Preclinical and Preliminary Clinical Activity of NVP-BKM120, an Oral Pan-Class I PI3K Inhibitor, in the Brain

Advances in the Management of Central Nervous System Metastases from Breast Cancer

Central nervous system (CNS) metastases are common in breast cancer (BC) patients and are particularly relevant as new treatments for BC are prolonging survival. Here, we review advances in the treatment of CNS metastases from BC, including radiotherapy, systemic therapies, and the evolving role of immunotherapy. The use of radiotherapy and chemotherapy is the cornerstone of treatment for CNS metastases. However, new targeted therapies have recently been developed, including anti-HER2 agents and antibody-drug conjugates that have presented promising results for the treatment of these patients.

Targeted Therapies for Breast Cancer Brain Metastases

The management of breast cancer, the most common cancer in the female population, has changed dramatically over years with the introduction of newer therapies. An increased incidence of brain metastases in recent years has created a challenge for oncologists because this population continues to have a poorer prognosis compared to metastatic breast cancer without central nervous system involvement. Historically, the exclusion of breast cancer patients with brain metastases from clinical trials has made treatment options even more limited. Nonetheless, more recently, this unmet need has been recognized by basic and clinical researchers and has led to the development of targeted therapies with better blood-brain barrier penetration and intracranial efficacy. Here we review targeted therapies directed at human epidermal growth factor receptor type 2 (HER2), vascular endothelial growth factor (VEGF), mammalian target of rapamycin (mTOR), epidermal growth factor receptor (EGFR), cyclin-dependent kinase 4 and 6 (CDK4/6) and poly(ADP-ribose) polymerase (PARP) for breast cancer patients with brain metastases. These therapies aim to be more efficacious and less toxic to represent a paradigm shift in the management of breast cancer brain metastases.

Imatinib in combination with phosphoinositol kinase inhibitor buparlisib in patients with gastrointestinal stromal tumour who failed prior therapy with imatinib and sunitinib: a Phase 1b, multicentre study

Background

The majority of patients with advanced gastrointestinal stromal tumours (GISTs) develop resistance to imatinib and sunitinib, the standard of care for these patients. This study evaluated the combination of buparlisib, an oral phosphoinositide 3-kinase (PI3K) inhibitor, with imatinib in patients with advanced GIST, who have failed prior therapy with imatinib and sunitinib.

Methods

This Phase 1b, multicentre, open-label study aimed to determine the maximum tolerated dose (MTD) and/or a recommended Phase 2 dose of buparlisib in combination with 400 mg of imatinib through a dose-escalation part and a dose-expansion part, and also evaluated the clinical profile of the combination.

Results

Sixty patients were enrolled, including 25 in the dose-escalation part and 35 in the dose-expansion part. In the combination, MTD of buparlisib was established as 80 mg. No partial or complete responses were observed. The estimated median progression-free survival was 3.5 months in the expansion phase. Overall, 98.3% of patients had treatment-related adverse events (AEs), including 45% with grade 3 or 4 AEs.

Conclusions

Buparlisib in combination with imatinib provided no additional benefit compared with currently available therapies. Due to the lack of objective responses, further development of this combination was not pursued for third-line/fourth-line advanced/metastatic GIST.

Trial registration number

NCT01468688.

Phase II study of buparlisib (BKM120) and trastuzumab in patients with HER2+ locally advanced or metastatic breast cancer resistant to trastuzumab-based therapy

PURPOSE

A Phase Ib study in patients with trastuzumab-resistant, human epidermal growth factor receptor-2- (HER2)-positive advanced breast cancer defined the recommended Phase II dose of buparlisib as 100 mg/day in combination with 2 mg/kg weekly trastuzumab, and reported preliminary signs of clinical activity. Here we present results from the Phase II portion.

METHODS

Patients with trastuzumab-resistant, HER2-positive advanced breast cancer received buparlisib plus trastuzumab. Study endpoints included safety/tolerability and antitumour activity. The study was extended to include a Phase Ib dose-escalation phase, in which patients with progressive brain metastases also received capecitabine.

RESULTS

In the Phase II portion, of 50 patients treated with buparlisib and trastuzumab, the most common (≥ 30%) all-grade adverse events (AEs) were diarrhoea (54%), nausea (48%), decreased appetite, increased alanine aminotransferase (36% each), increased aspartate aminotransferase (34%), fatigue, rash (32% each), cough and hyperglycemia (30% each). One (2%) patient achieved complete response and four (8%) patients had confirmed partial responses [PR; including two patients with phosphatidylinositol 3-kinase (PI3 K) pathway-activated tumours]. Overall response rate (ORR) was 10%: the primary endpoint (ORR ≥ 25%) was therefore not met. In the Phase Ib portion, all patients with measurable brain lesions at baseline showed tumour shrinkage to some degree; due to low enrollment, maximum tolerated dose of buparlisib in combination with trastuzumab and capecitabine was not determined.

CONCLUSION

Buparlisib plus trastuzumab, as a chemotherapy-free regimen, demonstrated an acceptable safety profile but limited efficacy in patients with heavily pretreated, trastuzumab-resistant HER2-positive breast cancer, and in patients with progressive brain metastases also receiving capecitabine.

Phase I dose-escalation study of buparlisib (BKM120), an oral pan-class I PI3K inhibitor, in Japanese patients with advanced solid tumors

Buparlisib (BKM120) is an oral pan-phosphatidylinositol 3-kinase inhibitor, targeting all four isoforms of class I PI3K (α, β, γ and δ). This open-label Phase I dose-escalation study was conducted to determine the maximum tolerated dose of continuous daily buparlisib in Japanese patients with advanced solid tumors. Secondary objectives included safety and tolerability, pharmacokinetics, antitumor activity and pharmacodynamic marker changes. Fifteen patients were treated at 25 mg/day (n = 3), 50 mg/day (n = 3) and 100 mg/day (n = 9) dose levels. One dose-limiting toxicity of Grade 4 abnormal liver function occurred at 100 mg/day. Considering the safety profile and the maximum tolerated dose in the first-in-man study of buparlisib in non-Japanese patients, further dose escalation was stopped and 100 mg/day was declared the recommended dose. The most common treatment-related adverse events were rash, abnormal hepatic function (including increased transaminase levels), increased blood insulin levels and increased eosinophil count. Hyperglycemia was experienced by two patients, one Grade 1 and one Grade 4, and mood alterations were experienced by three patients, two Grade 1 and one Grade 2. Pharmacokinetic results showed that buparlisib was rapidly absorbed in a dose-proportional manner. Best overall response was stable disease for six patients, including one unconfirmed partial response. In these Japanese patients with advanced solid tumors, buparlisib had a manageable safety profile, with similar pharmacokinetics to non-Japanese patients. The recommended dose of 100 mg/day will be used in future studies of buparlisib in Japanese patients.

PI3K pathway inhibitors for the treatment of brain metastases with a focus on HER2+ breast cancer

The incidence of breast cancer brain metastases has increased in recent years, largely due to improved control of systemic disease with human epidermal growth factor receptor 2 (HER2)-targeted agents and the inability of most of these agents to efficiently cross the blood-blood barrier (BBB) and control central nervous system disease. There is, therefore, an urgent unmet need for treatments to prevent and treat HER2+ breast cancer brain metastases (BCBMs). Aberrant activation of the phosphatidylinositol 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) signaling pathway is frequently observed in many cancers, including primary breast tumors and BCBMs. Agents targeting key components of this pathway have demonstrated antitumor activity in diverse cancers, and may represent a new treatment strategy for BCBMs. In preclinical studies, several inhibitors of PI3K and mTOR have demonstrated an ability to penetrate the BBB and down-regulate PI3K signaling, indicating that these agents may be potential therapies for brain metastatic disease. The PI3K inhibitor buparlisib (BKM120) and the mTOR inhibitor everolimus (RAD001) are currently under evaluation in combination with trastuzumab in patients with HER2+ BCBMs.