Antisense Drug ISIS 301012 Lowers LDL Cholesterol Alone and in Combination with Statins

Linda Brookes, MSc

Disclosures

June 12, 2007

This year's ACC meeting saw data presented from 3 phase 2 studies in the ongoing clinical development of a second-generation antisense drug that reduces the production of apolipoprotein B100 (apoB100). ApoB100 is one of the 2 main isoforms of ApoB, the primary protein of low-density lipoprotein (LDL) cholesterol. The interaction of apoB100 with LDL receptors mediates the uptake of LDL from the liver and peripheral cells. ISIS 301012 is being developed by Isis Pharmaceuticals (Carlsbad, California) and has already been granted orphan drug status for the treatment of homozygous familial hypercholesterolemia in the United States. It is envisaged that it could eventually be used as an add-on to statins in patients with familial or nonfamilial hypercholesterolemia who at risk and unable to achieve target LDL levels with statins and ezetimibe, or as an alternative for patients who are intolerant of statins.

The results of a randomized, double-blind, placebo-controlled, dose-escalation study were reported by lead investigator John JP Kastelein, MD, PhD (Academic Medical Center, Amsterdam, The Netherlands), who is an advisory board member for Isis.[1] The study initially included 5 weeks of treatment with ISIS 301012 at doses of 30, 100, 200, and 300 mg/week. ISIS 301012 showed potent, dose-dependent, and prolonged reductions in lipids and was well tolerated in these cohorts, so the study was expanded to include a 400 mg/week 5-week treatment group and 2 longer term treatment cohorts (200 or 300 mg/week for 3 months). Dr. Kastelein presented the results from the 400 mg/week cohort; results from the longer term cohorts will be presented later in the year.

 

Study Design

The study population comprised 50 subjects with median baseline LDL cholesterol 107-168 mg/dL who had been on a stable dose of atorvastatin or simvastatin ≤ 40 mg/day for ≥ 3 months. Mean duration of statin treatment was 4 years. Subjects (10 per dose group) were randomized 4:1 to receive 30, 100, 200, 300 or 400 mg/dose of ISIS 301012 or placebo, respectively. The study drug was administered by subcutaneous injection using a loading regimen in the first week (3 doses) followed by once-weekly doses for 3 additional weeks. The primary endpoint for these cohorts was the percentage reduction in LDL cholesterol 30 days after the last dose (Day 59).

 

Results

At a dose of 400 mg/week, patients receiving ISIS 301012 achieved median reductions of 47% in LDL cholesterol (P = .008 vs baseline) and 51% in apoB (P = .0004) beyond the levels already achieved on stable statin doses ( Table 1 ). This did not reflect further lipid-lowering activity over the 300 mg dose, but Dr. Kastelein explained that this may have reflected lower baseline levels of both LDL cholesterol and apoB in the 300 mg/week dose group compared with the 400 mg/week dose group (168 vs 138 mg/dL and 133 vs 110 mg/dL, respectively). He pointed out that the 400 mg/week cohort achieved lower median absolute levels of both apoB (55 vs 61 mg/dL at 300 mg/week) and LDL cholesterol (67 mg/dL at 400 mg/week vs 76 mg/dL at 300 mg/week) than the 300 mg/week cohort. ISIS 301012 400 mg/week was associated with a median reduction of 35% in triglycerides (P = .02 vs baseline) incremental to statin therapy, but there was no effect on levels of HDL cholesterol.

At the 400 mg/week dose, 4 of 8 patients achieved NCEP/ATP III LDL cholesterol levels < 70 mg/dL and 6 of 8 achieved LDL cholesterol levels < 100 mg/dL. Similarly, at a dose of 300 mg/week, 3 of 8 patients achieved LDL cholesterol levels < 70 mg/dL and 7 of 8 patients achieved LDL cholesterol levels below 100 mg/dL.

Side Effects

The most common drug-related adverse event was transient, painless erythema at the site of injection in 44 subjects (90%). Serious adverse events included fever in 1 patient taking 400 mg/week (possibly related to the study drug), and a myocardial infarction in another (unknown relationship to study drug). In the high dose cohort, one patient had consecutive measurements of liver transaminases (ALT) > 3 times the upper limit of normal (3 × ULN); the maximum ALT observed in the study was 211 IU/L. No clinically significant changes were noted in albumin or prothrombin, and although occasional ALT elevations 3 × ULN were observed, there were no elevations in bilirubin >2 ×ULN. No effects of ISIS 301012 were seen on hematological parameters, renal function chemistry or urinary protein, and no elevations in muscle-based creatine phosphokinase were recorded. "These data are very reassuring," Dr. Kastelein said.

 

Conclusion

According to Dr. Kastelein, "ISIS 301012 continues to show exceptional promise as a new lipid-lowering agent. This study demonstrates that as an add-on therapy in patients on statins whose LDL cholesterol levels are not adequately controlled, ISIS 301012 effectively enables patients to achieve target levels of LDL cholesterol. Its important clinical effect, together its tolerability and lack of drug interactions, make ISIS 301012 an exciting drug for potential use in combination with other lipid-lowering therapies in the patients unable to derive sufficient benefit from available agents."

Later this year, Isis plans to begin a longer-duration phase 2 study of ISIS 301012 added to statins in patients with routine high cholesterol to define maintenance doses of ISIS 301012 which are expected to be in the range of 100-200 mg/week.

 

Monotherapy Study

Earlier, new data from a study with ISIS 301012 400 mg/week as monotherapy were presented by Evan Stein, MD, PhD (Metabolic & Atherosclerosis Research Center, Cincinnati, Ohio), who is also an advisory board member for Isis.[2] This randomized, double-blinded, placebo-controlled, dose-escalation trial involved subjects with high cholesterol (baseline median LDL cholesterol 154-206 mg/dL). Subjects (10 per dose group) were randomized 4:1 to receive ISIS 301210 at 50, 100, 200, 300, or 400 mg/week or placebo. The primary endpoint of the study was percent LDL cholesterol reduction 14 days after the last dose. The results for the 50-300 mg/week doses showed potent, dose-dependent and prolonged reductions in LDL cholesterol and other apoB-containing lipoproteins. By 10 weeks into the protocol-specified 13-week dosing period, all 8 treated patients in the 400 mg/week dose cohort had levels of apoB-100 that were at or below the lower limit of normal (< 60 mg/dL), and 4 had undetectable levels of apoB-100 (< 35 mg/dL). Because further activity was not measurable, dosing was discontinued and patients progressed directly into follow-up. All 8 patients were evaluable per protocol. At this time they showed median reductions of 70% in LDL cholesterol (P < .0001 vs placebo), 65% in non-HDL cholesterol (P < .0001), 56% in total cholesterol (P < .0001), and 53% in triglycerides (P = .02) ( Table 2 ).

All 8 patients in the 400 mg/week dose cohort achieved LDL cholesterol levels < 100 mg/dL target and 6 of 8 achieved LDL cholesterol levels < 70 mg/dL. After dosing, LDL cholesterol levels for these patients ranged from 24 to 97 mg/dL.According to Dr. Stein, these data confirmed that, unlike statins, ISIS 301012 causes linearly increasing reductions of atherogenic lipids as doses are increased. At doses that decreased LDL cholesterol and apoB > 50%, there were modest reductions in HDL-cholesterol as measured via the protocol-specified, but nonstandardized, liquid detergent homogenous assay; these results were contradicted when samples were re-evaluated in a blinded manner by a Centers for Disease Control part III-standardized reference laboratory performing the more accurate dextran sulfate precipitation assay. The ratios of apoB to apoA-1 and total cholesterol to HDL cholesterol showed dose-dependent favorable decreases throughout the dose range.

Side Effects

ISIS 301012 was well tolerated through 400 mg/week. There were no drug-related serious adverse events in the study, and the most common drug-related adverse events were painless mild to moderate injection site reactions. Elevations in liver transaminases (ALT) were observed in the high-dose cohort; 5 of the 8 patients dosed at 400 mg/week, including all 4 patients with undetectable levels of apoB, experienced modest ALT elevations at or above 3 × ULN. No patients experienced ALT elevations > 5 × ULN; the maximal ALT observed was 241 IU/L. Importantly, no patients had liver chemistries suggestive risk of injury (extremely high ALT or ALT elevations plus elevations in bilirubin > 2 × ULN). Dr. Stein suggests that the mild increases in ALT at the 400 mg/week dose likely reflect extreme lipid-lowering activity, not toxicity, and are consistent with perturbations in liver chemistries seen with statins. There were no effects on kidney function.

 

Future Dosing Considerations

During the ACC meeting, Isis announced that with the potent and broad lipid-lowering activity seen at 200 and 300 mg/week, the 400 mg/week dose will not advance into registration studies. "We continue to be encouraged by the performance of ISIS 301012, and look forward to initiating a longer-term phase 2 study in patients with routine high cholesterol in combination with statins in which we will define induction and maintenance doses. We expect induction doses to be 200 to 300 mg/week and maintenance doses to be 100 to 200 mg/week. In addition, later this year we will begin our registration program for familial hypercholesterolemia," a company release said.

Earlier in the meeting, Dr. Stein presented data for 3 patients from an ongoing phase 2 clinical trial for ISIS 301012 in patients with homozygous familial hypercholesterolemia already being treated with maximally tolerated lipid-lowering therapies.[3] Two patients had completed at ≥ 11 weeks of dosing at 300 mg/week of ISIS 301012 added to ongoing lipid-lowering therapies and showed ≥ 50% further reductions in LDL cholesterol, with similar effects on apoB and other apoB-containing lipoproteins and triglycerides. The third patient had apoB and LDL cholesterol reductions of 29% and 32%, respectively, after 6 weeks of dosing. High-density lipoprotein cholesterol remained stable or increased slightly in these patients. ISIS 301012 was well tolerated in the study. Isis plans to begin registration-directed studies for familial hypercholesterolemia in 2007.

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