Purpose: TrkB acts as an oncogenic kinase in a subset of human neuroblastomas. Lestaurtinib, a multi-kinase inhibitor with potent activity against Trk kinases, has demonstrated activity in preclinical models of neuroblastoma.
Methods: Patients with refractory high-risk neuroblastoma received lestaurtinib twice daily for 5 days out of seven in 28-day cycles, starting at 70% of the adult recommended Phase 2 dose. Lestaurtinib dose was escalated using a 3 + 3 design. Pharmacokinetics and plasma phospho-TrkB inhibitory activity were evaluated in the first cycle.
Results: Forty-seven subjects were enrolled, and 10 dose levels explored starting at 25 mg/M(2)/dose BID. Forty-six subjects were evaluable for response, and 42 subjects were fully evaluable for determination of dose escalation. Asymptomatic and reversible grade 3-4 transaminase elevation was dose limiting in 4 subjects. Reversible pancreatitis (grade 2) was observed in 3 subjects after prolonged treatment at higher dose levels. Other toxicities were mild and reversible. Pharmacokinetic analyses revealed rapid drug absorption, however inter-patient variability was large. Plasma inhibition of phospho-TrkB activity was observed 1 h post-dosing at 85 mg/M(2) with uniform inhibition at 120 mg/M(2). There were two partial responses and nine subjects had prolonged stable disease at dose levels ≥ 5, (median: 6 cycles). A biologically effective and recommended phase 2 dose of 120 mg/M(2)/dose BID was established.
Conclusions: Lestaurtinib was well tolerated in patients with refractory neuroblastoma, and a dose level sufficient to inhibit TrkB activity was established. Safety and signs of activity at the higher dose levels warrant further evaluation in neuroblastoma.