LONDON – Despite very promising activity in animal models of idiopathic pulmonary fibrosis (IPF), a monoclonal antibody targeted at an enzyme considered to be important to collagen cross-linking did not produce any improvement in progression-free survival (PFS), according to results of a multicenter study presented at the annual congress of the European Respiratory Society.
“This was such a negative study, there is no point in doing another,” reported Ganesh Raghu, MD, director of the Pulmonary Fibrosis Program at the University of Washington Medical Center, Seattle.
Dr. Ganesh Raghu
The focus of this study was simtuzumab, a monoclonal antibody targeted at lysyl oxidase like 2 (LOXL2), an enzyme which catalyzes a step in the formation of collagen crosslinks, which are thought to be important in fibrosis formation. Simtuzumab has been entered into clinical trials for treatment of several forms of fibrosis, including fibrosis in the liver.
“In animal models, simtuzumab has demonstrated efficacy in reducing fibrosis when administered prior to fibrosis formation or after the process has already begun,” Dr. Raghu explained. He said a large trial was initiated in IPF because the agent seemed so promising and because a large study was thought to be the best strategy to arrive at a definitive answer regarding safety and efficacy.
The drug was found safe but not effective. The independent data monitoring and safety committee terminated the trial early for futility.
In the study, 544 IPF patients were randomized to 125 mg simtuzumab or placebo administered subcutaneously once weekly. The primary endpoint was PFS, but there were a large number of secondary endpoints including hospitalization for progressive disease, change in 6-minute walk distance (6MWD), and overall survival.
For the endpoint of PFS, “there was absolutely no difference” between the groups receiving simtuzumab or placebo. When the patients were stratified for demonstrating above or below median expression of LOXL2, which was a prespecified analysis for the trial, there was still no difference between groups. Even when those in the top quarter percentile of LOXL2 expression were compared with those with less [expression of the enzyme], there was still “absolutely no difference.”
There was also no significant evidence of benefit for simtuzumab observed on key secondary endpoints, such as overall survival. When patients were stratified by baseline lung function as expressed by percentage of predicted forced expiratory volume in 1 second (FEV1), there was no signal of benefit for those with severe, moderate, or mild impairment.
One criticism of this study raised after the presentation was that patients with 26% or greater of predicted FEV1 were permitted into the study. It was suggested that such patients would be expected to already have a high degree of fibrosis and therefore would be less likely to benefit from an antifibrosis therapy. Dr. Raghu acknowledged this criticism, but he said it was important to include patients with advanced disease in order to generate an adequate event rate. Even with inclusion of patients with severe lung impairment, the mortality rate was less than 10%.
He concluded that there was no signal of benefit even among those with the greatest expression of the target.
“We absolutely need better markers for IPF,” Dr. Raghu maintained. While other members of the LOXL family of enzymes may still prove to be valuable markers of IPF risk and targets of therapy, these data appear to rule out a therapeutic role for blocking LOXL2.
Dr. Raghu is a consultant for Boehringer Ingelheim, Biogen, FibroGen, Gilead, Janssen, MedImmune, Promedior, Sanofi-Aventis, and Veracyte.