Entrectinib demonstrated “very promising” antitumor activity in children and adolescents with recurrent or refractory solid tumors, according to an investigator involved in a phase 1/1b trial.
Twelve of 29 patients enrolled in the trial have responded to entrectinib. All responders had fusions in genes targeted by the drug – NTRK1/2/3 (TRKA/B/C), ROS1, or ALK – or an ALK mutation.
Details of this study are scheduled to be presented at the annual meeting of the American Society of Clinical Oncology.
Giles W. Robinson, MD, of St. Jude Children’s Research Hospital in Memphis, Tenn., discussed the study during a press briefing in advance of the meeting.
“Entrectinib is an oral and potent inhibitor of the TRKA/B/C, ROS1, and ALK proteins, but it also penetrates into the brain to reach tumors in the brain and spine, which can be a hard area to get drugs to,” Dr. Robinson explained.
“Promising clinical activity was initially seen in the adult solid tumor patients with target rearrangements, and it was encouraging to see these patients also had responses when the tumors were located in their brains. And what got us really excited as pediatric oncologists was that a variety of pediatric cancers harbor these fusions and mutations within certain tumors.”
With this in mind, Dr. Robinson and colleagues conducted a phase 1/1b study (NCT02650401) of entrectinib in 29 patients with recurrent or refractory solid tumors, including central nervous system (CNS) tumors.
The patients’ median age was 7 years (range, 0-20 years), and roughly half of them were male (n = 15). Patients were diagnosed with neuroblastoma (n = 16), high-grade glioma (n = 5), inflammatory myofibroblastic tumors (n = 3), infantile fibrosarcoma (n = 2), CNS embryonal tumor (n = 1), melanoma (n = 1), and synovial sarcoma (n = 1).
In the dose-finding portion of the trial, patients received entrectinib at 250 mg/m2 (n = 3), 400 mg/m2 (n = 3), 550 mg/m2 (n = 7), or 750 mg/m2 (n = 3).
In the phase 1b portion, patients received entrectinib at 550 mg/m2 (n = 7) – the recommended dose – or 400 mg/m2 (n = 6) if they were unable to swallow intact capsules.
Dr. Robinson said entrectinib was “quite well tolerated” overall, but he did not present any data on adverse events. He did say dose-limiting toxicities included fatigue, elevated creatinine levels, dysgeusia resulting in loss of taste, weight gain, and, in one patient, pulmonary edema.
“Entrectinib produced striking, rapid, and durable responses in all children with refractory CNS and solid tumors that actually harbored these fusions in NTRK1/2/3, ROS1, or ALK,” Dr. Robinson said. “It also produced a significant response in one ALK-mutated neuroblastoma patient. [N]o responses were seen in tumors lacking aberrations in the target kinases.”
In all, 12 patients responded. The three complete responders had an ALK F1174L mutation, an ALK fusion, and an NTRK fusion, respectively. Five partial responders had NTRK fusions, three had ROS1 fusions, and one had an ALK fusion.
Three responders discontinued treatment. Ten patients were still receiving entrectinib at last follow-up, and 11 patients had died.
Progression-free survival was significantly longer among patients who had fusions than among those who did not (P less than .0001).
“To sum up, entrectinib really is very promising,” Dr. Robinson said. “It has very promising antitumor activity and progression-free survival but [only] in patients with target gene fusions.”
Dr. Robinson said this trial is ongoing, but it is now limited to patients with fusions targeted by entrectinib.
The trial is sponsored by Hoffman-La Roche Ltd. and supported by Alex’s Lemonade Stand Center of Excellence. Dr. Robinson has relationships with Lilly, Genentech/Roche, and Novartis.
SOURCE: Robinson GW et al. ASCO 2019. Abstract 10009.