Comparative effectiveness of larotrectinib and entrectinib for TRK fusion cancer

Larotrectinib and entrectinib are tumor-agnostic tropomyosin receptor kinase (TRK) inhibitors that are indicated for the treatment of advanced or metastatic solid tumor cancers with neurotrophic tyrosine receptor kinase (NTRK) gene fusions. Regulatory approval of both agents was based on data from single-arm phase 1/2 studies, including tumor-agnostic basket trials. In the absence of randomized controlled trials, there remains a paucity of data to demonstrate the comparative effectiveness of larotrectinib and entrectinib vs established standard-of-care treatments in cancers with NTRK gene fusions. Furthermore, no studies have directly compared the 2 agents. This article reviews what is known about the comparative effectiveness of larotrectinib and entrectinib vs standard therapies in TRK fusion cancer and examines the comparative effectiveness of the 2 TRK inhibitors. Historical and intrapatient comparisons suggest that TRK inhibitors improve disease response compared with preexisting treatments across most tumor histologies; indirect and limited comparisons of phase 1/2 data and preliminary simulation modeling suggest a potential advantage for larotrectinib over entrectinib in terms of clinical response and survival. Although limited, these data provide some insight into the position of these treatments in established treatment paradigms for TRK fusion cancer, a setting where real-world evidence will be slow to accrue due to the rare nature of these tumors but may be the only way in the future to answer the outstanding questions regarding these 2 agents. Meanwhile, we need to try to obtain the maximum benefit that can be achieved for our patients using the currently available knowledge.