Phenotyping Study of Cyclophosphamide 4-Hydroxylation in Malay Cancer Patients

Abstract

Background Cyclophosphamide (CP) is an anticancer alkylating group (nitrogen mustard) and a prodrug that will be metabolized to form its active metabolite, 4-hydroxycyclophosphamide (4-OHCP). The various enzymes involved in its bioactivation can cause a wide range of CP expression and activity among patients and ultimately affect the metabolism, efficacy and toxicity of this drug. The effectiveness of CP therapy can be determined by 4-OHCP level in dried blood spot (DBS). Aim The purpose of this study was to conduct the phenotyping of CP 4-hydroxylation rate in Malay cancer patients. Methodology Phenotyping study of CP 4-hydroxylation rate to 40 subjects of Malay cancer patients was done based on the value of its bioactivity ratio (4-OHCP to CP levels). Results The result shown the cyclophosphamide 4-hydroxylation rate of 80% (n=32) subjects as ultrarapid metabolizer (UM) and 20% (n=8) as poor metabolizer (PM). Conclusion Phenotyping study of CP 4-hydroxylation in Malay cancer patients can be conducted by quantifying CP bioactivity ratio (4-OHCP to CP level) in dried blood spot. In majority of Malay cancer patients, cyclophosphamide would be bioactivated through 4-hydroxylation in hepar rapidly as indicated by the high value of the bioactivity ratio or the increased CP clearance and 4-OHCP level.

Advanced Microsamples: Current Applications and Considerations for Mass Spectrometry-Based Metabolic Phenotyping Pipelines

“…DBS samples have been evaluated in MS-based metabolic phenotyping and have been used in applications of cancer diagnostics [42], cancer treatments [43], air pollution [44], drug discovery [45], acidemia [46], and pyruvate kinase deficiency [47]. Despite this wide range of applications of DBS samples, there still remain concerns around their volumetric accuracy, This review of microsamples, to our knowledge, is the first of its kind to summarise applications to the metabolic phenotyping literature, wherein we highlight where applications have been successful/advantageous.…”

“…To date, studies have successfully performed DBS haematocrit normalisation through potassium content [54], using near-infrared (NIR) spectroscopy [55], haemoglobin measurement using non-contact diffuse reflectance spectroscopy [56], and using wax barriers on DBSs [57]. Despite the development of these normalisation techniques for DBSs, they are yet to be widely adopted in metabolic phenotyping workflows, with many literature examples not implementing a normalisation step in their protocol descriptions [43,44,46,47,55,[58][59][60]. Only two studies have openly reported hct normalisation of their DBS samples as part of their metabolic phenotyping workflow.…”

“…The reason for this is that analyte partitioning can occur between plasma and blood cells, which significantly influences the concentrations of analytes in plasma or whole blood samples taken from a DBS, although this is most commonly seen in monoclonal antibodies for pharmacokinetic studies [25,63]. Additionally, prominent sources of variation in DBS homogeneity have been attributed to the paper substrate used [49]; inconsistencies in the storage, packaging, and transport of samples [42,43]; and contact of DBSs with other surfaces [6].…”

Advanced Microsamples: Current Applications and Considerations for Mass Spectrometry-Based Metabolic Phenotyping Pipelines

“…DBS samples have been evaluated in MS-based metabolic phenotyping and have been used in applications of cancer [42,43], air-pollution [44], drug discovery [45], acidemia [46], and pyruvate kinase deficiency [47]. Despite this wide range of applications of DBS samples, there still remains concerns around their volumetric accuracy, particulary in metabolic phenotyping where standardisation of sample volume is required.…”

“…To date, studies have successfully performed DBS haematocrit normalisation through potassium content [54], using near infrared (NIR) spectroscopy [55], haemoglobin measurement using non-contact diffuse reflectance spectroscopy [56], and using wax barriers on DBSs [57]. Despite the development of these normalisation techniques for DBSs, they are yet to be widely adopted in metabolic phenotyping workflows, with many literature examples not implementing a normalisation step in their protocol descriptions [43,44,46,47,55,[58][59][60]. Only two studies have openly reported hct normalisation of their DBS samples as part of their metabolic phenotyping workflow.…”