β-thalassemia is a disorder caused by altered hemoglobin protein synthesis and affects individuals worldwide. Severe forms of the disease, left untreated, can result in death before the age of 3 years (1). The standard of care consists of chronic and costly palliative treatment by blood transfusion combined with iron chelation. This dual approach suppresses anemia and reduces iron-related toxicities in patients. Allogeneic bone marrow transplant is an option, but limited by the availability of a highly compatible HSC donor. While gene therapy is been explored in several trials, its use is highly limited to developed regions with centers of excellence and well-established healthcare systems (2). Hence, there remains a tremendous unmet medical need to develop alternative treatment strategies for β-thalassemia (3). Occurrence of aberrant splicing is one of the processes that affects β-globin synthesis in β-thalassemia. The (C>G) IVS-2-745 is a splicing mutation within intron 2 of the β-globin gene. It leads to an aberrantly spliced mRNA that incorporates an intron fragment. This results in an in-frame premature termination codon that inhibits β-globin production. Here, we propose the use of uniform 2'-O-methoxyethyl (2'-MOE) splice switching oligos (SSOs) to reverse this aberrant splicing in the pre-mRNA. With these lead SSOs we show aberrant to wild type splice switching. This switching leads to an increase of adult hemoglobin (HbA) up to 80% in erythroid cells from patients with the IVS-2-745 mutation. Furthermore, we demonstrate a restoration of the balance between β-like- and α-globin chains, and up to an 87% reduction in toxic α-heme aggregates. While examining the potential benefit of 2'-MOE-SSOs in a mixed sickle-thalassemic phenotypic setting, we found reduced HbS synthesis and sickle cell formation due to HbA induction. In summary, 2'-MOE-SSOs are a promising therapy for forms of β-thalassemia caused by mutations leading to aberrant splicing.

Monoclonal antibodies are one of the fastest growing classes of pharmaceutical products, however, their potential is limited by the high cost of development and manufacturing. Here we present a safe and cost-effective platform for in vivo expression of therapeutic antibodies using nucleoside-modified mRNA. To demonstrate feasibility and protective efficacy, nucleoside-modified mRNAs encoding the light and heavy chains of the broadly neutralizing anti-HIV-1 antibody VRC01 are generated and encapsulated into lipid nanoparticles. Systemic administration of 1.4 mg kg-1 of mRNA into mice results in ∼170 μg ml-1 VRC01 antibody concentrations in the plasma 24 h post injection. Weekly injections of 1 mg kg-1 of mRNA into immunodeficient mice maintain trough VRC01 levels above 40 μg ml-1. Most importantly, the translated antibody from a single injection of VRC01 mRNA protects humanized mice from intravenous HIV-1 challenge, demonstrating that nucleoside-modified mRNA represents a viable delivery platform for passive immunotherapy against HIV-1 with expansion to a variety of diseases.

HIV-1 entry requires the cell surface expression of CD4 and either the CCR5 or CXCR4 coreceptors on host cells. Individuals homozygous for the ccr5Δ32 polymorphism do not express CCR5 and are protected from infection by CCR5-tropic (R5) virus strains. As an approach to inactivating CCR5, we introduced CCR5-specific zinc-finger nucleases into human CD4+ T cells prior to adoptive transfer, but the need to protect cells from virus strains that use CXCR4 (X4) in place of or in addition to CCR5 (R5X4) remains. Here we describe engineering a pair of zinc finger nucleases that, when introduced into human T cells, efficiently disrupt cxcr4 by cleavage and error-prone non-homologous DNA end-joining. The resulting cells proliferated normally and were resistant to infection by X4-tropic HIV-1 strains. CXCR4 could also be inactivated in ccr5Δ32 CD4+ T cells, and we show that such cells were resistant to all strains of HIV-1 tested. Loss of CXCR4 also provided protection from X4 HIV-1 in a humanized mouse model, though this protection was lost over time due to the emergence of R5-tropic viral mutants. These data suggest that CXCR4-specific ZFNs may prove useful in establishing resistance to CXCR4-tropic HIV for autologous transplant in HIV-infected individuals.

Ongoing clinical trials for treatment of beta-globinopathies by gene therapy involve the transfer of the beta-globin gene, which requires integration of three to four copies per genome in most target cells. This high proviral load may increase genome toxicity, potentially limiting the safety of this therapy and relegating its use to total body myeloablation. We hypothesized that introducing an additional hypersensitive site from the locus control region, the complete sequence of the second intron of the beta-globin gene, and the ankyrin insulator may enhance beta-globin expression. We identified a construct, ALS20, that synthesized significantly higher adult hemoglobin levels than those of other constructs currently used in clinical trials. These findings were confirmed in erythroblastic cell lines and in primary cells isolated from sickle cell disease patients. Bone marrow transplantation studies in beta-thalassemia mice revealed that ALS20 was curative at less than one copy per genome. Injection of human CD34+ cells transduced with ALS20 led to safe, long-term, and high polyclonal engraftment in xenograft experiments. Successful treatment of beta-globinopathies with ALS20 could potentially be achieved at less than two copies per genome, minimizing the risk of cytotoxic events and lowering the intensity of myeloablation.