Three-Year Safety Results of SAR422459 (EIAV-ABCA4) Gene Therapy in Patients With ABCA4-Associated Stargardt Disease: An Open-Label Dose-Escalation Phase I/IIa Clinical Trial, Cohorts 1-5.

PURPOSE: To report on the safety of the first 5 cohorts of a gene therapy trial using recombinant equine infectious anemia virus expressing ABCA4 (EIAV-ABCA4) in adults with Stargardt dystrophy due to mutations in ABCA4. DESIGN: Nonrandomized multicenter phase I/IIa clinical trial. METHODS: Patients received a subretinal injection of EIAVABCA4 in the worse-seeing eye at 3 dose levels and were followed for 3 years after treatment. MAIN OUTCOME MEASURES: The primary end point was ocular and systemic adverse events. The secondary end points were best-corrected visual acuity, static perimetry, kinetic perimetry, total field hill of vision, full field electroretinogram, multifocal ERG, color fundus photography, short-wavelength fundus autofluorescence, and spectral domain optical coherence tomography. RESULTS: The subretinal injections were well tolerated by all 22 patients across 3 dose levels. There was 1 case of a treatment-related ophthalmic serious adverse event in the form of chronic ocular hypertension. The most common adverse events were associated with the surgical procedure. In 1 patient treated with the highest dose, there was a significant decline in the number of macular flecks as compared with the untreated eye. However, in 6 patients, hypoautofluorescent changes were worse in the treated eye than in the untreated eye. Of these, 1 patient had retinal pigment epithelium atrophy that was characteristic of tissue damage likely associated with bleb induction. No patients had any clinically significant changes in best-corrected visual acuity, static perimetry, kinetic perimetry, total field hill of vision, full field electroretinogram, or multifocal ERG attributable to the treatment. CONCLUSIONS: Subretinal treatment with EIAV-ABCA4 was well tolerated with only 1 case of ocular hypertension. No clinically significant changes in visual function tests were found to be attributable to the treatment. However, 27% of treated eyes showed exacerbation of retinal pigment epithelium atrophy on fundus autofluorescence. There was a significant reduction in macular flecks in 1 treated eye from the highest dose cohort. Additional follow-up and continued investigation in more patients will be required to fully characterize the safety and efficacy of EIAV-ABCA4.

Plasma/blood pharmacokinetics and metabolism after dermal exposure to para-aminophenol or para-phenylenediamine.

The pharmacokinetics and metabolism following dermal application of [(14)C]-para-aminophenol (PAP) or [(14)C]-para-phenylenediamine (PPD) were investigated. Groups of rats were treated under occlusion for 24 h with 12.5 mg/kg [(14)C]-PAP, or for 4h with 50 mg/kg [(14)C]-PPD on 10% or 20% of their body surface area, respectively. A female minipig was also treated dermally (24 h, occlusion) with 4.7 mg/kg [(14)C]-PAP on 10% of its body surface area. Blood and plasma samples were analysed for radioactivity and presence of metabolites. In PAP-treated rats, mean plasma levels at 0.5, 1, 2, 4, 8 or 24h were 0.16, 0.24, 0.38, 0.50, 0.36 or 0.14 microg [(14)C]-PAP equivalents/ml, respectively. The plasma half-life was 5.95 h, the C(max) was 0.5 microg/ml, the t(max) was 4 h, and the AUC(0-infinity) was 9.27 microg-equivalentsh/ml. No free PAP was detected in the plasma, but 3 metabolites (M1, M2 and M3) were found in 2-, 4- or 8-h samples at ranges from 0% to 17.7% (M1), 27.6% to 45.0% (M2) or 46.9% to 70% (M3) of the total plasma radioactivity. M2 was identified as acetylated PAP (paracetamol, acetaminophen, APAP), whereas M1 and M3 were identified as O-glucuronide or O-sulfate conjugates of APAP, respectively. In the pig, very low levels of radioactivity (C(max) of approximately 10 ng/ml) were found in the blood, and identified as APAP. Analysis of plasma of PPD-treated rats at 4 h after topical treatment revealed levels of 1.41 +/- 0.34 microg/ml [(14)C]-PPD-equivalents in males, and 7.40 +/- 1.83 microg/ml in females. Radioactivity, reflected a single metabolite, which was identified to be N,N'-diacetylated PPD. Comparison of the plasma APAP levels in rats or the pig following topical PAP with corresponding human plasma levels after a single oral therapeutic dose of APAP suggested a substantial margin of safety. Overall, the results suggest that topically applied PAP or PPD are metabolised in the skin, presumably by N-acetyltransferase-1 resulting in systemic exposure to acetylated metabolites, and not to their parent arylamines.

Comparative metabolism of methyl isobutyl carbinol and methyl isobutyl ketone in male rats.

Methyl isobutyl carbinol (MIBC) is an oxygenated solvent that is metabolized to methylisobutyl ketone (MIBK) and then to 4-hydroxymethyl-4-methyl-2-pentanone (HMP). Plasma levels of MIBC, MIBK and HMP were determined up to 12 h after a single oral 5 mmol/kg dose of MIBC or MIBK to male rats. The major material in the plasma in both cases was HMP, with similar areas-under-the-curve (AUC) and C(max) at 9 h after dosing. MIBK plasma levels and AUC were also comparable after MIBK or MIBC administration. MIBC AUC was only about 6% of the total material in the blood after MIBC, and insignificant after MIBK administration. No other metabolites were detected in the plasma under the analytical conditions used. The extent of metabolism of MIBC to MIBK, by comparing combined AUCs for MIBK and HMP, was at least 73%. The limited systemic toxicity data for MIBC are consistent with those for MIBK, which has been well studied. The metabolic equivalency of MIBC with MIBK indicates that MIBC will have a low potential for toxicity similar to that of MIBK, and reduces the need for additional animal studies.