Ocular Adverse Events Associated with Antibody-Drug Conjugates in Human Clinical Trials

Pharmacokinetics of Monoclonal Antibody and Antibody Fragments in the Mouse Eye Following Systemic Administration

The ocular pharmacokinetics (PK) of antibody-based therapies are infrequently studied in mice due to the technical difficulties in working with the small murine eye. This study is the first of its kind to quantitatively measure the PK of variously sized proteins in the plasma, cornea/ICB, vitreous humor, retina, and posterior cup (including choroid) of the mouse and to evaluate the relationship between molecular weight (MW) and antibody biodistribution coefficient (BC) to the eye. Proteins analyzed include trastuzumab (150 kDa), trastuzumab-vc-MMAE (T-vc-MMAE, 155 kDa), F(ab)₂ (100 kDa), Fab (50 kDa), and scFv (27 kDa). As expected, ocular PK mirrored the systemic PK as plasma was the driving force for ocular exposure. For trastuzumab, T-vc-MMAE, F(ab)₂, Fab, and scFv, respectively, the BCs in the cornea/ICB were 0.610%, 0.475%, 1.74%, 3.39%, and 13.7%; the BCs in the vitreous humor were 0.0198%, 0.0427%, 0.0934%, 0.234%, and 5.56%; the BCs for the retina were 0.539%, 0.230%, 0.704%, 2.44%, and 20.4%; the BCs for the posterior cup were 0.557%, 0.650%, 1.47%, 4.06%, and 13.9%. The relationship between BC and MW was best characterized by a log–log regression in which BC decreased as MW increased, with every doubling in MW leading to a decrease in BC by a factor of 3.44 × , 6.76 × , 4.74 × , and 3.43 × in cornea/ICB, vitreous humor, retina, and posterior cup, respectively. In analyzing the disposition of protein therapeutics to the eye, these findings enhance our understanding of the potential for ocular toxicity of systemically administered protein therapeutics and may aid in the discovery of systemically administered protein therapeutics for ocular disorders.

DREAMM-2: Indirect Comparisons of Belantamab Mafodotin vs. Selinexor + Dexamethasone and Standard of Care Treatments in Relapsed/Refractory Multiple Myeloma

Introduction

Single-agent belantamab mafodotin (belamaf; BLENREP) demonstrated deep and durable responses in patients with relapsed/refractory multiple myeloma and ≥ 3 prior lines of therapy, including an immunomodulatory agent, proteasome inhibitor, and anti-CD38 antibody (DREAMM-2; NCT03525678).

Methods

At the time of this study, STORM Part 2, NCT02336815 (selinexor plus low-dose dexamethasone; sel + dex) was systematically identified as the only feasible comparator to the DREAMM-2 cohort. Matching-adjusted indirect comparisons (MAIC) evaluated efficacy and safety of belamaf (2.5 mg/kg; n = 97) versus sel + dex (80 mg + 20 mg, respectively; n = 123). Populations were weighted for clinically validated effect modifiers and prognostic factors. Outcomes included overall survival (OS), progression-free survival (PFS), duration of response (DoR), overall response rate (ORR), time to response (TTR), and safety. The relative efficacy of belamaf versus standard of care (SoC) on OS was estimated by a Bucher indirect treatment comparison using the MAIC-adjusted hazard ratios (HR) for OS of belamaf (DREAMM-2) versus sel + dex (STORM Part 2) and a HR adjusted for refractoriness to carfilzomib and high-risk cytogenetics of sel + dex (STORM) versus SoC (MAMMOTH).

Results

Belamaf demonstrated improved OS (HR 0.53; 95% confidence interval 0.34, 0.83; p = 0.005) and DoR (0.41; 0.21, 0.83; p = 0.013) versus sel + dex. There were no statistically significant differences in ORR, TTR, and PFS. Belamaf had a favorable safety profile for most evaluable hematologic (any-grade, Grade 3–4) and non-hematologic (any-grade) adverse events versus sel + dex. Significantly improved OS was observed with belamaf versus SoC (0.29; 0.16, 0.54; p < 0.001).

Conclusion

Single-agent belamaf represents a new treatment option for triple-class refractory patients with RRMM.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12325-021-01884-7.

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.

Safety and efficacy of depatuxizumab mafodotin in Japanese patients with malignant glioma: A nonrandomized, phase 1/2 trial

INTELLANCE‐J was a phase 1/2 study of a potent antibody‐drug conjugate targeting epidermal growth factor receptor (EGFR), depatuxizumab mafodotin (Depatux‐M), as a second‐ or first‐line therapy, alone or combined with chemotherapy or chemoradiotherapy in 53 Japanese patients with World Health Organization (WHO) grade III/IV glioma. In second‐line arms, patients with EGFR‐amplified recurrent WHO grade III/IV glioma received Depatux‐M plus chemotherapy (temozolomide) or Depatux‐M alone regardless of EGFR status. In first‐line arms, patients with newly diagnosed WHO grade III/IV glioma received Depatux‐M plus chemoradiotherapy. The study was halted following lack of survival benefit with first‐line Depatux‐M in the global trial INTELLANCE‐1. The primary endpoint was 6‐month progression‐free survival (PFS) in patients with EGFR‐amplified tumors receiving second‐line Depatux‐M plus chemotherapy. Common nonocular treatment‐emergent adverse events (TEAEs) with both second‐line and first‐line Depatux‐M included lymphopenia (42%, 33%, respectively), thrombocytopenia (39%, 47%), alanine aminotransferase increase (29%, 47%), and aspartate aminotransferase increase (24%, 60%); incidence of grade ≥3 TEAEs was 66% and 53%, respectively. Ocular side effects (OSEs) occurred in 93% of patients receiving second‐line Depatux‐M plus chemotherapy and all patients receiving second‐line Depatux‐M alone or first‐line Depatux‐M plus chemoradiotherapy. Most OSEs were manageable with dose modifications and concomitant medications. The 6‐month PFS estimate was 25.6% (95% confidence interval [CI] 11.4‒42.6), and median PFS was 2.1 months (95% CI 1.9‒3.9) with second‐line Depatux‐M plus chemotherapy in the EGFR‐amplified subgroup. This study showed acceptable safety profile of Depatux‐M alone or plus chemotherapy/chemoradiotherapy in Japanese patients with WHO grade III/IV glioma. The study was registered at ClinicalTrials.gov (NCT02590263).

Corneal in vivo confocal microscopy to detect belantamab mafodotin-induced ocular toxicity early and adjust the dose accordingly: a case report

Background

New targeted antibody–drug conjugates (ADCs) against multiple myeloma are known to induce adverse effects that may lead to treatment discontinuation. Preclinical studies reported early severe ocular damage related to the use of belantamab mafodotin (belamaf), including ocular surface inflammation, severe dry eye, and a specific toxicity to the cornea, namely microcystic keratopathy. While belamaf-induced ocular changes have not been prospectively studied, a better understanding of mechanisms involved as well as kinetics may aid in anticipating dose adjustment rather than stopping the treatment once clinical ocular damage is too severe.

Case presentation

A 61-year-old woman scheduled for belamaf as a fifth-line treatment against multiple myeloma was prospectively included. Clinical examinations were performed before and every 3 weeks afterward, together with in vivo confocal microscopy (IVCM) of the cornea. Visual acuity, symptoms, slit-lamp examination, and ultrastructural changes of the cornea were recorded according to the received dose of belamaf. More precisely, kinetics, shape, density, and location of the toxic corneal lesions have been followed and analyzed using IVCM. Also, specific lesions at the sub-basal nerve plexus layer were detected and characterized for the first time. This advanced approach allowed a better understanding of the belamaf-induced toxicity, further balancing the dose to maintain good vision and eye health while continuing the treatment.

Conclusions

Systematic ultrastructural analysis and follow-up of the corneal state during ADCs treatment for multiple myeloma may open new avenues in the therapeutic approach. Early preclinical detection of ocular damage may accurately contribute to finding the correct dose for each patient and not stopping the treatment due to severe ocular adverse effects.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13045-021-01172-5.

Keeping Myeloma in Check: The Past, Present and Future of Immunotherapy in Multiple Myeloma

Multiple myeloma is an incurable disease of malignant plasma cells and an ideal target for modern immune therapy. The unique plasma cell biology maintained in multiple myeloma, coupled with its hematological nature and unique bone marrow microenvironment, provide an opportunity to design specifically targeted immunotherapies that selectively kill transformed cells with limited on-target off-tumor effects. Broadly defined, immune therapy is the utilization of the immune system and immune agents to treat a disease. In the context of multiple myeloma, immune therapy can be subdivided into four main categories: immune modulatory imide drugs, targeted antibodies, adoptive cell transfer therapies, and vaccines. In recent years, advances in all four of these categories have led to improved therapies with enhanced antitumor activity and specificity. In IMiDs, modified chemical structures have been developed that improve drug potency while reducing dose limiting side effects. Targeted antibody therapies have resulted from the development of new selectively expressed targets as well as the development of antibody drug conjugates and bispecific antibodies. Adoptive cell therapies, particularly CAR-T therapies, have been enhanced through improvements in the manufacturing process, as well as through the development of CAR constructs that enhance CAR-T activation and provide protection from a suppressive immune microenvironment. This review will first cover in-class breakthrough therapies for each of these categories, as well as therapies currently utilized in the clinic. Additionally, this review will explore up and coming therapeutics in the preclinical and clinical trial stage.

The Agony of Choice-Where to Place the Wave of BCMA-Targeted Therapies in the Multiple Myeloma Treatment Puzzle in 2022 and Beyond

Simple Summary

There is no doubt that immunotherapeutic approaches will change the current treatment landscape of multiple myeloma in the near future; in particular, a wave of BCMA-targeted therapies is currently entering clinical routine. Although the increasing availability of different therapeutic approaches is highly welcome, it also increases the daily challenges in clinical decision making if they all use the same target. Here, we provide a comprehensive summary of BCMA-targeted approaches in myeloma and aim to share some basic concepts in clinical decision making.

Abstract

Since the introduction of first-generation proteasome inhibitors and immunomodulatory agents, the multiple myeloma (MM) treatment landscape has undergone a remarkable development. Most recently, immunotherapeutic strategies targeting the B cell maturation antigen (BCMA) entered the clinical stage providing access to highly anticipated novel treatment strategies. At present, numerous different approaches investigate BCMA as an effective multi-modal target. Currently, BCMA-directed antibody–drug conjugates, bispecific and trispecific antibodies, autologous and allogeneic CAR-T cell as well as CAR-NK cell constructs are either approved or in different stages of clinical and preclinical development for the treatment of MM. This armamentarium of treatment choices raises several challenges for clinical decision making, particularly in the absence of head-to-head comparisons. In this review, we provide a comprehensive overview of BCMA-targeting therapeutics, deliver latest updates on clinical trial data, and focus on potential patient selection criteria for different BCMA-targeting immunotherapeutic strategies.

A Phase 1 Study of a CDH6-Targeting Antibody-Drug Conjugate in Patients with Advanced Solid Tumors with Evaluation of Inflammatory and Neurological Adverse Events

PURPOSE

This first-in-human study (NCT02947152) evaluated the safety, tolerability, pharmacokinetics, and preliminary efficacy of HKT288, a first-in-class CDH6-targeting antibody-drug conjugate (ADC).

EXPERIMENTAL DESIGN

HKT288 was administered intravenously (IV) every 3 weeks until patients experienced unacceptable toxicity or progressive disease (PD). The starting dose of 0.3 mg/kg was determined based on the highest nonseverely toxic dose in monkeys, which was 2 mg/kg IV weekly. Based on preclinical toxicology, skin, eyes, bone marrow, and liver were expected targets of toxicity.

RESULTS

Nine patients were enrolled: 5 with renal cell carcinoma and 4 with epithelial ovarian cancer. The best overall response on the 0.3 mg/kg cohort in patients with measurable disease was RECIST v1.1 stable disease in 3 patients and PD in 2 patients. The most frequent adverse events (AEs) regardless of causality were pyrexia (44.4%), constipation (44.4%), fatigue (33.3%), and vomiting (33.3%). Three suspected-related neurologic AEs (Grade 2) were reported on the 0.75 mg/kg cohort: seizure in 1 patient and another patient with aphasia and encephalopathy. Further studies were unable to identify the underlying mechanism of the neurologic AEs, and the study was terminated early.

CONCLUSIONS

Preclinical toxicology did not predict the neurotoxicity observed with HKT288, and a comprehensive assessment performed post hoc did not identify the mechanism of toxicity. The development of further CDH6-targeting ADCs should be pursued with caution.

Immunotherapy of Multiple Myeloma: Promise and Challenges

Whereas the treatment of MM was dependent solely on alkylating agents and corticosteroids during the prior three decades, the landscape of therapeutic measures to treat the disease began to expand enormously early in the current century. The introduction of new classes of small-molecule drugs, such as proteasome blockers (bortezomib and carfilzomib), immunomodulators (lenalidomide and pomalidomide), nuclear export inhibitors (selinexor), and histone deacetylase blockers (panobinostat), as well as the application of autologous stem cell transplantation (ASCT), resulted in a seismic shift in how the disease is treated. The picture changed dramatically once again starting with the 2015 FDA approval of two monoclonal antibodies (mAbs) - the anti-CD38 daratumumab and the anti-SLAMF7 elotuzumab. Daratumumab, in particular, has had a great impact on MM therapy and today is often included in various regimens to treat the disease, both in newly diagnosed cases and in the relapse/refractory setting. Recently, other immunotherapies have been added to the arsenal of drugs available to fight this malignancy. These include isatuximab (also anti-CD38) and, in the past year, the antibody-drug conjugate (ADC) belantamab mafodotin and the chimeric antigen receptor (CAR) T-cell product idecabtagene vicleucel (ide-cel). While the accumulated benefits of these newer agents have resulted in a doubling of the disease's five-year survival rate to more than 5 years and improved quality of life, the disease remains incurable. Almost without exception patients experience relapse and/or become refractory to the drugs used, making the search for innovative therapies all the more essential. This review covers the current scope of anti-myeloma immunotherapeutic agents, both those in clinical use and on the horizon, including naked mAbs, ADCs, bi- and multi-targeted mAbs, and CAR T-cells. Emphasis is placed on the benefits of each along with the challenges that need to be overcome if MM is to be considered curable in the future.

Antibody-Drug Conjugate Efficacy in Neuroblastoma: Role of Payload, Resistance Mechanisms, Target Density, and Antibody Internalization

Antibody-drug conjugates (ADC) are a targeted cancer therapy that utilize the specificity of antibodies to deliver potent drugs selectively to tumors. Here we define the complex interaction among factors that dictate ADC efficacy in neuroblastoma by testing both a comprehensive panel of ADC payloads in a diverse set of neuroblastoma cell lines and utilizing the glypican 2 (GPC2)-targeting D3-GPC2-PBD ADC to study the role of target antigen density and antibody internalization in ADC efficacy in neuroblastoma. We first find that DNA binding drugs are significantly more cytotoxic to neuroblastomas than payloads that bind tubulin or inhibit DNA topoisomerase 1. We additionally show that neuroblastomas with high expression of the ABCB1 drug transporter or that harbor a TP53 mutation are significantly more resistant to tubulin and DNA/DNA topoisomerase 1 binding payloads, respectively. Next, we utilized the GPC2-specific D3-GPC2-IgG1 antibody to show that neuroblastomas internalize this antibody/GPC2 complex at significantly different rates and that these antibody internalization kinetics correlate significantly with GPC2 cell surface density. However, sensitivity to pyrrolobenzodiazepine (PBD) dimers primarily dictated sensitivity to the corresponding D3-GPC2-PBD ADC, overall having a larger influence on ADC efficacy than GPC2 cell surface density or antibody internalization. Finally, we utilized GPC2 isogenic Kelly neuroblastoma cells with different levels of cell surface GPC2 expression to define the threshold of target density required for ADC efficacy. Taken together, DNA binding ADC payloads should be prioritized for development for neuroblastoma given their superior efficacy and considering that ADC payload sensitivity is a major determinant of ADC efficacy.

Corneal Changes After Belantamab Mafodotin in Multiple Myeloma Patients

OBJECTIVES

To describe progressive corneal microcyst-like epithelial changes (MECs) that developed in patients treated with the investigational drug belantamab mafodotin (belamaf) for refractory multiple myeloma (MM).

METHODS

This is a single center case series of patients with MM receiving the investigational drug belamaf.

RESULTS

All 12 patients included in this analysis who were treated with belamaf developed MECs that initially appeared in the peripheral cornea and progressed centrally with time. Cessation of therapy resulted in regression of the MECs first in the periphery then centrally. Microcyst-like epithelial changes recurred in all patients on retreatment. With prolonged therapy, eight patients developed corneal staining patterns suggestive of limbal stem cell dysfunction (LSCD).

CONCLUSION

We describe MECs and LSCD associated with systemic administration of belamaf. Further study is needed to determine the etiology and composition of the MECs and the mechanism of limbal stem cell involvement.

Implementing antibody-drug conjugates (ADCs) in HER2-positive breast cancer: state of the art and future directions

The development of anti-HER2 agents has been one of the most meaningful advancements in the management of metastatic breast cancer, significantly improving survival outcomes. Despite the efficacy of anti-HER2 monoclonal antibodies, concurrent chemotherapy is still needed to maximize response. Antibody-drug conjugates (ADCs) are a class of therapeutics that combines an antigen-specific antibody backbone with a potent cytotoxic payload, resulting in an improved therapeutic index. Two anti-HER2 ADCs have been approved by the FDA with different indications in HER2-positive breast cancer. Ado-trastuzumab emtansine (T-DM1) was the first-in-class HER2-targeting ADC, initially approved in 2013 for metastatic patients who previously received trastuzumab and a taxane, and the label was expanded in 2019 to include adjuvant treatment of high-risk patients with residual disease after neoadjuvant taxane and trastuzumab-based therapy. In 2020, trastuzumab deruxtecan (T-DXd) was the second approved ADC for patients who had received at least 2 lines of anti-HER2-based therapy in the metastatic setting. The success of these two agents has transformed the treatment of HER2-positive breast cancer and has re-energized the field of ADC development. Given their advanced pharmaceutical properties, next-generation HER2-targeted ADCs have the potential to be active beyond traditional HER2-positive breast cancer and may be effective in cells with low expression of HER2 or ERBB2 mutations, opening a spectrum of new possible clinical applications. Ongoing challenges include improving target-specificity, optimizing the toxicity profile, and identifying biomarkers for patient selection. The aim of this review is to summarize the principal molecular, clinical, and safety characteristics of approved and experimental anti-HER2 ADCs, contextualizing the current and future landscape of drug development.

Longer term outcomes with single-agent belantamab mafodotin in patients with relapsed or refractory multiple myeloma: 13-month follow-up from the pivotal DREAMM-2 study

Background

On the basis of the DREAMM‐2 study (ClinicalTrials.gov identifier NCT03525678), single‐agent belantamab mafodotin (belamaf) was approved for patients with relapsed or refractory multiple myeloma (RRMM) who received ≥4 prior therapies, including anti‐CD38 therapy. The authors investigated longer term efficacy and safety outcomes in DREAMM‐2 after 13 months of follow‐up among patients who received belamaf 2.5 mg/kg.

Methods

DREAMM‐2 is an ongoing, phase 2, open‐label, 2‐arm study investigating belamaf (2.5 or 3.4 mg/kg) in patients with RRMM who had disease progression after ≥3 lines of therapy and were refractory to immunomodulatory drugs and proteasome inhibitors and refractory and/or intolerant to an anti‐CD38 therapy. The primary outcome was the proportion of patients that achieved an overall response, assessed by an independent review committee.

Results

As of January 31, 2020, 10% of patients still received belamaf 2.5 mg/kg. Thirty‐one of 97 patients (32%; 97.5% confidence interval [CI], 21.7%‐43.6%) achieved an overall response, and 18 responders achieved a very good partial response or better. Median estimated duration of response, overall survival, and progression‐free survival were 11.0 months (95% CI, 4.2 months to not reached), 13.7 months (95% CI, 9.9 months to not reached), and 2.8 months (95% CI, 1.6‐3.6 months), respectively. Response and survival outcomes in patients who had high‐risk cytogenetics or renal impairment were consistent with outcomes in the overall population. Outcomes were poorer in patients with extramedullary disease. In patients who had a clinical response and prolonged dose delays (>63 days; mainly because of corneal events), 88% maintained or deepened responses during their first prolonged dose delay. Overall, there were no new safety signals during this follow‐up.

Conclusions

Extended follow‐up confirms sustained clinical activity without new safety signals with belamaf in this heavily pretreated patient population with RRMM.

Extended follow‐up of patients enrolled in the ongoing phase 2 DREAMM‐2 study confirms sustained clinical activity without new safety signals in patients with relapsed or refractory multiple myeloma who receive belantamab mafodotin 2.5 mg/kg every 3 weeks. These data show that belantamab mafodotin has the potential to shift the treatment paradigm in this heavily pretreated, anti‐CD38 monoclonal antibody–exposed patient population, which has a poor prognosis and few alternative treatment options.

Dawn of a new era of antibody-drug conjugates and bispecific T-cell engagers for treatment of multiple myeloma: a systematic review of literature

Multiple myeloma (MM) remains an incurable disease with the majority of patients experiencing disease relapse despite response to initial therapy. Antibody-drug conjugates (ADCs) and bispecific T-cell engagers are innovative immunotherapeutic approaches currently in development for the treatment of MM. This systematic review summarizes the efficacy and safety of ADCs and bispecific T-cell engagers in relapsed refractory (RR) MM patients from 2010 to date. Comprehensive literature search was conducted on PubMed, EMBASE, Wiley Cochrane Library, Web of Science, and Clinicaltrials.gov . A total of 13 studies (n = 529) met inclusion eligibility. All studies were prospective in nature investigating ADCs or bispecific T-cell engagers in RR MM; 10 trials were phase 1 and 3 were phase 2. The median age of patients ranged from 24 to 82 years. Among trials with ADC regimens, the overall response (OR) ranged from 34 to 60% and complete response (CR) ranged from 3 to 6%. The most common non-hematologic adverse event (AE) of ADCs was keratopathy, while anemia and thrombocytopenia were the most common hematological AEs. With bispecific T-cell engagers , ORR ranged from 31 to 83%, CR ranged from 7 to 22%, and partial response (PR) ranged from 5 to 16%. The most common non-hematologic AE of bispecific T-cell engagers was cytokine release syndrome (CRS) while the most common hematological AE was neutropenia. Initial data appears to show good clinical activity and tolerable safety profiles, making ADCs and bispecific T-cell engagers promising agents for RRMM. Future studies with newer combinations and a longer follow-up are needed to determine the precise role of these novel therapies in the evolving paradigm of MM treatment.

Investigational immunotherapy targeting CD19 for the treatment of acute lymphoblastic leukemia

INTRODUCTION

The anti-CD19 immunotherapy for the treatment of B-precursor acute lymphoblastic leukemia (B-ALL) underwent an expansion in the last decade. CD19 is widely expressed on B-ALL and nearly ideal for immunotherapy because of strong 'on target' ─ but manageable 'off target' effects.

AREAS COVERED

We review the major advances in the field, including data on CD19 monoclonal antibodies, antibody-drug conjugates, bispecific T-cell engaging antibodies and adoptive cellular therapies such as chimeric antigen receptor T cells (CAR-Ts). We discuss novel strategies on approved anti-CD19 immunotherapies. The focus is on experimental anti-CD19 antibodies or CAR-Ts, which might overcome the limitations of toxicity, rapid clearance or resistance.

EXPERT OPINION

The potential of new anti-CD19 antibodies in ALL is limited. The most promising results were achieved with novel cellular constructs. Bi- or multi-specific CAR-Ts might overcome the immune escape by antigen loss. Modified constructs with lower peak expansion or longer persistence provide better control of the toxicity and might improve the efficacy. Finally, the allogeneic 'off the shelf' constructs from healthy donors avoid the time-consuming preparation and the exhaustion of immune cells.

Profile and Management of Toxicity of Selinexor and Belantamab Mafodotin for the Treatment of Triple Class Refractory Multiple Myeloma

Treatment options are limited for multiple myeloma patients who have developed four/five drug-refractory disease. Selinexor (Sel) and belantamab mafodotin (belamaf) were recently approved by the US FDA for treatment of RRMM. The toxicity profile of these drugs is a concern since these agents are used in patients who have already undergone multiple lines of treatment. In this review, we discuss the toxicity profile and strategies for the management of toxicities of Sel and belamaf for the treatment of RRMM. We conducted a comprehensive literature search on PubMed, Embase, Cochrane, and Clinicaltrials.gov using the terms “selinexor”, “belantamab”, “belamaf”, and “multiple myeloma” without applying any limitations based on the date of the study, language, or country of origin. The most common hematological toxicity associated with these two drugs is thrombocytopenia. Cytopenias, constitutional symptoms, gastrointestinal effects, and hyponatremia are the major toxicities of Sel. Keratopathy and anemia are the major toxicities of belamaf. Treatment modifications and dose interruption are usually needed when side effects are more than grade II. As these are newer drugs with limited data, continuous surveillance and monitoring are warranted during the treatment course with early mitigation strategies.

Antibody-drug conjugates, immune-checkpoint inhibitors, and their combination in breast cancer therapeutics

INTRODUCTION

Advanced breast cancer (aBC) remains incurable and the quest for more effective systemic anticancer agents continues. Promising results have led to the FDA approval of three antibody-drug conjugates (ADCs) and two immune checkpoint inhibitors (ICIs) to date for patients with aBC.

AREAS COVERED

With the anticipated emergence of newer ADCs and ICIs for patients with several subtypes of breast cancer, and given their potential synergy, their use in combination is of clinical interest. In this article, we review the use of ADCs and ICIs in patients with breast cancer, assess the scientific rationale for their combination, and provide an overview of ongoing trials and some early efficacy and safety results of such dual therapy.

EXPERT OPINION

Improvement in the medicinal chemistry of next-generation ADCs, their rational combination with ICIs and other agents, and the development of multiparametric immune biomarkers could help to significantly improve the outlook for patients with refractory aBC.

Progress in Gynecologic Cancers with Antibody Drug Conjugates

PURPOSE OF REVIEW

This article provides a comprehensive review of antibody-drug conjugates (ADCs) under investigation in gynecologic cancers. The structure and function of ADCs are reviewed with a focus on clinical benefit as well as toxicity profiles.

RECENT FINDINGS

Several ADCs with various target antigens have been investigated in ovarian, cervical, and endometrial cancer. ADCs have consistently demonstrated favorable safety/tolerability profiles both as monotherapy and in combination therapy. In ovarian cancer, response rates have ranged from 9 to 46% for monotherapy with response rates as high as 83% in combination therapy. In patients with cervical cancer with progressive disease despite doublet therapy and bevacizumab, response rates as high as 24% have been observed. ADCs represent a rapidly evolving field of targeted therapy which have demonstrated notable clinical benefit both as monotherapy but also in combination therapy with an overall favorable toxicity profile. With continued refinement of the target biomarkers utilized, improved clinical benefit is likely to be observed.

Structural changes of corneal epithelium in belantamab-associated superficial keratopathy using anterior segment optical coherence tomography

Purpose

To describe structural changes in corneal epithelium using anterior segment optical coherence tomography (AS-OCT) in two relapsed and refractory multiple myeloma (RRMM) patients with bilateral belantamab-associated superficial keratopathy (BASK).

Observations case 1

A 56-year-old male who was diagnosed with RRMM and initiated on belantamab mafodotin, presented on day 42 (three weeks after the second infusion) with decreased pinhole visual acuity from 20/20 and 20/25 to 20/70 and 20/50 in the right eye and left eye, respectively. Slit-lamp examination revealed moderate superficial keratopathy with microcystic-like epithelial changes (MECs) in the paracentral cornea in both eyes. AS-OCT demonstrated increased bilateral heterogeneous signal intensity and hyperreflective lesions as well as increased thickness in the paracentral corneal epithelium with uninvolved central cornea. Given bilateral MECs, the third infusion was withheld, and then given on day 62 after five weeks of drug-free interval. Although MECs had improved on day 82, pinhole visual acuity remained at 20/50 and 20/40 in the right eye and the left eye. AS-OCT showed that hyperreflective lesions mostly resolved and corneal epithelial thickness returned to baseline, despite a slightly increased persisting heterogeneous signal intensity in the peripheral corneal epithelium in both eyes.

Case 2

A 77-year-old male with RRMM was started on belantamab mafodotin infusions. His pinhole visual acuity decreased from 20/40 and 20/30 at baseline to 20/60 and 20/40 on day 41 (three weeks after the second infusion) in the right eye and left eye, respectively. Slit-lamp examination showed diffuse, moderate MECs in both eyes, which was more severe in the peripheral cornea. AS-OCT demonstrated increased bilateral heterogeneous signal intensity and hyperreflective lesions in the corneal epithelium, which are more severe in the right eye along with increased corneal epithelial thickness. Therefore, belantamab mafodotin was withheld.

Conclusions and Impotance

AS-OCT objectively demonstrated structural changes such as signal intensity and thickness alterations with hyperreflective lesions in the corneal epithelium related to BASK. AS-OCT might be useful for clinicians to monitor ocular surface adverse events in RRMM patients receiving belantamab mafodotin and to adjust therapeutic plans for the patients.

Antibody-Drug Conjugates for the Treatment of Breast Cancer

Metastatic breast cancer (BC) is currently an incurable disease. Besides endocrine therapy and targeted agents, chemotherapy is often used in the treatment of this disease. However, lack of tumor specificity and toxicity associated with dose exposure limit the manageability of cytotoxic agents. Antibody-drug conjugates (ADCs) are a relatively new class of anticancer drugs. By merging the selectivity of monoclonal antibodies with the cytotoxic properties of chemotherapy, they improve the therapeutic index of antineoplastic agents. Three core components characterize ADCs: the antibody, directed to a target antigen; the payload, typically a cytotoxic agent; a linker, connecting the antibody to the payload. The most studied target antigen is HER2 with some agents, such as trastuzumab deruxtecan, showing activity not only in HER2-positive, but also in HER2-low BC patients, possibly due to a bystander effect. This property to provide a cytotoxic impact also against off-target cancer cells may overcome the intratumoral heterogeneity of some target antigens. Other cancer-associated antigens represent a strategy for the development of ADCs against triple-negative BC, as shown by the recent approval of sacituzumab govitecan. In this review, we discuss the current landscape of ADC development for the treatment of BC, as well as the possible limitations of this 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.

Unlocking the potential of antibody-drug conjugates for cancer therapy

Nine different antibody-drug conjugates (ADCs) are currently approved as cancer treatments, with dozens more in preclinical and clinical development. The primary goal of ADCs is to improve the therapeutic index of antineoplastic agents by restricting their systemic delivery to cells that express the target antigen of interest. Advances in synthetic biochemistry have ushered in a new generation of ADCs, which promise to improve upon the tissue specificity and cytotoxicity of their predecessors. Many of these drugs have impressive activity against treatment-refractory cancers, although hurdles impeding their broader use remain, including systemic toxicity, inadequate biomarkers for patient selection, acquired resistance and unknown benefit in combination with other cancer therapies. Emerging evidence indicates that the efficacy of a given ADC depends on the intricacies of how the antibody, linker and payload components interact with the tumour and its microenvironment, all of which have important clinical implications. In this Review, we discuss the current state of knowledge regarding the design, mechanism of action and clinical efficacy of ADCs as well as the apparent limitations of this treatment class. We then propose a path forward by highlighting several hypotheses and novel strategies to maximize the potential benefit that ADCs can provide to patients with cancer.

ASN004, A 5T4-targeting scFv-Fc Antibody-Drug Conjugate with High Drug-to-Antibody Ratio, Induces Complete and Durable Tumor Regressions in Preclinical Models

The 5T4 oncofetal antigen (trophoblast glycoprotein) is expressed in a wide range of malignant tumors but shows very limited expression in normal adult tissues. ASN004 is a 5T4-targeted antibody-drug conjugate (ADC) that incorporates a novel single-chain Fv-Fc antibody and Dolaflexin drug-linker technology, with an Auristatin F hydroxypropylamide payload drug-to-antibody ratio of approximately 10-12. The pharmacology, toxicology, and pharmacokinetic properties of ASN004 and its components were investigated in vitro and in vivo ASN004 showed high affinity for the 5T4 antigen and was selectively bound to and internalized into 5T4-expressing tumor cells, and potent cytotoxicity was demonstrated for a diverse panel of solid tumor cell lines. ASN004 induced complete and durable tumor regression in multiple tumor xenograft models, derived from human lung, breast, cervical, and gastric tumor cell lines having a wide range of 5T4 expression levels. A single dose of ASN004, as low as 1 mg/kg i.v., achieved complete tumor regression leading to tumor-free survivors in the A431 cervical cancer model. In head-to-head studies, superior activity of ASN004 was demonstrated against trastuzumab-DM1, in a low-5T4/high-HER2 expressing gastric tumor model, and 10-fold greater potency was found for ASN004 against the 5T4-targeted ADC PF-06263507 in a lung tumor model. In marmoset monkeys, ASN004 was well tolerated at doses up to 1.5 mg/kg Q3W i.v., and showed dose-dependent exposure, linear pharmacokinetics, and markedly low exposure of free payload drug. Taken together, these findings identify ASN004 as a promising new ADC therapeutic for clinical evaluation in a broad range of solid tumor types.

Management of belantamab mafodotin-associated corneal events in patients with relapsed or refractory multiple myeloma (RRMM)

Belantamab mafodotin (belamaf) demonstrated deep and durable responses in patients with heavily pretreated relapsed or refractory multiple myeloma (RRMM) in DREAMM-2 (NCT03525678). Corneal events, specifically keratopathy (including superficial punctate keratopathy and/or microcyst-like epithelial changes (MECs), eye examination findings with/without symptoms), were common, consistent with reports from other antibody–drug conjugates. Given the novel nature of corneal events in RRMM management, guidelines are required for their prompt identification and appropriate management. Eye examination findings from DREAMM-2 and insights from hematology/oncology investigators and ophthalmologists, including corneal specialists, were collated and used to develop corneal event management guidelines. The following recommendations were formulated: close collaboration among hematologist/oncologists and eye care professionals is needed, in part, to provide optimal care in relation to the belamaf benefit–risk profile. Patients receiving belamaf should undergo eye examinations before and during every treatment cycle and promptly upon worsening of symptoms. Severity of corneal events should be determined based on corneal examination findings and changes in best-corrected visual acuity. Treatment decisions, including dose modifications, should be based on the most severe finding present. These guidelines are recommended for the assessment and management of belamaf-associated ocular events to help mitigate ocular risk and enable patients to continue to experience a clinical benefit with belamaf.

Ocular Toxicity of Belantamab Mafodotin, an Oncological Perspective of Management in Relapsed and Refractory Multiple Myeloma

Belantamab mafodotin (belamaf), an antibody-drug conjugate approved for the treatment of relapsed and refractory multiple myeloma (RRMM), is an anti B-cell maturation antigen (BCMA) agent. DREAMM-1, a first in-human trial of belamaf, reported several ocular toxicities requiring dose adjustments, dose delays and treatment discontinuations. In DREAMM-1, 53% of patients in part-1 and 63% of patients in part-2 had ocular toxicity. Similarly, 73% of patients in DREAMM-2 had keratopathy (71% in 2.5 mg/kg versus 75% in 3.4 mg/kg) with the most common symptoms being blurred vision and dry eyes. Ocular toxicity of belamaf is attributed to microtubule-disrupting monomethylauristatin-F (MMAF), a cytotoxic payload of the drug that causes an off-target damage to the corneal epithelial cells. Ocular adverse events (AEs) of belamaf are more frequent at higher doses compared with lower doses. Higher belamaf dose, history of dry eyes and soluble BCMA are associated with increased risk of corneal toxicity. Absence of ocular symptoms does not exclude the possibility of belamaf-induced ocular toxicity, so patients need slit lamp and Snellen visual acuity testing to detect microcytic-like epithelial changes and visual decline. Corticosteroid eyes drops for 4-7 days prior to belamaf dose do not prevent ocular AEs and may cause steroid-related AEs instead. Keratopathy and Visual Acuity scale (KVA) is recommended to document the severity of belamaf-induced ocular toxicity and make treatment adjustments. Management of toxicity includes dosage modifications, treatment interruption or discontinuations and preservative-free artificial tears along with close ophthalmology and hematology-oncology follow-ups.

Burst of Corneal Dendritic Cells during Trastuzumab and Paclitaxel Treatment

During breast cancer therapy, paclitaxel and trastuzumab are both associated with adverse effects such as chemotherapy-induced peripheral neuropathy and other systemic side effects including ocular complications. Corneal nerves are considered part of the peripheral nervous system and can be imaged non-invasively by confocal laser scanning microscopy (CLSM) on the cellular level. Thus, in vivo CLSM imaging of structures of the corneal subbasal nerve plexus (SNP) such as sensory nerves or dendritic cells (DCs) can be a powerful tool for the assessment of corneal complications during cancer treatment. During the present study, the SNP of a breast cancer patient was analyzed over time by using large-scale in vivo CLSM in the course of paclitaxel and trastuzumab therapy. The same corneal regions could be re-identified over time. While the subbasal nerve morphology did not alter significantly, a change in dendritic cell density and an additional local burst within the first 11 weeks of therapy was detected, indicating treatment-mediated corneal inflammatory processes. Ocular structures such as nerves and dendritic cells could represent useful biomarkers for the assessment of ocular adverse effects during cancer therapy and their management, leading to a better visual prognosis.

Antibody Format and Serum Disposition Govern Ocular Pharmacokinetics of Intravenously Administered Protein Therapeutics

Protein therapeutics have witnessed tremendous use and application in recent years in treatment of various diseases. Predicting efficacy and safety during drug discovery and translational development is a key factor for successful clinical development of these therapies. In general, drug related toxicities are predominantly driven by pharmacokinetic (PK) exposure at off-target sites. This work explores the ocular PK of intravenously administered protein therapeutics to understand impact of antibody format on off-site exposure. Species matched non-binding rabbit antibody proteins (rabFab and rabIgG) were intravenously administered to male New Zealand White rabbits at a single 1 mg bolus dose and exposure was measured up to 3 weeks. As anticipated based on absence of FcRn recycling, rabFab has relatively fast systemic PK (CL–943 mL/day and t_1/2–1.93 days) compared to rabIgG (CL–18.5 mL/day and t_1/2–8.93 days). Similarly, rabFab has lower absolute ocular exposure in ocular compartments (e.g., vitreous and aqueous humor) compared to rabIgG, despite higher relative exposures (measured as percent tissue partition in ocular tissues relative to serum, based on C_max and AUC). In general, percent tissue partition based on AUC (in aqueous and vitreous humor) relative to serum exposure were 10.4 and 8.62 for rabFab respectively and 1.11 and 0.64 for rabIgG respectively. This work emphasizes size and format based ocular exposure of intravenously administered protein therapeutics. Findings from this work enable prediction of format based ocular exposure for systemically administered antibody based therapeutics and aid in selection of molecule format for clinical candidate to minimize ocular exposure.

Considerations for the Nonclinical Safety Evaluation of Antibody-Drug Conjugates

The targeted delivery of drugs by means of linking them to antibodies (Abs) to form antibody-drug conjugates (ADCs) has become an important approach in oncology and could potentially be used in other therapeutic areas. Targeted therapy is aimed at improving clinical efficacy while minimizing adverse reactions. The nonclinical safety assessment of ADCs presents several unique challenges involving the need to examine a complex molecule, each component of which can contribute to the effects observed, in appropriate animal models. Some considerations for the nonclinical safety evaluation of ADCs based on a literature review of ADCs in clinical development (currently or previously) are discussed.

Antibody-Based Treatment Approaches in Multiple Myeloma

PURPOSE OF REVIEW

The field of multiple myeloma treatment has entered a new era with antibody-based approaches in clinical practice. In this review, we focus on the clinical approaches of utilizing antibody-based modality, specifically monoclonal antibodies, antibody-drug conjugates, and bispecific T-cell antibodies in the treatment of multiple myeloma.

RECENT FINDINGS

Three monoclonal antibodies (daratumumab, isatuximab, elotuzumab) and one anti-BCMA (B-cell maturation antigen) antibody-drug conjugate (belantamab mafodotin) have been approved by the FDA in the last 5 years for the treatment of multiple myeloma. There are many ongoing clinical trials using novel targets and constructs, including bispecific antibodies against BCMA, GPRC5D, and FCRH5. In addition to exploring efficacy, there are ongoing efforts to overcome the resistance to therapy. Antibody-based therapy has improved the outcomes of patients with multiple myeloma and has been incorporated in the standard of care. We expect to see novel targets and constructs that can achieve a deeper and more durable response while minimizing toxicity, as well as better strategies for toxicity management for existing agents. We also expect that antibody-based strategies will be used in earlier lines of therapy in the future.

Enfortumab Vedotin: Nursing Perspectives on the Management of Adverse Events in Patients With Locally Advanced or Metastatic Urothelial Carcinoma

BACKGROUND

Many patients with locally advanced or metastatic urothelial carcinoma (mUC) need additional treatment options beyond PD-1 or PD-L1 inhibitors and platinum-based chemotherapies. Enfortumab vedotin-ejfv (EV) is an antibody-drug conjugate directed at Nectin-4 that received accelerated approval for treatment of adults with locally advanced or mUC previously treated with PD-1/PD-L1 inhibitors and platinum- containing chemotherapy in the neoadjuvant/adjuvant, locally advanced, or metastatic settings.

OBJECTIVES

This article provides practical considerations and recommendations regarding common and potentially treatment-limiting adverse events that may arise with EV therapy.

METHODS

The clinical data that supported the approval of EV are reviewed, and supporting safety and management considerations are provided based on the authors' experience.

FINDINGS

EV therapy can be optimized through patient and caregiver education, proactive patient monitoring, early identification of adverse events, and timely intervention to alleviate symptoms.

Reversible HER2 antibody-drug conjugate-induced ocular toxicity

PURPOSE

To report 3 cases of reversible epitheliopathy induced by A166-a human epidermal growth factor receptor (HER2)-targeted antibody-drug conjugate (ADC) therapy for resistant HER2 tumours.

METHODS

Advanced HER2 tumour patients were enrolled in A166 phase I/II clinical trial using Bayesian logistic regression model dose escalation. Key exclusion criteria were ≥grade 2 (G2) corneal pathology, severe organ disease, and other cancer therapy within 4 weeks. Eye exams were performed at baseline, regularly scheduled intervals, and additionally upon A166-induced ocular symptoms. Topical therapy with autologous serum tears (ASTs) was implemented based on visual acuity, symptoms, and slit lamp exam. A166 was withheld if ≥G2 ocular toxicity developed; if status improved to ≤G1, A166 therapy was resumed. Visual acuity, corneal exam, and subjective comfort were recorded.

RESULTS

After ≥2 cycles of A166, 6 eyes of 3/23 enrolled patients developed whorl pattern epitheliopathy suggestive of limbal stem cell (LSC) dysfunction requiring cessation of A166 despite positive tumour response. Patients 1 and 3 received 3.6 mg/kg A166 dose, and patient 2 received 3.0 mg/kg. Topical steroids (2/4 eyes) failed to improve epitheliopathy. Adding ASTs improved vision, ocular comfort, and whorl pattern epitheliopathy in 6/6 eyes within 3 weeks. Patient 1 continues to improve on ASTs; patient 2 withdrew from the study; and patient 3 resumed A166 therapy.

CONCLUSION

A166 precipitates LSC dysfunction-like epitheliopathy. Combination therapy including aggressive lubrication, withholding drug, and ASTs help reverse toxicity. Recognizing that ADC-induced epitheliopathy can respond to ocular management may enable cancer patients to continue lifesaving therapy.

Clinical Development of New Antibody-Drug Conjugates in Breast Cancer: To Infinity and Beyond

Metastatic breast cancer remains an incurable disease, and new therapies are needed. One major limitation of chemotherapy is the toxicity associated with higher dose exposure. Antibody-drug conjugates (ADCs) are a complex and evolving class of agents specifically designed with the objective of delivering antineoplastic medicines in the most precise and selectively targeted way. ADCs are composed of four key components: (1) the target antigen, (2) an antibody construct, (3) a payload (most commonly a cytotoxic agent), and (4) a linker moiety that couples the payload and the antibody. In this review, we discuss the clinical development of ADCs for the treatment of breast cancer, focusing on two recently FDA-approved agents, trastuzumab deruxtecan and sacituzumab govitecan, and discuss the ongoing efforts exploring new agents. Finally, we summarize the current portfolio of clinical trials that could change the algorithm of treatment for early and advanced breast cancer.

Belantamab Mafodotin to Treat Multiple Myeloma: A Comprehensive Review of Disease, Drug Efficacy and Side Effects

Multiple myeloma (MM) is a hematologic malignancy characterized by excessive clonal proliferation of plasma cells. The treatment of multiple myeloma presents a variety of unique challenges due to the complex molecular pathophysiology and incurable status of the disease at this time. Given that MM is the second most common blood cancer with a characteristic and unavoidable relapse/refractory state during the course of the disease, the development of new therapeutic modalities is crucial. Belantamab mafodotin (belamaf, GSK2857916) is a first-in-class therapeutic, indicated for patients who have previously attempted four other treatments, including an anti-CD38 monoclonal antibody, a proteosome inhibitor, and an immunomodulatory agent. In November 2017, the FDA designated belamaf as a breakthrough therapy for heavily pretreated patients with relapsed/refractory multiple myeloma. In August 2020, the FDA granted accelerated approval as a monotherapy for relapsed or treatment-refractory multiple myeloma. The drug was also approved in the EU for this indication in late August 2020. Of note, belamaf is associated with the following adverse events: decreased platelets, corneal disease, decreased or blurred vision, anemia, infusion-related reactions, pyrexia, and fetal risk, among others. Further studies are necessary to evaluate efficacy in comparison to other standard treatment modalities and as future drugs in this class are developed.

A Randomized Phase II Study of AGS-16C3F Versus Axitinib in Previously Treated Patients with Metastatic Renal Cell Carcinoma

LESSONS LEARNED

The primary endpoint of this phase II study that evaluated the efficacy and safety of the investigational compound, AGS-16C3F, versus axitinib in previously treated patients with metastatic renal cell carcinoma (mRCC) was not met. Median progression-free survival, the primary endpoint, was 2.9 months with AGS-16C3F and 5.7 months with axitinib (HR, 1.676; 95% CI, 1.107-2.537; p = .015), per investigator assessment The safety profile for each study drug was as expected, with the most commonly reported adverse events being fatigue (53%) and nausea (47%) in the AGS-16C3F arm and fatigue (57%) and diarrhea (48%) in the axitinib arm. These results provide a benchmark for axitinib use in heavily pretreated patients with mRCC.

BACKGROUND

AGS-16C3F is a novel antibody-drug conjugate that targets cell-surface ectonucleotide pyrophosphatase/phosphodiesterase 3 (ENPP3) and is conjugated to a microtubule disruptive agent. Here we present findings from a phase II study of AGS-16C3F versus axitinib in metastatic renal cell carcinoma (mRCC).

METHODS

Patients with mRCC of any histology and disease progression during or after their last treatment regimen were randomized 1:1 to intravenous AGS-16C3F 1.8 mg/kg every 3 weeks or oral axitinib 5 mg twice daily (starting dose). The primary objective was investigator-assessed progression-free survival (PFS) of AGS-16C3F versus axitinib (RECIST version 1.1).

RESULTS

In the total population (N = 133), 63% (n = 84) of patients had completed the study at data cutoff (August 21, 2019). Median PFS was 2.9 months with AGS-16C3F and 5.7 months with axitinib (hazard ratio [HR], 1.676; 95% confidence interval [CI], 1.107-2.537; p = .015). There were no significant differences between arms in secondary efficacy endpoints, including overall survival (13.1 months, AGS-16C3F and 15.4 months, axitinib; HR, 1.079; 95% CI, 0.681-1.707; p = .747). In the safety population (n = 131), the most commonly reported adverse events were fatigue (53%) and nausea (47%) in the AGS-16C3F arm and fatigue (57%) and diarrhea (48%) in the axitinib arm. The incidence of diarrhea was lower in the AGS-16C3F arm than in the axitinib arm (17% vs. 48%), and ocular toxicities were more frequent in the AGS-16C3F arm than in the axitinib arm (44% vs. 26%).

CONCLUSION

The investigational compound, AGS-16C3F, did not meet the primary endpoint of this trial. These study results provide a benchmark for axitinib use in heavily pretreated patients with mRCC.

Antibody Co-Administration Can Improve Systemic and Local Distribution of Antibody-Drug Conjugates to Increase In Vivo Efficacy

Several antibody-drug conjugates (ADC) showing strong clinical responses in solid tumors target high expression antigens (HER2, TROP2, Nectin-4, and folate receptor alpha/FRα). Highly expressed tumor antigens often have significant low-level expression in normal tissues, resulting in the potential for target-mediated drug disposition (TMDD) and increased clearance. However, ADCs often do not cross-react with normal tissue in animal models used to test efficacy (typically mice), and the impact of ADC binding to normal tissue antigens on tumor response remains unclear. An antibody that cross-reacts with human and murine FRα was generated and tested in an animal model where the antibody/ADC bind both human tumor FRα and mouse FRα in normal tissue. Previous work has demonstrated that a "carrier" dose of unconjugated antibody can improve the tumor penetration of ADCs with high expression target-antigens. A carrier dose was employed to study the impact on cross-reactive ADC clearance, distribution, and efficacy. Co-administration of unconjugated anti-FRα antibody with the ADC-improved efficacy, even in low expression models where co-administration normally lowers efficacy. By reducing target-antigen-mediated clearance in normal tissue, the co-administered antibody increased systemic exposure, improved tumor tissue penetration, reduced target-antigen-mediated uptake in normal tissue, and increased ADC efficacy. However, payload potency and tumor antigen saturation are also critical to efficacy, as shown with reduced efficacy using too high of a carrier dose. The judicious use of higher antibody doses, either through lower DAR or carrier doses, can improve the therapeutic window by increasing efficacy while lowering target-mediated toxicity in normal tissue.

Targeting cancer with antibody-drug conjugates: Promises and challenges

Antibody-drug conjugates (ADCs) are a rapidly expanding class of biotherapeutics that utilize antibodies to selectively deliver cytotoxic drugs to the tumor site. As of May 2021, the U.S. Food and Drug Administration (FDA) has approved ten ADCs, namely Adcetris®, Kadcyla®, Besponsa®, Mylotarg®, Polivy®, Padcev®, Enhertu®, Trodelvy®, Blenrep®, and Zynlonta™ as monotherapy or combinational therapy for breast cancer, urothelial cancer, myeloma, acute leukemia, and lymphoma. In addition, over 80 investigational ADCs are currently being evaluated in approximately 150 active clinical trials. Despite the growing interest in ADCs, challenges remain to expand their therapeutic index (with greater efficacy and less toxicity). Recent advances in the manufacturing technology for the antibody, payload, and linker combined with new bioconjugation platforms and state-of-the-art analytical techniques are helping to shape the future development of ADCs. This review highlights the current status of marketed ADCs and those under clinical investigation with a focus on translational strategies to improve product quality, safety, and efficacy.

Focus on monoclonal antibodies targeting B-cell maturation antigen (BCMA) in multiple myeloma: update 2021

Remarkable advances have been achieved in the treatment of multiple myeloma (MM) in the last decade, which saw targeted immunotherapy, represented by anti-CD38 monoclonal antibodies, successfully incorporated across indications. However, myeloma is still considered curable in only a small subset of patients, and the majority of them eventually relapse. B-cell maturation antigen (BCMA) is expressed exclusively in mature B lymphocytes and plasma cells, and represents an ideal new target for immunotherapy, presented by bispecific antibody (bsAb) constructs, antibody-drug conjugates (ADCs) and chimeric antigen receptor T (CAR-T) cells. Each of them has proved its efficacy with the potential for deep and long-lasting responses as a single agent therapy in heavily pretreated patients. As a result, belantamab mafodotin was approved by the United States Food and Drug Administration for the treatment of relapsed/refractory MM, as the first anti-BCMA agent. In the present review, we focus on monoclonal antibodies targeting BCMA - bsAbs and ADCs. The data from preclinical studies as well as first-in-human clinical trials will be reviewed, together with the coverage of their constructs and mechanisms of action. The present results have laid the groundwork for the ongoing or upcoming clinical trials with combinatory regimens, which have always been a cornerstone in the treatment of MM.

Clinical and Histological Characterization of Toxic Keratopathy From Depatuxizumab Mafodotin (ABT-414), an Antibody-Drug Conjugate

PURPOSE

To report the histological findings and clinical course of 2 patients with microcyst-like epithelial keratopathy (MEK) associated with antibody-drug conjugate, depatuxizumab mafodotin.

METHODS

Case series.

RESULTS

Two patients with glioblastoma multiforme participating in a phase 3 clinical trial of the antibody-drug conjugate, depatuxizumab mafodotin, presented with bilateral MEK. Confocal imaging showed multiple large, round, hyperreflective lesions in the epithelium. Epithelial debridement was performed for symptomatic relief in both patients. Along with aggressive lubrication, bandage contact lenses, and reduction in the chemotherapeutic dose to maintenance levels, both patients experienced symptomatic improvement. However, MEK lesions recurred after re-epithelialization. Immunohistochemistry of the diseased epithelium showed immunoglobulin (Ig)G-positive granular cytoplasmic inclusions and increased cell apoptosis.

CONCLUSIONS

Depatuxizumab mafodotin accumulates in the basal corneal epithelium resulting in MEK because of increased apoptosis. Frequent lubrication and bandage contact lenses can provide symptom relief.

Ocular Side Effects of EGFR-Inhibitor ABT-414 in Recurrent Glioblastoma: A Long-Term Safety Study

This study aimed to prospectively evaluate, on a long-term basis, corneal side effects secondary to compassionate administration of epidermal growth factor receptor (EGFR) inhibitor depatuxizumab mafodotin (ABT-414) in patients affected by EGFR-amplified recurrent glioblastoma. Fifteen patients with a median follow-up of 4.3 months after treatment discontinuation were enrolled. Each patient underwent full ophthalmologic examination including in vivo corneal confocal microscopy (CCM). No CTCAE grade 4 toxicity and four (27%) grade 3 toxicities were documented during treatment. Ocular symptoms (blurred vision, eye pain, photophobia) were experienced by all patients, reaching maximal severity after the second ABT-414 infusion, with persistence until treatment discontinuation. During treatment, CCM documented specific changes in the corneal epithelium and in the sub-basal nerve plexus layer fibers of all eyes. The median time of symptoms resolution after treatment discontinuation ranged from 38 days (eye pain) to 53 days (photophobia). The median time of signs resolution ranges from 14 days (corneal ulcer) to 38 days (superficial punctate epitheliopathy, corneal stroma edema and intraepithelial cysts). ABT-414 corneal side effects are detectable in all treated patients. Related symptoms are gradually experienced by all patients during treatment and although reversible, they are characterized by a relative prolonged persistence after treatment discontinuation.

Development of a physiologically-based pharmacokinetic model for ocular disposition of monoclonal antibodies in rabbits

Development of protein therapeutics for ocular disorders, particularly age-related macular degeneration (AMD), is a highly competitive and expanding therapeutic area. However, the application of a predictive and translatable ocular PK model to better understand ocular disposition of protein therapeutics, such as a physiologically-based pharmacokinetic (PBPK) model, is missing from the literature. Here, we present an expansion of an antibody platform PBPK model towards rabbit and incorporate a novel anatomical and physiologically relevant ocular component. Parameters describing all tissues, flows, and binding events were obtained from existing literature and fixed a priori. First, translation of the platform PBPK model to rabbit was confirmed by evaluating the model's ability to predict plasma PK of a systemically administered exogenous antibody. Then, the PBPK model with the new ocular component was validated by estimation of serum and ocular (i.e. aqueous humor, retina, and vitreous humor) PK of two intravitreally administered monoclonal antibodies. We show that the proposed PBPK model is capable of accurately (i.e. within twofold) predicting ocular exposure of antibody-based drugs. The proposed PBPK model can be used for preclinical-to-clinical translation of antibodies developed for ocular disorders, and assessment of ocular toxicity for systemically administered antibody-based therapeutics.

Belantamab mafodotin in the treatment of relapsed or refractory multiple myeloma

Multiple myeloma remains an incurable disease, with a large proportion of patients in the relapsed/refractory setting often unable to achieve durable responses. Novel, well-tolerated and highly effective therapies in this patient population represent an unmet need. Preclinical studies have shown that B-cell maturation antigen is nearly exclusively expressed on normal and malignant plasma cells, thereby identifying it as a highly selective target for immunotherapeutic approaches. Belantamab mafodotin (GSK2857916, belamaf) is a first-in-class antibody-drug conjugate directed at B-cell maturation antigen and has shown promising activity in clinical trials. In this review, we provide an overview of belantamab mafodotin as a compound and present the available clinical efficacy and safety data in the treatment of relapsed/refractory multiple myeloma.

Immune-based therapies in the management of multiple myeloma

Multiple myeloma (MM) is a clonal plasma cell malignancy affecting a predominantly elderly population. The continued development of newer therapies with novel mechanisms of action has reshaped the treatment paradigm of this disorder in the last two decades, leading to a significantly improved prognosis. This has in turn resulted in an increasing number of patients in need of therapy for relapsed/refractory disease. Immune-based therapies, including monoclonal antibodies, immune checkpoint inhibitors, and most promisingly, adoptive cellular therapies represent important therapeutic strategies in these patients due to their non-cross resistant mechanisms of actions with the usual frontline therapies comprising of immunomodulatory drugs (IMiDs) and proteasome inhibitors (PIs). The anti-CD38 antibodies daratumumab and more recently isatuximab, with their excellent efficacy and safety profile along with its synergy in combination with IMiDs and PIs, are being increasingly incorporated in the frontline setting. Chimeric antigen receptor-T cell (CART) therapies and bi-specific T-cell engager (BiTE) represent exciting new options that have demonstrated efficacy in heavily pretreated and refractory MM. In this review, we discuss the rationale for use of immune-based therapies in MM and summarize the currently available literature for common antibodies and CAR-T therapies that are utilized in MM.

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.

Antibody-Drug Conjugates: A Promising Novel Therapy for the Treatment of Ovarian Cancer

Antibody-drug conjugates (ADCs) represent a novel and promising therapeutic strategy for the treatment of cancer patients. ADCs target antigens highly expressed on the membrane surface of tumor cells to selectively deliver a cytotoxic drug. Ovarian tumors differentially express tumor-specific antigens, which can be used to guide ADCs. This strategy allows for optimizing tumor targeting while minimizing systemic toxicity compared to classical chemotherapeutic agents. ADCs can be improved by using a cleavable linker allowing the delivery of the toxic payload in surrounding cells not expressing the target protein, therefore acting on heterogeneous tumors with different cell populations. Currently, more than 15 ADCs are under preclinical investigation in ovarian cancer, and some of them have already been tested in early-phase clinical trials with promising results. In this review, we summarize the mechanism of action and the toxicity profile of ADCs and discuss the latest preclinical discoveries and forthcoming applications in ovarian cancer.

Corneal Epithelial Findings in Patients with Multiple Myeloma Treated with Antibody-Drug Conjugate Belantamab Mafodotin in the Pivotal, Randomized, DREAMM-2 Study

INTRODUCTION

Patients with relapsed or refractory multiple myeloma (RRMM) represent an unmet clinical need. Belantamab mafodotin (belamaf; GSK2857916) is a first-in-class antibody-drug conjugate (ADC; or immunoconjugate) that delivers a cytotoxic payload, monomethyl auristatin F (MMAF), to myeloma cells. In the phase II DREAMM-2 study (NCT03525678), single-agent belamaf (2.5 mg/kg) demonstrated clinically meaningful anti-myeloma activity (overall response rate 32%) in patients with heavily pretreated disease. Microcyst-like epithelial changes (MECs) were common, consistent with reports from other MMAF-containing ADCs.

METHODS

Corneal examination findings from patients in DREAMM-2 were reviewed, and the clinical descriptions and accompanying images (slit lamp microscopy and in vivo confocal microscopy [IVCM]) of representative events were selected. A literature review on corneal events reported with other ADCs was performed.

RESULTS

In most patients receiving single-agent belamaf (72%; 68/95), MECs were observed by slit lamp microscopy early in treatment (69% had their first event by dose 4). However, IVCM revealed hyperreflective material. Blurred vision (25%) and dry eye (15%) were commonly reported symptoms. Management of MECs included dose delays (47%)/reductions (25%), with few patients discontinuing due to MECs (1%). The first event resolved in most patients (grade ≥2 MECs and visual acuity [each 77%], blurred vision [67%], and dry eye [86%]), with no reports of permanent vision loss to date. A literature review confirmed that similar MECs were reported with other ADCs; however, event management strategies varied. The pathophysiology of MECs is unclear, though the ADC cytotoxic payload may contribute to on- or off-target effects on corneal epithelial cells.

CONCLUSION

Single-agent belamaf represents a new treatment option for patients with RRMM. As with other ADCs, MECs were observed and additional research is warranted to determine their pathophysiology. A multidisciplinary approach, involving close collaboration between eye care professionals and hematologist/oncologists, is needed to determine appropriate diagnosis and management of these patients.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier, NCT03525678.

The Society for Immunotherapy of Cancer consensus statement on immunotherapy for the treatment of multiple myeloma

Outcomes in multiple myeloma (MM) have improved dramatically in the last two decades with the advent of novel therapies including immunomodulatory agents (IMiDs), proteasome inhibitors and monoclonal antibodies. In recent years, immunotherapy for the treatment of MM has advanced rapidly, with the approval of new targeted agents and monoclonal antibodies directed against myeloma cell-surface antigens, as well as maturing data from late stage trials of chimeric antigen receptor CAR T cells. Therapies that engage the immune system to treat myeloma offer significant clinical benefits with durable responses and manageable toxicity profiles, however, the appropriate use of these immunotherapy agents can present unique challenges for practicing physicians. Therefore, the Society for Immunotherapy of Cancer convened an expert panel, which met to consider the current role of approved and emerging immunotherapy agents in MM and provide guidance to the oncology community by developing consensus recommendations. As immunotherapy evolves as a therapeutic option for the treatment of MM, these guidelines will be updated.

Targeted Therapy With Immunoconjugates for Multiple Myeloma

The introduction of proteasome inhibitors (PI) and immunomodulatory drugs (IMiD) has markedly increased the survival of multiple myeloma (MM) patients. Also, the unconjugated monoclonal antibodies (mAb) daratumumab (anti-CD38) and elotuzumab (anti-SLAMF7) have revolutionized MM treatment given their clinical efficacy and safety, illustrating the potential of targeted immunotherapy as a powerful treatment strategy for MM. Nonetheless, most patients eventually develop PI-, IMiD-, and mAb-refractory disease because of the selection of resistant MM clones, which associates with a poor prognosis. Accordingly, these patients remain in urgent need of new therapies with novel mechanisms of action. In this respect, mAbs or mAb fragments can also be utilized as carriers of potent effector moieties to specifically target surface antigens on cells of interest. Such immunoconjugates have the potential to exert anti-MM activity in heavily pretreated patients due to their distinct and pleiotropic mechanisms of action. In addition, the fusion of highly cytotoxic compounds to mAbs decreases the off-target toxicity, thereby improving the therapeutic window. According to the effector moiety, immunoconjugates are classified into antibody-drug conjugates, immunotoxins, immunocytokines, or radioimmunoconjugates. This review will focus on the mechanisms of action, safety and efficacy of several promising immunoconjugates that are under investigation in preclinical and/or clinical MM studies. We will also include a discussion on combination therapy with immunoconjugates, resistance mechanisms, and future developments.

Antibody-drug conjugates for the treatment of ovarian cancer

INTRODUCTION

Ovarian cancer typically presents at an advanced stage and while initial chemotherapy response rates are favorable, a majority of patients experience recurrence with the subsequent development of chemoresistance. Recurrent, platinum-resistant disease is associated with a very poor prognosis as treatment in this setting is often limited by systemic toxicity. Antibody-drug conjugates (ADCs) are novel therapeutic agents designed to target antigens specific to ovarian tumor cells with direct delivery of cytotoxic agents to combat recurrent, platinum-resistant disease while limiting systemic toxicity.

AREAS COVERED

The basic structure and function of ADCs will be reviewed as well as the current data on ADCs under investigation in ovarian cancer.

EXPERT OPINION

ADCs represent a promising class of targeted therapy in recurrent ovarian cancer with excellent response rates particularly when utilized as combination therapy. While mirvetuximab soravtansine is the only ADC that has been evaluated in a phase 3 trial, many other ADCs and trials are on the horizon. As the field of targeted therapy continues to evolve, continued development of target antigens and ADCs are likely to represent a key development in treatment of recurrent, platinum-resistant disease.

Corneal side effects induced by EGFR-inhibitor antibody-drug conjugate ABT-414 in patients with recurrent glioblastoma: a prospective clinical and confocal microscopy study

Background:

The aim of this study was to prospectively analyse, for the first time worldwide by in vivo clinical confocal microscopy (CCM), corneal side effects secondary to the use of epidermal growth factor receptor (EGFR) inhibitor depatuxizumab mafodotin (ABT-414) in a cohort of patients affected by EGFR-amplified recurrent glioblastoma.

Methods:

Each enrolled patient underwent full ophthalmologic examination including in vivo CCM of the cornea. Each patient was examined at baseline and every 2 weeks during treatment as long as patient conditions allowed it.

Results:

A total of 10 patients were consecutively enrolled. Median follow-up was 5 months. No Common Terminology Criteria for Adverse Events Version 4.0 grade 4 toxicity was documented. Two (20%) grade 3 toxicities were documented at week 8. CCM examination detected in all eyes multiple and diffuse hyperreflective white round spots in the corneal basal epithelial layers (100%), progressive subbasal nerve plexus layer fibres fragmentation followed by full disappearance (100%) and appearance of round cystic structures in the corneal epithelium (100%). All CCM documented side effects reached the peak of prevalence and severity after a median of 3 infusions. After treatment discontinuation, the reversibility of corneal side effects was documented at CCM after a median of 4 weeks.

Conclusion:

ABT-414 toxicity is not only directed to the corneal epithelium, but also to corneal nerves. Side effects are detectable in all treated patients and CCM documents early corneal epithelium and subbasal nerve plexus toxicity, with subsequent progressive restoration after treatment discontinuation. Ocular side effects due to ABT-414 can be manageable.