Phase Ib study of Buparlisib plus Trastuzumab in patients with HER2-positive advanced or metastatic breast cancer that has progressed on Trastuzumab-based therapy.
OBJECTIVE
Phosphoinositide 3-kinase (PI3K)/AKT/mTOR pathway activation in patients with HER2-positive (HER2(+)) breast cancer has been implicated in de novo and acquired trastuzumab resistance. The purpose of this study was to determine the clinical activity of the PI3K inhibitor buparlisib (BKM120) in patients with HER2(+) advanced/metastatic breast cancer resistant to trastuzumab-based therapy.


METHODS
In the dose-escalation portion of this phase I/II study, patients with trastuzumab-resistant locally advanced or metastatic HER2(+) breast cancer were treated with daily oral doses of buparlisib and weekly intravenous trastuzumab (2 mg/kg). Dose escalation was guided by a Bayesian logistic regression model with overdose control.


RESULTS
Of 18 enrolled patients, 17 received buparlisib. One dose-limiting toxicity of grade 3 general weakness was reported at the 100-mg/day dose level (the single-agent maximum tolerated dose) and this dose level was declared the recommended phase II dose (RP2D) of buparlisib in combination with trastuzumab. Common (>25%) adverse events included rash (39%), hyperglycemia (33%), and diarrhea (28%). The pharmacokinetic profile of buparlisib was not affected by its combination with trastuzumab. At the RP2D, there were two (17%) partial responses, 7 (58%) patients had stable disease (≥6 weeks), and the disease control rate was 75%. Pharmacodynamic studies showed inhibition of the PI3K/AKT/mTOR and RAS/MEK/ERK pathways.


CONCLUSIONS
In this patient population, the combination of buparlisib and trastuzumab was well tolerated, and preliminary signs of clinical activity were observed. The phase II portion of this study will further explore the safety and efficacy of this combination at the RP2D. Clin Cancer Res; 20(7); 1935-45. ©2014 AACR.
Authors' Affiliations: Medical Oncology Department, Vall d'Hebron University Hospital, Vall d'Hebron Institute of Oncology (VHIO), Barcelona, Spain; Catalan Institute of Oncology, Barcelona, Spain; Sarah Cannon Research Institute, Nashville, Tennessee; Novartis Pharmaceuticals, East Hanover, NJ; Novartis Pharmaceuticals, Florham Park, New Jersy; C.H.U. Sart-Tilman, Liege; Oncologisch Centrum AZ-St. Augustinus Oncology, Antwerp, Belgium; Novartis Pharma AG, Basel, Switzerland; Novartis Oncology, Paris, France; Memorial Sloan-Kettering Cancer Centre, New York, New York; Highlands Oncology Group, Fayetteville, Arkansas; and Novartis Institutes for BioMedical Research, Cambridge, Massachusetts.
Cristina
C
Saura
Johanna
J
Bendell
Guy
G
Jerusalem
Shaun
S
Su
Qinhua
Q
Ru
Stefan
S
De Buck
David
D
Mills
Sophie
S
Ruquet
Ana
A
Bosch
Ander
A
Urruticoechea
Joseph T
JT
Beck
Emmanuelle
E
Di Tomaso
David W
DW
Sternberg
Cristian
C
Massacesi
Samit
S
Hirawat
Luc
L
Dirix
Jose
J
Baselga
D000328:Adult; D000368:Aged; D061067:Antibodies, Monoclonal, Humanized / Q000008:administration & dosage*; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000008:administration & dosage*; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D005260:Female; D006801:Humans; D020714:Maximum Tolerated Dose; D008875:Middle Aged; D000081082:Phosphoinositide-3 Kinase Inhibitors; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000235:genetics; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism; D000068878:Trastuzumab
D061067:Antibodies, Monoclonal, Humanized; D000081082:Phosphoinositide-3 Kinase Inhibitors; D018719:Erb-b2 Receptor Tyrosine Kinases; D058570:TOR Serine-Threonine Kinases; D000068878:Trastuzumab; C546842:MTOR protein, human; C508053:ERBB2 protein, human