Multicenter phase II trial of enzastaurin in patients with relapsed or refractory advanced cutaneous T-cell lymphoma

An Update on Protein Kinases as Therapeutic Targets-Part I: Protein Kinase C Activation and Its Role in Cancer and Cardiovascular Diseases

Protein kinases are one of the most significant drug targets in the human proteome, historically harnessed for the treatment of cancer, cardiovascular disease, and a growing number of other conditions, including autoimmune and inflammatory processes. Since the approval of the first kinase inhibitors in the late 1990s and early 2000s, the field has grown exponentially, comprising 98 approved therapeutics to date, 37 of which were approved between 2016 and 2021. While many of these small-molecule protein kinase inhibitors that interact orthosterically with the protein kinase ATP binding pocket have been massively successful for oncological indications, their poor selectively for protein kinase isozymes have limited them due to toxicities in their application to other disease spaces. Thus, recent attention has turned to the use of alternative allosteric binding mechanisms and improved drug platforms such as modified peptides to design protein kinase modulators with enhanced selectivity and other pharmacological properties. Herein we review the role of different protein kinase C (PKC) isoforms in cancer and cardiovascular disease, with particular attention to PKC-family inhibitors. We discuss translational examples and carefully consider the advantages and limitations of each compound (Part I). We also discuss the recent advances in the field of protein kinase modulators, leverage molecular docking to model inhibitor-kinase interactions, and propose mechanisms of action that will aid in the design of next-generation protein kinase modulators (Part II).

Protein Kinase C at the Crossroad of Mutations, Cancer, Targeted Therapy and Immune Response

The frequent PKC dysregulations observed in many tumors have made these enzymes natural targets for anticancer applications. Nevertheless, this considerable interest in the development of PKC modulators has not led to the expected therapeutic benefits, likely due to the complex biological activities regulated by PKC isoenzymes, often playing ambiguous and protective functions, further driven by the occurrence of mutations. The structure, regulation and functions of PKCs have been extensively covered in other publications. Herein, we focused on PKC alterations mostly associated with complete functional loss. We also addressed the modest yet encouraging results obtained targeting PKC in selected malignancies and the more frequent negative clinical outcomes. The reported observations advocate the need for more selective molecules and a better understanding of the involved pathways. Furthermore, we underlined the most relevant immune mechanisms controlled by PKC isoforms potentially impacting the immune checkpoint inhibitor blockade-mediated immune recovery. We believe that a comprehensive examination of the molecular features of the tumor microenvironment might improve clinical outcomes by tailoring PKC modulation. This approach can be further supported by the identification of potential response biomarkers, which may indicate patients who may benefit from the manipulation of distinctive PKC isoforms.

Enzastaurin cardiotoxicity: QT interval prolongation, negative inotropic responses and negative chronotropic action

Several clinical trials observed that enzastaurin prolonged QT interval in cancer patients. However, the mechanism of enzastaurin-induced QT interval prolongation is unclear. Therefore, this study aimed to assess the effect and mechanism of enzastaurin on QT interval and cardiac function. The Langendorff and Ion-Optix MyoCam systems were used to assess the effects of enzastaurin on QT interval, cardiac systolic function and intracellular Ca²⁺ transient in guinea pig hearts and ventricular myocytes. The effects of enzastaurin on the rapid delayed rectifier (I_Kr), the slow delayed rectifier K⁺ current (I_Ks), transient outward potassium current (I_to), action potentials, Ryanodine Receptor 2 (RyR2) and the sarcoplasmic/endoplasmic reticulum Ca²⁺ ATPase 2a (SERCA2a) expression and activity in HEK 293 cell system and primary cardiomyocytes were investigated using whole-cell recording technique and western blotting. We found that enzastaurin significantly prolonged QT interval in guinea pig hearts and increased the action potential duration (APD) in guinea pig cardiomyocytes in a dose-dependent manner. Enzastaurin potently inhibited I_Kr by binding to the human Ether-à-go-go-Related gene (hERG) channel in both open and closed states, and hERG mutant channels, including S636A, S631A, and F656V attenuated the inhibitory effect of enzastaurin. Enzastaurin also moderately decreased I_Ks. Additionally, enzastaurin also induced negative chronotropic action. Moreover, enzastaurin impaired cardiac systolic function and reduced intracellular Ca²⁺ transient via inhibition of RyR2 phosphorylation. Taken together, we found that enzastaurin prolongs QT, reduces heart rate and impairs cardiac systolic function. Therefore, we recommend that electrocardiogram (ECG) and cardiac function should be continuously monitored when enzastaurin is administered to cancer patients.

Activators and Inhibitors of Protein Kinase C (PKC): Their Applications in Clinical Trials

Protein kinase C (PKC), a family of phospholipid-dependent serine/threonine kinase, is classed into three subfamilies based on their structural and activation characteristics: conventional or classic PKC isozymes (cPKCs; α, βI, βII, and γ), novel or non-classic PKC isozymes (nPKCs; δ, ε, η, and θ), and atypical PKC isozymes (aPKCs; ζ, ι, and λ). PKC inhibitors and activators are used to understand PKC-mediated intracellular signaling pathways and for the diagnosis and treatment of various PKC-associated diseases, such as cancers, neurological diseases, cardiovascular diseases, and infections. Many clinical trials of PKC inhibitors in cancers showed no significant clinical benefits, meaning that there is a limitation to design a cancer therapeutic strategy targeting PKC alone. This review will focus on the activators and inhibitors of PKC and their applications in clinical trials.

Cell signaling in cutaneous T-cell lymphoma microenvironment: promising targets for molecular-specific treatment

Cutaneous T-cell lymphomas (CTCL) result from the infiltration and proliferation of a population of T cells in the skin, inducing changes in the activity of both T cells and surrounding skin cells. In the CTCL microenvironment, cell interactions mediated by cell signaling pathways are altered. Defining changes in cell signaling enables to understand T-cell deregulations in the CTCL microenvironment and thus the progression of the disease. Moreover, characterizing signaling networks activated in CTCL stages can lead to consider new molecular biomarkers and therapeutic targets. Focusing on mycosis fungoides (MF), the most frequent variant of CTCL, and Sézary syndrome (SS), its leukemic variant, this review highlights recent molecular and genetic findings revealing modifications of key signaling pathways involved in (1) cell proliferation, cell growth, and cell survival such as MAP kinases and PI3K/Akt; (2) immune responses derived from TCR, TLR, JAK/STAT, and NF-kB; and (3) changes in tissue conditions such as extracellular matrix remodeling, hypoxia, and angiogenesis. Alterations in these signaling networks promote malignant T-cell proliferation and survival, T-cell migration, inflammation, and suppression of immune regulation of malignant T cells, making a skin microenvironment that allows disease progression. Targeting key proteins of these signaling pathways, using molecules already available and used in research, in clinical trials, and with other disease indications, can open the way to different therapeutic options in CTCL treatment.

Multi-Kinase Inhibitor with Anti-p38γ Activity in Cutaneous T-Cell Lymphoma

Current cutaneous T-cell lymphoma (CTCL) therapies are marked by an abbreviated response, subsequent drug resistance, and poor prognosis for patients with advanced disease. An understanding of molecular regulators involved in CTCL is needed to develop effective targeted therapies. One candidate regulator is p38γ, a mitogen-activated protein kinase crucial for malignant T-cell activity and growth. p38γ gene expression is selectively increased in CTCL patient samples and cell lines but not in healthy T cells. In addition, gene silencing of p38γ reduced CTCL cell viability, showing a key role in CTCL pathogenesis. Screening p38γ inhibitors is critical for understanding the mechanism of CTCL tumorigenesis and developing therapeutic applications. We prioritized a potent p38γ inhibitor (F7, also known as PIK75) through a high-throughput kinase inhibitor screen. At nanomolar concentrations, PIK75, a multiple kinase inhibitor, selectively killed CD4⁺ malignant CTCL cells but spared healthy CD4⁺ cells; induced significant reduction of tumor size in mouse xenografts; and effectively inhibited p38γ enzymatic activity and phosphorylation of its substrate, DLGH1, in CTCL cells and mouse xenografts. Here, we report that PIK75 has a potential clinical application to serve as a scaffold molecule for the development of a more selective p38γ inhibitor.

Cutaneous T-cell lymphomas: Focusing on novel agents in relapsed and refractory disease

Patients with relapsed or refractory cutaneous T-cell lymphoma (CTCL) display a dismal prognosis and their therapy represents an unmet medical need, as the best treatment strategy is yet to be determined. Exciting data on novel targeted agents are now emerging from recently concluded and ongoing clinical trials in patients with relapsed and refractory CTCL. Three FDA approved compounds are used as single agents including the oral retinoid bexarotene and histone deacetylase inhibitors romidepsin and vorinostat. Brentuximab vedotin, an anti-CD30 drug-conjugated monoclonal antibody, has received from European Commission the orphan designation but has not been approved by EMA yet. Several other molecules have demonstrated their activity in the same context and combination strategies are being explored. Participation in a well designed clinical trial is encouraged, as the introduction of novel agents will continue to expand the therapeutics options available in the management of CTCL.

Inhibition of Akt and other AGC kinases: A target for clinical cancer therapy?

AGC kinases have been identified to contribute to cancer development and progression. Currently, most AGC inhibitors in clinical development are Akt inhibitors such as MK-2206 or GDC-0068, which are known to promote cell growth arrest and to sensitize cancer cells to radiotherapy. Response rates in clinical trials with single agent Akt inhibitors are typically low. The observed adverse events are within the expected limits for compounds inhibiting the PI3K-mTOR axis. Preclinical and early clinical data for combination therapies are accumulating. Based on these data, several Akt inhibitors are about to enter phase 3 trials. Besides drugs that target Akt, p70S6K inhibitors have entered clinical development. Again, the response rates were rather low. In addition, relevant toxicities were identified, including a risk for coagulopathies with these compounds. Multi-AGC kinase inhibitors are also in early clinical development but the data is not sufficient yet to draw conclusions regarding their efficacy and side-effect profile. PKC inhibitors have been tested in the phase 3 setting but were found to lack efficacy. More trials with isoform-specific PKC inhibitors are expected. Taken together, therapies with AGC kinase inhibitors as single agents are unlikely to meet success. However, combination therapies and a precise stratification of patients according to the activation of signaling axes may increase the probability to see relevant efficacy with these compounds. The emergence of onco-immunotherapies holds some new challenges for these agents.

A pharmacokinetic and safety study of a fixed oral dose of enzastaurin HCl in native Chinese patients with refractory solid tumors and lymphoma

Purpose

This study was conducted to assess the pharmacokinetics and safety of enzastaurin in native Chinese patients with refractory solid tumors and lymphoma.

Methods

Eligible patients received 500 mg of enzastaurin orally once daily. The pharmacokinetics of enzastaurin and its metabolites were assessed on days 14 to 18. Patients were allowed to continue receiving the agent in a safety extension phase until disease progression or presentation with unacceptable toxicity.

Results

Twenty-five patients received at least 1 dose of enzastaurin, and twenty-one patients completed the pharmacokinetic phase. Fifteen patients entered the safety extension phase. Except for transient, asymptomatic grade 3 QT interval prolongation in one patient who had baseline grade 2 QT prolongation, other adverse events were of grade 1 to 2. The t_1/2, C_{av, ss,} and AUC_{τ, ss} for enzastaurin and its primary active metabolite LSN326020 were 14 and 42 h, 1,210 and 907 nmol/L, and 29,100 and 21,800 nmol•h/L, respectively. One patient with relapsed diffuse large B-cell lymphoma achieved a partial response that lasted for 8.1 months.

Conclusions

The pharmacokinetics of enzastaurin in Chinese cancer patients were consistent with those observed in previous studies abroad. Enzastaurin 500 mg daily was well tolerated by Chinese patients. We recommend 500 mg daily as the phase II dose in this population. Its efficacy in lymphoma deserves further investigation.

Trial Registration

ClinicalTrials.gov: NCT01432951

Enzastaurin: A lesson in drug development

Enzastaurin is an orally administered drug that was intended for the treatment of solid and haematological cancers. It was initially developed as an isozyme specific inhibitor of protein kinase Cβ (PKCβ), which is involved in both the AKT and MAPK signalling pathways that are active in many cancers. Enzastaurin had shown encouraging preclinical results for the prevention of angiogenesis, inhibition of proliferation and induction of apoptosis as well as showing limited cytotoxicity within phase I clinical trials. However, during its assessment in phase II and III clinical trials the efficacy of enzastaurin was poor both in combination with other drugs and as a single agent. In this review, we will discuss the development of enzastaurin from drug design to clinical testing, exploring target identification, validation and preclinical assessment. Finally, we will consider the clinical evaluation of enzastaurin as an example of the challenges associated with drug development. In particular, we discuss the poor translation of drug efficacy from preclinical animal models, inappropriate end point analysis, limited standards in phase I clinical trials, insufficient use of biomarker analysis and also patient stratification, all of which contributed to the failure to achieve approval of enzastaurin as an anticancer therapeutic.

Expression and activity of eIF6 trigger malignant pleural mesothelioma growth in vivo

eIF6 is an antiassociation factor that regulates the availability of active 80S. Its activation is driven by the RACK1/PKCβ axis, in a mTORc1 independent manner. We previously described that eIF6 haploinsufficiency causes a striking survival in the Eμ-Myc mouse lymphoma model, with lifespans extended up to 18 months. Here we screen for eIF6 expression in human cancers. We show that Malignant Pleural Mesothelioma tumors (MPM) and a MPM cell line (REN cells) contain high levels of hyperphosphorylated eIF6. Enzastaurin is a PKC beta inhibitor used in clinical trials. We prove that Enzastaurin treatment decreases eIF6 phosphorylation rate, but not eIF6 protein stability. The growth of REN, in vivo, and metastasis are reduced by either Enzastaurin treatment or eIF6 shRNA. Molecular analysis reveals that eIF6 manipulation affects the metabolic status of malignant mesothelioma cells. Less glycolysis and less ATP content are evident in REN cells depleted for eIF6 or treated with Enzastaurin (Anti-Warburg effect). We propose that eIF6 is necessary for malignant mesothelioma growth, in vivo, and can be targeted by kinase inhibitors.

A three-signal model of T-cell lymphoma pathogenesis

T-cell lymphoma pathogenesis and classification have, until recently, remained enigmatic. Recently performed whole-exome sequencing and gene-expression profiling studies have significant implications for their classification and treatment. Recurrent genetic modifications in antigen ("signal 1"), costimulatory ("signal 2"), or cytokine receptors ("signal 3"), and the tyrosine kinases and other signaling proteins they activate, have emerged as important therapeutic targets in these lymphomas. Many of these genetic modifications do not function in a cell-autonomous manner, but require the provision of ligand(s) by constituents of the tumor microenvironment, further supporting the long-appreciated view that these lymphomas are dependent upon and driven by their microenvironment. Therefore, the seemingly disparate fields of genomics and immunology are converging. A unifying "3 signal model" for T-cell lymphoma pathogenesis that integrates these findings will be presented, and its therapeutic implications briefly reviewed.

Follow-up of patients with mycosis fungoides after interferon α2b treatment failure

INTRODUCTION

Treatment of T cell cutaneous lymphoma( CTCL) is a controversial subject and the effectiveness of treatment is still low.

AIM

Report of single center experience of management CTCL after progression after first line treatment.

MATERIAL AND METHODS

We present 41 patients with CTCL, 29 received interferon α2b in first line, and 12 of them received second line therapy.

RESULTS

Overall response rate for second line therapy was 60%.

CONCLUSIONS

Results of the follow-up of patients with mycosis fungoides after interferon α2b treatment failure with the literature review and discussion.

Protein kinase C and cancer: what we know and what we do not

Since their discovery in the late 1970s, protein kinase C (PKC) isozymes represent one of the most extensively studied signaling kinases. PKCs signal through multiple pathways and control the expression of genes relevant for cell cycle progression, tumorigenesis and metastatic dissemination. Despite the vast amount of information concerning the mechanisms that control PKC activation and function in cellular models, the relevance of individual PKC isozymes in the progression of human cancer is still a matter of controversy. Although the expression of PKC isozymes is altered in multiple cancer types, the causal relationship between such changes and the initiation and progression of the disease remains poorly defined. Animal models developed in the last years helped to better understand the involvement of individual PKCs in various cancer types and in the context of specific oncogenic alterations. Unraveling the enormous complexity in the mechanisms by which PKC isozymes have an impact on tumorigenesis and metastasis is key for reassessing their potential as pharmacological targets for cancer treatment.

Identification of p38β as a therapeutic target for the treatment of Sézary syndrome

Cutaneous T-Cell Lymphomas (CTCL) represent a group of hematopoietic malignancies that home to the skin and have no known molecular basis for disease pathogenesis. Sézary syndrome (SS) is the leukemic variant of CTCL. Currently, CTCL is incurable, highlighting the need for new therapeutic modalities. We have previously observed that combined smallmolecule inhibition of protein kinase C (PKC) β and glycogen synthase kinase 3 (GSK3) causes synergistic apoptosis in CTCL cell lines and patient cells. Through microarray analysis of a SS cell line, we surveyed global gene expression following combined PKCβ-GSK3 treatment to elucidate therapeutic targets responsible for cell death. Clinically relevant targets were defined as genes differentially expressed in SS patients that were modulated by combination-drug treatment of SS cells. Gene set enrichment analysis uncovered candidate genes enriched for an immune cell signature, specifically the T-cell receptor and MAPK signaling pathways. Further analysis identified p38 as a potential therapeutic target that is over-expressed in SS patients and decreased by synergistic-inhibitor treatment. This target was verified through small-molecule inhibition of p38 leading to cell death in both SS cell lines and patient cells. These data establish p38 as a SS biomarker and potential therapeutic target for the treatment of CTCL.

Combinatorial inhibition of Plk1 and PKCβ in cancer cells with different p53 status

PKCβ and Plk1 are fascinating targets in cancer therapy. Therefore, we combined Enzastaurin targeting PKCβ and SBE13 targeting Plk1 to test synergistic effects in cells with different p53 status. We analyzed cell proliferation and apoptosis induction, and did Western blot and FACScan analyses to examine the combined PKCβ and Plk1 inhibition. p53-wild-type cells are more resistant to the combinatorial treatment than p53-deficient cells, which displayed a synergistic reduction of cell proliferation after the combination. HeLa, MCF-7 and HCT116(p53wt) and HCT116(p53-/-) cells differed in their cell cycle distribution after combinatorial treatment in dependence on a functional p53-dependent G1/S checkpoint (p53-deficient cells showed an enrichment in S and G2/M, p53-wild-type cells in G0/G1 phase). hTERT-RPE1 cells did not show the synergistic effects of cancer cells. Thus, we demonstrate for the first time that Plk1 inhibition using SBE13 enhances the effects of Enzastaurin in cancer cells. HCT116(p53wt) and HCT116(p53-/-) cells confirmed the p53-dependence of different effects after Plk1 and PKCβ inhibition observed in HeLa and MCF-7 cells. Obviously, p53 protects cells from the cytotoxicity of Enzastaurin in combination with SBE13. For that reason this combination can be useful to treat p53-deficient cancers, without displaying toxicity to normal cells, which all have functional p53.

Primary cutaneous T-cell lymphoma (mycosis fungoides and Sézary syndrome): part II. Prognosis, management, and future directions

Both mycosis fungoides (MF) and Sézary syndrome (SS) have a chronic, relapsing course, with patients frequently undergoing multiple, consecutive therapies. Treatment is aimed at the clearance of skin disease, the minimization of recurrence, the prevention of disease progression, and the preservation of quality of life. Other important considerations are symptom severity, including pruritus and patient age/comorbidities. In general, for limited patch and plaque disease, patients have excellent prognosis on ≥1 topical formulations, including topical corticosteroids and nitrogen mustard, with widespread patch/plaque disease often requiring phototherapy. In refractory early stage MF, transformed MF, and folliculotropic MF, a combination of skin-directed therapy plus low-dose immunomodulators (eg, interferon or bexarotene) may be effective. Patients with advanced and erythrodermic MF/SS can have profound immunosuppression, with treatments targeting tumor cells aimed for immune reconstitution. Biologic agents or targeted therapies either alone or in combination--including immunomodulators and histone-deacetylase inhibitors--are tried first, with more immunosuppressive therapies, such as alemtuzumab or chemotherapy, being generally reserved for refractory or rapidly progressive disease or extensive lymph node and metastatic involvement. Recently, an increased understanding of the pathogenesis of MF and SS with identification of important molecular markers has led to the development of new targeted therapies that are currently being explored in clinical trials in advanced MF and SS.

Management of relapses after hematopoietic cell transplantation in T-cell non-Hodgkin lymphomas

T-cell non-Hodgkin lymphomas (NHLs) are a heterogeneous group of malignancies that represent 10%-15% of all NHLs. The prognosis of relapsed T-cell NHL is poor, especially for those relapsing after an autologous (auto-) or allogeneic (allo-) hematopoietic cell transplantation (HCT). Disease relapse post auto-HCT is best managed on a clinical trial. In the absence of an investigational protocol, the choice of salvage therapies should take into account patient performance status, eligibility for an allo-HCT, and surface CD30 expression. CD30-directed therapies or aggressive salvage regimens can be used as a bridge to allo-HCT in medically fit patients. In the elderly or more infirm patients, single-agent therapies could be offered, aiming at palliation. Similarly, relapse after an allo-HCT is not uncommon and is a real challenge. Reduction in ongoing immune suppression or donor lymphocyte infusion are often considered in this setting to augment graft-versus-lymphoma (GVL) effects and can occasionally provide durable disease control. Clinical trials designed to investigate novel therapeutic agents with immunomodulatory properties to augment GVL effects (eg, histone deacetylase [HDAC] inhibitors, proteasome inhibitor, lenalidomide) or targeted therapies (eg, aurora A kinase inhibitors, anaplastic lymphoma kinase [ALK] inhibitors) are sorely needed to improve the dismal outcomes of T-cell NHL relapsing after an allo-HCT.

Modulation of pancreatic tumor potential by overexpression of protein kinase C β1

OBJECTIVE

This study aimed to investigate whether the overexpression of protein kinase C β1 (PKCβ1) is able to modulate the malignant phenotype displayed by the human ductal pancreatic carcinoma cell line PANC1.

METHODS

PKCβ1 overexpression was achieved using a stable transfection approach. PANC1-PKCβ1 and control cells were analyzed both in vitro and in vivo.

RESULTS

PANC1-PKCβ1 cells displayed a lower growth capacity associated with the down-regulation of the MEK/ERK pathway and cyclin expression. Furthermore, PKCβ1 overexpression was associated with an enhancement of cell adhesion to fibronectin and with reduced migratory and invasive phenotypes. In agreement with these results, PANC1-PKCβ1 cells showed an impaired ability to secrete proteolytic enzymes. We also found that PKCβ1 overexpressing cells were more resistant to cell death induced by serum deprivation, an event associated with G0/G1 arrest and the modulation of PI3K/Akt and NF-κB pathways. Most notably, the overexpression of PKCβ1 completely abolished the ability of PANC1 cells to induce tumors in nude mice.

CONCLUSIONS

Our results established an important role for PKCβ1 in PANC1 cells suggesting it would act as a suppressor of tumorigenic behavior in pancreatic cancer.

Randomized, Phase II, Placebo-Controlled, Double-Blind Study With and Without Enzastaurin in Combination With Paclitaxel and Carboplatin As First-Line Treatment Followed by Maintenance Treatment in Advanced Ovarian Cancer

Purpose

Enzastaurin is an oral serine/threonine kinase inhibitor antitumor agent. Our phase II trial tested the efficacy and safety of enzastaurin added to a standard carboplatin/paclitaxel chemotherapy regimen in patients with newly diagnosed advanced ovarian cancer.

Patients and Methods

This was a randomized, placebo-controlled study in patients with International Federation of Gynecology and Obstetrics stage IIB to IV ovarian, fallopian tube, or peritoneal epithelial carcinoma. Patients were randomly assigned to six cycles of chemotherapy (paclitaxel/carboplatin ± enzastaurin [PCE/PC]) followed by maintenance therapy (enzastaurin/placebo). Primary end point was progression-free survival (PFS). Secondary measures included response rate, safety assessment, and translational research.

Results

A total of 142 patients were randomly assigned to PCE (n = 69) or PC (n = 73). Patients in the PCE group had a 3.7-month longer median PFS compared with patients in the PC group; this was not statistically significant (hazard ratio [HR], 0.80; 95% CI, 0.50 to 1.29; P = .37). Safety profiles of the treatment arms were comparable. Frequency of discontinuation because of adverse events was similar (PCE, 11.9%; PC, 9.7%). Multivariate analyses confirmed the importance of optimal debulking with regard to PFS (debulking optimal v suboptimal: HR, 0.51; 95% CI, 0.30 to 0.85; P = .009). HR for covariate stage (stage IIB to IIIB v IIIC to IV) was not statistically significant (0.75; 95% CI, 0.38 to 1.47; P = .40). Translational research of immunohistochemistry protein assays did not identify any markers significantly associated with treatment difference regarding PFS.

Conclusion

The PCE combination increased PFS, but it was not significantly superior to PC in this phase II study.

Novel therapeutic agents for cutaneous T-Cell lymphoma

Mycosis fungoides (MF) and Sezary Syndrome (SS) represent the most common subtypes of primary Cutaneous T-cell lymphoma (CTCL). Patients with advanced MF and SS have a poor prognosis leading to an interest in the development of new therapies with targeted mechanisms of action and acceptable safety profiles. In this review we focus on such novel strategies that have changed the treatment paradigm of this rare malignancy.

Inhibition of glycogen synthase kinase-3 increases the cytotoxicity of enzastaurin

Cutaneous T cell lymphomas (CTCL) represent a spectrum of several distinct non-Hodgkin's lymphomas that are characterized by an invasion of the skin by malignant, clonal lymphocytes. Our lab has previously demonstrated that the Protein Kinase C (PKC) β inhibitor Enzastaurin increases apoptosis in malignant lymphocytes of CTCL. These results directly led to a clinical trial for Enzastaurin in CTCL where it was well tolerated and showed modest activity. To ascertain a means of improving the efficacy of Enzastaurin, we investigated complimentary signaling pathways and identified Glycogen Synthase Kinase 3 (GSK3) as important in survival signaling in CTCL. Enzastaurin combined with GSK3 inhibitors demonstrated anenhancement of cytotoxicity. Treatment with a combination of Enzastaurin and the GSK3 inhibitor AR-A014418 resulted in up-regulation of β catenin total protein and β catenin-mediated transcription. Inhibition of β catenin-mediated transcription or shRNA knockdown of β catenin decreased the cytotoxic effects of Enzastaurin plus AR-A014418. In addition, treatment with Enzastaurin and AR-A014418 decreased the mRNA levels and surface expression of CD44. shRNA knockdown of β catenin also restored CD44 surface expression. Our observations provide a rationale for the combined targeting of PKC and GSK3 signaling pathways in CTCL to enhance the therapeutic outcome.