Dalcetrapib
ADCY9 inactivation cuts atherosclerosis by 65 percent in mice, but only when CETP is absent (Circulation 2018)
Original title: ADCY9 (Adenylate Cyclase Type 9) Inactivation Protects From Atherosclerosis Only in the Absence of CETP (Cholesteryl Ester Transfer Protein)
This mouse study tested why ADCY9 genotype determines how the CETP inhibitor dalcetrapib affects cardiovascular events. Adcy9-inactivated mice without the CETP gene showed a 65% reduction in aortic atherosclerosis compared to wild-type mice, along with reduced macrophage accumulation in plaques, improved endothelial-dependent vasorelaxation, and improved autonomic tone. However, when the same Adcy9-inactivated mice were made transgenic for CETP, all of these protective effects on atherosclerosis, endothelial function, weight gain, adipose tissue volume, and feed efficiency were lost. The findings show that ADCY9 inactivation protects against atherosclerosis only in the absence of CETP activity, offering a mechanistic explanation for the pharmacogenomic interaction seen in dalcetrapib trials.
Original abstract
Background: Pharmacogenomic studies have shown that ADCY9 genotype determines the effects of the CETP (cholesteryl ester transfer protein) inhibitor dalcetrapib on cardiovascular events and atherosclerosis imaging. The underlying mechanisms responsible for the interactions between ADCY9 and CETP activity have not yet been determined.
Methods: Adcy9-inactivated ( Adcy9Gt/Gt) and wild-type (WT) mice, that were or not transgenic for the CETP gene (CETPtg Adcy9Gt/Gt and CETPtg Adcy9WT), were submitted to an atherogenic protocol (injection of an AAV8 [adeno-associated virus serotype 8] expressing a PCSK9 [proprotein convertase subtilisin/kexin type 9] gain-of-function variant and 0.75% cholesterol diet for 16 weeks). Atherosclerosis, vasorelaxation, telemetry, and adipose tissue magnetic resonance imaging were evaluated.
Results: Adcy9Gt/Gt mice had a 65% reduction in aortic atherosclerosis compared to WT ( P<0.01). CD68 (cluster of differentiation 68)-positive macrophage accumulation and proliferation in plaques were reduced in Adcy9Gt/Gt mice compared to WT animals ( P<0.05 for both). Femoral artery endothelial-dependent vasorelaxation was improved in Adcy9Gt/Gt mice (versus WT, P<0.01). Selective pharmacological blockade showed that the nitric oxide, cyclooxygenase, and endothelial-dependent hyperpolarization pathways were all responsible for the improvement of vasodilatation in Adcy9Gt/Gt ( P<0.01 for all). Aortic endothelium from Adcy9Gt/Gt mice allowed significantly less adhesion of splenocytes compared to WT ( P<0.05). Adcy9Gt/Gt mice gained more weight than WT with the atherogenic diet; this was associated with an increase in whole body adipose tissue volume ( P<0.01 for both). Feed efficiency was increased in Adcy9Gt/Gt compared to WT mice ( P<0.01), which was accompanied by prolonged cardiac RR interval ( P<0.05) and improved nocturnal heart rate variability ( P=0.0572). Adcy9 inactivation-induced effects on atherosclerosis, endothelial function, weight gain, adipose tissue volume, and feed efficiency were lost in CETPtg Adcy9Gt/Gt mice ( P>0.05 versus CETPtg Adcy9WT).
Conclusions: Adcy9 inactivation protects against atherosclerosis, but only in the absence of CETP activity. This atheroprotection may be explained by decreased macrophage accumulation and proliferation in the arterial wall, and improved endothelial function and autonomic tone.
Summary written by cetpinhibition.org from the published abstract; figures as published. Page updated 18 August 2026. Methods.