Efficacy and Safety of Trametinib Monotherapy or in Combination With Dabrafenib in Pediatric BRAF V600-Mutant Low-Grade Glioma
Eric Bouffet, Birgit Geoerger, Christopher Moertel, James A Whitlock, Isabelle Aerts, Darren Hargrave, Lisa Osterloh, Eugene Tan, Jeea Choi, Mark Russo, Elizabeth Fox, Eric Bouffet, Birgit Geoerger, Christopher Moertel, James A Whitlock, Isabelle Aerts, Darren Hargrave, Lisa Osterloh, Eugene Tan, Jeea Choi, Mark Russo, Elizabeth Fox
Abstract
Purpose: BRAF V600 mutations occur in many childhood cancers, including approximately 20% of low-grade gliomas (LGGs). Here, we describe a phase I/II study establishing pediatric dosing and pharmacokinetics of trametinib with or without dabrafenib, as well as efficacy and safety in a disease-specific cohort with BRAF V600-mutant LGG; other cohorts will be reported elsewhere.
Methods: This is a four-part, phase I/II study (ClinicalTrials.gov identifier: NCT02124772) in patients age < 18 years with relapsed/refractory malignancies: trametinib monotherapy dose finding (part A) and disease-specific expansion (part B), and dabrafenib + trametinib dose finding (part C) and disease-specific expansion (part D). The primary objective assessed in all patients in parts A and C was to determine pediatric dosing on the basis of steady-state pharmacokinetics. Disease-specific efficacy and safety (across parts A-D) were secondary objectives.
Results: Overall, 139 patients received trametinib (n = 91) or dabrafenib + trametinib (n = 48). Trametinib dose-limiting toxicities in > 1 patient (part A) included mucosal inflammation (n = 3) and hyponatremia (n = 2). There were no dose-limiting toxicities with combination therapy (part C). The recommended phase II dose of trametinib, with or without dabrafenib, was 0.032 mg/kg once daily for patients age < 6 years and 0.025 mg/kg once daily for patients age ≥ 6 years; dabrafenib dosing in the combination was as previously identified for monotherapy. In 49 patients with BRAF V600-mutant glioma (LGG, n = 47) across all four study parts, independently assessed objective response rates were 15% (95% CI, 1.9 to 45.4) for monotherapy (n = 13) and 25% (95% CI, 12.1 to 42.2) for combination (n = 36). Adverse event-related treatment discontinuations were more common with monotherapy (54% v 22%).
Conclusion: The trial design provided efficient evaluation of pediatric dosing, safety, and efficacy of single-agent and combination targeted therapy. Age-based and weight-based dosing of trametinib with or without dabrafenib achieved target concentrations with manageable safety and demonstrated clinical efficacy and tolerability in BRAF V600-mutant LGG.
Conflict of interest statement
Eric Bouffet
Consulting or Advisory Role: Novartis
Research Funding: Roche (Inst)
Birgit Geoerger
Consulting or Advisory Role: Boehringer Ingelheim, AZD, Novartis
Christopher Moertel
Stock and Other Ownership Interests: OX2 Therapeutics
Patents, Royalties, Other Intellectual Property: Patents related to intellectual property held by OX2 Therapeutics and the University of Minnesota
James A. Whitlock
Consulting or Advisory Role: Jazz Pharmaceuticals
Research Funding: Novartis (Inst), Daiichi Sankyo (Inst), Syndax (Inst)
Isabelle Aerts
Consulting or Advisory Role: AstraZeneca
Travel, Accommodations, Expenses: Jazz Pharmaceuticals
Darren Hargrave
Honoraria: AstraZeneca/MedImmune, Bayer, Alexion Pharmaceuticals
Consulting or Advisory Role: AstraZeneca, Roche/Genentech, Novartis, Bayer, Boehringer Ingelheim
Speakers' Bureau: Alexion Pharmaceuticals
Research Funding: AstraZeneca
Expert Testimony: AstraZeneca
Travel, Accommodations, Expenses: Boehringer Ingelheim, Novartis, Roche/Genentech, Alexion Pharmaceuticals
Other Relationship: Celgene, Novartis, Bristol Myers Squibb, Epizyme, AbbVie, AstraZeneca/MedImmune, Day One Therapeutics
Lisa Osterloh
Employment: Novartis
Eugene Tan
Employment: Novartis
Stock and Other Ownership Interests: Novartis
Jeea Choi
Employment: Novartis
Mark Russo
Employment: Novartis
Stock and Other Ownership Interests: Novartis
No other potential conflicts of interest were reported.
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Source: PubMed