د. هدير ماهر

Editor's Notes

• #5: Target Oncol. 2012 Mar;7(1):69-85. doi: 10.1007/s11523-012-0212-2. Epub 2012 Feb 15. A review on various targeted anticancer therapies. Li J1, Chen F, Cona MM, Feng Y, Himmelreich U, Oyen R, Verbruggen A, Ni Y. Author information Abstract Translational oncology aims to translate laboratory research into new anticancer therapies. Contrary to conventional surgery, chemotherapy, and radiotherapy, targeted anticancer therapy (TAT) refers to systemic administration of drugs with particular mechanisms that specifically act on well-defined targets or biologic pathways that, when activated or inactivated, may cause regression or destruction of the malignant process, meanwhile with minimized adverse effects on healthy tissues. In this article, we intend to first give a brief review on various known TAT approaches that are deemed promising for clinical applications in the current trend of personalized medicine, and then we will introduce our newly developed approach namely small molecular sequential dual targeting theragnostic strategy as a generalized class of TAT for the management of most solid malignancies, which, after optimization, is expected to help improve overall cancer treatability and curability. Targeted therapy or molecularly targeted therapy is one of the major modalities of medical treatment (pharmacotherapy) for cancer, others being hormonal therapy andcytotoxic chemotherapy. As a form of molecular medicine, targeted therapy blocks the growth of cancer cells by interfering with specific targeted molecules needed forcarcinogenesis and tumor growth,[1] rather than by simply interfering with all rapidly dividing cells (e.g. with traditional chemotherapy). Because most agents for targeted therapy are biopharmaceuticals, the term biologic therapy is sometimes synonymous with targeted therapy when used in the context of cancer therapy (and thus distinguished from chemotherapy, that is, cytotoxic therapy). However, the modalities can be combined; antibody-drug conjugates combine biologic and cytotoxic mechanisms into one targeted therapy. Targeted cancer therapies are expected to be more effective than older forms of treatments and less harmful to normal cells. Many targeted therapies are examples ofimmunotherapy (using immune mechanisms for therapeutic goals) developed by the field of cancer immunology. Thus, as immunomodulators, they are one type of biological response modifiers. The most successful targeted therapies are chemical entities that target or preferentially target a protein or enzyme that carries a mutation or other genetic alteration that is specific to cancer cells and not found in normal host tissue. One of the most successful molecular targeted therapeutic is Gleevec, which is a kinase inhibitor with exceptional affinity for the oncofusion protein BCR-Abl which is a strong driver of tumorigenesis in Chronic Myelogenous Leukemia. Although employed in other indications, Gleevec is most effective targeting BCR-Abl. Other examples of molecular targeted therapeutics targeting mutated oncogenes, include PLX27892 which targets mutant B-raf in melanoma. There are targeted therapies for breast cancer, multiple myeloma, lymphoma, prostate cancer, melanoma and other cancers.[2] The definitive experiments that showed that targeted therapy would reverse the malignant phenotype of tumor cells involved treating Her2/neu transformed cells with monoclonal antibodies in vitro and in vivo by Mark Greene’s laboratory and reported from 1985.[3] Some have challenged the use of the term, stating that drugs usually associated with the term are insufficiently selective.[4] The phrase occasionally appears in scare quotes: "targeted therapy".[5] Targeted therapies may also be described as "chemotherapy" or "non-cytotoxic chemotherapy", as "chemotherapy" strictly means only "treatment by chemicals". But in typical medical and general usage "chemotherapy" is now mostly used specifically for "traditional" cytotoxic chemotherapy. Contents   [hide]  1Types 1.1Small molecules 1.2Small molecule drug conjugates 1.3Serine/threonine kinase inhibitors (small molecules) 1.4Monoclonal antibodies 2Progress and future 3See also 4References 5External links Types[edit] The main categories of targeted therapy are currently small molecules and monoclonal antibodies. Small molecules[edit] Mechanism of imatinib Many are tyrosine-kinase inhibitors. Imatinib mesylate (Gleevec, also known as STI–571) is approved for chronic myelogenous leukemia, gastrointestinal stromal tumor and some other types of cancer. Early clinical trials indicate that imatinib may be effective in treatment ofdermatofibrosarcoma protuberans. Gefitinib (Iressa, also known as ZD1839), targets the epidermal growth factor receptor (EGFR) tyrosine kinase and is approved in the U.S. for non small cell lung cancer. Erlotinib (marketed as Tarceva). Erlotinib inhibits epidermal growth factor receptor,[6] and works through a similar mechanism as gefitinib. Erlotinib has been shown to increase survival in metastatic non small cell lung cancer when used as second line therapy. Because of this finding, erlotinib has replaced gefitinib in this setting. Sorafenib (Nexavar)[7] Sunitinib (Sutent) Dasatinib (Sprycel) Lapatinib (Tykerb) Nilotinib (Tasigna) Bortezomib (Velcade) is an apoptosis-inducing proteasome inhibitor drug that causes cancer cells to undergo cell death by interfering with proteins. It is approved in the U.S.to treat multiple myeloma that has not responded to other treatments. The selective estrogen receptor modulator tamoxifen has been described as the foundation of targeted therapy.[8] Janus kinase inhibitors, e.g. FDA approved tofacitinib ALK inhibitors, e.g. crizotinib Bcl-2 inhibitors (e.g. obatoclax in clinical trials, navitoclax, and gossypol.[9] PARP inhibitors (e.g. Iniparib, Olaparib in clinical trials) PI3K inhibitors (e.g. perifosine in a phase III trial) Apatinib is a selective VEGF Receptor 2 inhibitor which has shown encouraging anti-tumor activity in a broad range of malignancies in clinical trials.[10] Apatinib is currently in clinical development for metastatic gastric carcinoma, metastatic breast cancer and advanced hepatocellular carcinoma.[11] AN-152, (AEZS-108) doxorubicin linked to [D-Lys(6)]- LHRH, Phase II results for ovarian cancer.[12] Braf inhibitors (vemurafenib, dabrafenib, LGX818) used to treat metastatic melanoma that harbors BRAF V600E mutation MEK inhibitors (trametinib, MEK162) are used in experiments, often in combination with BRAF inhibitors to treat melanoma CDK inhibitors, e.g. PD-0332991, LEE011 in clinical trials Hsp90 inhibitors, some in clinical trials salinomycin has demonstrated potency in killing cancer stem cells in both laboratory-created and naturally occurring breast tumors in mice. Small molecule drug conjugates[edit] Vintafolide is a small molecule drug conjugate consisting of a small molecule targeting the folate receptor. It is currently in clinical trials for platinum-resistant ovarian cancer (PROCEED trial) and a Phase 2b study(TARGET trial) in non-small-cell lung carcinoma (NSCLC).[13] Serine/threonine kinase inhibitors (small molecules)[edit] Temsirolimus (Torisel) Everolimus (Afinitor) Vemurafenib (Zelboraf) Trametinib (Mekinist) Dabrafenib (Tafinlar) Monoclonal antibodies[edit] Main article: Monoclonal antibody therapy Several are in development and a few have been licensed by the FDA. Examples of licensed monoclonal antibodies include: Rituximab (marketed as MabThera or Rituxan) targets CD20 found on B cells. It is used in non Hodgkin lymphoma Trastuzumab (Herceptin) targets the Her2/neu (also known as ErbB2) receptor expressed in some types of breast cancer Alemtuzumab Cetuximab (marketed as Erbitux) and Panitumumab target the epidermal growth factor receptor (EGFR). They are used in the treatment of colon cancer and non-small cell lung cancer. Bevacizumab (marketed as Avastin) targets circulating VEGF ligand. It is approved for use in the treatment of colon cancer, breast cancer, non-small cell lung cancer, and is investigational in the treatment of sarcoma. Its use for the treatment of brain tumors has been recommended.[14] Ipilimumab (Yervoy) Many Antibody-drug conjugates (ADCs) are being developed. See also ADEPT (Antibody-directed enzyme prodrug therapy). Progress and future[edit] In the U.S., the National Cancer Institute's Molecular Targets Development Program (MTDP) aims to identify and evaluate molecular targets that may be candidates for drug development. See also[edit] History of cancer chemotherapy#Targeted therapy Targeted drug delivery Targeted molecular therapy for neuroblastoma Targeted therapy of lung cancer Treatment of lung cancer#Targeted therapy Targeted covalent inhibitors References[edit] Jump up^ "Definition of targeted therapy - NCI Dictionary of Cancer Terms". Jump up^ NCI: Targeted Therapy tutorials Jump up^ Perantoni AO, Rice JM, Reed CD, Watatani M, Wenk ML (September 1987). "Activated neu oncogene sequences in primary tumors of the peripheral nervous system induced in rats by transplacental exposure to ethylnitrosourea". Proc. Natl. Acad. Sci. U.S.A. 84(17): 6317–6321. doi:10.1073/pnas.84.17.6317. PMC 299062. PMID 3476947.Drebin JA, Link VC, Weinberg RA, Greene MI (December 1986). "Inhibition of tumor growth by a monoclonal antibody reactive with an oncogene-encoded tumor antigen".Proc. Natl. Acad. Sci. U.S.A. 83 (23): 9129–9133. doi:10.1073/pnas.83.23.9129.PMC 387088. PMID 3466178.Drebin JA, Link VC, Stern DF, Weinberg RA, Greene MI (July 1985). "Down-modulation of an oncogene protein product and reversion of the transformed phenotype by monoclonal antibodies". Cell 41 (3): 697–706. doi:10.1016/S0092-8674(85)80050-7.PMID 2860972. Jump up^ Zhukov NV, Tjulandin SA (May 2008). "Targeted therapy in the treatment of solid tumors: practice contradicts theory". Biochemistry Mosc. 73 (5): 605–618.doi:10.1134/S000629790805012X. PMID 18605984. Jump up^ Markman M (2008). "The promise and perils of 'targeted therapy' of advanced ovarian cancer". Oncology 74 (1–2): 1–6. doi:10.1159/000138349. PMID 18536523. Jump up^ Katzel JA, Fanucchi MP, Li Z (January 2009). "Recent advances of novel targeted therapy in non-small cell lung cancer". J Hematol Oncol 2 (1): 2. doi:10.1186/1756-8722-2-2. PMC 2637898. PMID 19159467. Jump up^ Lacroix, Marc (2014). Targeted Therapies in Cancer. Hauppauge , NY: Nova Sciences Publishers. ISBN 978-1-63321-687-7. Jump up^ Jordan VC (January 2008). "Tamoxifen: catalyst for the change to targeted therapy".Eur. J. Cancer 44 (1): 30–38. doi:10.1016/j.ejca.2007.11.002. PMC 2566958.PMID 18068350. Jump up^ Warr MR, Shore GC (December 2008). "Small-molecule Bcl-2 antagonists as targeted therapy in oncology". Curr Oncol 15 (6): 256–61. PMC 2601021. PMID 19079626. Jump up^ Li J, Zhao X, Chen L, et al. (2010). "Safety and pharmacokinetics of novel selective vascular endothelial growth factor receptor-2 inhibitor YN968D1 in patients with advanced malignancies". BMC Cancer 10: 529. doi:10.1186/1471-2407-10-529.PMC 2984425. PMID 20923544. Jump up^ http://clinicaltrials.gov/ct2/results?term=apatinib Jump up^ "Phase II study of AEZS-108 (AN-152), a targeted cytotoxic LHRH analog, in patients with LHRH receptor-positive platinum resistant ovarian cancer.". 2010. Jump up^ [1] Jump up^ Pollack, Andrew (2009-03-31). "F.D.A. Panel Supports Avastin to Treat Brain Tumor".New York Times. Retrieved 2009-08-13. External links[edit] CancerDriver : a free and open database to find targeted therapies according to the patient's features. Targeted Therapy Database (TTD) [2] from the Melanoma Molecular Map Project [3] Targeted therapy Fact sheet from the U.S. National Cancer Institute Molecular Oncology: Receptor-Based Therapy Special issue of Journal of Clinical Oncology (April 10, 2005) dedicated to targeted therapies in cancer treatment Targeting Targeted Therapy New England Journal of Medicine (2004)
• #7: This remarkable PK variability significantly affects the treatment outcomes (efficacy/toxicity) in various cancer .
• #10: Interaction of Drug or Food with Drug Transporters in Intestine and Liver Takeo Nakanishi and Ikumi Tamai* Current Drug Metabolism, 2015, 16, 000-000 Erlotinib, PKs, The oral bioavailability of erlotinib is ∼76% in cancer patients . Plasma protein binding is 92–95% for erlotinib. Its metabolism is mediated predominantly by CYP3A4 and CYP3A5 in liver and intestine, and to a lesser extent, by CYP1A2 and CYP2C8. An extra-hepatic metabolism through the pulmonary cytochrome CYP1A1 and CYP1B1 expressed in tumour tissue has been identified. Erlotinib is a potent inhibitor of CYP1A1, and a moderate inhibitor of CYP3A4 and CYP2C8, as well as a strong inhibitor of glucuronidation by UGT1A1 in vitro . Erlotinib is a moderate affinity substrate for ABCB1 and ABCG2, as well as an inhibitor of ABCB1, ABCG2 and ABCC10 . DDIs, As for gefitinib, interactions are suspected with concomitant use of erlotinib with drugs increasing gastric pH. Co-administration of omeprazole (40 mg daily) reduced both erlotinib AUC and Cmax by 46% and 61%, respectively. Similarly, the concomitant administration of ranitidine resulted in a decrease in erlotinib exposure. A case report also suggested that pantoprazole could alter erlotinib exposure. Nevertheless, the clinically relevant interaction observed during high dose intravenous pantoprazole treatment was absent during oral treatment with a lower dose. Rifampicin in healthy volunteers produced a 67% decrease in erlotinib AUC [112]. Surprisingly, co-administration of fenofibrate in a patient with lung adenocarcinoma led to subtherapeutic erlotinib concentrations that were dramatically increased after fenofibrate withdrawal. Co-administration of sorafenib resulted in subtherapeutic erlotinib concentrations which decreased from day 7 to 21, whereas sorafenib exposure was unaffected. The mechanism of this interaction remains unknown. Erlotinib AUC and Cmax were both estimated to increase approximately 2-fold in presence of ketoconazole, a potent CYP3A4 inhibitor. Similarly, the initiation of aprepitant (a potent CYP3A4 inhibitor) in a patient with lung adenocarcinoma led to a 2-fold increase in erlotinib plasmatic concentrations. This drug interaction is particularly interesting since aprepitant has been proposed for the treatment of elortinib-induced pruritus. Co-administration with ciprofloxacin (an inhibitor of CYP1A2 and CYP3A4) significantly increased erlotinib AUC by 39%, while no statistically significant change in Cmax was observed. The clinical relevance of this increase has not been established. Different case reports suggest that caution should be required with CYP3A4 or CYP2C8 substrates such as simvastatin, phenytoin and warfarin [118–120]. No significant interactions were noted in vivo between erlotinib with: oxaliplatin/leucovorin/fluorouracil, irinotecan/leucovorin/fluorouracil, gemcitabine [EMEA] gemcitabine/cisplatin, bevacizumab, docetaxel, pemetrexed and temozolomide. In tumour patients treated with paclitaxel/carboplatin, concomitant administration of erlotinib led to a 10.6% increase in carboplatin AUC, which is probably not clinically relevant.
• #13: This chemopreventive effect is related to the high content of these foods in several phytochemicals with potent anticancer properties. Among these, polyphenols such as flavonoids are found at high levels in several fruits and vegetables.
• #14: Although various biological functions of apigenin have been demonstrated in many studies, its role in health promotion mainly depends on the intaking amount and bioavailability. Research Article The Effect of Apigenin on Pharmacokinetics of Imatinib and Its Metabolite N-Desmethyl Imatinib in Rats Xian-yun Liu,1 Tao Xu,2 Wan-shu Li,3 Jun Luo,2 Pei-wu Geng,2 Li Wang,2 Meng-ming Xia,2 Meng-chun Chen,2 Lei Yu,2 and Guo-xin Hu2 Hindawi Publishing Corporation BioMed Research International Volume 2013, Article ID 789184, 6 pages http://dx.doi.org/10.1155/2013/789184
• #16: The second phase of the optimization procedure involves studying the effect of mobile phase composition on the analytes' response. Different mobile phases composed of mixtures of different ratios of acetonitrile (30-90%), water, and formic acid (0.005-0.15%) were evaluated for the chromatographic elution of standard mixtures of NER, PEL, and DOM (IS). Initially, mobile phases of different ratios of acetonitrile (30-90%) and water, each with 0.1% formic acid, were tried. Experimental trials revealed that acetonitrile percentage of 60% or less resulted in distortion of NER peaks. Sharp and symmetric peaks of both drugs, along with DOM (IS) were obtained with acetonitrile percentage of 70%. However, higher acetonitrile percentage resulted in peak distortion including peak tailing (NER) and peak broadening (PEL). Also, increased response of PEL peaks was noticed at acetonitrile percentage of 60% or higher. In addition, an increase in the acetonitrile content in the mobile phase was associated with a slight increase in the retention time of the three compounds. Thus, 70% acetonitrile in the mobile phase produced best results regarding the runtime, peak response, and peak shape of NER, PEL and DOM peaks. The second phase of mobile phase optimization involved the effect of formic acid content (0.005-0.15%) in the mobile phase. Formic acid was found to be essential to get sharp peaks of both NER and PEL. It was also noticed that a decrease in the retention time of both NER and PEL was associated with an increase in the formic acid content in the mobile phase till 0.1 % above which some tailing was recorded for NER and PEL peaks. Best results were achieved with 0.1% formic acid content in the mobile phase. Final analysis was performed with a mobile phase consisting of acetonitrile: water, each with 0.1% formic acid, (70: 30, v/v) for the whole runtime of 1.5 min. DOM had a suitable retention and chromatographic behavior, compared with NER/PEL. Thus it was used as the IS in this study. Under these chromatographic conditions, sharp and symmetric peaks of all drugs were obtained (NER eluted at 0.59 ± 0.03 min, PEL at 0.57 ± 0.02 min, and DOM (IS) at 0.51 ± 0.020 min).
• #17: Different MS/MS parameters such as ESI source temperature, cone and capillary voltage, flow rate of desolvation gas, and desolvation temperature were optimized in order to obtain the highest intensity of the protonated precursor ions. It was observed that a source temperature of 150 oC and desolvation gas flow rate of 80 L/h resulted in the highest response of the protonated precursor ions. Also, an increase in the relative abundance of the precursor ions was associated with the increase in the cone voltage or capillary voltage till optimum values after which a remarkable decrease was noticed. On the other hand, the collision energy was optimized for maximum intensity of the product ions. The intensity of a particular fragment ion increased with increasing the collision gas energy till optimum values above which a decrease in its intensity was noticed. The optimized MS/MS conditions of the studied drugs were summarized in Table 1. Full scan product ion spectra of protonated precursor ions [M+H]+ for NER, PEL, and DOM were shown in Fig. 2. Precursor ions were selected at m/z 557.30 (NER), m/z 468.21 (PEL), and at m/z 426.27 (DOM) while the product ions were at m/z 112.05 (NER), m/z 395.22 (PEL), and at m/z 175.18 (DOM).
• #18: 2.4. Mass spectrometric conditions Electrospray ionization (EI) was operated in the positive ionization mode. Quantitation was performed using multiple reaction monitoring (MRM) of the transitions m/z 393 > 147 (DEX), m/z 260 > 149 (LND), and m/z 426 > 175 (DOM) being used as the internal standard (IS). To obtain optimum MS parameters, the collision energy, cone voltage, and capillary voltage were set at (32 eV, 62 V, 4 kV for DEX), (14 eV, 14 V, 3.5 kV for LND), and (27 eV, 50 V, 3 kV for DOM), respectively. Nitrogen was used as the desolvating gas at a ow rate of 800 L h1. Cone gas ow was adjusted at 150 L h1. Desolvation temperature of 400 C was applied whereas the source temperature was adjusted to 150 C. The MS analyzer parameters were as follows: LM1 and HM1 resolution of 2.8 and 14.5, respectively, for ion energy 1, and LM2 and HM2 resolution of 2.8 and 14.5, respectively, for ion energy 2. The dwell time of 0.0255 s was used.
• #19: Blank and spiked plasma samples were vortex-mixed for 5 min at 6000 rpm. The supernatant of each sample was separated to a glass tube and the residue was further washed with 0.5 mL volumes of methanol. The combined methanolic solutions obtained from the supernatants and the washings were further purified by passing onto C 18 Bond Elut cartridges used for SPE, previously preconditioned with 1.0 mL methanol followed by 1.0 mL ultrapure water. The retained drugs were then eluted with 0.5 mL methanol which was further evaporated to dryness under nitrogen using the nitrogen evaporator. The obtained residue was then reconstituted in 0.5 mL acetonitrile and volumes of 5 µL were injected into the UPLC-MS/MS system for analysis. Sample preparation is very important parameter in the development of bioanalytical techniques. To overcome the interfering effect of many endogenous components that could largely hinder the selective analysis, different sample preparation techniques are applied. They include protein precipitation (PPT), liquid-liquid extraction (LLE), and solid-phase extraction (SPE). Among which, SPE has been widely applied in LC-MS/MS analysis of many biological matrices. Its superior potential to minimize the ion suppression could be referred to its ability to eliminate most endogenous serum components [26-28]. Thus, SPE was applied for sample preparation in this study. Plasma samples were treated with methanol then the obtained clear supernatants were further purified using SPE. Initially, two SPE cartridges namely, Bond Elut C 18 (100 mg, 1 mL) and octyl C 8 (200 mg, 3 mL) were tested for their extraction efficiency using plasma samples spiked with both NER and PEL at the concentration level of 50 ng/mL. It was found that better peak shape was obtained using C 18 compared with C 8 cartridges since the latter resulted in a significant peak splitting of both NER and PEL peaks. SPE recovery of C18 cartridges was further evaluated by replicate analysis (n=6) of plasma samples spiked with NER and PEL at the QC levels 0.5, 5, 50, and 150 ng/mL. C 18 cartridges provided excellent recovery for both drugs (89.73-94.84%).
• #24: 2.7. Application to pharmacokinetic studies All experiments were performed as per the WHO regulations in Saudi Arabia with reference to ethical guidelines for experimental studies with animals. Wistar healthy male rats weighing 250 ± 30 g were provided by the animal house, Women Student-Medical studies & Sciences Sections, College of Pharmacy, King Saud University, Riyadh, Saudi Arabia. The rats were placed in cages kept at standard laboratory conditions; a well-ventilated room, a regular 12 h day–night cycle, an average temperature of 24–27°C, and a relative humidity of 40–60%. All the rats had free access to water while diet was prohibited for 12 h before conducting the experiment. The rats were acclimatized for 7 days to laboratory conditions before initiating the study. The animals were divided into four groups of five rats each. Suspensions of 30 mg/mL (NER), 10 mg/mL (PEL), and 100 mg/mL (API) were prepared by triturating an appropriate weight of each drug with aqueous methyl cellulose (0.5%, w/v). Separate volumes (0.25 mL) of the drugs suspensions were given to the treated animals orally using a gavage needle as follows; NER, 30 mg/kg (Group I), PEL, 10 mg/kg (Group II). Rats of groups III and IV were first separately given an oral dose of API (100 mg/kg). After a period of 30 min, the rats were subjected to an oral dose of NER, 30 mg/kg (Group III), or PEL, 10 mg/kg (Group IV). Blood samples (0.3 mL) were collected from the retro-orbital sinus of each rat into heparinized tubes following drug administration at different time intervals; 0 (prior to dosing), 0.5, 1, 2, 3, 4, 6, 10, and 24 h. All samples were immediately centrifuged for 30 min using 4,500 rpm at 4oC. The resulting plasma samples were kept frozen at -20 °C until analysis. Volumes of 50 µL of each plasma sample were separately spiked with a constant volume of 100 µL of DOM, IS (5 ng/mL), then completed to a final volume of 1 mL with methanol. All samples were then treated exactly as described under sample preparation. The found concentrations were calculated, using the corresponding matrix-based calibration graph, by relating the peak area ratio of each drug to that of the IS.
• #26: 3.5. Application to pharmacokinetic studies Food-drug interactions could be widely classified into physicochemical, PK, and pharmacodynamics interactions. Among which, PK interactions is the most common. Despite the widespread use of API, as antioxidant and anticancer flavonoid, among cancerous patients receiving NER/PEL therapy, no studies have been found in the literature studying their PK interactions. Thus, the applicability of the validated UPLC-MS/MS method developed in this work was extended to study the possibility of pharmacokinetic interaction that could be encountered following the concomitant administration of NER/PEL with API. NER is clinically given in the oral dose of 240 mg daily. While for PEL, a daily oral dose of 75 mg is established for cancer treatment. Thus the design of this study involved the treatment of two groups of Wistar rats with NER (30 mg/kg), group I, or PEL (10 mg/kg), group II. In addition, for the purpose of studying the possibility of PK interactions with API, further two groups of Wistar rats were administered combinations of API (100 mg/kg) with either NER (30 mg/kg), group III, or PEL (10 mg/kg), group IV. As per the experimental section, blood samples were withdrawn from each group separately at different time intervals and analyzed for NER and PEL content. Fig. 3 shows representative MRM chromatograms of rat plasma samples withdrawn 4 h after the concomitant administration of NER/PEL with API. Fig. 4 shows the mean drug plasma concentration time profiles reported for each of NER/PEL combination with API, compared with their single administration. Different PK parameters were calculated for both drugs as shown in Table 6. They include the area under the curve (AUC), maximum plasma concentration (Cmax), time to reach the maximum plasma concentration (tmax), and half-life (t1/2). Although there was no significant change in the tmax of NER, a significant increase in the Cmax (56%) and AUC (58%) was reported following its co-administration with API suggesting the role of API on NER clearance. Also, an increase in the Cmax (16%) and AUC (53%), along with an increase in the tmax and t1/2 was noticed with PEL combination with API, compared with its single administration. From these results, the effect of API on the PK of both NER and PEL was considered significant. It is clearly indicated that API slowed down the metabolism of both drugs. This could be attributed to the fact that both NER and PEL are mainly metabolized by CYP3A4 enzymes and like other TKIs they are substrates of P-gp efflux transporters [30]. Thus API-induced increased bioavailability of NER/PEL could be attributed to the inhibitory effect of API on both CYP3A4 enzymes as well as P-gp efflux proteins. Because this type of PK interactions could lead to increased systematic drug exposure, excessive side effects could be encountered with this combination. This is extremely important since NER is characterized by diarrhea as the dose limiting toxicity. Also PEL suffers from gastrointestinal and cutaneous side effects that could lead to drug withdrawal in many clinical studies [2]. Although this study was conducted in rats and not on humans and that differences in their PK pattern could exist, the possibility of occurrence of PK interactions between NER/PEL and API could exist when shifting to clinical studies. Thus, TDM of both drugs is significantly important in cancerous patients receiving NER/PEL with API.
• #27: This superior sensitivity permits the determination of very low drug concentrations, an important issue in terminal phase elimination during PK studies. Also, smaller sample volume is preferable where large volumes of plasma samples are not available in some clinical cases, e.g. children and elderly people. In addition, short analysis time is necessary for high throughput bioanalysis.
• #28: This superior sensitivity permits the determination of very low drug concentrations, an important issue in terminal phase elimination during PK studies. Also, smaller sample volume is preferable where large volumes of plasma samples are not available in some clinical cases, e.g. children and elderly people. In addition, short analysis time is necessary for high throughput bioanalysis.