Investigational Antibody–Drug Conjugates for Treatment of B-lineage Malignancies

Belantamab Mafodotin: From Clinical Trials Data to Real-Life Experiences

Despite the recent approval of novel immunotherapies, such as immunomodulatory drugs, proteasome inhibitors and anti-CD38 monoclonal antibodies, Multiple Myeloma (MM) remains incurable, and the acquisition of triple-refractoriness leads to really dismal outcomes in even earlier lines of therapy. More recently, innovative therapeutic strategies targeting B cell maturation antigen (BCMA), highly expressed on the plasma cell surface, are drawing different future landscapes in terms of effectiveness and outcomes. Belantamab Mafodotin, a first-in-class anti-BCMA antibody-drug conjugate, demonstrated good efficacy and safety profile in triple-refractory patients in the phase 2 DREAMM-2 trial, and it was approved for the treatment of MM triple-exposed patients with >4 prior lines of therapy. Here, starting from Belantamab Mafodotin clinical trials and also exploring combination studies and different schedules in order to improve its efficacy and toxicity, we focused on real-life experiences all over the world, which have confirmed clinical trial data and encourage further Belantamab Mafodotin investigations.

Antibody-drug conjugates for lymphoma patients: preclinical and clinical evidences

Antibody-drug conjugates (ADCs) are a recent, revolutionary approach for malignancies treatment, designed to provide superior efficacy and specific targeting of tumor cells, compared to systemic cytotoxic chemotherapy. Their structure combines highly potent anti-cancer drugs (payloads or warheads) and monoclonal antibodies (Abs), specific for a tumor-associated antigen, via a chemical linker. Because the sensitive targeting capabilities of monoclonal Abs allow the direct delivery of cytotoxic payloads to tumor cells, these agents leave healthy cells unharmed, reducing toxicity. Different ADCs have been approved by the US Food and Drug Administration (FDA) and the European Medicines Agency (EMA) for the treatment of a wide range of malignant conditions, both as monotherapy and in combination with chemotherapy, including for lymphoma patients. Over 100 ADCs are under preclinical and clinical investigation worldwide. This paper it provides an overview of approved and promising ADCs in clinical development for the treatment of lymphoma. Each component of the ADC design, their mechanism of action, and the highlights of their clinical development progress are discussed.

Nanocarriers as a Delivery Platform for Anticancer Treatment: Biological Limits and Perspectives in B-Cell Malignancies

Nanoparticle-based therapies have been proposed in oncology research using various delivery methods to increase selectivity toward tumor tissues. Enhanced drug delivery through nanoparticle-based therapies could improve anti-tumor efficacy and also prevent drug resistance. However, there are still problems to overcome, such as the main biological interactions of nanocarriers. Among the various nanostructures for drug delivery, drug delivery based on polymeric nanoparticles has numerous advantages for controlling the release of biological factors, such as the ability to add a selective targeting mechanism, controlled release, protection of administered drugs, and prolonging the circulation time in the body. In addition, the functionalization of nanoparticles helps to achieve the best possible outcome. One of the most promising applications for nanoparticle-based drug delivery is in the field of onco-hematology, where there are many already approved targeted therapies, such as immunotherapies with monoclonal antibodies targeting specific tumor-associated antigens; however, several patients have experienced relapsed or refractory disease. This review describes the major nanocarriers proposed as new treatments for hematologic cancer, describing the main biological interactions of these nanocarriers and the related limitations of their use as drug delivery strategies.

Multiple Myeloma Therapy: Emerging Trends and Challenges

Multiple myeloma (MM) is a complex hematologic malignancy characterized by the uncontrolled proliferation of clonal plasma cells in the bone marrow that secrete large amounts of immunoglobulins and other non-functional proteins. Despite decades of progress and several landmark therapeutic advancements, MM remains incurable in most cases. Standard of care frontline therapies have limited durable efficacy, with the majority of patients eventually relapsing, either early or later. Induced drug resistance via up-modulations of signaling cascades that circumvent the effect of drugs and the emergence of genetically heterogeneous sub-clones are the major causes of the relapsed-refractory state of MM. Cytopenias from cumulative treatment toxicity and disease refractoriness limit therapeutic options, hence creating an urgent need for innovative approaches effective against highly heterogeneous myeloma cell populations. Here, we present a comprehensive overview of the current and future treatment paradigm of MM, and highlight the gaps in therapeutic translations of recent advances in targeted therapy and immunotherapy. We also discuss the therapeutic potential of emerging preclinical research in multiple myeloma.

A Novel Anti-CD22 scFv.Bim Fusion Protein Effectively Induces Apoptosis in Malignant B cells and Promotes Cytotoxicity

CD22 is a B-cell surface antigen which is highly expressed in cancerous B-cell lineages. Anti-CD22 antibodies are currently under focus as promising biologics against hematologic B-cell malignancies. Herein, we introduce a novel active recombinant anti-CD22 scFv.Bim fusion protein for targeting this cancerous antigen. An expression cassette encoding anti-CD22 scFv.Bim fusion protein was expressed in Pichia pastoris. The binding ability, cytotoxicity, and apoptotic activity of the purified recombinant protein against CD22⁺ Raji cell line were assessed by flow cytometry, microscopy, and MTT assay. Using bioinformatics, the 3D structure of the fusion protein and its interaction with CD22 were assessed. The in vitro binding analysis by immunofluorescence microscopy and flow cytometry demonstrated the specific binding of scFv.Bim to CD22⁺ Raji cells but not to CD22^- Jurkat cells. MTT data and Annexin V/PI flow cytometry analysis confirmed the apoptotic activity of anti-CD22 scFv.Bim against Raji cells but not Jurkat cells. In silico analysis also revealed the satisfactory stereochemical quality of the 3D model and molecular interactions toward CD22. This novel recombinant anti-CD22 scFv.Bim fusion protein could successfully deliver the pro-apoptotic peptide, BIM, to the target cells and thus nominates it as a promising molecule in treating B-cell malignancies.

Melflufen for the treatment of multiple myeloma

INTRODUCTION

Melphalan flufenamide (melflufen) is a first-in-class peptide-drug conjugate that takes advantage of increased aminopeptidase activity inside tumor cells to rapidly release alkylating agents therein. Melflufen in combination with dexamethasone has been evaluated in multiple clinical trials in patients with relapsed/refractory multiple myeloma (MM).

AREAS COVERED

This profile covers the unique mechanism of action of melflufen, the preclinical results supporting its activity in cellular models of resistance to chemotherapy, its activity in animal models of MM, and the clinical pharmacokinetics of melflufen. Findings from clinical trials evaluating melflufen, including the pivotal phase II HORIZON study and the phase III OCEAN study, are discussed.

EXPERT OPINION

Although MM treatment has improved, patients with disease refractory to multiple standard-of-care drug classes face a dismal prognosis. Melflufen demonstrated efficacy and tolerability in select populations, with an initial approval in the United States in patients with ≥ four previous lines of therapy and triple-class-refractory MM. Results from the phase III OCEAN study - currently under discussion with regulatory agencies in the United States and Europe - are more complex and have been put into context herein. Lastly, melflufen provides a proof-of-concept for the utility of the peptide-drug conjugate platform in relapsed/refractory MM.

An update on novel multiple myeloma targets

Introduction: despite therapeutic progress, leading to a significant improvement of outcome, multiple myeloma (MM) remains a difficult to treat hematologic disease due to its biological heterogeneity and clinical complexity.

Areas covered: Treatment of patients refractory and resistant to all classes of agents used in newly diagnosed MM, is becoming a relevant problem for every hematologist. New generation immunotherapies, such as conjugated mAb, bispecific mAbs and CAR-T cells, targeting novel molecules as BCMA, have showed relevant results in very advanced MM. In the same setting, small molecules, such as selinexor and melflufen, also proved to be effective. We are currently waiting for the results of under evaluation personalized therapy, directed against specific gene mutations or signaling pathways, responsible for disease progression.

Expert Opinion: In the near future, many therapeutic strategies will become available for MM and the challenge will be to position each approach in order to cure, maintaining a good quality of life in these patients.

CD30+ Lymphoproliferative Disorders as Potential Candidates for CD30-Targeted Therapies

CONTEXT.—

In the early 1980s, a monoclonal antibody termed Ki-1 was developed against a cell line derived from a patient with Hodgkin lymphoma. This antibody detected a limited number of benign activated lymphocytes in lymphoid tissue, whereas in Hodgkin lymphoma it appeared to be nearly specific for Reed-Sternberg cells and their mononuclear variants. Subsequent studies showed that Ki-1 expression defined a new type of lymphoma that was later designated anaplastic large cell lymphoma with or without anaplastic large cell kinase expression/translocation. In the past 30 years, numerous new lymphoma entities have been defined, many of which are variably positive for CD30. Many virally transformed lymphoproliferative disorders are also frequently positive for CD30.

OBJECTIVE.—

To illustrate the broad spectrum of CD30+ hematologic malignancies and to provide an update of CD30-targeted therapies.

DATA SOURCES.—

Personal experiences and published works in PubMed.

CONCLUSIONS.—

Because of its low expression in normal tissue, CD30 was studied as a therapeutic target for many years. However, the first functional humanized antibody against CD30 was developed only about 10 years ago. Brentuximab vedotin is a humanized anti-CD30 antibody linked to a cytotoxin, and was approved by the US Food and Drug Administration in 2012 for treating refractory Hodgkin lymphoma and anaplastic large cell lymphoma. Since then, the list of Food and Drug Administration-approved CD30-targeted hematologic malignancies has grown. Recently, the therapies using tumor antigen-specific chimeric antigen receptor T cells targeting CD30 have incited a great deal of enthusiasm and are studied in clinical trials.

Enhancement of Gene Knockdown on CD22-Expressing Cells by Chemically Modified Glycan Ligand-siRNA Conjugates

Extrahepatic targeted delivery of oligonucleotides, such as small interfering RNA (siRNA) and antisense oligonucleotides (ASOs), is an attractive technology for the development of nucleic acid-based medicines. To target CD22-expressing B cells, several drug platforms have shown promise, including antibodies, antibody-drug conjugates, and nanoparticles, but to date CD22-targeted delivery of oligonucleotide therapeutics has not been reported. Here we report the uptake and enhancement of siRNA gene expression knockdown in CD22-expressing B cells using a chemically stabilized and modified CD22 glycan ligand-conjugated siRNA. This finding has the potential to broaden the use of siRNA technology, opening up novel therapeutic opportunities, and presents an innovative approach for targeted delivery of siRNAs to B cell lymphomas.

Antibody-drug conjugates: Resurgent anticancer agents with multi-targeted therapeutic potential

Antibody-drug conjugates (ADCs) constitute a relatively new group of anticancer agents, whose first appearance took place about two decades ago, but a renewed interest occurred in recent years, following the success of anti-cancer immunotherapy with monoclonal antibodies. Indeed, an ADC combines the selectivity of a monoclonal antibody with the cell killing properties of a chemotherapeutic agent (payload), joined together through an appropriate linker. The antibody moiety targets a specific cell surface antigen expressed by tumor cells and/or cells of the tumor microenvironment and acts as a carrier that delivers the cytotoxic payload within the tumor mass. Despite advantages in terms of selectivity and potency, the development of ADCs is not devoid of challenges, due to: i) low tumor selectivity when the target antigens are not exclusively expressed by cancer cells; ii) premature release of the cytotoxic drug into the bloodstream as a consequence of linker instability; iii) development of tumor resistance mechanisms to the payload. All these factors may result in lack of efficacy and/or in no safety improvement compared to unconjugated cytotoxic agents. Nevertheless, the development of antibodies engineered to remain inert until activated in the tumor (e.g., antibodies activated proteolytically after internalization or by the acidic conditions of the tumor microenvironment) together with the discovery of innovative targets and cytotoxic or immunomodulatory payloads, have allowed the design of next-generation ADCs that are expected to possess improved therapeutic properties. This review provides an overview of approved ADCs, with related advantages and limitations, and of novel targets exploited by ADCs that are presently under clinical investigation.

A homogeneous high-DAR antibody-drug conjugate platform combining THIOMAB antibodies and XTEN polypeptides

The antibody-drug conjugate (ADC) is a well-validated modality for the cell-specific delivery of small molecules with impact expanding rapidly beyond their originally-intended purpose of treating cancer. However, antibody-mediated delivery (AMD)...

Promising Immunotherapeutic Modalities for B-Cell Lymphoproliferative Disorders

Over the last few years, treatment principles have been changed towards more targeted therapy for many B-cell lymphoma subtypes and in chronic lymphocytic leukemia (CLL). Immunotherapeutic modalities, namely monoclonal antibodies (mAbs), bispecific antibodies (bsAbs), antibody-drug conjugates (ADCs), and chimeric antigen receptor T (CAR-T) cell therapy, commonly use B-cell-associated antigens (CD19, CD20, CD22, and CD79b) as one of their targets. T-cell engagers (TCEs), a subclass of bsAbs, work on a similar mechanism as CAR-T cell therapy without the need of previous T-cell manipulation. Currently, several anti-CD20xCD3 TCEs have demonstrated promising efficacy across different lymphoma subtypes with slightly better outcomes in the indolent subset. Anti-CD19xCD3 TCEs are being developed as well but only blinatumomab has been evaluated in clinical trials yet. The results are not so impressive as those with anti-CD19 CAR-T cell therapy. Antibody-drug conjugates targeting different B-cell antigens (CD30, CD79b, CD19) seem to be effective in combination with mAbs, standard chemoimmunotherapy, or immune checkpoint inhibitors. Further investigation will show whether immunotherapy alone or in combinatory regimens has potential to replace chemotherapeutic agents from the first line treatment.

Belantamab Mafodotin for the Treatment of Multiple Myeloma: An Overview of the Clinical Efficacy and Safety

Despite the introduction of immunomodulatory drugs (IMiDs), proteasome inhibitors (PIs), and, more recently, monoclonal antibodies (mAbs), in the chemotherapy regimens for newly diagnosed (NDMM) and relapsed/refractory MM (RRMM), the occurrence of drug resistance remains a challenge in MM patients. This is mainly in the advanced stage of the disease when treatments are limited, and the prognosis is abysmal. Nevertheless, novel molecules and therapeutic approaches are rapidly moving through the several phases of drug development and could address the need for new treatment options. The recent innovative B-cell maturation antigen (BCMA) targeted immunotherapies, such as belantamab mafodotin, the first-in-class monoclonal antibody-drug conjugate (ADC), induce an effective and durable response in triple-class refractory disease and to be approved in MM. In contrast with the other BCMA-targeted therapies as CAR T cells with a complex manufacturing process, and bispecific antibodies, both requiring inpatient hospitalization to monitor the occurrence of severe adverse events, belantamab mafodotin is an “off-the-shelf” drug that can be administered in an outpatient setting. Many belantamab mafodotin-based combinations are under evaluation in Phase I, II, and III clinical trials either late or in early RRMM patients. Ocular toxicity represents a peculiar side effect of belantamab mafodotin. This toxicity is generally manageable with adequate dose reductions or delays since most patients who developed keratopathy recovered on treatment and discontinued ADC are rare. Here, we described the most recent clinical data of belantamab mafodotin and discussed the possible leading role of this intriguing agent in the near future of MM treatment.

CD70 antibody-drug conjugate as a potential therapeutic agent for uterine leiomyosarcoma

BACKGROUND

Uterine leiomyosarcoma is a rare and aggressive gynecologic malignancy originating in the myometrium of the uterine corpus that tends to recur even after complete surgical excision. Current therapeutic agents have only modest effects on uterine leiomyosarcoma. Although antibodies and antibody-drug conjugates have been recognized as useful targeted therapies for other cancers, no study has yet evaluated the effects of this approach on uterine leiomyosarcoma.

OBJECTIVE

This study aimed to examine the activity of tumoral CD70 in uterine leiomyosarcoma and assess the antitumor activity of CD70-antibody-drug conjugate treatment in uterine leiomyosarcoma.

STUDY DESIGN

Target membrane proteins were screened by profiling and comparing membrane protein expression in 3 uterine leiomyosarcoma cell lines (SK-UT-1, SK-LMS-1, and SKN) and normal uterine myometrium cells using the isobaric tags for relative and absolute quantitation labeling method. Western blotting, fluorescence-activated cell sorting analyses, and immunohistochemistry were used to examine CD70 expression in the membrane proteins in uterine leiomyosarcoma cell lines and clinical samples. We developed an antibody-drug conjugate with a monoclonal antibody of the target membrane protein linked to monomethyl auristatin F and investigated its antitumor effects against uterine leiomyosarcoma (in vitro, in vivo, and in patient-derived xenograft models).

RESULTS

CD70 was identified as a specific antigen highly expressed in uterine leiomyosarcoma cell lines. Of the 3 uterine leiomyosarcoma cell lines, CD70 expression was confirmed in SK-LMS-1 cells by western blotting and fluorescence-activated cell sorting analysis. CD70 overexpression was observed in 19 of 21 (90.5%) tumor specimens from women with uterine leiomyosarcoma. To generate CD70-antibody-drug conjugate, anti-CD70 monoclonal antibody was conjugated with a novel derivative of monomethyl auristatin F. CD70-antibody-drug conjugate showed significant antitumor effects on SK-LMS-1 cells (half maximal inhibitory concentration, 0.120 nM) and no antitumor effects on CD70-negative uterine leiomyosarcoma cells. CD70-antibody-drug conjugate significantly inhibited tumor growth in the SK-LMS-1 xenograft mouse model (tumor volume, 129.8 vs 285.5 mm³; relative reduction, 54.5%; P<.001) and patient-derived xenograft mouse model (tumor volume, 128.1 vs 837.7 mm³; relative reduction, 84.7%; P<.001).

CONCLUSION

Uterine leiomyosarcoma tumors highly express CD70 and targeted therapy with CD70-antibody-drug conjugate may have a potential therapeutic implication in the treatment of uterine leiomyosarcoma.

Safety and pharmacokinetics of polatuzumab vedotin in Japanese patients with relapsed/refractory B-cell non-Hodgkin lymphoma: a phase 1 dose-escalation study

Objective

A phase 1 dose-escalation study of polatuzumab vedotin (pola) was conducted to assess safety, pharmacokinetics and preliminary antitumor activity of pola in Japanese patients with relapsed/refractory B-cell non-Hodgkin lymphoma.

Methods

Patients received pola (1.0 or 1.8 mg/kg) intravenously every 21 days until disease progression or intolerance. Intra-patient dose escalation was prohibited. Tolerability was determined by the standard 3 + 3 rule. Blood sampling was performed to characterize pharmacokinetics. Antitumor activity was evaluated through computed tomography and bone marrow sampling.

Results

Four patients received pola 1.0 mg/kg; three received 1.8 mg/kg. Patients had follicular lymphoma (n = 4) or diffuse large B-cell lymphoma (n = 3), median age of 62 years, received a median of 3 prior therapies; six were female. Pola was well tolerated in both cohorts, with no dose-limiting toxicities observed. The most common adverse event was peripheral sensory neuropathy (n = 4). Grade 3 adverse events were cholecystitis and neutrophil count decreased (one each; both 1.0 mg/kg), and syncope and cataract (one each; both 1.8 mg/kg). The plasma half-life of antibody-conjugate monomethyl auristatin E was 4.43–7.98 days, and systemic exposure of unconjugated monomethyl auristatin E was limited in both cohorts. Four patients achieved objective responses (three complete, one partial) without disease progression during the study.

Conclusions

This phase 1 dose-escalation study demonstrated that pola has an acceptable safety profile and offers encouraging antitumor activity to Japanese patients with relapsed/refractory B-cell non-Hodgkin lymphoma. Pola 1.8 mg/kg, the recommended phase 2 dose, was tolerable in Japanese patients.

Drug Conjugated and Bispecific Antibodies for Multiple Myeloma: Improving Immunotherapies off the Shelf

The impressive improvement of overall survival in multiple myeloma (MM) patients in the last years has been mostly related to the availability of new classes of drugs with different mechanisms of action, including proteasome inhibitors (PI), immunomodulating agents (IMiDs), and monoclonal antibodies. However, even with this increased potence of fire, MM still remains an incurable condition, due to clonal selection and evolution of neoplastic clone. This concept underlines the importance of immunotherapy as one of the most relevant tools to try to eradicate the disease. In line with this concept, active and passive immunotherapies represent the most attractive approach to this aim. Antibody-drug conjugate(s) (ADCs) and bispecific antibodies (BsAbs) include two innovative tools in order to limit neoplastic plasma cell growth or even, if used at the time of the best response, to potentially eradicate the tumoral clone. Following their promising results as single agent for advanced disease, at the recent 62nd ASH meeting, encouraging data of several combinations, particularly of ADC(s) with PI or IMiDs, have been reported, suggesting even better results for patients treated earlier. In this paper, we reviewed the characteristics, mechanism of action, and clinical data available for most relevant ADC(s) and BsAbs.

Antibody-drug conjugates for previously treated aggressive lymphomas: focus on polatuzumab vedotin

INTRODUCTION

Antibody-drug conjugates (ADCs) are immunoconjugates and comprise a monoclonal antibody that is chemically attached to a cytotoxic drug (or payload) via a stable chemical linker. Since the approval of the first ADC in 2000, there are now nine different approved agents and over 100 ADCs in the drug-development pipeline.

AREAS COVERED

This review briefly describes the ADCs approved for treatment of lymphoma and their distinguishing factors in terms of target, linker and payload. The clinical implications of the use of ADCs are also considered. Here, we focus on polatuzumab vedotin, an ADC targeted to CD79b, which is approved for the treatment of patients with relapsed/refractory diffuse large B-cell lymphoma (R/R DLBCL) who have received at least one (EU approval) or two (US approval) prior therapies and are not eligible for bone marrow transplantation. The characteristics of polatuzumab vedotin are discussed and clinical data are presented. The future of polatuzumab vedotin clinical development, and ADCs in general, are also considered.

EXPERT OPINION

ADCs represent a significant advance in the treatment of lymphoma. Polatuzumab vedotin has shown clinical efficacy and a tolerable safety profile in both first-line and R/R DLBCL; future studies are planned to further investigate this ADC.

Polatuzumab vedotin, an anti-CD79b antibody-drug conjugate for the treatment of relapsed/refractory diffuse large B-cell lymphoma

Refractory/relapsed diffuse large B-cell lymphoma remains a major unmet medical need with poor outcome, especially for patients considered ineligible for stem cell transplant. Polatuzumab vedotin (PV) is a first-in-class anti-CD79b antibody-drug conjugate that contains the microtubule inhibitor monomethyl auristatin E. The development of PV is currently very active. This drug was US FDA approved in 2019 in combination with bendamustine and rituximab for the treatment of refractory/relapsed diffuse large B-cell lymphoma in third line and more, after demonstrating relevant efficacy and acceptable safety in a pivotal randomized Phase II trial. This review summarizes the features of this new drug with the primary focus on the clinical work supporting efficacy, relevance and tolerability of PV.

BCMA-targeted immunotherapy for multiple myeloma

B cell maturation antigen (BCMA) is a novel treatment target for multiple myeloma (MM) due to its highly selective expression in malignant plasma cells (PCs). Multiple BCMA-targeted therapeutics, including antibody-drug conjugates (ADC), chimeric antigen receptor (CAR)-T cells, and bispecific T cell engagers (BiTE), have achieved remarkable clinical response in patients with relapsed and refractory MM. Belantamab mafodotin-blmf (GSK2857916), a BCMA-targeted ADC, has just been approved for highly refractory MM. In this article, we summarized the molecular and physiological properties of BCMA as well as BCMA-targeted immunotherapeutic agents in different stages of clinical development.

Antibody-drug conjugates for multiple myeloma

Introduction: Antibody-drug conjugates (ADC) are a new class of treatment for multiple myeloma (MM) patients, delivering a potent cytotoxic agent directly to the myeloma cell. The target is defined by the specificity of the monoclonal antibody which is linked to the cytotoxic agent. This mechanism of action minimizes bystander cell injury and allows a favorable therapeutic window.Areas covered: This review describes the rationale, pre- and clinical data for ADCs that have been and are currently in development for MM. As the treatment landscape for MM rapidly evolves, the treatment paradigm and a description of novel agents in development including immunotherapies are provided to understand how ADCs may fit in the pathway.Expert opinion: ADCs have a significant potential for the treatment for MM. As they are 'off the shelf' treatments, they can be used across nearly all MM treatment centers and to a wide range of patients. Some ADCs have specific adverse events that may require specialist input to optimally manage. The most clinically advanced ADC is belantamab mafodotin which has demonstrated clinically meaningful responses in patients with heavily pre-treated MM. Additionally, it is being combined with standard of care agents and at earlier lines of treatment.

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.

Pharmacokinetics of polatuzumab vedotin in combination with R/G-CHP in patients with B-cell non-Hodgkin lymphoma

Purpose

The phase Ib/II open-label study (NCT01992653) evaluated the antibody-drug conjugate polatuzumab vedotin (pola) plus rituximab/obinutuzumab, cyclophosphamide, doxorubicin, and prednisone (R/G-CHP) as first-line therapy for B-cell non-Hodgkin lymphoma (B-NHL). We report the pharmacokinetics (PK) and drug–drug interaction (DDI) for pola.

Methods

Six or eight cycles of pola 1.0–1.8 mg/kg were administered intravenously every 3 weeks (q3w) with R/G-CHP. Exposures of pola [including antibody-conjugated monomethyl auristatin E (acMMAE) and unconjugated MMAE] and R/G-CHP were assessed by non-compartmental analysis and/or descriptive statistics with cross-cycle comparisons to cycle 1 and/or after multiple cycles. Pola was evaluated as a potential victim and perpetrator of a PK drug–drug interaction with R/G-CHP. Population PK (popPK) analysis assessed the impact of prior treatment status (naïve vs. relapsed/refractory) on pola PK.

Results

Pola PK was similar between treatment arms and independent of line of therapy. Pola PK was dose proportional from 1.0 to 1.8 mg/kg with R/G-CHP. Geometric mean volume of distribution and clearance of acMMAE ranged from 57.3 to 95.6 mL/kg and 12.7 to 18.2 mL/kg/day, respectively. acMMAE exhibited multi-exponential decay (elimination half-life ~ 1 week). Unconjugated MMAE exhibited formation rate-limited kinetics. Exposures of pola with R/G-CHP were similar to those in the absence of CHP; exposures of R/G-CHP in the presence of pola were comparable to those in the absence of pola.

Conclusions

Pola PK was well characterized with no clinically meaningful DDIs with R/G-CHP. Findings are consistent with previous studies of pola + R/G, and support pola + R/G-CHP use in previously untreated diffuse large B-cell lymphoma.

Electronic supplementary material

The online version of this article (10.1007/s00280-020-04054-8) contains supplementary material, which is available to authorized users.

Monoclonal antibodies in multiple myeloma: Current and emerging targets and mechanisms of action

The recent development of monoclonal antibodies (mAbs) has revolutionized the treatment armamentarium for multiple myeloma. The success of daratumumab and elotuzumab in relapsed/refractory patients, has generated tremendous enthusiasm for mAbs in this disease. Combination treatment with other anti-myeloma treatment modalities and clinical evaluation in newly diagnosed patients are expected to fundamentally change the natural history of the disease. Advances in biopharmaceutical engineering together with a robust interest in novel mAb-derivatives, including antibody drug conjugates and poly-specific antibodies are the next rapidly approaching treatment frontier in multiple myeloma. In this review, we comprehensively outline the currently available evidence and the future landscape of mAbs and mAb-derivative therapies in multiple myeloma.

Differential Expression of CD43, CD81, and CD200 in Classic Versus Variant Hairy Cell Leukemia

BACKGROUND

Hairy cell leukemia (HCL) and hairy cell leukemia variant (HCLv) are rare diseases with overlapping clinicopathological features. Features distinguishing HCL from HCLv include expression of CD25, CD123, CD200, annexin-A1, and the presence of BRAF V600E mutation. HCLv typically lacks these markers, but they may occur in a subgroup of HCL patients with an aggressive clinical course. We examined CD43, CD81, CD79b, and CD200 expression in HCL and HCLv.

METHODS

Multiparametric flow cytometry (FCM) was performed on blood from 59 HCL and 15 HCLv patients for protocol entry. Mean fluorescent intensity (MFI) of CD43, CD79b, CD81, and CD200 was determined (for CD200, n = 17 and 7, respectively).

RESULTS

Median MFI of HCL vs HCLv was 545 vs 272 for CD43, 602 vs 2,450 for CD81, 4,962 vs 1,969 for CD79b, and 11,652 vs 1,405 for CD200, respectively. Analysis of the median differences, HCL minus HCLv (and their 95% confidence intervals and P-values) indicated that CD43 MFI (estimated median difference (95% CI): 212 [72-413; P = 0.0027) and CD200 MFI (9,883 [3,514-13,434]; P < 0.0001) were higher in HCL than in HCLv, while CD81 MFI (-1,858 [-2,604 to -1,365]; P < 0.0001) was lower in HCL than in HCLv. CD79b MFI HCL median was more than double that of HCLv, but the observed difference (1,571 [-739 to 4,417]) was consistent with the null hypothesis of no difference (P = 0.13).

CONCLUSIONS

CD200, CD43, and CD81 are likely differentially expressed between HCL and HCLv, reflecting their differing disease biology. Inclusion of these markers in FCM is potentially informative. © 2019 International Clinical Cytometry Society.

Glycoengineering of Antibodies for Modulating Functions

Antibodies are immunoglobulins that play essential roles in immune systems. All antibodies are glycoproteins that carry at least one or more conserved N-linked oligosaccharides (N-glycans) at the Fc domain. Many studies have demonstrated that both the presence and fine structures of the attached glycans can exert a profound impact on the biological functions and therapeutic efficacy of antibodies. However, antibodies usually exist as mixtures of heterogeneous glycoforms that are difficult to separate in pure glycoforms. Recent progress in glycoengineering has provided useful methods that enable production of glycan-defined and site-selectively modified antibodies for functional studies and for improved therapeutic efficacy. This review highlights major approaches in glycoengineering of antibodies with a focus on recent advances in three areas: glycoengineering through glycan biosynthetic pathway manipulation, glycoengineering through in vitro chemoenzymatic glycan remodeling, and glycoengineering of antibodies for site-specific antibody-drug conjugation.

Targeting CD74 in multiple myeloma with the novel, site-specific antibody-drug conjugate STRO-001

STRO-001 is a site-specific, predominantly single-species, fully human, aglycosylated anti-CD74 antibody-drug conjugate incorporating a non-cleavable linker-maytansinoid warhead with a drug-antibody ratio of 2 which was produced by a novel cell-free antibody synthesis platform. We examined the potential pharmacodynamics and anti-tumor effects of STRO-001 in multiple myeloma (MM). CD74 expression was assessed in MM cell lines and primary bone marrow (BM) MM biopsies. CD74 mRNA was detectable in CD138+ enriched plasma cells from 100% (892/892) of patients with newly diagnosed MM. Immunohistochemistry confirmed CD74 expression in 35/36 BM biopsies from patients with newly diagnosed and relapsed/refractory MM. Cytotoxicity assays demonstrated nanomolar STRO-001 potency in 4/6 MM cell lines. In ARP-1 and MM.1S tumor-bearing mice, repeat STRO-001 dosing provided significant antitumor activity with eradication of malignant hCD138+ BM plasma cells and prolonged survival. In a luciferase-expressing MM.1S xenograft model, dose-dependent STRO-001 efficacy was confirmed using bioluminescent imaging and BM tumor burden quantification. Consistent with the intended pharmacodynamic effect, STRO-001 induced dose-responsive, reversible B-cell and monocyte depletion in cynomolgus monkeys, up to a maximum tolerated 10 mg/kg, with no evidence of off-target toxicity. Collectively, these data suggest that STRO-001 is a promising therapeutic agent for the treatment of MM.