The natural history of CML has been transformed in recent years by the introduction of Glivec[superscript TM] (imatinib mesylate), an ABL kinase inhibitor, which provides the new treatment paradigm for chronic phase CML. While the majority of patients with CP-CML respond very well to imatinib, there are approximately 15% of patients who fail to respond, or respond suboptimally. While the major cause of secondary imatinib resistance can be attributable to kinase domain mutations, the underlying cause of primary resistance is yet to be elucidated. Utilizing the phosphorylation of the adaptor protein Crkl, an immediate downstream partner of BCRABL, as a surrogate measure of BCR-ABL kinase activity, a large interpatient variation in the degree of imatinib induced kinase inhibition achieved in-vitro, was observed in previously untreated CP-CML patients. The observed in-vitro sensitivity was a good predictor of molecular response in patients treated with 600mg imatinib as front line therapy. Furthermore, analysis of the in-vivo reduction in p-Crkl mediated measured in blood cells in response to imatinib over the first 28 days of therapy, revealed that patients with higher % reductions respond significantly better over a two year period, than those with lower % reductions. Using 14-C labelled imatinib, it was demonstrated that this intrinsic sensitivity correlated to the amount of drug which was retained within the target haemopoietic cell, and furthermore, that a critical determinant of the active influx of imatinib, was the functional activity of the human organic cation transporter -1 (OCT-1), as determined by a prazosin (potent inhibitor of OCT-1) inhibition assay. Patients with high OCT-1 Activity had superior molecular responses when compared to those with low OCT-1 Activity, but in those patients who could tolerate increased imatinib dose, these inferior responses could be largely overcome. In contrast, Nilotinib, a more potent second generation tyrosine kinase inhibitor, is not dependent on OCT-1 for influx, making it a possible treatment choice for patients with low OCT-1 Activity. Both imatinib and nilotinib interact with the efflux transporters ABCB1, and ABCG2. In combination studies imatinib results in a significantly increased intracellular concentration of nilotinib, most likely through interaction with these efflux transporters. Furthermore, commonly used therapies such as proton pump inhibitors also interact with ABCB1 and ABCG2, and demonstrable changes in intracellular drug concentrations were observed in-vitro with concomitant administration of these agents and imatinib or nilotinib at clinically relevant concentrations. In conclusion, these data demonstrate that the degree of kinase inhibition mediated in-vitro and in-vivo by imatinib, is a critical determinant of subsequent molecular response. This intrinsic sensitivity to imatinib induced kinase inhibition is related to the activity of the OCT-1 protein. This protein is not involved in the transport of nilotinib, suggesting it as a possible treatment alternative in those patients with low OCT-1 Activity. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1319077 / Thesis (Ph.D.) -- University of Adelaide, School of Medicine, 2008

O carcinoma adrenocortical (ACC) é um tumor maligno raro. O objetivo foi testar a ação de drogas antitumorais na linhagem H295R, em cultura 2D e 3D, analisadas por MTS, ensaios multiparamétricos, e microscopia confocal. Em monocamada (2D), as drogas tiveram maior efeito quando utilizadas com o mitotano 10 mM, sendo: everolimus 10 mM (50±0,02% p &#8804 0.001), imatinib (10 mM 52±0.01% p &#8804 0.001), sunitinib 5 mM (47±0.02% p &#8804 0.001), e nilotinib 5 mM (59±0,03% p &#8804 0.001), com evidência de apoptose. Nos esferoides (3D) foi necessário mitotano 30 M com everolimus 10 mM para se obter diminuição de 32±0.02% p &#8804 0.001 na viabilidade das células, e com nilotinib 10 mM para redução de 57±0.03% p &#8804 0.001, com evidência de necrose e apoptose. Em resumo, os dados sugerem que os esferoides são mais resistentes aos tratamentos, como ocorre com tumores in vivo, e podem representar uma importante abordagem para estudos de ACC. O nilotinib foi o que induziu as melhores respostas, tanto no modelo em 2D quanto 3D, resultados que se apresentam promissores para o tratamento dos carcinomas adrenocorticais. / Adrenocortical carcinoma (ACC) is a rare malignant tumor. The objective was to test the antitumor drugs action in the H295R cell line, in 2D and 3D culture system, by using MTS, multiparameter assay (High Content Screening) and confocal microscopy. In monolayer, all drugs were more effective in combination with mitotane 10 mM: everolimus 10 mM (50±0.02%), 10 mM imatinib (52±0.01%), 5 mM sunitinib (47±0.02%), and 5 mM nilotinib (59±0.03%). The spheroids required mitotano 30 mM with everolimus 10 mM to decrease cell viability (32±0.02% p &#8804 0.001); and with 10 mM nilotinib to inhibit cell viability in 57±0.03% (p &#8804 0.001), with induction of apoptosis and necrosis. In summary, the spheroids were more resistant to treatment and may represent an important approach for studies of ACC. Nilotinib was the tyrosine kinase inhibitor that, either alone or in combination with mitotane, induced higher cytotoxicity, in both 2D and 3D cell cultures, showing promising results for the treatment of adrenocortical carcinoma, as well as for the studies of its mechanism of action.

Imatinib mesylate (imatinib) represents a potent molecularly targeted therapy against the oncogenic tyrosine kinase, BCR-ABL. Although imatinib has shown considerable efficacy against chronic myeloid leukemia (CML), displaying high rates of complete hematological and complete cytogenetic responses, treatment with imatinib is not curative and overtime advanced-stage CML patients often become refractory to further treatment. Acquired resistance to imatinib has been associated with mutations within the kinase domain of BCR-ABL, BCR-ABL gene amplification, leukemic stem cell quiescence as well as over-expression of the multidrug resistance (MDR1) gene. However, in vitro resistance models often fail to consider the role of the tumor microenvironment in the emergence of the imatinib-resistant phenotype. The bone marrow is the predominant microenvironment of CML and is a rich source of both soluble factors and extracellular matrixes, which may influence drug response. To address the influence of the bone marrow microenvironment on imatinib sensitivity, we utilized an in vitro co-culture bone marrow stroma model. Using a transwell system, we demonstrated that soluble factors secreted by the human bone marrow stroma cell line, HS-5, were sufficient to cause resistance to apoptosis induced by imatinib in CML cell lines. We subsequently determined that culturing CML cells in HS-5-derived conditioned media (CM) inhibits apoptosis induced by imatinib and other second generation BCR-ABL inhibitors. These data suggest that more potent BCR-ABL inhibitors will not overcome resistance associated with the bone marrow microenvironment. Additionally, we determined that CM increases the clonogenic survival of CML cells following treatment with imatinib. HS-5 cells are reported to express several cytokines and growth factors known to activate signal transducer and activator of transcription 3 (STAT3). Given its crucial role in the survival of hematopoietic cells, we asked whether, 1) CM derived from HS-5 cells can activate STAT3 in CML cells and 2) does activation of STAT3 confer resistance to BCR-ABL inhibitors. We demonstrated that exposure of the CML cell lines, K562 and KU812, to CM caused an increase in phospho-Tyr STAT3, while no increases in phospho-Tyr STAT5 were noted. Moreover, resistance was associated with increased levels of the STAT3 target genes, Bcl-xl, Mcl-1 and survivin. Furthermore, reducing STAT3 levels with siRNA sensitized K562 cells cultured in CM to imatinib-induced cell death (p<0.05, Student’s t-test). Importantly, STAT3 dependency was specific for cells grown in CM, as reducing STAT3 levels in regular growth conditions had no effect on imatinib sensitivity. Together, these data support a novel mechanism of BCR-ABL-independent imatinib resistance and provide preclinical rationale for using STAT3 inhibitors to increase the efficacy of imatinib within the context of the bone marrow microenvironment.

Bakgrund: Vid kronisk myeolid leukemi (KML) överproducerar blodstamceller omogna granulocyter som kan öka risken för infektioner, anemi och lätta blödningar. Ifall sjukdomen inte åtgärdas i tidigt skede så kan cancercellerna konkrurera ut friska blodceller vilket kan leda till ett livshotande tillstånd. KML drabbar främst vuxna över 55 år. Orsaken till KML är nästan alltid en somatisk mutation i blodcellerna som leder till förändring i karyotypen, den abnormala kromosomen kallas för Philadelphia kromosomen. De olika behandlingalternativ som finns mot KML inkluderar kemoterapi (låg dos/hög dos med stamcellstransplantation), interferon alfa, donator lymfocytinfusion och tyrosinkinasinhibitor (TKI). TKI är standardbehandling vid KML och TKIs inlkluderar imatinib, dasatinib, nilotinib, bosutinib och ponatinib. Studier har visat att TKI administrerat på friska råttor och möss har en teratogen effekt. Syfte: Syftet med arbetet var att utvärdera risker och fördelar vid behandling av kronisk myeloid leukemi med tyrosinkinasinhibitor i samband med graviditet. Metod: Arbetet är en litteraturstudie baserat på 13 caserapporter därav 4 studier om imatinib, 4 om nilotinib, 4 om dasatinib och 1 studie om imatinib, nilotinib och dasatinib. Bosutinib och ponatinib exkluderades eftersom det fanns inga studier om exponering av dessa läkemedel under graviditet. Resultat: Från studierna om imatinib var det totalt 23 av 163 patienter som fick missfall och 14 av 90 födsel slutade med foster abnormiteter. Totalt hade 49 fall rapporterats om exponering med nilotinib under graviditet därav 46 fall resulterade i normal födsel och 3 spädbarn fick fetala abnormiteter som resulterade till dödlighet. Av de fyra fall som rapporterades om Dasatinib var det ett som slutade med abort efter vecka 17 på grund av fostrets dåliga perinatala prognos. Alla patienter behandlades inte med TKIs under graviditeten. Vissa patienter hade kombinationer av läkemedel. Slutsats: Det finns fortfarande inte bekräftade risker med TKI behandling i samband med graviditet då statistiskt underlag saknas. Fördelen med att behandlas med TKI under graviditet är att risken för återfall och försämrad sjukdomprognos förminskas. Läkaren ska alltid diskutera med patienten om eventuella risker och möjligheter. Behandling för varje patient individualiseras utifrån patienens önskemål. / Background Chronic myeloid leukemia (CML) is a type of leukemia that affects bone marrow and blood cells. In CML, the blood stem cells produce an excessive number of immature granulocytes which leads to a high count of white blood cells in patients. Consequently, the risk of acquiring infections, anemia and hemorrhage, is increased. If not successfully treated the leukemia cells will eventually crowd out platelets and healthy blood cells and ultimately lead to death. Generally, CML occurs in adults aged 55 years or older. The cause of CML is in most cases a somatic mutation that is referred to as the Philadelphia chromosome. There are various treatments for CML, I.e., chemotherapy, interferons-alpha, high-dose chemotherapy combined with a stem cell transplantation, donor lymphocyte infusion (DLI), and tyrosine kinase inhibitors (TKI). TKI are the standard treatment for CML. There are several types of TKI, namely: Imatinib, nasatinib, nilotinib, bosutinib and ponatinib. Although considered the most effective treatment for CML, there are several animal studies indicating that TKI has a teratogenic effect. Purpose The objective of this study was to evaluate the risks and benefits of TKI treatment in connection with pregnancy. Method  A literature review based on 13 case reports, among them four reports about imatinib, four reports about nilotinib, four reports about dasatinib and one report describing several patients treated with imatinib, nilotinib and dasatinib. Studies about bosutinib and ponatinib are excluded from this study due to the lack of scientific research regarding their impact on pregnant women. Result The studies about Imatinib showed that 23 of 163 patients had miscarriage. Furthermore, 14 of the 90 live births resulted in foster abnormalities. There were totally 49 cases in which Nilotinib was administered to pregnant women. In 46 cases the patients gave birth to healthy children. However, in three cases the fetuses were abnormal and in one of these cases the child was stillborn. Moreover, there were four case studies in which the patients were treated with dasatinib. In one case the treatment lead to an abortion after week 17 due do the fetus poor perinatal prognosis. All patients were not treated with TKIs during pregnancy. Some patients had combinations of drugs.  Conclusion  There are still no confirmed risks with TKI treatment in connection with pregnancy because statistical evidence is missing. The benefit of being treated with TKI during pregnancy is that the risk of relapse and impaired disease prognosis is reduced. The doctor should always discuss with the patient about risks and opportunities. Treatment for each patiens is individualized based on the patients wishes.

京都大学 / 0048 / 新制・課程博士 / 博士(医科学) / 甲第20811号 / 医科博第82号 / 新制||医科||6(附属図書館) / 京都大学大学院医学研究科医科学専攻 / (主査)教授 長船 健二, 教授 妻木 範行, 教授 村井 俊哉 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

Orientador: Katia Borgia Barbosa Pagnano / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Ciências Médicas / Made available in DSpace on 2018-08-26T19:42:43Z (GMT). No. of bitstreams: 1 Ribeiro_BeatrizFelicio_M.pdf: 2588401 bytes, checksum: 356f862f97d6467c69db0ac9b13f28d5 (MD5) Previous issue date: 2015 / Resumo: A Leucemia Mielóide Crônica (LMC) é uma neoplasia mieloproliferativa crônica caracterizada pela presença do cromossomo Filadélfia (Ph) e produção da fusão proteica BCR-ABL que possui atividade tirosina quinase. O tratamento da LMC é realizado com inibidores de tirosina quinase (TKIs) e apesar das altas taxas de respostas obtidas com imatinibe, alguns pacientes são resistentes ou intolerantes ao tratamento, sendo necessário a troca para um TKI de segunda geração (nilotinibe ou dasatinibe). O monitoramento das respostas obtidas ao longo do tratamento permite identificar os pacientes que estão em um "estado seguro" (resposta ótima) e os que podem falhar ao tratamento. Os mecanismos de resistência ao tratamento são multifatoriais e a identificação desses mecanismos pode contribuir para o desenvolvimento de novas estratégias para o tratamento dos casos resistentes. Em um trabalho anterior do nosso grupo foram identificados diversos genes e RNAs longos não codificantes diferencialmente expressos em pacientes responsivos e não responsivos ao dasatinibe, entre eles os genes ABCF2, ALOX15B, PAWR, ncFOXO3A, ncMYLIP e ncSLC44A2. O objetivo desse trabalho foi avaliar a resposta molecular em pacientes com LMC em uso de inibidores de tirosina quinase de segunda geração (dasatinibe ou nilotinibe) após falha ou intolerância a um ou dois TKIs e avaliar a expressão dos genes ABCF2, ALOX15B, PAWR, ncFOXO3A, ncMYLIP e ncSLC44A2 em pacientes responsivos e resistentes ao dasatinibe. A metodologia utilizada para avaliação dos níveis de trancritos BCR-ABL e da expressão gênica foi o PCR quantitativo em tempo real. A pesquisa de mutações no domínio quinase do BCR-ABL foi realizada nos casos resistentes, através da técnica de sequenciamento direto. Setenta e um pacientes tratados com dasatinibe ou nilotinibe após falha ou intolerância ao imatinibe foram avaliados quanto à resposta molecular. Sessenta e sete porcento, 43% e 33% dos pacientes em fase crônica (FC), acelerada (FA) e crise blástica (CB) obtiveram resposta molecular maior (RMM), respectivamente, ao longo do tratamento. Os pacientes com respostas moleculares precoces (transcritos BCR-ABL <10% aos 3 meses e <1% aos 6 meses) apresentaram maiores SLP e SLE do que os casos que não alcançaram esses níveis de transcritos BCR-ABL aos 3 e/ou aos 6 meses. A avaliação molecular aos 3 meses e aos 6 meses permitiu a melhor identificação dos pacientes com pior prognóstico. Foram também avaliados 25 pacientes tratados com dasatinibe/nilotinibe após falha ou intolerância a dois TKIs. RMM foi obtida em somente 24% dos casos (em FC, um paciente em FA). As taxas de SG e SLP em 5 anos para pacientes em FC foram de 94% e 94%, respectivamente. Poucos pacientes alcançam respostas e essas respostas não são duráveis. Embora seja uma opção para pacientes não elegíveis ao TMO, é necessário o desenvolvimento de um tratamento mais eficaz para esses pacientes. Para avaliação da expressão dos genes ABCF2, ALOX15B, PAWR, ncFOXO3A, ncMYLIP e ncSLC44A2 foram utilizadas amostras de 9 pacientes ao diagnóstico (sem tratamento prévio), 39 pacientes tratados com dasatinibe (25 responsivos com RCC e 14 resistentes) e 13 doadores saudáves. Não houve diferença de expressão do gene ncSLC44A2 entre os grupos avaliados. Os genes ALOX15B e ncMYLIP estavam hipoexpressos em pacientes com LMC ao diagnóstico em relação aos pacientes com LMC tratados com dasatinibe e ao grupo controle. O gene ncFOXO3A apresentou expressão diminuída em pacientes com LMC ao diagnóstico em relação aos pacientes tratados com dasatinibe. O genes ABCF2 e PAWR estavam hipoexpressos em pacientes ao diagnóstico e nos pacientes tratados com dasatinibe em relação ao grupo controle. Além disso, o gene PAWR estava pouco expresso em pacientes resistentes ao dasatinibe em relação aos pacientes responsivos. Portanto, os genes ABCF2, ALOX15B, PAWR, ncMYLIP e ncFOXO3A foram encontrados com expressão alterada nos grupos estudados e podem estar associados a mecanismos importantes relacionados ao desenvolvimento e resistência da LMC, o que deve ser elucidado em estudos prospectivos / Abstract: Chronic myeloid leukemia (CML) is a chronic myeloproliferative neoplasm characterized by the presence of Philadelphia chromosome (Ph) and production of BCR-ABL fusion protein that has tyrosine kinase activity. Currently, the treatment of CML is accomplished with tyrosine kinase inhibitors (TKIs). Despite the high rates of responses obtained with imatinib, some patients are resistant or intolerant to treatment and need to switch to second generation TKIs (dasatinib or nilotinib). Monitoring responses during treatment allows the identification of patients who are in a "safe haven" (optimal response) and patients who may fail to treatment. Mechanisms of resistance to treatment are multifactorial and identification of these mechanisms may contribute to the development of new strategies for treatment of resistant cases. In a previous report of our group were identified several genes and long non-coding RNAs differentially expressed in CML patients responders and non-responders to dasatinib, including ABCF2, ALOX15B, PAWR, ncFOXO3A, ncMYLIP and ncSLC44A2 genes. The aim of this study was to evaluate molecular responses in CML patients treated with second generation TKIs (dasatinib or nilotinib) after failure or intolerance to one or two TKIs and to evaluate the expression of ABCF2, ALOX15B, PAWR, ncFOXO3A, ncMYLIP and ncSLC44A2 genes in patients responsive and resistant to dasatinib. The methodology used to evaluate BCR-ABL transcript leves and the gene expression was quantitative real time PCR. BCR-ABL kinase domain mutations analysis was performed in resistant cases by direct sequencing. Seventy-one patients treated with dasatinib/nilotinib after failure or intolerance with imatinib were evaluated according to molecular responses. Sixty-seven percent, 43% and 37% of chronic phase (CP), accelerated phase (AP) and blast crisis (BC) CML patients achieved major molecular response (MMR), respectively, during treatment. Patients with early molecular responses (BCR-ABL1<10% at 3 months and <1% at 6 months) had superior PFS and EFS than patients that not achieved these landmarks. The evaluation at 3 and 6 months allows better identication of patients with worse prognosis. We analyzed molecular responses in 25 patients treated with dasatinib/nilotinib after failure or intolerance with two TKIs. MMR was achieved in 24% of cases (all in CP, one in AP). Five-year OS and PFS rates for CP-CML patients were 94% and 94%, respectively. Few patients achieved responses and these responses are not durable. Although, dasatinib/nilotinib had been options for patients not elegible for bone morrow transplantation, its necessary the development of a treatment more effective to these patients. To evaluate the expression of ABCF2, ALOX15B, PAWR, ncFOXO3A, ncMYLIP e ncSLC44A2 genes was used samples of 9 patients newly diagnosed (without treatment), 39 patients treated with dasatinib (25 responsives with CCyR and 14 resistant) and 13 healthy donors. There¿s no difference of ncSLC44A2 gene expression between the groups analized. ALOX15B and ncMYLIP genes were down-regulated in CML patients newly diagnosed in comparison with CML patients treated with dasatinib and control group. ncFOXO3A gene presented decreased expression in CML patients at diagnosis in comparison with patients treated with dasatinib. ABCF2 and PAWR genes were down-regulated in CMl patients newly diagnosed and in CML patients treated with dasatinib in comparison with control group. Moreover, PAWR gene was down-regulated in CML patient¿s resistants to dasatinib in comparison with responsives. ABCF2, ALOX15B, PAWR, ncMYLIP and ncFOXO3A were found with altered expression between the groups evaluated and may be associated with mechanisms related to the development and resistance of CML, which should be elucidated in prospective studies / Mestrado / Clinica Medica / Mestra em Ciências

Parkinsons sjukdom (PD) är ett tillstånd som ger en försvårad och försämrad livskvalité. I dagsläget finns det endast symtomatiska läkemedel men ingen bot med vilken sjukdomen upphör eller som bromsar förloppet. Pågående forskningsarbete utgår bland annat från att ta fram nya läkemedel men även också undersöka om redan befintliga läkemedel går att använda som behandling av PD. Många av de redan befintliga läkemedlen som testas är de som har förmågan att påverka proteinet α-synuklein (α-syn) och dess aggregering, som visats vara en central orsak till uppkomsten av PD. I föreliggande litteraturstudie undersöktes på vilket sätt en del läkemedel vars indikation är PD och även andra sjukdomstillstånd såsom astma, påverkar (ex. påskyndar eller inhiberar) in-vitro aggregering av α-syn. Därutöver genomfördes en detaljerad analys av de utvalda läkemedlen och deras effekt på α-syn aggregering utifrån deras kemiska egenskaper med avseende på löslighet (hydrofila, lipofila, amfifila) och inbindning till α-syn. Här kunde det visas att aggregering av α-syn inhiberades av alla utvalda läkemedel förutom dexametason, som istället påskyndade aggregeringskinetiken för proteinet. Dessutom uppvisade fasudil, ceftriaxon, dopamin, entakapon och tolkapon inbindning till delar av (hydrofila, hydrofoba eller amfifila) vilka delade samma fysikalkemiska egenskaper som α-syn. Därtill uppvisade utvalda läkemedel med till viss del plana strukturer (ex. aromatiska ringar) direkt inbindning till α-syn, vilka också rapporterats ha en något högre grad av transport över blod-hjärnbarriären, dock måste dessa fynd mer noggrant undersökas. Sammanfattningsvis visade alla utvalda läkemedel förutom dexametason anti-aggregeringsegenskaper (hämmande) mot α-syn genom att antingen indirekt eller direkt binda till proteinet och därmed hindra proteinet från att börja binda till sig själv. Mer studier måste genomföras för att studera effekten av läkemedelsexponering på α-syn för att identifiera viktiga segment av proteinet som kan utgöra läkemedelsmål för inhibering av α-syn aggregering. / Parkinson's disease (PD) is a condition that leads to an aggravated and worsened quality of life. At present, there are only symptomatic drugs for PD but no cure that eradicate the disease nor halter the disease progression have been found. Current research is being carried out to develop new drugs, but efforts also investigate whether existing drugs can be used as treatment for PD. Many of the already existing drugs being tested are those that have the ability to interact with a protein called α-synuclein (α-syn), that has been implicated to be a major player for onset of PD. In the present literature study, it was investigated in what way some drugs, whose indication is PD but also other diseases such as asthma, affect (i.e. propagate or inhibit) the in-vitro aggregation kinetics of αsyn. Additionally, a detailed analysis of the investigated drugs and their effect on the aggregation pathway was made to characterize common chemical features of the selected drugs based upon choice of solvents and binding to α-syn. Here, it could be shown that aggregation of α-syn is inhibited upon exposure to all selected drugs except dexametason which instead propagated aggregation of α-syn. In addition, fasudil, ceftriaxone, dopamine, entacapone and tolcapone was found to bind to parts (hydrophilic, hydrophobic or amphiphilic) of α-syn similar to their solubility features. Moreover, the selected drugs that were found to bind to α-syn seemed to exhibit planar in structure (i.e. aromatic rings) and also be associated to pass the blood-brain barrier to a greater extent, however these findings need to be more thoroughly investigated. In summary, all drugs but dexametason were shown to inhibit aggregation of α-syn invitro by either indirectly or directly affecting the aggregation of the protein. Further investigations need to be carried out to study the effect of drug exposure on α-syn aggregation in order to propose key segments of α-syn that can act as drug targets for inhibition of protein aggregation.

Chronic Myelogenous Leukemia (CML) is a blood cancer that arises when hematopoietic cells acquire an abnormal protein known as BCR-ABL. Current therapies for CML include drugs that inhibit BCR-ABL. However, these drugs only suppress the disease and do not cure it. One reason is that BCR-ABL drugs fail to kill the primitive population of CML cells, referred to as leukemia stem cells (LSCs), which are responsible for initiating and propagating CML. Since LSCs are not killed, the cancer is not cured and many affected patients eventually relapse. Recent studies suggest that LSCs are protected from current therapies by the bone marrow micro-environment where they reside. There, cytokine signaling molecules are present, which mediate processes that protect LSCs from BCR-ABL drugs. The stem cell factor (SCF) is one of these signaling molecules. It activates the receptor c-Kit located on the surface of LSCs, and this activation in turn allows proliferating LSCs to resist BCR-ABL drugs, even without prior exposure to these drugs, i.e., innate resistance is observed. In this thesis, the mechanism of this innate resistance is investigated, so that a suitable treatment strategy can be developed. To this end, a co-agent approach based on synthetic antibodies (sABs) is proposed to inhibit the receptor c-Kit, with the goal of disrupting its activation by the ligand SCF. This disruption should in turn block the SCF-mediated innate resistance, thus potentially restoring BCR-ABL drug apoptotic activity. The method for this disruption involves targeting the c-Kit structural susceptibility. Specifically, the sABs are designed via antibody phage display technology to target the D1–D2–D3 domains representing the SCF binding sites, hence preventing downstream pathway activation. The hypothesis is that, by blocking the SCF-mediated innate resistance, a suitable combination of such an sAB co-agent and a BCR-ABL drug should be conducive to suppressing LSCs, thereby providing a potential means to improve CML treatment. In addition, to assess the performance of the proposed treatment strategy, a set of in vitro tests is conducted, focusing on performance behaviors such as cell binding, cell death, and the progenitor inhibition. The experimental results support the hypothesis that the proposed combinatorial strategy is indeed a promising approach to mitigate the innate resistance, thus restoring BCR-ABL drug apoptotic activity.