Sub lethal levels of MP MUS induce increased levels of

Sub-lethal levels of MP-MUS induce increased levels of mitochondria and mitochondrial MAOB in glioma cells in vitro and in vivo. Cells derived from MP-MUS-treated glioma xenografts harbored dysfunctional mitochondria many generations after treatment. The mitochondria in these cells had increased MAOB expression and increased ROS generation. Thus, glioma cells that survive after one or more cycles of MP-MUS treatment express increased levels of MAOB, rendering these glioma cells more sensitive to MP-MUS therapy. Unlike most chemotherapeutic drugs, which lose their efficacy during repetitive rechallenge, giving rise to drug resistance, serial challenge with MP-MUS appears to have the opposite effect; MP-MUS treated cells upregulate mitochondrial levels, and in doing so further upregulate their levels of MAOB, making them sensitive to further MP-MUS treatment. We have recently shown the kinetics of rhMAO-A/-B acting on MP-MUS and known MAO substrates (Sharpe et al., 2015). MP-MUS is a very poor rhMAO-A substrate, but MP-MUS has a similar km and Vmax to benzylamine in rhMAOB. We also show that in vitro, MP-MUS is more toxic to primary GBM than to normal human astrocytes and that this difference in toxicity at least partly due to the higher levels of MAOB in glioma. It is possible that like MPP+, P+-MUS could be a dopamine transporter substrate and so can induce Parkinsonian syndromes due to DAT-mediated toxicity. We designed MP-MUS so that the active compound, P+-MUS, would be too large to serve as a DAT substrate, based on the known kinetics of MPP+ analogues. We observed no Parkinsonian symptoms in any of the MP-MUS treated animals, nor did an examination of treated brains reveal any toxicity toward the dopaminergic neurons. As human and mouse DAT share very similar sequence homology and substrate kinetics (Han and Gu, 2006) the inability of MP-MUS to target mouse dopaminergic neurons via DAT-mediated toxicity should be replicated in humans. Treatment of glioblastoma has been a challenge for decades. The Radiation Therapy Oncology Group (RTOG) study in 1993 demonstrated the limited value of surgery (Simpson et al., 1993). Patients who underwent radical surgery and radiotherapy vs. biopsy only and radiation therapy had an increase in survival from only 6.6 to 11.3months. The addition of radiation therapy and chemotherapy, including the use of temozolomide, has only extended median survival to 15months over 20years later. Furthermore, the final 3months of life generally have a low quality attached to them. Thus, a novel approach is desperately needed for these patients. The next steps for this construct is to perform detailed toxicological studies, pharmacodynamic testing, and to fine-tune the details of the manufacturing process. This work is under way, and we are hopeful to see this drug in clinical trials in the next 18months.
Author Contributions MAS did the labeling/imaging and worked with AL on the flank model and with TG on the TAPI-1 model of glioma. MAS and DSB were responsible for the design of MP-MUS. MAS did the in silico modeling and designed the initial synthetic route. PG did the original MP-MUS synthesis. JH improved the synthesis and purified and chemically characterized the MP-MUS used in our reported studies.
Conflicts of Interest
Acknowledgments
This work was funded by, the Donna and Kenneth R. Peak Foundation, the Taub Foundation, the Blanche Green Estate Fund of the Pauline Sterne Wolff Memorial Foundation, the Veralan Foundation, the Methodist Hospital Foundation, the John S. Dunn Foundation, the American Brain Tumor Association, and was made possible by the many patients and families who have been affected by the devastating effects of brain tumors and central nervous system disease.
Introduction Within the last decade, tenofovir (TFV), prescribed as tenofovir disoproxil fumarate in its prodrug formulation, has emerged as a critical component of antiretroviral combination therapy for the treatment of human immunodeficiency virus (HIV) (Schooley et al., 2002; Robbins et al., 1998). More recently, oral as well as vaginal and rectal microbicide gel preparations of TFV have been investigated for use in pre-exposure prophylaxis (PrEP) as an HIV prevention strategy for individuals at high-risk of viral exposure (Baeten et al., 2012; Mayer et al., 2006; Anton et al., 2012). TFV is a desirable drug candidate for PrEP due to the long half-life of active drug TFV-diphosphate (TFV-DP), reported to be 53h in vaginal tissue homogenate and up to 139h in vaginal CD4+ cells following an oral dosing of HIV-uninfected women (Derdelinckx et al., 2006; Louissaint et al., 2013). That being said, there has been discrepancy in the prophylactic effect observed for TFV-based regimens. For example, the Partners in Prevention study demonstrated a 67–75% reduction in HIV acquisition in serodiscordant heterosexual couples, iPrEx demonstrated a 44% reduction in men or transgender women who have sex with men, whereas FEM-PrEP and VOICE trials showed no significant reduction in the rate of infection in heterosexual women (Grant et al., 2010; Van Damme et al., 2012; Marrazzo et al., 2015). This disparity has been primarily due to poor adherence. Adjusting for adherence, the differences among these clinical trials have been attributed to the increased accumulation of active drug in colorectal versus vaginal tissue. As such, these findings suggest that the enzymes responsible for TFV activation may differ between colorectal and vaginal tissue, however, this has not been tested thus far. Further, while yet to be explored, it can be envisioned that genetic variation in the nucleotide kinases that activate TFV could underlie observed inter-individual differences in tissue TFV-DP concentrations that has been noted even when adherence is high (Louissaint et al., 2013; Hendrix et al., 2013; Patterson et al., 2011).