MTTP gene variants and lomitapide response in a cohort of patients with homozygous familial hypercholesterolemia

doi:10.21203/rs.3.rs-3230833/v1

Background: Homozygous familial hypercholesterolemia (HoFH) is a rare inherited disorder of lipoprotein metabolism caused by pathogenic variants in both alleles of key low-density lipoprotein receptor (LDLR)-mediated pathway genes, resulting in very high LDL cholesterol (LDL-C) levels from birth. The microsomal triglyceride transfer protein (MTTP) inhibitor, lomitapide, is an effective treatment for lowering LDL-C in HoFH that acts independently of LDLR. This study investigated the potential impact of MTTP gene variants on the response to lomitapide treatment in a cohort of patients with HoFH.

Methods: Data were extracted from medical records of patients diagnosed with HoFH and receiving treatment with lomitapide in addition to background statin + ezetimibe therapy. Data were collected from patient medical histories, and LDL-C levels before and after lomitapide treatment. Genetic sequencing of all exonic and intronic flanking regions of the MTTP gene was carried out for all patients with genomic DNA isolated whole blood.

Results: A total of 13 patients with a diagnosis of HoFH were identified (mean ± standard deviation age, 47.3 ± 17.3 years). In all patients, the median (range) dose of lomitapide was 20 mg/day (10 to 60 mg/day). Median (range) baseline LDL-C at initiation of lipid-lowering treatment (before lomitapide) was 240 mg/dL (162 to 478 mg/dL). Following lomitapide treatment the median (range) LDL-C level was 119 mg/dL (56 to 305 mg/dL), and all patients reported a reduction in LDL-C with lomitapide. A total of 151 MTTP gene variants were identified encompassing 50 distinct variants. There were significantly more variants per patient with LDL-C reduction >50% vs patients with LDL-C reduction ≤50% (P=0.08). Several MTTP gene variants (rs17533489, rs79194015, rs745075, rs41275715, rs1491246, and rs17533517) previously identified as potentially associated with a greater response to lomitapide treatment were significantly more common in patients with a reduction in LDL-C >50% than those with a reduction in LDL-C ≤50% (P<0.001).

Conclusions: This study builds upon previous findings by our group suggesting that variants in the MTTP gene may be predictors of response to lomitapide. Further research into the effect of MTTPvariants on response to lomitapide is warranted to aid treatment personalization in patients with HoFH.

Homozygous familial hypercholesterolemia

lomitapide

MTP

MTTP

LDLR

LDL-C

lipoprotein metabolism

genetic variants

Homozygous familial hypercholesterolemia (HoFH) is an ultra-rare inherited disorder of lipoprotein metabolism that is caused by pathogenic variants in both alleles of key low-density lipoprotein receptor (LDLR)-mediated pathway genes [1–3]. These variants result in very high LDL cholesterol (LDL-C) levels from birth; in some cases, these are up to ten times the level of those without familial hypercholesterolemia [1, 3]. Patients have an extremely high risk of cardiovascular disease (CVD) due to accelerated development of atherosclerosis [4, 5]. Interventions to reduce elevated levels of LDL-C must, therefore, be initiated as early as possible to manage CVD risk and prevent premature death [4, 5]. Nonpharmacological intervention, in the form of lifestyle modification (primarily institution of low-fat diet) has an important role in the treatment of HoFH; however, this alone is not sufficient to prevent the adverse and premature progression of CVD [4, 6]. Thus, pharmacological interventions are required to lower LDL-C [4]; high-intensity statins, such as rosuvastatin or atorvastatin, and ezetimibe are usually the first therapies that are introduced [7]. These treatments are rarely sufficient to lower LDL-C below targets levels, necessitating the introduction of further lipid-lowering interventions, such as lipoprotein apheresis and proprotein convertase subtilisin kexin type-9 (PSCK9) inhibitors [2, 8]. Additionally, there are treatments that work independently of LDLR, such as the microsomal triglyceride transfer protein (MTTP) inhibitor lomitapide and the recently approved angiopoetin-like 3 inhibitor, evinacumab [7–9]. If intensive lipid-lowering is not initiated in early childhood, there is a high risk of severe cardiovascular morbidity and mortality [10, 11].

Lomitapide is an effective treatment for lowering LDL-C in HoFH with the advantage of acting independently of LDLR [7], whereas the effect of most other pharmacological interventions is dependent on residual LDLR expression [2, 12]. Nevertheless, individual response to lomitapide can vary, with some patients requiring a higher lomitapide dose for equivalent LDL-C reduction than others [7]; a better understanding of factors that impact the effectiveness of lomitapide could assist in the personalized management of HoFH. The target of lomitapide, MTP, plays a crucial role in production and secretion of apolipoprotein B (apoB)-containing lipoproteins (very-low-density lipoproteins and chylomicrons) in the liver and intestines, respectively [13, 14]. Genetic variations in the MTTP gene caused by single nucleotide polymorphisms (SNPs) affect the lipid transfer activity of the MTP protein [15]. A previous case series hypothesized that genetic variants in the MTTP gene encoding MTP may influence HoFH patients’ response to MTTP inhibitors such as lomitapide [16]. This study further investigated the potential impact of MTTP gene variants on the response to lomitapide treatment in a cohort of 13 patients with HoFH.

Study subjects

Data were extracted from medical records of 13 patients diagnosed with HoFH and receiving treatment with lomitapide in addition to background statin + ezetimibe therapy. Data were collected from patient medical histories including CVD history, liver ultrasound results and HoFH pathogenic variants, and LDL-C levels before and after lomitapide treatment). Genetic sequencing of all exonic and intronic flanking regions of the MTTP gene was carried out for all patients with genomic DNA isolated whole blood as previously described [16].

Data analysis

The total number of different MTTP variants in the full cohort was calculated. The National Center for Biotechnology Information (NCBI) database of SNPs (dbSNP) and ClinVar databases were queried for individual variant information. Variants were merged where this had been applied on NCBI dbSNP. MTTP variants were stratified into different LDL-C reduction subgroups, using similar stratification methods to a previous study performed by our group [16]. Patients were stratified by whether lomitapide treatment induced a reduction in LDL-C of ≤ 50% or > 50%. As an additional exploratory analysis, patients were further stratified by whether lomitapide induced a reduction in LDL-C of ≤ 25%. As per our previous study [16], variants unique to the different subgroups were identified. Variants were then sorted into these subgroups to determine if any were uniquely associated with a high or lower response to lomitapide treatment.

All statistical analyses compared between the group with a ≤ 50% reduction in LDL-C and the group with a > 50% reduction in LDL-C. Individual variants were compared between groups using Fisher’s exact test. Continuous variables were compared between groups using the unpaired t-test if found to be normally distributed or the Mann-Whitney test if not found to be normally distributed.

Patient histories and LDL-C levels before and after lomitapide treatment are shown in Table 1. A total of 13 patients with a diagnosis of HoFH were identified, with a mean ± standard deviation age 47.3 ±17.3 years (median [range]: 46 [22 to 75] years). CVD history was available for 11/13 patients, which included myocardial infarction, coronary artery bypass graft, aortic valve replacement, percutaneous coronary intervention, carotid stenosis, and severe heart failure. The total number of CVD events before lomitapide initiation was 28 vs 3 events after lomitapide initiation in this patient cohort. Liver ultrasound results at baseline were available for 11/13 patients (84.6%); of these patients, 6 (54.5%) had a steatosis grading of 0 (steatosis absent) and 5 (45.5%) had a grading one 1 (mild). HoFH genetic data were available for 11/13 patients, with all but one showing bi-allelic mutations in the LDLR gene, with the remaining patient showing a bi-allelic mutation in the APOB gene. Median (range) baseline LDL-C level prior to lipid-lowering treatment was reported for 11/13 patients and was 780 mg/dL (240 to 1000 mg/dL). Median (range) baseline LDL-C following initiation of lipid-lowering treatment (before lomitapide) was 240 mg/dL (162 to 478 mg/dL), with data available for all patients. Concomitant medications that were not lipid-lowering treatments prescribed to patients during the period of lomitapide treatment are shown in Supplementary Table 1, Additional File 1. Following lomitapide treatment, the median (range) LDL-C level was 119 mg/dL (56 to 305 mg/dL). All patients reported a reduction in LDL-C with lomitapide. The median (range) percentage change in LDL-C levels after lomitapide treatment was –43.8% (–71.6 to –10.9%) and did not appear to be related to the duration of lomitapide treatment as this was 2–9 years (R²=0.05) with a median (range) dose of lomitapide 20 mg/day (10 to 60 mg/day) in the full patient cohort (R²=0.05). In total, three patients achieved an LDL-C level of <100 mg/dL after lomitapide treatment (Table 1). Further to this LDL-C goal, a single patient achieved an LDL-C level <70 mg/dL after lomitapide treatment (patient 9, 56 mg/dL; LDL-C change, –71.6%), with a second patient approaching this level (patient 7, 74 mg/dL; LDL-C change, –54.3%).

Patients were stratified according to change in LDL-C reduction after lomitapide (Table 2). In response to lomitapide treatment, 6/13 patients (46.2%) showed a reduction in LDL-C >50%, with 7/13 (53.8%) showing reductions in LDL-C ≤50%. Median dose of lomitapide was the same for both the LDL-C >50% and ≤50% groups (20 mg/day); however, the maximum dose was higher in the LDL-C ≤50% reduction group (60 mg/day) compared with the LDL-C >50% reduction group (40 mg/day).

A total of 151 MTTP variants were identified encompassing 50 distinct variants. Querying of dbSNP revealed four variants associated with insertion/deletion of nucleotide sequences or nucleotide substitution leading to a synonymous variant (rs545365701/rs756785244/rs757684569, rs375598284, rs397878861/rs5860586 and rs982424). These variants appeared in 4/6 patients with reduction in LDL-C >50% and 6/7 patients with reduction in LDL-C ≤50% and did not appear to have an overall influence on LDL-C reduction with lomitapide. Variants unique to either LDL-C >50% or ≤50% reduction groups – and therefore potentially associated with lomitapide response – are listed in Table 3. Two variants associated with insertion/deletions (rs375598284 and rs397878861/rs5860586) were unique to patients in the LDL-C >50% reduction group, suggesting that these variants did not impair the lipid-lowering effect of lomitapide in these patients, or alternatively may be advantageous. A single variant, rs982424, was identified to lead to a synonymous variant and was only present in two patients with a reduction in LDL-C ≤50%: patient 1 (37.1% reduction) and patient 12 (10.9% reduction; lowest responder in the cohort).

In a previous study performed by our group [16], results suggested that six identified variants (rs17533489, rs79194015, rs745075, rs41275715, rs1491246, rs17533517) were associated with an enhanced effect of lomitapide (reduction in LDL-C >50%). All of these variants were observed in the present study cohort and generally only occurred in patients with reduction in LDL-C >50%. The only occurrence of these variants in patients with reduction in LDL-C ≤50% was in patient 3 who was receiving treatment with 10 mg lomitapide. This patient had 5/6 of the variants and the greatest reduction in LDL-C in the ≤50% group (43.8%). A comparison of these variants between LDL-C >50% and ≤50% reduction groups is shown in Table 4. The variant rs17533489 was significantly more common in the LDL-C >50% reduction group (p=0.02) and there was also weak evidence that rs79194015, rs745075 and rs41275715 were more common in the LDL-C >50% reduction group, although these results were not statistically significant; however, the overall occurrence of the six variants was found to be significantly greater in patients with reduction in LDL-C >50% vs. the ≤50% reduction group (mean: 4.6 versus 0.7, respectively; p<0.001). A further variant of interest previously identified by our group, rs3816873, did not significantly vary between the two groups (p=0.46).

Although there was a similar number of patients in both LDL-C >50% and ≤50% reduction groups in the present analysis (6/13 and 7/13 patients, respectively), there was approximately double the total number of variants in the former group than the latter group (Table 2). There was a mean of 16 variants per patient with LDL-C reduction >50%, compared with a mean of 8 variants per patient with LDL-C reduction ≤50%, and this difference approached statistical significance (p=0.08; Table 4). There was a weak/moderate positive correlation between the number of MTTP variants observed in each patient and individual response to lomitapide (R²=0.3186; Figure 1).

In this study, response to lomitapide treatment was assessed via the change in LDL-C levels in patients with HoFH. Patients possessed different SNPs in the MTTP gene, which our previous small study (n = 4) hypothesized would affect LDL-C reduction after lomitapide treatment [16].

According to previous methodology [16], it could be argued that the unique variants identified in this patient cohort may be associated with the degree of response to lomitapide treatment. Of note in the present study is the rs982424 variant, which was only seen in patients with lower response (LDL-C reduction ≤ 50%) as expected since it does not alter amino acid sequence of the protein while other identified variants which affect non-coding regions of the gene which may regulate gene expression.

Interestingly, all the variants identified as potentially associated with reduction in LDL-C > 50% in our previous study were found in the present cohort and were determined to be significantly more common in the higher response group reported here. This supports the hypothesis that these variants are associated with greater response to lomitapide treatment; rs17533489 is associated with the strongest evidence for this as it is present in patients with the greatest reduction in LDL-C following lomitapide treatment. Another of the six previously highlighted variants, rs745075, was found in a study of 202 statin-treated patients to be significantly associated with lipid-lowering compared with patients without the variant (p = 0.035) [17]. Although low patient numbers in the present study potentially prevented a significant association between this variant and a high response, the findings presented here suggest that the variant may also be associated with lipid-lowering response to lomitapide.

In addition to some individual variants potentially being associated with reduction in LDL-C > 50%, there was evidence that the cumulative effect of multiple minor variants could also be associated with this, as a greater number of variants were observed in the LDL-C > 50% reduction group versus the LDL-C ≤ 50% reduction group. This is further supported by the weak/moderate positive correlation between LDL-C reduction following lomitapide treatment and the number of MTTP variants found in each patient. A possible explanation for this may be that the cumulative effect of multiple minor genetic variants within the MTTP protein causes aberrant function/secretion to an extent that lomitapide binds a higher proportion of MTTP protein, thereby increasing the treatment effect.

We previously highlighted rs3816873 as a variant of interest [16], suggesting that this is a variant that confers reduced structural stability of MTTP and decreased binding to apoB, and possibly associated with a higher risk of CVD through the overloading of triglycerides in the myocardium [18]. In this patient cohort there was no significant difference in this variant between the LDL-C > 50% and LDL-C ≤ 50% reduction groups; rs3816873 occurred in both patient groups suggesting this variant does not affect response to lomitapide.

Several other variants identified in this study have been reported as being associated with lipid dysfunction. Dai et al. [19] reported that rs2306986 was associated with non-alcoholic fatty liver disease (NAFLD) in obese children. It was concluded that this MTTP variant may alter lipid metabolism by disrupting the MTTP protein function, leading to aberrant triglyceride storage in the liver. In the present study, rs2306986 was unique to the patient in LDL-C ≤ 50% reduction group with the smallest change in LDL-C levels, and this could be related to the above previously identified change in function. Furthermore, a cross-sectional study reported that rs2306986, along with rs3792683 and rs2306985, were associated with significantly lower serum triglycerides [20], with rs2306985 also associated with increased risk of NAFLD. Similar to rs2306986, rs3792683 was uniquely identified in the LDL-C ≤ 50% reduction group in the present study.

The MTTP variants rs1800804 and rs1057613 have also been shown to be associated with NAFLD risk (increased and decreased risk, respectively) [13]; however, the current study identified these variants in both patient groups, suggesting they do not influence response to lomitapide treatment. While these variants may not directly affect response to lomitapide treatment, their presence may influence subsequent hepatic steatosis status. The liver ultrasound data available for this cohort of patients with HoFH indicated that the highest liver steatosis grading was 1 (mild), and there was, therefore, little evidence that particular MTTP variants are contributing to steatosis in these patients. Nevertheless, since it is known that lomitapide can increase liver enzymes and hepatic fat [21], knowledge of increased risk due to background genetic variation in patients may allow clinicians to provide patients with an appropriate dosage and manage any adverse events which may arise in a timely manner, if an association is confirmed.

Lomitapide is a small-molecule that is metabolized by CYP3A4 in the liver [22]. As such, lomitapide response is likely influenced by CYP3A4 enzyme activity, which can show significant inter-patient variability and can be impacted by commonly prescribed drugs in cardiovascular disease such as diltiazem or verapamil [23, 24]. While CYP3A4 activity with concomitant medication was not accounted for in this study, the patient with the highest response to lomitapide was also receiving a low dose of amiodarone, a weak inhibitor of CYP3A4 [25, 26]. This may suggest that the higher response to lomitapide was partially aided by the inhibition of CYP3A4 and a reduction in metabolism of the small molecule; however, no other patients were receiving any concomitant medications that may have affected the activity of CYP3A4 (Supplementary Table 1, Additional File 1) and several were able to maintain high levels of LDL-C reduction.

Despite the variability in lomitapide response seen in the present cohort, it is encouraging that the majority of patients (8/13) showed at least a 40% reduction in LDL-C subsequent to the introduction of lomitapide. It is also encouraging that the great majority of cardiovascular events were reported prior to lomitapide initiation; however, as only two patients fell under or approached the target LDL-C level of 70 mg/dL, this highlights the challenge of achieving these levels in patients with HoFH, and the need for dosage up-titration where needed.

There were several limitations to the present study. The dosage of lomitapide (although on average similar between LDL-C > 50% and LDL-C ≤ 50% reduction groups) was not standardized owing to this being a retrospective analysis in a rare disease with few patients to choose from. Although the cohort was larger than in our previous study [16], the small number of patients (which again reflects the status of HoFH as an ultra-rare and underdiagnosed condition) means that only tentative conclusions can be drawn regarding the impact of specific MTTP variants on lomitapide response. Overall, further research, such as in vitro binding studies or computational modeling, is required to confirm whether particular variants indeed abrogate or enhance the effectiveness of lomitapide.

The present analysis lends support to previous findings by our group [16], suggesting that variants in the MTTP gene may be predictors of response to lomitapide. This study further presented a number of variants that may be uniquely associated with higher or lower response to lomitapide treatment. Further research into the effect of MTTP variants on response to lomitapide is warranted to aid treatment personalization in patients with HoFH.

Ethics approval

The study protocol was approved by the Ethics Committee of Metropolitan and Ioannina Hospitals.

Consent for publication

Written informed consent was obtained from all study subjects.

Availability of data and materials

The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.

Competing interests

GK has given talks and participated in trials sponsored by Amgen, Lilly, MSD, Novartis, Sanofi, Vianex and nonfinancial support from Amryt; EL reports personal fees from Boehringer-Ingelheim, Chiesi, Lilly, MSD, Novartis, Sanofi and Servier, and personal fees and nonfinancial support from Amgen, AstraZeneca and Bayer; VK, KA, GA and PK report no conflicts of interest.

Funding

This research was an investigator-initiated study and funded through a grant from Amryt Pharmaceuticals DAC. Statistical/data analysis and medical writing support was funded by Amryt Pharmaceuticals DAC, Dublin, Ireland.

Authors' contributions

All authors contributed to analyzing and interpreting the data, drafting the manuscript and approved the final manuscript. The authors were in full control of this research. Amryt Pharmaceuticals DAC was not involved in data analysis, in the preparation of the manuscript nor in the decision to submit it for publication.

Acknowledgements

Statistical/data analysis and medical writing support was provided by Meridian HealthComms Ltd, Manchester, UK, and funded by Amryt Pharma DAC, Dublin, Ireland.

Availability of data

The de-identified patient data may be available from the corresponding author (GK) upon reasonable request.

Cuchel M, Bruckert E, Ginsberg HN, et al. Homozygous familial hypercholesterolaemia: new insights and guidance for clinicians to improve detection and clinical management. A position paper from the Consensus Panel on Familial Hypercholesterolaemia of the European Atherosclerosis Society. Eur Heart J. 2014;35(32):2146-57.
Cuchel M, Raal FJ, Hegele RA, et al. 2023 Update on European Atherosclerosis Society Consensus Statement on Homozygous Familial Hypercholesterolaemia: new treatments and clinical guidance. Eur Heart J. 2023.
Nordestgaard BG, Chapman MJ, Humphries SE, et al. Familial hypercholesterolaemia is underdiagnosed and undertreated in the general population: guidance for clinicians to prevent coronary heart disease: consensus statement of the European Atherosclerosis Society. Eur Heart J. 2013;34(45):3478-90a.
Harada-Shiba M, Arai H, Ishigaki Y, et al. Guidelines for Diagnosis and Treatment of Familial Hypercholesterolemia 2017. J Atheroscler Thromb. 2018;25(8):751-70.
Nohara A, Tada H, Ogura M, et al. Homozygous Familial Hypercholesterolemia. J Atheroscler Thromb. 2021;28(7):665-78.
Juliani FC, Chacra APM, Miname MH, et al. Abstract 12279: Cardiovascular Disease Progression in Children With Homozygous Familial Hypercholesterolemia Despite Early Diagnosis on a Genetic Cascade Screening Program. Circulation. 2022;146(Suppl_1):A12279-A.
Cuchel M, Meagher EA, du Toit Theron H, et al. Efficacy and safety of a microsomal triglyceride transfer protein inhibitor in patients with homozygous familial hypercholesterolaemia: a single-arm, open-label, phase 3 study. Lancet. 2013;381(9860):40-6.
Kolovou G, Vasiliadis I, Gontoras N, Kolovou V, Hatzigeorgiou G. Microsomal transfer protein inhibitors, new approach for treatment of familial hypercholesterolemia, review of the literature, original findings, and clinical significance. Cardiovasc Ther. 2015;33(2):71-8.
Food and Drug Administration. FDA approves add-on therapy for patients with genetic form of severely high cholesterol 2021 [Available from: https://www.fda.gov/drugs/news-events-human-drugs/fda-approves-add-therapy-patients-genetic-form-severely-high-cholesterol-0.
Thompson GR, Group H-ULAW. Recommendations for the use of LDL apheresis. Atherosclerosis. 2008;198(2):247-55.
Mainieri F, Tagi VM, Chiarelli F. Recent Advances on Familial Hypercholesterolemia in Children and Adolescents. Biomedicines. 2022;10(5).
Taechalertpaisarn J, Zhao B, Liang X, Burgess K. Small Molecule Inhibitors of the PCSK9.LDLR Interaction. J Am Chem Soc. 2018;140(9):3242-9.
Peng XE, Wu YL, Lu QQ, Hu ZJ, Lin X. MTTP polymorphisms and susceptibility to non-alcoholic fatty liver disease in a Han Chinese population. Liver Int. 2014;34(1):118-28.
Gordon DA, Jamil H. Progress towards understanding the role of microsomal triglyceride transfer protein in apolipoprotein-B lipoprotein assembly. Biochim Biophys Acta. 2000;1486(1):72-83.
Hussain MM, Rava P, Walsh M, Rana M, Iqbal J. Multiple functions of microsomal triglyceride transfer protein. Nutr Metab (Lond). 2012;9:14.
Kolovou GD, Kolovou V, Papadopoulou A, Watts GF. MTP Gene Variants and Response to Lomitapide in Patients with Homozygous Familial Hypercholesterolemia. J Atheroscler Thromb. 2016;23(7):878-83.
Ruaño G, Thompson PD, Kane JP, et al. Physiogenomic analysis of statin-treated patients: domain-specific counter effects within the ACACB gene on low-density lipoprotein cholesterol? Pharmacogenomics. 2010;11(7):959-71.
Ledmyr H, Ottosson L, Sunnerhagen M, Ehrenborg E. The Ile128Thr polymorphism influences stability and ligand binding properties of the microsomal triglyceride transfer protein. J Lipid Res. 2006;47(7):1378-85.
Dai D, Wen F, Zhou S, et al. Association of MTTP gene variants with pediatric NAFLD: A candidate-gene-based analysis of single nucleotide variations in obese children. PLoS One. 2017;12(9):e0185396.
Hsiao PJ, Lee MY, Wang YT, et al. MTTP-297H polymorphism reduced serum cholesterol but increased risk of non-alcoholic fatty liver disease-a cross-sectional study. BMC Med Genet. 2015;16:93.
deGoma EM. Lomitapide for the management of homozygous familial hypercholesterolemia. Rev Cardiovasc Med. 2014;15(2):109-18.
National Center for Biotechnology Information. Lomitapide. LiverTox: Clinical and Research Information on Drug-Induced Liver Injury. Bethesda (MD)2012.
National Health Service. Diltiazem. 2020. Available at: https://www.nhs.uk/medicines/diltiazem/ (date accessed December 15 2022).
National Health Service. Verapamil. 2021. Available at: https://www.nhs.uk/medicines/verapamil/ (date accessed December 15 2022).
Ohyama K, Nakajima M, Suzuki M, Shimada N, Yamazaki H, Yokoi T. Inhibitory effects of amiodarone and its N-deethylated metabolite on human cytochrome P450 activities: prediction of in vivo drug interactions. Br J Clin Pharmacol. 2000;49(3):244-53.
McDonald MG, Au NT, Rettie AE. P450-Based Drug-Drug Interactions of Amiodarone and its Metabolites: Diversity of Inhibitory Mechanisms. Drug Metab Dispos. 2015;43(11):1661-9.

Table 1. Patient histories and LDL-C levels before and after lomitapide treatment

Patient ID	Age (years)	CVD history		Steatosis grading (liver ultrasound)	HoFH genetics^a	Lomitapide dose (mg/day)	Lomitapide duration (years)	LDL-C (mg/dL)
		CVD history						At diagnosis	Baseline on LLT	After lomitapide	% change from baseline LLT to after lomitapide
		Before lomitapide	After lomitapide					At diagnosis	Baseline on LLT	After lomitapide	% change from baseline LLT to after lomitapide
>50% LDL-C reduction from baseline LLT to after lomitapide
9	75	Non-fatal MI (NSTEMI RCA), non-fatal MI (strain)	Non-fatal MI (NSTEMI RCA-PCI)	N/A	LDLR: 1775G>A	10	5	N/A	197	56	–71.6
11	29	CABG, AVR, carotid stenosis	–	0	LDLR: c.1285G>A (p.Val429Met)	20	9	950	330	114	–65.5
6	46	–	–	1	LDLR: c.166T>C; p.Ser56Pro and c.1285G>A; p.Val429Met	30	7	511	478	185	–61.3
5	42	Non-fatal MI, PCI	–	1	LDLR: c.81C>G; p.Cys27Trp and c.1646G>A; p.Gly549Asp	40	4	371	235	106	–54.8
13	61	CABG x2, PCI x2, AVR, carotid endarterectomy, severe heart failure	PCI, death	1	N/A	20	6	780	259	118	–54.4
7	42	CABG	angina	N/A	LDLR: p.Gly1775Ala	10	4.5	N/A	162	74	–54.3
≤50% LDL-C reduction from baseline LLT to after lomitapide
3	62	Non-fatal MI, CABG, carotid stenosis	–	1	LDLR: c.858C>A; p.Ser286Arg and c.1291G>A; p.Ala431Thr	10	2	240	176	99	–43.8
4	53	Non-fatal MI, PCI, carotid endarterectomy, severe heart failure	–	0	LDLR: c.858C>A; p.Ser286Arg and c.1291G>A; p.Ala431Thr	10	2	500	204	119	–41.7
1	22	Mild aortic valve stenosis	–	0	LDLR: c.666C>A; p.Cys222* and c.1646G>A; p.Gly549Asp	60	4	1000	350	220	–37.1
10	32	Mild carotid stenosis	–	0	LDLR: c.1448G>A, (p.Trp483X) and c.1646G>A	20	9	900	472	305	–35.4
≤25% LDL-C reduction from baseline LLT to after lomitapide
2	69	Mild carotid stenosis	–	0	APOB: c.10580G>A; p.Arg3527Gln (rs5742904) Het	40	2	600	240	180	–25.0
8	24	–	–	0	LDLR: G1646A	20	5	987	243	188	–22.6
12	58	CABG + AVR, carotid endarterectomy, severe heart failure	–	1	N/A	20	6	900	220	196	–10.9

^aAll patients had two copies of each mutation listed.

APOB, apolipoprotein B-100; AVR, aortic valve replacement; CABG, coronary artery bypass graft; CVD, cardiovascular disease; ID, identification; LDL-C, low-density lipoprotein cholesterol; LDLR, low-density lipoprotein receptor; LLT, lipid-lowering treatment; MI, myocardial infarction; N/A, not available; NSTEMI, non-ST segment elevation myocardial infarction; PCI, percutaneous coronary intervention; RCA, right coronary artery.

Table 2. Stratification according to LDL-C reduction after lomitapide

Category	Number
Total patients	13
Number of patients with change in LDL-C >50%	6
Number of patients with change in LDL-C ≤50%^a	7
Number of patients with change in LDL-C ≤25%	3
Total number of MTTP variants in full cohort	151
Number of variants in LDL-C >50% reduction subgroup	97
Number of variants LDL-C ≤50% reduction subgroup^a	54
Number of variants LDL-C ≤25% reduction subgroup	16
Total number of distinct MTTP variants in full cohort	50
Number of variants unique to LDL-C >50% reduction subgroup	15
Number of variants in LDL-C ≤50% reduction subgroup but not in LDL-C >50% reduction subgroup^a	8
Number of variants in LDL ≤25% reduction subgroup not observed in patients with >25% LDL-C reduction	2

^aIncludes variants in LDL-C ≤25% reduction subgroup, low-density lipoprotein cholesterol.

LDL-C, low-density lipoprotein cholesterol.

Table 3. Variants unique to the LDL-C >50% and ≤50% reduction groups

LDL-C >50% reduction	LDL-C ≤50% reduction
rs112407688, rs112568939, rs113337987, rs113557405, rs113653192, rs114681504, rs141186441, rs1491244, rs17533489, rs375598284^a, rs397878861/rs5860586^a, rs61733139, rs6832119, rs6832927 and rs74542928	rs11944749, rs17532601, rs2255119, rs2306984, rs2306986^b, rs3792683^b, rs7533489, rs982424^c, rs114681504 and rs17533489

^aAssociated with insertion/deletion; ^bassociated with patients who experienced a very low response (≤25%); ^cassociated with stop codon insertion.

Table 4. Variant association with LDL-C >50% and ≤50% reduction groups – statistical comparisons

Variable	Reduction in LDL-C >50% (n=6)	Reduction in LDL-C ≤50% (n=7)	P-value
Number of variants per patient	16.2 ± 10.4	7.7 ± 4.8	0.08
rs982424	0 (0%)	2 (29%)	0.46
Variants previously identified in patients with reduction in LDL-C >50% [16]	4.6 ± 1.7	0.7 ± 1.8	<0.001
rs17533489	4 (67%)	0 (0%)	0.02
rs79194015	4 (67%)	1 (14%)	0.10
rs745075	4 (67%)	1 (14%)	0.10
rs41275715	4 (67%)	1 (14%)	0.10
rs1491246	2 (33%)	1 (14%)	0.56
rs17533517	3 (50%)	1 (14%)	0.27
Previously identified variant of interest[16]
rs3816873	4 (67%)	3 (43%)	0.59

Summary statistics are mean ± standard deviation or mean (percentage). Significance was determined by p<0.05.

LDL-C, low-density lipoprotein cholesterol.

KolovouMTTPvariantsAdditionalFile1.docx

MTTP gene variants and lomitapide response in a cohort of patients with homozygous familial hypercholesterolemia

Status:

Version 1

Abstract

Figures

Background

Methods

Data analysis

Results

Discussion

Conclusions

Declarations