Modest Blood-Brain Barrier Permeability of the Cyclodextrin Kleptose: Modification by Efflux and Luminal Surface Binding.

Cyclodextrins (CDs) have a variety of uses from acting as excipients to aiding the ability of lipid soluble drugs to cross the blood-brain barrier (BBB). They are being investigated as an active pharmaceutical ingredient, most recently for the treatment of Niemann-Pick disease, a lysosomal storage disease. Cyclodextrins are helpful in animal models and human subjects/patients afflicted with Neimann-Pick disease, including improving the neurologic component of the disease. The improvement in brain disease by intravenous administration implies that CDs can cross the BBB; however, there are only a few studies that have directly addressed this. In the current studies, multiple-time regression analysis indicated that 2-hydroxypropyl-ß-cyclodextrin [Kleptose (Klep)] radioactively labeled with 14C (C-Klep) crossed the BBB at a slow rate by a nonsaturable mechanism consistent with transcellular diffusion. However, the rate of transport varied greatly by the brain region with no detectable uptake by the spinal cord; additionally, many regions rapidly reached equilibrium between the brain and blood. The presence of a brain-to-blood efflux system was also detected and much of the C-Klep did not completely cross the BBB, but loosely adhered to the luminal surface of brain endothelial cells. Peripheral tissues also took up C-Klep, with the kidney taking up the most, which is consistent with renal clearance. In conclusion, we demonstrated minimal uptake of the ß-cyclodextrin Kleptose by the brain with accumulation being affected by efflux and reversible luminal binding. SIGNIFICANCE STATEMENT: This cyclodextrin, which produces therapeutic effects on the central nervous system after peripheral administration, penetrates the BBB poorly. Uptake by the brain to a therapeutic level will likely be difficult to achieve without giving high peripheral doses, bypassing the BBB, or otherwise altering penetration into the brain.

Brain uptake and distribution patterns of 2-hydroxypropyl-ß-cyclodextrin after intrathecal and intranasal administration.

OBJECTIVES: Cyclodextrins are increasingly used therapeutically. For example, 2-hydroxypropyl-ß-cyclodextrin (kleptose) is used for the treatment of Niemann-Pick disease. Kleptose crosses the blood-brain barrier poorly, in part because of a central nervous system (CNS)-to-blood (efflux) transporter, and so is administered by the intrathecal (IT) route in the treatment of Niemann-Pick disease. METHODS: Here, we evaluated the uptake and distribution of kleptose by the brain and spinal cord after intranasal (IN) or IT delivery. KEY FINDINGS: Kleptose distributed to all regions of the brain and spinal cord after IN administration, with only 3.27% of the administered dose entering the bloodstream. Intrathecal delivery produced levels in the whole brain about 40 times higher than intranasal administration and about 20 times higher than previously found after intravenous administration. About 70-90% of the IT dose rapidly entered the bloodstream, in part because of the previously described efflux transporter. The uptake by CNS after IN and IT was both non-saturable. The uptake by the olfactory bulb, hypothalamus and pons-medulla was favoured by all routes of administration. CONCLUSIONS: Kleptose was taken up by all regions of the CNS after either IN or IT administration, but IN administration resulted in only a fraction of the uptake of the IT route.

Iodine-124 as a label for pharmacological PET imaging.

With the growing number of biotechnology products and drug delivery systems entering preclinical and clinical studies, pharmacological imaging studies with PET play an increasingly significant role. Such studies often require investigation of slow and complex pharmacokinetics (PK). This suggests labeling of the drug candidate with radionuclides that have long physical half-lives. Among the currently available PET positron emitters, ¹²4I has the longest physical half-life (4.2 days). This, combined with the well-investigated behavior of iodine in vivo, makes ¹²4I very attractive for pharmacological studies. However, the high energy of the positrons emitted by ¹²4I and the presence of single photons in the ¹²4I emission can potentially introduce limitations in the quantitative analysis of the images. The objective of this research was to determine whether the use of ¹²4I as a PET label provides data quality suitable for PK studies. The study was carried out using MicroPET P4 scanner (Siemens/Concorde Microsystems). Spatial resolution, count-rate performance, sensitivity and scatter fraction were measured using a line source and a cylindrical phantom. Model animal studies in rats and cynomolgus monkeys were carried out using human recombinant proteins. The proteins were labeled with ¹²4I, up to 185 MBq/mg. The transaxial and axial spatial resolutions in the center of the camera were satisfactory and higher for OSEM3D/MAP than FORE-2DFBP (FWHM 2.52 vs 3.31 mm, and 3.10 vs 3.69 mm). Linearity of the true coincidence count-rate was observed up to 44 MBq. Animal studies demonstrated excellent delineation and resolution of even very small organs. At optimal doses, 2-10 MBq per animal for rodents and 4-10 MBq per kg of body weight for larger animals, the quality of numerical data was appropriate for PK analysis in all experimental timeframes from minutes (dynamic studies) to 10 days. Overall, the data suggest that ¹²4I is an excellent label for quantitative pharmacological PET imaging studies.

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.

2-Hydroxypropyl-ß-cyclodextrins and the Blood-Brain Barrier: Considerations for Niemann-Pick Disease Type C1.

The rare, chronic, autosomal-recessive lysosomal storage disease Niemann-Pick disease type C1 (NPC1) is characterized by progressively debilitating and ultimately fatal neurological manifestations. There is an urgent need for disease-modifying therapies that address NPC1 neurological pathophysiology, and passage through the blood-brain barrier represents an important consideration for novel NPC1 drugs. Animal investigations of 2-hydroxypropyl-ß-cyclodextrins (HPßCD) in NPC1 in mice demonstrated that HPßCD does not cross the blood-brain barrier in significant amounts but suggested a potential for these complex oligosaccharides to moderately impact CNS manifestations when administered subcutaneously or intraperitoneally at very high doses; however, safety concerns regarding pulmonary toxicity were raised. Subsequent NPC1 investigations in cats demonstrated far greater HPßCD efficacy at much lower doses when the drug was administered directly to the CNS. Based on this, a phase 1/2a clinical trial was initiated with intrathecal administration of a specific, wellcharacterized mixture of HPßCD, with a tightly controlled molar substitution specification and a defined molecular "fingerprint" of the different species. The findings were very encouraging and a phase 2b/3 clinical trial has completed enrollment and is underway. In addition, phase 1 clinical studies utilizing high-dose intravenous administration of a different HPßCD are currently recruiting. Independent studies are needed for each product to satisfactorily address questions of safety, efficacy, dosing, and route of administration. The outcomes cannot be assumed to be translatable between HPßCD products and/or routes of administration.

Intrathecal delivery of protein therapeutics to the brain: a critical reassessment.

Disorders of the central nervous system (CNS), including stroke, neurodegenerative diseases, and brain tumors, are the world's leading causes of disability. Delivery of drugs to the CNS is complicated by the blood-brain barriers that protect the brain from the unregulated leakage and entry of substances, including proteins, from the blood. Yet proteins represent one of the most promising classes of therapeutics for the treatment of CNS diseases. Many strategies for overcoming these obstacles are in development, but the relatively straightforward approach of bypassing these barriers through direct intrathecal administration has been largely overlooked. Originally discounted because of its lack of usefulness for delivering small, lipid-soluble drugs to the brain, the intrathecal route has emerged as a useful, in some cases perhaps the ideal, route of administration for certain therapeutic protein and targeted disease combinations. Here, we review blood-brain barrier functions and cerebrospinal fluid dynamics and their relevance to drug delivery via the intrathecal route, discuss animal and human studies that have investigated intrathecal delivery of protein therapeutics, and outline several characteristics of protein therapeutics that can allow them to be successfully delivered intrathecally.

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.

CNS penetration of intrathecal-lumbar idursulfase in the monkey, dog and mouse: implications for neurological outcomes of lysosomal storage disorder.

A major challenge for the treatment of many central nervous system (CNS) disorders is the lack of convenient and effective methods for delivering biological agents to the brain. Mucopolysaccharidosis II (Hunter syndrome) is a rare inherited lysosomal storage disorder resulting from a deficiency of iduronate-2-sulfatase (I2S). I2S is a large, highly glycosylated enzyme. Intravenous administration is not likely to be an effective therapy for disease-related neurological outcomes that require enzyme access to the brain cells, in particular neurons and oligodendrocytes. We demonstrate that intracerebroventricular and lumbar intrathecal administration of recombinant I2S in dogs and nonhuman primates resulted in widespread enzyme distribution in the brain parenchyma, including remarkable deposition in the lysosomes of both neurons and oligodendrocytes. Lumbar intrathecal administration also resulted in enzyme delivery to the spinal cord, whereas little enzyme was detected there after intraventricular administration. Mucopolysaccharidosis II model is available in mice. Lumbar administration of recombinant I2S to enzyme deficient animals reduced the storage of glycosaminoglycans in both superficial and deep brain tissues, with concurrent morphological improvements. The observed patterns of enzyme transport from cerebrospinal fluid to the CNS tissues and the resultant biological activity (a) warrant further investigation of intrathecal delivery of I2S via lumbar catheter as an experimental treatment for the neurological symptoms of Hunter syndrome and (b) may have broader implications for CNS treatment with biopharmaceuticals.

Protection against lethal intra-abdominal sepsis by 1-(3-dimethylaminopropyl)-3-ethylurea.

Sodium hyaluronate-carboxymethylcellulose (HA/CMC) formulations are gels that effectively reduce postoperative adhesions in both animals and humans, when placed in the peritoneal or pelvic cavities concomitant with surgical manipulation. However, it has been suggested that the use of these products may increase the risk of peritoneal infection after contamination with intestinal contents during surgery. Using the rat intra-abdominal sepsis model, we found that administration of HA/CMC gels before bacterial challenge did not increase mortality but did significantly protect rats against lethal infection. This effect was dose and time dependent. Protection was conferred not by the HA/CMC gels themselves but by 1-(3-dimethylaminopropyl)-3-ethylurea (EDU), a small molecule released from the gel complex under physiologic conditions. Our results suggest that the protective effect exhibited by EDU is related to down-regulation of T cell-dependent responses and suppression of the proinflammatory-cytokine cascade associated with mortality during the early phase of disease.