Cost-effectiveness of the addition of CDK4/6 inhibitors to standard endocrine therapy in first-line treatment of women with advanced HR+/HER2− breast cancer in Mexico

Purpose To estimate the cost-effectiveness of adding a CDK4/6 inhibitor to standard endocrine therapy in the first-line setting for advanced HR+/HER2− breast cancer in postmenopausal and premenopausal women, from the perspective of the Mexican public healthcare system. Methods We used a partitioned survival model to simulate relevant health outcomes in a synthetic cohort of patients with breast cancer derived from the PALOMA-2, MONALEESA-2, MONARCH-3 trials for postmenopausal patients, and from the MONALEESA-7 study for premenopausal patients. Effectiveness was measured in life years gained. Cost-effectiveness is reported through incremental cost-effectiveness ratios (ICER). Results In postmenopausal patients, palbociclib led to an increase of 1.51 life years, ribociclib of 1.58 years, and abemaciclib of 1.75 years, compared to letrozole alone. The ICER was 36,648 USD, 32,422 USD, and 26,888 USD, respectively. In premenopausal patients, ribociclib led to an increase of 1.82 life years when added to goserelin and endocrine therapy, with an ICER of 44,579 USD. In the cost minimization analysis, for postmenopausal patients, ribociclib was the treatment with the highest costs due to follow-up requirements. Conclusion Palbociclib, ribociclib, and abemaciclib demonstrated a significant increase in effectiveness in postmenopausal patients, and ribociclib in premenopausal patients, when added to standard endocrine therapy for patients with advanced HR+/HER2− breast cancer. At the national stablished willingness to pay, only the addition of abemaciclib to standard endocrine therapy in postmenopausal women would be considered cost-effective. However, differences on results between therapies for postmenopausal patients were not statistically significant (AU)

Altering neuronal circuitry with 4-aminopyridine for visual improvement in Leber's hereditary optic neuropathy (LHON).

In this retrospective, interventional, longitudinal small case series, we looked at the visual effects of pharmacologic intervention with 4-aminopyridine (4-AP) in chronic Leber's Hereditary Optic Neuropathy (LHON) patients who are non-responders to idebenone. We illustrate, as examples, the visual progression of three LHON patients with 4-AP as add-on therapy to idebenone. Each patient had a different primary LHON mutation and was treated with idebenone within one year of onset. No response to idebenone at 300 mg orally three times a day ranged from less than one year to 2.5 years, and the addition of 4-AP at 10 mg orally two times a day ranged from 24 to 29 months. Outcome measures included best-corrected distance visual acuity, color vision, automated perimetry, the average retinal nerve fiber layer (RNFL) thickness, and the full-field photopic negative response (PhNR) amplitude. The 19-year-old man with the LHON mutation 11778A > G had no response to the addition of 4-AP to idebenone. The 27-year-old man with the LHON mutation 3460A > G experienced a significant response to 4-AP. Finally, the 40-year-old man with the LHON mutation 14484 T > C had a milder response. Although this case series was too small to demonstrate the efficacy of idebenone with add-on 4AP, it allowed us to consider a new hypothesis that neuronal activity generated from 4-AP can add more potential for visual recovery in LHON patients.

Safety, Patient-Reported Well-Being, and Physician-Reported Assessment of Walking Ability in Patients with Multiple Sclerosis for Prolonged-Release Fampridine Treatment in Routine Clinical Practice: Results of the LIBERATE Study.

BACKGROUND: Prolonged-release fampridine (PR-FAM) 10-mg tablet twice daily is the only approved pharmacological treatment for improvement of walking ability in adults with multiple sclerosis (MS). LIBERATE assessed the safety/effectiveness of PR-FAM in the real-world. OBJECTIVES: The aim of this study was to collect additional safety data, including the incidence rate of seizures and other adverse events (AEs) of interest, from patients with MS taking PR-FAM in routine clinical practice (including patients aged ≥ 65 years and those with pre-existing cardiovascular risk factors). Other objectives included change over time in patient-reported evaluation of physical and psychological impact of MS while taking PR-FAM, and change over time in physician-reported assessment of walking ability in MS patients taking PR-FAM. METHODS: Patients with MS newly prescribed PR-FAM were recruited (201 sites, 13 countries). Demographic/safety data were collected at enrolment through 12 months. Physician-rated Clinical Global Impression of Improvement (CGI-I) scores for walking ability, and Multiple Sclerosis Impact Scale-29 (MSIS-29) were assessed. RESULTS: Safety analysis included 4646 patients with 3534.8 patient-years of exposure; median (range) age, 52.6 (21-85) years, 87.3% < 65 years, and 65.7% women. Treatment-emergent AEs (TEAEs) were reported in 2448 (52.7%) patients, and serious TEAEs were reported in 279 (6.0%) patients, of whom 37 (< 1%) experienced treatment-emergent serious AEs (TESAEs) considered related to PR-FAM. AEs of special interest (AESI) occurred in 1799 (38.7%) patients, and serious AESI in 128 (2.8%) patients. Seventeen (< 1%) patients experienced actual events of seizure. Overall, 1158 (24.9%) patients discontinued treatment due to lack of efficacy. At 12 months, a greater proportion of patients on-treatment had improvement from baseline in CGI-I for walking ability versus those who discontinued (61% vs. 11%; p <  0.001). MSIS-29 physical impact score improved significantly for patients on-treatment for 12 months versus those who discontinued (mean change, baseline to 12 months: - 9.99 vs. - 0.34 points; p <  0.001). Results were similar for MSIS-29 psychological impact. CONCLUSION: No new safety concerns were identified in this real-world study, suggesting that routine risk-minimization measures are effective. CGI-I and MSIS-29 scores after 12 months treatment with PR-FAM treatment show clinical benefits consistent with those previously reported. TRIAL REGISTRATION: ClinicalTrials.gov: NCT01480063.

(4-Aminopyridine)-PLGA-PEG as a Novel Thermosensitive and Locally Injectable Treatment for Acute Peripheral Nerve Injury.

Traumatic peripheral nerve injury (TPNI) represents a major medical problem that results in loss of motor and sensory function, and in severe cases, limb paralysis and amputation. To date, there are no effective treatments beyond surgery in selective cases. In repurposing studies, we found that daily systemic administration of the FDA-approved drug 4-aminopyridine (4-AP) enhanced functional recovery after acute peripheral nerve injury. This study was aimed at constructing a novel local delivery system of 4-AP using thermogelling polymers. We optimized a thermosensitive (4-AP)-poly(lactide-co-glycolide)-b-poly(ethylene glycol)-b-poly(lactide-co-glycolide) (PLGA-PEG-PLGA) block copolymer formulation. (4-AP)-PLGA-PEG exhibited controlled release of 4-AP both in vitro and in vivo for approximately 3 weeks, with clinically relevant safe serum levels in animals. Rheological investigation showed that (4-AP)-PLGA-PEG underwent a solution to gel transition at 32 °C, a physiologically relevant temperature, allowing us to administer it to an injured limb while subsequently forming an in situ gel. A single local administration of (4-AP)-PLGA-PEG remarkably enhanced motor and sensory functional recovery on post-sciatic nerve crush injury days 1, 3, 7, 14, and 21. Moreover, immunohistochemical studies of injured nerves treated with (4-AP)-PLGA-PEG demonstrated an increased expression of neurofilament heavy chain (NF-H) and myelin protein zero (MPZ) proteins, two major markers of nerve regeneration. These findings demonstrate that (4-AP)-PLGA-PEG may be a promising long-acting local therapeutic agent in TPNI, for which no pharmacologic treatment exists.

Bursting in cerebellar stellate cells induced by pharmacological agents: Non-sequential spike adding.

Cerebellar stellate cells (CSCs) are spontaneously active, tonically firing (5-30 Hz), inhibitory interneurons that synapse onto Purkinje cells. We previously analyzed the excitability properties of CSCs, focusing on four key features: type I excitability, non-monotonic first-spike latency, switching in responsiveness and runup (i.e., temporal increase in excitability during whole-cell configuration). In this study, we extend this analysis by using whole-cell configuration to show that these neurons can also burst when treated with certain pharmacological agents separately or jointly. Indeed, treatment with 4-Aminopyridine (4-AP), a partial blocker of delayed rectifier and A-type K+ channels, at low doses induces a bursting profile in CSCs significantly different than that produced at high doses or when it is applied at low doses but with cadmium (Cd2+), a blocker of high voltage-activated (HVA) Ca2+ channels. By expanding a previously revised Hodgkin-Huxley type model, through the inclusion of Ca2+-activated K+ (K(Ca)) and HVA currents, we explain how these bursts are generated and what their underlying dynamics are. Specifically, we demonstrate that the expanded model preserves the four excitability features of CSCs, as well as captures their bursting patterns induced by 4-AP and Cd2+. Model investigation reveals that 4-AP is potentiating HVA, inducing square-wave bursting at low doses and pseudo-plateau bursting at high doses, whereas Cd2+ is potentiating K(Ca), inducing pseudo-plateau bursting when applied in combination with low doses of 4-AP. Using bifurcation analysis, we show that spike adding in square-wave bursts is non-sequential when gradually changing HVA and K(Ca) maximum conductances, delayed Hopf is responsible for generating the plateau segment within the active phase of pseudo-plateau bursts, and bursting can become "chaotic" when HVA and K(Ca) maximum conductances are made low and high, respectively. These results highlight the secondary effects of the drugs applied and suggest that CSCs have all the ingredients needed for bursting.

Checkpoint kinase­1 inhibition and etoposide exhibit a strong synergistic anticancer effect on chronic myeloid leukemia cell line K562 by impairing homologous recombination DNA damage repair.

Leukemia, a malignant hematological disease, has poor therapeutic outcomes due to chemotherapeutic resistance. Increasing evidence has confirmed that the elevated capacity for DNA damage repair in cancer cells is a major mechanism of acquired chemotherapeutic resistance. Thus, combining chemotherapy with inhibitors of DNA damage repair pathways is potentially an ideal strategy for treating leukemia. Checkpoint kinase 1 (CHK1) is an important component of the DNA damage response (DDR) and is involved in the G2/M DNA damage checkpoint. In the present study, we demonstrated that shRNA­mediated CHK1 silencing suppressed cell proliferation and enhanced the cytotoxic effects of etoposide (VP16) in the chronic myeloid leukemia (CML) cell line K562 through the results of CCK­8, and comet assay. The results demonstrated that shRNA­induced CHK1 silencing can override G2/M arrest and impair homologous recombination (HR) repair by reducing breast cancer susceptibility gene 1 (BRCA1) expression. Cells had no time, and thus limited ability, to repair the damage and were thus more sensitive to chemotherapy after CHK1 downregulation. Second, we tested the therapeutic effect of VP16 combined with CCT245737, an orally bioavailable CHK1 inhibitor, and observed strong synergistic anticancer effects in K562 cells. Moreover, we discovered that CCT245737 significantly prevented the G2/M arrest caused by acute exposure to VP16. Interestingly, CCT245737 inhibited both BRCA1 and Rad51, the most important component of the HR repair pathway. In conclusion, these results revealed that CHK1 is potentially an ideal therapeutic target for the treatment of CML and that CCT245737 should be considered a candidate drug.

A double-blind, randomized, controlled study of two dose strengths of dalfampridine extended release on walking deficits in ischemic stroke.

BACKGROUND: Stroke-induced ischemia affects both cortex and underlying white matter. Dalfampridine extended release tablets (D-ER) enhance action potential conduction in demyelinated axons, which may positively affect post-stroke recovery. OBJECTIVE: Based on promising preliminary data, we compared efficacy of D-ER administered at 7.5 mg or 10 mg with placebo on post-stroke ambulation. Primary study outcome (response) was a ≥20% increase on the 2-minute walk test (2 MinWT) at 12 weeks after first drug administration. METHODS: This was a multicenter, randomized, placebo-controlled, 3-arm, parallel-group, safety and efficacy trial. After obtaining baseline measures of 2 MinWT, Walk-12, and Timed Up and Go, subjects entered a 2-week, single-blind placebo run-in period and were randomized 1:1:1 to receive 7.5 mg D-ER, 10 mg D-ER, or placebo, dosed twice-daily for 12 weeks. Follow-up evaluations occurred at weeks 14 and 16 when subjects were off study drug. RESULTS: The study was terminated early with 377 of planned 540 patients enrolled, due to no treatment effect. At week 12, mean increase in distances walked in 2 minutes were similar among the 3 study groups (14.9±40.0 feet; 19.4±39.6 feet; and 20.4±38.3 feet for placebo, 7.5 mg D-ER, and 10 mg D-ER, respectively). The proportion of subjects who showed ≥20% improvement on 2 MinWT at week 12 was 13.5%, 14.0%, and 19.0%, for placebo, 7.5 mg D-ER, and 10 mg D-ER, respectively; these were nonsignificant changes from baseline for all groups. CONCLUSIONS: D-ER at either a 7.5-mg or 10-mg dose did not significantly increase performance on the 2 MinWT in stroke survivors with gait impairment, although this study was terminated early before full enrollment. (Clinical Trial # NCT02271217).

Effects of modified-release fampridine on upper limb impairment in patients with Multiple Sclerosis.

BACKGROUND: Modified-release 4-aminopyridine (fampridine-MR) is used in the symptomatic treatment of walking disability in patients with multiple sclerosis (MS).  Its potential for use in other MS symptoms remains unproven and its mode of action in this context is uncertain. Interest is growing in the use of upper limb outcome measures in clinical trials in patients with Multiple Sclerosis, particularly in advanced or progressive disease.  This study tests the following hypotheses: (1) Fampridine-MR improves upper limb function in patients with MS and upper limb impairment.  (2) Treatment with fampridine-MR is associated with measurable alterations in objective electrophysiological parameters (evoked potentials and transcranial magnetic stimulation (TMS)) which may predict response to drug treatment. METHODS: Study population: patients with MS of any disease subtype, duration and severity who have symptomatic impairment of one or both upper limbs.  A healthy control group was included for validation of clinical and electrophysiological measures.  Study design: randomised double blind placebo-controlled trial.  Treatment details: participants allocated to either fampridine-MR 10 mg bd or placebo of identical appearance for 8 weeks.  Primary outcome: performance on 9-hole peg test (9HPT) after 4 weeks.  Secondary outcomes: persistence of effect on 9HPT; grip strength; visual acuity and contrast sensitivity; modified fatigue impact scale score; sensory discrimination capacity; visual, somatosensory and motor evoked potentials; resting motor threshold; paired-pulse TMS; peripheral nerve conduction studies. RESULTS: 40 patients with MS (60% female, median age 52, median disease duration 13.5 years, median EDSS 6.0) were enrolled.  Treatment with fampridine-MR was not associated with any change in upper limb function as measured by the clinical primary or secondary outcomes.  Treatment with fampridine-MR was also not associated with any difference in electrophysiological measures of upper limb function.  This held true after adjustment for hand dominance, disease duration and severity.  Four patients withdrew from the trial because of lack of efficacy or side-effects; all were in the placebo arm.  Three patients were admitted to hospital during the study period; one with MS exacerbation (placebo group), one with syncope (drug group) and one with UTI (drug group); otherwise there were no serious adverse events. CONCLUSION: Treatment with fampridine-MR was well-tolerated but did not produce clinical benefit in terms of upper limb function, vision or fatigue, nor was there any measurable effect on objective electrophysiological parameters.

Experiencia de uso de fampridina en pacientes con nistagmo vertical inferior / Clinical use of 4-aminopyridine in patients with downbeat nystagmus

OBJETIVO: Presentar los resultados del tratamiento con fampridina de liberación prolongada (4-AP-SR) en pacientes con nistagmo vertical inferior. MATERIAL Y MÉTODO: Serie de casos de nistagmo vertical inferior tratados con 10 mg de 4-AP-SR cada 12h. Se valoraron la mejoría clínica y la variación del nistagmo antes y después del tratamiento, registrando la puntuación en el Dizziness Handicap Inventory, la velocidad de la fase lenta del nistagmo y su frecuencia. RESULTADOS: Se trataron 3 pacientes, ninguno de los cuales notó cambios durante el tratamiento en relación con los síntomas visuales, aunque 2 pacientes notaron mejoría subjetiva de la marcha. No se detectaron diferencias significativas en la puntuación del Dizziness Handicap Inventory ni en las variables videonistagmográficas estudiadas. CONCLUSIÓN: No se han detectado cambios en los síntomas visuales con el tratamiento con 4-AP-SR. La contradicción con estudios previos puede estar producida por un bajo tamaño muestral, la etiología de los casos o la forma de medir los resultado

OBJECTIVE: To present the results of treatment with sustained-release fampridine (4-AP-SR) in patients with downbeat nystagmus. MATERIAL AND METHOD: Series of cases with downbeat nystagmus treated with 10 milligrams of 4-AP-SR every 12 hours. The clinical improvement and the variation of the nystagmus before and after the treatment were evaluated, recording the score in the Dizziness Handicap Inventory, the velocity of the slow phase of the nystagmus and its frequency. RESULTS: Three patients were treated, none of whom reported significant subjective changes during the treatment. No significant differences were detected in the Dizziness Handicap Inventory score or in the studied videonystagmographic variables. CONCLUSION: This communication does not present positive results on the use of 4-AP-SR. The contradiction with previous studies may be caused by a small sample size, by the etiology of the cases or by the way in which the results were measured

Tetraethylammonium, glibenclamide, and 4-aminopyridine modulate post-occlusive reactive hyperemia in non-glabrous human skin with no roles of NOS and COX.

OBJECTIVES: Post-occlusive reactive hyperemia (PORH) following arterial occlusion is widely used to assess cutaneous microvascular function, though the underlying mechanisms remain to be fully elucidated. We evaluated the hypothesis that Ca2+ -activated, ATP-sensitive, and voltage-gated K+ channels (KCa , KATP , and KV channels, respectively) contribute to PORH while nitric oxide synthase (NOS) and cyclooxygenase (COX) do not. METHODS: On separate occasions, cutaneous blood flow (laser Doppler flowmetry) was monitored before and following 5-min arterial occlusion at forearm skin sites treated via microdialysis with the following: Experiment 1 (n = 11): (a) lactated Ringer solution (Control), (b) 10 mM Nω -nitro-L -arginine (NOS inhibitor), (c) 10 mM ketorolac (COX inhibitor), and (d) combined NOS+COX inhibition; Experiment 2 (n = 14): (a) lactated Ringer solution (Control), (b) 50 mM tetraethylammonium (non-selective KCa channel blocker), (c) 5 mM glibenclamide (non-specific KATP channel blocker), and (d) 10 mM 4-aminopyridine (non-selective KV channel blocker). RESULTS: Separate and combined NOS and COX inhibition did not influence PORH. Conversely, tetraethylammonium and glibenclamide attenuated, whereas 4-aminopyridine augmented PORH. CONCLUSIONS: We showed that tetraethylammonium, glibenclamide, and 4-aminopyridine modulate PORH with no roles of NOS and COX in human non-glabrous forearm skin in vivo. Thus, cutaneous PORH changes could reflect altered K+ channel function.

Responder rates to fampridine differ between clinical subgroups of MS patients and patient reported outcome influences treatment decision making.

BACKGROUND: Fampridine is an effective treatment to improve ambulation for some multiple sclerosis (MS) patients. Remarkable discrepancies exist between responder rates in clinical trials and the proportion of patients continuing treatment in clinical practice. This may be related to clinical phenotypes of MS patients, and the influence of patient reported outcome (PRO) on treatment decision making. OBJECTIVE: To analyse responder rates to fampridine on ambulation and upper extremity function (UEF) and the influence on treatment decision making in different clinical subgroups in a real-world setting. METHODS: MS patients with ambulatory impairment treated with fampridine were included. Patients were subdivided based on disease duration, clinical phenotype, Expanded Disability Status Scale (EDSS), baseline walking speed, and presence of UEF impairment. Ambulatory response was assessed with the Timed 25-Foot Walk (T25FW, responder defined as ≥20% improvement) and with the MS Walking Scale (MSWS, responder defined as ≥8 points improvement) as a PRO. For patients also reporting impaired UEF, the Arm Function in MS Questionnaire (AMSQ, responder defined as ≥15 improvement) was the PRO of choice. Decision on treatment continuation was based on improvement of T25FW, MSWS and the clinicians' overall impression for improvement. RESULTS: In total 344 patients were included of which 75.3% continued treatment. More patients with a relapsing clinical phenotype continued treatment vs patients with a progressive phenotype (83.6 vs 68.6%, p < 0.01). A positive linear trend was found between severity of walking disability, as determined by baseline walking speed, and T25FW response (p < 0.01), while there was an inverse linear association between walking disability and MSWS response (p = 0.03). However, the proportion of patients continuing treatment was similar between subgroups of baseline walking speed. Impaired UEF was reported by 183 (66.5%) patients, of which 64 (39.3%) were AMSQ responders. Patients responding on AMSQ compared to non-responders, were also more frequently MSWS responders (82.8 vs 65.3%, p = 0.02), while response on T25FW was similar, and continued treatment more often (85.9 vs 70.7%, p = 0.04). This suggests an influence of PRO on treatment decision making. CONCLUSION: Responder rates and treatment continuation of fampridine differed between clinical subgroups of MS. PROs influenced treatment decision making of fampridine in clinical practice, particularly in patients with mild ambulatory impairment or those reporting UEF impairment. To some extent, these findings explain discrepancies found between clinical trials and clinical practice, and support the importance of subgroup analyses and incorporation of PROs in clinical trials. For clinical practice, using PROs to assess patients experience in conjunction with performance measures helps in treatment decision making.

Impact of 4-aminopyridine on vestibulo-ocular reflex performance.

Vestibulo-ocular reflexes (VOR) are mediated by frequency-tuned pathways that separately transform the different dynamic and static aspects of head motion/position-related sensory signals into extraocular motor commands. Voltage-dependent potassium conductances such as those formed by Kv1.1 are important for the ability of VOR circuit elements to encode highly transient motion components. Here we describe the impact of the Kv1.1 channel blocker 4-aminopyridine (4-AP) on spontaneous and motion-evoked discharge of superior oblique motoneurons. Spike activity was recorded from the motor nerve in isolated preparations of Xenopus laevis tadpoles. Under static conditions, bath application of 1-10 µM 4-AP increased the spontaneous firing rate and provoked repetitive bursts of spikes. During motion stimulation 4-AP also augmented and delayed the peak firing rate suggesting that this drug affects the magnitude and timing of vestibular-evoked eye movements. The exclusive Kv1.1 expression in thick vestibular afferent fibers in larval Xenopus at this developmental stage suggests that the altered extraocular motor output in the presence of 4-AP mainly derives from a firing rate increase of irregular firing vestibular afferents that propagates along the VOR circuitry. Clinically and pharmacologically, the observed 4-AP-mediated increase of peripheral vestibular input under resting and dynamic conditions can contribute to the observed therapeutic effects of 4-AP in downbeat and upbeat nystagmus as well as episodic ataxia type 2, by an indirect increase of cerebellar Purkinje cell discharge.

Aligned microchannel polymer-nanotube composites for peripheral nerve regeneration: Small molecule drug delivery.

Peripheral nerve injury accounts for roughly 2.8% of all trauma patients with an annual cost of 7 billion USD in the U.S. alone. Current treatment options rely on surgical intervention with the use of an autograft, despite associated shortcomings. Engineered nerve guidance conduits, stem cell therapies, and transient electrical stimulation have reported to increase speeds of functional recovery. As an alternative to the conduction effects of electrical stimulation, we have designed and optimized a nerve guidance conduit with aligned microchannels for the sustained release of a small molecule drug that promotes nerve impulse conduction. A biodegradable chitosan structure reinforced with drug-loaded halloysite nanotubes (HNT) was formed into a foam-like conduit with interconnected, longitudinally-aligned pores with an average pore size of 59.3 ±â€¯14.2 µm. The aligned composite with HNTs produced anisotropic mechanical behavior with a Young's modulus of 0.33 ±â€¯0.1 MPa, very similar to that of native peripheral nerve. This manuscript reports on the sustained delivery of 4-Aminopyridine (4AP, molecular weight 94.1146 g/mol), a potassium-channel blocker as a growth factor alternative to enhance the rate of nerve regeneration. The conduit formulation released a total of 30 ±â€¯2% of the encapsulated 4AP in the first 7 days. Human Schwann cells showed elevated expression of key proteins such as nerve growth factor, myelin protein zero, and brain derived neurotrophic factor in a 4AP dose dependent manner. Preliminary in vivo studies in a critical-sized sciatic nerve defect in Wistar rats confirmed conduit suturability and strength to withstand ambulatory forces over 4 weeks of their implantation. Histological evaluations suggest conduit biocompatibility and Schwann cell infiltration and organization within the conduit and lumen. These nerve guidance conduits and 4AP sustained delivery may serve as an attractive strategy for nerve repair and regeneration.

Pulmonary arterial hypertension in patient treated for multiple sclerosis with 4-aminopyridine.

4-Aminopyridine (4-AP) is a recent treatment indicated to improve walking in patient with multiple sclerosis. We report the first case of pulmonary arterial hypertension (PAH) that we attribute to the use of 4-AP. A 64-year-old woman with multiple sclerosis presented with dyspnea. After excluding other secondary causes of pulmonary hypertension, a diagnosis of severe PAH due to 4-AP was made based on right heart catheterization. History revealed that the dyspnea began with the initiation of 4-AP. After discontinuation of 4-AP therapy and initiation of ambrisentan and tadalafil, dyspnea and pulmonary arterial pressure have improved significantly and one specific PAH treatment was stopped. 4-AP is an outward rectifying potassium channel blocker with a vasoconstrictor effect in animal's pulmonary artery. According to the chronological sequence of events, the lack of other etiology, and its pharmacological plausibility, 4-AP is highly suspected to have induced our patient's PAH.

Long-term effects of prolonged-release fampridine in cognitive function, fatigue, mood and quality of life of MS patients: The IGNITE study.

BACKGROUND: Studies have reported conflicting results regarding the potential benefit of prolonged release (PR) fampridine in other domains besides walking. Moreover, only a small number of studies have explored long- term effects of PR fampridine. The aim of this study was to assess cognitive function, quality of life, mood and fatigue in MS patients treated with fampridine after 6 and 12 months of treatment. METHODS: IGNITE was an observational, open label study. Subjects were examined with the timed 25-ft walk (T25FW) and the BICAMS battery and were asked to complete the Multiple Sclerosis Impact Scale (MSIS-29), Modified Fatigue Impact Scale (MFIS), Beck Depression Inventory-II (BDI-II) and MS International Quality-of-Life questionnaire (MUSIQOL) at baseline and at weeks 24 and 48. Patients were sub-grouped into responders (n:40) and non-responders (n:20) according to T25FW performance after 2 weeks on treatment. RESULTS: After 6 months, statistically significant improvement was observed on T25FW (p < .001), SDMT (p < .001) and MSIS29 (p < .001), for responders. After 1 year on treatment, statistically significant improvement was observed in T25FW (p < .001), MSIS29 (p = .004), SDMT (p < .001) and MUSIQOL (p = .03) for responders. There were no statistically significant improvements for the non-responders. CONCLUSIONS: PR Fampridine may have a beneficial effect on information processing speed though not on memory. Study data provide some evidence that fampridine treatment may reduce the impact of MS on daily activities and improve quality of life but has no effect on subjective fatigue and mood.

Pharmacological characterization of crotamine effects on mice hind limb paralysis employing both ex vivo and in vivo assays: Insights into the involvement of voltage-gated ion channels in the crotamine action on skeletal muscles.

The high medical importance of Crotalus snakes is unquestionable, as this genus is the second in frequency of ophidian accidents in many countries, including Brazil. With a relative less complex composition compared to other genera venoms, as those from the Bothrops genus, the Crotalus genus venom from South America is composed basically by the neurotoxin crotoxin (a phospholipase A2), the thrombin-like gyroxin (a serinoprotease), a very potent aggregating protein convulxin, and a myotoxic polypeptide named crotamine. Interestingly not all Crotalus snakes express crotamine, which was first described in early 50s due to its ability to immobilize animal hind limbs, contributing therefore to the physical immobilization of preys and representing an important advantage for the envenoming efficacy, and consequently, for the feeding and survival of these snakes in nature. Representing about 10-25% of the dry weight of the crude venom of crotamine-positive rattlesnakes, the polypeptide crotamine is also suggested to be of importance for antivenom therapy, although the contribution of this toxin to the main symptoms of envenoming process remains far unknown until now. Herein, we concomitantly performed in vitro and in vivo assays to show for the first time the dose-dependent response of crotamine-triggered hind limbs paralysis syndrome, up to now believed to be observable only at high (sub-lethal) concentrations of crotamine. In addition, ex vivo assay performed with isolated skeletal muscles allowed us to suggest here that compounds active on voltage-sensitive sodium and/or potassium ion channels could both affect the positive inotropic effect elicited by crotamine in isolated diaphragm, besides also affecting the hind limbs paralysis syndrome imposed by crotamine in vivo. By identifying the potential molecular targets of this toxin, our data may contribute to open new roads for translational studies aiming to improve the snakebite envenoming treatment in human. Interestingly, we also demonstrate that the intraplantal or intraperitoneal (ip) injections of crotamine in mice do not promote pain. Therefore, this work may also suggest the profitable utility of non-toxic analogs of crotamine as a potential tool for targeting voltage-gated ion channels in skeletal muscles, aiming its potential use in the therapy of neuromuscular dysfunctions and envenoming therapy.

[A retrospective study of the effects of 3,4-diaminopyridine treatment in Lambert-Eaton myasthenic syndrome].

In this independent clinical study, we analyzed retrospectively the clinical features of 9 cases (6 male and 3 female) of Lambert-Eaton myasthenic syndrome that were administered 3,4-diaminopyridine (3,4-DAP). Four cases showed no cancer and 5 cases had small cell lung carcinoma. Seven cases were positive for anti voltage-gated calcium channel antibodies. Activities of daily living (ADL) were improved by 3,4-DAP in 8 cases that showed mainly weakness of the extremities, but did not improve ADL in 1 case with cerebellar ataxia of paraneoplastic cerebellar degeneration (PCD). Seven cases showed autonomic symptoms, and 6 cases were improved with 3,4-DAP. The maintenance dose varied widely among individuals, with a single dose ranging from 10 to 40 mg. Each patient was prescribed a maintenance dose 3 to 7 times a day. The daily dosage ranged from 36 to 100 mg. Two cases showed adverse effects to the treatment. Of those 2 cases, 1 case treated at 45 mg/day discontinued treatment, but another case treated at 100 mg/day reduced the dosage and continued treatment. The administration period was 1 to 149 months. Three cases have continued 3,4-DAP for more than 10 years. Four cases have discontinued 3,4-DAP, with 2 cases discontinuing due to death, 1 case discontinuing due to progression of cancer, and 1 case discontinuing due to an adverse reaction. Our results suggest that 3,4-DAP treatment is effective for weakness and autonomic symptoms, but may be ineffective for ataxia of PCD. Treatment with 3,4-DAP can be tolerated for a long period, but the optimal dosage varies widely among individuals.

Development of a PET radioligand for potassium channels to image CNS demyelination.

Central nervous system (CNS) demyelination represents the pathological hallmark of multiple sclerosis (MS) and contributes to other neurological conditions. Quantitative and specific imaging of demyelination would thus provide critical clinical insight. Here, we investigated the possibility of targeting axonal potassium channels to image demyelination by positron emission tomography (PET). These channels, which normally reside beneath the myelin sheath, become exposed upon demyelination and are the target of the MS drug, 4-aminopyridine (4-AP). We demonstrate using autoradiography that 4-AP has higher binding in non-myelinated and demyelinated versus well-myelinated CNS regions, and describe a fluorine-containing derivative, 3-F-4-AP, that has similar pharmacological properties and can be labeled with 18F for PET imaging. Additionally, we demonstrate that [18F]3-F-4-AP can be used to detect demyelination in rodents by PET. Further evaluation in Rhesus macaques shows higher binding in non-myelinated versus myelinated areas and excellent properties for brain imaging. Together, these data indicate that [18F]3-F-4-AP may be a valuable PET tracer for detecting CNS demyelination noninvasively.

Brief activation of GABAergic interneurons initiates the transition to ictal events through post-inhibitory rebound excitation.

Activation of γ-aminobutyric acid (GABAA) receptors have been associated with the onset of epileptiform events. To investigate if a causal relationship exists between GABAA receptor activation and ictal event onset, we activated inhibitory GABAergic networks in the superficial layer (2/3) of the somatosensory cortex during hyperexcitable conditions using optogenetic techniques in mice expressing channelrhodopsin-2 in all GABAergic interneurons. We found that a brief 30ms light pulse reliably triggered either an interictal-like event (IIE) or ictal-like ("ictal") event in the in vitro cortical 4-Aminopyridine (4-AP) slice model. The link between light pulse and epileptiform event onset was lost following blockade of GABAA receptors with bicuculline methiodide. Additionally, recording the chronological sequence of events following a light pulse in a variety of configurations (whole-cell, gramicidin-perforated patch, and multi-electrode array) demonstrated an initial hyperpolarization followed by post-inhibitory rebound spiking and a subsequent slow depolarization at the transition to epileptiform activity. Furthermore, the light-triggered ictal events were independent of the duration or intensity of the initiating light pulse, suggesting an underlying regenerative mechanism. Moreover, we demonstrated that brief GABAA receptor activation can initiate ictal events in the in vivo 4-AP mouse model, in another common in vitro model of epileptiform activity, and in neocortical tissue resected from epilepsy patients. Our findings reveal that the synchronous activation of GABAergic interneurons is a robust trigger for ictal event onset in hyperexcitable cortical networks.

Metyrapone prevents acute glucose hypermetabolism and short-term brain damage induced by intrahippocampal administration of 4-aminopyridine in rats.

Intracerebral administration of the potassium channel blocker 4-aminopyridine (4-AP) triggers neuronal depolarization and intense acute seizure activity followed by neuronal damage. We have recently shown that, in the lithium-pilocarpine rat model of status epilepticus (SE), a single administration of metyrapone, an inhibitor of the 11ß-hydroxylase enzyme, had protective properties of preventive nature against signs of brain damage and neuroinflammation. Herein, our aim was to investigate to which extent, pretreatment with metyrapone (150 mg/kg, i.p.) was also able to prevent eventual changes in the acute brain metabolism and short-term neuronal damage induced by intrahippocampal injection of 4-AP (7 µg/5 µl). To this end, regional brain metabolism was assessed by 2-deoxy-2-[18F]fluoro-d-glucose ([18F]FDG) positron emission tomography (PET) during the ictal period. Three days later, markers of neuronal death and hippocampal integrity and apoptosis (Nissl staining, NeuN and active caspase-3 immunohistochemistry), neurodegeneration (Fluoro-Jade C labeling), astrogliosis (glial fibrillary acidic protein (GFAP) immunohistochemistry) and microglia-mediated neuroinflammation (in vitro [18F]GE180 autoradiography) were evaluated. 4-AP administration acutely triggered marked brain hypermetabolism within and around the site of injection as well as short-term signs of brain damage and inflammation. Most important, metyrapone pretreatment was able to reduce ictal hypermetabolism as well as all the markers of brain damage except microglia-mediated neuroinflammation. Overall, our study corroborates the neuroprotective effects of metyrapone against multiple signs of brain damage caused by seizures triggered by 4-AP. Ultimately, our data add up to the consistent protective effect of metyrapone pretreatment reported in other models of neurological disorders of different etiology.