Clinical immunogenicity outcomes from GENEr8-1, a phase 3 study of valoctocogene roxaparvovec, an AAV5-vectored gene therapy for hemophilia A.

Gene transfer therapies utilizing adeno-associated virus (AAV) vectors involve a complex drug design with multiple components that may impact immunogenicity. Valoctocogene roxaparvovec is an AAV serotype 5 (AAV5)-vectored gene therapy for the treatment of hemophilia A that encodes a B-domain-deleted human factor VIII (FVIII) protein controlled by a hepatocyte-selective promoter. Following previous results from the first-in-human phase 1/2 clinical trial, we assessed AAV5-capsid- and transgene-derived FVIII-specific immune responses with 2 years of follow-up data from GENEr8-1, a phase 3, single-arm, open-label study in 134 adult men with severe hemophilia A. No FVIII inhibitors were detected following administration of valoctocogene roxaparvovec. Immune responses were predominantly directed toward the AAV5 capsid, with all participants developing durable anti-AAV5 antibodies. Cellular immune responses specific for the AAV5 capsid were detected in most participants by interferon-γ enzyme-linked immunosorbent spot assay 2 weeks following dose administration and declined or reverted to negative over the first 52 weeks. These responses were weakly correlated with alanine aminotransferase elevations and showed no association with changes in FVIII activity. FVIII-specific cellular immune responses were less frequent and more sporadic compared with those specific for AAV5 and showed no association with safety or efficacy parameters.

Dose selection for intracerebroventricular cerliponase alfa in children with CLN2 disease, translation from animal to human in a rare genetic disease.

Neuronal ceroid lipofuscinosis type 2 (CLN2 disease) is an ultra-rare pediatric neurodegenerative disorder characterized by deficiency of the lysosomal enzyme tripeptidyl peptidase-1 (TPP1). In the absence of adequate TPP1, lysosomal storage material accumulation occurs in the central nervous system (CNS) accompanied by neurodegeneration and neurological decline that culminates in childhood death. Cerliponase alfa is a recombinant human TPP1 enzyme replacement therapy administered via intracerebroventricular infusion and approved for the treatment of CLN2 disease. Here, we describe two allometric methods, calculated by scaling brain mass across species, that informed the human dose selection and exposure prediction of cerliponase alfa from preclinical studies in monkeys and a dog model of CLN2 disease: (1) scaling of dose using a human-equivalent dose factor; and (2) scaling of compartmental pharmacokinetic (PK) model parameters. Source PK data were obtained from cerebrospinal fluid (CSF) samples from dogs and monkeys, and the human exposure predictions were confirmed with CSF data from the first-in-human clinical study. Nonclinical and clinical data were analyzed using noncompartmental analysis and nonlinear mixed-effect modeling approaches. Both allometric methods produced CSF exposure predictions within twofold of the observed exposure parameters maximum plasma concentration (Cmax ) and area under the curve (AUC). Furthermore, cross-species qualification produced consistent and reasonable PK profile predictions, which supported the allometric scaling of model parameters. The challenges faced in orphan drug development place an increased importance on, and opportunity for, data translation from research and nonclinical development. Our approach to dose translation and human exposure prediction for cerliponase alfa may be applicable to other CNS administered therapies being developed.

Clinical Pharmacokinetics and Pharmacodynamics of Cerliponase Alfa, Enzyme Replacement Therapy for CLN2 Disease by Intracerebroventricular Administration.

Cerliponase alfa is recombinant human tripeptidyl peptidase 1 (TPP1) delivered by i.c.v. infusion for CLN2, a pediatric neurodegenerative disease caused by deficiency in lysosomal enzyme TPP1. We report the pharmacokinetics (PK) and pharmacodynamics of cerliponase alfa, the first i.c.v. enzyme replacement therapy, characterized in a phase I/II study. Escalating doses (30-300 mg Q2W) followed by 300 mg Q2W for ≥ 48 weeks were administered in 24 patients aged ≥ 3 years. Concentrations peaked in cerebrospinal fluid (CSF) at the end of ~ 4-hour i.c.v. infusion and 8 hours thereafter in plasma. Plasma exposure was 300-1,000-fold lower than in CSF, with no correlation in the magnitude of peak concentration (Cmax ) or area under the concentration-time curve (AUC) among body sites. There was no apparent accumulation in CSF or plasma exposure with Q2W dosing. Interpatient and intrapatient variability of AUC, respectively, were 31-49% and 24% in CSF vs. 59-103% and 80% in plasma. PK variability was not explained by baseline demographics, as sex, age, weight, and CLN2 disease severity score did not appear to impact CSF or plasma PK. No apparent correlation was noted between CSF or plasma PK and incidence of adverse events (pyrexia, hypersensitivity, seizure, and epilepsy) or presence of antidrug antibodies in CSF and serum. There was no relationship between magnitude of CSF exposure and efficacy (change in CLN2 score from baseline), indicating maximum benefit was obtained across the range of exposures with 300 mg Q2W. Data from this small trial of ultra-rare disease were leveraged to adequately profile cerliponase alfa and support 300 mg i.c.v. Q2W for CLN2 treatment.

Characterization of disease-specific chondroitin sulfate nonreducing end accumulation in mucopolysaccharidosis IVA.

Morquio syndrome type A, also known as MPS IVA, is a rare autosomal recessive disorder caused by deficiency of N-acetylgalactosamine-6-sulfatase, a lysosomal hydrolase critical in the degradation of keratan sulfate (KS) and chondroitin sulfate (CS). The CS that accumulates in MPS IVA patients has a disease-specific nonreducing end (NRE) terminating with N-acetyl-D-galactosamine 6-sulfate, which can be specifically quantified after enzymatic depolymerization of CS polysaccharide chains. The abundance of N-acetyl-D-galactosamine 6-sulfate over other possible NRE structures is diagnostic for MPS IVA. Here, we describe an assay for the liberation and measurement of N-acetyl-D-galactosamine 6-sulfate and explore its application to MPS IVA patient samples in pilot studies examining disease detection, effects of age and treatment with enzyme-replacement therapy. This assay complements the existing urinary KS assay by quantifying CS-derived substrates, which represent a distinct biochemical aspect of MPS IVA. A more complete understanding of the disease could help to more definitively detect disease across age ranges and more completely measure the pharmacodynamic efficacy of therapies. Larger studies will be needed to clarify the potential value of this CS-derived substrate to manage disease in MPS IVA patients.

Immunogenicity to cerliponase alfa intracerebroventricular enzyme replacement therapy for CLN2 disease: Results from a Phase 1/2 study.

Treatment with intracerebroventricular (ICV)-delivered cerliponase alfa enzyme replacement therapy (ERT) in a Phase 1/2 study of 24 subjects with CLN2 disease resulted in a meaningful preservation of motor and language (ML) function and was well tolerated. Treatment was associated with anti-drug antibody (ADA) production in the cerebrospinal fluid (CSF) of 6/24 (25%) and in the serum of 19/24 (79%) of clinical trial subjects, respectively, over a mean exposure of 96.4 weeks (range 0.1-129 weeks). Neutralizing antibodies (NAb) were not detected in the CSF of any of the subjects. No events of anaphylaxis were reported. Neither the presence of serum ADA nor drug-specific immunoglobulin E was associated with the incidence or severity of hypersensitivity adverse events. Serum and CSF ADA titers did not correlate with change in ML score. Therefore, the development of an ADA response to cerliponase alfa is not predictive of an adverse safety profile or poor treatment outcome.