Introduction Etranacogene dezaparvovec (formerly AMT-061) is the first approved gene therapy for haemophilia B in the EU and US. The HOPE-B pivotal phase 3 clinical trial (NCT03569891) demonstrated superior bleed protection compared to FIX prophylaxis up to 24 months post treatment with ongoing follow-up from Year 2 onward. Here, we report efficacy and safety during Years 1-3.

BACKGROUND Moderate-to-severe hemophilia B is treated with lifelong, continuous coagulation factor IX replacement to prevent bleeding. Gene therapy for hemophilia B aims to establish sustained factor IX activity, thereby protecting against bleeding without burdensome factor IX replacement. METHODS In this open-label, phase 3 study, after a lead-in period (≥6 months) of factor IX prophylaxis, we administered one infusion of adeno-associated virus 5 (AAV5) vector expressing the Padua factor IX variant (etranacogene dezaparvovec; 2×1013 genome copies per kilogram of body weight) to 54 men with hemophilia B (factor IX activity ≤2% of the normal value) regardless of preexisting AAV5 neutralizing antibodies. The primary end point was the annualized bleeding rate, evaluated in a noninferiority analysis comparing the rate during months 7 through 18 after etranacogene dezaparvovec treatment with the rate during the lead-in period. Noninferiority of etranacogene dezaparvovec was defined as an upper limit of the two-sided 95% Wald confidence interval of the annualized bleeding rate ratio that was less than the noninferiority margin of 1.8. Superiority, additional efficacy measures, and safety were also assessed. RESULTS The annualized bleeding rate decreased from 4.19 (95% confidence interval [CI], 3.22 to 5.45) during the lead-in period to 1.51 (95% CI, 0.81 to 2.82) during months 7 through 18 after treatment, for a rate ratio of 0.36 (95% Wald CI, 0.20 to 0.64; P<0.001), demonstrating noninferiority and superiority of etranacogene dezaparvovec as compared with factor IX prophylaxis. Factor IX activity had increased from baseline by a least-squares mean of 36.2 percentage points (95% CI, 31.4 to 41.0) at 6 months and 34.3 percentage points (95% CI, 29.5 to 39.1) at 18 months after treatment, and usage of factor IX concentrate decreased by a mean of 248,825 IU per year per participant in the post-treatment period (P<0.001 for all three comparisons). Benefits and safety were observed in participants with predose AAV5 neutralizing antibody titers of less than 700. No treatment-related serious adverse events occurred. CONCLUSIONS Etranacogene dezaparvovec gene therapy was superior to prophylactic factor IX with respect to the annualized bleeding rate, and it had a favorable safety profile. (Funded by uniQure and CSL Behring; HOPE-B ClinicalTrials.gov number, NCT03569891.).

BACKGROUND:Paroxysmal dystonic choreoathetosis (PDC) is characterized by attacks of involuntary movements that occur spontaneously while at rest and following caffeine or alcohol consumption. Previously, we and others identified a locus for autosomal dominant PDC on chromosome 2q33-2q35.OBJECTIVE:To identify the PDC gene.DESIGN:Analysis of PDC positional candidate genes by exon sequencing and reverse transcription-polymerase chain reaction.SETTING:Outpatient clinical and molecular genetic laboratory at a university hospital. Patients Affected (n = 12) and unaffected (n = 26) subjects from 2 unrelated families with PDC and 105 unrelated control subjects.RESULTS:We identified missense mutations in the myofibrillogenesis regulator gene (MR-1) in affected subjects in 2 unrelated PDC kindreds. These mutations were absent in control subjects and caused substitutions of valine for alanine at amino acid positions 7 and 9. The substitutions disturb interspecies conserved residues and are predicted to alter the MR-1 gene's amino-terminal alpha helix. The MR-1 exon containing these mutations (exon 1) was expressed only in the brain, a finding that explains the brain-specific symptoms of subjects with these mutations.CONCLUSIONS:Although MR-1 gene function is unknown, the precedence of ion channel disturbance in other episodic neurologic disorders suggests that the pathophysiologic features of PDC also involve abnormal ion localization. The discovery that MR-1 mutations underlie PDC provides opportunities to explore this condition's pathophysiologic characteristics and may provide insight into the causes of other paroxysmal neurologic disorders as well as the neurophysiologic mechanisms of alcohol and caffeine, which frequently precipitate PDC attacks.

Mutations in CTNS result in one of three forms of cystinosis: benign, intermediate, or nephropathic. Homozygosity for a nonsense mutation in CTNS (753G -->A), encoding a premature termination codon (PTC) at amino acid 138 (W138X), results in nephropathic cystinosis. Gentamicin is known to induce PTC readthrough and hence full-length protein production. We demonstrate that addition of gentamicin (300 microg/ml) to cystinotic fibroblasts leads to depletion of intracellular cystine in cell lines with a premature termination codon, but not in those with a large deletion or a deletion leading to a frameshift mutation. Plasmids were constructed with GFP as a C-terminal or N-terminal fusion to CTNS. The normal CTNS protein fused with either N- or C-terminal GFP colocalized with Lysotracker red, a fluorescent stain which selectively accumulates in lysosomes. PTC-GFP, a construct with GFP fused to the C-terminus of CTNS containing a PTC, allowed GFP to serve as a reporter of PTC readthrough. No significant fluorescence was observed in PTC-GFP-transfected cells in the absence of gentamicin but was seen and localized to lysosomes in its presence. A patient with a splice site mutation (IVS11 + 2T -->C) that eliminates the GYDQL lysosomal targeting sequence of cystinosin on one allele, and a PTC mutation (753G -->A) on the other, displays the intermediate phenotype. Transfection of the splice site mutant allele into CTNS null fibroblasts produced cystine depletion. Plasmids with GFP fused to the N-terminus of CTNS containing the splice site mutation (GFP-SS) were constructed. While the normal CTNS-GFP fusion protein was found to colocalize with Lysotracker red almost exclusively, the GFP-SS fusion product was found in the plasma membrane and cytoplasm, as well as lysosomes. A second lysosomal targeting motif in CTNS is present in this sequence, just proximal to the mutation, accounting for the partial lysosomal localization.

Aminoglycoside antibiotics suppress nonsense mutations leading to expression of full-length transcripts in the presence of premature termination codons. Fibroblasts derived from cystinosis patients with either homozygous deletion of a 57 kb portion of the CTNS cystine transport gene, homozygous for a 5-base deletion (545 del TCCTT), or heterozygous for a premature termination codon (753 G→A, W138X) and a splice-site mutation (IVS11 +2 T→C), were exposed to gentamycin at a concentration of 300 μg/mL for 15 days. The cells were then harvested and the intracellular cysline content measured by a cystine binding protein assay. At nine days of incubation, cells heterozygous for the premature stop codon and a splice-site mutation demonstrated 43% of the cystine content (0.65 ±0.38 nmol cystine/10 6 vs. 1.51 ±0.10 nmol/10 6 cells) of control cells incubated under identical conditions but not exposed to gentamycin (p< .01). Cells displaying the 57 kb deletion demonstrated no decline in cystine content (101% of control), and cells displaying the 5-base deletion demonstrated increased cystine (199% of control). No cystine depletion by gentamycin was seen at intervals less than nine days, but depletion was maintained through 15 days in the responsive line. Aminoglycosides are nephrotoxic, and cystinosis exerts its major pathological effect on the kidney, nevertheless, these results are intriguing, and suggest the need for further investigation of this category of compounds in altering gene expression in patients with premature stop codons resulting in lysosomal cystine storage.

Six patients with the intermediate form of cystinosis are described. Two have new mutations not previously described. The disease occurs due either to the combination of one mild mutation and one which is known to cause nephropathic cystinosis or to homozygosity for a predicted mild mutation. Partial phenotypic correction of cystinotic fibroblasts by transfection with normal cDNA or a cDNA derived from a mutation causing intermediate cystinosis is demonstrated.

Nephropathic cystinosis is an autosomal recessive lysosomal storage disease characterized by renal failure at 10 years of age and other systemic complications. The gene for cystinosis, CTNS, has 12 exons. Its 2.6-kb mRNA codes for a 367-amino-acid putative cystine transporter with seven transmembrane domains. Previously reported mutations include a 65-kb "European" deletion involving marker D17S829 and 11 small mutations. Mutation analysis of 108 American-based nephropathic cystinosis patients revealed that 48 patients (44%) were homozygous for the 65-kb deletion, 2 had a smaller major deletion, 11 were homozygous and 3 were heterozygous for 753G-->A (W138X), and 24 had 21 other mutations. In 20 patients (19%), no mutations were found. Of 82 alleles bearing the 65-kb deletion, 38 derived from Germany, 28 from the British Isles, and 4 from Iceland. Eighteen new mutations were identified, including the first reported missense mutations, two in-frame deletions, and mutations in patients of African American, Mexican, and Indian ancestry. CTNS mutations are spread throughout the leader sequence, transmembrane, and nontransmembrane regions. According to a cystinosis clinical severity score, homozygotes for the 65-kb deletion and for W138X have average disease, whereas mutations involving the first amino acids prior to transmembrane domains are associated with mild disease. By northern blot analysis, CTNS was not expressed in patients homozygous for the 65-kb deletion but was expressed in all 15 other patients tested. These data demonstrate the origins of CTNS mutations in America and provide a basis for possible molecular diagnosis in this population.

Lysosomes purified by Percoll gradient from normal human fibroblasts (GM0010A) show uptake of Ca2+ in a mediated manner. The uptake is linear over the first 1.5 min and approaches a steady state by 10 min. Uptake is saturable, displaying a Vmax of about 10 pmol/min/unit hexosaminidase at 20 mM Ca2+ (7 nmol/min/mg protein), and a Km of 5.7 mM. Ca2+ uptake increases with increasing extralysosomal pH from 5.0 to 8.5. The Q10 is 1.6, and Ea 8.7 kcal/mol. Uptake of 0.1 mM Ca2+ was inhibited to the extent indicated by 1.0 mM of the following: Cd2+, 100%; Hg2+, 100%; Zn2+, 89%; Mg2+, 77%; Ba2+, 60%; Sr2+, 37%; Fe2+, 20%; Cu2+, 0%. Mono- and trivalent cations had no effect. ATP (1.0 mM) inhibited uptake by 80%, and chloroquine (0.1 mM) inhibited by 60%, as did 1.0 mM L-cystine. Cysteamine, N-ethylmaleimide, and the anions Cl-, SO(2-)4, and acetate had no effect. The calcium ionophore A23187 augmented uptake by 10-fold at 10 microM. Surprisingly, Pb2+ greatly augmented lysosomal Ca2+ uptake in a concentration-dependent manner. Pb2+, however, adversely affected lysosomal latency. Lysosomal calcium uptake was not affected by inositol 1,4,5-triphosphate, and calcium-induced calcium release from lysosomes was not observed. A role for lysosomes in cellular calcium homeostasis has not been previously suggested. This work shows that Ca2+ can be transported into and out of lysosomes and could assist in lysosomal proteolysis. The extent of further lysosomal participation in cellular calcium regulation is unclear.

Lysosomes constitute only 4% of the intracellular volume of a normal human fibroblast. When human fibroblasts are incubated for 2-5 min with 20 microM [35S]cystine in Krebs-Ringer phosphate solution at pH 7.4, a minimum of 50-60% of the total radioactivity taken up by the cells is found sequestered into the lysosomal compartment in the form of cysteine. A lysosomal transport system, highly specific for cysteine, appears to facilitate this rapid lysosomal cysteine sequestration. Time courses of [35S]cysteine uptake into isolated, Percoll-purified fibroblast lysosomes at pH 7.0 and 37 degrees C are linear for the first 4-5 min and attain a steady state by 10 min. Lysosomal cysteine uptake displays a Km of 0.05 mM at pH 7.0 and an activation energy of 21 kcal/mol, corresponding to a Q10 of 3.2. The role of this transport system in delivering cysteine into lysosomes is supported by its pH curve showing a slow rate of cysteine transport at the acidic pHs between 5 and 6, but then increasing sevenfold between pH 6 and 7.5 to be maximally active near the cytosolic pH of 7. Carrier mediation by this lysosomal transport route demonstrates a high specificity for cysteine as indicated by the inability of the following amino acids to significantly inhibit at 5 mM the lysosomal uptake of 0.035 mM [35S]L-cysteine: ala, ser, pro, val, gly, homocysteine, D- or L-penicillamine, arg, asp, or leu. Similarly, D-cysteine and beta-mercaptopropionate were poor inhibitors, suggesting that both the L-isomer and alpha-amino group of cysteine appear to be required for recognition by the cysteine-specific transport system. In contrast, cysteamine, which lacks an alpha-carboxyl group, was able to strongly inhibit lysosomal cysteine uptake. The physiological importance of this cysteine-specific lysosomal transport system may be to aid lysosomal proteolysis by delivering cysteine into the lysosomal compartment to (a) maintain the catalytic activity of the thiol-dependent lysosomal enzymes and (b) break protein disulfide bridges at susceptible linkages, thereby allowing proteins to unfold, facilitating their degradation.

ABSTRACT: Human cystinotic fibroblasts were completely depleted of their accumulated intracellular free cystine within a 2-h time interval when exposed to culture medium containing between 1 and 5 mM mercaptoethylgluconamide. This cystine-depleting action of mercaptoethylgluconamide was observed with three different human cystinotic fibroblast cell lines and with all three cell lines, 2 mM mercaptoethylgluconamide was as effective as 1 mM cysteamine in depleting cells of their intracellular free cystine. Cell viability was excellent for cystinotic fibroblasts exposed to 2 mM mercaptoethylgluconamide for up to 6 days in duration. Mercaptoethylgluconamide (2 mM) was sufficiently stable under cell culture conditions such that a single addition of mercaptoethylgluconamide maintained cystine depletion in human cystinotic fibroblasts for at least a 4-day period. In contrast to cysteamine, 2 mM mercaptoethylgluconamide was not capable of depleting the cystine content of isolated cystinotic lysosomes, implying that cellular integrity is necessary to achieve cystine depletion by mercaptoethylgluconamide. The efficient cystine-depleting action of mercaptoethylgluconamide coupled with its lack of offensive odor encourage further investigation of this agent to possibly complement or supplant the use of cysteamine in the treatment of nephropathic cystinosis.

Exposure of cultured diploid fibroblasts to protease solutions induces a hyperpermeable state which permits entry of exogenous macromolecules directly into the cytosol. We have exploited this finding to devise a microinjection method whose chief advantages are simplicity and good retention of cell viability. Proteins successfully injected by this technique range from insulin to thyroglobulin. The amounts injected range from 4 × 105 to 5 × 106 molecules/cell.

Using a trans-stimulation property associated with lysine exodus, we have demonstrated previously a system mediating the transport of cationic amino acids across the lysosomal membrane of human fibroblasts. By studying instead the uptake of arginine into highly purified flbroblast lysosomes, obtained by centrifuging through Percoll density gradients, we now examine additional characteristics of this system. For arg uptake it displays a broad pH optimum from pH 7.0-8.0. The rate of arg uptake is 10-fold greater at pH 7.0 than 5.0, thus favoring net entry of arg into lysosomes as a result of the low intralysosomal pH. In contrast, external MgATP accelerates lysosomal efflux of cationic amino acids while inhibiting their influx. Trans-stimulation of arg uptake is seen when lysosomes have been loaded with 2-aminoethyl-L-cysteine. Arg uptake (.03 mM) is strongly inhibited by the L-isomers of external 3.3 mM arg, lys, orn, 2, 4-diaminobutyrate, 2-aminoethylcysteine and his, whereas D-arg, neutral and anionic amino acids have little effect. In addition, lysosomal arg uptake is inhibited by α-N-methyl-L-arg (72%) and e-trimethyl-L-lys (49%), neither of which are recognized by the plasma membrane System y+. These observations indicate that lysosomal System y+ is structurally different from System y+ of the plasma membrane of the human fibroblast and various other cells. Thiocholine (TC) depleted cystinotic fibroblasts of their accumulated cystine to the same level and rate as produced by cysteamine supporting the view that TC may react with cystine to form a mixed disulfide recognized by lysosomal System y+ similar to the one formed by cysteamine. Support ackn. from Grant AM32281, NIH.