Anti-BCMA CAR T-Cell Therapy bb2121 in Relapsed or Refractory Multiple Myeloma

Emerging agents and regimens for multiple myeloma

The outcomes of multiple myeloma (MM) have been improved significantly with the therapies incorporating proteasome inhibitors (PI), immunomodulatory drugs, monoclonal antibodies (MoAb) and stem cell transplantation. However, relapsed and refractory MM (RRMM) remains a major challenge. Novel agents and regimens are under active clinical development. These include new PIs such as ixazomib, marizomib, and oprozomib; new MoAbs such as isatuximab and MOR202; novel epigenetic agent ricolinostat and novel cytokines such as siltuximab. Recently, the first XPO-1 inhibitor, selinexor, was approved for RRMM. BCMA-targeted BiTE, antibody-drug conjugates and CAR-T cells have the potential to revolutionize the therapy for RRMM. In this review, we summarized the latest clinical development of these novel agents and regimens.

CAR T-Cells in Multiple Myeloma Are Ready for Prime Time

The survival of patients with multiple myeloma (MM) has been dramatically improved in the last decade thanks to the incorporation of second-generation proteasome inhibitors (PI), immunomodulatory drugs (IMID), and, more recently, anti-CD38 monoclonal antibodies (MoAb). Nevertheless, still, a major proportion of MM patients will relapse, underscoring the need for new therapies in this disease. Moreover, survival in patients failing the current standard of care regimens (including PI, IMIDs, and anti-CD38 MoAb), which is now defined as triple-class refractory, remains dismal, and new drugs with different mechanism of action are needed. B-cell maturation antigen (BCMA)-targeted therapies and in particular chimeric antigen receptor T cell (CAR T-cell) treatment have emerged as promising platforms to overcome refractoriness to conventional drugs. In this manuscript, we review the current available data regarding CAR T-cell therapy for MM, with a special focus on target selection, clinical results, limitations, and future strategies.

The Application of CAR-T Cells in Haematological Malignancies

Chimeric antigen receptor (CAR)-T cells (CART) remain one of the most advanced and promising forms of adoptive T-cell immunotherapy. CART represent autologous, genetically engineered T lymphocytes expressing CAR, i.e. fusion proteins that combine components and features of T cells as well as antibodies providing their more effective and direct anti-tumour effect. The technology of CART construction is highly advanced in vitro and every element of their structure influence their mechanism of action in vivo. Patients with haematological malignancies are faced with the possibility of disease relapse after the implementation of conventional chemo-immunotherapy. Since the most preferable result of therapy is a partial or complete remission, cancer treatment regimens are constantly being improved and customized to individual patients. This individualization could be ensured by CART therapy. This paper characterized CART strategy in details in terms of their structure, generations, mechanism of action and published the results of clinical trials in haematological malignancies including acute lymphoblastic leukaemia, diffuse large B-cell lymphoma, chronic lymphocytic leukaemia and multiple myeloma.

Three Drug Combinations in the Treatment of Fit Elderly Multiple Myeloma Patients

The multiple myeloma (MM) non transplant eligible (NTE) population is growing in line with the aging of the population in Western countries. Historically, this population has been known for having a greater risk of treatment related toxicity, and therefore drug development was slow and rather oriented towards the improvement of safety profile than the optimization of disease control. However, NTE MM patients, at least for the fit/non frail patients in recent years, seemed to have benefited more from a less palliative care to improve the depth of response and then prolong survival. NTE MM being a quite heterogeneous population, there are still a number of groups of patients that are in need of more efficient therapy, avoiding unnecessary toxicity, particularly for the frail patients. The use of triplet regimen with a melphalan-prednisone (MP) backbone has long been the standard of care for NTE MM, often dedicated to non-frail patients. New standards of care, triplet, and even quadruplet combinations, are emerging on the basis of the MP backbone but also on the more recently approved lenalidomide-dexamethasone (Rd) backbone. These developments were largely possible in line with the development of antibody-based immunotherapies (IT) in MM. The objective to improve outcomes with an acceptable safety profile will see other key therapeutic developments such as the dropping of dexamethasone early in the disease course or various attempts to allow permanent treatment discontinuation with a prolonged disease control. In that context, it is possible that immunomonitoring, minimal residual disease (MRD), and genomic risk-adaptation will become key elements of the treatment decisions on triplet-based regimens.

Cardiotoxicity of Contemporary Anticancer Immunotherapy

PURPOSE OF REVIEW

Contemporary anticancer immunotherapy, particularly immune checkpoint inhibitors (ICI) and chimeric antigen receptor (CAR) T cell therapy, has changed the landscape of treatment for patients with a variety of malignancies who historically had a poor prognosis. However, both immune checkpoint inhibitors and CAR T cell therapy are associated with serious cardiovascular adverse effects. As immunotherapy evolves to include high-risk patients with preexisting cardiovascular risk factors and disease, the risk and relevance of its associated cardiotoxicity will be even higher.

RECENT FINDINGS

ICI can cause myocarditis, which usually occurs early after initiation, can be fulminant, and prompt treatment with high-dose corticosteroids is crucial. CAR T cell therapy frequently leads to cytokine release syndrome, which is associated with cardiomyopathy or arrhythmia development and may also result in circulatory collapse. Supportive treatment, as well as tocilizumab, an anti-interleukin-6 receptor antibody, is the cornerstone of treatment. Recent findings suggest that preexisting cardiovascular risk factors and disease may increase the risk of such cardiotoxicity, and prompt recognition, as well as treatment, may favorably alter the outcomes.

SUMMARY

ICI and CAR T cell therapy have improved cancer-related outcomes; however, they both are associated with potentially therapy-limiting cardiotoxicity. Cardio-oncologists are required to play an important role in patient selection, pretherapy cardiovascular optimization, and prompt recognition and treatment of cardiotoxicity.

A T-cell-redirecting bispecific G-protein-coupled receptor class 5 member D x CD3 antibody to treat multiple myeloma

T-cell-mediated approaches have shown promise in myeloma treatment. However, there are currently a limited number of specific myeloma antigens that can be targeted, and multiple myeloma (MM) remains an incurable disease. G-protein-coupled receptor class 5 member D (GPRC5D) is expressed in MM and smoldering MM patient plasma cells. Here, we demonstrate that GPRC5D protein is present on the surface of MM cells and describe JNJ-64407564, a GPRC5DxCD3 bispecific antibody that recruits CD3+ T cells to GPRC5D+ MM cells and induces killing of GPRC5D+ cells. In vitro, JNJ-64407564 induced specific cytotoxicity of GPRC5D+ cells with concomitant T-cell activation and also killed plasma cells in MM patient samples ex vivo. JNJ-64407564 can recruit T cells and induce tumor regression in GPRC5D+ MM murine models, which coincide with T-cell infiltration at the tumor site. This antibody is also able to induce cytotoxicity of patient primary MM cells from bone marrow, which is the natural site of this disease. GPRC5D is a promising surface antigen for MM immunotherapy, and JNJ-64407564 is currently being evaluated in a phase 1 clinical trial in patients with relapsed or refractory MM (NCT03399799).

Short Time to Market and Forward Planning Will Enable Cell Therapies to Deliver R&D Pipeline Value

There is considerable industry excitement about the curative potential of cell and gene therapies, but significant challenges remain in designing cost-effective treatments that are accessible globally. We have taken a modeling-based approach to define the cost and value drivers for cell therapy assets during pharmaceutical drug development. We have created a model development program for a lentiviral modified ex vivo autologous T cell therapy for Oncology indications. Using internal and external benchmarks, we have estimated the total out-of-pocket cost of development for an Oncology cell therapy asset from target identification to filing of marketing application to be $500-600 million. Our model indicates that both clinical and Chemistry Manufacturing and Controls (CMC) cost of development for cell therapies are higher due to unique considerations of ex vivo autologous cell therapies. We have computed a threshold revenue-generating patient number for our model asset that enables selection of assets that can address high unmet medical need and generate pipeline value. Using statistical approaches, we identified that short time to market (<5 years) and reduced commercial cost of goods (<$65,000 per dose) will be essential in developing competitive assets and we propose solutions to reduce both. We emphasize that teams must proactively plan alternate development scenarios with clear articulation of path to value generation and greater patient access. We recommend using a modeling-based approach to enable data driven go/no-go decisions during multigenerational cell therapy development.

A guide to cancer immunotherapy: from T cell basic science to clinical practice

The T lymphocyte, especially its capacity for antigen-directed cytotoxicity, has become a central focus for engaging the immune system in the fight against cancer. Basic science discoveries elucidating the molecular and cellular biology of the T cell have led to new strategies in this fight, including checkpoint blockade, adoptive cellular therapy and cancer vaccinology. This area of immunological research has been highly active for the past 50 years and is now enjoying unprecedented bench-to-bedside clinical success. Here, we provide a comprehensive historical and biological perspective regarding the advent and clinical implementation of cancer immunotherapeutics, with an emphasis on the fundamental importance of T lymphocyte regulation. We highlight clinical trials that demonstrate therapeutic efficacy and toxicities associated with each class of drug. Finally, we summarize emerging therapies and emphasize the yet to be elucidated questions and future promise within the field of cancer immunotherapy.

Clinical CAR-T Cell and Oncolytic Virotherapy for Cancer Treatment

Immunotherapy has recently garnered success with the induction of clinical responses in tumors, which are traditionally associated with poor outcomes. Chimeric antigen receptor T (CAR-T) cells and oncolytic viruses (OVs) have emerged as promising cancer immunotherapy agents. Herein, we provide an overview of the current clinical status of CAR-T cell and OV therapies. While preclinical studies have demonstrated curative potential, the benefit of CAR-T cells and OVs as single-agent treatments remains limited to a subset of patients. Combinations of different targeted therapies may be required to achieve efficient, durable responses against heterogeneous tumors, as well as the microenvironment. Using a combinatorial approach to take advantage of the unique features of CAR-T cells and OVs with other treatments can produce additive therapeutic effects. This review also discusses ongoing clinical evaluations of these combination strategies for improved outcomes in treatment of resistant malignancies.

Actors on the Scene: Immune Cells in the Myeloma Niche

Two mechanisms are involved in the immune escape of cancer cells: the immunoediting of tumor cells and the suppression of the immune system. Both processes have been revealed in multiple myeloma (MM). Complex interactions between tumor plasma cells and the bone marrow (BM) microenvironment contribute to generate an immunosuppressive milieu characterized by high concentration of immunosuppressive factors, loss of effective antigen presentation, effector cell dysfunction, and expansion of immunosuppressive cell populations, such as myeloid-derived suppressor cells, regulatory T cells and T cells expressing checkpoint molecules such as programmed cell death 1. Considering the great immunosuppressive impact of BM myeloma microenvironment, many strategies to overcome it and restore myeloma immunosurveillance have been elaborated. The most successful ones are combined approaches such as checkpoint inhibitors in combination with immunomodulatory drugs, anti-monoclonal antibodies, and proteasome inhibitors as well as chimeric antigen receptor (CAR) T cell therapy. How best to combine anti-MM therapies and what is the optimal timing to treat the patient are important questions to be addressed in future trials. Moreover, intratumor MM heterogeneity suggests the crucial importance of tailored therapies to identify patients who might benefit the most from immunotherapy, reaching deeper and more durable responses.

Designing high affinity target-binding peptides to HLA-E: a key membrane antigen of multiple myeloma

Multiple myeloma (MM) is a plasma cell malignancy that is currently incurable. Finding new targets and designing drugs are crucial for the treatment of MM. The two datasets (GSE6691 and GSE39754) are used to screen highly expressed antigen on MM cells. HLA-E was an ideal target for it was a hub gene, and also located in one of the key clusters. Highly expression of HLA-E mRNA on MM cells was also confirmed by real-time qPCR testing the MM patients' samples in Shengjing hospital. Crystal structure of HLA-E was obtained from Protein Data Bank (PDB ID: 3CDG) which was used to design targeting peptides with Molecular Operating Environment software. By analyzing interaction between CD94/NKG2A and HLA-E, a peptide with twelve amino acids was screened as a model peptide. Peptides library was constructed by randomly replaced non-key amino acid. Peptide-protein docking method was used to identify high affinity peptides. PEPTIDE 1-3 and model peptide were synthesized and identified the affinity to HLA-E by flow cytometer and confocal laser microscopy. At last, PEPTIDE3 (NALDEYCEDKNR) was found with the highest affinity. Taking all, HLA-E is a new treatment target, and PEPTIDE 3 is an ideal high affinity target-binding peptide candidate.

Immunotherapy in Hematologic Malignancies: Emerging Therapies and Novel Approaches

Immunotherapy is extensively investigated for almost all types of hematologic tumors, from preleukemic to relapse/refractory malignancies. Due to the emergence of technologies for target cell characterization, antibody design and manufacturing, as well as genome editing, immunotherapies including gene and cell therapies are becoming increasingly elaborate and diversified. Understanding the tumor immune microenvironment of the target disease is critical, as is reducing toxicity. Although there have been many successes and newly FDA-approved immunotherapies for hematologic malignancies, we have learned that insufficient efficacy due to disease relapse following treatment is one of the key obstacles for developing successful therapeutic regimens. Thus, combination therapies are also being explored. In this review, immunotherapies for each type of hematologic malignancy will be introduced, and novel targets that are under investigation will be described.

Monoclonal antibodies as an addition to current myeloma therapy strategies

INTRODUCTION

Immunotherapy has emerged as a major class in the therapeutic arsenal of multiple myeloma. Cell-based immunotherapy (CAR T-cells) and monoclonal antibody-based immunotherapy (naked monoclonal antibodies, antibody-drug conjugates, and bispecific T-cell engagers) are the two cornerstones of this novel approach for myeloma patients. Among numerous targets evaluated in the previous decade; CD38, SLAMF7, and, more recently, BCMA stand as the most promising.

AREAS COVERED

This review presents and discusses the currently available data regarding monoclonal antibodies in the treatment of multiple myeloma.

EXPERT OPINION

Anti-CD38-naked monoclonal antibodies have become a standard-of-care in multiple myeloma, greatly improving the depth and duration of response when combined with conventional therapy. Elotuzumab is approved in the relapse setting in combination with pomalidomide and maybe an interesting option in patients whose disease became refractory to anti-CD38 monoclonal antibodies. Anti-BCMA drug conjugates and bispecific T-cell engager antibodies are promising new molecules in the multiple myeloma armamentarium.

Engineering Tolerance toward Allogeneic CAR-T Cells by Regulation of MHC Surface Expression with Human Herpes Virus-8 Proteins

Allogeneic, off-the-shelf (OTS) chimeric antigen receptor (CAR) cell therapies have the potential to reduce manufacturing costs and variability while providing broader accessibility to cancer patients and those with other diseases. However, host-versus-graft reactivity can limit the durability and efficacy of OTS cell therapies requiring new strategies to evade adaptive and innate-immune responses. Human herpes virus-8 (HHV8) maintains infection, in part, by evading host T and natural killer (NK) cell attack. The viral K3 gene encodes a membrane-tethered E3 ubiquitin ligase that discretely targets major histocompatibility complex (MHC) class I components, whereas K5 encodes a similar E3 ligase with broader specificity, including MHC-II and the MHC-like MHC class I polypeptide-related sequence A (MIC-A)- and sequence B (MIC-B)-activating ligands of NK cells. We created γ-retroviruses encoding K3 and/or K5 transgenes that efficiently transduce primary human T cells. Expression of K3 or K5 resulted in dramatic downregulation of MHC-IA (human leukocyte antigen [HLA]-A, -B, and -C) and MHC class II (HLA-DR) cell-surface expression. K3 expression was sufficient for T cells to resist exogenously loaded peptide-MHC-specific cytotoxicity, as well as recognition in one-way allogeneic mixed lymphocyte reactions. Further, in immunodeficient mice engrafted with allogeneic T cells, K3-transduced T cells selectively expanded in vivo. Ectopic K5 expression in MHC class I^-, MIC-A⁺/B⁺ K562 cells also reduced targeting by primary NK cells. Coexpression of K3 in prostate stem cell antigen (PSCA)-directed, inducible MyD88/CD40 (iMC)-enhanced CAR-T cells did not impact cytotoxicity, T cell growth, or cytokine production against HPAC pancreatic tumor target cells, whereas K5-expressing cells showed a modest reduction in interleukin (IL)-2 production without effect on cytotoxicity. Together, these results support application of these E3 ligases to advance development of OTS CAR-T cell products.

Quantitative PCR methodology with a volume-based unit for the sophisticated cellular kinetic evaluation of chimeric antigen receptor T cells

Although the cellular kinetics of chimeric antigen receptor T (CAR T) cells are expressed in units of copies/μg gDNA, this notation carries the risk of misrepresentation owing to dramatic changes in blood gDNA levels after lymphocyte-depleting chemotherapy and rapid expansion of CAR T cells. Therefore, we aimed to establish a novel qPCR methodology incorporating a spike-in calibration curve that expresses cellular kinetics in units of copies/μL blood, as is the case for conventional pharmacokinetic studies of small molecules and other biologics. Dog gDNA was used as an external control gene. Our methodology enables more accurate evaluation of in vivo CAR T-cell expansion than the conventional approach; the unit “copies/μL blood” is therefore more appropriate for evaluating cellular kinetics than the unit “copies/μg gDNA.” The results of the present study provide new insights into the relationship between cellular kinetics and treatment efficacy, thereby greatly benefiting patients undergoing CAR T-cell therapy.

Development of CAR T Cells Expressing a Suicide Gene Plus a Chimeric Antigen Receptor Targeting Signaling Lymphocytic-Activation Molecule F7

Chimeric antigen receptors (CARs) are fusion proteins that contain antigen-recognition domains and T cell signaling domains. Signaling lymphocytic-activation molecule F7 (SLAMF7) is a promising target for CAR T cell therapies of the plasma cell malignancy multiple myeloma (MM) because SLAMF7 is expressed by MM but not normal nonhematopoietic cells. We designed CARs targeting SLAMF7. We transduced human T cells with anti-SLAMF7 CARs containing either CD28 or 4-1BB costimulatory domains. T cells expressing CD28-containing CARs or 4-1BB-containing CARs recognized SLAMF7 in vitro. SLAMF7-specific cytokine release was higher for T cells expressing CARs with CD28 versus 4-1BB domains. In murine solid tumor and disseminated tumor models, anti-tumor activity of T cells was superior with CD28-containing CARs versus 4-1BB-containing CARs. Because of SLAMF7 expression on some normal leukocytes, especially natural killer cells that control certain viral infections, the inclusion of a suicide gene with an anti-SLAMF7 CAR is prudent. We designed a construct with a CD28-containing anti-SLAMF7 CAR and a suicide gene. The suicide gene encoded a dimerization domain fused to a caspase-9 domain. T cells expressing the anti-SLAMF7 CAR plus suicide-gene construct specifically recognized SLAMF7 in vitro and eliminated tumors from mice. T cells expressing this construct were eliminated on demand by administering the dimerizing agent AP1903 (rimiducid).

Immunotherapeutic and Targeted Approaches in Multiple Myeloma

The multiple myeloma (MM) therapeutic landscape has evolved significantly with the approval of numerous novel agents, including next generation proteasome inhibitors (PIs), immunomodulatory agents (IMIDs), and monoclonal antibodies (MoABs) targeting CD38 and SLAMF7. While these discoveries have led to an unprecedented improval in patient outcomes, the disease still remains incurable. Immunotherapeutic approaches have shown substantial promise in recent studies of chimeric antigen receptor T-cell (CAR T-cell) therapy, bispecific antibodies, and antibody drug conjugates targeting B-cell maturation antigen (BCMA). This review will highlight these novel and targeted therapies in MM, with particular focus on PIs, IMIDs, MoAb and BCMA-directed immunotherapy.

Model-Based Cellular Kinetic Analysis of Chimeric Antigen Receptor-T Cells in Humans

Chimeric antigen receptor (CAR)-T cell therapy has achieved considerable success in treating B-cell hematologic malignancies. However, the challenges of extending CAR-T therapy to other tumor types, particularly solid tumors, remain appreciable. There are substantial variabilities in CAR-T cellular kinetics across CAR-designs, CAR-T products, dosing regimens, patient responses, disease types, tumor burdens, and lymphodepletion conditions. As a "living drug," CAR-T cellular kinetics typically exhibit four distinct phases: distribution, expansion, contraction, and persistence. The cellular kinetics of CAR-T may correlate with patient responses, but which factors determine CAR-T cellular kinetics remain poorly defined. Herein, we developed a cellular kinetic model to retrospectively characterize CAR-T kinetics in 217 patients from 7 trials and compared CAR-T kinetics across response status, patient populations, and tumor types. Based on our analysis results, CAR-T cells exhibited a significantly higher cell proliferation rate and capacity but a lower contraction rate in patients who responded to treatment. CAR-T cells proliferate to a higher degree in hematologic malignancies than in solid tumors. Within the assessed dose ranges (10⁷ -10⁹ cells), CAR-T doses were weakly correlated with CAR-T cellular kinetics and patient response status. In conclusion, the developed CAR-T cellular kinetic model adequately characterized the multiphasic CAR-T cellular kinetics and supported systematic evaluations of the potential influencing factors, which can have significant implications for the development of more effective CAR-T therapies.

Conventional T cell therapies pave the way for novel Treg therapeutics

Approaches to harness the immune system to alleviate disease have become remarkably sophisticated since the crude, yet impressively-effective, attempts using live bacteria in the late 1800s. Recent evidence that engineered T cell therapy can deliver durable results in patients with cancer has spurred frenzied development in the field of T cell therapy. The myriad approaches include an innumerable variety of synthetic transgenes, multiplex gene-editing, and broader application to diseases beyond cancer. In this article, we review the preclinical studies and over a decade of clinical experience with engineered conventional T cells that have paved the way for translating engineered regulatory T cell therapies.

Pharmacology of Chimeric Antigen Receptor-Modified T Cells

Cell-based immunotherapies using T cells that are engineered to express a chimeric antigen receptor (CAR-T cells) are an effective treatment option for several B cell malignancies. Compared with most drugs, CAR-T cell products are highly complex, as each cell product is composed of a heterogeneous mixture of millions of cells. The biodistribution and kinetics of CAR-T cells, following administration, are unique given the ability of T cells to actively migrate as well as replicate within the patient. CAR-T cell therapies also have multiple mechanisms of action that contribute to both their antitumor activity and their toxicity. This review provides an overview of the unique pharmacology of CAR-T cells, with a focus on CD19-targeting and B cell maturation antigen (BCMA)-targeting CAR-T cells.

Multiple Myeloma: An Overview of the Current and Novel Therapeutic Approaches in 2020

The survival rate of multiple myeloma (MM) patients has drastically increased recently as a result of the wide treatment options now available. Younger patients truly benefit from these innovations as they can support more intensive treatment, such as autologous stem cell transplant or multiple drug association (triplet, quadruplet). The emergence of immunotherapy allowed new combinations principally based on monoclonal anti-CD38 antibodies for these patients. Still, the optimal induction treatment has not been found yet. While consolidation is still debated, maintenance treatment is now well acknowledged to prolong survival. Lenalidomide monotherapy is the only drug approved in that setting, but many innovations are expected. Older patients, now logically named not transplant-eligible, also took advantage of these breakthrough innovations as most of the recent drugs have a more acceptable safety profile than previous cytotoxic agents. For this heterogenous subgroup, geriatric assessment has become an essential tool to identify frail patients and provide tailored strategies. At relapse, options are now numerous, especially for patients who were not treated with lenalidomide, or not refractory at least. Concerning lenalidomide refractory patients, approved combinations are lacking, but many trials are ongoing to fill that space. Moreover, innovative therapeutics are increasingly being developed with modern immunotherapy, such as chimeric antigen receptor T-cells (CAR-T cells), bispecific antibodies, or antibody-drug conjugates. For now, these treatments are usually reserved to heavily pre-treated patients with a poor outcome. MM drug classes have tremendously extended from historical alkylating agents to current dominant associations with proteasome inhibitors, immunomodulatory agents, and monoclonal anti-CD38/anti SLAMF7 antibodies. Plus, in only a couple of years, several new classes will enter the MM armamentarium, such as cereblon E3 ligase modulators (CELMoDs), selective inhibitors of nuclear export, and peptide-drug conjugates. Among the questions that will need to be answered in the years to come is the position of these new treatments in the therapeutic strategy, as well as the role of minimal residual disease-driven strategies which will be a key issue to elucidate. Through this review, we chose to enumerate and comment on the most recent advances in MM therapeutics which have undergone major transformations over the past decade.

Treatment of Multiple Myeloma Using Chimeric Antigen Receptor T Cells with Dual Specificity

Chimeric antigen receptor (CAR) T-cell therapy has shown remarkable successes in fighting B-cell leukemias/lymphomas. Promising response rates are reported in patients treated with B-cell maturation antigen (BCMA) CAR T cells for multiple myeloma. However, responses appear to be nondurable, highlighting the need to expand the repertoire of multiple myeloma-specific targets for immunotherapy and to generate new CAR T cells. Here, we developed a "dual-CAR" targeting two multiple myeloma-associated antigens and explored its safety and efficacy. To reduce the "off-target" toxicity, we used the recognition of paired antigens that were coexpressed by the tumor to induce efficient CAR T-cell activation. The dual-CAR construct presented here was carefully designed to target the multiple myeloma-associated antigens, taking into consideration the distribution of both antigens on normal human tissues. Our results showed that the CD138/CD38-targeted dual CAR (dCAR138-38) elicited a potent anti-multiple myeloma response both in vitro and in vivo NSG mice transplanted with a multiple myeloma cell line and treated with dCAR138-38 showed median survival of 97 days compared with 31 days in the control group treated with mock-lymphocytes. The dCAR138-38 showed increased specificity toward cells expressing both targeted antigens compared with single-antigen-expressing cells and low activity toward primary cells from healthy tissues. Our findings indicated that the dCAR138-38 may provide a potent and safe alternative therapy for patients with multiple myeloma.

[Human cells for therapeutics purpose: State of the art]

Patient-derived induced pluripotent stem cells as well as human embryonic stem cells are pluripotent and their derivation has been used for the understanding of numerous diseases. Currently they are also used for the treatment of neurologic disorders such as Parkinson disease or cardiac disorders. Gene therapy has been successful for the treatment of hemophilia A and B, hemoglobinopathies and immunodeficiencies. Hemopoietic stem cell transplantation is a well-accepted therapeutic strategy for Leukemias, whereas CAR-T cells is a new promising approach even for lymphomas and myeloma.

Multiple myeloma: the (r)evolution of current therapy and a glance into future

Over the past 20 years, the regulatory approval of several novel agents to treat multiple myeloma (MM) has prolonged median patient survival from 3 to 8-10 years. Increased understanding of MM biology has translated to advances in diagnosis, prognosis, and response assessment, as well as informed the development of targeted and immune agents. Here we provide an overview of the recent progress in MM, and highlight research areas of greatest promise to further improve patient outcome in the future.

New drugs in early development for treating multiple myeloma: all that glitters is not gold

INTRODUCTION

The last twenty years have introduced new therapeutic agents for multiple myeloma (MM); these include proteasome inhibitors (PIs), immunomodulatory drugs (IMDs) and monoclonal antibodies (mAbs). However, MM remains incurable, hence there is an unmet need for new agents for the treatment of advanced refractory disease. New agents could also be used in early lines to achieve improved, more sustained remission.

AREAS COVERED

We review the most promising agents investigated in early-phase trials for the treatment of MM and provide an emphasis on new agents directed against well-known targets (new PIs, IMDs and anti-CD38 mAbs). Drugs that work through distinct and numerous mechanisms of action (e.g. pro-apoptotic agents and tyrosine kinase inhibitors) and innovative immunotherapeutic approaches are also described. The paper culminates with our perspective on therapeutic approaches on the horizon for this disease.

EXPERT OPINION

IMD iberdomide and the export protein inhibitor selinexor demonstrated efficacy in heavily pretreated patients who had no other therapeutic options. We expect that immunotherapy with anti-BCMA BTEs and ADCs will revolutionize the approach to treating the early stages of the disease. Data on venetoclax in t(11;14)-positive patients may pave the way for personalized therapy. Not all new agents under early clinical evaluation will be investigated in regulatory phase III trials; one of the most important challenges is to identify those that could make a difference.

Melflufen for relapsed and refractory multiple myeloma

INTRODUCTION

The overall survival of patients with multiple myeloma has improved with the advent of novel agents; however, multiple myeloma remains incurable. Combinations of standard-of-care agents such as immunomodulators, proteasome inhibitors, and anti-CD38 monoclonal antibodies are increasingly used in earlier lines of therapy. Patients with disease that is refractory to multiple novel agents represent a population with high unmet medical need and for whom therapies with new mechanisms of action could be beneficial. Melphalan flufenamide (melflufen) has demonstrated encouraging activity in patients with relapsed and refractory multiple myeloma.

AREAS COVERED

This review provides an overview of the mechanism of action of melflufen, a first-in-class peptide-drug conjugate that targets aminopeptidases and rapidly delivers alkylating agents into tumor cells. It reviews key Phase I and II clinical trial data for melflufen in combination with dexamethasone as well as in triplet combinations with daratumumab or bortezomib. The safety profile of melflufen, which is characterized primarily by clinically manageable hematologic adverse events, is described.

EXPERT OPINION

Melflufen has potential to fill a gap in the myeloma treatment landscape by providing a new mechanism of action with clinically meaningful efficacy and a favorable safety profile in patients refractory to multiple novel agents.

Multiple myeloma current treatment algorithms

The treatment of multiple myeloma (MM) continues to evolve rapidly with arrival of multiple new drugs, and emerging data from randomized trials to guide therapy. Along the disease course, the choice of specific therapy is affected by many variables including age, performance status, comorbidities, and eligibility for stem cell transplantation. In addition, another key variable that affects treatment strategy is risk stratification of patients into standard and high-risk MM. High-risk MM is defined by the presence of t(4;14), t(14;16), t(14;20), gain 1q, del(17p), or p53 mutation. In this paper, we provide algorithms for the treatment of newly diagnosed and relapsed MM based on the best available evidence. We have relied on data from randomized controlled trials whenever possible, and when appropriate trials to guide therapy are not available, our recommendations reflect best practices based on non-randomized data, and expert opinion. Each algorithm has been designed to facilitate easy decision-making for practicing clinicians. In all patients, clinical trials should be considered first, prior to resorting to the standard of care algorithms we outline.

Anti-CD19 CAR-T cells: Digging in the dark side of the golden therapy

The unprecedented technological advances in genetic engineering have resulted in the advent of the very promising chimeric antigen receptor (CAR)-T cell therapy. Based on the striking outcomes of clinical trials, the first two commercial CAR-T cell products, tisagenlecleucel and axicabtagene ciloleucel, have been approved in both the United States and Europe for the treatment of patients with highly aggressive CD19-positive hematological malignancies. Despite the initial remarkable responses many patients finally relapse, implying the presence of resistance mechanisms. In this review, we describe the limitations and resistance mechanisms to anti-CD19 CAR-T cells and address potential strategies to overcome CAR-T cell barriers.

Melflufen: A Peptide-Drug Conjugate for the Treatment of Multiple Myeloma

Despite the availability of new therapies that have led to improved outcomes for patients with multiple myeloma, most patients will eventually relapse. With triplet and even quadruplet combination therapies becoming standard in the first and second line, many patients will have few treatment options after second-line treatment. Melflufen (melphalan flufenamide) is a first-in-class peptide-drug conjugate (PDC) that targets aminopeptidases and rapidly releases alkylating agents into tumor cells. Once inside the tumor cells, melflufen is hydrolyzed by peptidases to release alkylator molecules, which become entrapped. Melflufen showed anti-myeloma activity in myeloma cells that were resistant to bortezomib and the alkylator melphalan. In early phase studies (O-12-M1 and HORIZON [OP-106]), melflufen plus dexamethasone has demonstrated encouraging clinical activity and a manageable safety profile in heavily pretreated patients with relapsed/refractory multiple myeloma, including those with triple-class refractory disease and extramedullary disease. The Phase III OCEAN study (OP-104) is further evaluating melflufen plus dexamethasone in patients with relapsed/refractory multiple myeloma. The safety profile of melflufen is characterized primarily by clinically manageable hematologic adverse events. Melflufen, with its novel mechanism of action, has the potential to provide clinically meaningful benefits to patients with relapsed/refractory multiple myeloma, including those with high unmet needs.

CAR T cell therapies for patients with multiple myeloma

Despite several therapeutic advances over the past decade, multiple myeloma (MM) remains largely incurable, indicating a need for new treatment approaches. Chimeric antigen receptor (CAR) T cell therapy works by mechanisms distinct from those of other MM therapies and involves the modification of patient or donor T cells to target specific cell-surface antigens. B cell maturation antigen (BCMA) is expressed only on plasma cells, a small subset of B cells and MM cells, which makes it a suitable target antigen for such therapies. At the time of writing, data from >20 clinical trials involving anti-BCMA CAR T cells have demonstrated that patients with relapsed and/or refractory MM can achieve objective responses. These early investigations have been instrumental in demonstrating short-term safety and efficacy; however, most patients do not have disease remission lasting >18 months. Attempts to reduce or delay the onset of relapsed disease are underway and include identifying additional CAR T cell target antigens and methods of enhancing BCMA expression on MM cells. Engineering CAR T cells to enhance both the activity and safety of treatment continues to be a promising avenue for improvement. In this Review we summarize data from clinical trials that have been carried out to date, describe novel antigens that could be targeted in the future, and highlight potential future innovations that could enhance the efficacy and/or reduce the toxicities associated with CAR T cell therapies.

Emerging immunotherapies in multiple myeloma

Despite considerable advances in treatment approaches in the past two decades, multiple myeloma remains an incurable disease. Treatments for myeloma continue to evolve with many emerging immunotherapies. The first immunotherapy used to treat hematologic cancers, including multiple myeloma, was an allogeneic stem cell transplant. In the mid-2000s, immunomodulatory drugs thalidomide, lenalidomide, and subsequently pomalidomide were proven to be effective in multiple myeloma and substantially improved survival. The next wave of immunotherapies for multiple myeloma included the monoclonal antibodies daratumumab and elotuzumab, which were approved by the Food and Drug Administration in 2015. Subsequently, a variety of immunotherapies have been developed for multiple myeloma, including chimeric antigen receptor T cells, bispecific antibodies, antibody drug conjugates, and checkpoint inhibitors. Many of these emerging treatments target the B cell maturation antigen, which is expressed on plasma cells, although several other novel receptors are also being studied. This review summarizes the evidence of these various immunotherapies, their mechanism of action, and data from clinical trials regarding the treatments' safety and efficacy.

BCMA-targeting approaches for treatment of multiple myeloma

Recent advances in treatment modalities have led to improved survival in patients with multiple myeloma (MM). However, despite these, MM remains an incurable disease. Many MM patients relapse through and become refractory to current treatment strategies or are intolerant due to toxicities arising from therapy. As such, novel strategies addressing new targets are crucial in improving care for MM patients. BCMA has emerged as a rationale therapeutic target for treatment of MM as it is preferentially expressed in mature B-lymphocytes and plasma cells with the overexpression and activation of BCMA via its ligands associated with the disease progression in multiple myeloma. Given the high expression of BCMA in malignant Plasma cells compared to those from normal healthy volunteers, targeting BCMA should reduce risks of on-target off-tumor toxicities. The main BCMA-targeting approaches currently used for treatment of MM include: 1) chimeric antigen receptor (CAR) T-cell therapy; 2) bi- and multi- specific antibodies; and 3) monoclonal antibodies and their drug conjugates. This review will outline these therapeutic agents and present their emerging clinical data.

CAR T cells targeting options in the fight against multiple myeloma

INTRODUCTION

Multiple myeloma (MM) is a hematological malignancy in which patients present with bone marrow infiltration of clonal terminally-differentiated plasma cells. Monoclonal protein in the serum and/or urine is frequently detected. Over the past decade, important progress has been made in the comprehension of disease biology and treatment personalization. Much work has been put into the development of chimeric antigen receptor (CAR) gene-modified T-cell therapy thought to be a promising therapeutic option for pluritreated patients with refractory MM.

EVIDENCE ACQUISITION

We performed an analysis of clinical trials registered at the international repository clinicaltrials.gov using "CAR" OR "CAR T" AND "multiple myeloma" as search terms to understand what were the antigens targeted by CAR T strategies and what was the trade-off of their exploitation. The search retrieved a list of 103 trials that was manually filtered to eliminate follow-up and observational or not-pertinent trials.

EVIDENCE SYNTHESIS

Most studies employed anti-BCMA targeting either alone (62/94; 66%), or in combination with a second target (12/94; 13%). The second target most studied was SLAMF7 (CD319) explored by 4/94 (4%) clinical trials. Other antigens investigated and described here include: CD44v6, CD38, CD138, MUC1, CD56, CD19, Igk light chain, Lewis Y, CD229 and GPRC5D.

CONCLUSIONS

Targeting an appropriate antigen(s) is the key to both safety and efficacy of CAR T approaches in MM as there is dearth of tumor-specific antigens. Most antigens tested are merely enriched on MM cells. Working with tumor-enriched antigens requires careful assessment of the balance between harm (toxicity) and benefit (disease eradication) to the patient. This review provides an up-to-date overview of the avenues that are being explored.

TEPI-2 and UBI: designs for optimal immuno-oncology and cell therapy dose finding with toxicity and efficacy

Conventional dose finding designs in oncology drug development target on the identification of the maximum tolerated dose (MTD), with the assumption that the MTD has the most potential of clinical activity among those identified tolerable dose levels. However, immuno-oncology (I-O) and cell therapy area, may lack dose-efficacy monotonicity, posing significant challenges in the statistical designs for dose finding trials. A desirable design should empower the trial to identify the right dose level with tolerable toxicity and acceptable efficacy. Such dose is called as optimal biological dose (OBD), which is more appropriate to be considered as the primary objective of the first-in-human trial in I-O and cell therapy than MTD. We propose two model-assisted designs in this setting: the toxicity and efficacy probability interval-2 (TEPI-2) design and the utility-based interval (UBI) design that incorporate the toxicity and efficacy outcomes simultaneously and identify a dose that has high probability of acceptable efficacy with manageable toxicity. The proposed designs can generate decision tables before trial starts to facilitate practical and easy-to-implement applications. Through simulation studies, our proposed novel designs demonstrate superior performance in accuracy, efficiency, and safety. Additionally, they can reduce the number of patients and shorten clinical development timeline. We also illustrate the advantages of proposed methods by redesigning a CAR T-cell therapy phase I clinical trial for multiple myeloma and summarize our recommendations in the discussion section.

The microenvironment in myeloma

PURPOSE OF REVIEW

The aim of the review is to describe recent advances in our understanding of how multiple myeloma interacts with its cellular and molecular neighbours in the bone marrow microenvironment, and how this may provide targets for prognostication and prevention.

RECENT FINDINGS

The bone marrow microenvironment in myeloma is beginning to yield targets that are amenable to therapy. A number of trials demonstrate some clinical efficacy in heavily pretreated disease. The challenge remains for how and when these therapeutic interventions are of particular benefit early in disease progression.

SUMMARY

Multiple myeloma is rarely curable and its interactions with the bone marrow microenvironment are evident. However, separating cause from effect remains a challenge. We propose that targeting specific niches within the bone marrow will yield therapies that have the potential for significant benefit in myeloma and may facilitate earlier intervention to disrupt an environment that is permissive for myeloma progression.

Chimeric Antigen Receptor T-cell Therapy for Multiple Myeloma

Relapsed/refractory multiple myeloma (MM) remains a significant clinical challenge, despite a wide array of approved therapeutic agents. Immunotherapy offers an advantage in this setting. Chimeric antigen receptor (CAR) modified T-cells have transformed care for patients with hematologic malignancies. CAR-T cells targeting CD-19 B-cell lymphoma cells have shown prominent activity in lymphoma and acute lymphoblastic leukemia. Recently, the CAR-T cell platform for MM demonstrated therapeutic benefit. Hence, it is rapidly progressing. The most commonly tested target for MM is the B-cell maturation antigen. Complexities involved in the generation and use of CAR-T cells for MM include the identification of appropriate target antigens that are specific, and tumor type restricted, in addition to the optimization of CAR constructs to mitigate toxicities including cytokine release syndrome. CAR-T cells hold immense promise as a therapeutic modality for the treatment of MM. In this article, we provide an updated review of clinical trials of MM-specific CAR-T cells.

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.

CAR T Cell Therapy for Solid Tumors: Bright Future or Dark Reality?

Chimeric antigen receptor (CAR) T cell therapy has garnered significant excitement due to its success for hematological malignancies in clinical studies leading to the US Food and Drug Administration (FDA) approval of three CD19-targeted CAR T cell products. In contrast, the clinical experience with CAR T cell therapy for solid tumors and brain tumors has been less encouraging, with only a few patients achieving complete responses. Clinical and preclinical studies have identified multiple "roadblocks," including (1) a limited array of targetable antigens and heterogeneous antigen expression, (2) limited T cell fitness and survival before reaching tumor sites, (3) an inability of T cells to efficiently traffic to tumor sites and penetrate physical barriers, and (4) an immunosuppressive tumor microenvironment. Herein, we review these challenges and discuss strategies that investigators have taken to improve the effector function of CAR T cells for the adoptive immunotherapy of solid tumors.

T-cell phenotypes associated with effective CAR T-cell therapy in postinduction vs relapsed multiple myeloma

T cells from patients early in myeloma therapy exhibit better fitness for CAR T manufacturing than those from relapsed/refractory patients. CAR T cells may be more effective if manufactured from patients before onset of relapsed/refractory disease.

Cell-based artificial APC resistant to lentiviral transduction for efficient generation of CAR-T cells from various cell sources

Background

Adoptive cell therapy with chimeric antigen receptor T cells (CAR-T) has become a standard treatment for patients with certain aggressive B cell malignancies and holds promise to improve the care of patients suffering from numerous other cancers in the future. However, the high manufacturing cost of CAR-T cell therapies poses a major barrier to their broader clinical application. Among the key cost drivers of CAR-T production are single-use reagents for T cell activation and clinical-grade viral vector. The presence of variable amounts of contaminating monocytes in the starting material poses an additional challenge to CAR-T manufacturing, since they can impede T cell stimulation and transduction, resulting in manufacturing failure.

Methods

We created K562-based artificial antigen-presenting cells (aAPC) with genetically encoded T cell stimulation and costimulation that represent an inexhaustible source for T cell activation. We additionally disrupted endogenous expression of the low-density lipoprotein receptor (LDLR) on these aAPC (aAPC-ΔLDLR) using CRISPR-Cas9 gene editing nucleases to prevent inadvertent lentiviral transduction and avoid the sink effect on viral vector during transduction. Using various T cell sources, we produced CD19-directed CAR-T cells via aAPC-ΔLDLR-based activation and tested their in vitro and in vivo antitumor potency against B cell malignancies.

Results

We found that lack of LDLR expression on our aAPC-ΔLDLR conferred resistance to lentiviral transduction during CAR-T production. Using aAPC-ΔLDLR, we achieved efficient expansion of CAR-T cells even from unpurified starting material like peripheral blood mononuclear cells or unmanipulated leukapheresis product, containing substantial proportions of monocytes. CD19-directed CAR-T cells that we produced via aAPC-ΔLDLR-based expansion demonstrated potent antitumor responses in preclinical models of acute lymphoblastic leukemia and B-cell lymphoma.

Conclusions

Our aAPC-ΔLDLR represent an attractive approach for manufacturing of lentivirally transduced T cells that may be simpler and more cost efficient than currently available methods.

Bispecific Chimeric Antigen Receptor T Cell Therapy for B Cell Malignancies and Multiple Myeloma

Chimeric antigen receptor (CAR) modified T cell therapy offers a targeted immunotherapeutic approach to patients with refractory hematological malignancies. This technology is most advanced in B cell malignancies and multiple myeloma and is rapidly evolving as more data become available regarding clinical efficacy and response durability. Despite excellent initial response rates with single antigen targeting CARs, failure to respond to therapy and relapse due to target antigen downregulation remain clinical challenges. To mitigate immunophenotypic selective pressures, simultaneous dual antigen targeting with bispecific CAR T cells or multiple administration of different populations of CAR T cells may prevent relapse by addressing one resistance mechanism attributed to antigenic loss. This article will review recently published data on the use of dual targeting with CAR T cells from early phase clinical trials aimed at treating B cell malignancies and multiple myeloma.

The (Neutrophils + Monocyte)/Lymphocyte Ratio Is an Independent Prognostic Factor for Progression-Free Survival in Newly Diagnosed Multiple Myeloma Patients Treated With BCD Regimen

Objective

Bortezomib is one of the important drugs that have made breakthrough progress in multiple myeloma (MM) in the past 10 years. However, the heterogeneity of its efficacy makes it difficult to predict the risk of disease progression. The purpose of this study is to determine the prognostic significance of the (neutrophils + monocytes)/lymphocytes ratio (NMLR) in newly diagnosed MM patients who received BCD regimen therapy in terms of progression-free survival (PFS).

Methods

A total of 150 patients who fulfilled the International Myeloma Working Group (IMWG) criteria were enrolled in the study retrospectively. The prognostic value of NMLR was evaluated by 150 patients with MM who were treated with BCD (bortezomib + cyclophosphamide + dexamethasone) regimen therapy. NMLR was calculated by the ratio of (neutrophils + monocyte) to lymphocytes. According to receiver operating characteristic curves, the cutoff value was 1.90. The patients were divided into high NMLR group (H-NMLR, NMLR ≥1.90) and low NMLR group (L-NMLR, NMLR <1.90). The clinical characteristics, treatment responses and PFS of the two groups were analyzed.

Results

The median age of the patients was 61 years. Fifty-five (36.67%) patients showed lower NMLR at initial diagnosis. Although NMLR was unable to discriminate prognosis in ISS stage I/II patients, interestingly, the addition of NMLR to the ISS further defined prognosis particularly in stage III. Low-NMLR group who achieved early immune reconstruction significantly higher than that of the high-NMLR group (P < 0.001). NMLR value was 1.98 ± 1.02 for the patients who achieved early immune reconstruction, which was 3.26 ± 2.52 for the patients without immune reconstruction (P < 0.05). Compared with the H-NMLR group, the levels of β2-microglobulin, serum creatinine and calcium were lower, and the very good partial response or better (≥VGPR) ratio was higher in L-NMLR group. The L-NMLR group experienced a superior median PFS compared with the H-NMLR group (24.0 versus 15.5 months; P < 0.001). In addition, several other prognostic factors of PFS were estimated, including the high-risk cytogenetics, β2-microglobulin and the depth of treatment response 3 months after treatment with BCD regimen. Moreover, NMLR was an independent predictor of PFS including non-high risk cytogenetics (0.587; P = 0.031).

Conclusion

In patients with newly diagnosed MM undergoing BCD regimen, the NMLR <1.90 was an independent prognostic factor for PFS as well as early immune reconstruction and lower disease burden.

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.

Defining an Optimal Dual-Targeted CAR T-cell Therapy Approach Simultaneously Targeting BCMA and GPRC5D to Prevent BCMA Escape-Driven Relapse in Multiple Myeloma

CAR T-cell therapy for multiple myeloma (MM) targeting B-cell maturation antigen (TNFRSF17; BCMA) induces high overall response rates; however, relapse occurs commonly. Implicated in relapse is a reservoir of MM if cells lacking sufficient BCMA surface expression (antigen escape). We demonstrate that simultaneous targeting of an additional antigen-here, G protein-coupled receptor class-C group-5 member-D (GPRC5D)-can prevent BCMA escape-mediated relapse in a model of MM. To identify an optimal approach, we compare subtherapeutic doses of different forms of dual-targeted cellular therapy. These include (1) parallel-produced and pooled mono-targeted CAR T-cells, (2) bicistronic constructs expressing distinct CARs from a single vector, and (3) a dual-scFv "single-stalk" CAR design. When targeting BCMA-negative disease, bicistronic and pooled approaches had the highest efficacy, whereas for dual-antigen-expressing disease, the bicistronic approach was more efficacious than the pooled approach. Mechanistically, expressing two CARs on a single cell enhanced the strength of CAR T-cell/target cell interactions.

Chimeric antigen receptor T-cell therapies: Optimising the dose

Lymphocytes such as T-cells can be genetically transduced to express a synthetic chimeric antigen receptor (CAR) that re-directs their cytotoxic activity against a tumour-expressed antigen of choice. Autologous (patient-derived) CAR T-cells have been licensed to treat certain relapsed and refractory B-cell malignancies, and numerous CAR T-cell products are in clinical development. As living gene-modified cells, CAR T-cells exhibit unique pharmacokinetics, typically proliferating within the recipient during the first 14 days after administration before contracting in number, and sometimes exhibiting long-term persistence. The relationship between CAR T-cell dose and exposure is highly variable, and may be influenced by CAR design, patient immune function at the time of T-cell harvest, phenotype of the CAR T-cell product, disease burden, lymphodepleting chemotherapy and subsequent immunomodulatory therapies. Recommended CAR T-cell doses are typically established for a specific product and indication, although for some products, stratification of dose based on disease burden may mitigate toxicity while maintaining efficacy. Re-evaluation of CAR T-cell dosing may be necessary following changes to the lymphodepleting regimen, for different disease indications, and following significant manufacturing changes, if product comparability cannot be demonstrated. Dose escalation trials have typically employed 3 + 3 designs, although this approach has limitations, and alternative phase I trial designs may facilitate the identification of CAR T-cell doses that strike an optimal balance of safety, efficacy and manufacturing feasibility.