Targeting of B‐cell receptor signalling in B‐cell malignancies

Pharmacological agents that inhibit enzymes of the B‐cell receptor (BCR) pathway are of increasing importance in the treatment of B‐cell malignancies. These include inhibitors of Bruton tyrosine kinase (BTK), phosphatidylinositol 3‐kinase (PI3K), splenic tyrosine kinase and protein kinase Cβ. Two agents are already approved in the USA and Europe: ibrutinib, a BTK inhibitor, for the treatment of chronic lymphatic leukaemia (CLL), mantle cell lymphoma (MCL) and Waldenström's macroglobulinemia; and idelalisib, a PI3Kδ inhibitor, for the treatment of CLL and follicular lymphoma. In addition, the role of these drugs in diffuse large B‐cell lymphoma and marginal zone lymphoma is under investigation, as single agents and in combination with chemotherapy. In CLL, both ibrutinib and idelalisib have an established role as first‐line therapy in patients with del(17p), and in MCL, ibrutinib is a standard option for patients relapsing after chemoimmunotherapy. Unexpected toxicities have been encountered when combining these potent new agents with other drugs, including chemotherapy and lenalidomide, and based on this experience the risks and benefits of novel combinations must be evaluated carefully. In this review, we summarize the efficacy and safety results with these inhibitors and discuss novel combinations that are under study and the future role of BCR inhibitors in these disorders.     

Antibody‐based therapies in B‐cell lineage acute lymphoblastic leukaemia

Targeted therapies represent a major breakthrough in the treatment of adult acute lymphoblastic leukaemia (ALL). Because lymphoblastic leukaemia cells express a variety of specific antigens, those ones can serve as targets for monoclonal antibodies (MoAbs). Anti‐CD20 (rituximab), anti‐CD19 (blinatumomab, SAR3419), anti‐CD22 (epratuzumab, inotuzumab ozogamicin) and anti‐CD52 (alemtuzumab) have therefore been developed. Possible strategies even include recruitment of CD3 cytotoxic T cells (blinatumomab) or adoptive T‐cell therapy by gene transfer of CD19‐chimeric antigen receptors (CD19‐CARs). Recent data show that antibody‐based therapy is a highly promising treatment approach. However, optimal treatment approach still needs to be defined.     

Anti‐leukaemic activity of the TYK2 selective inhibitor NDI‐031301 in T‐cell acute lymphoblastic leukaemia

Activation of tyrosine kinase 2 (TYK2) contributes to the aberrant survival of T‐cell acute lymphoblastic leukaemia (T‐ALL) cells. Here we demonstrate the anti‐leukaemic activity of a novel TYK2 inhibitor, NDI‐031301. NDI‐031301 is a potent and selective inhibitor of TYK2 that induced robust growth inhibition of human T‐ALL cell lines. NDI‐031301 treatment of human T‐ALL cell lines resulted in induction of apoptosis that was not observed with the JAK inhibitors tofacitinib and baricitinib. Further investigation revealed that NDI‐031301 treatment uniquely leads to activation of three mitogen‐activated protein kinases (MAPKs), resulting in phosphorylation of ERK, SAPK/JNK and p38 MAPK coincident with PARP cleavage. Activation of p38 MAPK occurred within 1 h of NDI‐031301 treatment and was responsible for NDI‐031301‐induced T‐ALL cell death, as pharmacological inhibition of p38 MAPK partially rescued apoptosis induced by TYK2 inhibitor. Finally, daily oral administration of NDI‐031301 at 100 mg/kg bid to immunodeficient mice engrafted with KOPT‐K1 T‐ALL cells was well tolerated, and led to decreased tumour burden and a significant survival benefit. These results support selective inhibition of TYK2 as a promising potential therapeutic strategy for T‐ALL.     

Lymphotoxin‐β receptor in microenvironmental cells promotes the development of T‐cell acute lymphoblastic leukaemia with cortical/mature immunophenotype

Lymphotoxin‐mediated activation of the lymphotoxin‐β receptor (LTβR; LTBR) has been implicated in cancer, but its role in T‐cell acute lymphoblastic leukaemia (T‐ALL) has remained elusive. Here we show that the genes encoding lymphotoxin (LT)‐α and LTβ (LTA, LTB) are expressed in T‐ALL patient samples, mostly of the TAL/LMO molecular subtype, and in the TEL‐JAK2 transgenic mouse model of cortical/mature T‐ALL (Lta, Ltb). In these mice, expression of Lta and Ltb is elevated in early stage T‐ALL. Surface LTα₁β₂ protein is expressed in primary mouse T‐ALL cells, but only in the absence of microenvironmental LTβR interaction. Indeed, surface LT expression is suppressed in leukaemic cells contacting Ltbr‐expressing but not Ltbr‐deficient stromal cells, both in vitro and in vivo, thus indicating that dynamic surface LT expression in leukaemic cells depends on interaction with its receptor. Supporting the notion that LT signalling plays a role in T‐ALL, inactivation of Ltbr results in a significant delay in TEL‐JAK2‐induced leukaemia onset. Moreover, young asymptomatic TEL‐JAK2;Ltbr^?/? mice present markedly less leukaemic thymocytes than age‐matched TEL‐JAK2;Ltbr^+/+ mice and interference with LTβR function at this early stage delayed T‐ALL development. We conclude that LT expression by T‐ALL cells activates LTβR signalling in thymic stromal cells, thus promoting leukaemogenesis.     

Safety and efficacy of nelarabine in children and young adults with relapsed or refractory T‐lineage acute lymphoblastic leukaemia or T‐lineage lymphoblastic lymphoma: results of a phase 4 study

Nelarabine is an antineoplastic agent approved for the treatment of relapsed/refractory T‐lineage acute lymphoblastic leukaemia (T‐ALL) or T‐lineage acute lymphoblastic lymphoma (T‐LBL). The purpose of this phase 4, multicentre, single‐arm, observational, open‐label trial was to provide additional data on the safety and efficacy of nelarabine under licensed conditions of use in children and young adults ≤21 years of age. Patients (N = 28) had a mean ± standard deviation age of 11·5 ± 4·6 years; 71% were male and 61% had a diagnosis of T‐ALL. Adverse events (AEs) and treatment‐related AEs were experienced by 46% and 21%, respectively, and included few haematological AEs and no haematological serious AEs. Neurological AEs from one of four predefined categories (peripheral and central nervous systems, mental status change and uncategorized) were reported in four patients. There were no AE‐related treatment discontinuations/withdrawals. The overall response rate was 39.3%: complete response (CR), 35.7%; CR without full haematological recovery (CR*), 3.6%. Post‐treatment stem cell transplantation was performed for 46% of the cohort. Median overall survival (OS) was 3·35 months for non‐responders and not reached for responders (CR + CR*). The response rate, median OS, and safety profile of nelarabine in this disease setting and population were consistent with those reported previously.     

Increased regulatory T cells in acute lymphoblastic leukaemia patients

Introduction: Regulation in adaptive immune response balances a fine line that prevents instigation of self-damage or fall into unresponsiveness permitting abnormal cell growth. Mechanisms that keep this balance in check include regulatory T cells (Tregs). Tregs consist of a small but heterogeneous population, which may be identified by the phenotype, CD3+CD4+CD25+CD127?. The role of Tregs in pathogenesis of cancers is thus far supported by evidence of increased Tregs in various cancers and may contribute to poorer prognosis. Tregs may also be important in acute leukaemias.

Objective: A review of the literature on Tregs in acute leukaemias was conducted and Tregs were determined in B-cell acute lymphoblastic leukaemias (ALLs).

Results: Studies on Tregs in B-cell ALL are few and controversial. We observed a significantly increased percentage of Tregs (mean±SD, 9.72?±?3.79% vs. 7.05?±?1.74%; P?=?0.047) in the bone marrow/peripheral blood of ALL (n?=?17) compared to peripheral blood of normal controls (n?=?35). A positive trend between Tregs and age (R?=?0.474, P?=?0.055, n?=?17) implicates this factor of poor prognosis in B-cell ALL.

Discussion: Tregs in cancer are particularly significant in immunotherapy. The manipulation of the immune system to treat cancer has for a long time ignored regulatory mechanisms inducible or in place. In lymphoma studies, tumour-specific mechanisms that are unlike conventional methods in the induction of Tregs have been hypothesized. In addition, tumour-infiltrating Tregs may present different profiles from peripheral blood pictures. Tregs will continue to be dissected to reveal its mysteries and their impact on clinical significance.     

Salvage therapy with nelarabine,etoposide, and cyclophosphamide in relapsed/refractory paediatric T‐cell lymphoblastic leukaemia and lymphoma

A combination of 5 d of nelarabine (AraG) with 5 d of etoposide (VP) and cyclophosphamide (CPM) and prophylactic intrathecal chemotherapy was used as salvage therapy in seven children with refractory or relapsed T‐cell leukaemia or lymphoma. The most common side effects attributable to the AraG included Grade 2 and 3 sensory and motor neuropathy and musculoskeletal pain. Haematological toxicity was greater for the combination than AraG alone, although median time to neutrophil and platelet recovery was consistent with other salvage therapies. All patients had some response to the combined therapy and five of the seven went into complete remission after one or two courses of AraG/VP/CPM. Our experience supports the safety of giving AraG as salvage therapy in synchrony with etoposide and cyclophosphamide, although neurological toxicity must be closely monitored.     

Outcome for children and young people with Early T‐cell precursor acute lymphoblastic leukaemia treated on a contemporary protocol,UKALL 2003

We investigated the outcome for children and young people with Early T‐precursor acute lymphoblastic leukaemia (ETP‐ALL), a recently described poor prognosis sub‐group of T‐ALL, treated on a contemporary protocol, UKALL 2003. After a median follow‐up of 4 years and 10 months, the ETP sub‐group, representing 16% of T‐ALL patients, had non‐significantly inferior 5‐year event‐free survival (76·7% vs. 84·6%, P = 0·2) and overall survival (82·4% vs. 90·9%, P = 0·1), and a higher relapse rate (18·6% vs. 9·6%, P = 0·1) compared to typical T‐ALL. ETP‐ALL has an intermediate risk outcome, which does not warrant experimental treatment or first remission allogeneic transplant for the group universally.     

Donor‐derived CD19‐targeted T cell infusion induces minimal residual disease‐negative remission in relapsed B‐cell acute lymphoblastic leukaemia with no response to donor lymphocyte infusions after haploidentical haematopoietic stem cell transplantation

Relapse is a common cause of failure in patients with B‐cell acute lymphoblastic leukaemia (B‐ALL) after haploidentical haematopoietic stem cell transplantation (haplo‐HSCT), and non‐responders to donor lymphoblastic infusion after HSCT have a very poor prognosis. Although donor‐derived CD19‐directed chimeric antigen receptor‐modified (CAR) T cells can potentially cure leukaemia, their effectiveness and safety have not been confirmed in relapsed B‐ALL cases after haplo‐HSCT. Between January 2015 and January 2017, two and four patients each received one and two infusions of CAR T cells from haplo‐HSCT donors. Five (83·33%) achieved minimal residual disease (MRD)‐negative remission; one patient was discharged automatically without evaluation after developing severe thrombotic microangiopathies. Four of five responsive patients relapsed after 2–7 months, and one died of sepsis following MRD‐negative remission after a second infusion. None of the other second infusion recipients achieved a second complete remission. Five patients (83·33%) experienced eight courses of grade 1–3 cytokine release syndrome; two were treated with tocilizumab. Two (33·3%) and one patient developed grade 2 and 3 acute graft‐versus‐host disease (aGVHD), respectively; the former was controlled with glucocorticoids. Donor‐derived CAR T‐cell infusion seems be effective and safe for relapsed B‐ALL after haplo‐HSCT, although larger clinical studies are needed.     

Pharmacogenetic determinants of outcome in acute lymphoblastic leukaemia

Present day paediatric co-operative group acute lymphoblastic leukaemia (ALL) protocols cure approximately 80% of patients, a result achieved largely through the use of risk-stratified therapies that employ multiple chemotherapy agents. These risk-based therapies utilize host and leukaemia traits to select the most appropriate therapy. However, these risk-stratified approaches predict therapy response imperfectly and an important fraction of patients experience relapse or therapy-related toxicity. Pharmacogenetics, the study of genetic variations in drug-processing genes and individual responses to drugs, may enable the improved identification of patients at higher risk for either disease relapse or chemotherapy-associated side effects. While the impact of genetic variation in the thiopurine-S-methyltransferase gene on ALL treatment outcome and toxicity has been extensively studied, the role of other polymorphisms remains less well known. This review summarizes current research on the impact of genetic variation in drug-processing genes in paediatric ALL and reviews important methodological and statistical issues presently challenging the field of pharmacogenetics.     

Treatment of acute lymphoblastic leukaemia with the second generation of CD19 CAR‐T containing either CD28 or 4‐1BB

T cells modified with anti‐CD19 chimeric antigen receptor (CAR) containing either CD28 or 4‐1BB (also termed TNFRSF9, CD137) costimulatory signalling have shown great potential in the treatment of acute lymphoblastic leukaemia (ALL). However, the difference between CD28 and 4‐1BB costimulatory signalling in CAR‐T treatment has not been well elucidated in clinical trials. In this study, we treated 10 relapsed or refractory ALL patients with the second generation CD19 CAR‐T. The first 5 patients were treated with CD28‐CAR and the other 5 patients were treated with 4‐1BB CAR‐T. All the 10 patients were response‐evaluable. Three patients achieved complete remission and 1 patient with extramedullary disease achieved partial response after CD28‐CAR‐T treatment. In the 4‐1BB CAR‐T treatment group, 3 patients achieved complete remission. Furthermore, FLT‐3 ligand (FLT3LG) was highly correlated with response time and may serve as a prognosis factor. No severe adverse events were observed in these 10 treated patients. Our study showed that both CD28 CAR‐T and 4‐1BB CAR‐T both worked for response but they differed in response pattern (peak reaction time, reaction lasting time and reaction degree), adverse events, cytokine secretion and immune‐suppressive factor level.     

Very high frequencies of leukaemia‐initiating cells in precursor T‐acute lymphoblastic leukaemia may be obscured by cryopreservation

Eltrombopag is a thrombopoietin‐receptor agonist that stimulates platelet production and increases platelet counts in patients with chronic immune thrombocytopenia (ITP). This open‐label, single‐arm study evaluated consistency of response and safety following repeated intermittent dosing of eltrombopag 50 mg daily over 3 cycles (1 cycle = up to 6 weeks on therapy followed by up to 4 weeks off therapy). The primary endpoint was proportion of patients with a response (platelet count ≥50 × 10⁹/l and ≥2× baseline) in Cycle 1 who subsequently responded in Cycle 2 or 3. Fifty‐two of 65 evaluable patients (80%) responded in Cycle 1; these responding patients comprised the primary analysis population. Of these, 45/52 (87%) responded in Cycle 2 or 3 [95% confidence interval (CI), 74–94%] and 34/48 (71%; 95% CI, 56–83%) responded in both Cycles 2 and 3. Time to response was consistent, with >50% of responders responding by Day 8 in each cycle. Bleeding rates relative to baseline decreased by approximately 50% during each treatment cycle. The frequency or severity of adverse events, most commonly headache, did not increase over successive cycles. If a chronic ITP patient not requiring consistent therapy responds to short‐term eltrombopag, then subsequent courses of eltrombopag, as needed, are likely to be safe and effective.     

Aberrant T-cell antigen expression in B lymphoblastic leukaemia

B lymphoblastic leukaemia (B-ALL) cells are characterized by the expression of various B-cell antigens. Expression of T/Natural Killer-cell antigens, however, has rarely been reported in B-ALL (TAg+ B-ALL), and the significance of this aberrant antigen expression is unclear. We thus analysed the frequency of TAg+ B-ALL at our institution and investigated its significance in the context of immunophenotypes, cytogenetic/molecular findings, and prognosis. We reviewed 134 consecutive cases of B-ALL and found 18 cases (13·4%) of TAg+ B-ALL. The most common aberrant T-cell antigens expressed were CD2, CD5, and CD7 at equivalent rates (each in six cases), CD4 (two cases), and CD56 (three cases). Adverse cytogenetic abnormalities were seen in a significantly larger proportion of the TAg+ cases (72·2%) than the TAg- cases (32·2%; P = 0·003). Multivariate Cox-regression analysis showed that the risk of relapse over time was higher in the TAg+ cases, independent of high risk status (based on age and white blood cell count) and the presence of adverse cytogenetic abnormalities (hazard ratio = 2·256, P = 0·065). These findings suggest that T-cell antigen expression in B-ALL may be an independent predictor of poor prognosis, and a useful marker to identify patients at increased risk for relapse and for harbouring adverse cytogenetic abnormalities.     

Understanding the reconstitution of the B‐cell compartment in bone marrow and blood after treatment for B‐cell precursor acute lymphoblastic leukaemia

A better understanding of the reconstitution of the B‐cell compartment during and after treatment in B‐cell precursor acute lymphoblastic leukaemia (BCP ‐ALL ) will help to assess the immunological status and needs of post‐treatment BCP ‐ALL patients. Using 8‐colour flow cytometry and proliferation‐assays, we studied the composition and proliferation of both the B‐cell precursor (BCP ) population in the bone marrow (BM ) and mature B‐cell population in peripheral blood (PB ) during and after BCP ‐ALL therapy. We found a normal BCP differentiation pattern and a delayed formation of classical CD 38^dim‐naive mature B‐cells, natural effector B‐cells and memory B‐cells in patients after chemotherapy. This B‐cell differentiation/maturation pattern was strikingly similar to that during initial B‐cell development in healthy infants. Tissue‐resident plasma cells appeared to be partly protected from chemotherapy. Also, we found that the fast recovery of naive mature B‐cell numbers after chemotherapy was the result of increased de novo BCP generation, rather than enhanced B‐cell proliferation in BM or PB . These results indicate that post‐treatment BCP ‐ALL patients will eventually re‐establish a B‐cell compartment with a composition and B‐cell receptor repertoire similar to that in healthy children. Additionally, the formation of a new memory B‐cell compartment suggests that revaccination might be beneficial after BCP ‐ALL therapy.     

Clinical outcomes of a novel therapeutic vaccine with Tax peptide‐pulsed dendritic cells for adult T cell leukaemia/lymphoma in a pilot study

Adult T cell leukaemia/lymphoma (ATL) is a human T cell leukaemia virus type‐I (HTLV‐I)‐infected T cell malignancy with poor prognosis. We herein developed a novel therapeutic vaccine designed to augment an HTLV‐I Tax‐specific cytotoxic T lymphocyte (CTL) response that has been implicated in anti‐ATL effects, and conducted a pilot study to investigate its safety and efficacy. Three previously treated ATL patients, classified as intermediate‐ to high‐risk, were subcutaneously administered with the vaccine, consisting of autologous dendritic cells (DCs) pulsed with Tax peptides corresponding to the CTL epitopes. In all patients, the performance status improved after vaccination without severe adverse events, and Tax‐specific CTL responses were observed with peaks at 16–20 weeks. Two patients achieved partial remission in the first 8 weeks, one of whom later achieved complete remission, maintaining their remission status without any additional chemotherapy 24 and 19 months after vaccination, respectively. The third patient, whose tumour cells lacked the ability to express Tax at biopsy, obtained stable disease in the first 8 weeks and later developed slowly progressive disease although additional therapy was not required for 14 months. The clinical outcomes of this pilot study indicate that the Tax peptide‐pulsed DC vaccine is a safe and promising immunotherapy for ATL.     

Quantitative expression of thrombopoietin receptor on leukaemia cells from patients with acute myeloid leukaemia and acute lymphoblastic leukaemia

Using a non-isotopic ligand binding assay, we quantitatively examined the amount of human thrombopoietin (TPO) receptor (TPO-R) on leukaemia cells from 128 patients with acute myeloid leukaemia (AML) or acute lymphoblastic leukaemia (ALL). The TPO-R was expressed in 53 (47%) of 114 AML cases, and an in vitro treatment with TPO led to proliferation (stimulation index >1.5) of leukaemia cells in 13 (20%) of 66 AML cases examined. The TPO levels had no relation to the FAB classification except for FAB-M7 AML. All five FAB-M7 cases expressed TPO-R, and one of three FAB-M7 examined showed in vitro proliferative response to TPO. Although there was no significant correlation ( r  = 0.3125) between the amount of TPO-R and the proliferative response, all of the AML cases which showed the in vitro response had TPO-R expression. There was no relationship between TPO-R amount and CD phenotypes, or the amount of granulocyte-colony stimulating factor (G-CSF) receptor. TPO-R was also expressed in two (14%) of 14 cases of ALL, and only these two cases had in vitro proliferative response to TPO. One had only lymphoid antigens, and the other had both lymphoid and myeloid antigens. Our results suggest that some leukaemia cells express functionally active TPO-R.