Gastrointestinal challenges in nephropathic cystinosis: clinical perspectives.

Gastrointestinal (GI) sequelae, such as vomiting, hyperacidity, dysphagia, dysmotility, and diarrhea, are nearly universal among patients with nephropathic cystinosis. These complications result from disease processes (e.g., kidney disease, cystine crystal accumulation in the GI tract) and side effects of treatments (e.g., cysteamine, immunosuppressive therapy). GI involvement can negatively impact patient well-being and jeopardize disease outcomes by compromising drug absorption and patient adherence to the strict treatment regimen required to manage cystinosis. Given improved life expectancy due to advances in kidney transplantation and the transformative impact of cystine-depleting therapy, nephrologists are increasingly focused on addressing extra-renal complications and quality of life in patients with cystinosis. However, there is a lack of clinical data and guidance to inform GI-related monitoring, interventions, and referrals by nephrologists. Various publications have examined the prevalence and pathophysiology of selected GI complications in cystinosis, but none have summarized the full picture or provided guidance based on the literature and expert experience. We aim to comprehensively review GI sequelae associated with cystinosis and its treatments and to discuss approaches for monitoring and managing these complications, including the involvement of gastroenterology and other disciplines.

Proposing a Cancer Rehabilitation Medicine Curriculum for Physical Medicine and Rehabilitation Trainees.

ABSTRACT: With the rapid growth and rising interest in the subspecialty of cancer rehabilitation medicine, establishing a structured training and educational curriculum in cancer rehabilitation medicine has become more crucial than ever. For those who are responsible for the educational experiences of students, residents, fellows, or other healthcare professionals, this article provides a systematic approach for establishing a curriculum template relevant for cancer rehabilitation medicine training. This included the assessment of general and targeted needs for learners and educators, rotation goals and objectives, educational strategies, implementation, and evaluation and feedback.

Case study: persistent recovery of hand movement and tactile sensation in peripheral nerve injury using targeted transcutaneous spinal cord stimulation.

Peripheral nerve injury can lead to chronic pain, paralysis, and loss of sensation, severely affecting quality of life. Spinal cord stimulation has been used in the clinic to provide pain relief arising from peripheral nerve injuries, however, its ability to restore function after peripheral nerve injury have not been explored. Neuromodulation of the spinal cord through transcutaneous spinal cord stimulation (tSCS), when paired with activity-based training, has shown promising results towards restoring volitional limb control in people with spinal cord injury. We show, for the first time, the effectiveness of targeted tSCS in restoring strength (407% increase from 1.79 ± 1.24 N to up to 7.3 ± 0.93 N) and significantly increasing hand dexterity in an individual with paralysis due to a peripheral nerve injury (PNI). Furthermore, this is the first study to document a persisting 3-point improvement during clinical assessment of tactile sensation in peripheral injury after receiving 6 weeks of tSCS. Lastly, the motor and sensory gains persisted for several months after stimulation was received, suggesting tSCS may lead to long-lasting benefits, even in PNI. Non-invasive spinal cord stimulation shows tremendous promise as a safe and effective therapeutic approach with broad applications in functional recovery after debilitating injuries.

Targeted transcutaneous spinal cord stimulation promotes persistent recovery of upper limb strength and tactile sensation in spinal cord injury: a pilot study.

Long-term recovery of limb function is a significant unmet need in people with paralysis. Neuromodulation of the spinal cord through epidural stimulation, when paired with intense activity-based training, has shown promising results toward restoring volitional limb control in people with spinal cord injury. Non-invasive neuromodulation of the cervical spinal cord using transcutaneous spinal cord stimulation (tSCS) has shown similar improvements in upper-limb motor control rehabilitation. However, the motor and sensory rehabilitative effects of activating specific cervical spinal segments using tSCS have largely remained unexplored. We show in two individuals with motor-complete SCI that targeted stimulation of the cervical spinal cord resulted in up to a 1,136% increase in exerted force, with weekly activity-based training. Furthermore, this is the first study to document up to a 2-point improvement in clinical assessment of tactile sensation in SCI after receiving tSCS. Lastly, participant gains persisted after a one-month period void of stimulation, suggesting that targeted tSCS may lead to persistent recovery of motor and sensory function.

Experiences and recommendations from people with spinal cord injury following participation in a disability education session at an allopathic medical school: a qualitative study.

BACKGROUND: Students in half of US medical schools do not receive formal instruction in providing medical care for people with disabilities. To address this gap in training, our medical school developed several strategies, including a session for second year medical students to address communication skills, knowledge, and attitudes relevant to delivering healthcare for people with disabilities. Here, our objective was to explore perceptions of people with spinal cord injury (SCI) who participated in the session on its content and structure. METHODS: Qualitative research using a focus group of people with SCI who participated in an educational session for medical students in an LCME accredited allopathic US medical school. A purposive sample of adults with SCI (N = 8) participated in a focus group. Data were analyzed using a six-phase thematic analysis. RESULTS: Participants favorably viewed the educational session, felt their participation was valuable, and had suggestions for its improvement. Four major themes were identified: (1) session format, content; (2) addressing student discomfort and avoidance behaviors; (3) increasing student knowledge and preparation; and (4): important lessons from discussions of past and role-played doctor-patient interactions. CONCLUSIONS: First-person input from people with SCI is critical to improve medical education and healthcare provision to the SCI community. To our knowledge, this is the first study to report feedback from stakeholders providing specific recommendations for teaching disabilities awareness to undergraduate medical students. We expect these recommendations to be relevant to the SCI and medical education communities in improving healthcare for people with SCI and other disabilities.

Nutritional considerations for a new era: A CF foundation position paper.

OBJECTIVE: To provide interim advice and considerations to the CF Community around CF nutrition in the current era. METHODS: The Cystic Fibrosis (CF) Foundation organized a multidisciplinary committee to develop a Nutrition Position Paper based on the rapidly changing nutrition landscape in CF, due in part to widespread use of cystic fibrosis transmembrane regulator highly effective modulator therapy (HEMT). Four workgroups were formed: Weight Management, Eating Behavior/Food Insecurity, Salt Homeostasis and Pancreatic Enzyme use. Each workgroup conducted their own focused review of the literature. RESULTS: The committee summarized current understanding of issues pertaining to the four workgroup topics and provided 6 key take-aways around CF Nutrition in the new era. CONCLUSION: People with CF (pwCF) are living longer, particularly with the advent of HEMT. The traditional high fat, high calorie CF diet may have negative nutritional and cardiovascular consequences as pwCF age. Individuals with CF may have poor diet quality, food insecurity, distorted body image, and an higher incidence of eating disorders. An increase in overweight and obesity may lead to new considerations for nutritional management, given potential effects of overnutrition on pulmonary and cardiometabolic parameters.

Profiling Immunological Phenotypes in Individuals During the First Year After Traumatic Spinal Cord Injury: A Longitudinal Analysis.

Abstract Individuals with SCI are severely affected by immune system changes, resulting in increased risk of infections and persistent systemic inflammation. While recent data support that immunological changes after SCI differ in the acute and chronic phases of living with SCI, only limited immunological phenotyping in humans is available. To characterize dynamic molecular and cellular immune phenotypes over the first year, we assess RNA (bulk-RNA sequencing), protein, and flow cytometry (FACS) profiles of blood samples from 12 individuals with SCI at 0-3 days and at 3, 6, and 12 months post injury (MPI) compared to 23 uninjured individuals (controls). We identified 967 differentially expressed (DE) genes in individuals with SCI (FDR <0.001) compared to controls. Within the first 6 MPI we detected a reduced expression of NK cell genes, consistent with reduced frequencies of CD56bright, CD56dim NK cells present at 12 MPI. Over 6MPI, we observed increased and prolonged expression of genes associated with inflammation (e.g. HMGB1, Toll-like receptor signaling) and expanded frequencies of monocytes acutely. Canonical T-cell related DE genes (e.g. FOXP3, TCF7, CD4) were upregulated during the first 6 MPI and increased frequencies of activated T cells at 3-12 MPI. Neurological injury severity was reflected in distinct whole blood gene expression profiles at any time after SCI, verifying a persistent 'neurogenic' imprint. Overall, 2876 DE genes emerge when comparing motor complete to motor incomplete SCI (ANOVA, FDR <0.05), including those related to neutrophils, inflammation, and infection. In summary, we identify a dynamic immunological phenotype in humans, including molecular and cellular changes which may provide potential targets to reduce inflammation, improve immunity, or serve as candidate biomarkers of injury severity.

Sirtuin 5 levels are limiting in preserving cardiac function and suppressing fibrosis in response to pressure overload.

Heart failure (HF) is the inability of the heart to pump blood sufficiently to meet the metabolic demands of the body. HF with reduced systolic function is characterized by cardiac hypertrophy, ventricular fibrosis and remodeling, and decreased cardiac contractility, leading to cardiac functional impairment and death. Transverse aortic constriction (TAC) is a well-established model for inducing hypertrophy and HF in rodents. Mice globally deficient in sirtuin 5 (SIRT5), a NAD+-dependent deacylase, are hypersensitive to cardiac stress and display increased mortality after TAC. Prior studies assessing SIRT5 functions in the heart have all employed loss-of-function approaches. In this study, we generated SIRT5 overexpressing (SIRT5OE) mice, and evaluated their response to chronic pressure overload using TAC. Compared to littermate controls, SIRT5OE mice were protected against adverse functional consequences of TAC, left ventricular dilation and impaired ejection fraction. Transcriptomic analysis revealed that SIRT5 suppresses key HF sequelae, including the metabolic switch from fatty acid oxidation to glycolysis, immune activation, and fibrotic signaling pathways. We conclude that SIRT5 is a limiting factor in the preservation of cardiac function in response to experimental pressure overload.

Elevated levels of IgA and IgG2 in individuals with chronic spinal cord injury.

OBJECTIVES: To determine circulating levels of antibodies (IgA, IgM, IgG1-4) in individuals with SCI as compared to uninjured individuals. STUDY DESIGN: Prospective, observational study. SETTING: Outpatient clinic of a Department of Physical Medicine and Rehabilitation and research institute in an academic medical center. PARTICIPANTS: Individuals with chronic (≥ 1 year from injury) SCI and uninjured individuals. OUTCOME MEASURES: Serum antibody titers were determined by commercial multiplex ELISA. RESULTS: Blood samples were collected from individuals with chronic SCI (N = 29, 83% males) and uninjured individuals (N = 25, 64% males). Among participants with SCI, the distribution of American Spinal Injury Association Impairment Scale (AIS) grades was: A (n = 15), B (n = 2), C (n = 4), D (n = 8). Neurological levels of injury were: cervical (n = 17), thoracic (n = 10), and lumbar (n = 2). IgA levels were significantly elevated in participants with SCI compared to uninjured participants (median: 1.98 vs. 1.21 mg/ml, P < 0.0001), with levels most elevated in individuals with motor complete injuries compared to uninjured participants (P < 0.0003). IgG2 antibodies were also significantly elevated in participants with SCI compared to uninjured participants (median: 5.98 vs. 4.37 mg/ml, P < 0.018). CONCLUSIONS: To our knowledge, this study provides the first evidence of elevated IgA, the antibody type most prevalent at respiratory, genitourinary and gastrointestinal tracts, common sites of infections in individuals with SCI. IgG2 levels were also elevated in individuals with SCI. These data support further investigations of IgA and other antibody types in individuals with chronic SCI, which may be increasingly important in the context of emerging novel infectious diseases such as SARS-CoV-2.

Low-dose Methotrexate Therapy Does Not Affect Semen Parameters and Sperm DNA.

BACKGROUND: Methotrexate is widely used in inflammatory diseases during the patients' reproductive years. The effect on male fertility and sperm DNA integrity is largely unknown. We evaluated sperm DNA integrity and basic semen parameters according to the World Health Organization (WHO) in male patients with inflammatory diseases treated with methotrexate. METHODS: Semen samples from 14 patients on low-dose maintenance methotrexate were compared with samples from 40 healthy volunteers. Further, 5 patients delivered samples on and off methotrexate therapy for paired comparison. Sperm DNA fragmentation index (DFI), concentration, motility, and morphology were evaluated. Blood sex hormones and methotrexate levels were measured in blood and semen. RESULTS: DNA fragmentation index in methotrexate-treated patients was comparable with that in healthy volunteers (DFI, 11.5 vs 15.0; P = .06), and DFI did not change significantly on and off methotrexate in the paired samples (DFI, 12.0 vs 14.0; P = 0.35). Sperm concentration, motility, and morphology did not differ between men treated with methotrexate and healthy volunteers. Sperm progressive motility increased off therapy compared with on therapy (65.0% vs 45.0%, P = .04), but all fluctuations in progressive motility were within the WHO reference interval. All methotrexate polyglutamates1-5 were detected in blood, but only methotrexate polyglutamate1 in semen. Serum testosterone was unaffected by methotrexate therapy. CONCLUSIONS: Patients treated with low-dose methotrexate have a sperm quality comparable with that of healthy volunteers, and methotrexate treatment does not increase sperm DNA fragmentation. This study does not support cryopreservation of semen before treatment initiation nor a 3-month methotrexate-free interval prior to conception.

Challenges and Lessons Learned for Acute Inpatient Rehabilitation of Persons With COVID-19: Clinical Presentation, Assessment, Needs, and Services Utilization.

OBJECTIVE: The aim of the study was to present: (1) physiatric care delivery amid the SARS-CoV-2 pandemic, (2) challenges, (3) data from the first cohort of post-COVID-19 inpatient rehabilitation facility patients, and (4) lessons learned by a research consortium of New York and New Jersey rehabilitation institutions. DESIGN: For this clinical descriptive retrospective study, data were extracted from post-COVID-19 patient records treated at a research consortium of New York and New Jersey rehabilitation inpatient rehabilitation facilities (May 1-June 30, 2020) to characterize admission criteria, physical space, precautions, bed numbers, staffing, employee wellness, leadership, and family communication. For comparison, data from the Uniform Data System and eRehabData databases were analyzed. The research consortium of New York and New Jersey rehabilitation members discussed experiences and lessons learned. RESULTS: The COVID-19 patients (N = 320) were treated during the study period. Most patients were male, average age of 61.9 yrs, and 40.9% were White. The average acute care length of stay before inpatient rehabilitation facility admission was 24.5 days; mean length of stay at inpatient rehabilitation facilities was 15.2 days. The rehabilitation research consortium of New York and New Jersey rehabilitation institutions reported a greater proportion of COVID-19 patients discharged to home compared with prepandemic data. Some institutions reported higher changes in functional scores during rehabilitation admission, compared with prepandemic data. CONCLUSIONS: The COVID-19 pandemic acutely affected patient care and overall institutional operations. The research consortium of New York and New Jersey rehabilitation institutions responded dynamically to bed expansions/contractions, staff deployment, and innovations that facilitated safe and effective patient care.

Systemic gene expression profiles according to pain types in individuals with chronic spinal cord injury.

Pain affects most individuals with traumatic spinal cord injury (SCI). Major pain types after SCI are neuropathic or nociceptive, often experienced concurrently. Pain after SCI may be refractory to treatments and negatively affects quality of life. Previously, we analyzed whole blood gene expression in individuals with chronic SCI compared to able-bodied (AB) individuals. Most participants with SCI reported pain (N = 19/28). Here, we examined gene expression of participants with SCI by pain status. Compared to AB, participants with SCI with pain had 468 differentially expressed (DE) genes; participants without pain had 564 DE genes (FDR < 0.05). Among DE genes distinct to participants with SCI with pain, Gene Ontology Biological Process (GOBP) analysis showed upregulated genes were enriched in categories related to T cell activation or inflammation; downregulated genes were enriched in categories related to protein proteolysis and catabolism. Although most participants with pain reported multiple pain types concurrently, we performed a preliminary comparison of gene expression by worst pain problem type. Compared to AB, participants with SCI who ranked neuropathic (N = 9) as worst had one distinct DE gene (TMEM156); participants who ranked nociceptive (N = 10) as worst had 61 distinct DE genes (FDR < 0.05). In the nociceptive group, the GOBP category with the lowest P-value identified among upregulated genes was "positive regulation of T cell activation"; among downregulated genes it was "receptor tyrosine kinase binding". An exploratory comparison of pain groups by principal components analysis also showed that the nociceptive group was enriched in T-cell related genes. A correlation analysis identified genes significantly correlated with pain intensity in the neuropathic or nociceptive groups (N = 145, 65, respectively, Pearson's correlation r > 0.8). While this pilot study highlights challenges of identifying gene expression profiles that correlate with specific types of pain in individuals with SCI, it suggests that T-cell signaling should be further investigated in this context.

Vedolizumab Concentrations in Breast Milk: Results from a Prospective, Postmarketing, Milk-Only Lactation Study in Nursing Mothers with Inflammatory Bowel Disease.

BACKGROUND AND OBJECTIVES: The safety of inflammatory bowel disease medications during lactation is of significant relevance to women of childbearing potential. Available data regarding the transfer of biologic agents for inflammatory bowel disease via breast milk are limited to case reports. The objective of this prospective postmarketing lactation study was to assess vedolizumab concentrations in breast milk from lactating vedolizumab-treated women with inflammatory bowel disease. METHODS: Breast milk was serially collected throughout the dosing interval from 11 patients receiving established intravenous vedolizumab 300-mg maintenance therapy every 8, 6, or 4 weeks. Maternal safety was also assessed. RESULTS: Vedolizumab was detectable in ~90% of milk samples collected from all patients. Following the day 1 dose, vedolizumab milk concentrations increased with a median of 3-4 days to peak concentration, and subsequently decreased exponentially. For the nine patients receiving vedolizumab every 8 weeks, the average relative infant dose was 20.9%. Using a mean trough serum concentration of 11.2 µg/mL from historical studies, the ratio of mean vedolizumab milk-to-serum concentration was ~ 0.4 to 2.2%, consistent with published data on vedolizumab and other monoclonal antibody therapeutics for inflammatory bowel disease. The maternal safety profile was similar to that observed in previous vedolizumab studies. Published vedolizumab studies also showed no adverse findings for infants breastfed by vedolizumab-treated mothers. CONCLUSIONS: Vedolizumab was present in human breast milk at a low level. The decision to use vedolizumab should balance the benefit of therapy to the mother and the potential risks to the infant. TRIAL REGISTRATION: ClinicalTrials.gov, NCT02559713; registered 24 September, 2015.

Hydrogen Bonding Site Number Predicts Dicamba Volatilization from Amine Salts.

Amine-based formulations are widely used to decrease volatilization of carboxylic acid-containing herbicides including dicamba. Despite our reliance on these formulations, the underlying amine properties that determine their ability to control herbicide volatilization are poorly understood. In this study, we measured dicamba volatilization from solid (BAMPA) on glass as with dimethylamine (DMA), diglycolamine (DGA), and N,N-bis(3-aminopropyl)methylamine (BAPMA) as a function of temperature and amine-to-dicamba ratio, as well as in the presence of glyphosate. In all cases, we found that BAPMA had a greater ability to lessen dicamba volatilization than DMA or DGA. Even when only 1 BAPMA molecule was present for every 10 dicamba molecules, dicamba volatilization was still decreased by 70% relative to the free acid case. The particular ability for BAPMA to control dicamba volatilization could be attributed to several molecular features (i.e., molecular weight, type and number of amine functional groups). Using a set including 5 additional amines, we determined that dicamba volatilization is primarily influenced by the number of functional groups in the amine that can participate in hydrogen bonding. From these results, we propose that ability of an amine to form multiple intermolecular interactions (i.e., hydrogen bonds) in the residue may best predict their potential to prevent herbicide volatilization.

Determining grasp selection from arm trajectories via deep learning to enable functional hand movement in tetraplegia.

BACKGROUND: Cervical spinal cord injury severely affects grasping ability of its survivors. Fortunately, many individuals with tetraplegia retain residual arm movements that allow them to reach for objects. We propose a wearable technology that utilizes arm movement trajectory information and deep learning methods to determine grasp selection. Furthermore, we combined this approach with neuromuscular stimulation to determine if self-driven functional hand movement could be enabled in spinal cord injury participants. METHODS: Two cervical SCI participants performed arbitrary and natural reaching movements toward target objects in three-dimensional space, which were recorded using an inertial sensor worn on their wrist. Time series classifiers were trained to recognize the trajectories using either a Dynamic Time Warping (DTW) algorithm or a Long Short-Term Memory (LSTM) recurrent neural network. As an initial proof-of-concept, we demonstrate real-time classification of the arbitrary movements using DTW only (due to its implementation simplicity), which when used in combination with a high density neuromuscular stimulation sleeve with textile electrodes, enabled participants to perform functional grasping. RESULTS: Participants were able to consistently perform arbitrary two-dimensional and three-dimensional arm movements which could be classified with high accuracy. Furthermore, it was found that natural reaching trajectories for two different target objects (requiring two different grasp types) were distinct and also discriminable with high accuracy. In offline comparisons, LSTM (mean accuracies 99%) performed significantly better than DTW (mean accuracies 86 and 83%) for both arbitrary and natural reaching movements, respectively. Type I and II errors occurred more frequently for DTW (up to 60 and 15%, respectively), whereas it stayed under 5% for LSTM. Also, DTW achieved online accuracy of 79%. CONCLUSIONS: We demonstrate the feasibility of utilizing arm trajectory information to determine grasp selection using a wearable inertial sensor along with DTW and deep learning methods. Importantly, this technology can be successfully used to control neuromuscular stimulation and restore functional independence to individuals living with paralysis. TRIAL REGISTRATION: NCT, NCT03385005. Registered September 26, 2017.

Improved homology modeling of the human & rat EP4 prostanoid receptors.

BACKGROUND: The EP4 prostanoid receptor is one of four GPCRs that mediate the diverse actions of prostaglandin E2 (PGE2). Novel selective EP4 receptor agonists would assist to further elucidate receptor sub-type function and promote development of therapeutics for bone healing, heart failure, and other receptor associated conditions. The rat EP4 (rEP4) receptor has been used as a surrogate for the human EP4 (hEP4) receptor in multiple SAR studies. To better understand the validity of this traditional approach, homology models were generated by threading for both receptors using the RaptorX server. These models were fit to an implicit membrane using the PPM server and OPM database with refinement of intra and extracellular loops by Prime (Schrödinger). To understand the interaction between the receptors and known agonists, induced-fit docking experiments were performed using Glide and Prime (Schrödinger), with both endogenous agonists and receptor sub-type selective, small-molecule agonists. The docking scores and observed interactions were compared with radioligand displacement experiments and receptor (rat & human) activation assays monitoring cAMP. RESULTS: Rank-ordering of in silico compound docking scores aligned well with in vitro activity assay EC50 and radioligand binding Ki. We observed variations between rat and human EP4 binding pockets that have implications in future small-molecule receptor-modulator design and SAR, specifically a S103G mutation within the rEP4 receptor. Additionally, these models helped identify key interactions between the EP4 receptor and ligands including PGE2 and several known sub-type selective agonists while serving as a marked improvement over the previously reported models. CONCLUSIONS: This work has generated a set of novel homology models of the rEP4 and hEP4 receptors. The homology models provide an improvement upon the previously reported model, largely due to improved solvation. The hEP4 docking scores correlates best with the cAMP activation data, where both data sets rank order Rivenprost>CAY10684 > PGE1 ≈ PGE2 > 11-deoxy-PGE1 ≈ 11-dexoy-PGE2 > 8-aza-11-deoxy-PGE1. This rank-ordering matches closely with the rEP4 receptor as well. Species-specific differences were noted for the weak agonists Sulprostone and Misoprostol, which appear to dock more readily within human receptor versus rat receptor.

Optimization of LpxC Inhibitors for Antibacterial Activity and Cardiovascular Safety.

UDP-3-O-(R-3-hydroxymyristoyl)-N-acetylglucosamine deacetylase (LpxC) is a Zn2+ deacetylase that is essential for the survival of most pathogenic Gram-negative bacteria. ACHN-975 (N-((S)-3-amino-1-(hydroxyamino)-3-methyl-1-oxobutan-2-yl)-4-(((1R,2R)-2-(hydroxymethyl)cyclopropyl)buta-1,3-diyn-1-yl)benzamide) was the first LpxC inhibitor to reach human clinical testing and was discovered to have a dose-limiting cardiovascular toxicity of transient hypotension without compensatory tachycardia. Herein we report the effort beyond ACHN-975 to discover LpxC inhibitors optimized for enzyme potency, antibacterial activity, pharmacokinetics, and cardiovascular safety. Based on its overall profile, compound 26 (LPXC-516, (S)-N-(2-(hydroxyamino)-1-(3-methoxy-1,1-dioxidothietan-3-yl)-2-oxoethyl)-4-(6-hydroxyhexa-1,3-diyn-1-yl)benzamide) was chosen for further development. A phosphate prodrug of 26 was developed that provided a solubility of >30 mg mL-1 for parenteral administration and conversion into the active drug with a t1/2 of approximately two minutes. Unexpectedly, and despite our optimization efforts, the prodrug of 26 still possesses a therapeutic window insufficient to support further clinical development.