Three simultaneous safety and efficacy studies of the drug larotrectinib reported an overall response rate of 75 percent for patients ages four months to 76 years with 17 different cancer diagnoses. All patients had tumors with tropomyosin receptor kinase (TRK) fusions, gene mutations that switch on TRK genes, allowing cancer growth. The studies indicate larotrectinib as a potentially powerful new treatment approach for the approximately 5,000 patients with these forms of cancer.
Findings from the multi-center investigation were published in the Feb. 21 online issue of the New England Journal of Medicine (NEJM). Co-principal investigators were David Hong, M.D., professor of Investigational Cancer Therapeutics at The University of Texas MD Anderson Cancer Center, and David Hyman, M.D., chief of Early Drug Development at Memorial Sloan Kettering Cancer Center.
"In this series of studies, larotrectinib had rapid, potent and durable anti-tumor activity in children and adults who had solid tumors with TRK fusions without regard to patient age, tumor tissue and fusion status," said Hong. "Our data not only validated TRK fusions as therapeutic targets, but also showed the potential for larotrectinib as a therapeutic agent for TRK-fusion-positive cancers."
The three protocols included a Phase I study of adults, a Phase I-II study of children, and a Phase II study with adolescents and adults. The investigators followed 55 patients who demonstrated minimal low-grade adverse effects.
Eligible patients had previously been diagnosed with locally advanced or metastatic solid tumors, received standard-of-care therapy and had functioning major organs. The study encompassed 17 unique cancer diagnoses including infantile fibrosarcoma (seven patients); mammary analogue secretory carcinoma of the salivary gland (12 patients); thyroid, colon, lung and gastrointestinal stromal tumors (20 patients); and 16 patients with other cancers.
"TRK fusions defined a unique molecular subgroup of advanced solid tumors in children and adults in whom larotrectinib was highly active," said Hong. "Study results suggest that long-term administration of larotrectinib is feasible for patients with TRK-fusion-positive cancers. However, screening strategies that include assays with the ability to detect TRK fusions will need to be developed to better identify patients who may benefit from this therapy."
Hong added that while clinically meaningful durability of response was observed in study patients, continued follow up could provide further confirmation of the drug's benefit.
Other senior co-authors of the NEJM paper included Alexander Drilon, M.D., Memorial Sloan Kettering Cancer Center, New York, and Theodore Laetsch, M.D., The University of Texas Southwestern Medical Center, Dallas. Funda Meric-Bernstam, M.D., chair of Investigational Cancer Therapeutics at MD Anderson, also participated in the study.
Other study team institutions included Stanford Cancer Center, Palo Alto, Calif.; Children's Hospital of Los Angeles, Keck School of Medicine; and the University of California Los Angeles David Geffen School of Medicine, Los Angeles; Loxo Oncology, South San Francisco, Calif.; Dana-Farber Cancer Institute, and Massachusetts General Hospital, Boston; the Finsen Center, Righospitalet, Copenhagen; the University of Colorado, Aurora; St. Jude Children's Hospital, Memphis, and Vanderbilt University, Nashville, Tenn.; Cincinnati Children's Hospital Medical Center; University Hospitals of Cleveland; Cleveland Clinic's Taussig Cancer Institute; Perelman School of Medicine, Abramson Cancer Center and Fox Chase Cancer Center, Philadelphia; University of Washington-Seattle Cancer Care Alliance; Seattle Children's Hospital' Inova Schar Cancer Institute, Falls Church, Va.; START Madrid, Centro Integral Oncológico Clara Campal, Madrid; Memorial Cancer Institute-Florida International University, Miami; Oregon Health and Science University, Portland; and the West Virginia Cancer Institute, Morgantown, W.Va.
The studies were funded by Loxo Oncology, which developed larotrectinib; the National Institutes of Health (P30 CA008748, P30 CA006927, P30 CA016672, P20 CA046934, and P50 CA058187); the Cancer Prevention and Research Institute of Texas (RP110000584); Alex's Lemonade Stand Foundation Centers of Excellence Award; and the National Center for Advancing Translational Sciences (TR000371 and UL1 TR001881). Hong previously served in an advisory capacity for Loxo Oncology.