Gene therapy in rare diseases: the benefits and challenges of developing a patient-centric registry for Strimvelis in ADA-SCID.

BACKGROUND: Strimvelis (autologous CD34+ cells transduced to express adenosine deaminase [ADA]) is the first ex vivo stem cell gene therapy approved by the European Medicines Agency (EMA), indicated as a single treatment for patients with ADA-severe combined immunodeficiency (ADA-SCID) who lack a suitable matched related bone marrow donor. Existing primary immunodeficiency registries are tailored to transplantation outcomes and do not capture the breadth of safety and efficacy endpoints required by the EMA for the long-term monitoring of gene therapies. Furthermore, for extended monitoring of Strimvelis, the young age of children treated, small patient numbers, and broad geographic distribution of patients all increase the risk of loss to follow-up before sufficient data have been collected. Establishing individual investigator sites would be impractical and uneconomical owing to the small number of patients from each location receiving Strimvelis. RESULTS: An observational registry has been established to monitor the safety and effectiveness of Strimvelis in up to 50 patients over a minimum of 15 years. To address the potential challenges highlighted above, data will be collected by a single investigator site at Ospedale San Raffaele (OSR), Milan, Italy, and entered into the registry via a central electronic platform. Patients/families and the patient's local physician will also be able to submit healthcare information directly to the registry using a uniquely designed electronic platform. Data entry will be monitored by a Gene Therapy Registry Centre (funded by GlaxoSmithKline) who will ensure that necessary information is collected and flows between OSR, the patient/family and the patient's local healthcare provider. CONCLUSION: The Strimvelis registry sets a precedent for the safety monitoring of future gene therapies. A unique, patient-focused design has been implemented to address the challenges of long-term follow-up of patients treated with gene therapy for a rare disease. Strategies to ensure data completeness and patient retention in the registry will help fulfil pharmacovigilance requirements. Collaboration with partners is being sought to expand from a treatment registry into a disease registry. Using practical and cost-efficient approaches, the Strimvelis registry is hoped to encourage further innovation in registry design within orphan drug development.

Gene Therapy for Adenosine Deaminase Deficiency: A Comprehensive Evaluation of Short- and Medium-Term Safety.

Loss of adenosine deaminase activity leads to severe combined immunodeficiency (ADA-SCID); production and function of T, B, and natural killer (NK) cells are impaired. Gene therapy (GT) with an autologous CD34+-enriched cell fraction that contains CD34+ cells transduced with a retroviral vector encoding the human ADA cDNA sequence leads to immune reconstitution in most patients. Here, we report short- and medium-term safety analyses from 18 patients enrolled as part of single-arm, open-label studies or compassionate use programs. Survival was 100% with a median of 6.9 years follow-up (range, 2.3 to 13.4 years). Adverse events were mostly grade 1 or grade 2 and were reported by all 18 patients following GT. Thirty-nine serious adverse events (SAEs) were reported by 15 of 18 patients; no SAEs were considered related to GT. The most common adverse events reported post-GT include upper respiratory tract infection, gastroenteritis, rhinitis, bronchitis, oral candidiasis, cough, neutropenia, diarrhea, and pyrexia. Incidence rates for all of these events were highest during pre-treatment, treatment, and/or 3-month follow-up and then declined over medium-term follow-up. GT did not impact the incidence of neurologic/hearing impairments. No event indicative of leukemic transformation was reported.

Good Laboratory Practice Preclinical Safety Studies for GSK2696273 (MLV Vector-Based Ex Vivo Gene Therapy for Adenosine Deaminase Deficiency Severe Combined Immunodeficiency) in NSG Mice.

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.

Update on the safety and efficacy of retroviral gene therapy for immunodeficiency due to adenosine deaminase deficiency.

Adenosine deaminase (ADA) deficiency is a rare, autosomal-recessive systemic metabolic disease characterized by severe combined immunodeficiency (SCID). The treatment of choice for ADA-deficient SCID (ADA-SCID) is hematopoietic stem cell transplant from an HLA-matched sibling donor, although <25% of patients have such a donor available. Enzyme replacement therapy (ERT) partially and temporarily relieves immunodeficiency. We investigated the medium-term outcome of gene therapy (GT) in 18 patients with ADA-SCID for whom an HLA-identical family donor was not available; most were not responding well to ERT. Patients were treated with an autologous CD34(+)-enriched cell fraction that contained CD34(+) cells transduced with a retroviral vector encoding the human ADA complementary DNA sequence (GSK2696273) as part of single-arm, open-label studies or compassionate use programs. Overall survival was 100% over 2.3 to 13.4 years (median, 6.9 years). Gene-modified cells were stably present in multiple lineages throughout follow up. GT resulted in a sustained reduction in the severe infection rate from 1.17 events per person-year to 0.17 events per person-year (n = 17, patient 1 data not available). Immune reconstitution was demonstrated by normalization of T-cell subsets (CD3(+), CD4(+), and CD8(+)), evidence of thymopoiesis, and sustained T-cell proliferative capacity. B-cell function was evidenced by immunoglobulin production, decreased intravenous immunoglobulin use, and antibody response after vaccination. All 18 patients reported infections as adverse events; infections of respiratory and gastrointestinal tracts were reported most frequently. No events indicative of leukemic transformation were reported. Trial details were registered at www.clinicaltrials.gov as #NCT00598481.

The effects of the TRPV1 antagonist SB-705498 on TRPV1 receptor-mediated activity and inflammatory hyperalgesia in humans.

TRPV1 is a cation channel activated by a range of noxious stimuli and highly expressed in nociceptive fibres. TRPV1 receptors are involved in pain and sensitisation associated with tissue injury and inflammation; hence, TRPV1 antagonists are potentially useful for the treatment of such pain states. SB-705498 is a potent, selective and orally bioavailable TRPV1 antagonist with demonstrated efficacy in a number of preclinical pain models. In this first-time-into-human study, we have investigated the pharmacodynamic and antihyperalgesic activity of SB-705498. The compound was safe and well tolerated at single oral doses up to 400mg. In a cohort of 19 healthy volunteers, we used a randomised placebo-controlled single-blind cross-over design to assess the effects of SB-705498 (400mg) on heat-evoked pain and skin sensitisation induced by capsaicin or UVB irradiation. Compared with placebo, SB-705498 reduced the area of capsaicin-evoked flare (P=0.0047). The heat pain threshold on non-sensitised skin was elevated following SB-705498 (estimated difference from placebo [95% confidence intervals]: 1.3 degrees C [0.07,2.53], P=0.019). Following capsaicin sensitisation, the heat pain threshold and tolerance were similar between SB-705498 and placebo. However, SB-705498 increased heat pain tolerance at the site of UVB-evoked inflammation (estimated difference from placebo: 0.93 degrees C [0.25,1.6], P=0.0054). The magnitude of the pharmacodynamic effects of SB-705498 appeared to be related to plasma concentration. These results indicate that SB-705498, at a clinically safe and well-tolerated dose, has target-specific pharmacodynamic activity in humans. These data provide the first clinical evidence that a TRPV1 antagonist may alleviate pain and hyperalgesia associated with inflammation and tissue injury.