I tend to think that low LDL patients respond better because they are good at taking medicine be it Apabetalone or statins. Adherence to lipid lowering drugs can be quite low, cf. quote below, such failure to take statins could also be the case for Apabetalone. I would really like to see plasma analyses for Apabetalone.

Adherence to lipid-lowering medications increases the success rate for attaining LDL cholesterol goals. Clinical trials demonstrate statin adherence rates of 80% to 87% over a period of three to four years.12 A study looking at pharmacy insurance claims projected an adherence rate of 78.5% in adults prescribed statin therapy for secondary prevention.13However, a study of elderly patients found an adherence rate of 36.1% in patients with coronary artery disease.14 Therefore, it is important for clinicians to assess medication adherence before changing therapy when clinical goals are not met. 15