ABSTRACT
With cancer diagnosis occurring at older ages, the use of immune checkpoint inhibitors (ICIs) has extended to older adults. However, the safety of immune-related adverse events (irAEs) in this population remains unclear and relies on data extrapolated from younger adults. This multicenter retrospective study aimed to examine irAE prevalence and tolerability in older adults. We included 436 patients with non-small lung cancer undergoing ICI therapy and dichotomized them into two age groups (< or ≥75 years). Incidence of any irAE grade, grade ≥3 irAEs, and steroid usage after irAE occurrence was similar between younger (n = 332) and older groups (n = 104). While the younger patients with irAEs showed prolonged overall survival in the 12-month landmark Kaplan-Meier analysis (Hazard ratio (HR) 0.59, 95% confidence interval (CI) 0.38-0.89, p = 0.013), the older cohort did not (HR 0.80, 95% CI 0.36-1.78, p = 0.588). Although no differences were observed with ICI continuation or re-challenge after irAE onset, the elderly cohort had double the irAE cases that required a transition to best supportive care (BSC) (11.3% vs. 22.4%, p = 0.026). In conclusion, although irAE prevalence remains consistent regardless of age, the increased conversion to BSC post-irAE onset in older adults suggests diminished tolerability and the potential absence of favorable prognosis associated with irAEs in this population.
ABSTRACT
This study sought to develop a specific and sensitive sandwich enzyme-linked immunosorbent assay (ELISA) for pharmacokinetic studies of dasatinib, a tyrosine kinase inhibitor. Anti-dasatinib antibodies were obtained from mice or rabbits by using two partial structures of dasatinib as haptens: 2-amino-N-(2-chloro-6-methylphenyl)-thiazole-5-carboxamide and 2-{4-(2-hydroxyethyl)-1-piperazinyl}-isonicotinic acid. The best combination of two antibodies for sandwich ELISA of dasatinib was determined using four anti-dasatinib antibodies derived from mice and rabbits. Using two dasatinib-specific rabbit antibodies, we successfully developed an ultra-specific and highly sensitive sandwich ELISA that is hardly affected by the main metabolite of dasatinib. The sandwich ELISA showed a linear detection range from 320 pg/mL to 1000 ng/mL. Serum dasatinib concentrations lower than 320 pg/mL were reproducibly measurable using the sandwich ELISA. The ELISA was specific to dasatinib and there were no cross-reactivities with the major metabolites 4'-hydroxy dasatinib and dasatinib carboxylic acid. The developed sandwich ELISA will be a valuable tool for pharmacokinetic studies of dasatinib. Furthermore, this study revealed that rabbit antibodies can sandwich drug molecules of a smaller size than mouse antibodies in sandwich ELISA.
Subject(s)
Dasatinib , Protein Kinase Inhibitors , Animals , Mice , Rabbits , Antibodies , Enzyme-Linked Immunosorbent AssayABSTRACT
Osimertinib is a third-generation, irreversible tyrosine kinase inhibitor (TKI) of epidermal growth factor receptor (EGFR) that selectively inhibits both EGFR-TKI-sensitizing and EGFR T790M resistance mutations and has shown efficacy in patients with non-small-cell lung cancer. In this study, we created osimertinib-specific antibodies and developed an immunohistochemistry (IHC) for locating the sites of osimertinib action. Moreover, we located osimertinib-protein conjugates in intestinal, dermal, and lung tissues of rats, thereby using our IHC to visualize the sites of the adverse effects of osimertinib, including diarrhea, skin disorder, and interstitial pneumonia. This report is the first to elucidate the localization of the sites of action of osimertinib in the rat intestine, skin, and lung and is expected to help clarify the mechanism of osimertinib-induced adverse effects.
ABSTRACT
Aromatic amides bearing secondary amide bond exist in trans conformation both in the crystal and in solution, whereas the conformation of the N-methylated derivatives is cis in the crystal and predominantly cis in various solvents. The cis conformational preference of N-alkylated benzanilide provides access to aromatic foldamers such as oligo(N-alkyl-p-benzamide)s, which adopt dynamic helical structures. Here, the conformational properties of imidazole-substituted amide in the crystal and in solution were examined. Imidazole-substituted amides 2a and 4a existed mainly in the cis conformation in solution. The ratio of the cis conformer of N-methyl-N-(1-methyl-1H-imidazol-4-yl)benzamide (4a) was smaller than that of N,1-dimethyl-N-phenyl-1H-imidazole-2-carboxamide (2a) or N-methylbenzanilide, but the introduction of a substituent strongly affected the conformer ratio. Compounds 6a and 7a bearing an electron-withdrawing group on the imidazole ring existed predominantly in trans form. On the other hand, the introduction of an electron-withdrawing group on the phenyl ring or a bulky substituent on the amide nitrogen of 4a increased the ratio of cis conformer. Further, the major conformer of N-alkylated N-imidazolylamides was switched from cis to trans by the addition of acid. These results suggest that imidazole-substituted amides might be applicable as conformational switches in aromatic foldamers to enable environment-dependent structural change.
ABSTRACT
BACKGROUND/AIM: There is limited evidence about the nephrotoxicity of calcium channel blockers (CCBs) and renin-angiotensin system (RAS) inhibitors with concomitant cisplatin (CDDP). We investigated whether combinations of antihypertensive drugs are associated with CDDP-related acute kidney injury (AKI) using the Japanese Adverse Drug Event Report database. PATIENTS AND METHODS: We analysed 544,864 reports in the database from 2004 to 2020. A reporting odds ratio (ROR) and confidence interval (CI) with adjustment for potential confounding factors was calculated for AKI for each drug and the combined use of the drugs and CDDP. RESULTS: CDDP, CCBs, and RAS inhibitors were all detected signals for AKI. The ROR in cases with concomitant use of CCBs, RAS inhibitors, and CDDP (adjusted ROR 7.28; 95% CI=5.56-9.54) was higher than that in cases with use of each drug. CONCLUSION: AKI may require more attention when patients receiving CDDP take CCBs and RAS inhibitors together.
Subject(s)
Acute Kidney Injury , Drug-Related Side Effects and Adverse Reactions , Acute Kidney Injury/chemically induced , Antihypertensive Agents/adverse effects , Cisplatin/adverse effects , Databases, Factual , Female , Humans , MaleABSTRACT
Sunitinib is an oral multi-targeted tyrosine kinase inhibitor approved for treating metastatic renal cell carcinoma. This study reports a specific and sensitive competitive enzyme-linked immunosorbent assay (ELISA) for the pharmacokinetic evaluation of sunitinib. Anti-sunitinib serum was obtained from mice by using N-(2-(diethylamino)ethyl)-5-formyl-2,4-dimethyl-1H-pyrrole-3-carboxamide (DFPC) as a hapten, which has the same substructure as sunitinib, in order to avoid the effects of structural changes in the geometrical isomers of sunitinib. Enzyme labeling of sunitinib with horseradish peroxidase was similarly performed using DFPC. Serum sunitinib concentrations below the limit of quantification of 0.52 ng/mL were reproducibly measurable. This ELISA was speciï¬c for sunitinib (Z- and E-isomers) and showed very low cross-reactivity (0.094%) with its major metabolite, N-desethyl sunitinib. Its analytical applicability was demonstrated by a kinetic study with human liver microsomes. In addition, the levels of sunitinib measured by ELISA in a kinetic study with human liver microsomes were comparable with those measured by HPLC, and there was a strong correlation between the values determined by both methods (y = 1.065x - 51.2, R2 = 0.9804). The developed ELISA provides for the specific and sensitive quantification of sunitinib without the influence of its major metabolite or light-induced geometric isomers. This ELISA will be a valuable tool in pharmacokinetic studies of sunitinib.
Subject(s)
Drug Monitoring/methods , Sunitinib/analysis , Animals , Cross Reactions , Enzyme-Linked Immunosorbent Assay/methods , Female , Humans , Isomerism , Light/adverse effects , Limit of Detection , Mice , Microsomes, Liver , Models, Animal , Sunitinib/chemistry , Sunitinib/pharmacokinetics , Sunitinib/radiation effectsABSTRACT
PURPOSE: Palonosetron, a long-acting 5-HT3 receptor antagonist, is an effective antiemetic agent for chemotherapy-induced nausea and vomiting; however, it sometimes causes severe constipation. The aim of the present study was to evaluate the severity of palonosetron-related constipation. METHODS: We retrospectively analyzed the incidence and severity of constipation after intravenous administration of 0.75-mg palonosetron in 150 chemotherapy-naïve patients who received first-line chemotherapy at Saga University Hospital. Constipation was classified into grades 1-5 according to the Common Terminology Criteria for Adverse Events version 5.0. Multiple logistic regression analysis was performed to identify factors associated with palonosetron-related worsening of constipation to grade 2 or higher. RESULTS: Palonosetron significantly increased the incidence and severity of constipation (incidence: before vs. after palonosetron, 35.4% vs. 74.0%, p < 0.0001, and severity: before vs. after palonosetron, 26.7% and 8.7% in grades 1 and 2, respectively, vs. 46.7%, 23.3%, and 4.0% in grades 1, 2, and 3, respectively, p < 0.0001). Despite the use of laxatives, 4.0% of patients had grade 3 constipation requiring manual evacuation. Combination treatment with aprepitant (odds ratio (OR), 10.9; 95% confidence interval (CI), 1.3-90.0; p = 0.026) and older age (OR, 1.25; 95% CI, 1.01-1.57; p = 0.039) were factors associated with the severity of constipation. CONCLUSION: Constipation was more severe in patients receiving combination treatment with aprepitant than in those treated with palonosetron alone. Older age was also associated with increased risk of severe palonosetron-related constipation. Identification of risk factors can help target risk-based laxative therapy.
Subject(s)
Antiemetics/adverse effects , Constipation/chemically induced , Palonosetron/adverse effects , Adult , Aged , Aged, 80 and over , Female , Humans , Male , Middle Aged , Retrospective Studies , Young AdultABSTRACT
Background: Although the biological agent ustekinumab (UST) is reported to be effective for Crohn's disease (CD) in pediatric as well as adult patients, data on the efficacy and safety of UST in pediatric patients with CD are limited. Here, we describe the case of a pediatric patient who showed an allergic reaction to UST after subcutaneous (SC) maintenance injections but not immediately after initial intravenous (IV) injection. Case Presentation: A 9-year-old boy presented to our hospital with diarrhea lasting 2 years and weight loss, leading to the diagnosis of CD. After prednisolone (PSL) was tapered and discontinued, he promptly relapsed. According to our institution's protocol, we introduced the biological agent infliximab (IFX) with premedication. Coughing and vomiting was observed after the second dose of IFX and it was changed to adalimumab (ADA). However, the effect of ADA gradually disappeared after 18 months; therefore, it was discontinued and he was treated using UST. The first IV UST dose was given after administering hydrocortisone (HDC), an antiallergic and antipyretic analgesic, as premedication, and no obvious adverse reaction was observed. After 8 weeks, UST was subcutaneously injected without premedication. The patient then complained of nausea, dizziness, and headache within 15 min of UST administration. Therefore, for the third dose of UST, HDC was administered again as premedication. However, nausea, dizziness, and headache presented 10 min after UST administration, resulting in discontinuation of further UST treatment. Conclusion: Careful distinction between "true" infusion-related reactions (IRRs) and anaphylaxis or allergic reactions is necessary to determine whether biological agents can be continued after the development of "so-called" IRRs. For true IRRs, it may be possible to continue using the biological agent with appropriate premedication; however, in cases of anaphylaxis, the biological agent itself should be changed.
ABSTRACT
Lithium, which is used for bipolar disorder, can cause toxicity. There are two categories of lithium toxicity, namely, overdose-related and not overdose-related. However, the treatment and prognosis of each type of toxicity are not clearly understood. We, therefore, compared the clinical characteristics of patients with overdose-related and not overdose-related lithium toxicity. Relevant data were obtained from the medical records of 16 patients with lithium toxicity, and renal function and concomitant medications were retrospectively compared between the two groups. We also compared the treatment for, manifestations of, and duration of hospitalization between the two types of lithium toxicity. The not overdose-related group more frequently had a low creatinine clearance (<50 mL/min) than did the overdose-related group (P = 0.01). Multivariable regression analysis demonstrated that creatinine clearance <50 mL/min was a significant predictor of lithium toxicity in the not overdose-related group (P = 0.01). Tremor and dysarthria occurred only in the not overdose-related group, and duration of hospitalization was significantly longer in the not overdose-related than overdose-related group (P = 0.01). Clinicians must monitor the renal function of patients taking lithium, even when in compliance with the prescribed dosage, because they are at long-term risk of lithium toxicity.
Subject(s)
Bipolar Disorder , Kidney , Lithium , Bipolar Disorder/drug therapy , Humans , Kidney/physiology , Lithium/toxicity , Retrospective StudiesABSTRACT
BACKGROUND/AIM: Afatinib, a 2nd generation epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI) used in treatment of non-small cell lung cancer (NSCLC), causes diarrhoea in over 90% of patients. The association of genetic background with diarrhoea is poorly understood. PATIENTS AND METHODS: We evaluated the roles of four single nucleotide polymorphisms (SNPs) in ATP binding cassette subfamily B member 1 (ABCB1) and ATP binding cassette subfamily G member 2 (ABCG2) genes-ABCB1 1236 C>T, 2677 G>T/A, and 3435 C>T, and ABCG2 421 C>A-on treatment-induced diarrhoea in 38 patients with NSCLC treated with afatinib. RESULTS: Diarrhoea occurred more frequently in patients with ABCB1 2677 T(A)/T(A) (14/16, 87.5%) than in patients with non-T(A)/T(A) alleles (8/22, 36.4%) (p=0.003). ABCB1 2677 T(A)/T(A) was significantly predictive of diarrhoea (p=0.002) by multivariable regression analysis. CONCLUSION: Afatinib-induced diarrhoea is associated with the SNP ABCB1 2677 T(A)/T(A).
Subject(s)
Afatinib/adverse effects , Antineoplastic Agents/adverse effects , Diarrhea/etiology , Genetic Predisposition to Disease , Polymorphism, Single Nucleotide , Protein Kinase Inhibitors/adverse effects , ATP Binding Cassette Transporter, Subfamily B/genetics , ATP Binding Cassette Transporter, Subfamily G, Member 2/genetics , Afatinib/therapeutic use , Aged , Aged, 80 and over , Antineoplastic Agents/therapeutic use , Diarrhea/diagnosis , Female , Humans , Incidence , Male , Middle Aged , Neoplasm Proteins/genetics , Odds Ratio , Protein Kinase Inhibitors/therapeutic useABSTRACT
Before surgery and other invasive treatments, decisions must be made on whether to discontinue drugs and provide appropriate drug holidays especially for antithrombotic drugs, and this is made difficult by the large number of available drugs and associated guidelines. We have therefore developed an online application for perioperative drug discontinuation and resumption management, named Saga Application for Management of Drug Holidays in PeriOperative Periods (SAMPOP).Multidisciplinary medical staff at Saga University Hospital (SUH) worked together to build an evidence-based Perioperative Drug Discontinuation Management Database (PDDMD) and developed the user-friendly SAMPOP online application via preliminary verification at SUH. From September 2018 to February 2020, 420 medical staff at SUH, including physicians, nurses, and pharmacists, installed and tested SAMPOP.Rate per surgical procedure for forgetting to discontinue antithrombotic drugs preoperatively decreased from 0.18% to 0.09% as of August 2019, 12 months after the introduction of SAMPOP (Pâ=â.1359). In addition, six months later, it decreased further to 0.03% as of February 2020 (Pâ=â.0436). Forgetting to resume antithrombotic drugs postoperatively decreased from 0.20% to 0.02% as of August 2019, 12 months after the introduction of SAMPOP (Pâ=â.0008). There was no case of forgetting to resume the medication in the last 6 months.SAMPOP may be useful for management of drug holidays in the clinic and warrants further evaluation of its safety and efficacy.
Subject(s)
Blood Loss, Surgical/prevention & control , Fibrinolytic Agents/administration & dosage , Medication Therapy Management/organization & administration , Perioperative Period , Electronic Health Records , Humans , InternetABSTRACT
Afatinib, a second-generation tyrosine kinase inhibitor, was designed to bind covalently to and irreversibly inhibit active ErbB family receptors. The major metabolites of afatinib in human plasma are adducts of afatinib covalently bound to plasma proteins via. the Michael addition reaction. These findings suggest that afatinib may form covalent bonds with proteins in tissue and be localized in tissue. However, there is no method for the specific detection of afatinib-protein conjugates localized in tissue. In this paper, we aimed to develop an immunohistochemical protocol to detect afatinib-protein conjugates. Immunostainings were performed with male rat intestinal tract and skin at 24â¯h after an oral administration of afatinib. In the intestinal tract, strong staining was observed in the ileum and colon, but only slight staining was observed in the duodenum and jejunum. In the skin, strong staining was observed in the epidermis, sebaceous glands and hair follicles. Immunohistochemistry for afatinib-protein conjugates could be a useful tool to detect the localization of such conjugates. This study is the first to elucidate the localization of afatinib-protein conjugates in the rat intestinal tract and skin and is expected to be of great use in efforts to clarify the mechanism underlying afatinib-induced diarrhoea or skin toxicities.
Subject(s)
Afatinib , Intestinal Mucosa/metabolism , Skin/metabolism , Administration, Oral , Afatinib/pharmacokinetics , Afatinib/pharmacology , Animals , Immunohistochemistry , Male , Rats , Rats, WistarABSTRACT
Afatinib is an oral tyrosine kinase inhibitor (TKI) approved for treating advanced non-small cell lung cancer. It is necessary to develop a simple quantification method for TKIs in order to facilitate therapeutic drug monitoring (TDM) in clinical settings. This study sought to develop a simple and sensitive competitive enzyme-linked immunosorbent assay (ELISA) to quantify afatinib in plasma for routine pharmacokinetic applications. An anti-afatinib antibody was obtained using (S)-N-4-(3-chloro-4-fluorophenyl)-7-(tetrahydrofuran-3-yloxy)-quinazoline-4,6-diamine (CTQD), which has the same substructure as afatinib, as a hapten. Enzyme labeling of afatinib with horseradish peroxidase was similarly performed using CTQD. A simple competitive ELISA for afatinib was developed based on the principle of direct competition between afatinib and the enzyme marker for the anti-afatinib antibody, which had been immobilized on the plastic surface of a microtiter plate. Plasma afatinib concentrations below the limit of quantification of 30â¯pg/mL were reproducibly measurable. Also, the values of plasma afatinib levels measured from 20 patients were comparable with those measured by high-performance liquid chromatography, and there was a strong correlation between the values determined by both methods (Y = 0.976X - 0.207, râ¯=â¯0.975). As indicated by its specificity and sensitivity, this newly developed ELISA for afatinib is an important tool for TDM and studies of the pharmacokinetics of afatinib.
ABSTRACT
The tyrosine kinase inhibitor ponatinib is extensively metabolized in the body, and consequently the development of specific immunoassays for pharmacokinetic studies and therapeutic drug monitoring of ponatinib is challenging. If two antibodies simultaneously recognize the entire structure of ponatinib, they could be utilized to establish an ultra-specific sandwich immunoassay for ponatinib, free of any interference from ponatinib metabolites. In this study, we created two types of anti-ponatinib polyclonal antibodies that recognize two different ponatinib epitopes, and sandwiched almost all structural components of ponatinib in these two antibodies in order to develop an enzyme-linked immunosorbent assay (ELISA) technique not affected by any ponatinib metabolites. After optimization, this sandwich ELISA showed a linear detection range of 640 pg/mL to 2000 ng/mL and a limit of quantification of 640 pg/mL. This sandwich ELISA was specific to ponatinib and showed no cross-reactivity with the major metabolite M14. Comparison between the sandwich ELISA and HPLC, using serum samples from 15 rats orally administered a single dose of 15 mg/kg ponatinib, showed a linear regression (y = 0.9662x + 3.5354, r = 0.9683). Thus, in this study, we successfully developed the first ultra-specific sandwich ELISA for ponatinib in serum.
Subject(s)
Enzyme-Linked Immunosorbent Assay , Imidazoles/blood , Pyridazines/blood , Humans , Imidazoles/metabolism , Molecular Structure , Pyridazines/metabolismABSTRACT
Afatinib is an oral tyrosine kinase inhibitor (TKI) approved for treating advanced non-small cell lung cancer. It is necessary to develop a simple quantification method for TKIs in order to facilitate therapeutic drug monitoring (TDM) in clinical settings. This study sought to develop a simple and sensitive com-petitive enzyme-linked immunosorbent assay (ELISA) to quantify afatinib in plasma for routine phar-macokinetic applications. An anti-afatinib antibody was obtained using (S)-N-4-(3-chloro-4-fluor-ophenyl)-7-(tetrahydrofuran-3-yloxy)-quinazoline-4,6-diamine (CTQD), which has the same sub-structure as afatinib, as a hapten. Enzyme labeling of afatinib with horseradish peroxidase was similarly performed using CTQD. A simple competitive ELISA for afatinib was developed based on the principle of direct competition between afatinib and the enzyme marker for the anti-afatinib antibody, which had been immobilized on the plastic surface of a microtiter plate. Plasma afatinib concentrations below the limit of quantification of 30 pg/mL were reproducibly measurable. Also, the values of plasma afatinib levels measured from 20 patients were comparable with those measured by high-performance liquid chromatography, and there was a strong correlation between the values determined by both methods (Y = 0.976X – 0.207, r = 0.975). As indicated by its specificity and sensitivity, this newly developed ELISA for afatinib is an important tool for TDM and studies of the pharmacokinetics of afatinib.
ABSTRACT
BACKGROUND: ABL tyrosine kinase inhibitors (TKIs) significantly changed the prognosis of patients with chronic myeloid leukemia (CML), and clinical trials demonstrated that TKIs can be discontinued in approximately 50% of patients after a period of deep molecular response (DMR). However, in some patients, TKI discontinuation leads to anxiety and depression. Here, we analysed the incidence of anxiety and depression in patients who stop TKI therapy. METHODS: Anxiety and depression were evaluated using the Hospital Anxiety and Depression Scale (HADS) in 32 patients with CML. The survey periods were at TKI discontinuation, at 1, 6, 12, and 24 months and at reintroduction of TKIs. The HADS score at the initial TKI discontinuation was compared between patients within and outside clinical trials. Treatment-free remission (TFR) rates outside clinical trials were evaluated. RESULTS: The HADS scores were significantly higher at TKI reintroduction after molecular relapse than at the initial TKI discontinuation (at the initiation of stopping TKIs vs. at reintroduction of TKIs, 8.47 ± 5.53 vs. 1.67 ± 2.26; p = 0.0003). The TFR rate at 12 months after stopping TKIs outside clinical trials was 55.6%. The HADS score at the initial TKI discontinuation did not differ between patients within and outside clinical trials. CONCLUSION: Stopping TKIs outside clinical trials is feasible if the guidelines for stopping are followed and an adequate monitoring system is available. Discontinuation of TKIs requires adequate management of anxiety and depression.
Subject(s)
Anxiety Disorders/chemically induced , Depressive Disorder/chemically induced , Leukemia, Myelogenous, Chronic, BCR-ABL Positive/drug therapy , Neoplasm Recurrence, Local/chemically induced , Protein Kinase Inhibitors/adverse effects , Protein-Tyrosine Kinases/antagonists & inhibitors , Anxiety Disorders/epidemiology , Depressive Disorder/epidemiology , Female , Humans , Japan/epidemiology , Male , Middle Aged , Neoplasm Recurrence, Local/epidemiology , Retrospective Studies , Survival Rate , Treatment Outcome , Withholding TreatmentABSTRACT
The development of an immunoassay for a low-molecular-weight drug first requires the identification of specific antibodies that do not cross-react with the drug's metabolites. If two antibodies can simultaneously recognize the entire structure of the drug, we can then utilize them to establish an ultra-specific sandwich ELISA, free from interference due to the metabolic products of the drug. This paper reports an ultra-specific and sensitive sandwich ELISA for determination of the tyrosine kinase inhibitor imatinib using two anti-imatinib antibodies. The anti-imatinib antibodies were obtained by two partial structures of imatinib as haptens (2-(5-amino-2-methylanilino)-4-(3-pyridyl)pyrimidine and 4-{(4-methyl-1-piperazinyl)-methyl}-benzoate). Under optimized conditions, this sandwich ELISA shows a linear detection range from 64 pg mL-1 to 8 ng mL-1, and a limit of detection of approximately 64 pg mL-1 for 100-µL samples. The ELISA is specific to imatinib and while there was no cross-reactivity with the major metabolite N-desmethyl-imatinib, slight cross-reactivity was found with metabolite pyridine-N-oxide-imatinib. This assay demonstrated significantly lower cross-reactivity with metabolites than competitive ELISAs. Using this assay, drug levels were easily measured in rat blood after oral administration of imatinib via a single dose of 30 mg kg-1 or 100 mg kg-1. The levels in rat serum measured by this ELISA were comparable with those measured by HPLC, and there was a strong correlation between the values determined by the two methods (y = 0.983x + 0.081, R2 = 0.948). Thus, we have successfully developed the first specific and sensitive sandwich ELISA for imatinib using two anti-imatinib antibodies. This sandwich ELISA will be a valuable tool for therapeutic drug monitoring and pharmacokinetic studies of imatinib.