Neurophysiological outcomes that sustained clinically significant improvements over 3 years of physiologic ECAP-controlled closed-loop spinal cord stimulation for the treatment of chronic pain.

INTRODUCTION: A novel, spinal cord stimulation (SCS) system with a physiologic closed-loop (CL) feedback mechanism controlled by evoked compound action potentials (ECAPs) enables the optimization of physiologic neural dose and the accuracy of the stimulation, not possible with any other commercially available SCS systems. The report of objective spinal cord measurements is essential to increase the transparency and reproducibility of SCS therapy. Here, we report a cohort of the EVOKE double-blind randomized controlled trial treated with CL-SCS for 36 months to evaluate the ECAP dose and accuracy that sustained the durability of clinical improvements. METHODS: 41 patients randomized to CL-SCS remained in their treatment allocation and were followed up through 36 months. Objective neurophysiological data, including measures of spinal cord activation, were analyzed. Pain relief was assessed by determining the proportion of patients with ≥50% and ≥80% reduction in overall back and leg pain. RESULTS: The performance of the feedback loop resulted in high-dose accuracy by keeping the elicited ECAP within 4µV of the target ECAP set on the system across all timepoints. Percent time stimulating above the ECAP threshold was >98%, and the ECAP dose was ≥19.3µV. Most patients obtained ≥50% reduction (83%) and ≥80% reduction (59%) in overall back and leg pain with a sustained response observed in the rates between 3-month and 36-month follow-up (p=0.083 and p=0.405, respectively). CONCLUSION: The results suggest that a physiological adherence to supra-ECAP threshold therapy that generates pain inhibition provided by ECAP-controlled CL-SCS leads to durable improvements in pain intensity with no evidence of loss of therapeutic effect through 36-month follow-up.

ECAP-controlled closed-loop versus open-loop SCS for the treatment of chronic pain: 36-month results of the EVOKE blinded randomized clinical trial.

INTRODUCTION: The evidence for spinal cord stimulation (SCS) has been criticized for the absence of blinded, parallel randomized controlled trials (RCTs) and limited evaluations of the long-term effects of SCS in RCTs. The aim of this study was to determine whether evoked compound action potential (ECAP)-controlled, closed-loop SCS (CL-SCS) is associated with better outcomes when compared with fixed-output, open-loop SCS (OL-SCS) 36 months following implant. METHODS: The EVOKE study was a multicenter, participant-blinded, investigator-blinded, and outcome assessor-blinded, randomized, controlled, parallel-arm clinical trial that compared ECAP-controlled CL-SCS with fixed-output OL-SCS. Participants with chronic, intractable back and leg pain refractory to conservative therapy were enrolled between January 2017 and February 2018, with follow-up through 36 months. The primary outcome was a reduction of at least 50% in overall back and leg pain. Holistic treatment response, a composite outcome including pain intensity, physical and emotional functioning, sleep, and health-related quality of life, and objective neural activation was also assessed. RESULTS: At 36 months, more CL-SCS than OL-SCS participants reported ≥50% reduction (CL-SCS=77.6%, OL-SCS=49.3%; difference: 28.4%, 95% CI 12.8% to 43.9%, p<0.001) and ≥80% reduction (CL-SCS=49.3%, OL-SCS=31.3%; difference: 17.9, 95% CI 1.6% to 34.2%, p=0.032) in overall back and leg pain intensity. Clinically meaningful improvements from baseline were observed at 36 months in both CL-SCS and OL-SCS groups in all other patient-reported outcomes with greater levels of improvement with CL-SCS. A greater proportion of patients with CL-SCS were holistic treatment responders at 36-month follow-up (44.8% vs 28.4%), with a greater cumulative responder score for CL-SCS patients. Greater neural activation and accuracy were observed with CL-SCS. There were no differences between CL-SCS and OL-SCS groups in adverse events. No explants due to loss of efficacy were observed in the CL-SCS group. CONCLUSION: This long-term evaluation with objective measurement of SCS therapy demonstrated that ECAP-controlled CL-SCS resulted in sustained, durable pain relief and superior holistic treatment response through 36 months. Greater neural activation and increased accuracy of therapy delivery were observed with ECAP-controlled CL-SCS than OL-SCS. TRIAL REGISTRATION NUMBER: NCT02924129.

Durability of Clinical and Quality-of-Life Outcomes of Closed-Loop Spinal Cord Stimulation for Chronic Back and Leg Pain: A Secondary Analysis of the Evoke Randomized Clinical Trial.

Importance: Chronic pain is debilitating and profoundly affects health-related quality of life. Spinal cord stimulation (SCS) is a well-established therapy for chronic pain; however, SCS has been limited by the inability to directly measure the elicited neural response, precluding confirmation of neural activation and continuous therapy. A novel SCS system measures the evoked compound action potentials (ECAPs) to produce a real-time physiological closed-loop control system. Objective: To determine whether ECAP-controlled, closed-loop SCS is associated with better outcomes compared with fixed-output, open-loop SCS at 24 months following implant. Design, Setting, and Participants: The Evoke study was a double-blind, randomized, controlled, parallel arm clinical trial with 36 months of follow-up. Participants were enrolled from February 2017 to 2018, and the study was conducted at 13 US investigation sites. SCS candidates with chronic, intractable back and leg pain refractory to conservative therapy, who consented, were screened. Key eligibility criteria included overall, back, and leg pain visual analog scale score of 60 mm or more; Oswestry Disability Index score of 41 to 80; stable pain medications; and no previous SCS. Analysis took place from October 2020 to April 2021. Interventions: ECAP-controlled, closed-loop SCS was compared with fixed-output, open-loop SCS. Main Outcomes and Measures: Reported here are the 24-month outcomes of the trial, which include all randomized patients in the primary and safety analyses. The primary outcome was a reduction of 50% or more in overall back and leg pain assessed at 3 and 12 months (previously published). Results: Of 134 randomized patients, 65 (48.5%) were female and the mean (SD) age was 55.2 (10.6) years. At 24 months, significantly more closed-loop than open-loop patients were responders (≥50% reduction) in overall pain (53 of 67 [79.1%] in the closed-loop group; 36 of 67 [53.7%] in the open-loop group; difference, 25.4% [95% CI, 10.0%-40.8%]; P = .001). There was no difference in safety profiles between groups (difference in rate of study-related adverse events: 6.0 [95% CI, -7.8 to 19.7]). Improvements were also observed in health-related quality of life, physical and emotional functioning, and sleep, in parallel with opioid reduction or elimination. Objective neurophysiological measurements substantiated the clinical outcomes and provided evidence of activation of inhibitory pain mechanisms. Conclusions and Relevance: ECAP-controlled, closed-loop SCS, which elicited a more consistent neural response, was associated with sustained superior pain relief at 24 months, consistent with the 3- and 12-month outcomes.

Long-term safety and efficacy of closed-loop spinal cord stimulation to treat chronic back and leg pain (Evoke): a double-blind, randomised, controlled trial.

BACKGROUND: Spinal cord stimulation has been an established treatment for chronic back and leg pain for more than 50 years; however, outcomes are variable and unpredictable, and objective evidence of the mechanism of action is needed. A novel spinal cord stimulation system provides the first in vivo, real-time, continuous objective measure of spinal cord activation in response to therapy via recorded evoked compound action potentials (ECAPs) in patients during daily use. These ECAPs are also used to optimise programming and deliver closed-loop spinal cord stimulation by adjusting the stimulation current to maintain activation within patients' therapeutic window. We aimed to examine pain relief and the extent of spinal cord activation with ECAP-controlled closed-loop versus fixed-output, open-loop spinal cord stimulation for the treatment of chronic back and leg pain. METHODS: This multicentre, double-blind, parallel-arm, randomised controlled trial was done at 13 specialist clinics, academic centres, and hospitals in the USA. Patients with chronic, intractable pain of the back and legs (Visual Analog Scale [VAS] pain score ≥60 mm; Oswestry Disability Index [ODI] score 41-80) who were refractory to conservative therapy, on stable pain medications, had no previous experience with spinal cord stimulation, and were appropriate candidates for a spinal cord stimulation trial were screened. Eligible patients were randomly assigned (1:1) to receive ECAP-controlled closed-loop spinal cord stimulation (investigational group) or fixed-output, open-loop spinal cord stimulation (control group). The randomisation sequence was computer generated with permuted blocks of size 4 and 6 and stratified by site. Patients, investigators, and site staff were masked to the treatment assignment. The primary outcome was the proportion of patients with a reduction of 50% or more in overall back and leg pain with no increase in pain medications. Non-inferiority (δ=10%) followed by superiority were tested in the intention-to-treat population at 3 months (primary analysis) and 12 months (additional prespecified analysis) after the permanent implant. This study is registered with ClinicalTrials.gov, NCT02924129, and is ongoing. FINDINGS: Between Feb 21, 2017, and Feb 20, 2018, 134 patients were enrolled and randomly assigned (67 to each treatment group). The intention-to-treat analysis comprised 125 patients at 3 months (62 in the closed-loop group and 63 in the open-loop group) and 118 patients at 12 months (59 in the closed-loop group and 59 in the open-loop group). The primary outcome was achieved in a greater proportion of patients in the closed-loop group than in the open-loop group at 3 months (51 [82·3%] of 62 patients vs 38 [60·3%] of 63 patients; difference 21·9%, 95% CI 6·6-37·3; p=0·0052) and at 12 months (49 [83·1%] of 59 patients vs 36 [61·0%] of 59 patients; difference 22·0%, 6·3-37·7; p=0·0060). We observed no differences in safety profiles between the two groups. The most frequently reported study-related adverse events in both groups were lead migration (nine [7%] patients), implantable pulse generator pocket pain (five [4%]), and muscle spasm or cramp (three [2%]). INTERPRETATION: ECAP-controlled closed-loop stimulation provided significantly greater and more clinically meaningful pain relief up to 12 months than open-loop spinal cord stimulation. Greater spinal cord activation seen in the closed-loop group suggests a mechanistic explanation for the superior results, which aligns with the putative mechanism of action for spinal cord stimulation and warrants further investigation. FUNDING: Saluda Medical.

Novel gemini cationic lipids with carbamate groups for gene delivery.

To obtain efficient non-viral vectors, a series of Gemini cationic lipids with carbamate linkers between headgroups and hydrophobic tails were synthesized. They have the hydrocarbon chains of 12, 14, 16 and 18 carbon atoms as tails, designated as G12, G14, G16 and G18, respectively. These Gemini cationic lipids were prepared into cationic liposomes for the study of the physicochemical properties and gene delivery. The DNA-bonding ability of these Gemini cationic liposomes was much better than their mono-head counterparts (designated as M12, M14, M16 and M18, respectively). In the same series of liposomes, bonding ability declined with an increase in tail length. They were tested for their gene-transferring capabilities in Hep-2 and A549 cells. They showed higher transfection efficiency than their mono-head counterparts and were comparable or superior in transfection efficiency and cytotoxicity to the commercial liposomes, DOTAP and Lipofectamine 2000. Our results convincingly demonstrate that the gene-transferring capabilities of these cationic lipids depended on hydrocarbon chain length. Gene transfection efficiency was maximal at a chain length of 14, as G14 can silence about 80 % of luciferase in A549 cells. Cell uptake results indicate that Gemini lipid delivery systems could be internalised by cells very efficiently. Thus, the Gemini cationic lipids could be used as synthetic non-viral gene delivery carriers for further study.

Targeted transferrin-modified polymeric micelles: enhanced efficacy in vitro and in vivo in ovarian carcinoma.

In this study, transferrin (Tf)-modified poly(ethylene glycol)-phosphatidylethanolamine (mPEG-PE) micelles loaded with the poorly water-soluble drug, R547 (a potent and selective ATP-competitive cyclin-dependent kinase (CDK) inhibitor), were prepared and evaluated for their targeting efficiency and cytotoxicity in vitro and in vivo to A2780 ovarian carcinoma cells, which overexpress transferrin receptors (TfR). At 10 mM lipid concentration, both Tf-modified and plain micelles solubilized 800 µg of R547. Tf-modified micelles showed enhanced interaction with A2780 ovarian carcinoma cells in vitro. The involvement of TfR in endocytosis of Tf-modified micelles was confirmed by colocalization studies of micelle-treated cells with the endosomal marker Tf-Alexa488. We confirmed endocytosis of micelles in an intact form with micelles loaded with a fluorescent dye and additionally labeled with fluorescent lipid. The in vitro cytotoxicity and in vivo tumor growth inhibition studies in A2780-tumor bearing mice confirmed the enhanced efficacy of Tf-modified R547-loaded micelles compared to free drug solution and to nonmodified micelles. The results of this study demonstrate the potential application of Tf-conjugated polymeric micelles in the treatment of tumors overexpressing TfR.

Preparation and characterization of albumin conjugates of a truncated peptide YY analogue for half-life extension.

Recombinant human serum albumin (HSA) conjugates of a 15-amino-acid truncated peptide YY (PYY) analogue were prepared using three heterobifunctional linkers [succinimidyl 4-[N-maleimidomethyl]cyclohexane-1-carboxylate (SMCC), 6-maleimidohexanoic acid N-hydroxysuccinimide ester (MHS), and N-[γ-maleimidobutyryloxy]sulfosuccinimide ester (GMBS)] in 2 synthetic steps involving (1) reaction of succinimidyl ester on linker with ε-amine of Lys2 on the peptide and (2) reaction of maleimide on peptide linker with free thiol of Cysteine 34 (Cys34) on albumin. In-process controls using ESI LC-MS were used to follow reactions and identify reaction products. Proteolytic digests of the conjugate revealed that peptide conjugation occurs at Cys34 on HSA. Conjugates were assayed in cell-based assays to determine potency at the human Y2-receptor, and selectivity at the human Y1-, Y4-, and Y5-receptors using a calcium flux assay. All three conjugates assayed were selective agonists of the Y2-receptor, and displayed nanomolar potencies. MCC and MH conjugates were selected for acute PK/PD studies in DIO mice. Significant reduction in food intake was observed with the MH conjugate, which lasted for 24 h at the 10 mg (or 4 µmol)/kg dose. While the MCC conjugate exhibited greater potency in vitro, it was slightly less effective than the MH conjugate in vivo with respect to reduction in food intake. Both conjugates were significantly less active than the peptide coupled to a 30 kDa PEG. The observed T1/2 (8-9 h) for both conjugates was significantly lower than that observed for the PEGylated peptide (∼25 h). These results suggest that, as compared with the unmodified and PEGylated peptide, the extended circulation half-life of albumin conjugates is mediated through uptake and recirculation by FcRn, and allometric scaling methods are necessary to account for interspecies variation in pharmacokinetic properties.

Structure-activity relationship of carbamate-linked cationic lipids bearing hydroxyethyl headgroup for gene delivery.

A novel series of carbamate-linked cationic lipids containing hydroxyl headgroup were synthesized and included in formulations for transfection assays. The DNA-lipid complexes were characterized for their ability to bind DNA, their size, ζ-potential and cytotoxicity. Compared with our previously reported cationic transfection lipid DDCDMA lacking the hydroxyl group and the commercially available, these cationic liposomes exhibited relatively higher transfection efficiency.

Stapled α-helical peptide drug development: a potent dual inhibitor of MDM2 and MDMX for p53-dependent cancer therapy.

Stapled α-helical peptides have emerged as a promising new modality for a wide range of therapeutic targets. Here, we report a potent and selective dual inhibitor of MDM2 and MDMX, ATSP-7041, which effectively activates the p53 pathway in tumors in vitro and in vivo. Specifically, ATSP-7041 binds both MDM2 and MDMX with nanomolar affinities, shows submicromolar cellular activities in cancer cell lines in the presence of serum, and demonstrates highly specific, on-target mechanism of action. A high resolution (1.7-Å) X-ray crystal structure reveals its molecular interactions with the target protein MDMX, including multiple contacts with key amino acids as well as a role for the hydrocarbon staple itself in target engagement. Most importantly, ATSP-7041 demonstrates robust p53-dependent tumor growth suppression in MDM2/MDMX-overexpressing xenograft cancer models, with a high correlation to on-target pharmacodynamic activity, and possesses favorable pharmacokinetic and tissue distribution properties. Overall, ATSP-7041 demonstrates in vitro and in vivo proof-of-concept that stapled peptides can be developed as therapeutically relevant inhibitors of protein-protein interaction and may offer a viable modality for cancer therapy.

The effect of dual ligand-targeted micelles on the delivery and efficacy of poorly soluble drug for cancer therapy.

We prepared and evaluated transferrin (Tf) and monoclonal antibody (mAb) 2C5-modified dual ligand-targeted poly(ethylene glycol)-phosphatidylethanolamine micelles loaded with a poorly soluble drug, R547 (a selective adenosine triphosphate-competitive cyclin-dependent kinase inhibitor) for enhancement of targeting efficiency and cytotoxicity in vitro and in vivo to A2780 ovarian carcinoma compared to single ligand-targeted micelles. Micellar solubilization significantly improved the solubility of R547 from 1 to 800 µg/mL. The size of modified and non-modified micelles was 13-16 nm. Flow cytometry indicated significantly enhanced cellular association of dual ligand-targeted micelles compared to single ligand-targeted micelles. Confocal microscopy confirmed the Tf receptor-mediated endocytosis of rhodamine-labeled Tf-modified micelles after staining the micelle-treated cells with the endosomal marker Tf-Alexa488. The optimized dual-targeted micelles enhanced cytotoxicity in vitro against A2780 ovarian cancer cells compared to plain and single ligand-targeted micelles. Interestingly, in vivo anti-tumor efficacy was more pronounced for the preparation with a single-targeting ligand (Tf). The specific combination Tf and mAb 2C5 did not yield the expected increase in efficacy as was observed in vitro. This observation suggests that the relationships between targeting ligands in vivo could be more complex than in simplified in vitro systems, and the results of the optimization process should always be verified in vivo.

Synthesis and biological activity of carbamate-linked cationic lipids for gene delivery in vitro.

We have introduced a convenient synthesis method for carbamate-linked cationic lipids. Two cationic lipids N-[1-(2,3-didodecylcarbamoyloxy)propyl]-N,N,N-trimethylammonium iodide (DDCTMA) and N-[1-(2,3-didodecyl carbamoyloxy)propyl]-N-ethyl-N,N-dimethylammonium iodide (DDCEDMA), with identical length of hydrocarbon chains, alternative quaternary ammonium heads, carbamate linkages between hydrocarbon chains and quaternary ammonium heads, were synthesized for liposome-mediated gene delivery. Liposomes composed of DDCEDMA and DOPE in 1:1 ratio exhibited a lower zeta potential as compared to those made of pure DDCEDMA alone, which influences their DNA-binding ability. pGFP-N2 plasmid was transferred by cationic liposomes formed from the above cationic lipids into Hela and Hep-2 cells, and the transfection efficiency of some of cationic liposomes was superior or parallel to that of two commercial transfection agents, Lipofectamine2000 and DOTAP. Combined with the results of the agarose gel electrophoresis and transfection experiment, the DNA-binding ability of cationic lipids was too strong to release DNA from complex in the transfection, which could lead to relative low transfection efficiency and high cytotoxicity.

Development of improved empirical models for estimating the binding constant of a beta-cyclodextrin inclusion complex.

PURPOSE: To develop empirical models for predicting the binding between a drug and beta-cyclodextrin. Specifically, the logarithm of the 1:1 binding constant is expressed as the function of various molecular descriptors of the drug. Many potential drugs exhibit poor aqueous solubility. Also, the amount available for solubility studies is limited early in drug development. Thus, models that show which excipients can increase a drug's solubility are useful because formulation scientists can focus on them experimentally. METHODS: Twenty-five descriptors were considered based on molecular characteristics governing complexation. These include the drug's size and/or shape, the dispersion of its electron cloud, its lipophilicity, and its flexibility. The training set contains 258 ligands, ranging from drug-like molecules to small polar organic compounds. RESULTS: Two models were developed. The first is derived by partial least squares regression and consists of all 25 descriptors. The r2 determined by cross-validation is 0.79. The second contains four variables and was constructed by multiple linear regression. Its cross-validated r2 is 0.65. CONCLUSIONS: Due to its simplicity, the second model is recommended over the first. The most important descriptor in both models is the calculated log P, indicating that drugs with greater lipophilicity form stronger complexes with beta-cyclodextrin.

Practice tip. How I use the internet.

Ms MC, aged 22 years, has come to ask my advice regarding the discontinuation of warfarin after an episode of deep vein thrombosis (DVT) 3 months ago. She is a hockey player and keen to cease her anticoagulant medication, but is concerned about the recurrence of DVT.

Practice tip. Diabetes register and recall.

The majority of general practices now have their patients' details entered on a computer database. These details often include a patient's age, sex, allergies, medications, diagnoses and dates of visits. Accessing this information by the general practitioner can prove useful for a variety of purposes including audits, notifications and research. Most medical software available has the capacity to search a database using specified criteria. The following practice tip is a guide to setting up this search process using the commonly used Medical Director software.