CAR-T lymphocyte-based cell therapies; mechanistic substantiation, applications and biosafety enhancement with suicide genes: new opportunities to melt side effects.

Immunotherapy has made significant strides in cancer treatment with strategies like checkpoint blockade antibodies and adoptive T cell transfer. Chimeric antigen receptor T cells (CAR-T) have emerged as a promising approach to combine these strategies and overcome their limitations. This review explores CAR-T cells as a living drug for cancer treatment. CAR-T cells are genetically engineered immune cells designed to target and eliminate tumor cells by recognizing specific antigens. The study involves a comprehensive literature review on CAR-T cell technology, covering structure optimization, generations, manufacturing processes, and gene therapy strategies. It examines CAR-T therapy in haematologic cancers and solid tumors, highlighting challenges and proposing a suicide gene-based mechanism to enhance safety. The results show significant advancements in CAR-T technology, particularly in structure optimization and generation. The manufacturing process has improved for broader clinical application. However, a series of inherent challenges and side effects still need to be addressed. In conclusion, CAR-T cells hold great promise for cancer treatment, but ongoing research is crucial to improve efficacy and safety for oncology patients. The proposed suicide gene-based mechanism offers a potential solution to mitigate side effects including cytokine release syndrome (the most common toxic side effect of CAR-T therapy) and the associated neurotoxicity.

Safety of non-replicative and oncolytic replication-selective HSV vectors.

Herpes simplex virus type 1 (HSV-1) is a DNA virus and human pathogen used to construct promising therapeutic vectors. HSV-1 vectors fall into two classes: replication-selective oncolytic vectors for cancer therapy and defective non-replicative vectors for gene therapy. Vectors from each class can accommodate ≥30 kb of inserts, have been approved clinically, and demonstrate a relatively benign safety profile. Despite oncolytic HSV (oHSV) replication in tumors and elicited immune responses, the virus is well tolerated in cancer patients. Current non-replicative vectors elicit only limited immune responses. Seropositivity and immune responses against HSV-1 do not eliminate either the vector or infected cells, and the vectors can therefore be re-administered. In this review we highlight vectors that have been translated to the clinic and host-virus immune interactions that impact on the safety and efficacy of HSVs.

Gene Editing for CEP290-Associated Retinal Degeneration.

BACKGROUND: CEP290-associated inherited retinal degeneration causes severe early-onset vision loss due to pathogenic variants in CEP290. EDIT-101 is a clustered regularly interspaced short palindromic repeats (CRISPR)-CRISPR-associated protein 9 (Cas9) gene-editing complex designed to treat inherited retinal degeneration caused by a specific damaging variant in intron 26 of CEP290 (IVS26 variant). METHODS: We performed a phase 1-2, open-label, single-ascending-dose study in which persons 3 years of age or older with CEP290-associated inherited retinal degeneration caused by a homozygous or compound heterozygous IVS26 variant received a subretinal injection of EDIT-101 in the worse (study) eye. The primary outcome was safety, which included adverse events and dose-limiting toxic effects. Key secondary efficacy outcomes were the change from baseline in the best corrected visual acuity, the retinal sensitivity detected with the use of full-field stimulus testing (FST), the score on the Ora-Visual Navigation Challenge mobility test, and the vision-related quality-of-life score on the National Eye Institute Visual Function Questionnaire-25 (in adults) or the Children's Visual Function Questionnaire (in children). RESULTS: EDIT-101 was injected in 12 adults 17 to 63 years of age (median, 37 years) at a low dose (in 2 participants), an intermediate dose (in 5), or a high dose (in 5) and in 2 children 9 and 14 years of age at the intermediate dose. At baseline, the median best corrected visual acuity in the study eye was 2.4 log10 of the minimum angle of resolution (range, 3.9 to 0.6). No serious adverse events related to the treatment or procedure and no dose-limiting toxic effects were recorded. Six participants had a meaningful improvement from baseline in cone-mediated vision as assessed with the use of FST, of whom 5 had improvement in at least one other key secondary outcome. Nine participants (64%) had a meaningful improvement from baseline in the best corrected visual acuity, the sensitivity to red light as measured with FST, or the score on the mobility test. Six participants had a meaningful improvement from baseline in the vision-related quality-of-life score. CONCLUSIONS: The safety profile and improvements in photoreceptor function after EDIT-101 treatment in this small phase 1-2 study support further research of in vivo CRISPR-Cas9 gene editing to treat inherited retinal degenerations due to the IVS26 variant of CEP290 and other genetic causes. (Funded by Editas Medicine and others; BRILLIANCE ClinicalTrials.gov number, NCT03872479.).

[How safe is gene therapy? : Second death after Duchenne therapy]. / Wie sicher ist die Gentherapie? : Zweiter Todesfall nach Therapie der Duchenne-Muskeldystrophie.

BACKGROUND: Duchenne muscular dystrophy (DMD) is a severe monogenic hereditary disease with early manifestation and a progressive course. Treatment options have so far been limited. Gene therapy opens up new options for DMD patients. OBJECTIVES: Against the background of a further death following DMD gene therapy, the side effects and risks of the gene therapeutics already approved or undergoing clinical trials will be evaluated and alternative gene therapeutics will be described. Based thereon, the future of DMD gene therapy will be discussed. CURRENT DATA: For the first time, in June 2023, delandistrogene moxeparvovec (SRP-9001), a gene replacement therapy based on an adeno-associated virus (AAV) vector, was approved in the USA for children aged 4-5 years with DMD. Other promising gene therapies are in preclinical development or clinical trials, including CRISPR/Cas9-mediated strategies to restore dystrophin expression. Two deaths following DMD gene therapy with high-dose AAV vectors were attributed to AAV-mediated immune responses. The pre-existing disease underlying the therapy is most likely involved in the fatal AAV toxicity. CONCLUSIONS: Although gene therapy applications of AAV vectors are generally considered safe, the systemic administration of high vector doses can lead to severe side effects with a potentially fatal outcome in individual patients, especially after activation of the immune system. In the future, new methods for immunosuppression, reduction of AAV dose and alternative vectors will therefore increasingly come to the fore.

The science and practice of current environmental risk assessment for gene therapy: a review.

Gene therapy is a fast-growing field showing great potential to treat genetic diseases and cancer. With accelerating gene therapy development and approval, their environment risk assessment (ERA) becomes increasingly important. An ERA is an assessment of the risks to human health and the environment upon exposure to a medicinal product as the result of its release during clinical development or after entering the market. Because ERA is an important component of regulatory submission, drug developers must perform a robust assessment to ensure the safety of unintended persons, animal, plants, microorganisms and environment at large. Global regulations on gene therapy ERA continue to evolve. Gene therapy ERAs are carried out according to general principles as provided in regulatory guidelines for application of clinical trials and marketing authorizations. The current review intends to summarize regulations and content requirements on gene therapy ERA in European Union, the USA and Japan. The approved gene therapy products by EMA and US Food and Drug Administration are analyzed for the critical aspects of their ERAs to provide the current status and practice of gene therapy ERAs by drug developers. For this purpose, the main contents of these gene therapy ERAs are summarized. Critical safety factors of gene therapy ERAs are described. With more experience and knowledge to be accumulated, gene therapy ERAs are expected to be less challenging with commonly used viral vectors.

Angiogenic Gene Therapy for Refractory Angina: Results of the EXACT Phase 2 Trial.

BACKGROUND: XC001 is a novel adenoviral-5 vector designed to express multiple isoforms of VEGF (vascular endothelial growth factor) and more safely and potently induce angiogenesis. The EXACT trial (Epicardial Delivery of XC001 Gene Therapy for Refractory Angina Coronary Treatment) assessed the safety and preliminary efficacy of XC001 in patients with no option refractory angina. METHODS: In this single-arm, multicenter, open-label trial, 32 patients with no option refractory angina received a single treatment of XC001 (1×1011 viral particles) via transepicardial delivery. RESULTS: There were no severe adverse events attributed to the study drug. Twenty expected severe adverse events in 13 patients were related to the surgical procedure. Total exercise duration increased from a mean±SD of 359.9±105.55 seconds at baseline to 448.2±168.45 (3 months), 449.2±175.9 (6 months), and 477.6±174.7 (12 months; +88.3 [95% CI, 37.1-139.5], +84.5 [95% CI, 34.1-134.9], and +115.5 [95% CI, 59.1-171.9]). Total myocardial perfusion deficit on positron emission tomography imaging decreased by 10.2% (95% CI, -3.1% to 23.5%), 14.3% (95% CI, 2.8%-25.7%), and 10.2% (95% CI, -0.8% to -21.2%). Angina frequency decreased from a mean±SD 12.2±12.5 episodes to 5.2±7.2 (3 months), 5.1±7.8 (6 months), and 2.7±4.8 (12 months), with an average decrease of 7.7 (95% CI, 4.1-11.3), 6.6 (95% CI, 3.5-9.7), and 8.8 (4.6-13.0) episodes at 3, 6, and 12 months. Angina class improved in 81% of participants at 6 months. CONCLUSIONS: XC001 administered via transepicardial delivery is safe and generally well tolerated. Exploratory improvements in total exercise duration, ischemic burden, and subjective measures support a biologic effect sustained to 12 months, warranting further investigation. REGISTRATION: URL: https://www.clinicaltrials.gov; Unique identifier: NCT04125732.

The FDA and Gene Therapy for Duchenne Muscular Dystrophy.

This Viewpoint examines the appropriateness of FDA accelerated approval of novel gene therapies to treat boys with Duchenne muscular dystrophy following clinical trials with surrogate outcomes that did not demonstrate net benefits.

Progranulin AAV gene therapy for frontotemporal dementia: translational studies and phase 1/2 trial interim results.

GRN mutations cause progranulin haploinsufficiency, which eventually leads to frontotemporal dementia (FTD-GRN). PR006 is an investigational gene therapy delivering the granulin gene (GRN) using an adeno-associated virus serotype 9 (AAV9) vector. In non-clinical studies, PR006 transduced neurons derived from induced pluripotent stem cells of patients with FTD-GRN, resulted in progranulin expression and improvement of lipofuscin, lysosomal and neuroinflammation pathologies in Grn-knockout mice, and was well tolerated except for minimal, asymptomatic dorsal root ganglionopathy in non-human primates. We initiated a first-in-human phase 1/2 open-label trial. Here we report results of a pre-specified interim analysis triggered with the last treated patient of the low-dose cohort (n = 6) reaching the 12-month follow-up timepoint. We also include preliminary data from the mid-dose cohort (n = 7). Primary endpoints were safety, immunogenicity and change in progranulin levels in cerebrospinal fluid (CSF) and blood. Secondary endpoints were Clinical Dementia Rating (CDR) plus National Alzheimer's Disease Coordinating Center (NACC) Frontotemporal Lobar Degeneration (FTLD) rating scale and levels of neurofilament light chain (NfL). One-time administration of PR006 into the cisterna magna was generally safe and well tolerated. All patients developed treatment-emergent anti-AAV9 antibodies in the CSF, but none developed anti-progranulin antibodies. CSF pleocytosis was the most common PR006-related adverse event. Twelve serious adverse events occurred, mostly unrelated to PR006. Deep vein thrombosis developed in three patients. There was one death (unrelated) occurring 18 months after treatment. CSF progranulin increased after PR006 treatment in all patients; blood progranulin increased in most patients but only transiently. NfL levels transiently increased after PR006 treatment, likely reflecting dorsal root ganglia toxicity. Progression rates, based on the CDR scale, were within the broad ranges reported for patients with FTD. These data provide preliminary insights into the safety and bioactivity of PR006. Longer follow-up and additional studies are needed to confirm the safety and potential efficacy of PR006. ClinicalTrials.gov identifier: NCT04408625 .

Non-clinical safety assessment of novel drug modalities: Genome safety perspectives on viral-, nuclease- and nucleotide-based gene therapies.

Gene therapies have emerged as promising treatments for various conditions including inherited diseases as well as cancer. Ensuring their safe clinical application requires the development of appropriate safety testing strategies. Several guidelines have been provided by health authorities to address these concerns. These guidelines state that non-clinical testing should be carried out on a case-by-case basis depending on the modality. This review focuses on the genome safety assessment of frequently used gene therapy modalities, namely Adeno Associated Viruses (AAVs), Lentiviruses, designer nucleases and mRNAs. Important safety considerations for these modalities, amongst others, are vector integrations into the patient genome (insertional mutagenesis) and off-target editing. Taking into account the constraints of in vivo studies, health authorities endorse the development of novel approach methodologies (NAMs), which are innovative in vitro strategies for genotoxicity testing. This review provides an overview of NAMs applied to viral and CRISPR/Cas9 safety, including next generation sequencing-based methods for integration site analysis and off-target editing. Additionally, NAMs to evaluate the oncogenicity risk arising from unwanted genomic modifications are discussed. Thus, a range of promising techniques are available to support the safe development of gene therapies. Thorough validation, comparisons and correlations with clinical outcomes are essential to identify the most reliable safety testing strategies. By providing a comprehensive overview of these NAMs, this review aims to contribute to a better understanding of the genome safety perspectives of gene therapies.

Which patients should be considered for gene therapy.

Gene therapy for haemophilia, utilizing adeno-associated viral vectors (AAVs) and coagulation factor genes, have demonstrated promising results, leading to recent approvals and introduction of the first gene therapy products into clinical practice. For successful and safe use, there are predefined inclusion and exclusion criteria, and the treatment process and associated risks should be thoroughly understood and long-term safety and efficacy carefully evaluated during follow up. As gene therapy becomes more accessible outside of clinical study centers, continuous evaluation of patient eligibility for subsequent AAV-based treatments becomes essential. Thorough evaluation of factors such as liver condition, anti-AAV status, and medical history ensures that gene therapy maximizing benefits while minimizing risks. Apart from fulfilling the established inclusion and exclusion criteria, the success of gene therapy is greatly influenced by the motivation and willingness of patients to accept temporary constraints, such as regular laboratory monitoring, potential use of immunosuppressants, and thorough documentation. Furthermore, various patient-related factors play a significant role in the management and outcomes of gene therapy, making a comprehensive evaluation essential. With the accumulation of more data, there is potential for the expansion of certain inclusion criteria, which may allow for a larger number of eligible patients to benefit from gene therapy. Empowering patients through shared decision-making enables them to thoroughly consider the therapy's potential benefits and risks.

Hepatitis after gene therapy, what are the possible causes?

Hepatitis is a common adverse event following gene therapy for haemophilia, often associated with a loss of transgene expression. Investigating the potential causes and implications of this is crucial for the overall success of treatment. Gene therapy trials using adeno-associated virus (AAV) vectors have demonstrated promising results marked by increases in factor FVIII and FIX levels and reductions in episodes of bleeding. However, hepatocellular injury characterised by elevations in alanine aminotransferases (ALT) has been noted. This liver injury is typically transient and asymptomatic, posing challenges in determining its clinical significance. Proposed causes encompass immune-mediated responses, notably T cell cytotoxicity in response to the AAV vector, direct liver injury from the viral capsid or transcribed protein via the unfolded protein response and pre-existing liver conditions. Liver biopsy data conducted years post-gene therapy infusion has shown sinusoidal infiltration without significant inflammation. The overall safety profile of gene therapy remains favourable with no evidence drug-induced liver injury (DILI) based on Hy's Law criteria. Essential pre-therapy monitoring and identifying patients at high risk of liver injury should involve liver function tests and non-invasive fibroscans, while novel blood-based biomarkers are under exploration. Further research is required to comprehend the mechanisms underlying transaminitis, loss of transgene expression and long-term effects on the liver, providing insights for optimising gene therapy for haemophilia.

LOAd703, an oncolytic virus-based immunostimulatory gene therapy, combined with chemotherapy for unresectable or metastatic pancreatic cancer (LOKON001): results from arm 1 of a non-randomised, single-centre, phase 1/2 study.

BACKGROUND: Pancreatic ductal adenocarcinoma is characterised by low immunogenicity and an immunosuppressive tumour microenvironment. LOAd703, an oncolytic adenovirus with transgenes encoding TMZ-CD40L and 4-1BBL, lyses cancer cells selectively, activates cytotoxic T cells, and induces tumour regression in preclinical models. The aim of this study was to evaluate the safety and feasibility of combining LOAd703 with chemotherapy for advanced pancreatic ductal adenocarcinoma. METHODS: LOKON001 was a non-randomised, phase 1/2 study conducted at the Dan L Duncan Comprehensive Cancer Center, Baylor College of Medicine, Houston, TX, USA, and consisted of two arms conducted sequentially; the results of arm 1 are presented here. In arm 1, patients 18 years or older with previously treated or treatment-naive unresectable or metastatic pancreatic ductal adenocarcinoma were treated with standard 28-day cycles of intravenous nab-paclitaxel 125 mg/m2 plus gemcitabine 1000 mg/m2 (up to 12 cycles) and intratumoural injections of LOAd703 every 2 weeks. Patients were assigned using Bayesian optimal interval design to receive 500 µL of LOAd703 at 5 × 1010 (dose 1), 1 × 1011 (dose 2), or 5 × 1011 (dose 3) viral particles per injection, injected endoscopically or percutaneously into the pancreatic tumour or a metastasis for six injections. The primary endpoints were safety and treatment-emergent immune response in patients who received at least one dose of LOAd703, and antitumour activity was a secondary endpoint. This study was registered with ClinicalTrials.gov, NCT02705196, arm 2 is ongoing and open to new participants. FINDINGS: Between Dec 2, 2016, and Oct 17, 2019, 23 patients were assessed for eligibility, leading to 22 patients being enrolled. One patient withdrew consent, resulting in 21 patients (13 [62%] men and eight [38%] women) assigned to a dose group (three to dose 1, four to dose 2, and 14 to dose 3). 21 patients were evaluable for safety. Median follow-up time was 6 months (IQR 4-10), and data cutoff was Jan 5, 2023. The most common treatment-emergent adverse events overall were anaemia (96 [8%] of 1237 events), lymphopenia (86 [7%] events), hyperglycaemia (70 [6%] events), leukopenia (63 [5%] events), hypertension (62 [5%] events), and hypoalbuminaemia (61 [5%] events). The most common adverse events attributed to LOAd703 were fever (14 [67%] of 21 patients), fatigue (eight [38%]), chills (seven [33%]), and elevated liver enzymes (alanine aminotransferase in five [24%], alkaline phosphatase in four [19%], and aspartate aminotransferase in four [19%]), all of which were grade 1-2, except for a transient grade 3 aminotransferase elevation occurring at dose 3. A maximum tolerated dose was not reached, thereby establishing dose 3 as the highest-evaluated safe dose when combined with nab-paclitaxel plus gemcitabine. Proportions of CD8+ effector memory cells and adenovirus-specific T cells increased after LOAd703 injections in 15 (94%) of 16 patients for whom T-cell assays could be performed. Eight (44%, 95% CI 25-66) of 18 patients evaluable for activity had an objective response. INTERPRETATION: Combining LOAd703 with nab-paclitaxel plus gemcitabine in patients with advanced pancreatic ductal adenocarcinoma was feasible and safe. To build upon this novel chemoimmunotherapeutic approach, arm 2 of LOKON001, which combines LOAd703, nab-paclitaxel plus gemcitabine, and atezolizumab, is ongoing. FUNDING: Lokon Pharma, the Swedish Cancer Society, and the Swedish Research Council.

The menace of severe adverse events and deaths associated with viral gene therapy and its potential solution.

Over the past decade, in vivo gene replacement therapy has significantly advanced, resulting in market approval of numerous therapeutics predominantly relying on adeno-associated viral vectors (AAV). While viral vectors have undeniably addressed several critical healthcare challenges, their clinical application has unveiled a range of limitations and safety concerns. This review highlights the emerging challenges in the field of gene therapy. At first, we discuss both the role of biological barriers in viral gene therapy with a focus on AAVs, and review current landscape of in vivo human gene therapy. We delineate advantages and disadvantages of AAVs as gene delivery vehicles, mostly from the safety perspective (hepatotoxicity, cardiotoxicity, neurotoxicity, inflammatory responses etc.), and outline the mechanisms of adverse events in response to AAV. Contribution of every aspect of AAV vectors (genomic structure, capsid proteins) and host responses to injected AAV is considered and substantiated by basic, translational and clinical studies. The updated evaluation of recent AAV clinical trials and current medical experience clearly shows the risks of AAVs that sometimes overshadow the hopes for curing a hereditary disease. At last, a set of established and new molecular and nanotechnology tools and approaches are provided as potential solutions for mitigating or eliminating side effects. The increasing number of severe adverse reactions and, sadly deaths, demands decisive actions to resolve the issue of immune responses and extremely high doses of viral vectors used for gene therapy. In response to these challenges, various strategies are under development, including approaches aimed at augmenting characteristics of viral vectors and others focused on creating secure and efficacious non-viral vectors. This comprehensive review offers an overarching perspective on the present state of gene therapy utilizing both viral and non-viral vectors.

Intrathecal Gene Therapy for Giant Axonal Neuropathy.

BACKGROUND: Giant axonal neuropathy is a rare, autosomal recessive, pediatric, polysymptomatic, neurodegenerative disorder caused by biallelic loss-of-function variants in GAN, the gene encoding gigaxonin. METHODS: We conducted an intrathecal dose-escalation study of scAAV9/JeT-GAN (a self-complementary adeno-associated virus-based gene therapy containing the GAN transgene) in children with giant axonal neuropathy. Safety was the primary end point. The key secondary clinical end point was at least a 95% posterior probability of slowing the rate of change (i.e., slope) in the 32-item Motor Function Measure total percent score at 1 year after treatment, as compared with the pretreatment slope. RESULTS: One of four intrathecal doses of scAAV9/JeT-GAN was administered to 14 participants - 3.5×1013 total vector genomes (vg) (in 2 participants), 1.2×1014 vg (in 4), 1.8×1014 vg (in 5), and 3.5×1014 vg (in 3). During a median observation period of 68.7 months (range, 8.6 to 90.5), of 48 serious adverse events that had occurred, 1 (fever) was possibly related to treatment; 129 of 682 adverse events were possibly related to treatment. The mean pretreatment slope in the total cohort was -7.17 percentage points per year (95% credible interval, -8.36 to -5.97). At 1 year after treatment, posterior mean changes in slope were -0.54 percentage points (95% credible interval, -7.48 to 6.28) with the 3.5×1013-vg dose, 3.23 percentage points (95% credible interval, -1.27 to 7.65) with the 1.2×1014-vg dose, 5.32 percentage points (95% credible interval, 1.07 to 9.57) with the 1.8×1014-vg dose, and 3.43 percentage points (95% credible interval, -1.89 to 8.82) with the 3.5×1014-vg dose. The corresponding posterior probabilities for slowing the slope were 44% (95% credible interval, 43 to 44); 92% (95% credible interval, 92 to 93); 99% (95% credible interval, 99 to 99), which was above the efficacy threshold; and 90% (95% credible interval, 89 to 90). Between 6 and 24 months after gene transfer, sensory-nerve action potential amplitudes increased, stopped declining, or became recordable after being absent in 6 participants but remained absent in 8. CONCLUSIONS: Intrathecal gene transfer with scAAV9/JeT-GAN for giant axonal neuropathy was associated with adverse events and resulted in a possible benefit in motor function scores and other measures at some vector doses over a year. Further studies are warranted to determine the safety and efficacy of intrathecal AAV-mediated gene therapy in this disorder. (Funded by the National Institute of Neurological Disorders and Stroke and others; ClinicalTrials.gov number, NCT02362438.).

Recent developments in gene therapy research in India.

Inherited genetic disorders are progressive in nature and lead to organ dysfunction or death in severe cases. At present, there are no permanent treatment options for >95% of inherited disorders. Different modes of inheritance, type of gene(s) involved, and population-based variations add further complexity to finding suitable cures for approximately 400 million patients worldwide. Gene therapy is a very promising molecular technique for the treatment of rare genetic disorders. Gene therapy functions on the basis of restoration, replacement, inhibition, and, most recently, editing of gene(s) to rescue the disease phenotype. Recent reports show that increasing numbers of gene therapy clinical trials are using viral vectors (64.2%) when compared with non-viral vectors. Rapid development of efficient viral vector systems like the adeno-associated virus (AAV) and lentivirus has significantly contributed to this progress. Notably, AAV-mediated gene therapy has shown high potential for genetic disease treatment as evident from recent clinical trials for the eye (NCT00999609), blood (NCT00979238), and neuro-muscular systems (NCT02122952). Safety and efficacy are the two most critical features required for vector(s) to qualify for pre-clinical and clinical trial approval. The process of clinical-grade vector production, evaluation, and approvals for gene therapy products requires significant technological development, knowledge enhancement, and large financial investments. Additionally, trained manpower is required to meet the demands for constant technical innovation. These factors together contribute towards exorbitant prices for every dose of a gene therapy product and thus pose a challenge for the gene therapy field. The Indian subcontinent has traditionally lagged behind North America, Europe, Japan, and others in gene therapy clinical trials due to factors like inadequate industrial-scientific infrastructure, lack of accessible and organized patient databases, low financial investments, etc. However, over the last decade, increasing awareness of rare diseases, and international approvals of gene therapies such as Luxturna, Zolgensma, Hemgenix, etc., have spurred gene therapy development in India as well. In view of these advances, this article outlines gene therapy research, regulatory processes, and the launch of gene therapy clinical trials in India in the context of major developments worldwide. We briefly describe ongoing gene therapy research across Indian organizations and the nascent gene therapy product manufacturing. Further, we highlight the various initiatives from the medical and patient community to avail rehabilitation and gene therapy options. We briefly discuss the roles of regulatory agencies and guidelines for gene therapy clinical trials in India. We anticipate that this concise review will highlight the promise of gene therapy for the large population of rare disease patients in India.

Hematopoietic stem cell collection for sickle cell disease gene therapy.

PURPOSE OF REVIEW: Gene therapy for sickle cell disease (SCD) is advancing rapidly, with two transformative products recently approved by the US Food and Drug Administration and numerous others under study. All current gene therapy protocols require ex vivo modification of autologous hematopoietic stem cells (HSCs). However, several SCD-related problems impair HSC collection, including a stressed and damaged bone marrow, potential cytotoxicity by the major therapeutic drug hydroxyurea, and inability to use granulocyte colony stimulating factor, which can precipitate severe vaso-occlusive events. RECENT FINDINGS: Peripheral blood mobilization of HSCs using the CXCR4 antagonist plerixafor followed by apheresis collection was recently shown to be safe and effective for most SCD patients and is the current strategy for mobilizing HSCs. However, exceptionally large numbers of HSCs are required to manufacture an adequate cellular product, responses to plerixafor are variable, and most patients require multiple mobilization cycles, increasing the risk for adverse events. For some, gene therapy is prohibited by the failure to obtain adequate numbers of HSCs. SUMMARY: Here we review the current knowledge on HSC collection from individuals with SCD and potential improvements that may enhance the safety, efficacy, and availability of gene therapy for this disorder.

Complement System Response to Adeno-Associated Virus Vector Gene Therapy.

Adeno-associated virus (AAV) vectors represent a novel tool for the delivery of genetic therapeutics and enable the treatment of a wide range of diseases. Success of this new modality is challenged, however, by cases of immune-related toxicities that complicate the clinical management of patients and potentially limit the therapeutic efficacy of AAV gene therapy. While significant progress has been made to manage immune-related liver enzyme elevations following systemic AAV delivery in humans, recent clinical trials utilizing high vector doses have highlighted a new challenge to AAV gene transfer-activation of the complement system. While current in vitro models implicate AAV-specific antibodies in the initiation of the classical complement pathway, evidence from in vivo pre-clinical and clinical studies suggests that the alternative pathway also contributes to complement activation. A convergence of AAV-specific, environmental, and patient-specific factors shaping complement responses likely contributes to differential outcomes seen in clinical trials, from priming of the adaptive immune system to serious adverse events such as hepatotoxicity and thrombotic microangiopathy. Research focused on the interplay of patient-specific and AAV-related factors driving complement activation is needed to understand and identify critical components in the complement cascade to target and devise strategies to mitigate vector-related immune responses.

Recommendations for a minimum data set for monitoring gene therapy in hemophilia: communication from the ISTH SSC Working Group on Gene Therapy.

Independent data collection is crucial in addressing the challenges associated with gene therapy for hemophilia, which is a promising treatment option but requires careful monitoring and management of short-term and potential long-term safety concerns. The International Society on Thrombosis and Haemostasis has identified a minimum efficacy and safety data set included in the World Federation of Hemophilia Gene Therapy Registry that should be collected on a national basis at specific time points for each patient who has been treated with the gene therapy products. This Gene Therapy Minimum Data Set (GT-MDS) was developed to facilitate data collection and to ensure capturing the most relevant data and most known and unknown safety and efficacy parameters recently cited by the European Medicine Agencies. The concept of assembling a minimum data set is not about creating a new data set but rather about identifying a subset of critical and essential topics that should always be included. The GT-MDS is structured into 3 sections and comprises an abridged list of 6 topics during routine gene therapy follow-up, keeping the number of data points low but allowing for rapid and independent data evaluation. The World Federation of Hemophilia Gene Therapy Registry data set, developed by the World Federation of Hemophilia, the International Society on Thrombosis and Haemostasis, and other organizations, including industry partners in 2020, is comprehensive. The GT-MDS reports the minimum relevant information that should not be lost and is mandatory to be collected for all patients who undergo gene therapy. Therefore, the implementation of the gene therapy registry and the minimum data set empowers and enhances data collection at a global level.