Phase I and pharmacological study of daily oral administration of perifosine (D-21266) in patients with advanced solid tumours

AT7867 Inhibits the Growth of Colorectal Cancer Stem-Like Cells and Stemness by Regulating the Stem Cell Maintenance Factor Ascl2 and Akt Signaling

Cancer stem cells (CSCs) are the core factors leading to recurrence, insensitivity to radiotherapy and chemotherapy, and immunotherapy resistance in patients with colorectal cancer. AT7867, a potent oral AKT inhibitor, was found to have antitumor activity in colorectal cancer; however, the effect on colorectal cancer stem cells is still unclear. This study was conducted to clarify the molecular mechanism underlying the CSC growth inhibitory effects of AT7867. We cultured colorectal cancer cells (CRCs) in a serum-free medium and enriched colorectal cancer stem cells. Subsequently, the effects of AT7867 on CSCs were analyzed by CCK-8, colony formation, flow cytometry, and immunofluorescence assays. The results indicated that AT7867 induces G2/M phase arrest and cell apoptosis in cancer stem cells. Subsequently, we identified Ascl2 as the main gene affecting the stemness of colorectal cancer in AT7867 by RNA sequencing. The current study showed that Ascl2 is involved in the metastasis, invasion, and proliferation of CRCs. The next experiments demonstrated that overexpression of Ascl2 did affect the therapeutic effect of AT7867 on CRC stemness. Furthermore, compared with other Akt inhibitors, AT7867 could promote the differentiation of colorectal cancer stem cells. Thus, AT7867 might be a potential antitumor drug candidate to treat CRC by targeting CSCs.

Comparative EPR spectroscopy analysis of amphotericin B and miltefosine interactions with Leishmania, erythrocyte and macrophage membranes

Electron paramagnetic resonance (EPR) spectroscopy of spin labels was used to study the interactions of amphotericin B (AmB) with the plasma membrane of Leishmania (L.) amazonensis promastigotes, human erythrocytes and J774.A1 murine macrophages, in comparison with reported and novel data for miltefosine (MIL). One of the objectives of this work is to look for the relationships between the activities of these two drugs in the Leishmania parasite with their changes in the cell membrane. A spin-labeled stearic acid inserted into the cell membranes showed strong interactions with putative AmB/sterol complexes, characterized by reductions in molecular dynamics. The concentration of the drugs in the plasma membrane that reduced the cell population by 50%, and the membrane-water partition coefficient of the drugs, were assessed. These biophysical parameters enabled estimates of possible therapeutic concentrations of these two drugs in the interstitial fluids of the tissues to be made. AmB displayed higher affinity for the plasma membrane of L. amazonensis than for that of the macrophage and erythrocyte, denoting a preference for a membrane that contains ergosterol. AmB also demonstrated higher hemolytic potential than MIL for measurements on erythrocytes in both PBS and whole blood. For MIL, the EPR technique detected membrane changes induced by the drug in the same concentration range that inhibited the growth of parasites, but in the case of AmB, an 8-fold higher concentration of the IC₅₀ was necessary to observe a reduction in membrane fluidity, suggesting a better localized effect of AmB on the membrane. Taken together, the results demonstrate that the antiproliferative and cytotoxic effects of both drugs are associated with changes in cell membranes.

Lactic Acidosis Interferes With Toxicity of Perifosine to Colorectal Cancer Spheroids: Multimodal Imaging Analysis

Colorectal cancer (CRC) is a disease with constantly increasing incidence and high mortality. The treatment efficacy could be curtailed by drug resistance resulting from poor drug penetration into tumor tissue and the tumor-specific microenvironment, such as hypoxia and acidosis. Furthermore, CRC tumors can be exposed to different pH depending on the position in the intestinal tract. CRC tumors often share upregulation of the Akt signaling pathway. In this study, we investigated the role of external pH in control of cytotoxicity of perifosine, the Akt signaling pathway inhibitor, to CRC cells using 2D and 3D tumor models. In 3D settings, we employed an innovative strategy for simultaneous detection of spatial drug distribution and biological markers of proliferation/apoptosis using a combination of mass spectrometry imaging and immunohistochemistry. In 3D conditions, low and heterogeneous penetration of perifosine into the inner parts of the spheroids was observed. The depth of penetration depended on the treatment duration but not on the external pH. However, pH alteration in the tumor microenvironment affected the distribution of proliferation- and apoptosis-specific markers in the perifosine-treated spheroid. Accurate co-registration of perifosine distribution and biological response in the same spheroid section revealed dynamic changes in apoptotic and proliferative markers occurring not only in the perifosine-exposed cells, but also in the perifosine-free regions. Cytotoxicity of perifosine to both 2D and 3D cultures decreased in an acidic environment below pH 6.7. External pH affects cytotoxicity of the other Akt inhibitor, MK-2206, in a similar way. Our innovative approach for accurate determination of drug efficiency in 3D tumor tissue revealed that cytotoxicity of Akt inhibitors to CRC cells is strongly dependent on pH of the tumor microenvironment. Therefore, the effect of pH should be considered during the design and pre-clinical/clinical testing of the Akt-targeted cancer therapy.

Phase I clinical trial of temsirolimus and perifosine for recurrent glioblastoma

Purpose

Malignant glioma (MG) is the most deadly primary brain cancer. Signaling though the PI3K/AKT/mTOR axis is activated in most MGs and therefore a potential therapeutic target. The mTOR inhibitor temsirolimus and the AKT inhibitor perifosine are each well‐tolerated as single agents but with limited activity reclinical data demonstrate synergistic anti‐tumor effects from combined treatment. Therefore, we initiated a phase I trial of combined therapy in recurrent MGs to determine safety and a recommended phase II dose.

Methods

Adults with recurrent MG, Karnofsky Performance Status ≥ 60 were enrolled, with no limit on the number of prior therapies. Temsirolimus dose was escalated using standard 3 + 3 design from 15 mg to 170 mg administered once weekly. Perifosine was fixed as a 600 mg load on day 1 followed by 100 mg nightly (single agent MTD) until dose level 7 when the load increased to 900 mg.

Results

We treated 35 patients with with glioblastoma (17) or other MGs (18; including nine anaplastic astrocytoma, nine anaplastic oligodendroglioma, one anaplastic oligoastrocytoma, and two low grade astrocytomas with radiographic transformation to MG). We observed five dose‐limiting toxicities (DLTs): one at dose level 3 (50mg temsirolimus), then two at dose level 7 expansion (170 mg temsirolimus), and then two more at dose level 6 expansion (170 mg temsirolimus). DLTs included thrombocytopenia (n = 3), intracerebral hemorrhage (n = 1) and lung infection (n = 1).

Conclusion

Combining the mTOR inhibitor temsirolimus dosed at 115 mg weekly and the AKT inhibitor perifosine dosed at 100 mg daily (following 600 mg load) is tolerable in heavily pretreated adults with recurrent MGs.

Lipids and Membrane Microdomains: The Glycerolipid and Alkylphosphocholine Class of Cancer Chemotherapeutic Drugs

Synthetic antitumor lipids are metabolically stable lysophosphatidylcholine derivatives, encompassing a class of non-mutagenic drugs that selectively target cancerous cells. In this chapter we review the literature as relates to the clinical efficacy of these antitumor lipid drugs and how our understanding of their mode of action has evolved alongside key advances in our knowledge of membrane structure, organization, and function. First, the history of the development of this class of drugs is described, providing a summary of clinical outcomes of key members including edelfosine, miltefosine, perifosine, erufosine, and erucylphosphocholine. A detailed description of the biophysical properties of these drugs and specific drug-lipid interactions which may contribute to the selectivity of the antitumor lipids for cancer cells follows. An updated model on the mode of action of these lipid drugs as membrane disorganizing agents is presented. Membrane domain organization as opposed to targeting specific proteins on membranes is discussed. By altering membranes, these antitumor lipids inhibit many survival pathways while activating pro-apoptotic signals leading to cell demise.

Alkylphospholipids are Signal Transduction Modulators with Potential for Anticancer Therapy

BACKGROUND

Alkylphospholipids (APLs) are synthetically derived from cell membrane components, which they target and thus modify cellular signalling and cause diverse effects. This study reviews the mechanism of action of anticancer, antiprotozoal, antibacterial and antiviral activities of ALPs, as well as their clinical use.

METHODS

A literature search was used as the basis of this review.

RESULTS

ALPs target lipid rafts and alter phospholipase D and C signalling cascades, which in turn will modulate the PI3K/Akt/mTOR and RAS/RAF/MEK/ERK pathways. By feedback coupling, the SAPK/JNK signalling chain is also affected. These changes lead to a G2/M phase cell cycle arrest and subsequently induce programmed cell death. The available knowledge on inhibition of AKT phosphorylation, mTOR phosphorylation and Raf down-regulation renders ALPs as attractive candidates for modern medical treatment, which is based on individualized diagnosis and therapy. Corresponding to their unusual profile of activities, their side effects result from cholinomimetic activity mainly and focus on the gastrointestinal tract. These aspects together with their bone marrow sparing features render APCs well suited for modern combination therapy. Although the clinical success has been limited in cancer diseases so far, the use of miltefosine against leishmaniosis is leading the way to better understanding their optimized use.

CONCLUSION

Recent synthetic programs generate congeners with the increased therapeutic ratio, liposomal formulations, as well as diapeutic (or theranostic) derivatives with optimized properties. It is anticipated that these innovative modifications will pave the way for the further successful development of ALPs.

Phase II trial of an AKT inhibitor (perifosine) for recurrent glioblastoma

PURPOSE

Perifosine (PRF) is an oral alkylphospholipid with antineoplastic effects and reasonable tolerability. It inhibits signaling through the PI3/AKT axis and other cascades of biologic importance in glioblastoma, and has promising pre-clinical activity in vitro and in vivo. Therefore, we conducted a phase II open-label single-arm clinical trial of perifosine for patients with recurrent glioblastoma (GBM).

METHODS

We planned to accrue up to 30 adults with recurrent GBM with a minimum Karnofsky Performance Status of 50 following radiotherapy but without other restrictions on the number or types of prior therapy. Concurrent p450 stimulating hepatic enzyme inducing anticonvulsants were prohibited. Patients were treated with a loading dose of 600 mg PRF (in 4 divided doses on day 1) followed by 100 mg daily until either disease progression or intolerable toxicity. The primary endpoint was the 6-month progression free survival (PFS6) rate, with at least 20% considered promising. Accrual was continuous but if 0 of the first 12 patients with GBM reached PFS6, then further accrual would terminate for futility. Patients with other high grade gliomas were accrued concurrently to an exploratory cohort.

RESULTS

Treatment was generally well tolerated; gastrointestinal toxicities were the most common side effects, although none resulted in treatment discontinuation. However, there was limited to no efficacy in GBM (n = 16): the PFS6 rate was 0%, median PFS was 1.58 months [95% CI (1.08, 1.84)], median overall survival was 3.68 months [95% CI (2.50, 7.79)], with no radiographic responses. There was a confirmed partial response in one patient with anaplastic astrocytoma (n = 14).

CONCLUSIONS

PRF is tolerable but ineffective as monotherapy for GBM. Preclinical data suggests synergistic effects of PRF in combination with other approaches, and further study is ongoing.

Role of the PI3K/AKT/mTOR signaling pathway in ovarian cancer: Biological and therapeutic significance

Ovarian cancer (OC) is a lethal gynecological cancer. The phosphatidylinositol 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) signaling pathway plays an important role in the regulation of cell survival, growth, and proliferation. Irregularities in the major components of the PI3K/AKT/mTOR signaling pathway are common in human cancers. Despite the availability of strong pre-clinical and clinical data of PI3K/AKT/mTOR pathway inhibitors in OC, there is no FDA approved inhibitor available for the treatment of OC. Here, we outline the importance of PI3K/AKT/mTOR signaling pathway in OC tumorigenesis, proliferation and progression, and pre-clinical and clinical experience with several PI3K/AKT/mTOR pathway inhibitors in OC.

Perturbing the Dynamics and Organization of Cell Membrane Components: A New Paradigm for Cancer-Targeted Therapies

Cancer is a multi-process disease where different mechanisms exist in parallel to ensure cell survival and constant adaptation to the extracellular environment. To adapt rapidly, cancer cells re-arrange their plasma membranes to sustain proliferation, avoid apoptosis and resist anticancer drugs. In this review, we discuss novel approaches based on the modifications and manipulations that new classes of molecules can exert in the plasma membrane lateral organization and order of cancer cells, affecting growth factor signaling, invasiveness, and drug resistance. Furthermore, we present azurin, an anticancer protein from bacterial origin, as a new approach in the development of therapeutic strategies that target the cell membrane to improve the existing standard therapies.

A phase I study of single-agent perifosine for recurrent or refractory pediatric CNS and solid tumors

The PI3K/Akt/mTOR signaling pathway is aberrantly activated in various pediatric tumors. We conducted a phase I study of the Akt inhibitor perifosine in patients with recurrent/refractory pediatric CNS and solid tumors. This was a standard 3+3 open-label dose-escalation study to assess pharmacokinetics, describe toxicities, and identify the MTD for single-agent perifosine. Five dose levels were investigated, ranging from 25 to 125 mg/m2/day for 28 days per cycle. Twenty-three patients (median age 10 years, range 4-18 years) with CNS tumors (DIPG [n = 3], high-grade glioma [n = 5], medulloblastoma [n = 2], ependymoma [n = 3]), neuroblastoma (n = 8), Wilms tumor (n = 1), and Ewing sarcoma (n = 1) were treated. Only one DLT occurred (grade 4 hyperuricemia at dose level 4). The most common grade 3 or 4 toxicity at least possibly related to perifosine was neutropenia (8.7%), with the remaining grade 3 or 4 toxicities (fatigue, hyperglycemia, fever, hyperuricemia, and catheter-related infection) occurring in one patient each. Pharmacokinetics was dose-saturable at doses above 50 mg/m2/day with significant inter-patient variability, consistent with findings reported in adult studies. One patient with DIPG (dose level 5) and 4 of 5 patients with high-grade glioma (dose levels 2 and 3) experienced stable disease for two months. Five subjects with neuroblastoma (dose levels 1 through 4) achieved stable disease which was prolonged (≥11 months) in three. No objective responses were noted. In conclusion, the use of perifosine was safe and feasible in patients with recurrent/refractory pediatric CNS and solid tumors. An MTD was not defined by the 5 dose levels investigated. Our RP2D is 50 mg/m2/day.

Maximising the potential of AKT inhibitors as anti-cancer treatments

PI3K/AKT signalling is commonly disrupted in human cancers, with AKT being a central component of the pathway, influencing multiple processes that are directly involved in tumourigenesis. Targeting AKT is therefore a highly attractive anti-cancer strategy with multiple AKT inhibitors now in various stages of clinical development. In this review, we summarise the role and regulation of AKT signalling in normal cellular physiology. We highlight the mechanisms by which AKT signalling can be hyperactivated in cancers and discuss the past, present and future clinical strategies for AKT inhibition in oncology.

Alkylphospholipids: An update on molecular mechanisms and clinical relevance

Alkylphospholipids (APLs) represent a new class of drugs which do not interact directly with DNA but act on the cell membrane where they accumulate and interfere with lipid metabolism and signalling pathways. This review summarizes the mode of action at the molecular level of these compounds. In this sense, a diversity of mechanisms has been suggested to explain the actions of clinically-relevant APLs, in particular, in cancer treatment. One consistently reported finding is that APLs reduce the biosynthesis of phosphatidylcholine (PC) by inhibiting the rate-limiting enzyme CTP:phosphocholine cytidylyltransferase (CT). APLs also alter intracellular cholesterol traffic and metabolism in human tumour-cell lines, leading to an accumulation of cholesterol inside the cell. An increase in cholesterol biosynthesis associated with a decrease in the synthesis of choline-containing phospholipids and cholesterol esterification leads to a change in the free-cholesterol:PC ratio in cells exposed to APLs. Akt phosphorylation status after APL exposure shows that this critical regulator for cell survival is modulated by changes in cholesterol levels induced in the plasma membrane by these lipid analogues. Furthermore, APLs produce cell ultrastructural alterations with an abundant autophagic vesicles and autolysosomes in treated cells, indicating an interference of autophagy process after APL exposure. Thus, antitumoural APLs interfere with the proliferation of tumour cells via a complex mechanism involving phospholipid and cholesterol metabolism, interfere with lipid-dependent survival-signalling pathways and autophagy. Although APLs also exert antiparasitic, antibacterial, and antifungal effects, in this review we provide a summary of the antileishmanial activity of these lipid analogues. This article is part of a Special Issue entitled: Membrane Lipid Therapy: Drugs Targeting Biomembranes edited by Pablo V. Escribá.

AKT in cancer: new molecular insights and advances in drug development

The phosphatidylinositol-3 kinase (PI3K)-AKT pathway is one of the most commonly dysregulated pathways in all of cancer, with somatic mutations, copy number alterations, aberrant epigenetic regulation and increased expression in a number of cancers. The carefully maintained homeostatic balance of cell division and growth on one hand, and programmed cell death on the other, is universally disturbed in tumorigenesis, and downstream effectors of the PI3K-AKT pathway play an important role in this disturbance. With a wide array of downstream effectors involved in cell survival and proliferation, the well-characterized direct interactions of AKT make it a highly attractive yet elusive target for cancer therapy. Here, we review the salient features of this pathway, evidence of its role in promoting tumorigenesis and recent progress in the development of therapeutic agents that target AKT.

New development of inhibitors targeting the PI3K/AKT/mTOR pathway in personalized treatment of non-small-cell lung cancer

Lung cancer is the leading cause of cancer-related death worldwide. Non-small-cell lung cancer (NSCLC) is the most common pathological type of lung cancer, divided into squamous cell carcinoma and adenocarcinoma. Despite better techniques of surgery and improvement in adjuvant and neoadjuvant therapy, the median survival of advanced NSCLC is only 8-10 months. With increased understanding of molecular alternations in NSCLC, considerable efforts have focused on the development of personalized molecular-targeted therapies. The PI3K/AKT/mTOR pathway regulates tumor development, growth, and proliferation of NSCLC. Various novel inhibitors targeting this pathway have been identified in preclinical studies or clinical trials. Some genetic alternations may be considered sensitive or resistant biomarkers to these inhibitors. Sometimes, upregulation of RTK and the downstream PI3K pathway or upregulation of the ERK pathway by compensatory feedback reactivation in response to these inhibitors also lead to drug resistance. Therefore, combination therapy of these inhibitors and other targeted inhibitors such as EGFR-TKI or MEK inhibitors according to genetic status and categories of inhibitors is required to enhance the efficacy of these inhibitors. Here, we reviewed the genetic status of the PI3K/AKT/mTOR pathway in NSCLC and the novel inhibitors targeting this pathway in preclinical or clinical studies, exploring the possible genetic alternations related to different inhibitors and the means to enhance the antitumor effect in NSCLC.

Preclinical evaluation of perifosine as a potential promising anti-rhabdomyosarcoma agent

Rhabdomyosarcoma (RMS) is a highly malignant and metastatic pediatric cancer that arises from the skeletal muscle. Recent studies have identified an important role of AKT signaling in RMS progression. In the current study, we investigated the activity of perifosine, an oral alkylphospholipid AKT inhibitor, against human RMS cells (RD and Rh-30 lines) both in vivo and in vitro, and studied the underlying mechanisms. We showed that perifosine significantly inhibited RMS cell growth in concentration- and time-dependent manners. Meanwhile, perifosine induced dramatic apoptosis in RMS cells. At the signaling level, perifosine blocked AKT activation, while inducing reactive oxygen species (ROS) production as well as JNK and P38 phosphorylations in RMS cells. Restoring AKT activation by introducing a constitutively active-AKT (CA-AKT) only alleviated (not abolished) perifosine-induced cytotoxicity in RD cells. Yet, the ROS scavenger N-acetyl cysteine (NAC) as well as pharmacological inhibitors against JNK (SP-600125) or P38 (SB-203580) suppressed perifosine-induced cytotoxicity in RMS cells. Thus, perifosine induces growth inhibition and apoptosis in RMS cells through mechanisms more than just blocking AKT. In vivo, oral administration of perifosine significantly inhibited growth of Rh-30 xenografts in severe combined immunodeficient (SCID) mice. Our data indicate that perifosine might be further investigated as a promising anti-RMS agent.

Efficacy of perifosine alone and in combination with sorafenib in an HrasG12V plus shp53 transgenic mouse model of hepatocellular carcinoma

PURPOSE

Perifosine has shown antitumor activity via inhibition of Akt phosphorylation in many advanced solid tumors. This study investigated the efficacy of perifosine alone and in combination with sorafenib in a transgenic mouse model of HCC.

METHODS

The mouse model of HCC was generated by hydrodynamic injection of transposons encoding HrasG12V and short-hairpin RNA downregulating p53. The transgenic mice were treated with perifosine alone and in combination with sorafenib to evaluate efficacy of drugs on tumor growth and survival.

RESULTS

Treatment with perifosine for 5 weeks, alone and in combination with sorafenib, strongly inhibited tumor growth and increased survival. Perifosine inhibited HCC cell proliferation, induced apoptosis, and decreased tumor angiogenesis. Furthermore, its combination with sorafenib enhanced these effects. In addition, Akt phosphorylation was decreased by perifosine and further decreased by combination treatment. Although perifosine alone did not appear to activate the caspase pathway, combination treatment increased the cleavage of caspase-3, caspase-9, and poly (ADP-ribose) polymerase.

CONCLUSIONS

The preclinical effect that current study showed represents a strong rationale for clinical trials using perifosine alone and in combination with sorafenib in the treatment of HCC patients.

Plasma and cerebrospinal fluid pharmacokinetics of the Akt inhibitor, perifosine, in a non-human primate model

PURPOSE

Central nervous system tumors are histologically and biologically heterogeneous. Standard treatment for malignant tumors includes surgery, radiation and chemotherapy, yet surgical resection is not always an option and chemotherapeutic agents have limited benefit. Recent investigations have focused on molecularly targeted therapies aimed at critical tumorigenic pathways. Several tumor types, including high-grade gliomas and pediatric pontine gliomas, exhibit Akt activation. Perifosine, an orally bioavailable, synthetic alkylphospholipid and potent Akt inhibitor, has demonstrated activity in some preclinical models, but absent activity in a genetically engineered mouse model of pontine glioma. We evaluated the plasma and cerebrospinal fluid pharmacokinetics of orally administered perifosine in a non-human primate model to evaluate CNS penetration.

METHODS

Perifosine was administered orally to three adult rhesus monkeys as a single dose of 7.0 mg/kg perifosine. Serial paired plasma and CSF samples were collected for up to 64 days. Perifosine was quantified with a validated HPLC/tandem mass spectrometry assay. Pharmacokinetic parameters were estimated using non-compartmental methods. CSF penetration was calculated from the areas under the concentration-time curves.

RESULTS

Peak plasma concentrations (C max) ranged from 11.7-19.3 µM, and remained >1 µM for >28 days. Time to C max (T max) was 19 h. The median (range) AUCPl was 3148 (2502-4705) µM/h, with a median (range) terminal half-life (t 1/2) of 193 (170-221) h. Plasma clearance was 494 (329-637) mL/h/kg. Peak CSF concentrations were 4.1-10.1 nM (T max 64-235 h). CSF AUCs and t 1/2 were 6358 (2266-7568) nM/h and 277 (146-350) h, respectively. Perifosine concentrations in the CSF remained over  nM for >35 days. The mean CSF penetration was 0.16 %.

CONCLUSION

CNS penetration of perifosine after systemic administration is poor. However, levels were measurable in both plasma and CSF for an extended time (>2 months) after a single oral dose.

Emerging therapeutic targets in bladder cancer

Treatment of muscle invasive urothelial bladder carcinoma (BCa) remains a major challenge. Comprehensive genomic profiling of tumors and identification of driver mutations may reveal new therapeutic targets. This manuscript discusses relevant molecular drivers of the malignant phenotype and agents with therapeutic potential in BCa. Small molecule pan-FGFR inhibitors have shown encouraging efficacy and safety results especially among patients with activating FGFR mutations or translocations. mTOR inhibitors for patients with TSC1 mutations and concomitant targeting of PI3K and MEK represent strategies to block PI3K/AKT/mTOR pathway. Encouraging preclinical results with ado-trastuzumab emtansine (T-DM1) exemplifies a new potential treatment for HER2-positive BCa along with innovative bispecific antibodies. Inhibitors of cell cycle regulators (aurora kinase, polo-like kinase 1, and cyclin-dependent kinase 4) are being investigated in combination with chemotherapy. Early results of clinical studies with anti-CTLA4 and anti-PDL1 are propelling immune modulating drugs to the forefront of emerging treatments for BCa. Collectively, these novel therapeutic targets and treatment strategies hold promise to improve the outcome of patients afflicted with this malignancy.

Anti-tumor activities of lipids and lipid analogues and their development as potential anticancer drugs

Lipids have the potential for development as anticancer agents. Endogenous membrane lipids, such as ceramides and certain saturated fatty acids, have been found to modulate the viability of tumor cells. In addition, many tumors over-express cyclooxygenase, lipoxygenase or cytochrome P450 enzymes that mediate the biotransformation of ω-6 polyunsaturated fatty acids (PUFAs) to potent eicosanoid regulators of tumor cell proliferation and cell death. In contrast, several analogous products from the biotransformation of ω-3 PUFAs impair particular tumorigenic pathways. For example, the ω-3 17,18-epoxide of eicosapentaenoic acid activates anti-proliferative and proapoptotic signaling cascades in tumor cells and the lipoxygenase-derived resolvins are effective inhibitors of inflammatory pathways that may drive tumor expansion. However, the development of potential anti-cancer drugs based on these molecules is complex, with in vivo stability a major issue. Nevertheless, recent successes with the antitumor alkyl phospholipids, which are synthetic analogues of naturally-occurring membrane phospholipid esters, have provided the impetus for development of further molecules. The alkyl phospholipids have been tested against a range of cancers and show considerable activity against skin cancers and certain leukemias. Very recently, it has been shown that combination strategies, in which alkyl phospholipids are used in conjunction with established anticancer agents, are promising new therapeutic approaches. In future, the evaluation of new lipid-based molecules in single-agent and combination treatments may also be assessed. This could provide a range of important treatment options in the management of advanced and metastatic cancer.

A phase I and pharmacokinetic study of oral perifosine with different loading schedules in patients with refractory neoplasms

PURPOSE

To determine the maximum tolerated dose (MTD) of perifosine (NSC 639966), an alkylphospholipid modulator of signal transduction, using different oral loading and maintenance regimens in an effort to avoid gastrointestinal toxicity while seeking maximal sustained plasma concentrations.

METHODS

Thirty-one patients with advanced neoplasms were treated with monthly cycles of perifosine loading doses of 300, 600, 900, 1,200 and 1,500 mg (dose levels 1 through 5, respectively) on days 1-2 depending on the actual dose of the initial cycle. For subsequent cycles, perifosine loading doses were reduced to 100, 200, 300, 400 and 1,000 mg at the respective corresponding dose levels. Daily perifosine "maintenance" doses of 50, 100, 150, 200 and 250 mg for levels 1 through 5, respectively, commenced on days 2 or 3 and continued for a total of 21 days. No treatment was given for days 22-27. The pharmacokinetics of perifosine with these schedules was characterized.

RESULTS

Dose-limiting diarrhea developed at or above dose level 4. The MTD and recommended phase II dose was dose level 3B, with a loading dose of 900 mg on day 1 divided into two doses of 450 mg administered 6 h apart and a maintenance dose of 150 mg on day 2 through 21. On subsequent cycles, the loading dose was reduced to 300 mg. Non-gastrointestinal toxicities included three episodes of gout or gout-like syndromes observed at doses above the MTD. The median peak plasma concentration of perifosine achieved at the MTD was approximately 8.3 µg/mL. Four patients had stable disease ranging from 167 to 735 days.

CONCLUSIONS

Perifosine given according to a loading and maintenance schedule can safely sustain concentrations of drug, approaching concentrations achieved in preclinical models with evidence of anti-tumor effect.

Affinity of alkylphosphocholines to biological membrane of prostate cancer: studies in natural and model systems

The effectiveness of two alkylphosphocholines (APCs), hexadecylphosphocholine (miltefosine) and erucylphosphocholine to combat prostate cancer has been studied in vitro with artificial cancerous membrane, modelled with the Langmuir monolayer technique, and on cell line (Du-145). Studies performed with the Langmuir method indicate that both the investigated drugs have the affinity to the monolayer mimicking prostate cancer membrane (composed of cholesterol:POPC = 0.428) and the drug-membrane interactions are stronger for erucylphosphocholine as compared to hexadecylphosphocholine. Moreover, both studied drugs were found to fluidize the model membrane, which may lead to apoptosis. Indeed, biological studies confirmed that in Du-145 cell line both investigated alkylphosphocholines cause cell death primarily by apoptosis while necrotic cells constitute only a small percentage of APC-treated cells.

Repurposing miltefosine for the treatment of immune-mediated disease?

Miltefosine is an ether lipid that was initially developed for cancer treatment in the early 1980s. Miltefosine largely failed development for oncology, although it was approved for the topical treatment of breast cancer metastasis. It was subsequently discovered that miltefosine is a highly effective treatment of visceral Leishmaniasis, a parasitic disease that affects millions worldwide and causes an estimated 30,000 fatalities each year. Oral treatment with miltefosine is generally well tolerated and has relatively few adverse effects. The exact mechanism of action of miltefosine treatment is still under investigation. Its close resemblance to phospholipids allows it to be quickly taken up by cell membranes and affect related processes, such as lipid metabolism and signaling through lipid rafts. These processes play an important role in the immune response and it comes as no surprise that miltefosine has been successfully tested for the treatment of a number of immune-mediated diseases in preclinical models of disease. Drug repurposing of miltefosine for immune-mediated diseases may provide an opportunity to expand the limited number of drugs that are currently available for therapeutic use.

AKT kinase pathway: a leading target in cancer research

AKT1, a serine/threonine-protein kinase also known as AKT kinase, is involved in the regulation of various signalling downstream pathways including metabolism, cell proliferation, survival, growth, and angiogenesis. The AKT kinases pathway stands among the most important components of cell proliferation mechanism. Several approaches have been implemented to design an efficient drug molecule to target AKT kinases, although the promising results have not been confirmed. In this paper we have documented the detailed molecular insight of AKT kinase protein and proposed a probable doxorubicin based approach in inhibiting miR-21 based cancer cell proliferation. Moreover, the inhibition of miR-21 activation by raising the FOXO3A concentration seems promising in reducing miR-21 mediated cancer activation in cell. Furthermore, the use of next generation sequencing and computational drug design approaches will greatly assist in designing a potent drug molecule against the associated cancer cases.

Perifosine treatment in chronic lymphocytic leukemia: results of a phase II clinical trial and in vitro studies

Abstract Because of the importance of the phosphoinositide 3-kinase (PI3K)/AKT pathway in chronic lymphocytic leukemia (CLL), we evaluated in vitro cytotoxicity induced by perifosine, an AKT inhibitor, in CLL lymphocytes and found that the mean 50% effective dose (ED50) was 313 nM. We then performed a phase II trial of perifosine in patients with relapsed/refractory CLL to assess response, outcomes, toxicity and ex vivo correlative measures. After 3 months of treatment, six of eight patients showed stable disease, one achieved a partial response and one had progressive disease. Median event-free survival and overall survival in all patients treated were 3.9 and 9.7 months. Adverse events included hematologic, infectious/fever, pain, gastrointestinal and constitutional toxicities. Unexpectedly, AKT phosphorylation in CLL lymphocytes from treated patients was not correlated with response. Additionally, perifosine did not inhibit AKT phosphorylation in cultured CLL lymphocytes. Perifosine is cytotoxic to CLL cells in vitro, and largely induces stabilized disease in vivo, with an AKT-independent mechanism.

Targeting the PI3-kinase/Akt/mTOR signaling pathway

This article presents an overview of the PI3K/Akt/mTOR signaling pathway. As a central regulator of cell growth, protein translation, survival, and metabolism, activation of this signaling pathway contributes to the pathogenesis of many tumor types. Biochemical and genetic aberrations of this pathway observed in various cancer types are explored. Last, pathway inhibitors both in development and already approved by the Food and Drug Administration are discussed.

Perifosine inhibits lipopolysaccharide (LPS)-induced tumor necrosis factor (TNF)-α production via regulation multiple signaling pathways: new implication for Kawasaki disease (KD) treatment

Kawasaki disease (KD) is a multisystem vasculitis of unknown etiology, with coronary artery aneurysms occurring in majority of untreated cases. Tumor necrosis factor (TNF)-α is the pleiotropic inflammatory cytokine elevated during the acute phase of KD, which induces damage to vascular endothelial cells to cause systemic vasculitis. We here investigated the potential role of perifosine, a novel Akt inhibitor, on TNFα expression in LPS-stimulated macrophages and in ex-vivo cultured peripheral blood mononuclear cells (PBMCs) of acute KD patients. Here, we found that perifosine inhibited LPS-induced TNFα expression and production in mouse macrophages (RAW 264.7 cells and bone marrow-derived macrophages (BMDMs)). Meanwhile, perifosine administration down-regulated TNFα production in PBMCs isolated from acute KD patients. For the mechanism study, we found that perifosine significantly inhibited Akt and ERK/mitogen-activated protein kinases (MAPK) signaling, while activating AMP-activated protein kinase (AMPK) signaling in both patients' PBMCs and LPS-stimulated macrophages. Interestingly, although perifosine is generally known as an Akt inhibitor, our data suggested that ERK inhibition and AMPK activation, but not Akt inactivation were possibly involved in perifosine-mediated inhibition against TNFα production in monocytes. In conclusion, our data suggested that perifosine significantly inhibited TNFα production via regulation multiple signaling pathways. The results of this study should have significant translational relevance in managing this devastating disease.

Induction of death receptor 5 expression in tumor vasculature by perifosine restores the vascular disruption activity of TRAIL-expressing CD34(+) cells

The proapoptotic death receptor 5 (DR5) expressed by tumor associated endothelial cells (TECs) mediates vascular disrupting effects of human CD34(+) cells engineered to express membrane-bound tumor necrosis factor-related apoptosis-inducing ligand (CD34-TRAIL (+) cells) in mice. Indeed, lack of DR5 on TECs causes resistance to CD34-TRAIL (+) cells. By xenografting in nonobese diabetic/severe combined immunodeficient mice the TRAIL-resistant lymphoma cell line SU-DHL-4V, which generates tumors lacking endothelial DR5 expression, here we demonstrate for the first time that the Akt inhibitor perifosine induces in vivo DR5 expression on TECs, thereby overcoming tumor resistance to the vascular disruption activity of CD34-TRAIL (+) cells. In fact, CD34-TRAIL (+) cells combined with perifosine, but not CD34-TRAIL (+) cells alone, exerted marked antivascular effects and caused a threefold increase of hemorrhagic necrosis in SU-DHL-4V tumors. Consistent with lack of DR5 expression, CD34-TRAIL (+) cells failed to affect the growth of SU-DHL-4V tumors, but CD34-TRAIL (+) cells plus perifosine reduced tumor volumes by 60 % compared with controls. In view of future clinical studies using membrane-bound TRAIL, our results highlight a strategy to rescue patients with primary or acquired resistance due to the lack of DR5 expression in tumor vasculature.

Perifosine induces cell apoptosis in human osteosarcoma cells: new implication for osteosarcoma therapy?

Despite the advances of adjuvant chemotherapy and significant improvement of survival, the prognosis for patients with osteosarcoma is generally poor. The search for more effective anti-osteosarcoma agents is necessary and urgent. Here we report that perifosine induces cell apoptosis and growth inhibition in cultured human osteosarcoma cells. Perifosine blocks Akt/mTOR complex 1 (mTORC1) signaling, while promoting caspase-3, c-Jun N-terminal kinases (JNK), and p53 activation. Further, perifosine inhibits survivin expression probably by disrupting its association with heat shock protein-90 (HSP-90). These signaling changes together were responsible for a marked increase of osteosarcoma cell apoptosis and growth inhibition. Finally, we found that a low dose of perifosine enhanced etoposide- or doxorubicin-induced anti-OS cells activity. The results together suggest that perifosine might be used as a novel and effective anti-osteosarcoma agent.

Phase I study of UCN-01 and perifosine in patients with relapsed and refractory acute leukemias and high-risk myelodysplastic syndrome

BACKGROUND

The PI3K-Akt pathway is frequently activated in acute leukemias and represents an important therapeutic target. UCN-01 and perifosine are known to inhibit Akt activation.

METHODS

The primary objective of this phase I study was to determine the maximum tolerated dose (MTD) of UCN-01 given in combination with perifosine in patients with advanced acute leukemias and myelodysplastic syndrome. Secondary objectives included safety, pharmacokinetics, pharmacodynamics, and efficacy. Perifosine 150 mg every 6 h was given orally on day 1 followed by 100 mg once a day continuously in 28-day cycles. UCN-01 was given intravenously over 3 h on day 4 at three dose levels (DL1=40 mg/m(2); DL2=65 mg/m(2); DL3=90 mg/m(2)).

RESULTS

Thirteen patients were treated (DL1, n=6; DL2, n=4; DL3, n=3) according to a traditional "3+3" design. Two patients at the DL3 experienced dose-limiting toxicity including grade 3-4 pericardial effusion, hypotension, hyperglycemia, hyperkalemia, constitutional symptoms and grade 5 pneumonitis. Other frequent toxicities were grade 1-2 nausea, diarrhea, vomiting, fatigue and hyperglycemia. The MTD was determined to be UCN-01 65 mg/m(2) with perifosine 100 mg a day. No appreciable direct Akt inhibition could be demonstrated in patients' mononuclear cells using Western blot, however, reduced phosphorylation of the downstream target ribosomal protein S6 in leukemic blasts was noted by intracellular flow cytometry. No objective responses were observed on this study.

CONCLUSION

UCN-01 and perifosine can be safely administered, but this regimen lacked clinical efficacy. This approach may have failed because of insufficient Akt inhibition in vivo.

Perifosine in renal cell carcinoma

INTRODUCTION

Perifosine is an oral alkylphospholipid which has recently been assessed clinically in patients with advanced renal cell carcinoma (RCC). Perifosine acts primarily by attenuating the activation of Akt by preventing its pleckstrin homology (PH) domain-dependent localization to the cell membrane.

AREAS COVERED

This review summarizes the therapeutic landscape of RCC including the proposed role of perifosine in patients with advanced RCC. The mechanism of action, pharmacodynamics, pharmacokinetics, clinical efficacy in RCC and safety of perifosine are all addressed as well.

EXPERT OPINION

Although perifosine has clear clinical activity in RCC, it is not superior to currently available agents and therefore does not appear worthy of further clinical development in RCC as a single agent. Given the observed efficacy and mild toxicity, however, perifosine may have a role in RCC therapy given in combination with other molecularly targeted agents.

Perifosine , an oral, anti-cancer agent and inhibitor of the Akt pathway: mechanistic actions, pharmacodynamics, pharmacokinetics, and clinical activity

INTRODUCTION

Perifosine is a novel targeted oral Akt inhibitor currently in Phase III clinical development for treatment of colorectal cancer (CRC, in combination with capecitabine) and multiple myeloma (MM, in combination with bortezomib and dexamethasone).

AREAS COVERED

The mechanism, preclinical testing, and clinical activity of perifosine in CRC and MM are discussed, with supportive pharmacokinetic information presented. Appropriate literature searches were carried out for background and discussion purposes.

EXPERT OPINION

In preclinical models, perifosine has been shown to target phosphatidylinositol 3-kinase-Akt signaling. In CRC cell lines, preclinical studies indicate that perifosine may enhance the cytotoxic effects of fluorouracil, likely primarily through the nuclear transcription factor-kappa B pathway. A placebo-controlled Phase II randomized trial of capecitabine ± perifosine in previously treated patients with metastatic CRC showed the combination to be superior. In MM, Phase I/II clinical trials have established the optimal dosing schedule for perifosine and bortezomib in combination, and demonstrated that perifosine can sensitize to, or overcome resistance to, bortezomib, associated with prolonged responses and a favorable side effect profile. Ultimately, the favorable tolerability of perifosine will allow for its testing in combination with multiple targeted therapies to improve PFS and OS, which represent an important unmet need in these populations.

mTOR kinase inhibitors as a treatment strategy in hematological malignancies

The mammalian target of rapamycin (mTOR) kinase is a key element of intracellular signal transduction, responsible for the regulation of cell growth and proliferation. Since abnormal activation of the mTOR pathway was found in several tumors, including human malignancies, it may be an attractive target for antineoplastic treatment. The first identified mTOR inhibitor was rapamycin (sirolimus). Subsequently, the most potent rapamycin analogues (rapalogues), such as everolimus, temsirolimus and deforolimus, have been developed. After encouraging preclinical experiments, several clinical trials testing the rapalogues in monotherapy or in combinations with other cytotoxic agents have been conducted in patients with hematological malignancies. Results of these studies, described in this review, indicate that inhibition of the mTOR pathway may be a very promising strategy of anti-tumor treatment in several types of lymphomas and leukemias. Recently, a second generation of more effective mTOR inhibitors has been developed. These are currently being assessed in preclinical, Phase I or I/II clinical studies.

Two phase 2 trials of the novel Akt inhibitor perifosine in patients with advanced renal cell carcinoma after progression on vascular endothelial growth factor-targeted therapy

BACKGROUND

The clinical activity of allosteric inhibitors of mammalian target of rapamycin (mTOR) inhibitors in renal cell carcinoma (RCC) may be limited by upstream activation of phosphatidylinositol 3 (PI3)-kinase/Akt resulting from mTOR1 inhibition. On the basis of this rationale, 2 independent phase 2 trials (Perifosine 228 and 231) were conducted to assess the efficacy and safety of the novel Akt inhibitor perifosine in patients with advanced RCC who had failed on previous vascular endothelial growth factor (VEGF)-targeted therapy.

METHODS

In the Perifosine 228 trial, 24 patients with advanced RCC received oral perifosine (100 mg daily). Perifosine 231 enrolled 2 groups that received daily oral perifosine (100 mg daily): Group A comprised 32 patients who had received no prior mTOR inhibitor, and Group B comprised 18 patients who had received 1 prior mTOR inhibitor.

RESULTS

In the Perifosine 228 trial, 1 patient achieved a partial response (objective response rate, 4%; 95% confidence interval, 0.7%-20%), and 11 patients (46%) had stable disease as their best response. The median progression-free survival was 14.2 weeks (95% confidence interval, 7.7-21.6 weeks). In the Perifosine 231 trial, 5 patients achieved a partial response (objective response rate, 10%; 95% confidence interval, 4.5%-22.2%) and 16 patients (32%) had stable disease as their best response. The median progression-free survival was 14 weeks (95% confidence interval, 12.9, 20.7 weeks). Overall, perifosine was well tolerated, and there were very few grade 3 and 4 events. The most common toxicities included nausea, diarrhea, musculoskeletal pain, and fatigue.

CONCLUSIONS

Although perifosine demonstrated activity in patients with advanced RCC after failure on VEGF-targeted therapy, its activity was not superior to currently available second-line agents. Nonetheless, perifosine may be worthy of further study in RCC in combination with other currently available therapies.

Perifosine plus docetaxel in patients with platinum and taxane resistant or refractory high-grade epithelial ovarian cancer

OBJECTIVES

On the basis of reversal of taxane resistance with AKT inhibition, we initiated a phase I trial of the AKT inhibitor perifosine with docetaxel in taxane and platinum-resistant or refractory epithelial ovarian cancer.

METHODS

Patients with pathologically confirmed high-grade epithelial ovarian cancer (taxane resistant, n=10; taxane refractory, n=11) were enrolled. Peripheral blood samples and tumor biopsies were obtained and (18)F-FDG-PET and DCE-MRI scans were performed for pharmacodynamic and imaging studies.

RESULTS

Patients received a total of 42 treatment cycles. No dose-limiting toxicity was observed. The median progression-free survival and overall survival were 1.9 months and 4.5 months, respectively. One patient with a PTEN mutation achieved a partial remission (PR) for 7.5 months, and another patient with a PIK3CA mutation had stable disease (SD) for 4 months. Two other patients without apparent PI3K pathway aberrations achieved SD. Two patients with KRAS mutations demonstrated rapid progression. Decreased phosphorylated S6 correlated with (18)F-FDG-PET responses.

CONCLUSIONS

Patients tolerated perifosine 150 mg PO daily plus docetaxel at 75 mg/m(2) every 4 weeks. Further clinical evaluation of effects of perifosine with docetaxel on biological markers and efficacy in patients with ovarian cancer with defined PI3K pathway mutational status is warranted.

Interleukin-6, osteopontin and Raf/MEK/ERK signaling modulate the sensitivity of human myeloma cells to alkylphosphocholines

Alkylphosphocholines are highly active against multiple myeloma (MM) cells in vitro and are devoid of myelotoxicity. Little is known about the determinants of MM cell responsiveness or resistance to these drugs. In this study we investigated the effects of disease-relevant cytokines, such as interleukin-6 (IL-6) and osteopontin (OPN), on the in vitro antimyeloma activity of erufosine and perifosine. The role of the Raf/MEK/ERK pathway was also studied. Exogenous IL-6 reduced the cytotoxicity of erufosine against OPM-2 cells and, to a smaller extent, against U-266 cells. This was accompanied by inhibition of apoptosis in OPM-2 cells. The efficacy of perifosine was similarly affected, but to a greater extent. IL-6 slightly enhanced the sensitivity of RPMI-8226 cells to erufosine, thus emphasizing the heterogeneity of MM. Induced overexpression of OPN isoforms made OPM-2 cells less sensitive to erufosine. In all cases of IL-6- or OPN-induced resistance, the effective concentrations of erufosine were still within the clinically achievable range. Like other alkylphosphocholines, erufosine enhanced Raf/MEK/ERK signaling in MM cells but in some cases this contributed to cytotoxicity.

Emerging treatment options for the treatment of neuroblastoma: potential role of perifosine

Achieving a cure for high-risk neuroblastoma, the most common extracranial solid tumor in children, remains a formidable task despite the recent addition of antibody-mediated anti-GD2 immunotherapy to established multimodality therapy. The PI3K/Akt pathway is a pivotal signaling pathway utilized by a plethora of receptor tyrosine kinases that contribute to the aggressive phenotype of high-risk neuroblastoma. Akt is aberrantly activated in high-risk neuroblastoma and is therefore an attractive therapeutic target. Perifosine is the best-characterized Akt inhibitor in preclinical studies and in clinical trials in adults, although safety in children is not yet confirmed. It is a synthetic third-generation alkylphospholipid with good oral bioavailability and modest side effects. Perifosine targets the lipid-binding PH domain of Akt and inhibits the translocation of Akt to the cell membrane, an essential step for Akt activation. It decreases Akt phosphorylation and increases caspase-dependent apoptosis in neuroblastoma cell lines, inhibits growth of neuroblastoma xenografts, and overcomes RTK/ligand-mediated chemoresistance. It is currently being studied in two Phase I clinical trials in children with recurrent or refractory solid tumors including neuroblastoma. In the single agent trial (ClinicalTrials.gov identifier NCT00776867), maximum tolerated dose has not yet been reached and pharmacokinetic data has been accrued. In the second study (ClinicalTrials.gov identifier NCT01049841), patients are treated with a combination of perifosine and the mTOR-inhibitor temsirolimus based on preclinical data showing synergy of the two agents, and the premise that direct Akt inhibition may overcome Akt activation secondary to mTOR inhibition. Based on results from adult trials, it is unlikely that perifosine alone will produce dramatic therapeutic effects against high-risk neuroblastoma. However, given the recent encouraging early-phase combination therapy results in adults with multiple myeloma and colorectal carcinoma, rational perifosine-containing combination regimens hold promise for neuroblastoma therapy. These will be explored after safety in children is established in Phase I studies.

Metabolic consequences of treatment with AKT inhibitor perifosine in breast cancer cells

Activation of the PI3K/Akt pathway is associated with the development of numerous human cancers. As a result, many emerging therapies target this pathway. Previous studies have shown that targeting the PI3K/Akt pathway at the level of PI3K is associated with a drop in phosphocholine (PCho) and a reduction in hyperpolarized lactate production. However, the consequences of targeting downstream of PI3K at the level of Akt have not been investigated. Perifosine is an anticancer alkylphospholipid used in clinical trials. It acts by inhibiting phosphorylation of Akt and has been shown to inhibit CTP-phosphocholine cytidyltransferase (CT). The goal of this study was to identify the MRS-detectable metabolic consequences of treatment with perifosine in MCF-7 breast cancer cells. We found that perifosine treatment led to a 51 ± 5% drop in PCho from 30 ± 5 to 15 ± 1 fmol/cell and a comparable drop in de novo synthesized PCho. This was associated with a drop in choline kinase (ChoK) activity and ChoKα expression. CT inhibition could not be ruled out but likely did not contribute to the change in PCho. We also found that intracellular lactate levels decreased from 2.7 ± 0.5 to 1.5 ± 0.3 fmol/cell and extracellular lactate levels dropped by a similar extent. These findings were consistent with a drop in lactate dehydrogenase expression and associated with a drop in activity of the hypoxia inducible factor (HIF)-1α. The drops in PCho and lactate production following perifosine treatment are therefore mediated downstream of Akt by the drop in HIF-1α, which serves as the transcription factor for both ChoK and lactate dehydrogenase. The metabolic changes were confirmed in a second breast cancer cell line, MDA-MB-231. Taken together, these findings indicate that PCho and lactate can serve as noninvasive metabolic biomarkers for monitoring the effects of inhibitors that target the PI3K/Akt pathway, independent of the step that leads to inhibition of HIF-1α.

The Akt signaling pathway: an emerging therapeutic target in malignant melanoma

Studies using cultured melanoma cells and patient tumor biopsies have demonstrated deregulated PI3 kinase-Akt3 pathway activity in ~70% of melanomas. Furthermore, targeting Akt3 and downstream PRAS40 has been shown to inhibit melanoma tumor development in mice. Although these preclinical studies and several other reports using small interfering RNAs and pharmacological agents targeting key members of this pathway have been shown to retard melanoma development, analysis of early Phase I and Phase II clinical trials using pharmacological agents to target this pathway demonstrate the need for (1) selection of patients whose tumors have PI3 kinase-Akt pathway deregulation, (2) further optimization of therapeutic agents for increased potency and reduced toxicity, (3) the identification of additional targets in the same pathway or in other signaling cascades that synergistically inhibit the growth and progression of melanoma, and (4) better methods for targeted delivery of pharmaceutical agents inhibiting this pathway. In this review we discuss key potential targets in PI3K-Akt3 signaling, the status of pharmacological agents targeting these proteins, drugs under clinical development, and strategies to improve the efficacy of therapeutic agents targeting this pathway.

Novel inhibitors of AKT: assessment of a different approach targeting the pleckstrin homology domain

Protein kinase B/AKT plays a central role in cancer. The serine/threonine kinase is overexpressed or constitutively active in many cancers and has been validated as a therapeutic target for cancer treatment. However, targeting the kinase activity has revealed itself to be a challenge due to non-selectivity of the compounds towards other kinases. This review summarizes other approaches scientists have developed to inhibit the activity and function of AKT. They consist in targeting the pleckstrin homology (PH) domain of AKT. Indeed, upon the generation of 3-phosphorylated phosphatidylinositol phosphates (PI3Ps) by PI3-kinase (PI3K), AKT translocates from the cytosol to the plasma membrane and binds to the PI3Ps via its PH domain. Thus, several analogs of PI3Ps (PI Analogs or PIAs), alkylphospholipids (APLs), such as edelfosine or inositol phophates (IPs) have been described that inhibit the binding of the PH domain to PI3Ps. Recent allostertic inhibitors and small molecules that do not bind the kinase domain but affect the kinase activity of AKT, presumably by interacting with the PH domain, have been also identified. Finally, several drug screening studies spawned novel chemical scaffolds that bind the PH domain of AKT. Together, these approaches have been more or less sucessfull in vitro and to some extent translated in preclinical studies. Several of these new AKT PH domain inhibitors exhibit promising anti-tumor activity in mouse models and some of them show synergy with ionizing radiation and chemotherapy. Early clinical trials have started and results will attest to the validity and efficacy of such approaches in the near future.

In vitro effects of perifosine, bortezomib and lenalidomide against hematopoietic progenitor cells from healthy donors

The novel AKT inhibitor perifosine possesses myelopoiesis-stimulating effects in rodents. We studied the in vitro effects of the novel agents perifosine, bortezomib and lenalidomide in addition to adriamycin against normal human hematopoietic progenitor cells (HPC) using different clonogenic and non-clonogenic assays. All agents inhibited colony-forming unit (CFU) formation, perifosine inhibiting mainly CFU-granulocyte/macrophage formation and the other agents burst-forming unit-erythroid formation. Perifosine combined with lenalidomide or adriamycin tended to act antagonistically in suppressing CFU formation. Despite their inhibition of CFU formation, perifosine, bortezomib and lenalidomide induced only slight or moderate cytotoxicity in CD34(+) selected HPC, as assessed using different assays such as flow cytometry-based detection of activated caspases and immunohistochemistry studies (e.g., Ki-67 staining). In contrast to its myelopoiesis-stimulating effects in rodents, perifosine--like bortezomib and lenalidomide--suppresses the clonogenic potential of HPC from healthy donors in vitro and thus probably plays no role in preventing neutropenia or in shorting its duration after intensive chemotherapy. However, all these novel agents typically induce only slight or moderate suppression of the clonogenic potential or loss of viability of normal HPC at clinically achievable plasma concentrations, assuming that hematoxicity is manageable and functional HPC can be collected after treatment with these compounds.

Co-administration of perifosine with paclitaxel synergistically induces apoptosis in ovarian cancer cells: more than just AKT inhibition

Here we report an oral alkylphospholipid perifosine dramatically sensitizes chemo-resistant ovarian cancer cells to paclitaxel induced cell death and apoptosis in vitro. We found that co-administration perifosine with paclitaxel in human ovarian cancer cells led to the inhibition of AKT/mTOR complex 1 (mTORC1), a marked increase in ceramide and reactive oxygen species (ROS) production, and a striking increase in the activation of pro-apoptosis pathways, including caspase 3, c-Jun N-terminal kinases (JNK) and AMP-activated protein kinase (AMPK). These signaling events together caused a marked increase of cancer cell apoptosis. Combining paclitaxel with perifosine may represent a novel anti-ovarian cancer strategy.

Evaluating rational non-cross-resistant combination therapy in advanced clear cell renal cell carcinoma: combined mTOR and AKT inhibitor therapy

PURPOSE

Inhibition of the mammalian target of rapamycin (mTOR), a regulator of hypoxia inducible factor (HIF), is an established therapy for advanced renal cell cancer (RCC). Inhibition of mTOR results in compensatory AKT activation, a likely resistance mechanism. We evaluated whether addition of the Akt inhibitor perifosine to the mTOR inhibitor rapamycin would synergistically inhibit RCC.

METHODS

Select RCC cell lines were studied [786-O, A498 (VHL mutant), CAKI-1 (VHL wild type), and 769-P (VHL methylated)] with single agent and combination therapy. Growth inhibition was assessed by MTT and cell cycling by flow cytometry. Phospho-AKT (S473) and HIF-2α were assessed by Western blot. Total RNA was isolated from 786-O cells subjected to single agent and combination treatments. In these cells, genome-wide expression profiles were assessed, and real-time PCR was used to confirm a limited set of expression results.

RESULTS

Three out of four cell lines (CAKI-1, 769-P, and 786-O) were sensitive to single-agent perifosine with 50% inhibitory concentrations ranging from 5 to 10 μM. Perifosine blocked phosphorylation of AKT induced by rapamycin and inhibited HIF-2α expression in 786-O and CAKI-1. Combined treatment resulted in sub-additive growth inhibition. GeneChip analysis and pathway modeling revealed inhibition of the IL-8 pathway by these agents, concomitant with up-regulation of the KLF2 gene, a known suppressor of HIF1α.

CONCLUSIONS

Perifosine is active in select RCC lines, abrogating the induction of AKT phosphorylation mediated by mTOR inhibition. Combined mTOR and AKT inhibition resulted in the modulation of pro-angiogenesis pathways, providing a basis for future investigations.

New targeted therapies for renal cell carcinoma

INTRODUCTION

The aim of treatment in metastatic renal cell carcinoma is palliation. In the last 5 years, multiple targeted agents have been developed which have resulted in prolongation of patients' lives, but complete responses remain rare. New therapies and approaches are required to further improve the prognosis for patients with this disease.

AREAS COVERED

This review discusses the molecular targets in renal cell carcinoma relevant to the development of new treatments and describes the progress of novel therapies. The evidence is compiled from the PubMed database and proceedings of scientific meetings, searched up to December 2010.

EXPERT OPINION

A multitude of experimental agents are in clinical development and offer theoretical advantages over those currently in use. It is hoped that these treatments will result in better long-term control of metastatic renal cell carcinoma, with improved side effect profiles, but curative treatment in this disease remains elusive until the mechanisms underlying response and resistance to therapy are elucidated. Progress in the field has been limited by inadequate tissue collection within clinical trials; current and future clinical trial design will incorporate a larger translational component in an attempt to establish predictive biomarkers.

In vitro cytotoxicity of the novel antimyeloma agents perifosine, bortezomib and lenalidomide against different cell lines

The novel AKT inhibitor perifosine, a synthetic alkylphospholipid, is currently being investigated in clinical trials for the treatment of different hematological and oncological malignancies. The in vitro cytotoxicity of perifosine, bortezomib and lenalidomide against 6 cell lines derived from hematological malignancies was investigated using trypan blue staining, flow cytometry-based detection of activated caspases, Annexin V assays, immunohistochemistry studies (KI-67 and caspase-3 staining) and the immature-myeloid-information (IMI) technique. Perifosine and bortezomib induced concentration- and time-dependent cytotoxicity in all cell lines tested. Perifosine together with bortezomib largely exerted additive or synergistic effects with combination indices ranging from 1.13 to 0.22 for combined efficacies of 25% to 75% after 24-hour incubation. Lenalidomide-triggered cytotoxicity was low in all cell lines tested with any assay (less than 10% compared to the negative control). Finally, perifosine, but not bortezomib or lenalidomide, significantly increased the number of cells detected in the IMI channel. Perifosine and bortezomib- but not lenalidomide- trigger substantial cytotoxicity by caspase activation and mainly act additively or synergistically. The IMI technique might be a useful tool for studying cytotoxicity of agents like perifosine that interact mainly with the cellular membrane.