2.5. Specificity and selectivity
Blood samples from subjects not receiving any of the drugs of
the interest were used to test the selectivity and the specificity of
the method. Interferences with endogenous compounds have been
evaluated from plasma samples from patients experiencing severe
hepatic (n = 5) or renal (n = 5) impairment. Drug interferences were
investigated in plasma from 10 cancer patients and 10 hospitalized
patients.
2.6. Method validation
The method was validated according to the Food and Drug
Administration (FDA) guidelines for bioanalytical method validation
[8]. Linearity of the method was determined by replicate
analysis of 6 complete standard curves on 6 separate days. The
three levels of IQC were assayed thrice with each standard curve. A
linear regression was used to plot the peak area ratio (y) of analyte
to IS versus analyte concentration. Homoscedasticity of the
model was assessed by the Levene test. Intra- and inter-day precision
(coefficient of variation (CV%)) and accuracy expressed as
bias were evaluated at the three levels of IQC. Six replicates of each
level were assayed in one run for the intra-day experiment. Three
replicates of each level were assayed within six different days for
the inter-day experiment. According to FDA guidelines, the accuracy
and precision for all tested concentrations should be within
±15% except for the lower limit of quantification (LLOQ), in which
case these parameters should not exceed 20%. Average recovery of
vemurafenib and erlotinib was determined by comparing the peak
area of the extracts obtained from IQC samples (6 replicates for each
level) with those obtained by direct injection of the same amount
of drug. Freeze–thaw, short-term, autosampler and long-term stabilities
of vemurafenib and erlotinib were determined according to
the FDA guidelines [8].
2.7. Application
Steady state plasma trough concentration (Cminss) of vemurafenib
was assayed in 22 patients (57 samples) who had melanoma
harboring BRAFV600Emutation. Patients received either 480 mg or
960 mg of vemurafenib on a twice daily schedule. Erlotinib Cminss
was assayed in 30 patients (48 samples) with relapsed non-smallcell
lung cancer (NSCLC) harboring EGFR activating mutations.
Patients received 150 mg or 300 mg of erlotinib once daily. The
results of erlotinib plasma concentrations were compared with
those obtained from a previous method developed in our laboratory
[9]. Blood samples were collected into 5-mL lithium heparinized
Vacutainer tubes. After centrifugation at 3000 rpm for 5 min at 4 ◦C,
plasma was transferred to propylene tubes and stored at
−20 ◦C
until analysis. This study was approved by the local Review Board
for Oncology.
2.8. Statistical analysis
The nonparametric regression proposed by Passing and Bablock
[10] was used to estimate the relationship between the two
analytical techniques used to assay erlotinib concentration. The
scatter of the method comparison data was visualized according
to the recommendations of Bland and Altman [11]. The
individual relative difference was calculated as follows: (new
method
−
reference method)/reference method. Statistical analysis
was performed with Medcalc software, version 7.3.0.1 (Medcalc,
Mariakerke, Belgium). P < 0.05 was considered statistically
significant.
2.5. Specificity and selectivityBlood samples from subjects not receiving any of the drugs ofthe interest were used to test the selectivity and the specificity ofthe method. Interferences with endogenous compounds have beenevaluated from plasma samples from patients experiencing severehepatic (n = 5) or renal (n = 5) impairment. Drug interferences wereinvestigated in plasma from 10 cancer patients and 10 hospitalizedpatients.2.6. Method validationThe method was validated according to the Food and DrugAdministration (FDA) guidelines for bioanalytical method validation[8]. Linearity of the method was determined by replicateanalysis of 6 complete standard curves on 6 separate days. Thethree levels of IQC were assayed thrice with each standard curve. Alinear regression was used to plot the peak area ratio (y) of analyteto IS versus analyte concentration. Homoscedasticity of themodel was assessed by the Levene test. Intra- and inter-day precision(coefficient of variation (CV%)) and accuracy expressed asbias were evaluated at the three levels of IQC. Six replicates of eachlevel were assayed in one run for the intra-day experiment. Threereplicates of each level were assayed within six different days forthe inter-day experiment. According to FDA guidelines, the accuracyand precision for all tested concentrations should be within±15% except for the lower limit of quantification (LLOQ), in whichcase these parameters should not exceed 20%. Average recovery ofvemurafenib and erlotinib was determined by comparing the peakarea of the extracts obtained from IQC samples (6 replicates for eachlevel) with those obtained by direct injection of the same amountof drug. Freeze–thaw, short-term, autosampler and long-term stabilitiesof vemurafenib and erlotinib were determined according tothe FDA guidelines [8].2.7. ApplicationSteady state plasma trough concentration (Cminss) of vemurafenibwas assayed in 22 patients (57 samples) who had melanomaharboring BRAFV600Emutation. Patients received either 480 mg or960 mg of vemurafenib on a twice daily schedule. Erlotinib Cminsswas assayed in 30 patients (48 samples) with relapsed non-smallcelllung cancer (NSCLC) harboring EGFR activating mutations.Patients received 150 mg or 300 mg of erlotinib once daily. Theresults of erlotinib plasma concentrations were compared withthose obtained from a previous method developed in our laboratory[9]. Blood samples were collected into 5-mL lithium heparinizedVacutainer tubes. After centrifugation at 3000 rpm for 5 min at 4 ◦C,plasma was transferred to propylene tubes and stored at−20 ◦Cuntil analysis. This study was approved by the local Review Boardfor Oncology.2.8. Statistical analysisThe nonparametric regression proposed by Passing and Bablock[10] was used to estimate the relationship between the twoanalytical techniques used to assay erlotinib concentration. Thescatter of the method comparison data was visualized accordingto the recommendations of Bland and Altman [11]. Theindividual relative difference was calculated as follows: (newmethod−reference method)/reference method. Statistical analysiswas performed with Medcalc software, version 7.3.0.1 (Medcalc,Mariakerke, Belgium). P < 0.05 was considered statisticallysignificant.
การแปล กรุณารอสักครู่..
