rs20455 — KIF6 Trp719Arg

Missense variant in kinesin family member 6; the Arg allele was associated with elevated coronary heart disease risk and with substantially greater benefit from statin therapy in the CARE, WOSCOPS, PROSPER, and PROVE IT-TIMI 22 trials, though a large meta-analysis of 19 case-control studies found no independent CAD risk association

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KIF6 Trp719Arg — Statin Response and the Coronary Risk Controversy

Inside the nucleus and cytoplasm of every cell, molecular motors called kinesins ferry cargo along microtubule tracks. KIF6 (kinesin family member 6) is one of these motors, and while its precise cellular role is still being worked out, it has attracted intense scrutiny for one reason: a common amino acid variant at position 719 — swapping tryptophan for arginine — appeared in large prospective trials to dramatically reshape who benefits from statin therapy.

The Mechanism

The Trp719Arg substitution (plus-strand G allele at chr6:39357302) changes an uncharged, bulky amino acid (tryptophan) to a positively charged one (arginine) in the tail domain of the KIF6 motor protein. KIF6 is expressed in cardiomyocytes, smooth muscle cells, and cilia, where it is thought to regulate cytoskeletal dynamics and intracellular vesicle transport. The exact mechanism connecting the 719Arg variant to cardiovascular risk and statin sensitivity remains incompletely characterized — the statin interaction notably occurs independently of LDL cholesterol lowering11 occurs independently of LDL cholesterol lowering
the benefit was observed without differences in LDL or CRP between groups, suggesting a non-lipid pathway, pointing toward a direct effect on cell signaling or endothelial biology.

The Evidence

The KIF6 story has two chapters: an exciting initial phase and a sobering replication phase.

Chapter 1 — The original trials. In 2008, Iakoubova et al. published a cluster of studies from four major randomized controlled trials. In the CARE and WOSCOPS trials22 CARE and WOSCOPS trials, 719Arg carriers on placebo had a 50–55% higher risk of coronary events than non-carriers (CARE HR 1.50, 95% CI 1.05–2.15; WOSCOPS OR 1.55, 95% CI 1.14–2.09). Pravastatin reduced their absolute risk by 4.89% (CARE) and 5.49% (WOSCOPS) — while providing near-zero benefit in non-carriers. The PROVE IT-TIMI 22 trial33 PROVE IT-TIMI 22 trial in acute coronary syndrome patients showed that intensive statin therapy halved event rates in 719Arg carriers (HR 0.59) but had no significant effect in non-carriers (HR 0.94), with an interaction p = 0.018 and a 10% vs. 0.8% absolute risk reduction. The PROSPER trial44 PROSPER trial in elderly patients confirmed the pattern: in carriers with prior vascular disease, pravastatin HR was 0.66 vs. 0.94 in non-carriers. A meta-review of all four trials55 meta-review of all four trials yielded number-needed-to-treat of 10–20 for 719Arg carriers versus over 80 for non-carriers — a striking pharmacogenomic signal.

Chapter 2 — The replication crisis. In 2010, Assimes et al. published a definitive replication attempt66 definitive replication attempt in 19 independent case-control studies comprising 17,000 cases and 39,369 controls across multiple ancestries. None of the 19 studies showed increased CAD risk in 719Arg carriers; the meta-analysis ruled out with high confidence even a 2% risk increase in Europeans. A 2018 pooled analysis77 pooled analysis of 50 studies (40,059 cases, 64,032 controls) confirmed: OR 1.007 under the homozygote model, p = 0.801 — no CAD association. The original risk signal88 original risk signal appears to have been a survival bias artefact specific to the prospective cohort design.

The current position. The CAD risk association from Chapter 1 is not supported by the larger replication literature. The pharmacogenomic statin-response signal is more robust — it has been replicated in multiple trials under consistent analytical frameworks — though it also has not been incorporated into CPIC or DPWG clinical guidelines and the mechanistic explanation is incomplete.

Practical Actions

The ~59% of people who carry at least one G (Arg) allele have moderate-strength evidence that they will derive greater-than-average benefit from statin therapy if they develop cardiovascular risk factors. Non-carriers have multiple large trials suggesting pravastatin and possibly other statins may offer them materially less benefit per unit of drug. This genotype does not determine whether to start a statin — that decision depends on absolute cardiovascular risk — but it can inform the relative priority of statin initiation when the clinical picture is borderline, and it may support discussion of statin choice and dose intensity with a cardiologist.

Interactions

KIF6 rs20455 was one of five variants in a composite CHD genetic risk score (ARIC cohort, Bare 2007, PMID 18073581)99 composite CHD genetic risk score (ARIC cohort, Bare 2007, PMID 18073581) alongside rs2298566 (SNX19), rs3900940 (MYH15), rs7439293 (PALLD), and rs1010 (VAMP8). Those with a high score across all five variants had HR 1.57 for incident CHD over 13 years. The combined score performed better than any individual variant alone, suggesting these variants capture partially independent biological pathways. Within the KIF6 locus, rs20455 is in high linkage disequilibrium (r² > 0.84) with rs9462535 and rs9471077, which show the same statin-differential pattern.

Drug Interactions

pravastatin reduced_efficacy literature
atorvastatin reduced_efficacy literature
rosuvastatin reduced_efficacy literature

Genotype Interpretations

What each possible genotype means for this variant.

AA Non-carrier Normal

No KIF6 Trp719Arg variant — typical baseline statin response

In the CARE trial, non-carriers showed a hazard ratio of 1.01 for pravastatin vs. placebo — effectively no benefit — while Arg carriers had HR 0.63–0.64. In PROVE IT-TIMI 22, non-carrier HR was 0.94 (not significant), versus 0.59 in carriers. This genotype does not mean statins are harmful or ineffective — it means the pharmacogenomic advantage documented in carriers does not apply. Statin decisions should still be based on absolute cardiovascular risk and lipid panel results. Other statins (e.g. rosuvastatin, simvastatin) have not been tested for this interaction specifically, so the finding cannot be generalized to all statin therapy.

AG Carrier Intermediate

Carries one Arg allele — enhanced benefit from statin therapy

The original trial data (CARE, WOSCOPS, PROSPER, PROVE IT-TIMI 22) consistently showed that 719Arg carriers — heterozygous and homozygous pooled as ~59% of each cohort — had both elevated baseline coronary risk (in the prospective designs) and much greater absolute event reduction with statin therapy. The statin-benefit signal has not been adopted into formal CPIC or DPWG prescribing guidelines, as independent replication of the statin-differential in other trial designs has been limited. The effect may be stronger for pravastatin specifically, based on the available data.

GG Homozygous Carrier High Risk

Carries two Arg alleles — likely maximal statin benefit, elevated baseline risk

In the CARE trial analysis (Shiffman et al. 2010), the hazard ratio for pravastatin vs. placebo in all 719Arg carriers was 0.63–0.64 for coronary endpoints, a robust finding across ethnic groups. The absolute risk reduction for intensive vs. moderate statin therapy in the PROVE IT-TIMI 22 trial was 10.0% in carriers vs. 0.8% in non-carriers. Homozygous carriers, being fully "loaded" at both alleles, are expected to occupy the high end of this pharmacogenomic response gradient. The mechanistic basis — likely independent of LDL cholesterol lowering given that lipid and CRP differences between groups were not observed — points toward cytoskeletal or endothelial pathways not yet fully characterized.