Long-term treatment with ganaxolone for seizures associated with cyclin-dependent kinase-like 5 deficiency disorder: Two-year open-label extension follow-up.

OBJECTIVE: In the placebo-controlled, double-blind phase of the Marigold study (NCT03572933), ganaxolone significantly reduced major motor seizure frequency (MMSF) in patients with cyclin-dependent kinase-like 5 deficiency disorder (CDD). We report 2-year safety and clinical outcomes data from the open-label extension (OLE) phase of Marigold. METHODS: Patients with CDD who completed the double-blind phase were eligible to continue in the OLE. Efficacy assessments included MMSF reduction from prerandomization baseline, responder rates, and Clinical Global Impression-Improvement scores, including assessment of seizure intensity and duration (CGI-CSID). Safety assessments included treatment-emergent adverse events (TEAEs) and TEAEs leading to discontinuation. RESULTS: Of 101 patients who enrolled in Marigold, 88 (87.1%) entered the OLE (median age = 5 years, 79.5% female). Median 28-day MMSF at baseline was 50.6. At 2 years in the OLE (months 22-24), MMSF was reduced by a median of 48.2% (n = 50); when missing data were imputed, median reduction in MMSF was 43.8% using a mixed effects model and 27.4% using a last observation carried forward model. During months 22-24, 23 of 50 (46.0%) patients experienced reductions in MMSF of ≥50%; 12 of 50 (24.0%) patients experienced MMSF reductions of ≥75%. During months 22-24, 40 of 49 (81.6%) patients were rated by caregivers as having improvement in seizure-related outcomes based on CGI-CSID scores. Thirty-seven patients discontinued ganaxolone due to lack of efficacy (n = 13), withdrawal by caregiver (n = 12), adverse event (n = 10), physician decision (n = 1), or death (n = 1; unrelated to study drug). The most common treatment-related TEAEs were somnolence (17.0%), seizure (11.4%), and decreased appetite (5.7%). Patients reported serious TEAEs (n = 28, 31.8%); those reported in ≥3% of patients were seizure (n = 6), pneumonia (n = 5), acute respiratory failure (n = 3), aspiration pneumonia (n = 3), and dehydration (n = 3). SIGNIFICANCE: Sustained reductions in MMSF at 2 years in the OLE support the efficacy of ganaxolone in seizures associated with CDD. Safety findings in the OLE were consistent with the double-blind phase.

Phase 2, placebo-controlled clinical study of oral ganaxolone in PCDH19-clustering epilepsy.

INTRODUCTION: Protocadherin-19 (PCDH19)-clustering epilepsy is a distinct developmental and epileptic encephalopathy characterized by early-onset seizures that are often treatment refractory. Caused by a mutation of the PCDH19 gene on the X chromosome, this rare epilepsy syndrome primarily affects females with seizure onset commonly in the first year of life. A global, randomized, double-blind, placebo-controlled, phase 2 trial was conducted to evaluate the efficacy, safety, and tolerability of ganaxolone compared with placebo as adjunctive therapy to a standard antiseizure medication regimen in patients with PCDH19-clustering epilepsy (VIOLET; NCT03865732). METHODS: Females aged 1-17 years with a molecularly confirmed pathogenic or likely pathogenic PCDH19 variant who were experiencing ≥12 seizures during a 12-week screening period were stratified by baseline allopregnanolone sulfate (Allo-S) levels (low: ≤2.5 ng/mL; high: >2.5 ng/mL) at screening and randomized 1:1 within each strata to receive ganaxolone (maximum daily dose of 63 mg/kg/day if ≤28 kg or 1800 mg/day if >28 kg) or matching placebo in addition to their standard antiseizure treatment for the 17-week double-blind phase. The primary efficacy endpoint was the median percentage change in 28-day seizure frequency from baseline to the 17-week double-blind phase. Treatment-emergent adverse events (TEAEs) were tabulated by overall, system organ class, and preferred term. RESULTS: Of the 29 patients screened, 21 (median age, 7.0 years; IQR, 5.0-10.0 years) were randomized to receive either ganaxolone (n = 10) or placebo (n = 11). After the 17-week double-blind phase, the median (IQR) percentage change in 28-day seizure frequency from baseline was - 61.5% (-95.9% to -33.4%) among patients in the ganaxolone group and - 24.0% (-88.2% to -4.9%) among patients in the placebo group (Wilcoxon rank-sum test, p = 0.17). TEAEs were reported by 7 of 10 (70.0%) patients in the ganaxolone group and 11 of 11 (100%) patients in the placebo group. Somnolence was the most common TEAE (40.0% ganaxolone vs 27.3% placebo); serious TEAEs were more common in the placebo group (10.0% ganaxolone vs 45.5% placebo); and 1 (10.0%) patient in the ganaxolone group discontinued the study versus none in the placebo group. CONCLUSIONS: Ganaxolone was generally well tolerated and led to a greater reduction in the frequency of PCDH19-clustering seizures compared to placebo; however, the trend did not reach statistical significance. Novel trial designs are likely needed to evaluate the effectiveness of antiseizure treatments for PCDH19-clustering epilepsy.

Safety and efficacy of ganaxolone in patients with CDKL5 deficiency disorder: results from the double-blind phase of a randomised, placebo-controlled, phase 3 trial.

BACKGROUND: CDKL5 deficiency disorder (CDD) is a rare, X-linked, developmental and epileptic encephalopathy characterised by severe global developmental impairment and seizures that can begin in the first few months after birth and are often treatment refractory. Ganaxolone, an investigational neuroactive steroid, reduced seizure frequency in an open-label, phase 2 trial that included patients with CDD. We aimed to further assess the efficacy and safety of ganaxolone in patients with CDD-associated refractory epilepsy. METHODS: In the double-blind phase of this randomised, placebo-controlled, phase 3 trial, done at 39 outpatient clinics in eight countries (Australia, France, Israel, Italy, Poland, Russia, the UK, and the USA), patients were eligible if they were aged 2-21 years with a pathogenic or probably pathogenic CDKL5 variant and at least 16 major motor seizures (defined as bilateral tonic, generalised tonic-clonic, bilateral clonic, atonic, or focal to bilateral tonic-clonic) per 28 days in each 4-week period of an 8-week historical period. After a 6-week prospective baseline period, patients were randomly assigned (1:1) via an interactive web response system to receive either enteral adjunctive ganaxolone or matching enteral adjunctive placebo (maximum dose 63 mg/kg per day for patients weighing ≤28 kg or 1800 mg/day for patients weighing >28 kg) for 17 weeks. Patients, caregivers, investigators (including those analysing data), trial staff, and the sponsor (other than the investigational product manager) were masked to treatment allocation. The primary efficacy endpoint was percentage change in median 28-day major motor seizure frequency from the baseline period to the 17-week double-blind phase and was analysed (using a Wilcoxon-rank sum test) in all patients who received at least one dose of trial treatment and for whom baseline data were available. Safety (compared descriptively across groups) was analysed in all patients who received at least one dose of trial treatment. This study is registered with ClinicalTrials.gov, NCT03572933, and the open-label extension phase is ongoing. FINDINGS: Between June 25, 2018, and July 2, 2020, 114 patients were screened for eligibility, of whom 101 (median age 6 years [IQR 3 to 10]) were randomly assigned to receive either ganaxolone (n=50) or placebo (n=51). All patients received at least one dose of a study drug, but seizure frequency for one patient in the ganaxolone group was not recorded at baseline and so the primary endpoint was analysed in a population of 100 patients. There was a median percentage change in 28-day major motor seizure frequency of -30·7% (IQR -49·5 to -1·9) in the ganaxolone group and of -6·9% (-24·1 to 39·7) in the placebo group (p=0·0036). The Hodges-Lehmann estimate of median difference in responses to ganaxolone versus placebo was -27·1% (95% CI -47·9 to - 9·6). Treatment-emergent adverse events occurred in 43 (86%) of 50 patients in the ganaxolone group and in 45 (88%) of 51 patients in the placebo group. Somnolence, pyrexia, and upper respiratory tract infections occurred in at least 10% of patients in the ganaxolone group and more frequently than in the placebo group. Serious adverse events occurred in six (12%) patients in the ganaxolone group and in five (10%) patients in the placebo group. Two (4%) patients in the ganaxolone group and four (8%) patients in the placebo group discontinued the trial. There were no deaths in the double-blind phase. INTERPRETATION: Ganaxolone significantly reduced the frequency of CDD-associated seizures compared with placebo and was generally well tolerated. Results from what is, to our knowledge, the first controlled trial in CDD suggest a potential treatment benefit for ganaxolone. Long-term treatment is being assessed in the ongoing open-label extension phase of this trial. FUNDING: Marinus Pharmaceuticals.

Influences on the trajectory and subsequent outcomes in CDKL5 deficiency disorder.

OBJECTIVE: The study investigated the effect of seizure and medication burden at initial contact with the International CDKL5 Disorder Database on subsequent development and clinical severity and compared quality of life among those whose development progressed, remained stable, or regressed between baseline and follow-up. METHODS: The effects of seizure and medication burden at baseline (high or low) on the CDKL5 Disorder Severity Scores and CDKL5 Developmental Score (CDS) at follow-up were assessed using linear and negative binomial regressions, respectively, with adjustment for age at baseline, gender, and follow-up duration with and without genotype. Seizure and medication burden were defined by average daily seizure count (high, ≥5/day; low, <5/day) and number of antiseizure medications (high, ≥3/day; low, <3/day), respectively. The effects of change in CDS over time (improved, stable, or deteriorated) on Quality of Life Inventory-Disability (QI-Disability) total and domain scores at follow-up were assessed in those aged at least 3 years at follow-up using linear regression models with adjustment for baseline CDS, gender, and follow-up duration. RESULTS: The expected follow-up CDS was lower for individuals with high compared to low seizure burden at baseline (ß = -.49, 95% confidence interval [CI] = -.84 to -.13). The average total QI-Disability score was 5.6 (95% CI = -.2 to 11.5) points higher among those with improved compared with stable or deteriorating CDS and 8.5 (95% CI = 3.1-13.8) points lower for those with deteriorating compared to stable or improved CDS. SIGNIFICANCE: Our finding that later development showed slight improvement in those with better earlier seizure control even after adjustment for genotype suggests that the trajectory for an individual child is not necessarily predetermined and could possibly be influenced by optimal seizure management. This has implications for children's quality of life.

Natural history of neurological improvement following complete (AIS A) thoracic spinal cord injury across three registries to guide acute clinical trial design and interpretation.

STUDY DESIGN: Retrospective, longitudinal analysis of motor and sensory outcomes following thoracic (T2-T12) sensorimotor complete spinal cord injury (SCI) in selected patients enrolled into three SCI) registries. OBJECTIVES: To establish a modern-day international benchmark for neurological recovery following traumatic complete thoracic sensorimotor SCI in a population similar to those enrolled in acute clinical trials. SETTING: Affiliates of the North American Clinical Trial Network (NACTN), European Multicenter Study about Spinal Cord Injury (EMSCI), and the Spinal Cord Injury Model Systems (SCIMS). METHODS: Only traumatic thoracic injured patients between 2006 and 2016 meeting commonly used clinical trial inclusion/exclusion criteria such as: age 16-70, T2-T12 neurological level of injury (NLI), ASIA Impairment Scale (AIS) A, non-penetrating injury, acute neurological exam within 7 days of injury, and follow-up neurological exam at least ~ 6 months post injury, were included in this analysis. International Standards for Neurological Classification of Spinal Cord injury outcomes including AIS conversion rate, NLI, and sensory and motor scores/levels were compiled. RESULTS: A total of 170 patients were included from the three registries: 12 from NACTN, 64 from EMSCI, and 94 from SCIMS. AIS conversion rates at approximately 6 months post injury varied from 16.7% to 23.4% (21.1% weighted average). Improved conversion rates were observed in all registries for low thoracic (T10-T12) injuries when compared with high/mid thoracic (T2-T9) injuries. The NLI was generally stable and lower extremity motor score (LEMS) improvement was uncommon and usually limited to low thoracic injuries only. CONCLUSIONS: This study presents the aggregation of selected multinational natural history recovery data in thoracic AIS A patients from three SCI registries and demonstrates comparable minimal improvement of ISNCSCI-scored motor and sensory function following these injuries, whereas conversions to higher AIS grades occur at a frequency of ~20%. These data inform the development of future clinical trial protocols in this important patient population for the interpretation of the safety and potential clinical benefit of new therapies, and the potential applicability in a multinational setting. SPONSORSHIP: InVivo Therapeutics.

Method and Apparatus for the Automated Delivery of Continuous Neural Stem Cell Trails Into the Spinal Cord of Small and Large Animals.

BACKGROUND: Immature neurons can extend processes after transplantation in adult animals. Neuronal relays can form between injected neural stem cells (NSCs) and surviving neurons, possibly improving recovery after spinal cord injury (SCI). Cell delivery methods of single or multiple bolus injections of concentrated cell suspensions thus far tested in preclinical and clinical experiments are suboptimal for new tract formation. Nonuniform injectate dispersal is often seen due to gravitational cell settling and clumping. Multiple injections have additive risks of hemorrhage, parenchymal damage, and cellular reflux and require additional surgical exposure. The deposition of multiply delivered cells boluses may be uneven and discontinuous. OBJECTIVE: To develop an injection apparatus and methodology to deliver continuous cellular trails bridging spinal cord lesions. METHODS: We improved the uniformity of cellular trails by formulating NSCs in hyaluronic acid. The TrailmakerTM stereotaxic injection device was automatized to extend a shape memory needle from a single-entry point in the spinal cord longitudinal axis to "pioneer" a new trail space and then retract while depositing an hyaluronic acid-NSC suspension. We conducted testing in a collagen spinal models, and animal testing using human NSCs (hNSCs) in rats and minipigs. RESULTS: Continuous surviving trails of hNSCs within rat and minipig naive spinal cords were 12 and 40 mm in length. hNSC trails were delivered across semi-acute contusion injuries in rats. Transplanted hNSCs survived and were able to differentiate into neural lineage cells and astrocytes. CONCLUSION: The TrailmakerTM creates longitudinal cellular trails spanning multiple levels from a single-entry point. This may enhance the ability of therapeutics to promote functional relays after SCI.

Internal decompression of the acutely contused spinal cord: Differential effects of irrigation only versus biodegradable scaffold implantation.

Severe spinal cord injury leads to hemorrhage, edema and elevated tissue pressures that propagate ischemia. Liquefactive necrosis of damaged tissue eventually results in chronic cavities due to a wound healing process lacking adhesive contractile cells. Biomaterials can potently influence wound healing responses. Internal decompression (ID) refers to pial opening, allowing spontaneous extrusion and irrigation of fluid necrotic debris relieving pressure and resulting in a space for biomaterial scaffold insertion. After thoracic contusions, rats were randomized to: contusion only, contusion + ID and contusion + ID + PLGA-PLL scaffold implantation, to test for neuroprotection and endogenous repair over 3 months. ID alone reduced inflammatory activity, cavity volume, and increased tissue sparing. Scaffold biodegradation produced delayed ingrowth of inflammatory and other cells resulting in endogenously derived laminin-rich tissue, marked reduction in cavitation and presence of tissue remodeling macrophages. Extensive recruitment of Schwann cells into adjacent spared white matter occurred, greatest in scaffold-implanted animals. Despite tissue preservation with myelin repair, no groups differed significantly in open field locomotion. However, across all rats, spared epicenter tissue and locomotor outcomes were correlated. Scaffold-implanted animals showed no obvious toxicity. To study the clinical feasibility, timing and indications for scaffold implantation, Göttingen minipigs underwent ID and were implanted with scaffolds 4, 6, and 24 h after T10 contusion. High intra-spinal tissue pressures fell to pre-injury levels after ID and scaffold implantation. Extrusion of necrotic debris left sufficient space for a sized scaffold. These results provided the preclinical rationale for a current clinical study of biomaterial scaffold implantation into the human injured spinal cord.

Relationship of American Spinal Injury Association Impairment Scale Grade to Post-injury Hospitalization and Costs in Thoracic Spinal Cord Injury.

BACKGROUND: The lifetime economic burden of thoracic spinal cord injury (SCI) is known to be high, but evidence of variability of costs in relation to the American Spinal Injury Association Impairment Scale (AIS) grade is limited. OBJECTIVE: To estimate lifetime economic costs of hospitalization by AIS grade in thoracic SCI. METHODS: Using SCI Model Systems data from January 2000 to March 2016 from the National Spinal Cord Injury Statistical Center, we estimated mean total annual days of all-cause hospitalization by AIS grade among persons with thoracic SCI, based on assessments 1, 5, and 10 yr post-injury. We combined this information with secondary cost data and projections of life expectancy to estimate lifetime economic costs of hospitalization by AIS grade in persons aged 35 yr at time of thoracic SCI. Future costs were discounted to present value at 3% annually. RESULTS: One year post-injury, mean total annual days of hospitalization ranged from 2.1 for persons with AIS-D injuries to 5.9 for those who were AIS-A. Similar differences were noted 5 and 10 yr post-SCI. The estimated net present value of expected lifetime costs of hospitalization following thoracic SCI at age 35 yr was $321 534, $249 514, $188 989, and $68 120 (2015 US$) for AIS-A, AIS-B, AIS-C, and AIS-D injuries, respectively. CONCLUSION: Persons with less severe thoracic SCI, as reflected in AIS grade, spend fewer days in hospital over their lifetimes, leading to lower costs of inpatient care. Therapies improving AIS grade following thoracic SCI may provide cost savings in addition to addressing substantial unmet need.

Sustained Local Release of Methylprednisolone From a Thiol-Acrylate Poly(Ethylene Glycol) Hydrogel for Treating Chronic Compressive Radicular Pain.

STUDY DESIGN: A preclinical animal model of chronic ligation of the sciatic nerve was used to compare the effectiveness of a slow-release hydrogel carrying methylprednisolone to methylprednisolone injection alone, which simulates the current standard of care for chronic compressive radiculopathy (CR). OBJECTIVE: To extend the short-term benefits of steroid injections by using a nonswelling, biodegradable hydrogel as carrier to locally release methylprednisolone in a regulated and sustained way at the site of nerve compression. SUMMARY OF BACKGROUND DATA: CR affects millions worldwide annually, and is a cause of costly disability with significant societal impact. Currently, a leading nonsurgical therapy involves epidural injection of steroids to temporarily alleviate the pain associated with CR. However, an effective way to extend the short-term effect of steroid treatment to address the chronic component of CR does not exist. METHODS: We induced chronic compression injury of the sciatic nerves of rats by permanent ligation. Forty-eight hours later we injected our methylprednisolone infused hydrogel and assessed the effectiveness of our treatment for 4 weeks. We quantified mechanical hyperalgesia using a Dynamic Plantar Aesthesiometer (Ugo Basile, Stoelting Co., IL, USA), whereas gait analysis was conducted using the Catwalk automated gait analysis platform (Noldus, Leesburg, VA, USA). Macrophage staining was performed with immunohistochemistry and quantification of monocyte chemoattractant protein-1 in sciatic nerve lysates was performed with multiplex immunoassay using a SECTOR Imager 2400A (Meso Scale Discovery, Rockville, MA, USA). RESULTS: We demonstrate that using the hydrogel to deliver methylprednisolone results in significant (P < 0.05) reduction of hyperalgesia and improvement in the gait pattern of animals with chronic lesions as compared with animals treated with steroid alone. In addition, animals treated with hydrogel plus steroid showed significant reduction in the number of infiltrating macrophages at the sciatic nerve and reduced expression of the neuroinflammatory chemokine monocyte chemoattractant protein-1 (P < 0.05). CONCLUSION: Use of hydrogels as carriers for sustained local release of steroids provides significantly better control of pain in an animal model of chronic CR. Our steroid-infused hydrogel could be an effective extender of the short-term benefits of epidural steroid injections for patients with chronic compression-induced radicular pain. LEVEL OF EVIDENCE: N/A.

Covalent Incorporation of Trehalose within Hydrogels for Enhanced Long-Term Functional Stability and Controlled Release of Biomacromolecules.

Hydrogels with covalently incorporated trehalose are synthesized using thiol-ene Michael addition. Trehalose hydrogels afford prolonged stabilization and -controlled release of model enzymes in vitro and in vivo as well as preservation of protein stability under heat and -lyophilization stressors. Strong and -ordered hydrogen bonding interactions within covalently incorporated trehalose hydrogels represent a possible mechanism for protein stabilization.

Synthesis and characterization of a library of in-situ curing, nonswelling ethoxylated polyol thiol-ene hydrogels for tailorable macromolecule delivery.

A transesterfication reaction is used to synthesize tri-thiol-functionalized-ethoxylated polyols that are combined with polyethylene glycol diacrylates to form a biodegradable hydrogel library. Hydrogels display nonswelling equilibration and offer temporal control over material degradation and the release of biomolecules. The demonstrated in vitro biocompatibility makes this a versatile platform that can be used for local drug delivery to volume-constrained anatomical sites.

Injectable nano-network for glucose-mediated insulin delivery.

Diabetes mellitus, a disorder of glucose regulation, is a global burden affecting 366 million people across the world. An artificial "closed-loop" system able to mimic pancreas activity and release insulin in response to glucose level changes has the potential to improve patient compliance and health. Herein we develop a glucose-mediated release strategy for the self-regulated delivery of insulin using an injectable and acid-degradable polymeric network. Formed by electrostatic interaction between oppositely charged dextran nanoparticles loaded with insulin and glucose-specific enzymes, the nanocomposite-based porous architecture can be dissociated and subsequently release insulin in a hyperglycemic state through the catalytic conversion of glucose into gluconic acid. In vitro insulin release can be modulated in a pulsatile profile in response to glucose concentrations. In vivo studies validated that these formulations provided improved glucose control in type 1 diabetic mice subcutaneously administered with a degradable nano-network. A single injection of the developed nano-network facilitated stabilization of the blood glucose levels in the normoglycemic state (<200 mg/dL) for up to 10 days.

Synthesis of cyclic, multivalent Arg-Gly-Asp using sequential thiol-ene/thiol-yne photoreactions.

A unique method has been developed for the formation of multivalent cyclic peptides. This procedure exploits on-resin peptide cyclization using a photoinitiated thiol-ene click reaction and subsequent clustering using thiol-yne photochemistry. Both reactions utilize the sulfhydryl group on natural cysteine amino acids to participate in the thiol-mediated reactions.

On-resin peptide macrocyclization using thiol-ene click chemistry.

A versatile and rapid synthetic strategy has been developed for the on-resin cyclization of peptides using thiol-ene photochemistry. This unique method exploits the thiol group of natural cysteine amino acids and allows for various alkenes to be incorporated orthogonal to the peptide backbone.

Regulating MCP-1 diffusion in affinity hydrogels for enhancing immuno-isolation.

Delivering cells using semi-permeable hydrogels is becoming an increasingly important direction in cell based therapies and regenerative medicine applications. Synthetic hydrogels have been functionalized with bioactive motifs to render otherwise inert polymer networks responsive. However, little effort has been focused on creating immuno-isolating materials capable of retarding the transport of small antigenic molecules secreted from the cells delivered with the synthetic carriers. Toward the goal of developing a complete immuno-isolation polymeric barrier, affinity peptide-functionalized PEG hydrogels were developed with the ability to sequester monocyte chemotactic protein 1 (MCP-1), a chemokine known to induce the chemotaxis of monocytes, dendritic cells, and memory T-cells. Affinity peptides capable of sequestering MCP-1 were identified from CCR2 (a G protein-coupled receptor for MCP-1) and incorporated within PEG hydrogels via a thiol-acrylate photopolymerization. The release of encapsulated recombinant MCP-1 from PEG hydrogels is readily tuned by: (1) incorporating affinity peptides within the network; and/or (2) altering the spacer distance between the affinity peptide and the crosslinking site. Furthermore, when pancreatic beta-cells were encapsulated within these novel peptide-functionalized hydrogels, the release of cell-secreted MCP-1 was significantly reduced, demonstrating the potential of this new gel formulation to reduce the host innate immune response to transplanted cells by decreasing the recruitment and activation of host monocytes and other immune cells.

Poly(ethylene glycol) hydrogels formed by thiol-ene photopolymerization for enzyme-responsive protein delivery.

Degradable hydrogels have been extensively used in biomedical applications such as drug delivery, and recent interest has grown in hydrogels that degrade in recognition of a cellular response. This contribution describes a poly(ethylene glycol) (PEG) hydrogel platform with human neutrophil elastase (HNE) sensitive peptide cross-links formed using thiol-ene photopolymerization rendering the gel degradable at sites of inflammation. Further, protein therapeutics can be physically entrapped within the network and selectively released upon exposure to HNE. HNE-responsive hydrogels exhibited surface erosion where the degradation kinetics was influenced by changes in peptide k(cat), concentration of HNE, and concentration of peptide within the gel. Using this platform, we were able to achieve controlled, zero-order release of bovine serum albumin (BSA) in the presence of HNE, and release was arrested in the absence of HNE. To further exploit the advantages of surface eroding delivery systems, a smaller protein (carbonic anhydrase) was delivered at the same rate as BSA and only dependent on gel formulation and environmental conditions. Also, protein release was predicted from a 3-layered hydrogel device using mass loss data. Lastly, the bioactivity of lysozyme was maintained above 90% following the exposure to thiol-ene photopolymerization conditions.

Human neutrophil elastase responsive delivery from poly(ethylene glycol) hydrogels.

A novel enzyme-responsive hydrogel drug delivery system was developed with the potential to treat inflammation locally. Human neutrophil elastase (HNE) is a serine protease secreted by neutrophils which are the first cells recruited to inflammatory sites. We exploited this cell-secreted enzyme as a biological cue for controlled release. HNE sensitive peptide linkers were immobilized within poly(ethylene glycol) hydrogels using photopolymerization techniques. The kinetics of the enzyme reaction within the gel was tailored by varying the amino acid residues present in the P1 and P1' substrate positions (immediately adjacent to cleavage location). A novel FRET-based hydrogel platform was designed to characterize the accessibility of the substrate within the cross-linked, macroscopic hydrogel. Lastly, a diffusion-reaction mathematical model with Michaelis-Menten kinetics was developed to predict the overall release profile and captured the initial 80% of the experimentally observed release. The hydrogel platform presented shows highly controlled release kinetics with potential applications in cellular responsive drug delivery.