Development and Clinical Application of Gene and Cell therapies for Patients with Immune Deficiencies

National Institute Of Allergy And Infectious Diseases

Investigators

Linked publications & trials

Abstract

Our mission is to develop novel gene and cell therapies for primary immunodeficiency diseases (PID). This program has a long history with the development and implementation of hematopoietic stem & progenitor cell (HSPC) gene therapy for treatment of patients with PID. Currently we have active clinical trials using lentivector to treat Chronic Granulomatous Disease (CGD) and X-linked Severe Combined Immunodeficiency (X-SCID), a mRNA-transfection of autologous granulocytes for X-linked CGD cell therapy, as well as gene therapy for X-CGD using autologous stem cells with mutation repaired by base editing. In addition, we have applied base-editing approach to other PIDs and has initiated base editing of autologous HSPCs for treatment of X-SCID as well as CD40L Hyper IgM syndrome. Our lentivector gene therapy clinical trial (IND 15041, NIAID IRB approved 11-I-0007) is aimed at treatment of older patients (aged 2 to 40 years) with X-SCID. The objectives of this study are to establish safety and efficacy of lentivector transduced autologous HSPCs in improving immunity and ameliorate clinical problems. To address problems related to low transduction efficiencies and need for large amounts of clinical vector for older/larger patients, we have incorporated the use of LentiBoost and prostaglandin (PEG2) during transduction. Including patients treated with cells transduced using the enhanced transduction conditions, we treated a total of nineteen subjects. Our surveillance of the vector insert sites in peripheral blood cells of treated subjects uncovered cryptic splice acceptors within the vector that has led to aberrant fusion transcripts of vector and insert gene, which led to expansion of HMGA2+ clones. The clonal expansion is observed in molecular studies in most patients but has not led to any clinical or laboratory abnormalities. We modified the vector to remove two cryptic splice sites in the vector. This new modified vector was used to treat one patient recently without problems to date. Long-term follow up is necessary to establish the efficacy and safety of the LV-transduced HSCs This experience has revealed advantages and shortcomings of these approaches and allow us to develop improvement to the cell manufacture procedures and treatment of patients to overcome problems such as low transduction efficiencies and development of autoimmune problems following cell infusion To address concerns regarding potential insertional oncogenesis and the lack of endogenous regulation of genes inserted using integrating vectors, we recently evaluated the CRISPR/Cas system to attempt more specific genetic modifications in hematopoietic stem cells. The CRISPR-Cas9 nuclease approach relies on delivery of a double strand DNA-break (DSB) at a specific target genetic site (guided by single guide RNA), followed by homology-directed repair to convert to the desired DNA sequence. The donor template can be a short oligonucleotide for a mutation repair, or insertion of a entire gene delivered by a engineered virus such as adeno-associated virus. To improve the efficiency of the desired homology-directed repair and to abrogate DNA damage response following exposure to AAV, we evaluated the addition of editing enhancers (i53 and GSE) to augment the efficacy of targeted insertion and cell viability with genome editing using CRISPR/Cas9. Although highly efficient correction levels can be achieved, additional safety studies to assess the consequences of nuclease-induced double strand DNA breaks and relatively inefficient HDR are necessary before these approaches can be translated to treatment of patients in clinical trials. More recently, we have applied base editing and PRIME editing approaches to functionally correct mutations that result in some PIDs. This is an exciting development due to its improved safety profile from the lack of double strand DNA breaks and likely increased specificity. We conducted extensive preclinical studies to demonstrate efficacy and safety of base-edited HSPCs from a few mutations that cause PID such as CGD, X-SCID, WHIM, XLA and XMEN. Data from the preclinical studies supported an approved IND for treatment of CGD patients (with select CYBB mutations) using base-edited HSPCs (IND 28925, NCT06325709). The same approach to repair mutations is also used for treatment of X-SCID (NCT06851767) and CD40L HIGM (NCT06959771).