Investigational immunotherapeutics for B-cell malignancies

HLA-DR expression in melanoma: from misleading therapeutic target to potential immunotherapy biomarker

Since the advent of anti-PD1 immune checkpoint inhibitor (ICI) immunotherapy, cutaneous melanoma has undergone a true revolution with prolonged survival, as available 5-year updates for progression-free survival and overall survival demonstrate a durable clinical benefit for melanoma patients receiving ICI. However, almost half of patients fail to respond to treatment, or relapse sooner or later after the initial response to therapy. Little is known about the reasons for these failures. The identification of biomarkers seems necessary to better understand this resistance. Among these biomarkers, HLA-DR, a component of MHC II and abnormally expressed in certain tumor types including melanoma for unknown reasons, seems to be an interesting marker. The aim of this review, prepared by an interdisciplinary group of experts, is to take stock of the current literature on the potential interest of HLA-DR expression in melanoma as a predictive biomarker of ICI outcome.

Anti-CD 19 and anti-CD 20 CAR-modified T cells for B-cell malignancies: a systematic review and meta-analysis

Chimeric antigen receptor modified T cells targeting CD19 and CD20 have shown activity in Phase I, II trials of patients with hematological malignancies. We conducted a systematic review and meta-analysis of all published clinical trials studying the role of efficacy as well as safety of CD-19 and CD-20 chimeric antigen receptor-T therapy for B-cell hematologic malignancies. A total of 16 studies with 195 patients were identified. The pooled analysis showed an overall response rate of 61% (118/195) with complete response of 42% (81/195) and partial response of 19% (37/195). Major adverse events were cytokine release syndrome 33%, neurotoxicity 33% and B-cell aplasia 54%. Collectively, the results indicate encouraging response in relapsed/refractory B lymphoma and leukemia, especially in acute lymphoblastic leukemia (ALL) patients.

Development of Engineered T Cells Expressing a Chimeric CD16-CD3ζ Receptor to Improve the Clinical Efficacy of Mogamulizumab Therapy Against Adult T-Cell Leukemia

PURPOSE

Mogamulizumab (Mog), a humanized anti-CC chemokine receptor 4 (CCR4) mAb that mediates antibody-dependent cellular cytotoxicity (ADCC) using FcγR IIIa (CD16)-expressing effector cells, has recently been approved for treatment of CCR4-positive adult T-cell leukemia (ATL) in Japan. However, Mog failure has sometimes been observed in patients who have accompanying chemotherapy-associated lymphocytopenia. In this study, we examined whether adoptive transfer of artificial ADCC effector cells combined with Mog would overcome this drawback.

EXPERIMENTAL DESIGN

We lentivirally gene-modified peripheral blood T cells from healthy volunteers and ATL patients expressing the affinity-increased chimeric CD16-CD3ζ receptor (cCD16ζ-T cells). Subsequently, we examined the ADCC effect mediated by those cCD16ζ-T cells in the presence of Mog against ATL tumor cells both in vitro and in vivo

RESULTS

cCD16ζ-T cells derived from healthy donors killed in vitro Mog-opsonized ATL cell line cells (n = 7) and primary ATL cells (n = 4) depending on both the number of effector cells and the dose of the antibody. cCD16ζ-T cells generated from ATL patients (n = 3) also exerted cytocidal activity in vitro against Mog-opsonized autologous ATL cells. Using both intravenously disseminated model (n = 5) and subcutaneously inoculated model (n = 4), coadministration of Mog and human cCD16ζ-T cells successfully suppressed tumor growth in xenografted immunodeficient mice, and significantly prolonged their survival (P < 0.01 and P = 0.02, respectively).

CONCLUSIONS

These data strongly suggest clinical feasibility of the novel combined adoptive immunotherapy using cCD16ζ-T cells and Mog for treatment of aggressive ATL, particularly in patients who are ineligible for allogeneic hematopoietic stem cell transplantation. Clin Cancer Res; 22(17); 4405-16. ©2016 AACR.

Recombinant human CD19L-sTRAIL effectively targets B cell precursor acute lymphoblastic leukemia

Patients with B cell precursor acute lymphoblastic leukemia (BPL) respond well to chemotherapy at initial diagnosis; however, therapeutic options are limited for individuals with BPL who relapse. Almost all BPL cells express CD19, and we recently cloned the gene encoding a natural ligand of the human CD19 receptor (CD19L). We hypothesized that fusion of CD19L to the soluble extracellular domain of proapoptotic TNF-related apoptosis-inducing ligand (sTRAIL) would markedly enhance the potency of sTRAIL and specifically induce BPL cell apoptosis due to membrane anchoring of sTRAIL and simultaneous activation of the CD19 and TRAIL receptor (TRAIL-R) apoptosis signaling pathways. Here, we demonstrate that recombinant human CD19L-sTRAIL was substantially more potent than sTRAIL and induced apoptosis in primary leukemia cells taken directly from BPL patients. CD19L-sTRAIL effectively targeted and eliminated in vivo clonogenic BPL xenograft cells, even at femtomolar-picomolar concentrations. In mice, CD19L-sTRAIL exhibited a more favorable pharmacokinetic (PK) profile than sTRAIL and was nontoxic at doses ranging from 32 fmol/kg to 3.2 pmol/kg. CD19L-sTRAIL showed potent in vivo antileukemic activity in NOD/SCID mouse xenograft models of relapsed and chemotherapy-resistant BPL at nontoxic fmol/kg dose levels. Together, these results suggest that recombinant human CD19L-sTRAIL has clinical potential as a biotherapeutic agent against BPL.

Tumor-antigen-binding bispecific antibodies for cancer treatment

Bi- and multispecific antibody derivatives (bsAbs) can be considered as the next generation of targeted biologics for cancer therapy. The general concept of bsAbs is a physical connection of recombinant antibody-derived entities with at least two binding specificities. This generates bsAbs that bind at least two antigens or epitopes, thus altering their binding functionalities and specificities in comparison to "normal" antibodies. Most bsAbs are produced as recombinant proteins, either as large IgG-like proteins that contain Fc regions, or as smaller entities with multiple antigen-binding regions but without Fc. Application of bsAbs in experimental cancer therapy currently includes molecules that bind different cell surface proteins to achieve more complete blockage of proliferative or angiogenesis-associated pathways. This approach of blocking more than one pathway component, or to simultaneously hit complementing pathways, also may limit potential escape mechanisms of cancer cells. BsAbs also are applied in the clinic as vehicles to deliver immune effector cells and/or cytokines to tumors.

Pediatric posttransplant relapsed/refractory B-precursor acute lymphoblastic leukemia shows durable remission by therapy with the T-cell engaging bispecific antibody blinatumomab

We report on posttransplant relapsed pediatric patients with B-precursor acute lymphoblastic leukemia with no further standard of care therapy who were treated with the T-cell engaging CD19/CD3-bispecific single-chain antibody construct blinatumomab on a compassionate use basis. Blast load was assessed prior to, during and after blinatumomab cycle using flow cytometry to detect minimal residual disease, quantitative polymerase chain reaction for rearrangements of the immunoglobulin or T-cell receptor genes, and bcr/abl mutation detection in one patient with Philadelphia chromosome-positive acute lymphoblastic leukemia. Blinatumomab was administered as a 4-week continuous intravenous infusion at a dosage of 5 or 15 μg/m(2)/day. Nine patients received a total of 18 cycles. Four patients achieved complete remission after the first cycle of treatment; 2 patients showed a complete remission from the second cycle after previous reduction of blast load by chemotherapy. Three patients did not respond, of whom one patient proceeded to a second cycle without additional chemotherapy and again did not respond. Four patients were successfully retransplanted in molecular remission from haploidentical donors. After a median follow up of 398 days, the probability of hematologic event-free survival is 30%. Major toxicities were grade 3 seizures in one patient and grade 3 cytokine release syndrome in 2 patients. Blinatumomab can induce molecular remission in pediatric patients with posttransplant relapsed B-precursor acute lymphoblastic leukemia and facilitate subsequent allogeneic hematopoietic stem cell transplantation from haploidentical donor with subsequent long-term leukemia-free survival.

Gene-modified human α/β-T cells expressing a chimeric CD16-CD3ζ receptor as adoptively transferable effector cells for anticancer monoclonal antibody therapy

The central tumoricidal activity of anticancer monoclonal antibodies (mAb) is exerted by FcγR IIIa (CD16)-expressing effector cells in vivo via antibody-dependent cell-mediated cytotoxicity (ADCC), as observed for natural killer (NK) cells. In practice, chemotherapy-induced leukopenia and exhaustion of NK cells resulting from ADCC often hamper the clinical efficacy of cancer treatment. To circumvent this drawback, we examined in vivo the feasibility of T cells, gene-modified to express a newly generated affinity-matured (158V/V) chimeric CD16-CD3ζ receptor (cCD16ζ-T cells), as a transferable alternative effector for cancer mAb therapy. cCD16ζ-T cells were readily expandable in ex vivo culture using anti-CD2/CD3/CD28 beads and recombinant human interleukin-2 (rhIL-2), and they successfully displayed ADCC-mediated tumoricidal activity in vitro. During ADCC, ligation of opsonized cancer cells to the introduced cCD16ζ-T cells stimulated the effector cells to produce proinflammatory cytokines and release toxic granules through the activation of the Nuclear factor of activated T cells (NFAT) pathway after phosphorylation of the CD3ζ chain. In parallel, these stimulated cCD16ζ-T cells transiently proliferated and differentiated into effector memory T cells. In contrast, NK cells activated by rhIL-2 displayed similar ADCC activity, but failed to proliferate. Human cCD16ζ-T cells infused concomitantly with anti-CD20 mAb synergistically inhibited the growth of disseminated Raji cells, a CD20(+) lymphoma cell line, in immunodeficient mice, whereas similarly infused rhIL-2-treated NK cells survived for a shorter time and displayed less effective tumor suppression. Our findings strongly suggest the clinical feasibility of cCD16ζ-T cells as adoptively transferable ADCC effector cells that could potentially enhance the clinical responses mediated by currently available anticancer mAbs.

Primary cutaneous B-cell lymphomas: part II. Therapy and future directions

The choice of therapy for primary cutaneous B-cell lymphoma (PCBCL) relies on correct histopathologic classification and the exclusion of systemic disease. In part II of this continuing medical education article, we will review the available therapies for the different types of PCBCL. Primary cutaneous follicle center lymphoma (PCFCL) and primary cutaneous marginal zone lymphoma (PCMZL) are indolent tumors with an excellent prognosis. They are managed similarly with local therapy, such as radiotherapy or surgical excision, for isolated disease and observation for asymptomatic multifocal presentations. Relapses are common in both PCFCL and PCMZL, but overall survival remains excellent. Primary cutaneous diffuse large B-cell lymphoma (both leg type and other) has a much poorer prognosis than indolent PCBCL, and it often requires an aggressive approach with radiation therapy and/or multiagent chemotherapy. Investigational approaches hold promise for the treatment of these malignancies, particularly primary cutaneous diffuse large B-cell lymphoma.

The future role of monoclonal antibody therapy in childhood acute leukaemias

Leukaemia is the single most common childhood malignancy. With modern treatment regimens, survival in acute lymphoblastic leukaemia (ALL) approaches 90%. Only about 70% of children with acute myeloid leukaemia (AML) achieve long term survival. Patients who relapse have a dismal prognosis. Novel therapeutic approaches are needed to improve treatment outcomes in newly-diagnosed patients with a poor prognosis and for patients with relapsed/refractory disease that have limited treatment options. One promising approach in treating haematological malignancies has been the use of monoclonal antibodies to target cell surface antigens expressed on malignant cells. Most success with monoclonal antibody therapy in the treatment of haematological malignancies has come in the setting of adult B-cell non-Hodgkin lymphoma with the addition of the anti-CD20 monoclonal antibody rituximab to standard treatment regimens. In order to further advance treatment of haematological malignancies, novel monoclonal antibodies continue to be developed that target a variety of cell surface antigens. Several antibodies continue to be investigated in childhood leukaemias. This review will discuss the development of monoclonal antibodies that target a variety of cell surface antigens for the treatment of childhood ALL and the use of the anti-CD33 antibody gemtuzumab ozogamicin in the treatment of childhood AML.

Immunotherapy for B-Cell Neoplasms using T Cells expressing Chimeric Antigen Receptors: From antigen choice to clinical implementation

Immunotherapy with T cells expressing chimeric antigen receptors (CAR) is being evaluated as a potential treatment for B-cell neoplasms. In recent clinical trials it has shown promising results. As the number of potential candidate antigens expands, the choice of suitable target antigens becomes more challenging to design studies and to assess optimal efficacy of CAR. Careful evaluation of candidate target antigens is required to ensure that T cells expressing CAR will preferentially kill malignant cells with a minimal toxicity against normal tissues. B cells express specific surface antigens that can theoretically act as targets for CAR design. Although many of these antigens can stimulate effective cellular immune responses in vivo, their implementation in clinical settings remains a challenge. Only targeted B-cell antigens CD19 and CD20 have been tested in clinical trials. This article reviews exploitable B cell surface antigens for CAR design and examines obstacles that could interfere with the identification of potentially useful cellular targets.

Update on novel monoclonal antibodies and immunoconjugates for the treatment of lymphoproliferative disorders

The year 1997 was pivotal in lymphoma research, as it was the year that the US FDA approved rituximab. Rituximab significantly altered clinical management and outcomes of patients with B-cell malignancies. Despite a high initial response rate, the majority of patients subsequently develop variable degrees of therapeutic resistance to rituximab. Research attempting to understand the mechanisms of rituximab resistance and potential ways to overcome them has given rise to the development of novel targeted immunotherapeutics. This article will update the readers on advances in bioengineering of monoclonal antibodies and immunoconjugates that target CD20, as well as other surface antigens. Some additional novel immunotherapeutics, including small modular immunopharmaceuticals, bispecific monoclonal antibodies, T-cell engaging antibodies and immunoconjugates, will also be discussed.

Targeting siglecs--a novel pharmacological strategy for immuno- and glycotherapy

The immune system must be tightly held in check to avoid bystander tissue damage as well as autoreactivity caused by overwhelming immune reactions. A novel family of immunoregulatory, carbohydrate-binding receptors, the Siglecs (sialic acid binding immunoglobulin-like lectins), has received particular attention in light of their capacity to mediate cell death, anti-proliferative effects and to regulate a variety of cellular activities. Siglec receptors are mainly expressed on leukocytes in a cell type-specific and differentiation-dependent manner. Siglecs might potentially be exploited as targets of novel immune- and glycotherapeutics for cell-directed therapies in autoimmune and allergic diseases, as well as in haematologic malignancies. Here we present novel insights on structural and functional characteristics, expression patterns and evolutionary aspects of Siglecs and their ligands. Pharmacological strategies using Siglec agonistic cross-linking therapeutics, such as monoclonal or engineered antibodies, intravenous immunoglobulin (IVIG), or glycomimetics are discussed. Modulation of immune responses by targeting Siglecs using agonistic or antagonistic therapeutics may have important clinical implications and may pave the way for novel pharmacological avenues for the treatment of autoimmune and allergic diseases or for tumor immunotherapy.

The future of anti-CD20 monoclonal antibodies: are we making progress?

The anti-CD20 monoclonal antibody (mAb) rituximab has revolutionized the treatment of B-cell malignancies. This unprecedented success has not only substantially changed the mindset of the clinical community about the ability of mAb to improve outcomes but has catalyzed the interest in the pharmaceutical industry to develop the next generation of anti-CD20 mAbs. Since the introduction of rituximab 15 years ago, we have learned much about the potential mechanisms underlying the therapeutic efficacy of anti-CD20 mAbs. In parallel, many novel anti-CD20 mAbs have entered the clinic, each designed with modifications to structure aimed at further improving efficacy. On review of the newer generation of anti-CD20 mAbs entering clinical trials, it appears that the link between the novel mechanistic insights and the development of these next-generation anti-CD20 mAbs is unclear. As we move into an era of personalized medicine, it will become increasingly important for us to develop closer links between the emerging mechanistic insights and the clinical development, to further enhance the potency of anti-CD20 mAbs beyond that achieved with rituximab.

CD22 EXON 12 deletion as a pathogenic mechanism of human B-precursor leukemia

Here, we report that primary leukemic cells from infants with newly diagnosed B-precursor leukemia express a truncated and functionally defective CD22 coreceptor protein that is unable to transmit apoptotic signals because it lacks most of the intracellular domain, including the key regulatory signal transduction elements and all of the cytoplasmic tyrosine residues. Expression of this structurally and functionally abnormal CD22 protein is associated with a very aggressive in vivo growth of patients' primary leukemia cells causing disseminated overt leukemia in SCID mice. The abnormal CD22 coreceptor is encoded by a profoundly aberrant mRNA arising from a splicing defect that causes the deletion of exon 12 (c.2208-c.2327) (CD22ΔE12) and results in a truncating frameshift mutation. The splicing defect is associated with multiple homozygous mutations within a 132-bp segment of the intronic sequence between exons 12 and 13. These mutations cause marked changes in the predicted secondary structures of the mutant CD22 pre-mRNA sequences that affect the target motifs for the splicing factors hnRNP-L, PTB, and PCBP that are up-regulated in infant leukemia cells. Forced expression of the mutant CD22ΔE12 protein in transgenic mice perturbs B-cell development, as evidenced by B-precursor/B-cell hyperplasia, and corrupts the regulation of gene expression, causing reduced expression levels of several genes with a tumor suppressor function. We further show that CD22ΔE12-associated unique gene expression signature is a discriminating feature of newly diagnosed infant leukemia patients. These striking findings implicate CD22ΔE12 as a previously undescribed pathogenic mechanism in human B-precursor leukemia.

Safety and immunotoxicity assessment of immunomodulatory monoclonal antibodies

Most therapeutic monoclonal antibodies (mAbs) licensed for human use or in clinical development are indicated for treatment of patients with cancer and inflammatory/autoimmune disease and as such, are designed to directly interact with the immune system. A major hurdle for the development and early clinical investigation of many of these immunomodulatory mAbs is their inherent risk for adverse immune-mediated drug reactions in humans such as infusion reactions, cytokine storms, immunosuppression and autoimmunity. A thorough understanding of the immunopharmacology of a mAb in humans and animals is required to both anticipate the clinical risk of adverse immunotoxicological events and to select a safe starting dose for first-in-human (FIH) clinical studies. This review summarizes the most common adverse immunotoxicological events occurring in humans with immunomodulatory mAbs and outlines non-clinical strategies to define their immunopharmacology and assess their immunotoxic potential, as well as reduce the risk of immunotoxicity through rational mAb design. Tests to assess the relative risk of mAb candidates for cytokine release syndrome, innate immune system (dendritic cell) activation and immunogenicity in humans are also described. The importance of selecting a relevant and sensitive toxicity species for human safety assessment in which the immunopharmacology of the mAb is similar to that expected in humans is highlighted, as is the importance of understanding the limitations of the species selected for human safety assessment and supplementation of in vivo safety assessment with appropriate in vitro human assays. A tiered approach to assess effects on immune status, immune function and risk of infection and cancer, governed by the mechanism of action and structural features of the mAb, is described. Finally, the use of immunopharmacology and immunotoxicity data in determining a minimum anticipated biologic effect Level (MABEL) and in the selection of safe human starting dose is discussed.