Mesothelin-targeting T cell receptor fusion construct cell therapy in refractory solid tumors: phase 1/2 trial interim results.

The T cell receptor fusion construct (TRuC) gavocabtagene autoleucel (gavo-cel) consists of single-domain anti-mesothelin antibody that integrates into the endogenous T cell receptor (TCR) and engages the signaling capacity of the entire TCR upon mesothelin binding. Here we describe phase 1 results from an ongoing phase1/2 trial of gavo-cel in patients with treatment-refractory mesothelin-expressing solid tumors. The primary objectives were to evaluate safety and determine the recommended phase 2 dose (RP2D). Secondary objectives included efficacy. Thirty-two patients received gavo-cel at increasing doses either as a single agent (n = 3) or after lymphodepletion (LD, n = 29). Dose-limiting toxicities of grade 3 pneumonitis and grade 5 bronchioalveolar hemorrhage were noted. The RP2D was determined as 1 × 108 cells per m2 after LD. Grade 3 or higher pneumonitis was seen in 16% of all patients and in none at the RP2D; grade 3 or higher cytokine release syndrome occurred in 25% of all patients and in 15% at the RP2D. In 30 evaluable patients, the overall response rate and disease control rate were 20% (13% confirmed) and 77%, respectively, and the 6-month overall survival rate was 70%. Gavo-cel warrants further study in patients with mesothelin-expressing cancers given its encouraging anti-tumor activity, but it may have a narrow therapeutic window. ClinicalTrials.gov identifier: NCT03907852 .

Paediatric Strategy Forum for medicinal product development of chimeric antigen receptor T-cells in children and adolescents with cancer: ACCELERATE in collaboration with the European Medicines Agency with participation of the Food and Drug Administration.

The seventh multi-stakeholder Paediatric Strategy Forum focused on chimeric antigen receptor (CAR) T-cells for children and adolescents with cancer. The development of CAR T-cells for patients with haematological malignancies, especially B-cell precursor acute lymphoblastic leukaemia (BCP-ALL), has been spectacular. However, currently, there are scientific, clinical and logistical challenges for use of CAR T-cells in BCP-ALL and other paediatric malignancies, particularly in acute myeloid leukaemia (AML), lymphomas and solid tumours. The aims of the Forum were to summarise the current landscape of CAR T-cell therapy development in paediatrics, too identify current challenges and future directions, with consideration of other immune effector modalities and ascertain the best strategies to accelerate their development and availability to children. Although the effect is of limited duration in about half of the patients, anti-CD19 CAR T-cells produce high response rates in relapsed/refractory BCP-ALL and this has highlighted previously unknown mechanisms of relapse. CAR T-cell treatment as first- or second-line therapy could also potentially benefit patients whose disease has high-risk features associated with relapse and failure of conventional therapies. Identifying patients with very early and early relapse in whom CAR T-cell therapy may replace haematopoietic stem cell transplantation and be definitive therapy versus those in whom it provides a more effective bridge to haematopoietic stem cell transplantation is a very high priority. Development of approaches to improve persistence, either by improving T cell fitness or using more humanised/fully humanised products and co-targeting of multiple antigens to prevent antigen escape, could potentially further optimise therapy. Many differences exist between paediatric B-cell non-Hodgkin lymphomas (B-NHL) and BCP-ALL. In view of the very small patient numbers with relapsed lymphoma, careful prioritisation is needed to evaluate CAR T-cells in children with Burkitt lymphoma, primary mediastinal B cell lymphoma and other NHL subtypes. Combination trials of alternative targets to CD19 (CD20 or CD22) should also be explored as a priority to improve efficacy in this population. Development of CD30 CAR T-cell immunotherapy strategies in patients with relapsed/refractory Hodgkin lymphoma will likely be most efficiently accomplished by joint paediatric and adult trials. CAR T-cell approaches are early in development for AML and T-ALL, given the unique challenges of successful immunotherapy actualisation in these diseases. At this time, CD33 and CD123 appear to be the most universal targets in AML and CD7 in T-ALL. The results of ongoing or planned first-in-human studies are required to facilitate further understanding. There are promising early results in solid tumours, particularly with GD2 targeting cell therapies in neuroblastoma and central nervous system gliomas that represent significant unmet clinical needs. Further understanding of biology is critical to success. The comparative benefits of autologous versus allogeneic CAR T-cells, T-cells engineered with T cell receptors T-cells engineered with T cell receptor fusion constructs, CAR Natural Killer (NK)-cell products, bispecific T-cell engager antibodies and antibody-drug conjugates require evaluation in paediatric malignancies. Early and proactive academia and multi-company engagement are mandatory to advance cellular immunotherapies in paediatric oncology. Regulatory advice should be sought very early in the design and preparation of clinical trials of innovative medicines, for which regulatory approval may ultimately be sought. Aligning strategic, scientific, regulatory, health technology and funding requirements from the inception of a clinical trial is especially important as these are very expensive therapies. The model for drug development for cell therapy in paediatric oncology could also involve a 'later stage handoff' to industry after early development in academic hands. Finally, and very importantly, strategies must evolve to ensure appropriate ease of access for children who need and could potentially benefit from these therapies.

Synthetic T cell receptor-based lymphocytes for cancer therapy.

Chimeric antigen receptor (CAR) T cells have been remarkably successful in patients with hematological malignancies expressing the CD19 surface antigen, but such level of success is far from being replicated in solid tumors. Engineered T cell receptor (TCR) T cells targeting cancer antigens were first developed over two decades ago and represent an alternative adoptive T cell approach that has produced provocative clinical data in solid cancers. However, several factors may hinder this technology from realizing its full potential, including the need for HLA matching, HLA downregulation by cancer cells, the suppressive tumor microenvironment, and tissue liabilities resulting from targeting antigens shared with normal tissues. Efforts therefore continue to engineer enhanced versions of CAR T and TCR T therapies that can overcome current barriers. Furthermore, emergent novel TCR-based, HLA-unrestricted platforms may also provide unique tools that integrate the complexity of the TCR signaling cascade that can be applied to treat solid tumors. This article reviews the current state of development of TCR T cell approaches and discusses next generation improvements to overcome their current limitations.

What CAR Will Win the CD19 Race?

Adoptive transfer of T cells engineered with synthetic receptors is emerging as a new pillar in the treatment of cancer. The adoptive cell therapy furthest along in clinical development is the engineering of T cells to express chimeric antigen receptors (CAR) against the CD19 antigen. Several platforms have shown remarkable activity in patients with relapsed or refractory B-cell malignancies. In 2017, the FDA approved the first CAR T cell products tisagenlecleucel (Kymriah, Novartis) and axicabtagene ciloleucel (Yescarta, Gilead), and others are expected to follow shortly. Despite their activity, CAR T cell approaches have limitations that will need to be addressed, including excessive toxicity, relapses mediated via antigen escape, difficulties overcoming the suppressive tumor microenvironment, high manufacturing costs and retail prices, and patient access, among others. The CAR T cell product that better addresses those challenges will obtain a critical competitive advantage.

Tumorigenesis promotes Mdm4-S overexpression.

Disruption of the p53 tumor suppressor pathway is a primary cause of tumorigenesis. In addition to mutation of the p53 gene itself, overexpression of major negative regulators of p53, MDM2 and MDM4, also act as drivers for tumor development. Recent studies suggest that expression of splice variants of Mdm2 and Mdm4 may be similarly involved in tumor development. In particular, multiple studies show that expression of a splice variant of MDM4, MDM4-S correlates with tumor aggressiveness and can be used as a prognostic marker in different tumor types. However, in the absence of prospective studies, it is not clear whether expression of MDM4-S in itself is oncogenic or is simply an outcome of tumorigenesis. Here we have examined the role of Mdm4-S in tumor development in a transgenic mouse model. Our results suggest that splicing of Mdm4 does not promote tumor development and does not cooperate with other oncogenic insults to alter tumor latency or aggressiveness. We conclude that Mdm4-S overexpression is a consequence of splicing defects in tumor cells rather than a cause of tumor evolution.

Peripheral blood blast clearance is an independent prognostic factor for survival and response to acute myeloid leukemia induction chemotherapy.

In patients with acute myeloid leukemia (AML), rapid reduction of circulating blasts with induction chemotherapy may serve as an in vivo marker of chemosensitivity. We performed a retrospective analysis of 363 patients with untreated AML who received induction chemotherapy in order to determine the relationship between day of blast disappearance (DOBD) and complete remission (CR) rates, event-free survival (EFS), and overall survival (OS). DOBD ≤ 5 vs. >5 was identified as the most discriminating cutoff for OS. DOBD > 5 was observed in 35 patients (9.6%). The CR rate for patients with DOBD ≤ 5 vs. >5 was 74.0 and 28.6%, median EFS was 9.4 and 1.8 months, and median OS was 17.1 and 5.8 months, respectively (P < 0.001 for all). DOBD > 5 was independently associated with a lower CR rate and shorter EFS and OS (P < 0.001 for all). DOBD > 5 retained prognostic significance for EFS and OS when patients were stratified by cytogenetic risk group, de novo vs. secondary or therapy-related AML, European LeukemiaNet-based risk groups, and whether CR was achieved. We propose DOBD > 5 as a simple and early marker of disease resistance that identifies patients with poor prognosis who otherwise may not be identified with existing risk stratification systems. Am. J. Hematol. 91:1221-1226, 2016. © 2016 Wiley Periodicals, Inc.

hnRNP K Is a Haploinsufficient Tumor Suppressor that Regulates Proliferation and Differentiation Programs in Hematologic Malignancies.

hnRNP K regulates cellular programs, and changes in its expression and mutational status have been implicated in neoplastic malignancies. To directly examine its role in tumorigenesis, we generated a mouse model harboring an Hnrnpk knockout allele (Hnrnpk(+/-)). Hnrnpk haploinsufficiency resulted in reduced survival, increased tumor formation, genomic instability, and the development of transplantable hematopoietic neoplasms with myeloproliferation. Reduced hnRNP K expression attenuated p21 activation, downregulated C/EBP levels, and activated STAT3 signaling. Additionally, analysis of samples from primary acute myeloid leukemia patients harboring a partial deletion of chromosome 9 revealed a significant decrease in HNRNPK expression. Together, these data implicate hnRNP K in the development of hematological disorders and suggest hnRNP K acts as a tumor suppressor.

Loss of TRIM62 expression is an independent adverse prognostic factor in acute myeloid leukemia.

BACKGROUND: Tripartite motif (TRIM)-62 is a putative tumor suppressor gene whose role in leukemia is unknown. MATERIALS AND METHODS: We evaluated the effect of TRIM62 protein expression in patients with acute myeloid leukemia (AML). We used reverse-phase protein array methodology to determine TRIM62 levels in leukemia-enriched protein samples from 511 patients newly diagnosed with AML. RESULTS: TRIM62 levels in AML cells were significantly lower than in normal CD34-positive cells, suggesting that TRIM62 loss might be involved in leukemogenesis, but was not associated with specific karyotypic abnormalities or Nucleophosmin (NPM1), Fms-like Tyrosine Kinase-3 (FLT3), or rat sarcoma viral oncogene (RAS) mutational status. Low TRIM62 levels were associated with shorter complete remission duration and significantly shorter event-free and overall survival rates, particularly among patients with intermediate-risk cytogenetics. In that AML subgroup, age and TRIM62 levels were the most powerful independent prognostic factors for survival. TRIM62 protein levels further refined the risk associated with NPM1 and FLT3 mutational status. TRIM62 loss was associated with altered expression of proteins involved in leukemia stem cell homeostasis (ß-catenin and Notch), cell motility, and adhesion (integrin-ß3, ras-related C3 botulinum toxin substrate [RAC], and fibronectin), hypoxia (Hypoxia-inducible factor 1-alpha [HIF1α], egl-9 family hypoxia-inducible factor 1 [Egln1], and glucose-regulated protein, 78 kDa [GRP78]), and apoptosis (B-cell lymphoma-extra large (BclXL) and caspase 9). CONCLUSION: Low TRIM62 levels, consistent with a tumor suppressor role, represent an independent adverse prognostic factor in AML.

Dynamics of chronic myeloid leukemia response to dasatinib, nilotinib, and high-dose imatinib.

Treatment with the tyrosine kinase inhibitor imatinib is the standard of care for newly diagnosed patients with chronic myeloid leukemia. In recent years, several second-generation inhibitors - such as dasatinib and nilotinib - have become available: these promise to overcome some of the mutations associated with acquired resistance to imatinib. Despite eliciting similar clinical responses, the molecular effects of these agents on different subpopulations of leukemic cells remain incompletely understood. Furthermore, the consequences of using high-dose imatinib therapy have not been investigated in detail. Here we utilized clinical data from patients treated with dasatinib, nilotinib, or high-dose imatinib, together with a statistical data analysis and mathematical modeling approach, to investigate the molecular treatment response of leukemic cells to these agents. We found that these drugs elicit very similar responses if administered front-line. However, patients display significantly different kinetics when treated second-line, both in terms of differences between front-line and second-line treatment for the same drug, and among agents when used as second-line. We then utilized a mathematical framework describing the behavior of four differentiation levels of leukemic cells during therapy to predict the treatment response kinetics for the different cohorts of patients. The dynamics of BCR-ABL1 clearance observed in our study suggest that the use of standard or high-dose imatinib or a second-generation tyrosine kinase inhibitor such as nilotinib or dasatinib elicits similar responses when administered as front-line therapy for patients with chronic myeloid leukemia in chronic phase.

Loss of the novel tumour suppressor and polarity gene Trim62 (Dear1) synergizes with oncogenic Ras in invasive lung cancer.

Deregulation of cell polarity proteins has been linked to the processes of invasion and metastasis. TRIM62 is a regulator of cell polarity and a tumour suppressor in breast cancer. Here, we demonstrate that human non-small cell lung cancer lesions show a step-wise loss of TRIM62 levels during disease progression, which was associated with poor clinical outcomes. To directly examine the role of Trim62 in development of lung cancer, we deleted Trim62 in a mutant K-Ras mouse model of lung cancer. In this context, haploinsufficiency of Trim62 synergized with a K-RasG12D mutation to promote invasiveness and disrupt three-dimensional morphogenesis, both of which are associated with epithelial-mesenchymal transitions. Re-expression of Trim62 reverted these phenotypes in tumour cell lines. Thus, Trim62 loss cooperates with K-Ras mutation in tumourigenesis and metastasis in vivo, indicating that decreased levels of TRIM62 may play an important role in the evolution of lung cancer.

A prognostic model of therapy-related myelodysplastic syndrome for predicting survival and transformation to acute myeloid leukemia.

INTRODUCTION/BACKGROUND: We evaluated the characteristics of a cohort of patients with myelodysplastic syndrome (MDS) related to therapy (t-MDS) to create a prognostic model. PATIENTS AND METHODS: We identified 281 patients with MDS who had received previous chemotherapy and/or radiotherapy for previous malignancy. Potential prognostic factors were determined using univariate and multivariate analyses. RESULTS: Multivariate Cox regression analysis identified 7 factors that independently predicted short survival in t-MDS: age ≥ 65 years (hazard ratio [HR], 1.63), Eastern Cooperative Oncology Group performance status 2-4 (HR, 1.86), poor cytogenetics (-7 and/or complex; HR, 2.47), World Health Organization MDS subtype (RARs or RAEB-1/2; HR, 1.92), hemoglobin (< 11 g/dL; HR, 2.24), platelets (< 50 × 10(9)/dL; HR, 2.01), and transfusion dependency (HR, 1.59). These risk factors were used to create a prognostic model that segregated patients into 3 groups with distinct median overall survival: good (0-2 risk factors; 34 months), intermediate (3-4 risk factors; 12 months), and poor (5-7 risk factors; 5 months) (P < .001) and 1-year leukemia-free survival (96%, 84%, and 72%, respectively, P = .003). This model also identified distinct survival groups according to t-MDS therapy. CONCLUSION: In summary, we devised a prognostic model specifically for patients with t-MDS that predicted overall survival and leukemia-free survival. This model might facilitate the development of risk-adapted therapeutic strategies.