CHICAGO – Both methotrexate and canakinumab are anti-inflammatory drugs, but only canakinumab cut the incidence of cardiovascular disease events in a major clinical trial, CANTOS. A second big trial designed to parallel CANTOS tested methotrexate in roughly the same way and found it produced no cardiovascular disease benefit among high-risk patients.
Mitchel L. Zoler/MDedge News
Dr. Paul M. Ridker
The CANTOS (Canakinumab Anti-inflammatory Thrombosis Outcome Study) results with canakinumab and the new results with methotrexate “demonstrate that inflammation inhibition [with canakinumab] can significantly reduce cardiovascular event rates independent of lipid lowering and blood pressure reduction,” Paul M. Ridker, MD, said at the American Heart Association scientific sessions. But, “inhibition of the IL [interleukin]–1 beta to IL-6 to CRP [C-reactive protein] pathway of innate immunity appears to be important for atheroprotection,” and was something methotrexate couldn’t deliver, concluded Dr. Ridker, a professor of medicine at Harvard Medical School and director of the Center for Cardiovascular Disease Prevention at Brigham and Women’s Hospital in Boston.
The new results he reported showed that weekly treatment with a single, oral, 15- to 20-mg dose of methotrexate not only had no effect on cardiovascular events but also had no discernible impact on serum levels of IL-1beta (IL-1B), IL-6, or high sensitivity (hs) CRP, in contrast to canakinumab, which Dr. Ridker took as evidence that this inflammatory pathway links to the pathophysiology of atherosclerotic cardiovascular disease.
CIRT (Cardiovascular Inflammation Reduction Trial) randomized 4,786 patients at 417 centers in the United States or Canada. Enrolled patients had to have a history of an MI or documented multivessel coronary disease, and also had to have type 2 diabetes, metabolic syndrome, or both. All patients were maintained on optimized dosages of a statin, aspirin, a beta-blocker, and an angiotensin-converting enzyme inhibitor or angiotensin-receptor blocker. All patients also received 1 mg folate daily. Randomization assigned patients to either receive 15-20 mg methotrexate orally once a week or placebo.
CIRT stopped prematurely because of futility after a median follow-up of 2.3 years. At that time, the incidence of one of two primary endpoints, the combination of cardiovascular death, nonfatal MI, and nonfatal stroke was 3.46/100 person-years with methotrexate treatment and 3.43/100 person-years with placebo, a difference that was not statistically significant. The incidence of the second primary endpoint, which combined the first three types of events plus hospitalization for unstable angina that led to urgent coronary revascularization, occurred in 4.13/100 person-years with methotrexate and 4.31/100 person years with placebo, also a difference that was not statistically significant. Concurrently with this report, the results were published online (N Engl J Med. 2018 Nov 10. doi: 10.1056/NEJMoa1809798).
Analysis of inflammatory markers in the blood after 8 months on treatment showed that methotrexate had no effect on levels of IL-1B, IL-6, and hsCRP. Methotrexate’s lack of an effect on these markers as well as the absence of an effect on cardiovascular disease events contrasted sharply with results that Dr. Ridker and his associates reported a little more than a year earlier in CANTOS. The study’s investigators randomized 10,061 patients with a history of an MI and an elevated serum level of hsCRP, at least 2.0 mg/L. After a median follow-up of 3.7 years, treatment with 150 mg of canakinumab injected subcutaneously once every 3 months produced a 15% relative risk reduction in the combined rate of cardiovascular death, nonfatal MI, and nonfatal stroke, compared with patients treated with placebo, a statistically significant between-group difference (N Engl J Med. 2017 Sep 21;377[12]:1119-31). Canakinumab had no impact on LDL cholesterol levels, but lowered hsCRP levels by more than a third. Dr. Ridker and his associates designed the CIRT and CANTOS trials “in parallel,” he said, and the CIRT results using methotrexate provided a “neutral control” to complement the positive results from canakinumab in CANTOS,
Given its high cost, canakinumab (Ilaris) is not an obviously practical option for treating patients similar to those enrolled in CANTOS, so other candidate agents that inhibit the IL-1B, IL-6, CRP inflammatory pathway are now under study, Dr. Ridker said in an interview. The mechanism of methotrexate’s inhibition of inflammation is unknown, but clearly does not involve this pathway; it may be mediated by adenosine, Dr. Ridker suggested. Canakinumab has Food and Drug Administration approval for treating systemic juvenile idiopathic arthritis and a handful of additional, low-prevalence diseases. Novartis, the company that markets canakinumab, made a submission to the Food and Drug Administration seeking an indication for prevention of cardiovascular disease based on the CANTOS results, and the company said in October 2018 that the FDA denied this request.
The CIRT results also showed a previously unseen signal of a possible safety issue with the tested methotrexate regimen. The incidence of non–basal cell skin cancer was 0.65/100 person-years with methotrexate, compared with 0.24/100 person-years with placebo, a statistically significant difference. Until now, no one had reported a link like this and it requires further analysis, Dr. Ridker said.
CIRT received no commercial funding. Dr. Ridker has been a consultant to Corvidia, Inflazome, and Novartis; he has received research funding from Kowa and Novartis; and his work led to a patent held by Brigham and Women’s Hospital for inflammatory biomarkers licensed to Siemens and AstraZeneca.
SOURCE: Ridker P et al. AHA scientific sessions, Abstract 17778.