OBJECTIVES : To conduct a systematic review of clinical trials for moderate-to-severe asthma (MSA) in Japan and assess how they incorporated economic relevant outcomes recommended by National Institute of Health (NIH), identifying evidence gaps for future economic evaluations in this field.

METHODS : A systematic search using four databases (Medline, Embase, Cochrane CENTRAL, Ichushi) was conducted to identify randomized controlled trials of MSA in Japan (or global trials including Japan) published between 1980-2017. The outcome measures in these trials were compared with NIH recommendations and also another published systematic review (Makoka 2019). For outcome data not available from clinical trials, a target literature review of other Japanese studies was further conducted to identify evidence gaps for future economic evaluations.

RESULTS : In total, 12 published trials were identified from the systematic literature review. Eight trials were conducted entirely in Japan, while the other four were global trials that included Japan. While pulmonary function outcomes were reported by all these trials, asthma exacerbation and rescue medication use, which are listed as core outcomes in NIH recommendation, were reported much less often, especially in the Japanese-only trials (2 of 8 trials). Nine trials incorporated patient-reported outcomes, while six trials reported study discontinuation data. Other core/supplemental outcomes in NIH recommendation, such as healthcare resource uses and school/work absences, were not reported in these trials.

CONCLUSIONS : Although a target literature review of studies other than clinical trials could help solve the evidence gaps, it subjects to the issues of evidence quality and heterogeneity of data sources. Clinical trials in Japan are expected to consider and incorporate more economic relevant outcomes to expedite the good value assessment of different therapies for MSA in future.