Ruihong Chen

Consensus Recommendations for Current Treatments and Accelerating Clinical Trials for Patients with Neurofibromatosis Type 2

Neurofibromatosis type 2 (NF2) is a tumor suppressor syndrome characterized by bilateral vestibular schwannomas (VS) which often result in deafness despite aggressive management. Meningiomas, ependymomas, and other cranial nerve and peripheral schwannomas are also commonly found in NF2 and collectively lead to major neurologic morbidity and mortality. Traditionally, the overall survival rate in patients with NF2 is estimated to be 38% at 20 years from diagnosis. Hence, there is a desperate need for new, effective therapies. Recent progress in understanding the molecular basis of NF2 related tumors has aided in the identification of potential therapeutic targets and emerging clinical therapies. In June 2010, representatives of the international NF2 research and clinical community convened under the leadership of Drs. D. Gareth Evans (University of Manchester) and Marco Giovannini (House Research Institute) to review the state of NF2 treatment and clinical trials. This manuscript summarizes the expert opinions about current treatments for NF2 associated tumors and recommendations for advancing therapies emerging from that meeting. The development of effective therapies for NF2 associated tumors has the potential for significant clinical advancement not only for patients with NF2 but for thousands of neuro‐oncology patients afflicted with these tumors.

Consensus Recommendations to Accelerate Clinical Trials for Neurofibromatosis Type 2

Purpose: Neurofibromatosis type 2 (NF2) is a rare autosomal dominant disorder associated primarily with bilateral schwannomas seen on the superior vestibular branches of the eighth cranial nerves. Significant morbidity can result from surgical treatment of these tumors. Meningiomas, ependymomas, and other benign central nervous system tumors are also common in NF2. The lack of effective treatments for NF2 marks an unmet medical need. Experimental Design: Here, we provide recommendations from a workshop, cochaired by Drs. D. Gareth Evans and Marco Giovannini, of 36 international researchers, physicians, representatives of the biotechnology industry, and patient advocates on how to accelerate progress toward NF2 clinical trials. Results: Workshop participants reached a consensus that, based on current knowledge, the time is right to plan and implement NF2 clinical trials. Obstacles impeding NF2 clinical trials and how to address them were discussed, as well as the candidate therapeutic pipeline for NF2. Conclusions: Both phase 0 and phase II NF2 trials are near-term options for NF2 clinical trials. The number of NF2 patients in the population remains limited, and successful recruitment will require ongoing collaboration efforts between NF2 clinics. (Clin Cancer Res 2009;15(16):5032–9)

Inhibition of HSP90 with pochoximes: SAR and structure-based insights.

The pochoximes, based on the radicicol pharmacophore, are potent inhibitors of heat shock protein 90 (HSP90) that retain their activity in vivo. Herein we report an extended library that broadly explores the structure–activity relationship (SAR) of the pochoximes with four points of diversity. Several modifications were identified that afford improved cellular efficacy, new opportunities for conjugation, and further diversifications. Cocrystal structures of pochoximes A and B with HSP90 show that pochoximes bind to a different conformation of HSP90 than radicicol and provide a rationale for the enhanced affinity of the pochoximes relative to radicicol and the pochonins.

The Novel Hsp90 Inhibitor NXD30001 Induces Tumor Regression in a Genetically Engineered Mouse Model of Glioblastoma Multiforme

Glioblastoma multiforme (GBM) has an abysmal prognosis. We now know that the epidermal growth factor receptor (EGFR) signaling pathway and the loss of function of the tumor suppressor genes p16Ink4a/p19ARF and PTEN play a crucial role in GBM pathogenesis: initiating the early stages of tumor development, sustaining tumor growth, promoting infiltration, and mediating resistance to therapy. We have recently shown that this genetic combination is sufficient to promote the development of GBM in adult mice. Therapeutic agents raised against single targets of the EGFR signaling pathway have proven rather inefficient in GBM therapy, showing the need for combinatorial therapeutic approaches. An effective strategy for concurrent disruption of multiple signaling pathways is via the inhibition of the molecular chaperone heat shock protein 90 (Hsp90). Hsp90 inhibition leads to the degradation of so-called client proteins, many of which are key effectors of GBM pathogenesis. NXD30001 is a novel second generation Hsp90 inhibitor that shows improved pharmacokinetic parameters. Here we show that NXD30001 is a potent inhibitor of GBM cell growth in vitro consistent with its capacity to inhibit several key targets and regulators of GBM biology. We also show the efficacy of NXD30001 in vivo in an EGFR-driven genetically engineered mouse model of GBM. Our findings establish that the Hsp90 inhibitor NXD30001 is a therapeutically multivalent molecule, whose actions strike GBM at the core of its drivers of tumorigenesis and represent a compelling rationale for its use in GBM treatment. Mol Cancer Ther; 9(9); 2618–26. ©2010 AACR.

Therapeutic Potential of HSP90 Inhibition for Neurofibromatosis type 2

Purpose: The growth and survival of neurofibromatosis type 2 (NF2)–deficient cells are enhanced by the activation of multiple signaling pathways including ErbBs/IGF-1R/Met, PI3K/Akt, and Ras/Raf/Mek/Erk1/2. The chaperone protein HSP90 is essential for the stabilization of these signaling molecules. The aim of the study was to characterize the effect of HSP90 inhibition in various NF2-deficient models. Experimental Design: We tested efficacy of the small-molecule NXD30001, which has been shown to be a potent HSP90 inhibitor. The antiproliferative activity of NXD30001 was tested in NF2-deficient cell lines and in human primary schwannoma and meningioma cultures in vitro. The antitumor efficacy of HSP90 inhibition in vivo was verified in two allograft models and in one NF2 transgenic model. The underlying molecular alteration was further characterized by a global transcriptome approach. Results: NXD30001 induced degradation of client proteins in and suppressed proliferation of NF2-deficient cells. Differential expression analysis identified subsets of genes implicated in cell proliferation, cell survival, vascularization, and Schwann cell differentiation whose expression was altered by NXD30001 treatment. The results showed that NXD30001 in NF2-deficient schwannoma suppressed multiple pathways necessary for tumorigenesis. Conclusions: HSP90 inhibition showing significant antitumor activity against NF2-related tumor cells in vitro and in vivo represents a promising option for novel NF2 therapies. Clin Cancer Res; 19(14); 3856–70. ©2013 AACR.

Synthesis of pochoxime prodrugs as potent HSP90 inhibitors

Pochoximes are potent inhibitors of heat shock protein 90 (HSP90) based on the radicicol pharmacophores. Herein we present a pharmacokinetics and pharmacodynamics evaluation of this compound series as well as a phosphate prodrug strategy to facilitate formulation and improve oral bioavailability.

A novel small molecule HSP90 inhibitor, NXD30001, differentially induces heat shock proteins in nervous tissue in culture and in vivo

Heat shock proteins (HSPs) are attractive therapeutic targets for neurodegenerative diseases, such as amyotrophic lateral sclerosis (ALS), characterized by aberrant formation of protein aggregates. Although motor neurons have a high threshold for activation of HSP genes, HSP90 inhibitors are effective inducers. This study evaluated NXD30001, a novel, small molecule HSP90 inhibitor based on the radicicol backbone, for its ability to induce neuronal HSPs and for efficacy in an experimental model of ALS based on mutations in superoxide-dismutase 1 (SOD1). In motor neurons of dissociated murine spinal cord cultures, NXD30001-induced expression of HSP70/HSPA1 (iHSP70) and its co-chaperone HSP40/DNAJ through activation of HSF1 and exhibited a protective profile against SOD1G93A similar to geldanamycin, but with less toxicity. Treatment prevented protein aggregation, mitochondrial fragmentation, and motor neuron death, important features of mutant SOD1 toxicity, but did not effectively prevent aberrant intracellular Ca2+ accumulation. NXD30001 distributed to brain and spinal cord of wild-type and SOD1G93A transgenic mice following intraperitoneal injection; however, unlike in culture, in vivo levels of SOD1 were not reduced. NXD30001-induced expression of iHSP70 in skeletal and cardiac muscle and, to a lesser extent, in kidney, but not in liver, spinal cord, or brain, with either single or repeated administration. NXD30001 is a very useful experimental tool in culture, but these data point to the complex nature of HSP gene regulation in vivo and the necessity for early evaluation of the efficacy of novel HSP inducers in target tissues in vivo.