Ensayos de Terapia Génica en Enfermedad de Parkinson

Estos son los ensayos publicados recientemente sobre Terapia Génica en EP.
Han sido realizados en modelos animales, células en cultivo y en seres humanos (Fase I).


Neurology. 2008 May 20;70(21):1980-3. Epub 2008 Apr 9.
Results from a phase I safety trial of hAADC gene therapy for Parkinson disease.
Eberling JL, Jagust WJ, Christine CW, Starr P, Larson P, Bankiewicz KS, Aminoff MJ.
Department of Molecular Imaging and Neuroscience, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA. jleberling@lbl.gov
BACKGROUND: In a primate model of Parkinson disease (PD), intrastriatal infusion of an adeno-associated viral (AAV) vector containing the human aromatic l-amino acid decarboxylase (hAADC) gene results in robust gene expression. After gene transfer, low doses of systemically administered l-dopa are converted to dopamine in the transduced striatal neurons, resulting in behavioral improvement without the side effects typically associated with higher doses of l-dopa. These studies led to the initiation of a phase I safety trial. Here we report the findings for the first cohort of five patients. METHODS: Patients with moderate to advanced PD received bilateral infusion of a low dose of the AAV-hAADC vector into the putamen. PET scans using the AADC tracer, 6-[18F]fluoro-l-m-tyrosine (FMT), were performed at baseline and at 1 and 6 months after infusion as an in vivo measure of gene expression. RESULTS: PET results showed an average 30% increase in FMT uptake (K(i)(c)) in the putamen after gene transfer. Preliminary analysis of clinical data indicates a modest improvement, but absence of a control and the nonblinded analyses make interpretation difficult. CONCLUSIONS: Thus far, this gene therapy approach has been well tolerated and shows PET evidence of sustained gene expression. These initial findings demonstrate the safety of the therapy; higher doses of adeno-associated viral vector containing the human aromatic l-amino acid decarboxylase gene in the next cohort of patients may further increase dopamine production in the putamen and provide more profound clinical benefit.

Lancet. 2007 Jun 23;369(9579):2097-105.
Safety and tolerability of gene therapy with an adeno-associated virus (AAV) borne GAD gene for Parkinson's disease: an open label, phase I trial.
Kaplitt MG, Feigin A, Tang C, Fitzsimons HL, Mattis P, Lawlor PA, Bland RJ, Young D, Strybing K, Eidelberg D, During MJ.
Department of Neurological Surgery, Weill Medical College of Cornell University, New York, NY, USA.
BACKGROUND: Dopaminergic neuronal loss in Parkinson's disease leads to changes in the circuitry of the basal ganglia, such as decreased inhibitory GABAergic input to the subthalamic nucleus. We aimed to measure the safety, tolerability, and potential efficacy of transfer of glutamic acid decarboxylase (GAD) gene with adeno-associated virus (AAV) into the subthalamic nucleus of patients with Parkinson's disease. METHODS: We did an open label, safety and tolerability trial of unilateral subthalamic viral vector (AAV-GAD) injection in 11 men and 1 woman with Parkinson's disease (mean age 58.2, SD=5.7 years). Four patients received low-dose, four medium-dose, and four high-dose AAV-GAD at New York Presbyterian Hospital. Inclusion criteria consisted of Hoehn and Yahr stage 3 or greater, motor fluctuations with substantial off time, and age 70 years or less. Patients were assessed clinically both off and on medication at baseline and after 1, 3, 6, and 12 months at North Shore Hospital. Efficacy measures included the Unified Parkinson's Disease Rating Scale (UPDRS), scales of activities of daily living (ADL), neuropsychological testing, and PET imaging with 18F-fluorodeoxyglucose. The trial is registered with the ClinicalTrials.gov registry, number NCT00195143. FINDINGS: All patients who enrolled had surgery, and there were no dropouts or patients lost to follow-up. There were no adverse events related to gene therapy. Significant improvements in motor UPDRS scores (p=0.0015), predominantly on the side of the body that was contralateral to surgery, were seen 3 months after gene therapy and persisted up to 12 months. PET scans revealed a substantial reduction in thalamic metabolism that was restricted to the treated hemisphere, and a correlation between clinical motor scores and brain metabolism in the supplementary motor area. INTERPRETATION: AAV-GAD gene therapy of the subthalamic nucleus is safe and well tolerated by patients with advanced Parkinson's disease, suggesting that in-vivo gene therapy in the adult brain might be safe for various neurodegenerative diseases.

J Gene Med. 2007 Jul;9(7):605-12.
Comparison of cDNA and genomic forms of tyrosine hydroxylase gene therapy of the brain with Trojan horse liposomes.
Xia CF, Chu C, Li J, Wang Y, Zhang Y, Boado RJ, Pardridge WM.
Department of Medicine, UCLA, Los Angeles, CA 90024, USA.
BACKGROUND: The present study examines whether chromosomal derived forms of therapeutic genes can be delivered to brain following intravenous administration. The brain expression of a rat tyrosine hydroxylase (TH) cDNA is compared to the brain expression of a plasmid DNA encoding the 18 kb rat TH gene. METHODS: TH gene expression is measured in cell culture and in vivo in brain in experimental Parkinson's disease (PD). A total of four eukaryotic expression plasmids encoding rat TH were engineered wherein the size of the TH expression cassette ranged from 1.5 kb, in the case of the cDNA form of the gene, to 17.5 kb, in the case of the largest size genomic construct. The TH expression plasmids were delivered to either cultured cells or to rat brain in vivo with Trojan horse liposomes (THLs), which target the non-viral plasmid DNA to cells via cell membrane receptors. RESULTS: The pattern of TH gene expression in cell culture and in vivo was similar: the cDNA form of the TH gene was fast-acting with short duration of action, and the genomic form of the TH gene was slow-acting with longer duration of action. The most sustained replacement of striatal TH enzyme activity in experimental PD was produced by combination gene therapy where both the cDNA and the genomic forms of the TH gene were administered simultaneously. CONCLUSIONS: Eukaryotic expression plasmids encoding genomic forms of therapeutic genes, as large as 18 kb, can be successfully incorporated in THLs and delivered to brain following intravenous administration.

Gene Ther. 2006 Dec;13(23):1639-44.
Koike H, Ishida A, Shimamura M, Mizuno S, Nakamura T, Ogihara T et al, Prevention of onset of Parkinson's disease by in vivo gene transfer of human hepatocyte growth factor in rodent model: a model of gene therapy for Parkinson's disease.
Division of Clinical Gene Therapy, Graduate School of Medicine, Osaka University, 2-2 Yamada-oka, Suita, Osaka 565-0871, Japan.
Parkinson's disease (PD) is a neurodegenerative disorder characterized by the loss of dopaminergic neurons in the substantia nigra (SNi). As neurotrophic factors support the survival and enhance the function of dopaminergic neurons, gene therapy using neurotrophic factors has become the center of interest. Thus, we focused on hepatocyte growth factor (HGF) as a neurotrophic and angiogenic growth factor. At 7 days before injection of 6-hydroxydopamine into the SNi, stereotaxic transfection of human HGF or lacZ plasmid was performed into the unilateral striatum of rats. Expression of human HGF in the injected sites could be detected in rats transfected with HGF plasmid DNA, using immunohistochemical staining. Consistently, human immunoreactive HGF protein could be detected at least up to 12 days after transfection. Interestingly, PD rats transfected with lacZ demonstrated amphetamine-induced rotational asymmetry. However, transfection of HGF plasmid DNA resulted in significant inhibition of abnormal rotation up to 24 weeks in a dose-dependent manner. Over 90% of dopaminergic neurons were lost in PD rats transfected with lacZ, whereas over 70% survived in rats transfected with HGF, as assessed by immunohistochemical staining. Overall, the present study demonstrated that overexpression of HGF prevented neuronal death in a PD rat model, providing a potential novel therapy for PD.

Riesgos familiares en Enfermedad de Parkinson

Mov Disord. 2008 Jun 15;23(8):1174-83.
Familial aggregation of Parkinson's disease: a meta-analysis.
Thacker EL, Ascherio A.
Department of Nutrition, Harvard School of Public Health, Boston, Massachusetts, USA. ethacker@post.harvard.edu

We sought to determine the relative risk (RR) of Parkinson's disease (PD) for having a first-degree relative with PD versus having no first-degree relative with PD. Studies of familial aggregation of PD were identified by searching Medline and other sources. From each study, RRs were extracted or calculated based on the published data. Studies were categorized according to methodological characteristics, as well as by first-degree relationship type and age at PD onset restrictions. Meta-analyses and meta-regressions were based on random effect models. Twenty-nine studies of familial aggregation of PD were identified with results for first-degree relatives. The best estimate of the RR of PD for having a first-degree relative with PD was 2.9 (95% CI: 2.2, 3.8; P = 2.2 E-14), based on the studies with the most rigorous methods. The RR for sibling pairs was 4.4 (95% CI: 3.1, 6.1; P < 1.0 E-30), while for child-parent pairs it was 2.7 (95% CI: 2.0, 3.7; P = 3.6 E-10). The RR for early onset PD was 4.7 (95% CI: 3.2, 6.8; P = 6.7 E-16), while for late onset PD it was 2.7 (95% CI: 1.9, 3.9; P = 1.8 E-8). Inclusion of methodologically less rigorous investigations tended to increase the RR estimates. Summary RRs were clearly elevated above one for all study methods, all first-degree relationship types, and all age at onset categories. Familial aggregation of PD is strong and unlikely to be due to chance or to deficiencies in study methodology.

(c) 2008 Movement Disorder Society

Asesoramiento Genético en Enfermedad de Parkinson

La Enfermedad de Parkinson (EP) es una patología neurodegenerativa compleja y multifactorial en su etiopatogenia. Si bien se consideró en un principio como improbable una base genética en la misma, trabajos de la última década han implicado a varios genes en su patogénesis, han identificado varias formas monogénicas de EP y han evidenciado un significativo componente hereditario, al menos en un subgrupo de pacientes (y familias).

Si bien la mayoría de los casos de Enfermedad de Parkinson (EP) son de presentación esporádica (no hay otros afectados en la familia) y empiezan luego de los 60 años, en algunos casos (o algunas familias) aparecen varios individuos afectados y/o la EP se inicia en la juventud. En los casos de inicio en la juventud y/o con antecedentes familiares el rol de los genes es probablemente más significativo. Estos casos son aproximadamente un 10% de los casos de EP. De todos modos, los genes influencian la aparición de EP aún en los casos sin antecedentes familiares y de inicio más tardío.

Como los genes influencian el riesgo de EP y los genes se transmiten de padres a hijos y se comparten entre hermanos, entonces los familiares de pacientes con EP tienen un riesgo aumentado de padecer la EP. Los familiares de primer grado (hijos, padres y hermanos) de pacientes con EP tienen al menos el triple de riesgo (a lo largo de su vida) de sufrir EP que otras personas. Este riesgo de recurrencia depende sobre todo de la edad de inicio de la enfermedad, aproximadamente:

–Antes de los 45 años: el riesgo para familiares de primer grado es 1/12

–Entre los 45 y 55 años: el riesgo para familiares de primer grado es 1/20

–Luego de los 65 años: el riesgo para familiares de primer grado es 1/50

Estos riesgos son promedios, por lo que en algunas famlias este riesgo puede ser tan alto como un 50% (herencia autosómica dominante) o tan bajos como 2-3% (formas multifactoriales). En la mayoría de los casos el riesgo es intermedio a estos valores y menor al 10%.

El asesoramiento genético permite analizar a cada familia en particular y calcular (al menos aproximadamente) estos riesgo para cada familia (o individuo) y discutirlos con los interesados. Los datos de presentación clínica de la afección, los datos obtenidos de la realización sistematizada de la historia familiar y los datos empíricos sore recurrencia de la afección, permiten una estimación aproximada de estos riesgos (que son, en general, significativos, solamente para los familaires de primer grado, fundamentalmente hijos y hermanos).

Adicionalmente, y en casos seleccionados, se puede recurrir a análisis de genética molecular, sobre genes (o mutaciones) específicos, que aportan datos más precisos de riesgo, pero muchas veces difíciles de interpretar. Este tipo de estudios se denominan de “Genética predictiva”, en el sentido de que conociendo el genotipo del individuo (para determinadas variantes genéticas) se puede predecir (al menos parcialmente) el fenotipo (en este caso, el riesgo de determinada enfermedad) para afecciones de inicio tardía y con un extenso período presintomático (como la EP). En estos casos las implicancias del test, las cuestiones psicoemocionales que lo acompañan, y la dificil interpretación de los resultados, obligan a un cuidadoso proceso de asesoramiento genético pre y postest.

El asesoramiento genético tradicional era esencialmente reproductivo y no tenía como objetivo primario la prevención de patologías genéticas, sino mejorar la calidad de vida de las personas o parejas que sufrían por la posibilidad de aparición de estas afecciones en su descendencia, brindándoles la posibilidad de tomar decisiones reproductivas basándose en una información fidedigna. En los últimos años, ha surgido un moderno asesoramiento genético orientado específicamente a la prevención primaria o secundaria de diversas afecciones como el cáncer u otras afecciones frecuentes vinculadas al envejecimiento. En las últimas dos décadas, al impulso del Proyecto Genoma Humano y desarrollos asociados, ha ocurrido un cambio de modelo en la Genética Médica que ha pasado de ocuparse exclusivamente de las “enfermedades genéticas” a la “genética de las enfermedades”. La moderna medicina genómica se ocupa de la interacción entre el genoma de los individuos y su ambiente en la determinación de las enfermedades, generando herramientas aplicables al diagnóstico, tratamiento, pronóstico y diseño de estrategias y programas preventivos. El amplio espectro de la medicina genómica incluye un gran número de enfermedades; entre ellas, las enfermedades cardiovasculares, la diabetes, la hipertensión, las dislipemias, la osteoporosis, la obesidad, el asma, el cáncer, las enfermedades neurodegenerativas y las enfermedades gastrointestinales, que incluyen buena parte de las patologías crónicas frecuentes y prevenibles. Entonces, el objetivo central de la medicina genómica es el asesoramiento genético individualizado para prevenir la enfermedad o la mortalidad prematura en individuos genéticamente susceptibles. En este marco, los datos fundamentales se derivan del análisis de la historia familiar y del uso de diagnósticos moleculares específicos, y éstos aportan datos relevantes para identificar individuos susceptibles, para ayudar en el diagnóstico, para seleccionar el tratamiento más adecuado y para elaborar pronósticos.

La Genética Médica (como especialidad de la Medicina) aporta una serie de herramientas que pueden ser útiles en la atención de los pacientes y familias con EP. Es altamente probable que en el futuro inmediato estas herramientas de diagnóstico, tratamiento y prevención, aumenten y se desarrollen nuevas, ya que se realiza un intensa investigación en temas vinculados a la genética de la EP.