Roadmap for an early gene therapy for cystic fibrosis airway disease

[Towards a generalization of non-invasive prenatal diagnosis of single-gene disorders? Assesment and outlook]

OBJECTIVES

The screening of fetal aneuploidies and non-invasive prenatal diagnosis of monogenic diseases (NIPD-MD) both rely on the study of free fetal DNA in maternal circulation, but their respective rise was unequal. Development of NIPD-MD has taken longer as it represents a less attractive commercial dynamic for industry, but also because it usually involves the development of tailored tests specific to each pathogenic variant.

METHODS

We have carried out a review of the literature on the various indications and technologies involved in the use of NIPD-MM. We present its current implementation and its development in France.

RESULTS

To date, NIPD-MD has been routinely offered in France for several years by the laboratories of the French NIPD-MD network but remains mostly limited to the exclusion of paternal or de novo variants, the exclusion DPNI-MD. Indeed, it is still difficult to study the transmission of maternal variants from circulating free DNA analysis, due to its biological complexity: coexistence and predominance of similar DNA sequences of maternal origin. Different strategies, either direct or indirect, are being evaluated to establish fetal status regardless of the parental origin of the disease or its transmission mode. The emergence of commercial screening solutions for monogenic diseases complements the arsenal of prenatal exploration tools for these diseases.

CONCLUSION

The multitude of existing technologies and protocols may complicate the information provided during antenatal consultations, but mastery of know-how and knowledge of ethical issues of NIPD-MD will ensure optimal service and better management of pregnancies at risk of transmitting monogenic disease.

Anticipating New Treatments for Cystic Fibrosis: A Global Survey of Researchers

Cystic fibrosis is a life-threatening disease that affects at least 100,000 people worldwide. It is caused by a defect in the cystic fibrosis transmembrane regulator (CFTR) gene and presently, 360 CFTR-causing mutations have been identified. Since the discovery of the CFTR gene, the expectation of developing treatments that can substantially increase the quality of life or even cure cystic fibrosis patients is growing. Yet, it is still uncertain today which developing treatments will be successful against cystic fibrosis. This study addresses this gap by assessing the opinions of over 524 cystic fibrosis researchers who participated in a global web-based survey. For most respondents, CFTR modulator therapies are the most likely to succeed in treating cystic fibrosis in the next 15 years, especially through the use of CFTR modulator combinations. Most respondents also believe that fixing or replacing the CFTR gene will lead to a cure for cystic fibrosis within 15 years, with CRISPR-Cas9 being the most likely genetic tool for this purpose.

Future of genetic therapies for rare genetic diseases: what to expect for the next 15 years?

Introduction

Rare genetic diseases affect millions of people worldwide. Most of them are caused by defective genes that impair quality of life and can lead to premature death. As genetic therapies aim to fix or replace defective genes, they are considered the most promising treatment for rare genetic diseases. Yet, as these therapies are still under development, it is still unclear whether they will be successful in treating these diseases. This study aims to address this gap by assessing researchers' opinions on the future of genetic therapies for the treatment of rare genetic diseases.

Methods

We conducted a global cross-sectional web-based survey of researchers who recently authored peer-reviewed articles related to rare genetic diseases.

Results

We assessed the opinions of 1430 researchers with high and good knowledge about genetic therapies for the treatment of rare genetic diseases. Overall, the respondents believed that genetic therapies would be the standard of care for rare genetic diseases before 2036, leading to cures after this period. CRISPR-Cas9 was considered the most likely approach to fixing or replacing defective genes in the next 15 years. The respondents with good knowledge believed that genetic therapies would only have long-lasting effects after 2036, while those with high knowledge were divided on this issue. The respondents with good knowledge on the subject believed that non-viral vectors are more likely to be successful in fixing or replacing defective genes in the next 15 years, while most of the respondents with high knowledge believed viral vectors would be more successful.

Conclusion

Overall, the researchers who participated in this study expect that in the future genetic therapies will greatly benefit the treatment of patients with rare genetic diseases.

The fetus in the age of the genome

Due to a number of recent achievements, the field of prenatal medicine is now on the verge of a profound transformation into prenatal genomic medicine. This transformation is expected to not only substantially expand the spectrum of prenatal diagnostic and screening possibilities, but finally also to advance fetal care and the prenatal management of certain fetal diseases and malformations. It will come along with new and profound challenges for the normative framework and clinical care pathways in prenatal (and reproductive) medicine. To adequately address the potential ethically challenging aspects without discarding the obvious benefits, several agents are required to engage in different debates. The permissibility of the sequencing of the whole fetal exome or genome will have to be examined from a philosophical and legal point of view, in particular with regard to conflicts with potential rights of future children. A second requirement is a societal debate on the question of priority setting and justice in relation to prenatal genomic testing. Third, a professional-ethical debate and positioning on the goal of prenatal genomic testing and a consequential re-structuring of clinical care pathways seems to be important. In all these efforts, it might be helpful to envisage the unborn rather not as a fetus, not as a separate moral subject and a second "patient", but in its unique physical connection with the pregnant woman, and to accept the moral quandaries implicitly given in this situation.

Die Rechte zukünftiger Kinder im Kontext pränataler Diagnostik

Das Gendiagnostikgesetz (GenDG) verbietet seit 2010 die pränatale Diagnostik spätmanifestierender Erkrankungen (§ 15(2) GenDG). In seiner Begründung bezog sich der Gesetzgeber in Analogie zu internationalen Empfehlungen für den pädiatrischen Bereich vor allem auf das Recht des heranwachsenden Kindes bzw. des späteren Erwachsenen auf Nichtwissen. Mit diesem gesetzlichen Verbot hat Deutschland einen viel diskutierten Sonderweg in der Regulierung genetischer Pränataldiagnostik eingeschlagen. Seither jedoch hat sich nicht nur die Perspektive auf prädiktive Testungen im Kindesalter verändert. In zunehmendem Maße generieren auf das gesamte Genom abzielende Diagnostikangebote auch andere vorgeburtlich genetische Informationen, die – in ähnlicher Weise wie diejenigen zu spätmanifestierenden Erkrankungen eine potenzielle Gefahr für das Recht auf Nichtwissen der späteren Person darstellen. Es soll daher im Rahmen dieses Beitrages überprüft werden, inwiefern das deutsche Diagnostikverbot und dessen Bezug auf das Recht auf Nichtwissen des späteren Kindes eine tragfähige Basis zur Regulierung gendiagnostischer Untersuchungen in der Pränatalmedizin insgesamt darstellt bzw. zukünftig darstellen kann.

Untersucht wird der Argumentationsgang des Diagnostikverbotes im Hinblick auf spätmanifestierende Erkrankungen vor dem Hintergrund der Entwicklungen in der prädiktiven (genomischen) Diagnostik. Eine Analyse des normativen Begründungsrahmens zeigt, dass nach wie vor deutlicher Klärungsbedarf hinsichtlich der philosophisch-ethischen Fundierung wie auch hinsichtlich der Interpretation eines Rechts auf Nichtwissen eines (zukünftigen) Kindes im Kontext von genetischer Diagnostik besteht. Darüber hinaus müssen auch Interessen des (zukünftigen) Kindes an eventuell möglich werdender pränataler Behandlung oder Prävention von Erkrankungen in die Abwägung miteinbezogen werden.

Um zukünftigen Herausforderungen genomischer Pränataldiagnostik und -therapie begegnen zu können, müsste dringend geklärt werden, inwiefern Rechte zukünftiger Personen tatsächlich in der speziellen Situation der Schwangerschaft relevant sein können und mit welchen Pflichten diese für den Gesetzgeber, aber insbesondere auch für zukünftige Eltern und Ärzte einhergehen. Der Menschenrechtsdiskurs könnte hierfür eine tragfähige Basis und hilfreiche Strategien liefern.

Single-Dose Lentiviral Mediated Gene Therapy Recovers CFTR Function in Cystic Fibrosis Knockout Rats

Cystic fibrosis (CF) is a genetic disease caused by mutations in the CF transmembrane conductance regulator (CFTR) gene, resulting in defective ion transport in the airways. Addition of a functioning CFTR gene into affected airway cells has the potential to be an effective treatment for lung disease. The therapeutic efficacy of airway gene transfer can be quantified in animal models by assessing ion transport in the treated nasal epithelium using the nasal potential difference (PD) measurement technique. The nasal PD technique is routinely used in CF mice, however when applied to a recently developed CF rat model those animals did not tolerate the initial nasal PD assessment, therefore the procedure was firstly optimised in rats. This study evaluated the effect of lentiviral (LV)-mediated CFTR airway gene delivery on nasal PD in a CFTR knockout rat model. LV gene vector containing the CFTR gene tagged with a V5 epitope tag (LV-V5-CFTR) was delivered to the nasal epithelium of CF rats, and one week later nasal PD was analysed. This study demonstrated for the first time that LV-V5-CFTR treatment produced a mean correction of 46% towards wild-type chloride response in treated CF rats. Transduced cells were subsequently identifiable using V5 immunohistochemical staining. These findings in the nose validate the use of airway gene therapy for future lung based experiments.

On the Corner of Models and Cure: Gene Editing in Cystic Fibrosis

Cystic fibrosis (CF) is a severe genetic disease for which curative treatment is still lacking. Next generation biotechnologies and more efficient cell-based and in vivo disease models are accelerating the development of novel therapies for CF. Gene editing tools, like CRISPR-based systems, can be used to make targeted modifications in the genome, allowing to correct mutations directly in the Cystic Fibrosis Transmembrane conductance Regulator (CFTR) gene. Alternatively, with these tools more relevant disease models can be generated, which in turn will be invaluable to evaluate novel gene editing-based therapies for CF. This critical review offers a comprehensive description of currently available tools for genome editing, and the cell and animal models which are available to evaluate them. Next, we will give an extensive overview of proof-of-concept applications of gene editing in the field of CF. Finally, we will touch upon the challenges that need to be addressed before these proof-of-concept studies can be translated towards a therapy for people with CF.

Animal models for cystic fibrosis: a systematic search and mapping review of the literature. Part 2: nongenetic models

Various animal models are available to study cystic fibrosis (CF). These models may help to enhance our understanding of the pathology and contribute to the development of new treatments. We systematically searched all publications on CF animal models. Because of the large number of models retrieved, we split this mapping review into two parts. Previously, we presented the genetic CF animal models. In this paper we present the nongenetic CF animal models. While genetic animal models may, in theory, be preferable for genetic diseases, the phenotype of a genetic model does not automatically resemble human disease. Depending on the research question, other animal models may thus be more informative.We searched Pubmed and Embase and identified 12,303 unique publications (after duplicate removal). All references were screened for inclusion by two independent reviewers. The genetic animal models for CF (from 636 publications) were previously described. The non-genetic CF models (from 189 publications) are described in this paper, grouped by model type: infection-based, pharmacological, administration of human materials, xenografts and other. As before for the genetic models, an overview of basic model characteristics and outcome measures is provided. This CF animal model overview can be the basis for an objective, evidence-based model choice for specific research questions. Besides, it can help to retrieve relevant background literature on outcome measures of interest.

Rewriting CFTR to cure cystic fibrosis

Cystic fibrosis (CF) is an autosomal recessive monogenic disease caused by mutations in the Cystic Fibrosis Transmembrane conductance Regulator (CFTR) gene. Although F508del is the most frequent mutation, there are in total 360 confirmed disease-causing CFTR mutations, impairing CFTR production, function and stability. Currently, the only causal treatments available are CFTR correctors and potentiators that directly target the mutant protein. While these pharmacological advances and better symptomatic care have improved life expectancy of people with CF, none of these treatments provides a cure. The discovery and development of programmable nucleases, in particular CRISPR nucleases and derived systems, rekindled the field of CF gene therapy, offering the possibility of a permanent correction of the CFTR gene. In this review we will discuss different strategies to restore CFTR function via gene editing correction of CFTR mutations or enhanced CFTR expression, and address how best to deliver these treatments to target cells.

Current and novel therapeutic strategies for the management of cystic fibrosis

Introduction: Cystic fibrosis (CF), is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene and affects thousands of people throughout the world. Lung disease is the leading cause of death in CF patients. Despite the advances in treatments, the management of CF mainly targets symptoms. Recent CFTR modulators however target common mutations in patients, alleviating symptoms of CF. Unfortunately, there is still no approved treatments for patients with rare mutations to date.Areas covered: This paper reviews current treatments of CF that mitigate symptoms and target genetic defects. The use of gene and drug delivery systems such as viral or non-viral vectors and nano-compounds to enhance CFTR expression and the activity of antimicrobials against chronic pulmonary infections respectively, will also be discussed.Expert opinion: Nano-compounds tackle biological barriers to drug delivery and revitalize antimicrobials, anti-inflammatory drugs and even genes delivery to CF patients. Gene therapy and gene editing are of particular interest because they have the potential to directly target genetic defects. Nanoparticles should be formulated to more specifically target epithelial cells, and biofilms. Finally, the development of more potent gene vectors to increase the duration of gene expression and reduce inflammation is a promising strategy to eventually cure CF.

Allele specific repair of splicing mutations in cystic fibrosis through AsCas12a genome editing

Cystic fibrosis (CF) is an autosomal recessive disease caused by mutations in the CFTR gene. The 3272-26A>G and 3849+10kbC>T CFTR mutations alter the correct splicing of the CFTR gene, generating new acceptor and donor splice sites respectively. Here we develop a genome editing approach to permanently correct these genetic defects, using a single crRNA and the Acidaminococcus sp. BV3L6, AsCas12a. This genetic repair strategy is highly precise, showing very strong discrimination between the wild-type and mutant sequence and a complete absence of detectable off-targets. The efficacy of this gene correction strategy is verified in intestinal organoids and airway epithelial cells derived from CF patients carrying the 3272-26A>G or 3849+10kbC>T mutations, showing efficient repair and complete functional recovery of the CFTR channel. These results demonstrate that allele-specific genome editing with AsCas12a can correct aberrant CFTR splicing mutations, paving the way for a permanent splicing correction in genetic diseases.

Innovative Therapeutic Strategies for Cystic Fibrosis: Moving Forward to CRISPR Technique

One of the most revolutionary technologies in recent years in the field of molecular biology is CRISPR-Cas9. CRISPR technology is a promising tool for gene editing that provides researchers the opportunity to easily alter DNA sequences and modify gene function. Its many potential applications include correcting genetic defects, treating and preventing the spread of diseases. Cystic fibrosis (CF) is one of the most common lethal genetic diseases caused by mutations in the CF transmembrane conductance regulator (CFTR) gene. Although CF is an old acquaintance, there is still no effective/resolutive cure. Life expectancy has improved thanks to the combination of various treatments, but it is generally below average. Recently, a significant number of additional key medications have become licensed in Europe for the CF treatment including CFTR modulators. But innovative genomically-guided therapies have begun for CF and it is predictable that this will lead to rapid improvements in CF clinical disease and survival in the next decades. In this way, CRISPR-Cas9 approach may represent a valid tool to repair the CFTR mutation and hopeful results were obtained in tissue and animal models of CF disease.