From the Authors:We thank Dr. Horita and Dr. Takeshi for their interest and important comments regarding our recent randomized trial (1).The 90-day survival proportion in the non–thrombomodulin alfa arm was much higher than that in previous reports (2–4), as indicated by Horita and Takeshi. Indeed, as well as the 90-day survival proportion in the placebo group, the 90-day survival proportion in all subjects included in the full analysis set in our study was even higher than assumed. Some possible reasons for this unexpected result were discussed in our article, but no clear reason was found.We also did not anticipate the discrepancy between the results of our study and those of previous studies. Although some possible reasons for this discrepancy were also considered in our article, the definite reason is still unclear.As we discussed in our article, acute exacerbation of idiopathic pulmonary fibrosis could have a heterogeneous pathology, meaning there would be factors that remain to be elucidated. Consequently, it may be important to examine the prognostic factors of acute exacerbation to select a more homogeneous population and/or to have a more balanced allocation of cases in future studies.