Margaret Humphries

Sustained transgene expression despite T lymphocyte responses in a clinical trial of rAAV1-AAT gene therapy

Alpha-1 antitrypsin (AAT) deficiency is well-suited as a target for human gene transfer. We performed a phase 1, open-label, dose-escalation clinical trial of a recombinant adeno-associated virus (rAAV) vector expressing normal (M) AAT packaged into serotype 1 AAV capsids delivered by i.m. injection. Nine AAT-deficient subjects were enrolled sequentially in cohorts of 3 each at doses of 6.9 × 1012, 2.2 × 1013, and 6.0 × 1013 vector genome particles per patient. Four subjects receiving AAT protein augmentation discontinued therapy 28 or 56 days before vector administration. Vector administration was well tolerated, with only mild local reactions and 1 unrelated serious adverse event (bacterial epididymitis). There were no changes in hematology or clinical chemistry parameters. M-specific AAT was expressed above background in all subjects in cohorts 2 and 3 and was sustained at levels 0.1% of normal for at least 1 year in the highest dosage level cohort, despite development of neutralizing antibody and IFN-γ enzyme-linked immunospot responses to AAV1 capsid at day 14 in all subjects. These findings suggest that immune responses to AAV capsid that develop after i.m. injection of a serotype 1 rAAV vector expressing AAT do not completely eliminate transduced cells in this context.

Phase I Trial of Intranasal and Endobronchial Administration of a Recombinant Adeno-Associated Virus Serotype 2 (rAAV2)-CFTR Vector in Adult Cystic Fibrosis Patients: A Two-Part Clinical Study

Recombinant adeno-associated serotype 2-based vectors (rAAV2) possess a number of theoretical advantages for cystic fibrosis (CF) gene therapy because they elicit little or no inflammatory response and generally result in stable expression. rAAV2 vectors expressing the cystic fibrosis transmembrane conductance regulator (CFTR) gene have previously been shown to mediate stable correction of the CF defect in CF bronchial epithelial cells and stable expression of CFTR in rabbit and nonhuman primate models. Here we report the results of the first trial initiated with rAAV in humans, a phase I study in 25 adult and adolescent CF patients with mild to moderate lung disease. Doses of the rAAV-CFTR vector (tgAAVCF) ranging from 3 x 10(1) to 1 x 10(9) replication units (RU), which is equivalent to approximately 6 x 10(4) to 2 x 10(12) DNase resistant particles (DRP), were administered to one side of the nose and to the superior segment of the lower lobe of the right lung. Several adverse events were noted prior to and/or after vector delivery, but most of them appeared to be related to the endogenous CF lung disease or a result of the bronchoscopic procedures. Only one of the serious events was judged to be possibly vector-related (based on temporal association), and this event was a pulmonary exacerbation very similar to several others experienced by the same subject in the three months preceding vector delivery. Vector shedding was minimal throughout the study, and serum-neutralizing antibodies were detected after vector delivery to subjects in the highest dosage cohorts. Gene transfer as measured by DNA polymerase chain reaction (PCR) was not observed until cohort 10 in nasal and bronchial epithelia. Sporadic low-level copy numbers suggested gene transfer of anywhere from 0.002 copies per cell up to 0.5 copies per cell was possible; however, DNA PCR was positive in lungs prior to direct dosing suggesting aspiration from the nasal dosing. These data indicate the need for continued evaluation of rAAV-CFTR vectors in additional clinical trials.

Phase 2 Clinical Trial of a Recombinant Adeno-Associated Viral Vector Expressing α1-Antitrypsin: Interim Results

Recombinant adeno-associated virus (rAAV) vectors offer promise for the gene therapy of α(1)-antitrypsin (AAT) deficiency. In our prior trial, an rAAV vector expressing human AAT (rAAV1-CB-hAAT) provided sustained, vector-derived AAT expression for >1 year. In the current phase 2 clinical trial, this same vector, produced by a herpes simplex virus complementation method, was administered to nine AAT-deficient individuals by intramuscular injection at doses of 6.0×10(11), 1.9×10(12), and 6.0×10(12) vector genomes/kg (n=3 subjects/dose). Vector-derived expression of normal (M-type) AAT in serum was dose dependent, peaked on day 30, and persisted for at least 90 days. Vector administration was well tolerated, with only mild injection site reactions and no serious adverse events. Serum creatine kinase was transiently elevated on day 30 in five of six subjects in the two higher dose groups and normalized by day 45. As expected, all subjects developed anti-AAV antibodies and interferon-γ enzyme-linked immunospot responses to AAV peptides, and no subjects developed antibodies to AAT. One subject in the mid-dose group developed T cell responses to a single AAT peptide unassociated with any clinical effects. Muscle biopsies obtained on day 90 showed strong immunostaining for AAT and moderate to marked inflammatory cell infiltrates composed primarily of CD3-reactive T lymphocytes that were primarily of the CD8(+) subtype. These results support the feasibility and safety of AAV gene therapy for AAT deficiency, and indicate that serum levels of vector-derived normal human AAT >20 μg/ml can be achieved. However, further improvements in the design or delivery of rAAV-AAT vectors will be required to achieve therapeutic target serum AAT concentrations.

Phase I trial of intramuscular injection of a recombinant adeno-associated virus alpha 1-antitrypsin (rAAV2-CB-hAAT) gene vector to AAT-deficient adults.

A recombinant virus vector constructed from adeno-associated virus (AAV) that has been altered to carry the human alpha1-antitrypsin (hAAT) gene expressed from a hybrid chicken beta-actin promoter with a cytomegalovirus enhancer has been developed. The construct has been shown to initiate the production of hAAT in animal models closely matching the proposed human trial. The proposed clinical trial is an open-label, phase I study administering recombinant adeno-associated virus alpha1-antitrypsin (rAAV2-CB-hAAT) gene vector intramuscularly to AAT-deficient human subjects where gene expression can be measured directly in blood samples to assess safety. Safety parameters will be measurement of changes in serum chemistries and hematology, urinalysis, pulmonary function testing, semen assay for vector genomes, immunologic response to AAT, and AAV, as well as reported subject history of any symptoms.

Human Treg responses allow sustained recombinant adeno-associated virus–mediated transgene expression

Recombinant adeno-associated virus (rAAV) vectors have shown promise for the treatment of several diseases; however, immune-mediated elimination of transduced cells has been suggested to limit and account for a loss of efficacy. To determine whether rAAV vector expression can persist long term, we administered rAAV vectors expressing normal, M-type α-1 antitrypsin (M-AAT) to AAT-deficient subjects at various doses by multiple i.m. injections. M-specific AAT expression was observed in all subjects in a dose-dependent manner and was sustained for more than 1 year in the absence of immune suppression. Muscle biopsies at 1 year had sustained AAT expression and a reduction of inflammatory cells compared with 3 month biopsies. Deep sequencing of the TCR Vβ region from muscle biopsies demonstrated a limited number of T cell clones that emerged at 3 months after vector administration and persisted for 1 year. In situ immunophenotyping revealed a substantial Treg population in muscle biopsy samples containing AAT-expressing myofibers. Approximately 10% of all T cells in muscle were natural Tregs, which were activated in response to AAV capsid. These results suggest that i.m. delivery of rAAV type 1-AAT (rAAV1-AAT) induces a T regulatory response that allows ongoing transgene expression and indicates that immunomodulatory treatments may not be necessary for rAAV-mediated gene therapy.

Results at 2 Years after Gene Therapy for RPE65-Deficient Leber Congenital Amaurosis and Severe Early-Childhood-Onset Retinal Dystrophy

PURPOSE To provide an initial assessment of the safety of a recombinant adeno-associated virus vector expressing RPE65 (rAAV2-CB-hRPE65) in adults and children with retinal degeneration caused by RPE65 mutations. DESIGN Nonrandomized, multicenter clinical trial. PARTICIPANTS Eight adults and 4 children, 6 to 39 years of age, with Leber congenital amaurosis (LCA) or severe early-childhood-onset retinal degeneration (SECORD). METHODS Patients received a subretinal injection of rAAV2-CB-hRPE65 in the poorer-seeing eye, at either of 2 dose levels, and were followed up for 2 years after treatment. MAIN OUTCOME MEASURES The primary safety measures were ocular and nonocular adverse events. Exploratory efficacy measures included changes in best-corrected visual acuity (BCVA), static perimetry central 30° visual field hill of vision (V30) and total visual field hill of vision (VTOT), kinetic perimetry visual field area, and responses to a quality-of-life questionnaire. RESULTS All patients tolerated subretinal injections and there were no treatment-related serious adverse events. Common adverse events were those associated with the surgical procedure and included subconjunctival hemorrhage in 8 patients and ocular hyperemia in 5 patients. In the treated eye, BCVA increased in 5 patients, V30 increased in 6 patients, VTOT increased in 5 patients, and kinetic visual field area improved in 3 patients. One subject showed a decrease in BCVA and 2 patients showed a decrease in kinetic visual field area. CONCLUSIONS Treatment with rAAV2-CB-hRPE65 was not associated with serious adverse events, and improvement in 1 or more measures of visual function was observed in 9 of 12 patients. The greatest improvements in visual acuity were observed in younger patients with better baseline visual acuity. Evaluation of more patients and a longer duration of follow-up will be needed to determine the rate of uncommon or rare side effects or safety concerns.

Preclinical Evaluation of a Recombinant Adeno-Associated Virus Vector Expressing Human Alpha-1 Antitrypsin Made Using a Recombinant Herpes Simplex Virus Production Method

Recombinant adeno-associated virus (rAAV) vectors offer promise for gene therapy of alpha-1 antitrypsin (AAT) deficiency. A toxicology study in mice evaluated intramuscular injection of an rAAV vector expressing human AAT (rAAV-CB-hAAT) produced using a herpes simplex virus (HSV) complementation system or a plasmid transfection (TFX) method at doses of 3 × 10(11) vg (1.2 × 10(13) vg/kg) for both vectors and 2 × 10(12) vg (8 × 10(13) vg/kg) for the HSV-produced vector. The HSV-produced vector had favorable in vitro characteristics in terms of purity, efficiency of transduction, and hAAT expression. There were no significant differences in clinical findings or hematology and clinical chemistry values between test article and control groups and no gross pathology findings. Histopathological examination demonstrated minimal to mild changes in skeletal muscle at the injection site, consisting of focal chronic interstitial inflammation and muscle degeneration, regeneration, and vacuolization, in vector-injected animals. At the 3 × 10(11) vg dose, serum hAAT levels were higher with the HSV-produced vector than with the TFX-produced vector. With the higher dose of HSV-produced vector, the increase in serum hAAT levels was dose-proportional in females and greater than dose-proportional in males. Vector copy numbers in blood were highest 24 hr after dosing and declined thereafter, with no detectable copies present 90 days after dosing. Antibodies to hAAT were detected in almost all vector-treated animals, and antibodies to HSV were detected in most animals that received the highest vector dose. These results support continued development of rAAV-CB-hAAT for treatment of AAT deficiency.

5 Year Expression and Neutrophil Defect Repair after Gene Therapy in Alpha-1 Antitrypsin Deficiency

Alpha-1 antitrypsin deficiency is a monogenic disorder resulting in emphysema due principally to the unopposed effects of neutrophil elastase. We previously reported achieving plasma wild-type alpha-1 antitrypsin concentrations at 2.5%–3.8% of the purported therapeutic level at 1 year after a single intramuscular administration of recombinant adeno-associated virus serotype 1 alpha-1 antitrypsin vector in alpha-1 antitrypsin deficient patients. We analyzed blood and muscle for alpha-1 antitrypsin expression and immune cell response. We also assayed previously reported markers of neutrophil function known to be altered in alpha-1 antitrypsin deficient patients. Here, we report sustained expression at 2.0%–2.5% of the target level from years 1–5 in these same patients without any additional recombinant adeno-associated virus serotype-1 alpha-1 antitrypsin vector administration. In addition, we observed partial correction of disease-associated neutrophil defects, including neutrophil elastase inhibition, markers of degranulation, and membrane-bound anti-neutrophil antibodies. There was also evidence of an active T regulatory cell response (similar to the 1 year data) and an exhausted cytotoxic T cell response to adeno-associated virus serotype-1 capsid. These findings suggest that muscle-based alpha-1 antitrypsin gene replacement is tolerogenic and that stable levels of M-AAT may exert beneficial neutrophil effects at lower concentrations than previously anticipated.

Results at 5 Years After Gene Therapy for RPE65-Deficient Retinal Dystrophy

Previously, results at 2 years after subretinal injection of a recombinant adeno-associated virus vector expressing RPE65 (rAAV2-CB-hRPE65) in eight adults and four children with retinal degeneration caused by RPE65 mutations were reported. Now, results at 5 years after treatment in 11 of these subjects are reported. Subjects received a subretinal injection of rAAV2-CB-hRPE65 in the poorer-seeing eye, at either of two dose levels, and were followed for 5 years after treatment. The primary safety outcomes were ocular and non-ocular adverse events. Efficacy outcomes included changes in best corrected visual acuity, static perimetry hill of vision measurements for the central 30° (V30), and total (VTOT) visual field and kinetic perimetry visual field area. The only adverse events reported during years 3, 4, and 5 were minor intercurrent illnesses. Pediatric subjects had improvement in visual acuity and static perimetry in the treated eye, sometimes with a smaller improvement in the untreated eye, during the first 2 years of the study that persisted during years 3-5, with no consistent changes in kinetic perimetry during the study. Most adult subjects had no consistent changes in visual acuity or static perimetry during the study. Three adult subjects with markedly abnormal baseline kinetic visual field area had improvement in the treated eye during the first 1-2 years after treatment, but the absolute magnitude of the improvement was small and was not sustained at subsequent visits. There were no clinically significant adverse events. Visual acuity and static perimetry testing results suggest that treating patients at a younger age is associated with better visual function outcomes during 5 years after treatment.

24. Sustained Expression with Partial Correction of Neutrophil Defects 5 Years After Intramuscular rAAV1 Gene Therapy for Alpha-1 Antitrypsin Deficiency

Alpha-1 antitrypsin (AAT) deficiency is a common monogenic disorder resulting in emphysema, which is currently treated with weekly infusions of protein replacement. We previously reported achieving plasma wild-type (M) AAT concentrations at 2.5-3.8% of the therapeutic level at 1 year after intramuscular (IM) administration of 6×1012vg/kg of a recombinant adeno-associated virus serotype 1 (rAAV1)-AAT vector in AAT-deficient patients, with an associated regulatory T cell (Treg) response to AAV1 capsid epitopes in the absence of any exogenous immune suppression. Here, we report sustained expression, at >2% of the therapeutic level, for 5 years after one-time treatment with rAAV1-AAT in an AAT-deficient patient from that study, with the partial correction of neutrophil defects previously reported in AAT-deficient patients. There was also evidence of an in-situ Treg response and an exhausted CD8+ T cell response to AAV1 capsid. These findings suggest that muscle-based AAT gene replacement is tolerogenic and that very stable levels of M AAT may exert beneficial effects at lower concentrations than previously anticipated.