Background Beyond their potent LDL (low-density lipoprotein) cholesterol ( LDL -C)-lowering efficacy (50-60%), PCSK9 (proprotein convertase subtilisin/kexin type 9) inhibitors also reduce Lp(a) (lipoprotein[a]) levels by 25% to 30%, suggesting a 2:1 response ratio. We aimed to characterize the relationship between LDL -C and Lp(a) lowering by evolocumab, a PCSK 9 inhibitor, in a large clinical trial population and to determine the prevalence of concordant/discordant LDL -C and Lp(a) responses to PCSK 9 inhibition. Methods and Results Data were analyzed from 4 randomized, 12-week, multicenter, phase 3 evolocumab trials. Patients with familial hypercholesterolemia, nonfamilial hypercholesterolemia, or statin intolerance participated in the trials. The main measure was the degree of concordance or discordance of LDL -C and Lp(a) in response to PCSK 9 inhibition; concordant response was defined as LDL -C reduction >35% and Lp(a) reduction >10%. The study cohort comprised 895 patients (438 female; median age: 59.0 years [interquartile range: 51-66 years]). Baseline mean level of LDL -C was 133.6 mg/dL (SE: 1.7) and median Lp(a) level was 46.4 mg/dL (interquartile range: 18.4-82.4 mg/dL). A discordant response was observed in 165 (19.7%) patients. With these cutoffs, the prevalence of discordance was higher when considering baseline Lp(a) concentrations >30 mg/dL (26.5%) or >50 mg/dL (28.6%). Conclusions We demonstrate high prevalence of discordance in LDL -C and Lp(a) reduction in response to evolocumab, particularly when considering higher baseline Lp(a) concentrations, indicating the possibility of alternative pathways beyond LDLR ( LDL receptor)-mediated clearance involved in Lp(a) reduction by evolocumab. Clinical Trial Registration URL : http://www.clinicaltrials.gov . Unique identifiers: NCT 01763827, NCT 01763866, NCT 01763905, NCT 01763918.