From the Guidelines

Red yeast rice (RYR) is as effective as low-to-moderate intensity statin therapy in reducing low-density lipoprotein cholesterol (LDL-C) levels.

RYR has been shown to decrease LDL-C levels by 20-30% and reduce triglycerides by 15-25% 1, similar to the effects observed with statin therapy.
The efficacy of RYR is thought to be attributed to its active component, monacolin K, which is a potent inhibitor of HMG-CoA reductase, similar to the mechanism of action of statins such as atorvastatin 10mg or rosuvastatin 5mg 1.
Studies have demonstrated that RYR can reduce recurrent events by 45% in patients with coronary artery disease (CAD) 1, and statin therapy can reduce the risk of cardiovascular events by approximately 21% per 1-mmol/L LDL-C reduction 1.

RYR has a comparable efficacy to low-to-moderate intensity statin therapy, such as pravastatin 20mg or simvastatin 10mg, when administered at a dose of 1200-2400mg per day for a duration of 8-12 weeks.
The benefits of RYR and statin therapy are inextricably linked to LDL cholesterol lowering, with each 1.0 mmol/L (~40 mg/dL) reduction in LDL cholesterol associated with a 22% reduction in major vascular events and a 10% reduction in all-cause mortality 1.

From the Research

The extracts of red yeast rice (RYR) have been shown to be effective in lowering low-density lipoprotein (LDL)-cholesterol plasma levels by 15% to 25% within 6 to 8 weeks, with a similar effect to low-dose, first-generation statins in subjects with mild-to-moderate dyslipidemia 2, 3, 4.
RYR supplementation has been found to reduce LDL-C levels by approximately 15-34% versus placebo, with a beneficial reduction of up to 45% versus placebo in the risk of atherosclerotic cardiovascular disease (ASCVD) events in secondary prevention studies 4.
Compared to statins, RYR has been shown to have an equal efficacy when combined with or without other dietary supplements, and appeared to be superior to placebo in preventing nonfatal myocardial infarction, total coronary heart disease events, and total deaths 5.

The main cholesterol-lowering component of RYR is monacolin K, which is structurally identical to lovastatin and targets the same key enzyme of cholesterol biosynthesis, with a daily consumption of 3 to 10 mg monacolin K having minimal associated risks, such as mild myalgia in previously severely statin-intolerant subjects 2, 3, 4.
RYR has been found to be well tolerated, with an adverse event profile similar to that of low-dose statins, and can be used as a treatment option for lowering LDL-C levels and ASCVD risk for people with mild-to-moderate hypercholesterolemia who are ineligible for statin therapy or unwilling to take pharmacologic therapy 4.

Clinical trials have shown that RYR significantly lowers LDL cholesterol and total cholesterol, with effects on triglycerides and HDL cholesterol also observed in some studies 5, 6.
A randomized clinical efficacy trial found that monacolin K-rich RYR can reduce cholesterol as expected, while GABA-rich RYR performed non-significant reduction on serum triglyceride, suggesting that using different concentrations and ratios between monacolin K and GABA could be beneficial for antihyperlipidemia 6.