First-in-human study of CH5132799, an oral class I PI3K inhibitor, studying toxicity, pharmacokinetics, and pharmacodynamics, in patients with metastatic cancer

PURPOSE

This phase I dose-escalation study investigated the maximum-tolerated dose (MTD), dose-limiting toxicities (DLT), safety, pharmacokinetics (PK), pharmacodynamics (PD), and preliminary clinical activity of CH5132799.

EXPERIMENTAL DESIGN

Patients with metastatic solid tumors were eligible for the study. CH5132799 was administered orally once daily or twice daily in 28-day cycles.

RESULTS

Thirty-eight patients with solid tumors received CH5132799 at 2 to 96 mg once daily or 48 to 72 mg twice daily. The MTD was 48 mg on the twice-daily schedule but was not reached on the once daily schedule. DLTs were grade 3 elevated liver function tests (LFT), grade 3 fatigue, grade 3 encephalopathy, grade 3 diarrhea, and grade 3 diarrhea with grade 3 stomatitis; all DLTs were reversible. Most drug-related adverse events were grade 1/2. Diarrhea (34%) and nausea (32%) were the most common events. Mean Cmax and AUC0-24 in steady state at MTD were 175 ng/mL and 1,550 ng·h/mL, respectively, consistent with efficacious exposure based on preclinical modeling. Reduction in SUVmax with [(18)F] fluorodeoxyglucose positron emission tomography (FDG-PET) was observed in 5 of 7 patients at MTD. A patient with PIK3CA-mutated clear cell carcinoma of the ovary achieved a partial response by GCIG CA125 criteria and further, a heavily pretreated patient with triple-negative breast cancer had marked improvement in her cutaneous skin lesions lasting six cycles.

CONCLUSION

CH5132799 is well tolerated at the MTD dose of 48 mg twice daily. At this dose, the drug had a favorable PK and PD profile and preliminary evidence of clinical activity.

The Biological Role of PI3K Pathway in Lung Cancer

Lung cancer is the primary cause of cancer-related mortality worldwide and although improvements in treatment have been achieved over the last few years, long-term survival rates for lung cancer patients remain poor. Therefore, there is an imperative need for molecularly targeted agents that will achieve long-term disease control. Numerous downstream molecular pathways, such as EGF/RAS/RAF/MEK/ERK and PI3K/AKT/mTOR are identified as having a key role in the pathogenesis of various forms of human cancer, including lung cancer. PI3K/AKT/mTOR signal pathway is an important intracellular signal transduction pathway with a significant role in cell proliferation, growth, survival, vesicle trafficking, glucose transport, and cytoskeletal organization. Aberrations in many primary and secondary messenger molecules of this pathway, including mutations and amplifications, are accounted for tumor cell proliferation, inhibition of apoptosis, angiogenesis, metastasis and resistance to chemotherapy-radiotherapy. In this review article, we investigate thoroughly the biological role of PI3K pathway in lung cancer and its contribution in the development of future therapeutic strategies.

Phase I pharmacokinetic and pharmacodynamic study of the pan-PI3K/mTORC vascular targeted pro-drug SF1126 in patients with advanced solid tumours and B-cell malignancies

BACKGROUND

SF1126 is a peptidic pro-drug inhibitor of pan-PI3K/mTORC. A first-in-human study evaluated safety, dose limiting toxicities (DLT), maximum tolerated dose (MTD), pharmacokinetics (PK), pharmacodynamics (PD) and efficacy of SF1126, in patients with advanced solid and B-cell malignancies.

PATIENTS AND METHODS

SF1126 was administered IV days 1 and 4, weekly in 28day-cycles. Dose escalation utilised modified Fibonacci 3+3. Samples to monitor PK and PD were obtained.

RESULTS

Forty four patients were treated at 9 dose levels (90-1110 mg/m(2)/day). Most toxicity was grade 1 and 2 with a single DLT at180 mg/m(2) (diarrhoea). Exposure measured by peak concentration (C(max)) and area under the time-concentration curve (AUC(0-)(t)) was dose proportional. Stable disease (SD) was the best response in 19 of 33 (58%) evaluable patients. MTD was not reached but the maximum administered dose (MAD) was 1110 mg/m(2). The protocol was amended to enrol patients with CD20+ B-cell malignancies at 1110 mg/m(2). A CLL patient who progressed on rituximab [R] achieved SD after 2 months on SF1126 alone but in combination with R achieved a 55% decrease in absolute lymphocyte count and a lymph node response. PD studies of CLL cells demonstrated SF1126 reduced p-AKT and increased apoptosis indicating inhibition of activated PI3K signalling.

CONCLUSION

SF1126 is well tolerated with SD as the best response in patients with advanced malignancies.

Treatment of HER2-positive breast cancer: current status and future perspectives

The advent of HER2-directed therapies has significantly improved the outlook for patients with HER2-positive early stage breast cancer. However, a significant proportion of these patients still relapse and die of breast cancer. Trials to define, refine and optimize the use of the two approved HER2-targeted agents (trastuzumab and lapatinib) in patients with HER2-positive early stage breast cancer are ongoing. In addition, promising new approaches are being developed including monoclonal antibodies and small-molecule tyrosine kinase inhibitors targeting HER2 or other HER family members, antibodies linked to cytotoxic moieties or modified to improve their immunological function, immunostimulatory peptides, and targeting the PI3K and IGF-1R pathways. Improved understanding of the HER2 signaling pathway, its relationship with other signaling pathways and mechanisms of resistance has also led to the development of rational combination therapies and to a greater insight into treatment response in patients with HER2-positive breast cancer. Based on promising results with new agents in HER2-positive advanced-stage disease, a series of large trials in the adjuvant and neoadjuvant settings are planned or ongoing. This Review focuses on current treatment for patients with HER2-positive breast cancer and aims to update practicing clinicians on likely future developments in the treatment for this disease according to ongoing clinical trials and translational research.

The selective class I PI3K inhibitor CH5132799 targets human cancers harboring oncogenic PIK3CA mutations

PURPOSE

The phosphatidylinositol 3-kinase (PI3K) pathway plays a central role in cell proliferation and survival in human cancer. PIK3CA mutations, which are found in many cancer patients, activate the PI3K pathway, resulting in cancer development and progression. We previously identified CH5132799 as a novel PI3K inhibitor. Thus, this study aimed to clarify the biochemical and antitumor activity of CH5132799 and elucidate the correlation between CH5132799 response and genetic alterations in the PI3K pathway.

EXPERIMENTAL DESIGN

Kinase inhibitory activity was profiled in cell-free assays. A large panel of human breast, ovarian, prostate, and endometrial cancer cell lines, as well as xenograft models, were used to evaluate the antitumor activity of CH5132799, followed by analysis for genetic alterations. Effects on Akt phosphorylation induced by mTORC1 inhibition were tested with CH5132799 and compared with mTORC1 and PI3K/mTOR inhibitors.

RESULTS

CH5132799 selectively inhibited class I PI3Ks and PI3Kα mutants in in vitro kinase assays. Tumors harboring PIK3CA mutations were significantly sensitive to CH5132799 in vitro and were remarkably regressed by CH5132799 in in vivo mouse xenograft models. In combination with trastuzumab, tumors disappeared in the trastuzumab-insensitive breast cancer model with the PIK3CA mutation. Moreover, CH5132799 did not reverse a negative feedback loop of PI3K/Akt/mTOR signaling and induced regression against tumors regrown after long-term mTORC1 inhibitor treatment.

CONCLUSIONS

CH5132799 is a selective class I PI3K inhibitor with potent antitumor activity against tumors harboring the PIK3CA mutations. Prediction of CH5132799 response on the basis of PIK3CA mutations could enable patient stratification in clinical settings.

Development of phosphoinositide-3 kinase pathway inhibitors for advanced cancer

The phosphoinositide-3 kinase (PI3K) pathway plays a critical role in cancer cell growth and survival. PI3K is activated in human cancers by elevated receptor tyrosine kinase activity, RAS mutation, as well as by mutation, amplification, and deletion of genes encoding components of the pathway. Additionally, PI3K pathway activation plays an important role in acquired resistance to both chemotherapy and targeted agents. The essential role of PI3K in human cancer has led to the development of PI3K pathway inhibitors that have shown promise in preclinical models and have entered phase 1 clinical trials. This article reviews preclinical and clinical data on members of this novel drug class, as well as data justifying the combination of PI3K inhibitors with other anticancer agents.

Envisioning the future of early anticancer drug development

The development of novel molecularly targeted cancer therapeutics remains slow and expensive with many late-stage failures. There is an urgent need to accelerate this process by improving early clinical anticancer drug evaluation through modern and rational trial designs that incorporate predictive, pharmacokinetic, pharmacodynamic, pharmacogenomic and intermediate end-point biomarkers. In this article, we discuss current approaches and propose strategies that will potentially maximize benefit to patients and expedite the regulatory approvals of new anticancer drugs.

Drugging the PI3 kinome: from chemical tools to drugs in the clinic

The phosphatidylinositide 3-kinase (PI3K) pathway is very commonly activated in a wide range of human cancers and is a major driving force in oncogenesis. One of the class I lipid kinase members of the PI3K family, p110alpha, is probably the most commonly mutated kinase in the human genome. Alongside genetic, molecular biological, and biochemical studies, chemical inhibitors have been extremely helpful tools in understanding the role of PI3K enzymes in signal transduction and downstream physiological and pathological processes, and also in validating PI3Ks as therapeutic targets. Although they have been valuable in the past, the early and still frequently employed inhibitors, wortmannin and LY294002, have significant limitations as chemical tools. Here, we discuss the case history of the discovery and properties of an increasingly used chemical probe, the pan-class I PI3K and mammalian target of rapamycin (mTOR) inhibitor PI-103 (a pyridofuropyrimidine), and its very recent evolution into the thienopyrimidine drug GDC-0941, which exhibits excellent oral anticancer activity in preclinical models and is now undergoing phase I clinical trials in cancer patients. We also illustrate the impact of structural biology on the design of PI3K inhibitors and on the interpretation of their effects. The challenges and outlook for drugging the PI3 kinome are discussed in the more general context of the role of structural biology and chemical biology in innovative drug discovery.

From the bench to the bed side: PI3K pathway inhibitors in clinical development

A number of intracellular kinase components of the PI3K/Akt/mTOR pathway have been targeted over the past few years, leading to a new generation of anticancer agents that effectively and specifically disrupt this pathway in tumor cells. Here, progress in the identification and clinical evaluation of compounds designed to modulate the enzymatic activity of PI3K, Akt, mTOR, and Hsp90 is reviewed.