Introduction: Constitutive activation of the phosphatidylinositol-3-kinase (PI3K) signaling pathway is implicated in many human cancers. Until recently, drugs that specifically inhibit the alpha isoform of PI3K that is activated by alterations in the PIK3CA gene have been missing. BYL719 is the first oral PI3K inhibitor that strongly and selectively inhibits the PI3K alpha isoform of PI3K. Its biological activity correlates with inhibition of various downstream signaling components of the PI3K/Akt pathway and it inhibits the proliferation of breast cancer cell lines harboring PIK3CA mutations. In vivo, BYL719 shows statistically significant dose-dependent anti-tumor efficacy in PIK3CA mutant xenograft models in rodents. Methods: BYL719 entered clinical investigation in 2010 exclusively in patients (pts) with advanced solid malignancies carrying an alteration in the PIK3CA gene. In the dose escalation phase, dose selection is guided by a Bayesian regression model with overdose control. As of 21-Sep-2011, a total of 25 pts with a variety of solid tumors, such as colon and breast cancer, have been enrolled and treated at once daily oral doses ranging from 30mg to 450mg. Results: The safety profile of the compound is characterized by mostly on-target toxicity, such as hyperglycemia (33% of pts), which was found more frequently at higher doses and is largely reversible with BYL719 interruption and treatment with oral anti-diabetics. Other commonly reported toxicities include nausea (38%) and decreased appetite, diarrhea, and vomiting (each 29%). 2 DLTs of hyperglycemia and nausea, both CTCAE grade 3, were observed in 2 pts out of 5 treated at 450mg/d. In humans, BYL719 has a low clearance, a half-life of 8.5 h and its exposure increases dose proportionally between 30mg/d and 450mg/d, displaying a low inter-individual variability in Cmax and AUC. Exposure levels reached at clinical doses above 270 mg/d correspond to exposures causing tumor stasis or regression in preclinical PIK3CA dependent xenograft models. First signs of clinical efficacy of BYL719 include 1 confirmed partial response in a patient with ER+ breast cancer treated at 270mg/d. In addition, preliminary data suggest that significant PET responses (PMR) and/or tumor shrinkage were achieved in 8 out of 17 evaluated pts. Three pts had prolonged stable disease (≥7 months) at doses below 270mg/d and overall 8 patients have been on the study for at least 4 months. Upon determination of the MTD for the once daily dosing regimen, ∼45 pts with PIK3CA altered solid tumors will be enrolled into a safety expansion arm. Also, the PK and MTD for twice daily administration of BYL719 will be investigated. Conclusion: The preliminary clinical data available so far suggest BYL719 to be well tolerated, and showing signs of clinical activity, with manageable side effects and a predictable PK profile. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr CT-01. doi:1538-7445.AM2012-CT-01

Aims5-FU is used as the main backbone of chemotherapy regimens for patients with colorectal and other gastrointestinal cancers. Despite development of new strategies that allowed enhancing clinical effectiveness and tolerability of 5-FU, 10–30% of patients treated with 5-FU-based regimens experience severe treatment-related toxicity. In our study, we evaluated the 5-FU exposure-toxicity relationship and investigated the efficacy of PK-guided dosing in increasing tolerability of 5-FU-based chemotherapy.Results50.7% of patients required dose adjustments after cycle 1. Percentage of patients within 5-FU AUC range was 49.3%, 66.9%, 61.0% at cycle 1, 2 and 3 respectively (p = 0.002 cycle 1 vs cycle 2). At all 3 cycles, lower incidences of grade I/II toxicities were observed for patients below or within range compared with those above range (19.4% vs 41.3%, p < 0.001 respectively).ConclusionsOur analysis confirms that the use of BSA-guided dosing results in highly variable 5-FU exposure and strongly suggests that PK-guided dosing can improve tolerability of 5-FU based chemotherapy in patients with gastrointestinal cancers, thus supporting 5-FU therapeutic drug monitoring.Methods155 patients with gastrointestinal cancers, who were to receive 5-FU-based regimens were included in our study. At cycle 1, the 5-FU dose was calculated using patient’s Body Surface Area (BSA) method. A blood sample was drawn on Day 2 to measure 5-FU concentration. At cycle 2, the 5-FU dose was adjusted using a PK-guided dosing strategy targeting a plasma AUC range of 18–28 mg·h/L, based on cycle 1 concentration. Assessments of toxicity was performed at the beginning of every cycle.

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This study provides useful information to clinicians to better estimate the hematopoietic toxicity of carboplatin and thus choose more rationally carboplatin target AUCs as a function of pretreatment or concomitantly administered chemotherapies. For example, an AUC of 5 mg/mL · min is associated with a risk of grade 3 or 4 thrombocytopenia of 2% in combination with paclitaxel versus 38% with gemcitabine in a non-pretreated patient.

Fluoropyrimidines (FU) are still the most prescribed anticancer drugs for the treatment of solid cancers. However, fluoropyrimidines cause severe toxicities in 10 to 40% of patients and toxic deaths in 0.2 to 0.8% of patients, resulting in a real public health problem. The main origin of FU-related toxicities is a deficiency of dihydropyrimidine dehydrogenase (DPD), the rate-limiting enzyme of 5-FU catabolism. DPD deficiency may be identified through pharmacogenetics testing including phenotyping (direct or indirect measurement of enzyme activity) or genotyping (detection of inactivating polymorphisms on the DPYD gene). Approximately 3 to 15% of patients exhibit a partial deficiency and 0.1 to 0.5% a complete DPD deficiency. Currently, there is no regulatory obligation for DPD deficiency screening in patients scheduled to receive a fluoropyrimidine-based chemotherapy. Based on the levels of evidence from the literature data and considering current French practices, the Group of Clinical Pharmacology in Oncology (GPCO)-UNICANCER and the French Network of Pharmacogenetics (RNPGx) recommend the following: (1) to screen DPD deficiency before initiating any chemotherapy containing 5-FU or capecitabine; (2) to perform DPD phenotyping by measuring plasma uracil (U) concentrations (possibly associated with dihydrouracil/U ratio), and DPYD genotyping (variants *2A, *13, p.D949V, HapB3); (3) to reduce the initial FU dose (first cycle) according to DPD status, if needed, and further, to consider increasing the dose at subsequent cycles according to treatment tolerance. In France, 17 public laboratories currently undertake routine screening of DPD deficiency.

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Purpose: It has recently been shown that it is possible to improve the prediction of carboplatin clearance by adding plasma cystatin C level (cysC), an endogenous marker of glomerular filtration rate, to the other patient characteristics routinely used for carboplatin individual dosing, namely serum creatinine (Scr), actual body weight (ABW), age, and sex. This multicenter pharmacokinetic study was done to evaluate prospectively the benefit of using cysC for carboplatin individual dosing. Experimental Design: The 357 patients included in the study were receiving carboplatin as part of established protocols. A population pharmacokinetic analysis was done using NONMEM program. Seven covariates studied were as follows: Scr, cysC, age, sex, ABW, ideal body weight, and lean body mass. Using an alternative weight descriptor (ideal body weight or lean body mass) did not improve the prediction. This final covariate model was validated by bootstrap analysis. The bias (mean percentage error) and imprecision (mean absolute percentage error) were +1% and 15%, respectively, on the total population, and were of a similar magnitude in each of the three subgroups of patients defined according to their body mass index. Conclusion: For the first time, a unique formula is proposed for carboplatin individual dosing to patients, which is shown to be equally valid for underweight, normal weight, and obese patients. (2) using the measured creatinine clearance (CrCl; requiring 24-hour urine collection). Some years later, Calvert et al. (3) proposed to use the GFR measured by the clearance (CL) of [Cr 51 ]EDTA. Since then, substituting the CrCl calculated with the Cockcroft-Gault equation (4) into the Calvert formula (i.e., carboplatin CL = CrCl + 25) is the most widely used method to calculate the individual dose of carboplatin. Over the past 15 years, there has been an endless debate concerning the best equation to predict carboplatin CL. No single equation has been found to be applicable to all patients without bias except for the original method based on [Cr 51 ]EDTA CL determination (5). The main limitation of the existing equations is that they are all based on serum creatinine level (Scr) as the unique biological covariate (together with demographical and morphologic covariates). Scr is dependent on GFR, but its rate of production depends on muscle mass. Because of this, it has been shown that several of the existing formulae overestimate carboplatin CL in both obese patients and patients with cachexia (6). Recently, Thomas et al. (7) showed by analyzing the pharmacokinetic data of 45 patients from one center that cystatin C plasma level (cysC) was a marker of carboplatin elimination that is at least

The proposed model allows a mechanistic interpretation of G-CSF effects on ANC and raises the question of a systematic beneficial effect of G-CSF treatment. Other studies are needed to confirm these findings and help identifying patients for whom G-CSF is beneficial.