Phase I pharmacokinetic and pharmacodynamic study of the pan-PI3K/mTORC vascular targeted pro-drug SF1126 in patients with advanced solid tumours and B-cell malignancies

The combination of novel targeted molecular agents and radiation in the treatment of pediatric gliomas

Brain tumors are the most common solid pediatric malignancy. For high-grade, recurrent, or refractory pediatric brain tumors, radiation therapy (XRT) is an integral treatment modality. In the era of personalized cancer therapy, molecularly targeted agents have been designed to inhibit pathways critical to tumorigenesis. Our evolving knowledge of genetic aberrations in pediatric gliomas is being exploited with the use of specific targeted inhibitors. These agents are additionally being combined with XRT to increase the efficacy and duration of local control. In this review, we discuss novel agents targeting three different pathways in gliomas, and their potential combination with XRT. BRAF is a serine/threonine kinase in the RAS/RAF/MAPK kinase pathway, which is integral to cellular division, survival, and metabolism. Two-thirds of pilocytic astrocytomas, a low-grade pediatric glioma, contain a translocation within the BRAF gene called KIAA1549:BRAF that causes an overactivation of the MEK/MAPK signaling cascade. In vitro and in vivo data support the use of MEK or mammalian target of rapamycin (mTOR) inhibitors in low-grade gliomas expressing this translocation. Additionally, 15-20% of high-grade pediatric gliomas express BRAF V600E, an activating mutation of the BRAF gene. Pre-clinical in vivo and in vitro data in BRAF V600E gliomas demonstrate dramatic cooperation between XRT and small molecule inhibitors of BRAF V600E. Another major signaling cascade that plays a role in pediatric glioma pathogenesis is the PI3-kinase (PI3K)/mTOR pathway, known to be upregulated in the majority of high- and low-grade pediatric gliomas. Dual PI3K/mTOR inhibitors are in clinical trials for adult high-grade gliomas and are poised to enter studies of pediatric tumors. Finally, many brain tumors express potent stimulators of angiogenesis that render them refractory to treatment. An analog of thalidomide, CC-5103 increases the secretion of critical cytokines of the tumor microenvironment, including IL-2, IFN-γ, TNF-α, and IL-10, and is currently being evaluated in clinical trials for the treatment of recurrent or refractory pediatric central nervous system tumors. In summary, several targeted inhibitors with radiation are currently under investigation in both translational bench research and early clinical trials. This review article summarizes the molecular rationale for, and the pre-clinical data supporting the combinations of these targeted agents with other anti-cancer agents and XRT in pediatric gliomas. In many cases, parallels are drawn to molecular mechanisms and targeted inhibitors of adult gliomas. We additionally discuss the potential mechanisms underlying the efficacy of these agents.

Synthesis and cancer stem cell-based activity of substituted 5-morpholino-7H-thieno[3,2-b]pyran-7-ones designed as next generation PI3K inhibitors

Dysregulation of the phosphatidylinositol-3-kinase (PI3K) pathway in a wide range of tumors has made PI3K a consensus target to inhibit as illustrated by more than 15 inhibitors now in clinical trials. Our previous work, built on the early pioneering multikinase inhibitor LY294002, resulted in the only PI3K vascular-targeted PI3K inhibitor prodrug, SF1126, which has now completed Phase I clinical trials. This inhibitor has properties that impart more in vivo activity than should be warranted by its enzymatic potency, which in general is much lower than other clinical stage PI3K inhibitors. We embarked on the exploration of scaffolds that retained such properties while simultaneously exhibiting an increased potency toward PI3K. This work resulted in the discovery of the 5-morpholino-7H-thieno[3,2-b]pyran-7-one system as the foundation of a new compound class of potential PI3K inhibitors having improved potency toward PI3K. The synthesis and cancer stem cell-based activity of these compounds are reported herein.

Targeting the RAS oncogene

INTRODUCTION

The Ras proteins (K-Ras, N-Ras, and H-Ras) are GTPases that function as molecular switches for a variety of critical cellular activities and their function is tightly and temporally regulated in normal cells. Oncogenic mutations in the RAS genes, which create constitutively-active Ras proteins, can result in uncontrolled proliferation or survival in tumor cells.

AREAS COVERED

The paper discusses three therapeutic approaches targeting the Ras pathway in cancer: i) Ras itself, ii) Ras downstream pathways, and iii) synthetic lethality. The most adopted approach is targeting Ras downstream signaling, and specifically the PI3K-AKT-mTOR and Raf-MEK pathways, as they are frequently major oncogenic drivers in cancers with high Ras signaling. Although direct targeting of Ras has not been successful clinically, newer approaches being investigated in preclinical studies, such as RNA interference-based and synthetic lethal approaches, promise great potential for clinical application.

EXPERT OPINION

The challenges of current and emerging therapeutics include the lack of "tumor specificity" and their limitation to those cancers which are "dependent" on aberrant Ras signaling for survival. While the newer approaches have the potential to overcome these limitations, they also highlight the importance of robust preclinical studies and bidirectional translational research for successful clinical development of Ras-related targeted therapies.

An integrin-targeted, pan-isoform, phosphoinositide-3 kinase inhibitor, SF1126, has activity against multiple myeloma in vivo

PURPOSE

Multiple reports point to an important role for the phosphoinositide-3 kinase (PI3K) and AKT signaling pathways in tumor survival and chemoresistance in multiple myeloma (MM). The goals of our study were: (1) to generate the preclinical results necessary to justify a Phase I clinical trial of SF1126 in hematopoietic malignancies including MM and (2) to begin combining pan-PI3K inhibitors with other agents to augment antitumor activity of this class of agent in preparation for combination therapy in Phase I/II trials.

METHODS

We determined the in vitro activity of SF1126 with 16 human MM cell lines. In vivo tumor growth suppression was determined with human myeloma (MM.1R) xenografts in athymic mice. In addition, we provide evidence that SF1126 has pharmacodynamic activity in the treatment of patients with MM.

RESULTS

SF1126 was cytotoxic to all tested MM lines, and potency was augmented by the addition of bortezomib. SF1126 affected MM.1R cell line signaling in vitro, inhibiting phospho-AKT, phospho-ERK, and the hypoxic stabilization of HIF1α. Tumor growth was 94 % inhibited, with a marked decrease in both cellular proliferation (PCNA immunostaining) and angiogenesis (tumor microvessel density via CD31 immunostaining). Our clinical results demonstrate pharmacodynamic knockdown of p-AKT in primary patient-derived MM tumor cells in vivo.

CONCLUSIONS

Our results establish three important points: (1) SF1126, a pan-PI3K inhibitor has potent antitumor activity against MM in vitro and in vivo, (2) SF1126 displays augmented antimyeloma activity when combined with proteasome inhibitor, bortezomib/Velcade(®), and (3) SF1126 blocks the IGF-1-induced activation of AKT in primary MM tumor cells isolated from SF1126-treated patients The results support the ongoing early Phase I clinical trial in MM and suggest a future Phase I trial in combination with bortezomib in hematopoietic malignancies.

mTOR Inhibition: From Aging to Autism and Beyond

The mechanistic target of rapamycin (mTOR) is a highly conserved protein that regulates growth and proliferation in response to environmental and hormonal cues. Broadly speaking, organisms are constantly faced with the challenge of interpreting their environment and making a decision between "grow or do not grow." mTOR is a major component of the network that makes this decision at the cellular level and, to some extent, the tissue and organismal level as well. Although overly simplistic, this framework can be useful when considering the myriad functions ascribed to mTOR and the pleiotropic phenotypes associated with genetic or pharmacological modulation of mTOR signaling. In this review, I will consider mTOR function in this context and attempt to summarize and interpret the growing body of literature demonstrating interesting and varied effects of mTOR inhibitors. These include robust effects on a multitude of age-related parameters and pathologies, as well as several other processes not obviously linked to aging or age-related disease.