Safety, pharmacokinetics and CNS distribution of tralesinidase alfa administered via intracerebroventricular infusion to juvenile cynomolgus monkeys.

Mucopolysaccharidosis Type IIIB (MPS IIIB) is an ultrarare, fatal pediatric disease with no approved therapy. It is caused by mutations in the gene encoding for lysosomal enzyme alpha-N-acetylglucosaminidase (NAGLU). Tralesinidase alfa (TA) is a fusion protein comprised of recombinant NAGLU and a modified human insulin-like growth factor 2 that is being developed as an enzyme replacement therapy for MPS IIIB. Since MPS IIIB is a pediatric disease the safety/toxicity, pharmacokinetics and biodistribution of TA were evaluated in juvenile non-human primates that were administered up to 5 weekly intracerebroventricular (ICV) or single intravenous (IV) infusions of TA. TA administered by ICV slow-, ICV isovolumetric bolus- or IV-infusion was well-tolerated, and no effects were observed on clinical observations, electrocardiographic or ophthalmologic parameters, or respiratory rates. The drug-related changes observed were limited to increased cell infiltrates in the CSF and along the ICV catheter track after ICV administration. These findings were not associated with functional changes and are associated with the use of ICV catheters. The CSF PK profiles were consistent across all conditions tested and TA distributed widely in the CNS after ICV administration. Anti-drug antibodies were observed but did not appear to significantly affect the exposure to TA. Correlations between TA concentrations in plasma and brain regions in direct contact with the cisterna magna suggest glymphatic drainage may be responsible for clearance of TA from the CNS. The data support the administration of TA by isovolumetric bolus ICV infusion to pediatric patients with MPS IIIB.

Safety Evaluation of CNS Administered Biologics-Study Design, Data Interpretation, and Translation to the Clinic.

Many central nervous system (CNS) diseases are inadequately treated by systemically administered therapies due to the blood brain barrier (BBB), which prevents achieving adequate drug concentrations at sites of action. Due to the increasing prevalence of neurodegenerative diseases and the inability of most systemically administered therapies to cross the BBB, direct CNS delivery will likely play an increasing role in treatment. Administration of large molecules, cells, viral vectors, oligonucleotides, and other novel therapies directly to the CNS via the subarachnoid space, ventricular system, or parenchyma overcomes this obstacle. Clinical experience with direct CNS administration of small molecule therapies suggests that this approach may be efficacious for the treatment of neurodegenerative disorders using biological therapies. Risks of administration into the brain tissue or cerebrospinal fluid include local damage from implantation of the delivery system and/or administration of the therapeutic and reactions affecting the CNS. Preclinical safety studies on CNS administered compounds must differentiate between the effects of the test article, the delivery device, and/or the vehicle, and assess exacerbations of reactions due to combinations of effects. Animal models characterized for safety assessment of CNS administered therapeutics have enabled human trials, but interpretation can be challenging. This manuscript outlines the challenges of preclinical intrathecal/intracerebroventricular/intraparenchymal studies, evaluation of results, considerations for special endpoints, and translation of preclinical findings to enable first-in-human trials. Recommendations will be made based on the authors' collective experience with conducting these studies to enable clinical development of CNS-administered biologics.

Recombinant human tripeptidyl peptidase-1 infusion to the monkey CNS: safety, pharmacokinetics, and distribution.

CLN2 disease is caused by deficiency in tripeptidyl peptidase-1 (TPP1), leading to neurodegeneration and death. The safety, pharmacokinetics (PK), and CNS distribution of recombinant human TPP1 (rhTPP1) were characterized following a single intracerebroventricular (ICV) or intrathecal-lumbar (IT-L) infusion to cynomolgus monkeys. Animals received 0, 5, 14, or 20mg rhTPP1, ICV, or 14 mg IT-L, in artificial cerebrospinal fluid (aCSF) vehicle. Plasma and CSF were collected for PK analysis. Necropsies occurred at 3, 7, and 14 days post-infusion. CNS tissues were sampled for rhTPP1 distribution. TPP1 infusion was well tolerated and without effect on clinical observations or ECG. A mild increase in CSF white blood cells (WBCs) was detected transiently after ICV infusion. Isolated histological changes related to catheter placement and infusion were observed in ICV treated animals, including vehicle controls. The CSF and plasma exposure profiles were equivalent between animals that received an ICV or IT-L infusion. TPP1 levels peaked at the end of infusion, at which point the enzyme was present in plasma at 0.3% to 0.5% of CSF levels. TPP1 was detected in brain tissues with half-lives of 3-14 days. CNS distribution between ICV and IT-L administration was similar, although ICV resulted in distribution to deep brain structures including the thalamus, midbrain, and striatum. Direct CNS infusion of rhTPP1 was well tolerated with no drug related safety findings. The favorable nonclinical profile of ICV rhTPP1 supports the treatment of CLN2 by direct administration to the CNS.

Safety evaluation of chronic intrathecal administration of heparan N-sulfatase in juvenile cynomolgus monkeys.

An intrathecal (IT) formulation of recombinant human heparan N-sulfatase (HNS) is under development for the treatment of the neurological symptoms of mucopolysaccharidosis IIIA (MPS IIIA; Sanfilippo A disease), the defining clinical feature of this disorder. Since the average age of MPS IIIA patients is 4.5 years, the pivotal toxicology studies for HNS were conducted in juvenile cynomolgus monkeys to evaluate the effects on the developing brain. Monkeys were implanted with an IT-lumbar drug delivery device and dosed every other week by slow bolus administration (1.5, 4.5, or 8.3 mg/dose HNS for 6 months; 12 doses), with device and vehicle controls receiving phosphate-buffered saline or vehicle, respectively. Eight animals per group (four/sex) were necropsied at 3 and 6 months (device control group necropsied at 3 months), and eight animals from the vehicle group and the three HNS-dosed groups were necropsied 1 month after the final IT dose. No HNS-related clinical signs or gross central nervous system lesions were observed. Compared with controls, there were cellular infiltrates of slight-to-minimal mean severity in the meninges/perineurium surrounding the brain/spinal cord correlating with transient increases in cerebrospinal fluid (CSF) leukocytes, predominantly eosinophils, which largely resolved 1 month after the final dose. These changes were not associated with any adverse morphological changes in the brain or spinal cord. There appeared to be a dose-related trend toward higher mean CSF HNS levels and in tissue HNS activity levels in the brain, spinal cord, and liver. The no-observed-adverse-effect-level was 8.3 mg/dose given every other week, the highest dose administered.

Safety evaluation of chronic intrathecal administration of idursulfase-IT in cynomolgus monkeys.

Recombinant human idursulfase, an intravenous enzyme replacement therapy indicated for treatment of somatic symptoms of mucopolysaccharidosis II (Hunter syndrome), is anticipated to have minimal benefit for the cognitive impairment associated with the severe phenotype. Because intrathecal (IT) administration of enzyme replacement therapy for other lysosomal enzyme disorders has shown efficacy in animal models, an IT formulation of idursulfase (idursulfase-IT) and a drug-delivery device (subcutaneous port connected to a lumbar IT catheter) were developed for treating central nervous system (CNS) involvement. In this chronic safety study, cynomolgus monkeys were dosed weekly with IV idursulfase (0.5 mg/kg) and every four weeks with idursulfase-IT (3, 30, and 100 mg) for six months, with device and vehicle controls treated similarly (n = 6, all groups). Necropsies were performed twenty-four hours post-final IT dose or after a recovery period (four weeks post-final dose in vehicle-control, 3 mg, and 100 mg IT groups: n = 6). No clinical signs or gross central nervous system lesions were observed. Compared to controls, more pronounced cellular infiltrates in brain and spinal cord meninges were noted, which largely resolved after the recovery period. Central nervous sytem levels of idursulfase-IT were dose dependent, as determined by enzyme activity and immunohistochemistry. The no-observed-adverse-effect level of idursulfase-IT was 100 mg.

Six-month continuous intraputamenal infusion toxicity study of recombinant methionyl human glial cell line-derived neurotrophic factor (r-metHuGDNF in rhesus monkeys.

Recombinant human glial cell line-derived neurotrophic factor (r-metHuGDNF) is a potent neuronal growth and survival factor that has been considered for clinical use in the treatment of Parkinson's disease (PD). Here we present results of a 6-month toxicology study in rhesus monkeys conducted to support clinical evaluation of chronic intraputamenal infusion of r-metHuGDNF for PD. Monkeys (6-9/sex/group) were treated with 0 (vehicle), 15, 30, or 100 microg/day r-metHuGDNF by continuous unilateral intraputamenal infusion (150 microl/day flow rate) for 6 months; a subset of animals (2-3/sex/group) underwent a subsequent 3-month treatment-free recovery period. Notable observations included reduced food consumption and body weight at 100 microg/day and meningeal thickening underlying the medulla oblongata and/or overlying various spinal cord segments at 30 and 100 microg/day. In addition, multifocal cerebellar Purkinje cell loss (with associated atrophy of the molecular layer and, in some cases, granule cell loss) was observed in 4 monkeys in the 100-microg/day group. This cerebellar finding has not been observed in previous nonclinical studies evaluating r-metHuGDNF. The small number of affected animals precludes definitive conclusions regarding the pathogenesis of the cerebellar lesion, but the data support an association with r-metHuGDNF treatment.

Six-month continuous intraputamenal infusion toxicity study of recombinant methionyl human glial cell line-derived neurotrophic factor (r-metHuGDNF) in rhesus monkeys.

Recombinant human glial cell line-derived neurotrophic factor (r-metHuGDNF) is a potent neuronal growth and survival factor that has been considered for clinical use in the treatment of Parkinson's disease (PD). Here we present results of a 6-month toxicology study in rhesus monkeys conducted to support clinical evaluation of chronic intraputamenal infusion of r-metHuGDNF for PD. Monkeys (6-9/sex/group) were treated with 0 (vehicle), 15, 30, or 100 micro g/day r-metHuGDNF by continuous unilateral intraputamenal infusion (150 micro l/day flow rate) for 6 months; a subset of animals (2-3/sex/group) underwent a subsequent 3-month treatment-free recovery period. Notable observations included reduced food consumption and body weight at 100 micro g/day and meningeal thickening underlying the medulla oblongata and/or overlying various spinal cord segments at 30 and 100 micro g/day. In addition, multifocal cerebellar Purkinje cell loss (with associated atrophy of the molecular layer and, in some cases, granule cell loss) was observed in 4 monkeys in the 100-micro g/day group. This cerebellar finding has not been observed in previous nonclinical studies evaluating r-metHuGDNF. The small number of affected animals precludes definitive conclusions regarding the pathogenesis of the cerebellar lesion, but the data support an association with r-metHuGDNF treatment.