WASHINGTON – Acute respiratory distress syndrome (ARDS) appears to exist in at least two major forms, and one of these, the hyperinflammatory form, seemed responsive to simvastatin in a post-hoc analysis of trial data.

The other version of ARDs is a hypoinflammatory form, which occurred in 70% of ARDS patients in most of the analyses that have been done.

Researchers classified the 540 ARDS patients enrolled in a 2014 study of simvastatin as either hyperinflammatory or hypoinflammatory. Separating out the hyperinflammatory patients created a subclass that responded to simvastatin, with a 13% absolute reduction in mortality during follow-up, compared with no response among patients in the hypoinflammatory group, Carolyn S. Calfee, MD, said at an international conference of the American Thoracic Society.

“Hyperinflammatory patients treated with simvastatin may have improved outcomes, compared with hypoinflammatory* patients treated with placebo,” said Dr. Calfee, a pulmonologist at the University of California, San Francisco.

The finding raises the possibility that simvastatin, as well as other statins, may be an effective treatment for selected patients with ARDS, but proving this requires new prospective, randomized trials in hyperinflammatory patients, Dr. Calfee said in a video interview.

Currently, the tests Dr. Calfee uses to distinguish hyperinflammatory and hypoinflammatory ARDS patients take about 6-8 hours to complete. A “point of care test to stratify patients in real time,” is needed to further study the various forms of ARDs, Dr. Calfee noted. A critical next step would be the development of a “practical, rapid, bedside assay” to ease identification of hyperinflammatory ARDS patients. “The work we’ve done prior seems to indicate that we are going to definitely need to measure biomarkers in order to identity these subgroups,” she noted.

Hypoinflammatory patients also merit study, she added. Although hyperinflammatory patients have significant worse mortality rates, the hypoinflammatory subclass includes about 70% of ARDS patients, “so we need to better understand how to potentially treat this group.”

Dr. Calfee and her associates first reported finding the two ARDS subclasses, what they also call subphenotypes or endotypes, in two separate cohorts of ARDS patients in a 2014 report (Lancet Resp Med. 2014 Aug;2[8]:611-20). Then, they confirmed the finding in a third ARDS cohort in a 2017 report (Amer J Resp Crit Care Med. 2017 Feb 1;195[3]:331-8). These reports have documented other characteristics of the hyperinflammatory ARDS subclass: hypotension, metabolic acidosis, more frequent treatment with vasopressors, and a higher prevalence of sepsis and shock. Concurrent with the 2017 report, an editorial hailed the finding as “the dawn of personalized medicine for ARDS” (Amer J resp Crit Care Med. 2017 Feb 1;195[3]: 280-1).

To build on this, Dr. Calfee and her associates applied their method for identifying ARDS subclasses to a different cohort of 540 patients enrolled in the The HARP (Hydroxymethylglutaryl-CoA Reductase Inhibition with Simvastatin in Acute Lung Injury to Reduce Pulmonary Dysfunction)–2 study, a multicenter UK and Irish study designed to test the efficacy of daily simvastatin treatment in a heterogeneous group of ARDS patients. A 2014 report of the study’s primary results showed no significant effect from simvastatin for increasing the number of ventilator-free days nor did the drug improve any other measured efficacy endpoints (New Engl J Med. 2014 Oct 30;371[18]:1695-703).

Applying a statistical analysis called “latent class analysis,” which is designed to recognize subclass groupings that might not be readily apparent, Dr. Calfee and her team first confirmed that, in this fourth cohort, the ARDS patients again split into a hyperinflammatory subclass, in this case including 188 (35%) of the cohort, and a hypoinflammatory subclass with 352 (65%) patients. The next step was to see what impact simvastatin treatment had in each of the two patient subclasses. They focused the analysis on a secondary outcome in HARP-2, 28-day survival.

They found that simvastatin produced no significant difference in 28-day survival, compared with placebo among the hypoinflammatory patients, but, in the hyperinflammatory subclass, 28-day survival was 68% for patients on simvastatin and 55% for those on placebo, a statistically significant difference, Dr. Calfee reported (Am J Resp Crit Care Med. 2017;195:A6749).

“I’m excited that we are seeing, for the first time, a different response to pharmacotherapy” after dividing ARDS patients into these two subclasses, she said. But, the work remains in an early stage, she cautioned. “We need to test treatments [like statins] prospectively.” The new finding for simvastatin “is not the same as showing benefit in a prospective, randomized trial.”

In the meantime, Dr. Calfee plans to apply the same analytic approach to data collected in another failed statin trial in ARDS patients, the SAILS trial. That study failed to show benefit from rosuvastatin treatment in an unselected population of patients with sepsis-associated ARDS (New Engl J Med. 2014 June 5;370[23]:2191-200).

Dr. Calfee is a consultant to Bayer, Boehringer Ingelheim, and GlaxoSmithKline. She received research funding from GlaxoSmithKline.

mzoler@frontlinemedcom.com

On Twitter @mitchelzoler

*An earlier version of this article misquoted Dr. Calfee.

VIDEO: Hyperinflammatory ARDS responds to simvastatin