The maximum median percentage change in serum Lp(a) out to day 337 of follow-up was 5% reduction in the placebo group. In the active treatment groups, the reductions were 41% on 4 mg, 59% on 12 mg, 76% on 32 mg, 96% on 304 mg, and 97% on 608 mg.
These reductions were generally sustained for as long as therapy was maintained. Maximal reductions were reached at day 85 in the 4-mg group but were achieved by day 29 in the 605-mg group, Dr. Nissen reported. In fact, serum Lp(a) was undetectable in the 605-mg group at day 29 and remained so until day 281.
Currently, there is no practical treatment for Lp(a). The only potential exception, apheresis, is “cumbersome” to perform and must be repeated for sustained reductions. Niacin and PCSK9 inhibitors are known to provide modest reductions in Lp(a), but Dr. Nissen said they are too modest to expect a meaningful clinical benefit.
Lp(a) not responsive to lifestyle changes
Statins as well as all lifestyle modifications, including diet, have been shown to have “little or no effect,” Dr. Nissen said.
The safety and the evidence so far of sustained Lp(a) lowering has already led to a phase 2 trial, according to Dr. Nissen, but the more important test for the future of lepodisiran will be studies powered to confirm reductions in MACE. Lepodisiran may finally allow that hypothesis to be tested.
“I think a lot of us have been waiting a long time for evidence that we can reliably reduce Lp(a),” said Karol Watson, MD, PhD, who has a research interest in lipids and is a professor of medicine at the University of California, Los Angeles.
Although she conceded that the overwhelming evidence that Lp(a) is a risk factor does not ensure that any specific Lp(a)-lowering therapy will be clinically viable, she suggested this drug is a promising candidate to move this field forward.
“At the highest doses, lepodisiran is not just lowering Lp(a), it appears to be getting rid of it,” she said.
Dr. O’Donoghue said that the phase 1 results suggest lepodisiran might have a somewhat longer duration of action than other siRNA therapies studied for Lp(a) so far, but said larger trials are needed to determine whether the growing number of drugs in this class differ in ways that are clinically meaningful.
Overall, the excitement in this field is probably mostly driven by the fact that there are so many promising therapies for Lp(a) that address the target in so many unique ways. Dr. O’Donoghue cited, as an example, a gene-editing therapy called CTX320 that showed impressive effects in an animal study presented at the AHA meeting as a poster. She called the pipeline for treating Lp(a) “rich.”
Elevated Lp(a) is genetically determined, so levels do not generally change over time, said Donald Lloyd-Jones, MD, chair of the department of preventive medicine, Northwestern Medicine, Chicago.
“It is not affected by your diet. It is not affected by your exercise. What your level is will be the level you will have for the rest of your life,” he said. Generally, it is recommended to have Lp(a) measured just once to more accurately calculate cardiovascular risk, but Dr. Lloyd-Jones predicted that this lipid subfraction might be measured more frequently to verify control if a therapeutic becomes available.
Dr. Nissen agreed. Estimating that 64 million people in the United States have significantly elevated Lp(a), he expects this risk to be addressed as a specific and independent target in CV risk management when and if it becomes treatable.
Dr. Nissen reported financial relationships with Novartis, Silence Therapeutics, and Eli Lilly, which provided funding for this trial. Dr. Watson reported financial relationships with Amgen, Boehringer Ingelheim, Lilly, and Novartis. Dr. Lloyd-Jones disclosed no relevant financial relationships.
A version of this article first appeared on Medscape.com.