SGLT2 inhibitors therapy protects glucotoxicity-induced ß-cell failure in a mouse model of human KATP-induced diabetes through mitigation of oxidative and ER stress.

Progressive loss of pancreatic ß-cell functional mass and anti-diabetic drug responsivity are classic findings in diabetes, frequently attributed to compensatory insulin hypersecretion and ß-cell exhaustion. However, loss of ß-cell mass and identity still occurs in mouse models of human KATP-gain-of-function induced Neonatal Diabetes Mellitus (NDM), in the absence of insulin secretion. Here we studied the temporal progression and mechanisms underlying glucotoxicity-induced loss of functional ß-cell mass in NDM mice, and the effects of sodium-glucose transporter 2 inhibitors (SGLT2i) therapy. Upon tamoxifen induction of transgene expression, NDM mice rapidly developed severe diabetes followed by an unexpected loss of insulin content, decreased proinsulin processing and increased proinsulin at 2-weeks of diabetes. These early events were accompanied by a marked increase in ß-cell oxidative and ER stress, without changes in islet cell identity. Strikingly, treatment with the SGLT2 inhibitor dapagliflozin restored insulin content, decreased proinsulin:insulin ratio and reduced oxidative and ER stress. However, despite reduction of blood glucose, dapagliflozin therapy was ineffective in restoring ß-cell function in NDM mice when it was initiated at >40 days of diabetes, when loss of ß-cell mass and identity had already occurred. Our data from mouse models demonstrate that: i) hyperglycemia per se, and not insulin hypersecretion, drives ß-cell failure in diabetes, ii) recovery of ß-cell function by SGLT2 inhibitors is potentially through reduction of oxidative and ER stress, iii) SGLT2 inhibitors revert/prevent ß-cell failure when used in early stages of diabetes, but not when loss of ß-cell mass/identity already occurred, iv) common execution pathways may underlie loss and recovery of ß-cell function in different forms of diabetes. These results may have important clinical implications for optimal therapeutic interventions in individuals with diabetes, particularly for those with long-standing diabetes.

Haploinsufficiency, Dominant Negative, and Gain-of-Function Mechanisms in Epilepsy: Matching Therapeutic Approach to the Pathophysiology.

This review summarizes the pathogenic mechanisms that underpin the monogenic epilepsies and discusses the potential of novel precision therapeutics to treat these disorders. Pathogenic mechanisms of epilepsy include recessive (null alleles), haploinsufficiency, imprinting, gain-of-function, and dominant negative effects. Understanding which pathogenic mechanism(s) that underlie each genetic epilepsy is pivotal to design precision therapies that are most likely to be beneficial for the patient. Novel therapeutics discussed include gene therapy, gene editing, antisense oligonucleotides, and protein replacement. Discussions are illustrated and reinforced with examples from the literature.

Novel pharmacological modulation of dystonic phenotypes caused by a gain-of-function mutation in the Na+ leak-current channel.

The Na leak-current channel (NALCN) regulates the resting membrane potential in excitable cells, thus determining the likelihood of depolarization in response to incoming signals. Gain-of-function (gf) mutations in this channel are associated with severe dystonic movement disorders in man. Currently, there are no known pharmacological antagonists or selective modulators of this important channel. A gain-of-function mutation in NALCN of C. elegans [known as unc-77(e625)] causes uncoordinated, hyperactive locomotion. We hypothesized that this hyperactive phenotype can be rescued with pharmacological modulators. Here, we summarize the results of targeted drug screening aimed at identification of drugs that corrected locomotion deficits in unc-77(e625) animals. To assay hyperactive locomotion, animals were acutely removed from food and characteristic foraging movements were quantified. Drug screening revealed that 2-aminoethoxydiphenyl borate (2-ABP), nifedipine, nimodipine, flunarizine and ethoxzolamide significantly decreased abnormal movements in unc-77(e625) animals. 2-APB also corrected egg release and coiling deficits in this strain. In addition, serotonin and dopamine both reduced hyperactive locomotion, consistent with regulatory interactions between these systems and the NALCN. 2-APB induced movement phenotypes in wild-type animals that faithfully mimicked those observed in NALCN knockout strains, which suggested that this drug may directly block the channel. Moreover, 2-APB and flunarizine showed significant structural similarities suggestive of overlap in their mode of action. Together, these studies have revealed new insights into regulation of NALCN function and led to the discovery of a potential pharmacological antagonist of the NALCN.

CRISPR-Generated Nrf2a Loss- and Gain-of-Function Mutants Facilitate Mechanistic Analysis of Chemical Oxidative Stress-Mediated Toxicity in Zebrafish.

The transcription factor Nrf2a induces a cellular antioxidant response and provides protection against chemical-induced oxidative stress, as well as playing a critical role in development and disease. Zebrafish are a powerful model to study the role of Nrf2a in these processes but have been limited by reliance on transient gene knockdown techniques or mutants with only partial functional alteration. We developed several lines of zebrafish carrying different null (loss of function, LOF) or hyperactive (gain of function, GOF) mutations to facilitate our understanding of the Nrf2a pathway in protecting against oxidative stress. The mutants confirmed Nrf2a dependence for induction of the antioxidant genes gclc, gstp, prdx1, and gpx1a and identified a role for Nrf2a in the baseline expression of these genes, as well as for sod1. Specifically, the 4-fold induction of gstp by tert-butyl hydroperoxide (tBHP) in wild type fish was abolished in LOF mutants. In addition, baseline gstp expression in GOF mutants increased by 12.6-fold and in LOF mutants was 0.8-fold relative to wild type. Nrf2a LOF mutants showed increased sensitivity to the acute toxicity of cumene hydroperoxide (CHP) and tBHP throughout the first 4 days of development. Conversely, GOF mutants were less sensitive to CHP toxicity during the first 4 days of development and were protected against the toxicity of both hydroperoxides after 4 dpf. Neither gain nor loss of Nrf2a modulated the toxicity of R-(-)-carvone (CAR), despite the ability of this compound to potently induce Nrf2a-dependent antioxidant genes. Similar to other species, GOF zebrafish mutants exhibited significant growth and survival defects. In summary, these new genetic tools can be used to facilitate the identification of downstream gene targets of Nrf2a, better define the role of Nrf2a in the toxicity of environmental chemicals, and further the study of diseases involving altered Nrf2a function.

Eficacia y seguridad de afatinib como tratamiento de primera línea en pacientes adultos con cáncer de pulmón de células no pequeñas avanzado (estadios IIIB/IV), con mutaciones activadoras del gen del receptor del factor de crecimiento epidérmico, con contraindicación a erlotinib por hipersensibilidad / Efficacy and safety of afatinib as first-line treatment in adult patients with advanced non-small cell lung cancer (stages IIIB/IV), with activating mutations of the epidermal growth factor receptor gene, with contraindication to erlotinib due to hypersensitivity

INTRODUCCIÓN: El cáncer de pulmón de células no pequeñas (CPCNP) es la causa más frecuente (85 % - 90 %) de tumores pulmonares malignos que generalmente afectan a adultos que fuman y que tienen ≥ 65 años. En Perú, en 2017, el cáncer de pulmón fue la segunda causa de muerte entre todos los cánceres, con una mortalidad anual de 8.8 muertes por cada 100,000 personas.  La terapia de primera línea del CPCNP avanzado (estadio IIIB/IV) depende del estado de las mutaciones conductoras oncogénicas, la expresión de PD-L1 y la histología. Así, para los casos en los que se detecta una mutación sensibilizante1 del receptor de factor de crecimiento epidérmico (EGFR, por sus siglas en inglés), se recomienda ofrecer una terapia dirigida contra el EGFR utilizando los inhibidores de la tirosina quinasa del EGFR (de aquí en adelante llamados TKI, por sus siglas en inglés) de primera línea (e.g., erlotinib, afatinib).  En el Seguro Social de Salud del Perú (EsSalud), los pacientes con CPCNP avanzado cuyos tumores poseen mutaciones positivas2 del EGFR disponen de erlotinib como tratamiento de primera línea según lo establecido en el Petitorio Farmacológico de EsSalud. Sin embargo, existe un grupo de pacientes que presentan eventos adversos (EA) cutáneos severos (grado 3 o mayor) asociados al tratamiento con erlotinib, quienes, en ciertos casos, requerirán de la discontinuación de uso del medicamento, a pesar del manejo óptimo de las toxicidades cutáneas (e.g., reducción de dosis). En este grupo de pacientes con hipersensibilidad a erlotinib (contraindicación de uso), los médicos especialistas de la institución sugieren el uso de un TKI alternativo: afatinib. OBJETIVO: Evaluar la mejor evidencia disponible sobre la eficacia y seguridad de afatinib, en comparación con la quimioterapia, en pacientes adultos con CPCNP avanzado, con mutaciones activadoras3 del gen del EGFR, con contraindicación a erlotinib por hipersensibilidad. TECNOLOGÍA SANITARIA DE INTERÉS: Afatinib: Afatinib es un inhibidor selectivo e irreversible de la actividad de la tirosina quinasa de los receptores de la familia ErbB: EGFR (ErbB1), HER2 (ErbB2), HER3 (ErbB3) y HER4 (ErbB4). Afatinib se une en forma covalente a los dominios de la tirosina quinasa de estos receptores e inhibe irreversiblemente la autofosforilación de la tirosina quinasa, lo que resulta en un bloqueo de las señales de los receptores ErbB (European Medicines Agency 2019). METODOLOGÍA: Se realizó una búsqueda sistemática de literatura con el objetivo de identificar evidencia sobre la eficacia y seguridad de afatinib, en comparación con la quimioterapia, en pacientes adultos con CPCNP avanzado, con mutaciones activadoras del gen del EGFR, con contraindicación a erlotinib por hipersensibilidad. Se utilizó la base de datos The Cochrane Library, PubMed, LILACS y el metabuscador TRIP Database, priorizándose evidencia proveniente de ensayos clínicos aleatorizados. Asimismo, se realizó una búsqueda dentro de bases de datos pertenecientes a grupos que realizan evaluaciones de tecnologías sanitarias y guías de práctica clínica, incluyendo el Scottish Medicines Consortium (SMC), el National Institute for Health and Care Excellence (NICE), la Canadian Agency for Drugs and Technologies in Health (CADTH), la Haute Autorité de Santé (HAS), el Institut für Qualität und Wirtschaftlichkeit im Gesundheitswesen (IQWiG), además de la Base Regional de Informes de Evaluación de Tecnologías en Salud de las Américas (BRISA) y páginas web de sociedades especializadas en cáncer de pulmón. Se hizo una búsqueda adicional en la página web de clinicaltrials.gov, para poder identificar ensayos clínicos en curso o que no hayan sido publicados para, de este modo, disminuir el riesgo de sesgo de publicación. La búsqueda sistemática se basó en una metodología escalonada, la cual consistió en la búsqueda inicial de estudios secundarios (tipo revisiones sistemáticas con o sin metaanálisis). RESULTADOS: Se realizó una búsqueda de la literatura con respecto a la eficacia y seguridad de afatinib, en comparación con la quimioterapia, en pacientes adultos con CPCNP avanzado, con mutaciones activadoras del gen del EGFR, con contraindicación a erlotinib por hipersensibilidad. Dado que no se identificaron estudios en una población específica de pacientes con contraindicación a erlotinib, se procedió a revisar la evidencia para la población general de pacientes con CPCNP avanzado, con mutaciones activadoras del gen del EGFR. CONCLUSIONES: Dado que no se identificaron estudios en la población específica de pacientes con contraindicación a erlotinib, se procedió a revisar la evidencia para la población general de pacientes con CPCNP avanzado, con mutaciones activadoras del gen del receptor del factor de crecimiento epidérmico. En líneas generales, todas las GPC y ETS basaron sus recomendaciones y/o conclusiones en los resultados de los estudios LUX-Lung 3 y/o LUX-Lung 6. La evidencia procedente de los estudios LUX-Lung 3 y LUX-Lung 6 muestra que afatinib comparado con la quimioterapia ofrece un beneficio clínico en términos de una mayor sobrevida global (aproximadamente 11 meses adicionales) en los pacientes con CPCNP metastásico, ECOG 0-1 y mutaciones del EGFR tipo Del19, sin tratamiento previo. Además, afatinib tuvo un perfil de seguridad similar al de la quimioterapia con cisplatino más pemetrexed y un mejor perfil de seguridad que la quimioterapia con gemcitabina más cisplatino, en términos de EA severos, EA serios y discontinuación debido a EA. A diferencia de las GPC identificadas, que recomendaron el uso de afatinib en la población general de pacientes con CPCNP y mutaciones positivas del EGFR, esta evaluación de la evidencia identificó que los pacientes con mutaciones Del19 serían el subgrupo con mayor probabilidad de beneficiarse del tratamiento con afatinib. Por otro lado, no se identificó evidencia directa que sustente el uso de afatinib en el grupo de pacientes previamente tratados. Sin embargo, tal como se menciona en el Dictamen Preliminar de Evaluación de Tecnología Sanitaria N° 041-SDEPFyOTSDETS-IETSI-2019: Eficacia y Seguridad de erlotinib en pacientes adultos con CPCNP, metastásico o irresecable, con mutación del gen del EGFR, tras fallo a al menos una línea de quimioterapia, se valora que la evidencia del uso de afatinib en el contexto de primera línea puede ser extrapolada al grupo de pacientes que han sido previamente tratados con quimioterapia sistémica y que han experimentado hipersensibilidad severa a erlotinib. Adicionalmente, es importante analizar el contexto de intercambio de TKI (de erlotinib a afatinib) debido a EA cutáneos severos como resultado de uma hipersensibilidad a erlotinib (contraindicación de uso) en pacientes con CPCNP avanzado y mutación del EGFR, ya que es el grupo específico de pacientes en quienes se propone el uso de afatinib en la institución. Así, si bien la evidencia sobre el intercambio de TKI debido a EA es limitada, algunas series de casos han sugerido que esta aproximación proporciona un efecto beneficioso en pacientes con CPCNP avanzado y mutaciones del EGFR. Además, el intercambio de erlotinib a afatinib podría justificarse biológicamente dada las diferencias en las estructuras químicas de erlotinib y afatinib, que podrían influir en los EA asociados con estos medicamentos. De este modo, teniendo en cuenta que los pacientes que recibirían un segundo TKI tendrían que haber demostrado no tener una mutación resistente a TKI, se estima que los pacientes que discontinúan el tratamiento con erlotinib debido a hipersensibilidad severa aún podrían beneficiarse de "cambiar" a un segundo TKI (afatinib). Con ello, y considerando la experiencia de uso de TKI a nivel institucional y la opinión favorable por parte de los médicos especialistas de la institución, el equipo evaluador del IETSI encuentra suficientes argumentos técnicos para aprobar el uso de afatinib en pacientes adultos con CPCNP avanzado, con mutaciones activadoras del gen del EGFR (Del19), con contraindicación a erlotinib por hipersensibilidad. Por lo expuesto, el IETSI aprueba el uso de afatinib en pacientes adultos con CPCNP avanzado, con mutaciones activadoras del gen del receptor del factor de crecimiento epidérmico, con contraindicación a erlotinib por hipersensibilidad, según lo establecido en el Anexo N° 1. La vigencia del presente dictamen preliminar es de un año a partir de la fecha de publicación. Así, la continuación de dicha aprobación estará sujeta a los resultados obtenidos de los pacientes que reciban este tratamiento, a los reportes de seguridad que puedan surgir durante farmacovigilancia activa y nueva evidencia que pueda surgir en el tiempo.

A novel gain-of-function Nav1.7 mutation in a carbamazepine-responsive patient with adult-onset painful peripheral neuropathy.

Voltage-gated sodium channel Nav1.7 is a threshold channel in peripheral dorsal root ganglion (DRG), trigeminal ganglion, and sympathetic ganglion neurons. Gain-of-function mutations in Nav1.7 have been shown to increase excitability in DRG neurons and have been linked to rare Mendelian and more common pain disorders. Discovery of Nav1.7 variants in patients with pain disorders may expand the spectrum of painful peripheral neuropathies associated with a well-defined molecular target, thereby providing a basis for more targeted approaches for treatment. We screened the genome of a patient with adult-onset painful peripheral neuropathy characterized by severe burning pain and report here the new Nav1.7-V810M variant. Voltage-clamp recordings were used to assess the effects of the mutation on biophysical properties of Nav1.7 and the response of the mutant channel to treatment with carbamazepine (CBZ), and multi-electrode array (MEA) recordings were used to assess the effects of the mutation on the excitability of neonatal rat pup DRG neurons. The V810M variant increases current density, shifts activation in a hyperpolarizing direction, and slows kinetics of deactivation, all gain-of-function attributes. We also show that DRG neurons that express the V810M variant become hyperexcitable. The patient responded to treatment with CBZ. Although CBZ did not depolarize activation of the mutant channel, it enhanced use-dependent inhibition. Our results demonstrate the presence of a novel gain-of-function variant of Nav1.7 in a patient with adult-onset painful peripheral neuropathy and the responsiveness of that patient to treatment with CBZ, which is likely due to the classical mechanism of use-dependent inhibition.

Gain of function in Mycobacterium bovis BCG Moreau due to loss of a transcriptional repressor.

The Bacille Calmette-Guérin (BCG) vaccine comprises a family of genetically different strains derived by the loss of genomic regions (RDs) and other mutations. In BCG Moreau, loss of RD16 inactivates rv3405c * , encoding a transcriptional repressor that negatively regulates the expression of Rv3406, an alkyl sulfatase. To evaluate the impact of this loss on the BCG and host cell viability and the cytokine profile, THP-1 cells were infected with BCG Moreau (harbouring the empty vector) and a complemented strain carrying a functional copy of rv3405c. Viability of the host cells and bacteria as well as the pattern of cytokine secretion were evaluated. Our results show that the viability of BCG Moreau is higher than that of the complemented strain in an axenic medium, suggesting a possible functional gain associated with the constitutive expression of Rv3406. Viability of the host cells did not vary significantly between recombinant strains, but differences in the profiles of the cytokine secretion (IL-1ß and IL-6) were observed. Our results suggest an example of a functional gain due to gene loss contributing to the elucidation of the impact of RD16 on the physiology of BCG Moreau.

A gain-of-function study of amelioration of pentylenetetrazole-induced seizures by endogenous prostaglandin D2.

We previously showed that knockout mice of hematopoietic prostaglandin (PG) D synthase (H-PGDS) produce less PGD2 to exacerbate pentylenetetrazole (PTZ)-induced seizures. Here, we adopted a gain-of-function strategy and used transgenic mice that over-express human H-PGDS enzyme, to elucidate the role of overproduction of endogenous PGD2 in PTZ-induced seizures. H-PGDS-transgenic mice showed the elevated level of a urinary metabolite of PGD2, tetranor-PGDM, 3.3- and 2.8-fold higher than the wild-type littermates under the basal condition and after the PTZ administration, respectively, without significantly changing the urinary concentration of a PGE2-metabolite, tetranor-PGE2. The intensity of PTZ-induced seizures was decreased in H-PGDS-transgenic mice as evident by the increased seizure onset latency, and a decrease in total duration of generalized tonic-clonic seizures and a total number of EEG seizure spikes during the postictal period (84 s, 17 s, and 5.3/min, respectively), as compared to wild-type mice (53 s, 24 s, and 12.6/min, respectively). These results indicate that overproduction of endogenous PGD2 decreased PTZ-induces seizures.

Irreversible tyrosine kinase inhibition of epidermal growth factor receptor with afatinib in EGFR activating mutation-positive advanced non-small-cell lung cancer.

Despite recent advances in the systemic therapy of non-small-cell lung cancer (nsclc), the prognosis for stage iv disease remains poor. The discovery of targetable mutations has led to new treatment options. The most common mutations, the EGFR activating mutations, are present in about 50% of Asian patients and up to 15% of white patients. First-generation reversible epidermal growth factor receptor (egfr) tyrosine kinase inhibitors (tkis) have led to improved survival in patients positive for EGFR activating mutations, but resistance eventually leads to disease progression. The irreversible egfr tki afatinib was developed to counter such resistance. The clinical efficacy of afatinib has been shown in first-line studies comparing it with both cytotoxic chemotherapy and first-generation egfr tkis. Afatinib has also shown continued benefit beyond progression while a patient is taking an egfr inhibitor. Furthermore, its toxicity profile is both predictable and manageable. The results of the principal clinical trials assessing afatinib are reviewed here.

Combination of Proteasome and Histone Deacetylase Inhibitors Overcomes the Impact of Gain-of-Function p53 Mutations.

Mutations in the "guardian of the genome" TP53 predominate in solid tumors. In addition to loss of tumor suppressor activity, a specific subset of missense mutations confers additional oncogenic properties. These "gain-of-function" (GOF) mutations portend poor prognosis across cancer types regardless of treatment. Our objective in this study was to identify novel therapeutic opportunities to overcome the deleterious effects of GOF TP53 mutants. Using gynecologic cancer cell lines with known TP53 mutational status, we established that treatment with a proteasome inhibitor induced cell death in cells with two recurrent GOF TP53 mutations (R175H and R248Q), and addition of a histone deacetylase inhibitor (HDACi) enhanced this effect. By contrast, p53-null cancer cells were relatively resistant to the combination. Proteasome inhibition promoted apoptosis of cells with TP53 GOF mutations, potentially through induction of the unfolded protein response. In line with the reported hyperstabilization of GOF p53 protein, cells treated with HDACi exhibited reduced levels of p53 protein. Together, these data form the basis for future clinical studies examining therapeutic efficacy in a preselected patient population with GOF TP53 mutations.

Gain of function in Mycobacterium bovis BCG Moreau due to loss of a transcriptional repressor

The Bacille Calmette-Guérin (BCG) vaccine comprises a family of genetically different strains derived by the loss of genomic regions (RDs) and other mutations. In BCG Moreau, loss of RD16 inactivates rv3405c * , encoding a transcriptional repressor that negatively regulates the expression of Rv3406, an alkyl sulfatase. To evaluate the impact of this loss on the BCG and host cell viability and the cytokine profile, THP-1 cells were infected with BCG Moreau (harbouring the empty vector) and a complemented strain carrying a functional copy of rv3405c. Viability of the host cells and bacteria as well as the pattern of cytokine secretion were evaluated. Our results show that the viability of BCG Moreau is higher than that of the complemented strain in an axenic medium, suggesting a possible functional gain associated with the constitutive expression of Rv3406. Viability of the host cells did not vary significantly between recombinant strains, but differences in the profiles of the cytokine secretion (IL-1β and IL-6) were observed. Our results suggest an example of a functional gain due to gene loss contributing to the elucidation of the impact of RD16 on the physiology of BCG Moreau.

The impact of intermittent versus continuous exposure to EGFR tyrosine kinase inhibitor on selection of EGFR T790M-mutant drug-resistant clones in a lung cancer cell line carrying activating EGFR mutation.

Drug-resistant cell lines are essential tools for investigating the mechanisms of resistance to molecular-targeted anti-cancer drugs. However, little is known about how to establish clinically relevant drug-resistant cell lines. Our study examined the impact of a drug-free period on the establishment of a cell line with clinically relevant resistance to molecular-targeted drugs. We used PC9 cells, a lung cancer cell line carrying EGFR mutation, because this is a validated target for EGFR tyrosine kinase inhibitors (TKI). PC9 cells were intermittently or continuously exposed to increasing concentrations of gefitinib (0.01 µM to 1.0 µM) and the emergence of the most common acquired resistance mutation in EGFR, T790M, was determined. T790M was detected at a 25-fold lower drug concentration in cells continuously exposed to gefitinib (PC9/GRc) than in cells intermittently exposed to gefitinib (PC9/GRi) (0.04 µM vs 1.0 µM, respectively). The mutation frequencies at those drug concentrations were 19.8% and 8.0% in PC9/GRc and PC9/GRi cells, respectively. After drug-free culture for 8 weeks, resistance to gefitinib decreased in the PC9/GRi cells but not in the PC9/GRc cells. In the PC9/GRc cells, the frequency of the T790M mutation was consistently about 20% from 0.04 µM to 1.0 µM of gefitinib. In the PC9/GRc cells, the T790M mutation was detected in all single-cell clones, at frequencies ranging from 7.0% to 37.0%, with a median of 19.5% (95% confidence interval, 17.3%-20.9%). In conclusion, compared with intermittent drug exposure, continuous exposure might select better minor drug-resistant clones when creating cell lines resistant to molecular-targeted drugs.