P5328Clinical and demographic predictors of attenuated LDL-C response to PCSK9 inhibition with bococizumab: Insights from the SPIRE trials

Background

While there exists significant inter-individual variability in low density lipoprotein cholesterol (LDL-C) response to proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibition, predictors of this response remain uncertain. The Studies of PCSK9 Inhibition and the Reduction of Vascular Events (SPIRE) randomized control trials evaluated the efficacy of bococizumab, a humanized murine PCSK9 antibody, in patients at high cardiovascular risk.

Purpose

This study's purpose is to determine predictors of attenuated LDL-C response to bococizumab.

Methods

SPIRE 1 and 2 trial subjects allocated to bococizumab (n=13,675) were included. Subjects with an increase in LDL-C or non-compliance to bococizumab, or development of anti-drug or neutralizing antibodies were excluded. The remaining 8281 subjects were divided into quintiles of percent LDL-C reduction from baseline to 14 weeks. The first quintile (Q1) was considered an attenuated response. Multivariate logistic regression was used to discern significant predictors of attenuated response (Q1) compared to robust response (Q5).

Results

Q1 included 1657 subjects with median 35% LDL-C reduction (range 0.4% - 48%), whereas Q5 included 1658 subjects with median 83% LDL-C reduction (range 78% - 99%). Female sex, diabetes, white race, younger age, higher baseline non-high-density lipoprotein cholesterol (non-HDL-C), lipoprotein (a) [Lp(a)] and high-sensitivity C-reactive protein (hsCRP) were significantly associated with an attenuated response compared to a robust response (each p<0.05, Table).

Multivariate logistic regression for attenuated percent LDL-C response to bococizumab from baseline to 14 week Baseline characteristic Adjusted odds ratio (95% confidence interval) P-value Female 3.30 (2.72, 4.00) <0.0001 Diabetes 1.57 (1.32, 1.86) <0.0001 White race 1.44 (1.07, 1.93) 0.016 BMI (per 1kg/m2) 1.09 (1.07, 1.11) <0.0001 Age (per year) 0.98 (0.98, 0.99) 0.0005 Ln hs-CRP (per 1mg/L) 1.19 (1.11, 1.29) <0.0001 Lp (a) (per 10mg/dL) 1.11 (1.09, 1.14) <0.0001 Non-HDL-C (per 10mg/dL) 1.05 (1.02, 1.07) <0.0001 Odds ratios mutually adjusted for the listed variables.

Conclusions

In the SPIRE 1 and 2 trials, excluding subjects with anti-drug and neutralizing antibodies, significant predictors of an attenuated LDL-C response to PCSK9 inhibition with bococizumab included female sex, diabetes, younger age and white race.

Acknowledgement/Funding

Pfizer

p.(Asp47Asn) and p.(Thr62Met): non deleterious LDL receptor missense variants functionally characterized in vitro

Familial Hypercholesterolemia (FH) is a common genetic disorder caused most often by mutations in the Low Density Lipoprotein Receptor gene (LDLr) leading to high blood cholesterol levels, and ultimately to development of premature coronary heart disease. Genetic analysis and subsequent cascade screening in relatives allow diagnosis of FH at early stage, especially relevant to diagnose children. So far, more than 2300 LDLr variants have been described but only a minority of them have been functionally analysed to evaluate their pathogenicity in FH. Thus, identifying pathogenic mutations in LDLr is a long-standing challenge in the field. In this study, we investigated in vitro the activity p.(Asp47Asn) and p.(Thr62Met) LDLr variants, both in the LR1 region. We used CHO-ldlA7 transfected cells with plasmids carrying p.(Asp47Asn) or p.(Thr62Met) LDLr variants to analyse LDLr expression by FACS and immunoblotting, LDL binding and uptake was determined by FACS and analysis of mutation effects was assessed in silico. The in vitro activity assessment of p.(Asp47Asn) and p.(Thr62Met) LDLr variants shows a fully functional LDL binding and uptake activities. Therefore indicating that the three of them are non-pathogenic LDLr variants. These findings also emphasize the importance of in vitro functional LDLr activity studies to optimize the genetic diagnosis of FH avoiding the report of non-pathogenic variants and possible misdiagnose in relatives if cascade screening is carried out.

Replacement of cysteine at position 46 in the first cysteine-rich repeat of the LDL receptor impairs apolipoprotein recognition

Background and aims

Pathogenic mutations in the Low Density Lipoprotein Receptor gene (LDLR) cause Familial Hypercholesterolemia (FH), one of the most common genetic disorders with a prevalence as high as 1 in 200 in some populations. FH is an autosomal dominant disorder of lipoprotein metabolism characterized by high blood cholesterol levels, deposits of cholesterol in peripheral tissues such as tendon xanthomas and accelerated atherosclerosis. To date, 2500 LDLR variants have been identified in the LDLR gene; however, only a minority of them have been experimentally characterized and proven to be pathogenic. Here we investigated the role of Cys46 located in the first repeat of the LDL receptor binding domain in recognition of apolipoproteins.

Methods

Activity of the p.(Cys46Gly) LDLR variant was assessed by immunoblotting and flow cytometry in CHO-ldlA7 expressing the receptor variant. Affinity of p.(Cys46Gly) for LDL and VLDL was determined by solid-phase immunoassays and in silico analysis was used to predict mutation effects.

Results and conclusion

Functional characterization of p.(Cys46Gly) LDLR variant showed impaired LDL and VLDL binding and uptake activity. Consistent with this, solid-phase immunoassays showed the p.(Cys46Gly) LDLR variant has decreased binding affinity for apolipoproteins. These results indicate the important role of Cys46 in LDL receptor activity and highlight the role of LR1 in LDLr activity modulation. This study reinforces the significance of in vitro functional characterization of LDL receptor activity in developing an accurate approach to FH genetic diagnosis. This is of particular importance because it enables clinicians to tailor personalized treatments for patients’ mutation profile.

Isolation of nematicidal compounds from Tagetes patula L. yellow flowers: structure-activity relationship studies against cyst nematode Heterodera zeae infective stage larvae

Bioassay-guided isolation studies on the extracts of yellow flowers of Tagetes patula L. against the Heterodera zeae were carried out to identify phytochemicals lethal to this economically important cyst nematode. In vitro investigation of a polar extract and fractions showing activity led to the isolation of phenolic compounds (flavonoids and phenolic acids). In the nonpolar extract, a few fatty acids, their methyl esters, and thiophenes (including α-terthienyl) were detected. In studies of compounds obtained commercially, α-terthienyl and gallic and linoleic acids showed 100% mortality at concentrations of 0.125% after 24 h. Assessment of structure-activity relationships revealed that an increase in the number of hydroxyl groups in phenolic acids increased the activity; with fatty acids, activity depended on chain length and the number and position of double bonds. Crude extracts of the flowers of different colors also have promising activity.

Bioassay-guided isolation of antioxidant agents with analgesic properties from flowers of Tagetes patula

CONTEXT

Tagetes patula L. is one of the French marigold group of the Asteraceae family. It is recognized in folklore for its medicinal and pesticidal properties.

OBJECTIVE

In search of more effective, but non-toxic compounds with antioxidative potential led to the bioassay guided isolation studies on the extracts of T. patula.

MATERIALS AND METHODS

The bioassay on Tagetes patula flowers were carried out guided by in vitro antioxidant activity using DPPH assay. A minor but proven plant constituent methyl protocatechuate (1) was isolated by column chromatography, while patuletin (2) and patulitrin (3) obtained in bulk by employing solvent partition of methanol extract. Derivatization of patuletin into benzoyl, cinnamoyl and methyl was conducted to establish the structure activity relationship (SAR). Analgesic activity of compound 2 was evaluated using acetic acid-induced writhing test and hot-plate test in mice. The toxicity of methanol extract and compound 2 were also determined.

RESULTS

Polar extracts, fractions and phases demonstrated better antioxidant activity. The synthetic methyl protocatechuate (1) showed IC(50) value of 2.8 ± 0.2 μg/mL, whereas patuletin (2) (IC(50) = 4.3 ± 0.25 µg/mL) was comparable to quercetin and rutin but significantly better than patulitrin (3) (IC(50) = 10.17 ± 1.16 µg/mL). Toxicity test for the methanol extract and compound 2 did not elicit any behavioral changes or cause mortality in mice. Compound 2 also demonstrated mild analgesic property.

DISCUSSION AND CONCLUSION

These findings demonstrate that the plant polar extracts and fractions possess significant antioxidant property with non-toxic effect. Compound 1 is a genuine plant constituent of T. patula.