Cytidine Deaminase Status Research Articles

Abstract 1150: Pharmacokinetics and pharmacogenetics of liposomal cytarabine in AML patients treated with CPX-351

Abstract CPX-351 is a liposomal form encapsulating cytarabine and daunorubicin for treating Acute Myeloid Leukemia (AML) patients. Cytidine Deaminase (CDA) catabolizes free cytarabine in the liver, but to what extent it could affect as well the pharmacokinetics of liposomal cytarabine is yet to be investigated. Here we have studied the pharmacokinetics (PK) of released, liposomal and total cytarabine using a population-modeling approach in adult AML patients treated with CPX-351. Impact of CDA status (i.e., Poor Metabolizer (PM) vs. Extensive Metabolizer (EM)) on cytarabine exposure levels (AUC, trough levels, Cmax) and PK parameters were analyzed. All patients showed febrile neutropenia and one toxic-death was observed. Overall response rate was 75%. The ratio free:total cytarabine monitored in our patients was higher than expected (i.e., 47%). Inter-individual variability on pharmacokinetics parameters and subsequent exposure levels was >60%. A trend towards severe toxicities was observed in patients with higher exposure of cytarabine. Results showed that liposomal CPX-351 led to sustained exposure with reduced clearance (Cl = 0.16 L/h) and prolonged half-life (T1/2 = 28 h). Of note, liposomes were observed transiently in bone marrow on D15, with cytarabine levels 2.3-time higher than in plasma. Sequencing CDA gene was not contributive and CDA status was primarily evaluated upon phenotyping patients. PM status was found in 77% of the patients with a marked impact on cytarabine PK parameters, i.e., PM patients had higher exposure than EM patients (AUC: 5536 vs. 1784 ng/mL.h), prolonged half-life (T1/2: 33.9 vs. 13.7 h), and reduced clearance (Cl: 0.12 vs. 0.29 L/h). This pilot study suggests that despite being encapsulated in a liposomal vehicle as CPX-351, cytarabine fate in the body is highly dependent upon CDA activity, suggesting that liver metabolism is only partly skipped by the nanoparticle. Here, CDA status proved to have a major impact on cytarabine PK and possibly safety in AML patients treated with CPX-351. Indeed PM patients displayed higher exposure levels with higher risk for severe non-hematological toxicities. This study suggests that CDA status could be used as a covariate to customize CPX-351 dosing in AML patients. Citation Format: Melanie Donnette, Mourad Hamimed, Joseph Ciccolini, Regis Costello, Laure Delassus, Geoffroy Venton, Raphaelle Fanciullino. Pharmacokinetics and pharmacogenetics of liposomal cytarabine in AML patients treated with CPX-351 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1150.

Pharmacokinetics and pharmacogenetics of liposomal cytarabine in AML patients treated with CPX-351

CPX-351 is a liposome encapsulating cytarabine and daunorubicin for treating Acute Myeloid Leukemia (AML) patients. To what extent differences in cytidine deaminase (CDA) activity, the enzyme that catabolizes free cytarabine in the liver, can affect the pharmacokinetics of liposomal cytarabine as well, is unknown.We have studied the pharmacokinetics (PK) of released, liposomal and total cytarabine using a population-modeling approach in 9 adult AML patients treated with liposomal CPX-351. Exposure levels and PK parameters were compared with respect to the patient's CDA status (i.e., Poor Metabolizer (PM) vs. Extensive Metabolizer (EM)).Overall response rate was 75%, and 56% of patients had non-hematological severe toxicities, including one lethal toxicity. All patients had febrile neutropenia. A large (>60%) inter-individual variability was observed on pharmacokinetics parameters and subsequent drug levels. A trend towards severe toxicities was observed in patients with higher exposure of cytarabine. Results showed that liposomal CPX-351 led to sustained exposure with reduced clearance (Cl = 0.16 L/h) and prolonged half-life (T1/2 = 28 h). Liposomal nanoparticles were observed transiently in bone marrow with cytarabine levels 2.3-time higher than in plasma. Seven out of 9 patients were PM with a strong impact on the PK parameters, i.e., PM patients showing higher cytarabine levels as compared with EM patients (AUC: 5536 vs. 1784 ng/mL.h), sustained plasma exposure (T1/2: 33.9 vs. 13.7 h), and reduced clearance (Cl: 0.12 vs. 0.29 L/h).This proof-of-concept study suggests that CDA status has a major impact on cytarabine PK and possibly safety in AML patients even when administered as a liposome.

Simultaneous determination of cytosine arabinoside and its metabolite uracil arabinoside in human plasma by LC-MS/MS: Application to pharmacokinetics-pharmacogenetics pilot study in AML patients

Purine analogs like aracytine (AraC) are a mainstay for treating acute myeloid leukemia (AML). There are marked differences in drug dosing and scheduling depending on the protocols when treating AML patients with AraC. Large inter-patient pharmacokinetics variability has been reported, and genetic polymorphisms affecting cytidine deaminase (CDA), the liver enzyme responsible for the conversion of Ara-C to inactive uracil arabinoside (AraU) could be a culprit for either life-threatening toxicities or poor efficacy related to substantial changes in plasma exposure levels among patients. The quantitative determination of Ara-C in plasma is challenging due the required sensitivity because of the short half-life of this drug (i.e., <10 min) and the metabolic instability in biological matrix upon sampling possibly resulting in erratic values. We developed and validated a liquid chromatography tandem mass spectrometry method (UPLC-MS/MS) for the simultaneous determination of Ara-C and Ara-U metabolite in human plasma. After simple and rapid precipitation, analytes were successfully separated and quantitated over a 1–500 ng/ml range for Ara-C and 250–7500 ng/ml range for AraU. The performance and reliability of this method was tested as part of an investigational study in AML patients treated with low dose cytarabine and confirmed marked differences in drug exposure levels and metabolic ratio, depending on the CDA status of the patients. Overall, this new method meets the requirements of current bioanalytical guidelines and could be used to monitor drug levels in AML patients with respect to their CDA phenotypes.

Abstract 3898: CDA predicts life-threatening toxicities in AML patients treated with cytarabine

Abstract Cytarabine (Ara-C) is the backbone for treating accute myeloid leukemia (AML). As most nucleoside analogs, Ara-C is metabolized in the liver by an exclusive enzymatic step driven by cytidine deaminase (CDA). CDA is a ubiquitous enzyme that proved to be highly polymorphic, with activities in patients ranging from poor metabolizer (PM) to ultra metabolizer (UM). To date, deregulated CDA has been evidenced as a culprit for life-threatening toxicities with gemcitabine. Little evidences have been collected thus far about the possible role erratic CDA could further play with Ara-C. Here, we investigated whether deregulations affecting CDA could be at the origin of unexpectedly severe, and sometimes lethal, toxicities with Ara-C in patients with AML. In this clinical observational study we determined CDA activity levels and searched for CDA genetic polymorphisms in 58 adult patients (25F, 33M, mean age 63 ±15 years) hospitalized for AML and scheduled for induction therapy. All patients were treated following current standard care by Ara-C-containing regimen (i.e., 7+3 protocol) and monitored for toxicity (CTCAEv4 grading) and response. Efficacy was evaluated one-month after starting the induction protocol. Mean CDA activity in the studied population was 3.14 ± 3 U/mg. No relationship was found between CDA phenotype and genotype (i.e., 79A&amp;gt;C polymorphism). A total of 20 patients (43%) displayed severe toxicities (i.e. grade-3 and above) upon administration, including 3 unrecoverable grade-5 toxicities (5%). Relationship between CDA activity and severe toxicity was investigated using ROC analysis. We observed that the incidence of CDA deficiency was much higher in AML patients (40%) than what we previously observed in patients with solid tumors. A cut-off value in CDA ≤ 2 U/mg was associated with increased risk of experiencing severe/lethal toxicities with 74% sensitivity and 65% specificity. Among the 20 patients with severe toxicities, 14 (72 %) were categorized as PM. Importantly, patients who experienced lethal toxicities were all profoundly PM patients. CR was achieved in 35 patients (60%), CRI achieved in 4 patients (7%) whereas 16 patients (27%) failed to respond (PD). No relationship was evidenced between CDA status and response, however regardless of the karyotype we observed that PM patients tended to have longer PFS (278 vs. 517 days) and OS (570 days vs. not reached) as compared with EM patients. Overall this proof-of-concept study strongly suggests that CDA status could be a relevant marker for predicting clinical outcome in patients treated with Ara-C, especially treatment-induced toxicities. A prospective study including full PK and pharmacogenetics support is currently ongoing in our institute to confirm these observations. Should the role CDA plays be confirmed, this marker could be used as a covariate to customize Ara-C dosing in AML patients. Citation Format: Raphaelle Fanciullino, Laure Farnault, Mélanie Donnette, Vadim Ivanov, Geoffroy Venton, Joseph Ciccolini, Yael Berda-Haddad, Catherine Roche, L'Houcine Ouafik, Bruno Lacarelle, Regis Costello. CDA predicts life-threatening toxicities in AML patients treated with cytarabine [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3898.

Population Pharmacokinetics of Gemcitabine and dFdU in Pancreatic Cancer Patients Using an Optimal Design, Sparse Sampling Approach.

Gemcitabine remains a pillar in pancreatic cancer treatment. However, toxicities are frequently observed. Dose adjustment based on therapeutic drug monitoring might help decrease the occurrence of toxicities. In this context, this work aims at describing the pharmacokinetics (PK) of gemcitabine and its metabolite dFdU in pancreatic cancer patients and at identifying the main sources of their PK variability using a population PK approach, despite a sparse sampled-population and heterogeneous administration and sampling protocols. Data from 38 patients were included in the analysis. The 3 optimal sampling times were determined using KineticPro and the population PK analysis was performed on Monolix. Available patient characteristics, including cytidine deaminase (CDA) status, were tested as covariates. Correlation between PK parameters and occurrence of severe hematological toxicities was also investigated. A two-compartment model best fitted the gemcitabine and dFdU PK data (volume of distribution and clearance for gemcitabine: V1 = 45 L and CL1 = 4.03 L/min; for dFdU: V2 = 36 L and CL2 = 0.226 L/min). Renal function was found to influence gemcitabine clearance, and body surface area to impact the volume of distribution of dFdU. However, neither CDA status nor the occurrence of toxicities was correlated to PK parameters. Despite sparse sampling and heterogeneous administration and sampling protocols, population and individual PK parameters of gemcitabine and dFdU were successfully estimated using Monolix population PK software. The estimated parameters were consistent with previously published results. Surprisingly, CDA activity did not influence gemcitabine PK, which was explained by the absence of CDA-deficient patients enrolled in the study. This work suggests that even sparse data are valuable to estimate population and individual PK parameters in patients, which will be usable to individualize the dose for an optimized benefit to risk ratio.

Abstract 5479: PGx of gemcitabine in pancreatic ADK: Where did we go wrong

Abstract There is a rising concern about how to limit toxicities and improve treatment outcome upon gemcitabine (GEM)-based treatment since evidence has been made that cytidine deaminase (CDA) is the major enzyme responsible for its inactivation into dFdU. CDA is subject to a wide inter-individual variability in terms of activity, due to genetic variations, leading to decreased or increased activity. We studied the effect of CDA phenotype and genotype on incidence of early severe hematologic toxicities upon GEM. We also conducted a pharmacokinetic (PK) study of GEM and dFdU. 120 patients with pancreatic ADK were enrolled in a prospective clinical trial FFCD-1004, all receiving GEM in monotherapy (1000mg/m2, 30-min IV infusion). Blood samples were collected prior to treatment to evaluate CDA status by a double approach: a phenotypic and a genotyping tests. PK study was conducted with a LSS: on 1rst course, samples were withdrawn prior administration, at the end of infusion, and 90 and 120 min after the end of infusion. GEM and dFdU levels were measured by UPLC-MSMS on plasma fraction. GEM and dFdU kinetics were analyzed using non-linear mixed effect modeling software Monolix 4.3.2®. 109 patients were analyzable for CDA activity, with a mean age of 66 years. 40 patients displayed early severe toxicities, including 26 hematological toxicities and 20 other toxicities. 39 kinetics could be collected. CDA activity range from 0.86 to 8.56 U/mg. Mean and median CDA activity were respectively 2.6 and 2.2 U/mg, which is not different from our previous study. There was not difference in CDA activity between patients with early severe hematological toxicities versus no toxicities. For rs2072671 SNP, 38 patients were wild-type, 41 heterozygous and 14 were homozygous variant (92 samples). Patients with a C/C genotype were not at higher risk of early severe toxicity. PK of GEM and dFdU was best described by a 3-compartment model, with a first order transfer rate. BSA was covariate of dFdU volume distribution and clearance of first dFdU compartment, whereas age was a covariate of volume of distribution of the second dFdU compartment. We evidenced CDA as a covariate of inter-compartmental clearance of dFdU, and not as a covariate of GEM to dFdU clearance as expected. This multicenter prospective clinical trial doesn't confirm predictive role of CDA status in occurrence of early severe toxicities in patients with pancreatic adenocarcinoma treated with GEM only. Genotypic data could neither explain discrepancies in toxicity. Furthermore, we designed a sparse data pharmacokinetic study allowing to estimate population and individual parameters of GEM from few samples. However, this trial doesn't reflect the wide inter-individual variability observed in routine. Selection in patients must introduce a bias, especially by selecting pancreatic ADK patients. Predictive role of CDA in occurrence of toxicity should be investigated in a larger cohort including various cancers. Citation Format: Cindy SERDJEBI, Florence GATTACCECA, Martina SCHNEIDER, Carole MONTERYMARD, Jaic CARIO, Karine LE MALICOT, Madani RACHID, Bruno LACARELLE, Jean-François SEITZ, Joseph CICCOLINI, Laetitia DAHAN. PGx of gemcitabine in pancreatic ADK: Where did we go wrong. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5479. doi:10.1158/1538-7445.AM2015-5479

Abstract 5549: Recipient-donor contradictory genotype with impact on anticancer drug pharmacogenetics after liver transplant: A deadly gift

Abstract A 5-year old girl with liver transplant was scheduled for a therapy including high-dose cytarabine for her Burkitt lymphoma. Cytarabine pharmacogenetics focus on cytidine deaminase (CDA) , the polymorphic liver enzyme responsible for its detoxification. Preliminary double testing for her CDA status on DNA lymphocytes showed none of the germline polymorphisms usually associated with CDA deficiency (ie, 79A&amp;gt;C (K27Q), 208G&amp;gt;A), but surprisingly with a functional mild deficiency syndrom. Despite 30% reduction in cytarabine dosing, life-threatening toxicities showed quickly and treatment was discontinued. Genetic HRM-based investigations performed in the patient on liver biopsy failed in generating a clear genotype. Further HRM+sequencing retrospective investigations on liver biopsy collected from the donor showed that he was actually bearing the homozygous CDA*2 allelic variant (ie, 79AA), a genotype usually associated with severe CDA deficiency. Based upon the donor liver genotype, and not the recipient genotype, treatement was resumed with further dose reduction, close monitoring and better tolerance eventually. The patient is now in complete remission more than a year after completion of the treatment. This case report illustrates the limits and risks of searching germline polymorphisms in patients with liver transplant when the story plays in the liver. Citation Format: Cindy Serdjebi, Raphaelle Fanciullino, Frederic Fina, Arnaud Verschuur, Bertrand Roquelaure, Bruno Lacarelle, L'Houcine Ouafik, Joseph Ciccolini, Nicolas André. Recipient-donor contradictory genotype with impact on anticancer drug pharmacogenetics after liver transplant: A deadly gift. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5549. doi:10.1158/1538-7445.AM2014-5549

Cytidine Deaminase Status As a Predictive Marker Of Response and Toxicity In Patients With Haematological Malignancies Treated With Azacytidine Or Cytarabine

BackgroundCytarabine and azacytidine are mainstays for treating haematological malignancies. As most nucleosidic analogs, both azacytidine and cytarabine are metabolized in the liver by an exclusive enzymatic step driven by cytidine deaminase (CDA). CDA expression polymorphism has been associated with clinical outcome in patients treated with gemcitabine. MethodsWe determined CDA levels in 39 adult patients (16F, 23M, mean age 77 years), treated mainly for AML and myelodysplastic syndromes with either aza-cytidine or a cytarabine-containing regimen. Response and treatment-related toxicities were monitored following current standards. In addition, impact of CDA status on azacytidine tolerance was evaluated in mice with or without CDA deficiency, as a proof of concept for the actual implication of metabolic deregulations in the toxicities observed in patients. ResultsIn patients, mean CDA activity was 3.7 +/-2.8 U/mg (min: 1, max: 14.8 U/mg). Ten out of 39 patients (i.e., 25%) had low CDA activities and were considered as poor metabolizers (PM). Conversely, 8 patients (i.e., 20%) displayed high CDA activities (i.e., > 6U/mg) and were considered as high metabolizers (HM). PM showed severe toxicities, including two toxic-deaths. Conversely, HM showed little efficacy when treated with either azacytidine or cytarabine. In mice with CDA-deficiency, standard dose azacytidine led to profound and long-lasting neutropenia, as compared with normal mice. Drug monitoring confirmed that individuals with low CDA activity and toxicities showed higher concentrations of azacytidine as compared with normal individuals. Conclusionsthis study suggests that CDA status could be a relevant marker for predicting clinical outcome in patients treated with either azacytidine or cytarabine. CDA status could be further used as a covariate to tailor drug dosage so as to ensure an optimal efficacy/toxicity balance in patients with haematological malignancies. Disclosures:No relevant conflicts of interest to declare.

Cytidine deaminase status as a predictive marker in patients with hematologic malignancies treated with azacytidine or cytarabine.

7117 Background: Cytarabine and azacytidine are mainstays for treating haematological malignancies. As most nucleosidic analogs, both azacytidine and cytarabine are metabolized in the liver by an exclusive enzymatic step driven by cytidine deaminase (CDA). CDA is highly polymorphic and dysregulations have been repeatedly associated with poor clinical outcome with gemcitabine. Methods: We have used a test to determine, on a phenotype basis, CDA status in patients. This test was used prospectively in a subset of 39 adult patients (16F, 23M, mean age 77 years), all treated for various haematological malignancies (i.e., CML, AML, lymphomas, myelodysplastic syndromes) with either aza-cytidine or a cytarabine-containing regimen. Response and treatment-related toxicities were monitored following current standards. In addition, impact of CDA status on azacytidine tolerance was evaluated in mice with or without CDA deficiency, as a proof of concept for the actual implication of metabolic deregulations in the toxicities observed in patients. Results: In patients, mean CDA activity was 3.7 +/-2.8 U/mg (min: 1, max: 14.8 U/mg). Ten out of 39 patients (i.e., 25%) showed low CDA activities and were considered as PM. Conversely, 8 patients (i.e., 20%) displayed CDA activities particurlary elevated (i.e., &gt; 6U/mg) and were considered as UM patients. Of note, PM patients all showed severe toxicities, including two toxic-deaths. Conversely, UM patients showed little efficacy when treated with either azacytidine or cytarabine. In mice with CDA-deficiency, standard azacytidine led to profound and long-lasting neutropenia, as compared with normal mice. Drug monitoring confirmed that individuals with low CDA activity and toxicities showed higher concentrations of azacytidine as compared with normal individuals. Conclusions: Overall this pilot study strongly suggests that CDA status could be a relevant marker for predicting clinical outcome in patients treated with either azacytidine or cytarabine. CDA status could be further used as a covariate to tailor drug dosage so as to ensure an optimal efficacy/toxicity balance in patients with haematological malignancies.

Abstract 1869: Severe toxicities in patients undergoing gemcitabine, ARA-C, capecitabine, or azacytidine treatments: Is deregulated cytidine deaminase the bad guy

Abstract Background: Nucleoside analogs are anticancer drugs widely used both in adults and in children. Genetic polymorphisms leading to impaired ability to detoxify drugs in the liver are a major issue in clinical oncology. Cytidine deaminase (CDA) is a ubiquituous enzyme responsible for the metabolism of several pyrimidine derivatives. CDA is involved in the activation pattern of capecitabine, but conversely is responsible for the liver catabolism of most other nucleosidic analogs. So far, downregulated CDA is considered as an issue with gemcitabine, but little is known about the impact of deregulated CDA on the clinical outcome with other pyrimidine analogs. Methods: A retrospective study was perfomed as a proof-of-concept for the implication of CDA in severe toxicities with several pyrimidine analogs. Phenotypic and genotypic investigations were performed in a subset of patients presenting with severe toxicities soon after being treated for the first time with a pyrimidine derivative. CDA status was evaluated on a phenotypic basis using a surrogate enzymatic test. Additionally, polymorphisms associated with loss of CDA activity (i.e. 79A&amp;gt;C, 435 T&amp;gt;C, 208 G&amp;gt;A mutations) or conversely with increased expression (i.e. rs532545 deletion) were screened. Toxicities were monitored following the standard CTC 4.0 grading. Results &amp; Discussion: We followed five patients (4 adults, 1 child), all presenting with extremely severe toxicities soon after being treated with a nucleoside analog (i.e. capecitabine, gemcitabine, azacytidine and ara-C, respectively). Two patients treated with capecitabine underwent severe toxicities, including a lethal one. Both patients were phenotyped as CDA ultra-metabolizer (UM: CDA &amp;gt; 6 U/mg). The rs532545 deletion in the CDA promoter region was found in the patient with lethal outcome. This suggests that CDA UM status triggers toxicities through an increased activation of capecitabine towards its toxics metabolites. Conversely, poor metabolizer (PM) profile (i.e. CDA &amp;lt; 2 U/mg) was evidenced in the 3 other patients with severe toxicities upon gemcitabine, azacytidine and Ara-C intake. Of note, one of the patient exhibited the double 79A&amp;gt;C and rs532545 polymorphisms, which have opposite impacts on CDA levels eventually. In this case, phenotypic determination proved to be critical to picture the CDA status, and confirmed her PM phenotype. Our observations suggest that CDA deficiency makes patients administered with gemcitabine, azacytidine and ara-C at risk of early severe toxicities alike. Conclusions: Deregulated CDA (i.e. PM or UM patients) proved to be associated with a serial of severe/lethal toxicities in patients treated with nucleoside analogs frequently administered in clinical oncology. Overall, this POC study warrants the identification of CDA status in patients prior to starting pyrimidine-based treatments. 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 1869. doi:1538-7445.AM2012-1869

Treatment failure upon gemcitabine intake: Is cytidine deaminase extensivity the ideal culprit?

e14558 Background: Gemcitabine is a mainstay for treating various solid tumors, including pancreatic and lung cancers, as well as sarcomas. Gemcitabine metabolism in the body is dependent primarily upon a detoxification step in the liver driven by cytidine deaminase (CDA). Activity in CDA is highly variable among patients, with possible impact on drug disposition and subsequent clinical outcome. The aim of this work was to investigate whether extensivity in CDA could be at the origin of treatment failure with gemcitabine. Methods: Forty patients (19F, 21 M, mean age 61 years) mostly treated with gemcitabine alone (23 patients) or associated with oxaliplatin, capecitabine, erlotinib or a biotherapy (7 patients) for pancreatic or biliary cancers were retrospectively studied. CDA status was evaluated both upon a phenotypic (CDA residual activity in serum) and a genotypic (search for the 79A>C polymorphism) basis. Extensive Metabolizer (EM) phenotype was defined as a CDA activity above 6 U/mg (e.g., 50% above the mean value of a reference adult population). Results: Median CDA activity was 3.4 U/mg (range: 0.8-17.4). No genotype to phenotype relationship was evidenced. Eight out of 40 patients (20%) displayed CDA values associated with the EM phenotype (range: 6-17.4). A statistical difference (p < 0.001, Mann-Whitney Rank Sum Test) was observed in response between EM and non-EM patients. In the EM subset, 75% of the patients had progressive disease (PD), the remaining 25% patients displaying equally Objective Response and Stable Disease. Conversely, Progressive disease was observed in 15.5% patients with normal/low CDA activities, whereas 84.5% had controlled disease. Conclusions: Our data suggest that EM with CDA could be a predictive marker for treatment failure with gemcitabine. Complementary data from patients with sarcoma are currently evaluated and should be presented. Overall, our data suggest that CDA-based adaptive dosing strategies could improve clinical outcome with gemcitabine, one of the most prescribed anticancer drug worldwide. No significant financial relationships to disclose.

Anticipating gemcitabine-related severe/lethal toxicities: A feasibility study

14652 Background: Gemcitabine is an antimetabolite drug extensively used for treating solid tumors in adults. Gemcitabine pharmacokinetics is altered by Cytidine Deaminase (CDA) gene polymorphism, resulting in impaired detoxification, systemic overexposure and potentially severe toxicities in deficient patients. To ensure a better safety in the handling of gemcitabine, we have developed a simple and rapid phenotypic test to determine the CDA status in patients with cancer. The aim of this work was to evaluate the feasibility and relevance of screening CDA status in patients undergoing gemcitabine-based therapy. Methods: CDA status was evaluated by measuring spectrophotometrically the residual CDA activity in serum. This retrospective study was performed in 100 adult patients (56M/44F, 64± 16 years) with either lung, pancreatic or vesical cancers. Early toxicities were monitored following standard NCI grading. Results: Four patients (2M/2F, mean age 68± 9 years, mean gemcitabine dose: 1200± 240 mg/m2) displayed early severe toxicities (e.g., > grade 3), including one toxic-death. Mean recorded CDA activities in non-toxic patients were 3.5± 2 U/mg protein. Conversely, mean CDA activities in patients with severe/lethal toxicities upon gemcitabine intake were as low as 0.8± 0.14 U/mg (i.e., -77% vs non-toxic patients), thus suggesting that CDA deficiency could be at the origin of the side-effects reported. Conclusions: In this study, 4% of the patients administred with gemcitabine displayed severe or lethal (1%) toxicities. All of them showed marked impairment in CDA function, as measured with the phenotypic test we used. These preliminary data strongly suggests, therefore, that our simple test could be of interest in a routine setting to detect CDA-deficient patients at risk with gemcitabine, a major drug extensively used in clinical oncology. No significant financial relationships to disclose.

Toxic death case in a patient undergoing gemcitabine-based chemotherapy in relation with cytidine deaminase downregulation

Gemcitabine is an antimetabolite drug used in the treatment of various solid tumours, including lung, pancreatic or gynaecological cancers. Innovative combinational strategies (e.g. gemcitabine+capecitabine or gemcitabine+oxaliplatin) make gemcitabine an extensively prescribed drug now. Gemcitabine is characterized by a narrow therapeutic index, and its liver elimination depends upon a key enzymatic step, driven by cytidine deaminase (CDA). CDA is prone to gene polymorphism, including the 208A>G mutation, which can result in marked enzymatic deficiency with subsequent impact on drug exposure levels and related toxicities. We have developed a simple and inexpensive method to determine phenotypically CDA status in cancer patients, as an attempt to detect those at risk upon gemcitabine intake. Conjointly to genotypic investigations, this method was used to phenotype, in a retrospective setting, a female patient displaying extremely severe, and eventually lethal, toxicities after administration of a standard gemcitabine/carboplatin protocol. Phenotypic investigation showed a marked CDA deficiency (-75%) in this patient when compared with a reference, nontoxic population. Genetic studies undertaken next to screen mutations, possibly at the origin of this deficiency, showed heterozygosity for the 79A>C single-point mutation, whereas surprisingly the canonical CDA 208A>G polymorphism was not found. Taken together, this case report demonstrates, for the first time, that CDA downregulation can lead to toxic-death in patients exposed to gemcitabine. Besides, we showed here that our cost-effective and simple phenotypic approach should enable, in the future, the detection of deficient patients at risk upon gemcitabine administration.