug conjugates (ADCs) having a high drug payload against topoisomerase I, important for DNA function, and targeting selective tumor antigens, predominantly TROP-2.

AREAS COVERED

The historical development of ADCs is reviewed before presenting the current line of improved, third-generation ADCs targeting topoisomerase I, thus affecting DNA and causing double-stranded DNA breaks. Emphasis is given to explaining why sacituzumab govitecan represents a paradigm change in ADCs by achieving a high therapeutic index due to its novel target, TROP-2, an internalizing antigen/antibody, proprietary linker chemistry, and high drug payload, resulting in a high tumor concentration of the drug given in repeated doses with acceptable tolerability, particularly evidencing a lower percentage of 'late' diarrhea than its prodrug, irinotecan. PubMed was used for the primary search conducted.

EXPERT OPINION

The properties and clinical results of third-generation ADCs, based on sacituzumab govitecan, are discussed, including prospects for future applications, particularly combination therapies with PARP inhibitors and immune checkpoint inhibitors. Since one topoisomerase I ADC has just received regulatory approval for HER2⁺ breast cancer, and sacituzumab govitecan is under FDA review for accelerated approval in the therapy of triple-negative breast cancer, the prospects for these novel ADCs are discussed.

Antibody-based immunotherapy for treatment of immunoglobulin light-chain amyloidosis

Immunoglobulin light-chain (AL) amyloidosis is a clonal plasma cell disorder characterised by production and deposition of misfolded monoclonal light chains in vital organs with potential to cause irreversible organ damage. The treatment of AL amyloidosis has evolved along the lines of multiple myeloma (MM) owing to clonal plasma cells being at the root of both disease processes. Treatment with melphalan and autologous haematopoietic cell transplantation, as well as proteasome inhibitors and immunomodulatory agents, are the standard of care for AL amyloidosis. While these treatment modalities are highly effective against the neoplastic plasma cells, patients often relapse and those with advanced disease may be unable to tolerate these treatments due to side-effects. Immunotherapy with monoclonal antibodies, bispecific antibodies, antibody-drug conjugates and chimeric antigen receptor T cells have revolutionised the treatment armamentarium for MM. These novel immunotherapy agents are in the early phases of evaluation and clinical development for patients with AL amyloidosis. The present review aims to discuss the role of novel immunotherapies currently in development and their potential for use in the treatment of AL amyloidosis.

Fast Cyclization of a Proline-Derived Self-Immolative Spacer Improves the Efficacy of Carbamate Prodrugs

Self-immolative (SI) spacers are sophisticated chemical constructs designed for molecular delivery or material degradation. We describe herein a (S)-2-(aminomethyl)pyrrolidine SI spacer that is able to release different types of anticancer drugs (possessing either a phenolic or secondary and tertiary hydroxyl groups) through a fast cyclization mechanism involving carbamate cleavage. The high efficiency of drug release obtained with this spacer was found to be beneficial for the in vitro cytotoxic activity of protease-sensitive prodrugs, compared with a commonly used spacer of the same class. These findings expand the repertoire of degradation machineries and are instrumental for the future development of highly efficient delivery platforms.

ADCs, as Novel Revolutionary Weapons for Providing a Step Forward in Targeted Therapy of Malignancies

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Antibody drug conjugates (ADCs), as potent pharmaceutical trojan horses for cancer treatment, provide superior efficacy and specific targeting along with low risk of adverse reactions compared to traditional chemotherapeutics. In fact, the development of these agents combines the selective targeting capability of monoclonal antibody (mAb) with high cytotoxicity of chemotherapeutics for controlling the neoplastic mass growth. Different ADCs (more than 60 ADCs) in preclinical and clinical trials were introduced in this novel pharmaceutical field. Various design-based factors must be taken into account for improving the functionality of ADC technology, including selection of appropriate target antigen and high binding affinity of fragment (miniaturized ADCs) or full mAbs (preferentially use of humanized or fully human antibodies compared to murine and chimeric ones), use of bispecific antibodies for dual targeting effect, linker engineering and conjugation method efficacy to obtain more controlled drug to antibody ratio (DAR). Challenging issues affecting therapeutic efficacy and safety of ADCs, including bystander effect, on- and off-target toxicities, multi drug resistance (MDR) are also addressed. 4 FDA-approved ADCs in the market, including ADCETRIS ®, MYLOTARG®, BESPONSA ®, KADCYLA®. The goal of the current review is to evaluate the key parameters affecting ADCs development.

Antibody Conjugates-Recent Advances and Future Innovations

Monoclonal antibodies have evolved from research tools to powerful therapeutics in the past 30 years. Clinical success rates of antibodies have exceeded expectations, resulting in heavy investment in biologics discovery and development in addition to traditional small molecules across the industry. However, protein therapeutics cannot drug targets intracellularly and are limited to soluble and cell-surface antigens. Tremendous strides have been made in antibody discovery, protein engineering, formulation, and delivery devices. These advances continue to push the boundaries of biologics to enable antibody conjugates to take advantage of the target specificity and long half-life from an antibody, while delivering highly potent small molecule drugs. While the "magic bullet" concept produced the first wave of antibody conjugates, these entities were met with limited clinical success. This review summarizes the advances and challenges in the field to date with emphasis on antibody conjugation, linker-payload chemistry, novel payload classes, absorption, distribution, metabolism, and excretion (ADME), and product developability. We discuss lessons learned in the development of oncology antibody conjugates and look towards future innovations enabling other therapeutic indications.

Antibody-drug conjugates in clinical trials for lymphoid malignancies and multiple myeloma

Antibody-drug conjugates (ADC) represent a distinct family of chemoimmunotherapy agents. ADCs are composed of monoclonal antibodies conjugated to cytotoxic payloads via specialized chemical linkers. ADCs therefore combine the immune therapy with targeted chemotherapy. Due to the distinct biomarkers associated with lymphocytes and plasma cells, ADCs have emerged as a promising treatment option for lymphoid malignancies and multiple myeloma. Several ADCs have been approved for clinical applications: brentuximab vedotin, inotuzumab ozogamicin, moxetumomab pasudotox, and polatuzumab vedotin. More novel ADCs are under clinical development. In this article, we summarized the general principles for ADC design, and updated novel ADCs under various stages of clinical trials for lymphoid malignancies and multiple myeloma.