Developing a second-generation clinical candidate AAV vector for gene therapy of familial hypercholesterolemia

Gene therapy for hypercholesterolemia offers the potential to sustainably ameliorate disease for life with a single dose. In this study, we demonstrate the combinatorial effects of codon and vector optimization, which significantly improve the efficacy of an adeno-associated virus (AAV) vector in the low-density lipoprotein receptor (LDLR)-deficient mouse model (Ldlr -/-, Apobec1 -/- double knockout [DKO]). This study investigated vector efficacy following the combination of intervening sequence 2 (IVS2) of the human beta-globin gene and codon optimization with the previously developed gain-of-function, human LDLR triple-mutant variant (hLDLR-L318D/K809R/C818A) in the treatment of homozygous familial hypercholesterolemia (HoFH). Vector doses as low as 3 × 1011 genome copies (GC)/kg achieved a robust reduction of serum low-density lipoprotein cholesterol (LDL-C) by 98% in male LDLR-deficient mice. Less efficient LDL-C reduction was observed in female mice, which was attributable to lower gene transfer efficiency in liver. We also observed persistent and stable transgene expression for 120 days, with LDL-C levels being undetectable in male DKO mice treated with the second-generation vector. In conclusion, codon and vector optimization enhanced transgene expression and reduced serum LDL-C levels effectively at a lower dose in LDLR-deficient mice. The second-generation clinical candidate vector we have developed has the potential to achieve therapeutic effects in HoFH patients.

Mental status and physical activity in patients with homozygous familial hypercholesterolemia: A subgroup analysis of a nationwide survey (A-HIT1 registry)

BACKGROUND

Homozygous familial hypercholesterolemia (HoFH) is a rare, life-threatening disease due to high serum low-density lipoprotein (LDL) cholesterol levels. LDL cholesterol-lowering interventions are fundamental for patients with HoFH.

OBJECTIVE

It was aimed to investigate the association between the mental status of patients with HoFH and healthy lifestyle behaviors.

METHODS

This subgroup analysis of the A-HIT1 population included the data of patients aged ≥18 years with a clinical diagnosis of HoFH undergoing therapeutic LDL apheresis. Besides the demographic and clinical characteristics of patients, healthy lifestyle behaviors were assessed, and psychiatric symptoms were screened by Symptom Check List (SCL-90-R).

RESULTS

The highest percentage for pathology was observed in dimensions of obsessive-compulsive, somatization, interpersonal sensitivity, and depression in SCL-90-R. Patients with any cardiovascular condition have more psychiatric symptoms in different fields of SCL-90-R. The outcomes of the correlative analysis indicated that lower the age of the first coronary event better the psychiatric status, probably denoting a better adaptation to disease and its treatment. Among 68 patients, 36 patients were not exercising regularly. Patients with regular physical activity had significantly lower scores in most dimensions of SCL-90-R and there was no association between regular physical activity and other investigated variables. The strongest predictor of regular exercising was global severity index of SCL-90-R.

CONCLUSION

In the HoFH population, there was a high prevalence of mental disturbances. Better psychiatric status was associated with regular exercising. Therefore, assessing the mental status of patients with HoFH and referring patients in need, to a psychiatrist, may improve the outcome of patients.

Case Report: Liver Transplantation in Homozygous Familial Hypercholesterolemia (HoFH)-Long-Term Follow-Up of a Patient and Literature Review

Homozygous familial hypercholesterolemia (HoFH) is a rare inherited metabolic disorder, frequently leading to an early cardiovascular death if not adequately treated. Since standard medications usually fail to reduce LDL-cholesterol (LDL-C) levels satisfactorily, LDL-apheresis is a mainstay of managing HoFH patients but, at the same time, very burdensome and suboptimally effective. Liver transplantation (LT) has been previously shown to be a promising alternative. We report on a 14 year-long follow-up after LT in a HoFH patient. At the age of 4, the patient was referred to our institution because of the gradually increasing number of xanthomas on the knees, elbows, buttocks, and later the homozygous mutation c.1754T>C (p.Ile585Thr) on the LDL-receptor gene was confirmed. Despite subsequent intensive treatment with the combination of diet, statins, bile acid sequestrant, probucol, and LDL-apheresis, the patient developed valvular aortic stenosis and aortic regurgitation by 12 years. At 16 years, the patient successfully underwent deceased-donor orthotopic LT. Nine years post-LT, we found total regression of the cutaneous xanthomas and atherosclerotic plaques and with normal endothelial function. Fourteen years post-LT, his clinical condition remained stable, but LDL-C levels have progressively risen. In addition, a systematic review of the literature and guidelines on the LT for HoFH patients was performed. Six of the 17 identified guidelines did not take LT as a treatment option in consideration at all. But still the majority of guidelines suggest LT as an exceptional therapeutic option or as the last resort option when all the other treatment options are inadequate or not tolerated. Most of the observed patients had some kind of cardiovascular disease before the LT. In 76% of LT, the cardiovascular burden did not progress after LT. According to our experience and in several other reported cases, the LDL-C levels are slowly increasing over time post LT. Most of the follow-up data were short termed; only a few case reports have followed patients for 10 or more years after LT. LT is a feasible therapeutic option for HoFH patients, reversing atherosclerotic changes uncontrollable by conservative therapy, thus importantly improving the HoFH patient's prognosis and quality of life.

Nonclinical Pharmacology/Toxicology Study of AAV8.TBG.mLDLR and AAV8.TBG.hLDLR in a Mouse Model of Homozygous Familial Hypercholesterolemia

The homozygous form of familial hypercholesterolemia (HoFH) is an excellent model for developing in vivo gene therapy in humans. The success of orthotropic liver transplantation in correcting the metabolic abnormalities in HoFH suggests that the correction of low-density lipoprotein receptor (LDLR) expression in hepatocytes via gene therapy should be sufficient for therapeutic efficacy. Vectors based on adeno-associated virus serotype 8 (AAV8) have been previously developed for liver-targeted gene therapy of a number of genetic diseases, including HoFH. In preparation for initiating a Phase 1 clinical trial of AAV8-mediated LDLR gene therapy for HoFH, a combined pharmacology/toxicology study was conducted in a mouse model of HoFH. No dose-limiting toxicities were found at or below 6.0 × 10¹³ GC/kg. Therefore, the maximally tolerated dose is greater than the highest dose that was tested. Mild and transient liver pathology was noted at the highest dose. Therefore, the no effect dose was greater than or equal to the middle dose of 7.5 × 10¹² GC/kg. The minimally effective dose was determined to be ≤7.5 × 10¹¹ GC/kg, based on stable reductions in cholesterol that were considered to be clinically significant. This translates to a therapeutic window of ≥80-fold for the treatment of HoFH.

Individual analysis of patients with HoFH participating in a phase 3 trial with lomitapide: The Italian cohort

BACKGROUND AND AIMS

The efficacy and safety of lomitapide as adjunct treatment for adults with homozygous familial hypercholesterolaemia (HoFH) have been confirmed in a phase 3 trial. Given the small number of patients (N = 29), and variations in patient characteristics, examining individual cases provides additional details regarding patient management with lomitapide. Here, we examine the details of the Italian patient cohort in the phase 3 trial.

METHODS AND RESULTS

The methodology of the multinational, single-arm, open-label, 78-week, dose-escalation, phase 3 trial has been previously reported. The current report details the Italian cohort of six patients (three males, three females) based on individual patient data, individual patient histories and narratives, and by mean data ± SD. Lomitapide was administered according to the dose-escalation protocol. At Week 78, concentrations of low-density lipoprotein-cholesterol were decreased by a mean of 42.6 ± 21.8% compared with baseline. Lomitapide was similarly well tolerated in the Italian cohort as in the entire study population. The most common adverse events were gastrointestinal symptoms. One patient showed an increase in liver transaminases >5× upper limit of normal that resolved after lomitapide treatment was reduced and maintained at a lower dose.

CONCLUSION

The efficacy, safety and tolerability of lomitapide demonstrated in the Italian subgroup of patients are consistent with findings in the entire study population, and illustrate the broad applicability of lomitapide therapy across genotypes and clinical phenotypes. These data also provide an insight into the management of lomitapide use in a cohort of patients within a clinical trial protocol. Clinicaltrials.gov Identifier: NCT00730236.

Liver as a target for oligonucleotide therapeutics

Oligonucleotide-based therapeutics are an emerging class of drugs that hold the promise for silencing "un-druggable" targets,thus creating unique opportunities for innovative medicines. As opposed to gene therapy, oligonucleotides are considered to be more akin to small molecule therapeutics because they are small,completely synthetic in origin, do not integrate into the host genome,and have a defined duration of therapeutic activity after which effects recover to baseline. They offer a high degree of specificity at the genetic level, thereby reducing off-target effects.At the same time, they provide a strategy for targeting any gene in the genome, including transcripts that produce mutated proteins.Oligonucleotide-based therapeutics include short interfering RNA (siRNA), that degrade target mRNA through RISC mediated RNAi; anti-miRs, that target miRNAs; miRNA mimics, that regulate target mRNA; antisense oligonucleotides, that may be working through RNAseH mediated mRNA decay; mRNA upregulation,by targeting long non-coding RNAs; and oligonucleotides induced alternative splicing [1]. All these approaches require some minimal degree of homology at the nucleic acid sequence level for them to be functional. The different mechanisms of action and their relevant activity are outlined in Fig. 1. Besides homology,RNA secondary structure has also been exploited in the case of ribozymes and aptamers, which act by binding to nucleic acids or proteins, respectively. While there have been many reports of gene knockdown and gene modulation in cell lines and mice with all these methods, very few have advanced to clinical stages.The main obstacle to date has been the safe and effective intracellular delivery of these compounds in higher species, including humans. Indeed, their action requires direct interaction with DNA/RNA within the target cell so even when one solves the issues of tissue and cellular access, intracellular/intranuclear location represents yet another barrier to overcome. To date,hepatic delivery of oligonucleotides has been the area with greatest progress, and thus we have focused on liver-targeted therapeutics that have shown promise at the preclinical and/or clinical level.The liver is the largest internal organ in the body, playing a central role in metabolism, detoxification, synthesis, and secretion of major plasma proteins (carrier proteins, coagulation factors,complement components, hormones, and apolipoproteins),and iron homeostasis. It is therefore not surprising that a large number of disease targets reside in the liver where they are susceptible to modulation by oligonucleotide therapies.