Human Gene Therapy Clinical Development最新文献

The homozygous form of familial hypercholesterolemia (HoFH) is an excellent model for developing in vivo gene therapy in humans. The success of orthotropic liver transplantation in correcting the metabolic abnormalities in HoFH suggests that the correction of low-density lipoprotein receptor (LDLR) expression in hepatocytes via gene therapy should be sufficient for therapeutic efficacy. Vectors based on adeno-associated virus serotype 8 (AAV8) have been previously developed for liver-targeted gene therapy of a number of genetic diseases, including HoFH. In preparation for initiating a Phase 1 clinical trial of AAV8-mediated LDLR gene therapy for HoFH, a combined pharmacology/toxicology study was conducted in a mouse model of HoFH. No dose-limiting toxicities were found at or below 6.0 × 10¹³ GC/kg. Therefore, the maximally tolerated dose is greater than the highest dose that was tested. Mild and transient liver pathology was noted at the highest dose. Therefore, the no effect dose was greater than or equal to the middle dose of 7.5 × 10¹² GC/kg. The minimally effective dose was determined to be ≤7.5 × 10¹¹ GC/kg, based on stable reductions in cholesterol that were considered to be clinically significant. This translates to a therapeutic window of ≥80-fold for the treatment of HoFH.

Vectors based on adeno-associated virus serotype 8 (AAV8) have been evaluated in several clinical trials of gene therapy for hemophilia B with encouraging results. In preparation for a Phase 1 clinical trial of AAV8 gene therapy for the treatment of homozygous familial hypercholesterolemia (HoFH), the safety of the clinical candidate vector, AAV8.TBG.hLDLR, was evaluated in wild-type rhesus macaques and macaques heterozygous for a nonsense mutation in the low-density lipoprotein receptor (LDLR) gene (LDLR^+/-). Intravenous infusion of 1.25 × 10¹³ GC/kg of AAV8.TBG.hLDLR expressing the human version of LDLR was well tolerated and associated with only mild histopathology that was restricted to the liver and sporadic, low-level, and transient elevations in transaminases. Some animals developed T cells to both capsid and the hLDLR transgene, although these adaptive immune responses were most evident at the early time points from peripheral blood and in mononuclear cells derived from the liver. This toxicology study supports the safety of AAV8.TBG.hLDLR for evaluation in HoFH patients, and provides some context for evaluating previously conducted clinical trials of AAV8 in patients with hemophilia.

GSK2696273 (autologous CD34+ cells transduced with retroviral vector that encodes for the human adenosine deaminase [ADA] enzyme) is a gamma-retroviral ex vivo gene therapy of bone marrow-derived CD34+ cells for the treatment of adenosine deaminase deficiency severe combined immunodeficiency (ADA-SCID). ADA-SCID is a severe monogenic disease characterized by immunologic and nonimmunologic symptoms. Bone-marrow transplant from a matched related donor is the treatment of choice, but it is available for only a small proportion of patients. Ex vivo gene therapy of patient bone-marrow CD34+ cells is an alternative treatment. In order to prepare for a marketing authorization application in the European Union, preclinical safety studies in mice were requested by the European Medicines Agency (EMA). A pilot study and a main biodistribution study were performed according to Good Laboratory Practice (GLP) at the San Raffaele Telethon Institute for Gene Therapy test facility. In the main study, human umbilical cord blood (UCB)-derived CD34+ cells were transduced with gamma-retroviral vector used in the production of GSK2696273. Groups of 10 male and 10 female NOD-SCID gamma (NSG) mice were injected intravenously with a single dose of transduced- or mock-transduced UCB CD34+ cells, and they were observed for 4 months. Engraftment and multilineage differentiation of blood cells was observed in the majority of animals in both groups. There was no significant difference in the level of chimerism between the two groups. In the gene therapy group, vector was detectable in lymphohemopoietic and nonlymphohemopoietic tissues, consistent with the presence of gene-modified human hematopoietic donor cells. Given the absence of relevant safety concerns in the data, the nonclinical studies and the clinical experience with GSK2696273 supported a successful application for market authorization in the European Union for the treatment of ADA-SCID patients, for whom no suitable human leukocyte antigen-matched related donor is available.

The modified Edmonston vaccine strain of measles virus (MV) has shown potent oncolytic efficacy against various tumor types and is being investigated in clinical trials. Our laboratory showed that MV effectively kills medulloblastoma tumor cells in both localized disease and when tumor cells are disseminated through cerebrospinal fluid (CSF). Although the safety of repeated intracerebral injection of modified MV in rhesus macaques has been established, the safety of administering MV into CSF has not been adequately investigated. In this study, we assessed the safety of MV-NIS (MV modified to express the human sodium iodide symporter protein) injected into the CSF of measles-immunized and measles virus-susceptible transgenic (CD46, IFNαRko) mice. Treated animals were administered a single intraventricular injection of 1 × 10⁵ or 1 × 10⁶ TCID₅₀ (50% tissue culture infective dose) of MV-NIS. Detailed clinical observation was performed over a 90-day period. Clinically, we did not observe any measles-related toxic effects or behavioral abnormality in animals of any treated cohort. The complete blood count and blood chemistry analysis results were found to be within normal range for all the cohorts. Histologic examination of brains and spinal cords revealed inflammatory changes, mostly related to the needle track; these resolved by day 21 postinjection. To assess viral biodistribution, quantitative RT-PCR to detect the measles virus N-protein was performed on blood and brain samples. Viral RNA was not detectable in the blood as soon as 2 days after injection, and virus cleared from the brain by 45 days postadministration in all treatment cohorts. In conclusion, our data suggest that a single injection of modified MV into the CSF is safe and can be used in future therapeutic applications.