Preclinical evaluation of investigational radiopharmaceutical RISAD-P intended for use as a diagnostic and molecular radiotherapy agent for prostate cancer.

BACKGROUND: The androgen receptor (AR) plays a dominant role in the pathogenesis of prostate cancer. 5-Radioiodo-3'-O-(17ß-succinyl-5α-androstan-3-one)-2'-deoxyuridin-5'-yl phosphate (RISAD-P) is an AR-targeting reagent developed for noninvasive assessment of AR and proliferative status of the AR-expressing tumors, and for molecular radiotherapy with Auger electron-emitting radionuclides. In this study, the preclinical toxicity and targeting potential of RISAD-P was evaluated. METHODS: Effects of nonradioactive ISAD-P and RISAD-P labeled with (123) I, (124) I, and (125) I were evaluated in male mice. Expanded-acute single dose toxicity studies, hematologic toxicity, liver and kidney function, pharmacokinetics, biodistribution, and imaging studies were conducted. Imaging and pilot therapy studies were conducted in transgenic mice. RESULTS: RISAD-P is not toxic at doses projected for clinical use. Its tissue distribution compares favorably with the distribution reported for (18) F-dihydrotestosterone derivatives. RISAD-P has excellent prostate cancer targeting properties. One hour after (125) IRISAD-P administration, nearly 10% of the injected dose is associated with prostate tumor. The tumor clearance is biphasic and plateaus between 24 and 48 hr post-injection. The estimated radiation doses calculated for 1 g tumor using the MIRD convention are well within the therapeutic range with values of 170, 250, 1,240 Gy × MBq(-1) × g(-1) for (125) I-, (123) I-, and (124) I-labeled RISAD-P, respectively. The transient uptake of radioactivity is observed in the genitourinary tract and stomach. Without the potassium iodide blockade, thyroid uptake is also observed. CONCLUSIONS: Biodistribution, toxicity, and radiation dosimetry studies suggest that RISAD-P holds characteristics of a promising candidate for imaging of AR expression and tumor proliferation, as well as molecular radiotherapy for metastatic or locally, regionally advanced prostate cancer.

Neuromagnetic evidence of abnormal movement-related beta desynchronization in Parkinson's disease.

Parkinson's disease (PD) is a neurodegenerative disorder associated with debilitating motor, posture, and gait abnormalities. Human studies recording local field potentials within the subthalamic nucleus and scalp-based electroencephalography have shown pathological beta synchronization throughout the cortical-basal ganglia motor network in PD. Suppression of such pathological beta synchronization has been associated with improved motor function, which may explain the effectiveness of deep-brain stimulation. We used magnetoencephalography (MEG) to investigate neural population-level beta responses, and other oscillatory activity, during a motor task in unmedicated patients with PD and a matched group of healthy adults. MEG is a noninvasive neurophysiological technique that permits the recording of oscillatory activity during movement planning, execution, and termination phases. Each of these phases was independently examined using beamforming to distinguish the brain areas and movement phases, where pathological oscillations exist during motor control. Patients with PD exhibited significantly diminished beta desynchronization compared with controls prior to and during movement, which paralleled reduced alpha desynchronization. This study is the first to systematically investigate neural oscillatory responses in PD during distinct stages of motor control (e.g. planning, execution, and termination) and indicates that these patients have significant difficulty suppressing cortical beta synchronization during movement planning, which may contribute to their diminished movement capacities.

Actin interaction and regulation of cyclin-dependent kinase 5/p35 complex activity.

Cyclin-dependent kinase 5 (Cdk5) plays a critical role during neurodevelopment, synaptic plasticity, and neurodegeneration. Cdk5 activity depends on association with neuronal proteins p35 and p25, a proteolytic product of p35. Cdk5 regulates the actin cytoskeletal dynamics that are essential for neuronal migration, neuritic growth, and synaptogenesis. However, little is known about the interaction of actin and Cdk5 and its effect on neuronal Cdk5 activity. In a previous study, we observed that Cdk5/p35 activity is negatively correlated with co-immunoprecipitated F-actin (filamentous actin) amounts in the mouse brain, and suggested that F-actin inhibits the formation of the Cdk5/p35 complex [Journal of Neuroscience (2008) vol. 28, p. 14511]. The experiments reported here were undertaken to elucidate the relationship between actin and the formation of the Cdk5/p35 complex and its activity. Instead of an F-actin-mediated inhibition, we propose that G-actin (globular actin) in the F-actin preparations is responsible for inhibiting Cdk5/p35 and Cdk5/p25 kinase activity. We found that F-actin binds to p35 but not p25 or Cdk5. We have shown that G-actin binds directly to Cdk5 without disrupting the formation of the Cdk5/p35 or Cdk5/p25 complexes. G-actin potently suppressed Cdk5/p35 and Cdk5/p25 activity when either histone H1 or purified human tau protein were used as substrates, indicating a substrate-independent inhibitory effect of G-actin on Cdk5 activity. Finally, G-actin suppressed the activity of Cdk5 immunoprecipitated from wild type and p35-deficient mouse brain, suggesting that G-actin suppresses endogenous Cdk5 activity in a p35-independent manner. Together, these results suggest a novel mechanism of actin cytoskeletal regulation of Cdk5/p35 activity.

Evaluation of the safety and immunomodulatory effects of sargramostim in a randomized, double-blind phase 1 clinical Parkinson's disease trial.

A potential therapeutic role for immune transformation in Parkinson's disease evolves from more than a decade of animal investigations demonstrating regulatory T cell (Treg) nigrostriatal neuroprotection. To bridge these results to human disease, we conducted a randomized, placebo-controlled double-blind phase 1 trial with a well-studied immune modulator, sargramostim (granulocyte-macrophage colony-stimulating factor). We enrolled 17 age-matched non-Parkinsonian subjects as non-treated controls and 20 Parkinson's disease patients. Both Parkinson's disease patients and controls were monitored for 2 months for baseline profiling. Parkinson's disease patients were then randomized into two equal groups to self-administer placebo (saline) or sargramostim subcutaneously at 6 µg/kg/day for 56 days. Adverse events for the sargramostim and placebo groups were 100% (10/10) and 80% (8/10), respectively. These included injection site reactions, increased total white cell counts, and upper extremity bone pain. One urticarial and one vasculitis reaction were found to be drug and benzyl alcohol related, respectively. An additional patient with a history of cerebrovascular disease suffered a stroke on study. Unified Parkinson's disease rating scale, Part III scores in the sargramostim group showed modest improvement after 6 and 8 weeks of treatment when compared with placebo. This paralleled improved magnetoencephalography-recorded cortical motor activities and Treg numbers and function compared with pretreated Parkinson's disease patients and non-Parkinsonian controls. Peripheral Treg transformation was linked to serum tryptophan metabolites, including L-kynurenine, quinolinic acid, and serotonin. These data offer a potential paradigm shift in modulating immune responses for potential therapeutic gain for Parkinson's disease. Confirmation of these early study results requires larger numbers of enrolled patients and further clinical investigation.

Dual destructive and protective roles of adaptive immunity in neurodegenerative disorders.

Inappropriate T cell responses in the central nervous system (CNS) affect the pathogenesis of a broad range of neuroinflammatory and neurodegenerative disorders that include, but are not limited to, multiple sclerosis, amyotrophic lateral sclerosis, Alzheimer's disease and Parkinson's disease. On the one hand immune responses can exacerbate neurotoxic responses; while on the other hand, they can lead to neuroprotective outcomes. The temporal and spatial mechanisms by which these immune responses occur and are regulated in the setting of active disease have gained significant recent attention. Spatially, immune responses that affect neurodegeneration may occur within or outside the CNS. Migration of antigen-specific CD4+ T cells from the periphery to the CNS and consequent immune cell interactions with resident glial cells affect neuroinflammation and neuronal survival. The destructive or protective mechanisms of these interactions are linked to the relative numerical and functional dominance of effector or regulatory T cells. Temporally, immune responses at disease onset or during progression may exhibit a differential balance of immune responses in the periphery and within the CNS. Immune responses with predominate T cell subtypes may differentially manifest migratory, regulatory and effector functions when triggered by endogenous misfolded and aggregated proteins and cell-specific stimuli. The final result is altered glial and neuronal behaviors that influence the disease course. Thus, discovery of neurodestructive and neuroprotective immune mechanisms will permit potential new therapeutic pathways that affect neuronal survival and slow disease progression.

CD4+ regulatory and effector/memory T cell subsets profile motor dysfunction in Parkinson's disease.

Animal models and clinical studies have linked the innate and adaptive immune system to the pathology of Parkinson's disease (PD). Despite such progress, the specific immune responses that influence disease progression have eluded investigators. Herein, we assessed relationships between T cell phenotype and function with PD progression. Peripheral blood lymphocytes from two separate cohorts, a discovery cohort and a validation cohort, totaling 113 PD patients and 96 age- and environment-matched caregivers were examined by flow cytometric analysis and T cell proliferation assays. Increased effector/memory T cells (Tem), defined as CD45RO+ and FAS+ CD4+ T cells and decreased CD31+ and α4ß7+ CD4+ T cells were associated with progressive Unified Parkinson's Disease Rating Scale III scores. However, no associations were seen between immune biomarkers and increased age or disease duration. Impaired abilities of regulatory T cells (Treg) from PD patients to suppress effector T cell function was observed. These data support the concept that chronic immune stimulation, notably Tem activation and Treg dysfunction is linked to PD pathobiology and disease severity, but not disease duration. The association of T cell phenotypes with motor symptoms provides fresh avenues for novel biomarkers and therapeutic designs.