Implementation and clinical benefit of DPYD genotyping in a Danish cancer population

BACKGROUND

In 2020, the European Medicines Agency recommended testing patients for dihydropyrimidine dehydrogenase (DPD) deficiency before systemic treatment with fluoropyrimidines (FP). DPD activity testing identifies patients at elevated risk of severe FP-related toxicity (FP-TOX). The two most used methods for DPD testing are DPYD genotyping and DPD phenotyping (plasma uracil concentration). The primary objective of this study was to compare the overall frequency of overall grade ≥3 FP-TOX before and after the implementation of DPYD genotyping.

PATIENTS AND METHODS

Two hundred thirty Danish, primarily gastrointestinal cancer patients, were DPYD-genotyped before their first dose of FP, and blood was sampled for post hoc assessment of P-uracil. The initial dose was reduced for variant carriers. Grade ≥3 FP-TOX was registered after the first three treatment cycles of FP. The frequency of toxicity was compared to a historical cohort of 492 patients with post hoc determined DPYD genotype from a biobank.

RESULTS

The frequency of overall grade ≥3 FP-TOX was 27% in the DPYD genotype-guided group compared to 24% in the historical cohort. In DPYD variant carriers, DPYD genotyping reduced the frequency of FP-related hospitalization from 19% to 0%. In the control group, 4.8% of DPYD variant carriers died due to FP-TOX compared to 0% in the group receiving DPYD genotype-guided dosing of FP. In the intervention group, wild-type patients with uracil ≥16 ng/ml had a higher frequency of FP-TOX than wild-type patients with uracil <16 ng/ml (55% versus 28%).

CONCLUSIONS

We found no population-level benefit of DPYD genotyping when comparing the risk of grade ≥3 FP-TOX before and after clinical implementation. We observed no deaths or FP-related hospitalizations in patients whose FP treatment was guided by a variant DPYD genotype. The use of DPD phenotyping may add valuable information in DPYD wild-type patients.

DPYD genotyping and dihydropyrimidine dehydrogenase (DPD) phenotyping in clinical oncology. A clinically focused minireview

BACKGROUND

In clinical oncology, systemic 5-fluorouracil (5-FU) and its oral pro-drugs are used to treat a broad group of solid tumours. Patients with dihydropyrimidine dehydrogenase (DPD) enzyme deficiency are at elevated risk of toxicity if treated with standard doses of 5-FU. DPYD genotyping and measurements of plasma uracil concentration (DPD phenotyping) can be applied as tests for DPD deficiency. In April 2020, the European Medicines Agency recommended pre-treatment DPD testing to reduce the risk of 5-FU-related toxicity.

OBJECTIVES

The objective of this study is to present the current evidence for DPD testing in routine oncological practice.

METHODS

Two systematic literature searches were performed following the PRISMA guidelines. We identified studies examining the possible benefit of DPYD genotyping or DPD phenotyping on the toxicity risk.

FINDINGS

Nine and 12 studies met the criteria for using DPYD genotyping and DPD phenotyping, respectively.

CONCLUSIONS

The evidence supporting either DPYD genotyping or DPD phenotyping as pre-treatment tests to reduce 5-FU toxicity is poor. Further evidence is still needed to fully understand and guide clinicians to dose by DPD activity.

No significant influence of OCT1 genotypes on the pharmacokinetics of morphine in adult surgical patients

We investigated the impact of genetic variants in OCT1 (SLC22A1) on morphine, morphine‐3‐glucuronide (M3G) and morphine‐6‐glucuronide (M6G) pharmacokinetics in adult patients scheduled for major surgery. Blood samples were taken before and 5, 10, 15, 30, 45, 60 and 90 min after a bolus of morphine (0.15 mg/kg). Patients were genotyped for the genetic variants (rs12208357, rs34059508, rs72552763 and rs34130495) in OCT1.

Eighty‐six patients completed the trial. The mean difference (95% confidence interval) for dose adjusted morphine, M3G and M6G AUC was 0.9 (−0.7–2.4), −5.9 (−11.8 to −0.03) and −1.1 (−2.5–0.4) h/L*10⁻⁶, respectively, in patients with two reduced function alleles compared to patients with no reduced function alleles in OCT1. Accordingly, the (AUC_M3G/Dose)/(AUC_{morphine/Dose}) and (AUC_M6G/Dose)/(AUC_{morphine/Dose}) ratio was reduced, −1.8 (−3.2 to −0.4) and −0.4 (−0.7 to −0.03), respectively, when comparing the same groups. OCT1 variants had no influence on the experience of pain, adverse events or the number of PCA doses used. In conclusion, genetic variants in OCT1 had a small and clinically unimportant impact on the exposure of morphine after intravenous administration. Our results do not support pre‐emptive genotyping for OCT1 prior to morphine administration in patients scheduled for major surgery.

Four phase 1 trials to evaluate the safety and pharmacokinetic profile of single and repeated dosing of SCO-101 in adult male and female volunteers

SCO‐101 (Endovion) was discontinued 20 years ago as a new drug under development against sickle cell anaemia. Data from the phase 1 studies remained unpublished. New data indicate that SCO‐101 might be efficacious as add‐on therapy in cancer. Thus, we report the results from the four phase 1 trials performed between 2001 and 2002. Adult volunteers received SCO‐101 or placebo in four independent trials. Adverse events were recorded, and SCO‐101 was determined for pharmacokinetic analysis. Ninety‐two volunteers completed the trials. The most remarkable adverse effect was a transient and dose‐dependent increase in unconjugated bilirubin. Plasma SCO‐101 elimination was approximately log linear, with apparent oral clearances of between 315 and 2103 mL/h for single doses, and between 121 and 2433 mL/h at steady state following oral administration. There was a marked decrease in clearance with increasing dose, and for repeated dose versus single dose. T_max was greater, and C_max and AUC_∞ were lower in the fed state compared to the fasted state. Exposure was equivalent in males and females and for African Americans and Caucasians. In conclusion, SCO‐101 appears to be a safe drug with a predictable PK profile. Its efficacy as add‐on to standard anticancer drugs has yet to be defined.

Drug-drug cross contamination in the Swisslog fully automated medication handling system

OBJECTIVE

The risk of drug-drug cross contamination in drug dispensing robots in hospital pharmacies causes cumbersome restraints to be put on the production of the robot for example by scheduling high-risk drugs to be dispensed at the end of the day. However, we were unable to find published data on the matter, and therefore performed a worst-case scenario study to assess the magnitude of the problem.

METHODS

We measured dexamethasone residue left on the suction cup after the production of 100 and 400 dexamethasone tablets, and after 20 paracetamol tablets used as a negative control.

RESULTS

We found that 32.9 µg and 49.5 µg of dexamethasone had been transferred to the suction cup in the two experiments. This is approximately 1 per mille of the dexamethasone content in a 40 mg tablet.

CONCLUSION

We conclude that uncoated dexamethasone does shed measurable residue in the robot. It remains unknown to what extent this residue contaminates the subsequent production.

A phase I study of the PARP inhibitor niraparib in combination with bevacizumab in platinum-sensitive epithelial ovarian cancer: NSGO AVANOVA1/ENGOT-OV24

BACKGROUND

Combining poly(ADP-ribose) polymerase (PARP) inhibitors with antiangiogenic agents appeared to enhance activity vs PARP inhibitors alone in a randomized phase II trial.

MATERIALS AND METHODS

In AVANOVA (NCT02354131) part 1, patients with measurable/evaluable high-grade serous/endometrioid platinum-sensitive ovarian cancer received bevacizumab 15 mg/kg every 21 days with escalating doses of niraparib capsules (100, 200, or 300 mg daily) in a 3 + 3 dose-escalation design. Primary objectives were to evaluate safety and tolerability and to determine the recommended phase II dose (RP2D).

RESULTS

Three of 12 enrolled patients had germline BRCA2 mutations. In cycle 1, nine patients experienced grade 3 toxicities: five with hypertension, three with anemia, and one with thrombocytopenia. There was one dose-limiting toxicity (grade 4 thrombocytopenia with niraparib 300 mg), thus the RP2D was bevacizumab 15 mg/kg with niraparib 300 mg. The response rate was 50%; disease was stabilized in a further 42%. Median progression-free survival was 11.6 (95% confidence interval 8.4-20.1) months. Niraparib pharmacokinetics were consistent with historical single-agent data. Overlapping exposure was observed across the dose ranges tested on days 1 and 21.

CONCLUSIONS

There was one dose-limiting toxicity; other adverse events were typical PARP inhibitor and antiangiogenic class effects. Niraparib-bevacizumab showed promising activity; Part 2 (vs bevacizumab) was recently reported and phase III comparison with standard-of-care therapy is planned.

Progression-free survival in oncology: Caveat emptor!

Overall survival (OS) is the undisputed gold standard efficacy end-point in cancer drug trials. It is with growing concern that we observe how progression-free survival (PFS) gains ground as surrogate end-point in its place. PFS has appeal because it is resource-efficient, but it has severe shortcomings. Our concern is that uncritical use of PFS will harm the evidence-based evaluation of cancer drugs when considering them for standard use in publicly financed health care systems. PFS is only valid as a surrogate end-point for OS if it correlates strongly with OS and if the cancer drug being investigated has the same effect on PFS and OS such that effects on one predict effects on the other. The latter might be less obvious than the former but is no less critical. Research indicates that in a majority of cases, correlation between surrogate end-points and OS is of medium strength or lower. PFS is therefore unreliable as a surrogate for OS. We do not find it justified to use PFS as surrogate for OS without first having assessed its validity. Stakeholders who take part in evaluating cancer drugs considered for standard use in a health care system must be particularly vigilant about this issue to minimize the risk of introducing cancer drugs that have an unacceptable cost-risk-benefit profile.

The Pharmacogenetics of Tacrolimus in Corticosteroid-Sparse Pediatric and Adult Kidney Transplant Recipients

Introduction

Tacrolimus is a calcineurin inhibitor used as an immunosuppressant drug in solid organ transplantation, and is mainly metabolized by cytochrome P450 (CYP) 3A4 and CYP3A5. Studies have shown an association between the CYP3A5 genotype and tacrolimus dose-adjusted trough concentrations. Variants in the genes PPARA, POR and CYP3A4 have recently been shown to influence tacrolimus metabolism. Furthermore, pharmacokinetic interaction between corticosteroid treatment and tacrolimus has been shown. In the present study, we investigated a potential association between CYP3A5*3, PPARA c.209-1003G>A, POR*28 and CYP3A4*22 and dose-adjusted tacrolimus trough concentrations in a primarily corticosteroid-free (>85%) population of Danish pediatric and adult kidney transplant recipients.

Methods

Seventy-two patients receiving treatment with oral tacrolimus were genotyped using real-time polymerase chain reaction and Primer-Probe Detection. Tacrolimus trough concentrations, corresponding doses and covariates were retrospectively collected from the patients’ medical charts.

Results

It was confirmed that CYP3A5*1 wild-type carriers had lower median dose-adjusted tacrolimus trough concentrations compared with noncarriers. Adults had 56 and 77% lower trough concentrations at 6 weeks (p = 0.0003) and 1 year, respectively (p < 0.0017), and, similarly, children had 65 and 39% lower median concentrations, with p values of 0.006 and 0.011, respectively. No association was found for PPARA c.209-1003G>A, POR*28, or CYP3A4*22. An association between the PPARA c.209-1003G>A genotype and an increased number of infections with cytomegalovirus (CMV) within the first year was identified (p < 0.05). Only 29% of trough concentrations measured between 2 and 12 weeks post-transplantation were on target.

Conclusion

This study shows that the known association of the CYP3A5 genotype with tacrolimus dose-adjusted trough concentrations has the same impact in a corticosteroid-sparse population. The association between PPARA variance and infections with CMV will need further investigation.

Electronic supplementary material

The online version of this article (doi:10.1007/s40268-017-0177-9) contains supplementary material, which is available to authorized users.

[Lactic acidosis in a 24-year-old woman with status asthmaticus]

A 24-year-old woman with asthma presented with symptoms of upper airway infection and tachypnoea and wheezes. She had a history of admissions to intensive care units (ICU) due to respiratory insufficiency. The initial lactate concentration was 2.1 mmol/l. The treatment consisted of inhaled and intravenous β ² agonists. Hereafter, the lactate concentration rose to 9.8 mmol/l, and the patient was admitted to the ICU due to severe asthma exacerbation. The elevation of lactate concentration cleared after discontinuation of β ² agonist therapy. Although lactic acidosis is a rare side effect to β ² agonist treatment, it is important to recog-nize it when present.

Neurotoxicity and low paclitaxel clearance associated with concomitant clopidogrel therapy in a 60-year-old Caucasian woman with ovarian carcinoma

AIM

The aim of the present case report was to describe a novel pharmacokinetic drug–drug interaction between the antiplatelet agent clopidogrel and the antineoplastic agent paclitaxel.

METHODS

The patient was identified in a previously described cohort of 93 patients with ovarian carcinoma treated with paclitaxel. The effect of clopidogrel acyl-β-D-glucuronide on the metabolism of paclitaxel was assessed in human liver microsomes. The analysis of clopidogrel in plasma and the quantification of paclitaxel and 6-hydroxypaclitaxel in in vitro samples were performed by liquid chromatography tandem mass spectrometry.

RESULTS

The patient was a 60-year-old female treated with an unknown dose of clopidogrel at the time of paclitaxel therapy. Clopidogrel was present in all three of the plasma samples obtained during paclitaxel dosing. Estimated unbound paclitaxel clearance was 238 l h−1, which was only 62% of the cohort geometric mean (385 l h−1; range 176–726). She was hospitalized three times, developed severe neuropathy and paclitaxel treatment was subsequently discontinued. In vitro, 30-min preincubation with 100 μM clopidogrel acyl-β-D-glucuronide inhibited the depletion rate of 0.5 μM paclitaxel by 51% and the formation rate of 6-hydroxypaclitaxel by 77%.

CONCLUSION

This is the first report of a clopidogrel–paclitaxel interaction, suggesting that clinically used doses of clopidogrel can reduce the cytochrome P450 2C8 (CYP2C8)-mediated systemic clearance of paclitaxel, leading to an increased risk of paclitaxel toxicity. Caution should be exercised whenever the simultaneous use of paclitaxel and clopidogrel cannot be avoided.

Population Pharmacokinetics of Methylphenidate in Healthy Adults Emphasizing Novel and Known Effects of Several Carboxylesterase 1 (CES1) Variants

The aim of this study was to identify demographic and genetic factors that significantly affect methylphenidate (MPH) pharmacokinetics (PK), and may help explain interindividual variability and further increase the safety of MPH. d‐MPH plasma concentrations, demographic covariates, and carboxylesterase 1 (CES1) genotypes were gathered from 122 healthy adults and analyzed using nonlinear mixed effects modeling. The structural model that best described the data was a two‐compartment disposition model with absorption transit compartments. Novel effects of rs115629050 and CES1 diplotypes, as well as previously reported effects of rs71647871 and body weight, were included in the final model. Assessment of the independent and combined effect of CES1 covariates identified several specific risk factors that may result in severely increased d‐MPH plasma exposure.

Exploratory study of total and free prednisolone plasma exposure and cushingoid appearance, quality of life and biochemical toxicity in adult male kidney transplant recipients

BACKGROUND AND OBJECTIVE

Long-term adverse effects of oral glucocorticoids are frequent and serious. Large between-patient variability in the pharmacokinetics of prednisolone might explain why drug dose is a poor predictor of drug-related toxicity. The aim of the study was to investigate relationships between prednisolone exposure and adverse effects.

METHODS

Male kidney transplant recipients were recruited for serial blood sampling and assessment of glucocorticoid-related adverse effects including dyslipidaemia, abnormal body fat distribution, Cushingoid appearance and impaired quality of life. Total and free prednisolone plasma concentrations were determined using ultra-high-performance liquid chromatography with tandem mass spectrometric detection. Prednisolone exposure was estimated using a limited sampling strategy.

RESULTS

Fifty-six patients were recruited. Patients had a mean age of 54 years and median time post-transplantation of 75 months. Median prednisolone dose was 5 mg. Mean area under the plasma concentration-time curve was 2390 nmol h/L (±580) (SD) and 175 nmol h/L (±78) for total and free prednisolone, respectively. Waist to upper arm circumference ratio was positively associated with free prednisolone plasma exposure with a Spearman correlation coefficient of 0.30 (p value 0.02). The correlation coefficient was 0.24 (p value 0.08) for neck to upper arm circumference ratio and free prednisolone plasma exposure. The clinical Cushingoid phenotype as determined by the Visual Assessment of Cushing's Severity (VACS) score was associated with a reduced score relating to physical functioning on the SF-12, but there was no significant relationship between free prednisolone plasma exposure and quality-of-life scores. Lipid levels and haemoglobin A1c (HbA1c) were not associated with total or free prednisolone exposure.

CONCLUSIONS

There is a positive correlation between free prednisolone plasma exposure and waist to upper arm circumference ratio in adult male kidney transplant recipients on low maintenance prednisolone doses. There is no significant association between total or free prednisolone plasma exposure and plasma glucose and lipid levels in the low prednisolone dose range.

Role of cytochrome P450 2C8*3 (CYP2C8*3) in paclitaxel metabolism and paclitaxel-induced neurotoxicity

AIM

The CYP2C8*3 allele has been suggested as a risk factor for paclitaxel-induced neuropathy but the data hitherto published are conflicting.

MATERIALS & METHODS

In total 435 patients were investigated with respect to maximum neuropathy grade and accumulated paclitaxel dose. The enzymatic properties of CYP2C8.3 variant were analyzed using heterologous mammalian HEK293 cell expression system.

RESULTS

No significant association between CYP2C8*3 allele and neuropathy was found, although a trend was observed. The paclitaxel and amodiaquine metabolism by CYP2C8.3 were found similar to CYP2C8.1, whereas CYP2C8.3 was more efficient in the metabolism of rosiglitazone.

CONCLUSION

These results indicate a difference in substrate specificity between CYP2C8.1 and CYP2C8.3; however, the CYP2C8*3 allele has no major impact on paclitaxel metabolism in vitro or of paclitaxel-induced neuropathy in vivo. Original submitted on 6 February 2015; revision submitted on 9 April 2015.

Improved prediction of tacrolimus concentrations early after kidney transplantation using theory-based pharmacokinetic modelling

Aims

The aim was to develop a theory-based population pharmacokinetic model of tacrolimus in adult kidney transplant recipients and to externally evaluate this model and two previous empirical models.

Methods

Data were obtained from 242 patients with 3100 tacrolimus whole blood concentrations. External evaluation was performed by examining model predictive performance using Bayesian forecasting.

Results

Pharmacokinetic disposition parameters were estimated based on tacrolimus plasma concentrations, predicted from whole blood concentrations, haematocrit and literature values for tacrolimus binding to red blood cells. Disposition parameters were allometrically scaled to fat free mass. Tacrolimus whole blood clearance/bioavailability standardized to haematocrit of 45% and fat free mass of 60 kg was estimated to be 16.1 l h⁻¹ [95% CI 12.6, 18.0 l h⁻¹]. Tacrolimus clearance was 30% higher (95% CI 13, 46%) and bioavailability 18% lower (95% CI 2, 29%) in CYP3A5 expressers compared with non-expressers. An E_max model described decreasing tacrolimus bioavailability with increasing prednisolone dose. The theory-based model was superior to the empirical models during external evaluation displaying a median prediction error of −1.2% (95% CI −3.0, 0.1%). Based on simulation, Bayesian forecasting led to 65% (95% CI 62, 68%) of patients achieving a tacrolimus average steady-state concentration within a suggested acceptable range.

Conclusion

A theory-based population pharmacokinetic model was superior to two empirical models for prediction of tacrolimus concentrations and seemed suitable for Bayesian prediction of tacrolimus doses early after kidney transplantation.

Docetaxel-induced neuropathy: a pharmacogenetic case-control study of 150 women with early-stage breast cancer

BACKGROUND

Docetaxel is a highly effective treatment of a wide range of malignancies but is often associated with peripheral neuropathy. The genetic variability of genes involved in the transportation or metabolism of docetaxel may be responsible for the variation in docetaxel-induced peripheral neuropathy (DIPN). The main purpose of this study was to investigate the impact of genetic variants in GSTP1 and ABCB1 on DIPN.

MATERIAL AND METHODS

DNA was extracted from whole blood from 150 patients with early-stage breast cancer who had received adjuvant docetaxel from February 2011 to May 2012. Two polymorphisms in GSTP1 and three in ABCB1 were selected for the primary analysis, and a host of other candidate genes was explored and compared between 75 patients with clinician-reported DIPN grade ≥ 2 and 75 patients without DIPN.

RESULTS

Patients with the genetic variants GSTP1 rs1138272 C/T or T/T (114Ala/114Val or 114Val/114Val) genotype had an adjusted odds ratio of 3.82; 95% confidence interval 1.34-11.09 of developing DIPN. This result was confirmed in both analysis of cumulated docetaxel dose and haplotype analysis. None of the explorative genes investigated were significantly correlated with DIPN. Patients with a BMI ≥ 30 were five-fold more likely to have DIPN than patients with BMI < 25.

CONCLUSION

We found that GSTP1 Ala114Val polymorphism is associated with occurrence of DIPN. This supports the theory that oxidative stress is involved in DIPN pathophysiology. If confirmed, this may be helpful in the risk assessment of DIPN and perhaps help to achieve better management of neurotoxicity.

Comparison of the influence of cyclosporine and tacrolimus on the pharmacokinetics of prednisolone in adult male kidney transplant recipients

BACKGROUND AND OBJECTIVE

Cyclosporine has been observed to precipitate cushingoid features in kidney transplant recipients already on prednisolone. Some pharmacokinetic studies have demonstrated increased prednisolone exposure in patients on cyclosporine therapy compared with azathioprine, whereas other studies have found no difference. The objective of this study was to determine whether cyclosporine impacts on prednisolone exposure as compared with tacrolimus.

METHODS

Adult male kidney transplant recipients treated with prednisolone and either cyclosporine or tacrolimus were recruited for pharmacokinetic blood sampling at the outpatient clinic at the Princess Alexandra Hospital, Brisbane, Australia. Prednisolone plasma concentrations were determined using ultra-high-performance liquid chromatography. Dose-adjusted area under the plasma concentration-time curve (AUC) of free and total prednisolone was estimated using a previously developed limited sampling strategy and non-compartmental analysis.

RESULTS

A total of 55 patients were eligible for analysis; 38 % received cyclosporine and 62 % received tacrolimus co-therapy. No significant difference in mean dose-adjusted total prednisolone AUC from 0 to 6 h post-dose or mean dose-adjusted free prednisolone AUC from 0 to 12 h was observed between the cyclosporine and tacrolimus groups (449 versus 428 nmol·h/L/mg, p = 0.43, and 32 versus 30 nmol·h/L/mg, p = 0.51, respectively).

CONCLUSION

Cyclosporine does not change the dose-adjusted exposure of prednisolone compared with tacrolimus. Adult kidney transplant recipients can therefore continue on their usual prednisolone dose when changing therapy between cyclosporine and tacrolimus.

The predictive value of KRAS, NRAS, BRAF, PIK3CA and PTEN for anti-EGFR treatment in metastatic colorectal cancer: A systematic review and meta-analysis

BACKGROUND

In metastatic colorectal cancer, mutation testing for KRAS exon 2 is widely implemented to select patients with wild-type tumors for treatment with the monocloncal anti-EGFR antibodies cetuximab and panitumumab. The added predictive value of additional biomarkers in the RAS-RAF-MAPK and PI3K-AKT-mTOR pathways in colorectal cancer is uncertain, which led us to systematically review the impact of alterations in KRAS (outside of exon 2), NRAS, BRAF, PIK3CA and PTEN in relation to the clinical benefit from anti-EGFR treatment.

METHODS

In total, 22 studies that include 2395 patients formed the basis for a meta-analysis on alterations in KRAS exons 3 and 4, NRAS, BRAF, and PIK3CA and PTEN and outcome of anti-EGFR treatment. Odds ratios for objective response rate (ORR) and hazard ratios (HR) for progression-free survival (PFS) and overall survival (OS) were calculated.

RESULTS

Mutations in KRAS exons 3 and 4, BRAF, PIK3CA and non-functional PTEN (mutations or loss of protein expression) significantly predicted poor ORR (OR = 0.26, OR = 0.29, OR = 0.39, and OR = 0.41, respectively). Significantly shorter PFS applied to mutations in KRAS exons 3 and 4 (HR = 2.19), NRAS (HR = 2.30) and BRAF (HR = 2.95) and non-functional PTEN (HR = 1.88). Significantly shorter OS applied to mutations in KRAS exons 3 and 4 (HR = 1.78), NRAS (HR = 1.85), BRAF (HR = 2.52), PIK3CA (HR = 1.43) and alterations in PTEN (HR = 2.09).

CONCLUSIONS

Meta-analysis suggests that mutations in KRAS exons 3 and 4, NRAS, BRAF and PIK3CA and non-functional PTEN predict resistance to anti-EGFR therapies and demonstrates that biomarker analysis beyond KRAS exon 2 should be implemented for prediction of clinical benefit from anti-EGFR antibodies in metastatic colorectal cancer.

The predictive value of KRAS, NRAS, BRAF, PIK3CA and PTEN for anti-EGFR treatment in metastatic colorectal cancer: A systematic review and meta-analysis

BACKGROUND

In metastatic colorectal cancer, mutation testing for KRAS exon 2 is widely implemented to select patients with wild-type tumors for treatment with the monocloncal anti-EGFR antibodies cetuximab and panitumumab. The added predictive value of additional biomarkers in the RAS-RAF-MAPK and PI3K-AKT-mTOR pathways in colorectal cancer is uncertain, which led us to systematically review the impact of alterations in KRAS (outside of exon 2), NRAS, BRAF, PIK3CA and PTEN in relation to the clinical benefit from anti-EGFR treatment.

METHODS

In total, 22 studies that include 2395 patients formed the basis for a meta-analysis on alterations in KRAS exons 3 and 4, NRAS, BRAF, and PIK3CA and PTEN and outcome of anti-EGFR treatment. Odds ratios for objective response rate (ORR) and hazard ratios (HR) for progression-free survival (PFS) and overall survival (OS) were calculated.

RESULTS

Mutations in KRAS exons 3 and 4, BRAF, PIK3CA and non-functional PTEN (mutations or loss of protein expression) significantly predicted poor ORR (OR = 0.26, OR = 0.29, OR = 0.39, and OR = 0.41, respectively). Significantly shorter PFS applied to mutations in KRAS exons 3 and 4 (HR = 2.19), NRAS (HR = 2.30) and BRAF (HR = 2.95) and non-functional PTEN (HR = 1.88). Significantly shorter OS applied to mutations in KRAS exons 3 and 4 (HR = 1.78), NRAS (HR = 1.85), BRAF (HR = 2.52), PIK3CA (HR = 1.43) and alterations in PTEN (HR = 2.09).

CONCLUSIONS

Meta-analysis suggests that mutations in KRAS exons 3 and 4, NRAS, BRAF and PIK3CA and non-functional PTEN predict resistance to anti-EGFR therapies and demonstrates that biomarker analysis beyond KRAS exon 2 should be implemented for prediction of clinical benefit from anti-EGFR antibodies in metastatic colorectal cancer.

Retrospective study of the impact of pharmacogenetic variants on paclitaxel toxicity and survival in patients with ovarian cancer

PURPOSE

Paclitaxel has a broad spectrum of anti-tumor activity and is useful in the treatment of ovarian, breast, and lung cancer. Paclitaxel is metabolized in the liver by CYP2C8 and CYP3A4 and transported by P-glycoprotein. The dose-limiting toxicities are neuropathy and neutropenia, but the interindividual variability in toxicity and also survival is large. The main purpose of this study was to investigate the impact of genetic variants in CYP2C8 and ABCB1 on toxicity and survival.

METHODS

The 182 patients previously treated for ovarian cancer with carboplatin and paclitaxel in either the AGO-OVAR-9 or the NSGO-OC9804 trial in Denmark or Sweden were eligible for this study. Genotyping was carried out on formalin-fixed tissue. The patients' toxicity profiles and survival data were derived from retrospective data. CYP2C8*3, ABCB1 C1236T, G2677T/A, and C3435T were chosen a priori for primary analysis; a host of other variants were entered into an exploratory analysis.

RESULTS

Clinical data and tissue were available from a total of 119 patients. Twenty-two single nucleotide polymorphisms (SNPs) in 10 genes were determined. Toxicity registration was available from 710 treatment cycles. In the primary analysis, no statistically significant correlation was found between CYP2C8*3, ABCB1 C1236T, G2677T/A, and C3435T and neutropenia, sensoric neuropathy, and overall survival.

CONCLUSION

CYP2C8*3 and the ABCB1 SNPs C1236T, G2677T/A, and C3435T were not statistically significantly correlated to overall survival, sensoric neuropathy, and neutropenia in 119 patients treated for ovarian cancer with paclitaxel/carboplatin.

Linkage disequilibrium between the CYP2C19*17 allele and wildtype CYP2C8 and CYP2C9 alleles: identification of CYP2C haplotypes in healthy Nordic populations

PURPOSE

To determine the distribution of clinically important CYP2C genotypes and allele frequencies in healthy Nordic populations with special focus on linkage disequilibrium.

METHODS

A total of 896 healthy subjects from three Nordic populations (Danish, Faroese, and Norwegian) were genotyped for five frequent and clinically important CYP2C allelic variants: the defective CYP2C8*3, CYP2C9*2, CYP2C9*3, and CYP2C19*2 alleles, and the CYP2C19*17 allele that causes rapid drug metabolism. Linkage disequilibrium was evaluated and CYP2C haplotypes were inferred in the entire population.

RESULTS

Ten CYP2C haplotypes were inferred, the most frequent of which (49%) was the CYP2C wildtype haplotype carrying CYP2C8*1, CYP2C9*1, and CYP2C19*1. The second most frequent haplotype (19%) is composed of CYP2C19*17, CYP2C8*1, and CYP2C9*1. This predicted haplotype accounts for 99.7% of the CYP2C19*17 alleles found in the 896 subjects.

CONCLUSION

CYP2C19*17 is a frequent genetic variant in Nordic populations that exists in strong linkage disequilibrium with wildtype CYP2C8*1 and CYP2C9*1 alleles, which effectively makes it a determinant for a haplotype exhibiting an efficient CYP2C substrate metabolism.

Multiple hepatic abscesses due to Yersinia enterocolitica infection secondary to primary haemochromatosis

A case of hepatic abscesses due to Yersinia enterocolitica in an immunocompetent male is presented. Re-examination after 3 months showed that the patient had primary haemochromatosis. Treatment with repeated phlebotomies was instituted. Two years after the patient was first admitted to hospital. 17.2 g iron had been removed and all haematological and biochemical parameters had returned to normal. Genetic analysis of the patients' two sons showed that one was positive for the chromosome defect found in primary haemochromatosis; further investigation is under progress. A study of the literature showed that prior to this case only 45 cases of hepatic abscess secondary to Yersinia enterocolitica have been registered. Of the 45 reported cases, 64% had underlying haemochromatosis and 29% had diabetes mellitus. The overall mortality was 31%. Mortality before 1987 was 60% (n = 20) and since 1987 it has been 8% (n = 25).

Duplication of CYP2D6 predicts high clearance of desipramine but high clearance does not predict duplication of CYP2D6

OBJECTIVE

Duplication of CYP2D6 causes very rapid metabolism of CYP2D6 substrates such as desipramine. However, we have previously shown that in the Danish population, only about 15% of very rapid metabolisers, defined as subjects with a metabolic ratio of sparteine of 0.15 or less, carried a duplicated allele. The question is whether gene duplication is a relatively rare cause (perhaps predictor) of very rapid metabolism or whether a low metabolic ratio is a poor predictor of this.

METHODS

After measuring metabolic ratios anew, we selected six volunteers with duplication of CYP2D6 and metabolic ratios ranging from 0.07 to 0.17 and six volunteers without duplication with metabolic ratios ranging from 0.08 to 0.21. Each subject took 100 mg of desipramine. Blood and urine were collected for 48 h.

RESULTS

The median total oral clearance of desipramine was 372 l/h and 196 l/h [median difference 108 l/h (95.9% c.i., -304-598 l/h)] and the median partial clearance of desipramine by 2-hydroxylation was 155 l/h and 87 l/h [median difference 47 l/h (95.9% c.i., -124-141 l/h)] for the group with duplication and the group without duplication, respectively.

CONCLUSION

The predictive value of duplication of CYP2D6 is poor; there must be other causes (or predictors) of very rapid metabolism and with much higher frequency than duplication of CYP2D6.