Clinical Trial Details
— Status: Withdrawn
Administrative data
| NCT number |
NCT03198897 |
| Other study ID # |
BHFH 06-2018 |
| Secondary ID |
|
| Status |
Withdrawn |
| Phase |
|
| First received |
|
| Last updated |
|
| Start date |
August 20, 2018 |
| Est. completion date |
February 28, 2021 |
Study information
| Verified date |
February 2023 |
| Source |
CENTOGENE GmbH Rostock |
| Contact |
n/a |
| Is FDA regulated |
No |
| Health authority |
|
| Study type |
Observational
|
Clinical Trial Summary
Development of a new MS-based biomarker for the early and sensitive diagnosis of Homozygous
familial Hypercholesterolemia from blood
Description:
Homozygous familial hypercholesterolemia (HoFH) is a rare hereditary disorder of lipoprotein
metabolism characterized by exceptionally high levels of low-density lipoprotein cholesterol
(LDL-C). Clinical manifestations may vary but often include markedly premature coronary
artery disease, supravalvular aortic stenosis due to aortic root atheroma, and cutaneous
manifestations such as tendon xanthomata. Although there are no universally ac-cepted
clinical diagnostic criteria for HoFH, an untreated serum LDL-C of >13 mmol/L (500 mg/dL), or
an on-treatment LDL-C of more 8 mmol/L (300 mg/dL) together with the appearance of cutaneous
xanthomata before the age of 10 years, have often been used to diagnose HoFH clinically. As
molecular diagnostic techniques have advanced, genotyping of patients with severe
hypercholesterolemia has become an integral part of clinical practice in many settings. This
has led to the realization that the spectrum of clinical severity in HoFH is much wider than
initially thought and that the clinical criteria often fail to identify patients with milder
phenotypes.
Although the HoFH phenotype may result from mutations in multiple genes, low-density
lipoprotein receptor (LDL-R) dysfunction is the final common pathophysiological pathway
leading to LDL-C elevation in patients with HoFH and LDL-R mutations are by far the most
common genetic causes of HoFH. Patients with HoFH secondary to LDL-R mutations inherit a
mutated allele from each parent, resulting in severe functional impairment of the LDL-R
pathway. Residual LDL-R activity may vary considerably between mutations. Patients with HoFH
can be classified as receptor negative or receptor defective (<2% or 2%-25% of residual
activity, respectively) based on LDL uptake studies in cultured fibroblasts, although
receptor function is nowadays often inferred after the identification of specific mutations.
Historically, the prevalence of HoFH has been reported as 1 case per million. However,
emerging studies suggest that the prevalence of HeFH, and consequently HoFH, may be higher
than previously thought. Recent literature suggests an estimated prevalence of HeFH of ∼1
case in 2002 and of deleterious LDLR mutations in 0.45% of a control population and 1.9% of
individuals with early-onset myocardial infarction or coronary artery dis-ease.Extrapolating
from these data, the prevalence of HoFH is estimated to be ∼6 cases per million. Analysis of
a Dutch database of molecularly defined HoFH suggested a prevalence of ∼1 case per
160,000-300,000. Prevalence data are, however, continuing to evolve, and these calculations
could be underestimates or overestimates of the prevalence in the general patient population.
Information on the prevalence of FH in non-European populations is generally limited, and
conclusions about the possible worldwide prevalence remain speculative. However, as a result
of founder effects, the prevalence of HeFH and HoFH is higher in certain populations such as
the Afrikaners in South Africa, Christian Lebanese, and French Canadians.
The range of untreated and treated LDL-C levels in HoFH is wide. In two recent clinical
tri-als of novel therapies for HoFH, the LDL-C levels at study entry in conventionally
treated patients ranged from a mean of 8.7 ± 2.9 mmol/L (336 ± 112 mg/dL) to 11.4 ± 3.6
mmol/L (441 ± 139 mg/dL). Not all patients with HoFH have extreme LDL-C elevations. In a
study from the Netherlands, only 50% of patients with molecularly defined HoFH met the
clinical criterion of untreated LDL-C >13 mmol/L (500 mg/dL), with some patients presenting
with untreated LDL-C levels as low as 4.4 mmol/L (170 mg/dL).
Reported LDL-C levels for clinical and genetic diagnoses of FH. Improved molecular diagnosis
has led to the understanding that a conventional diagnosis of HoFH encompasses a wide range
of underlying mutations with different effects on LDL-C levels, and highlights the need for
caution in interpreting historical LDL-C values. Furthermore, some patients with clinical FH
(10%-40%) lack an identified disease-causing mutation.
A genetic diagnosis is highly desirable since the phenotype of severe hypercholesterolemia is
highly overlapping.
Actually 4 genes have been described being involved in the disease. The most common genetic
defects in FH are LDLR mutations (prevalence 1 in 500, depending on the population), ApoB
mutations (prevalence 1 in 1000), PCSK9 mutations (less than 1 in 2500) and LDLRAP1. The
related disease sitosterolemia, which has many similarities with FH and also features
cholesterol accumulation in tissues, is due to ABCG5 and ABCG8 mutations.
LDL receptor The LDL receptor gene is located on the short arm of chromosome 19
(19p13.1-13.3). It comprises 18 exons and spans 45 kb, and the protein gene product contains
839 amino acids in mature form. A single abnormal copy (heterozygote) of FH causes
cardiovascular disease by the age of 50 in about 40% of cases. Having two abnormal copies
(homozygote) causes accelerated atherosclerosis in childhood, including its complications.
The plasma LDL levels are inversely related to the activity of LDL receptor (LDLR).
Homozygotes have LDLR activity of less than 2%, while heterozygotes have defective LDL
pro-cessing with receptor activity being 2-25%, depending on the nature of the mutation. Over
1000 different mutations are known.
Apolipoprotein B Apolipoprotein B, in its ApoB100 form, is the main apolipoprotein, or
protein part of the lipoprotein particle. Its gene is located on the second chromosome
(2p24-p23) and is be-tween 21.08 and 21.12 Mb long. FH is often associated with the mutation
of R3500Q, which causes replacement of arginine by glutamine at position 3500. The mutation
is located on a part of the protein that normally binds with the LDL receptor, and binding is
reduced as a result of the mutation. Like LDLR, the number of abnormal copies determines the
severity of the hypercholesterolemia.
PCSK9 Mutations in the proprotein convertase subtilisin/kexin type 9 (PCSK9) gene were linked
to autosomal dominant (i.e. requiring only one abnormal copy) FH in a 2003 report. The gene
is located on the first chromosome (1p34.1-p32) and encodes a 666 amino acid protein that is
expressed in the liver. It has been suggested that PCSK9 causes FH mainly by reducing the
number of LDL receptors on liver cells.
LDLRAP1 Abnormalities in the ARH gene, also known as LDLRAP1, were first reported in a family
in 1973. In contrast to the other causes, two abnormal copies of the gene are required for FH
to develop (autosomal recessive). The mutations in the protein tend to cause the production
of a shortened protein. Its real function is unclear, but it seems to play a role in the
relation between the LDL receptor and clathrin-coated pits. People with autosomal recessive
hypercholesterolemia tend to have more severe disease than LDLR-heterozygotes but less severe
than LDLR-homozygotes.
New methods, like mass-spectrometry give a good chance to characterize specific metabolic
alterations in the blood (plasma) of affected patients that allow diagnosing in the future
the disease earlier, with a higher sensitivity and specificity.
Therefore it is the goal of the study to identify and validate a new biochemical marker from
the blood of the affected patients helping to benefit other patients by an early diagnose and
thereby with an earlier treatment.
