Improving Treatment Outcomes in Chronic Myeloid Leukaemia Patients Using Imatinib and Artesunate Combination Therapy

Improving treatment outcomes in chronic myeloid leukaemia patients using Imatinib and Artesunate combination therapy.

Statement of Research Problem:

Imatinib is a first-line tyrosine kinase inhibitor (TKI) in the management of CML patients. At present, over one thousand Nigerians with CML are accessing free imatinib on the Glivec International Patient Assistance Program (GIPAP) platform at the Obafemi Awolowo University Teaching Hospital (OAUTH), Ile-Ife, Nigeria. This is the one of the two centres providing this service in the country and has been providing this service since 2003. However, only 40% of the patients had optimal clinical response while the rest had suboptimal response or treatment failure (Oyekunle et al., 2015). The high cost of alternative TKIs and/or stem cell transplantation hugely limits the treatment options available for Nigerian CML patients. Therefore, there is a strong need for an alternative therapeutic option that could optimize the management and clinical outcomes of CML in Nigeria and other resource-challenged countries.

Conceptual Framework of the Study:

This study explores drug repurposing for artesunate by investigating its anti-neoplastic effect in CML patients. Artesunate is a first-line antimalarial that has also demonstrated anti-leukemic activity in cell lines and murine models. Artesunate will be combined with imatinib and the synergy will be explored based on the multi-dimensional synergy of combination theory as described by Wooten (Wooten et al., 2019). The focus will be to evaluate the synergistic potency and synergistic efficacy of the combination. Synergistic potency is the amount of the change in drug potency, owing to the presence of another drug while synergistic efficacy is the percentage change in the maximal efficacy of the combination compared to the most efficacious single agent (Wooten et al., 2019). In this study, we will evaluate the pharmacokinetic interaction between artesunate and imatinib, and also determine the safety and efficacy of the combination, and the corresponding positive clinical outcomes in suboptimal CML patients. This approach has the potential to accelerate the translatability and reproducibility of this drug-synergy study by bridging the gap between the positive clinical outcome potential of the drug combination and the complexity of the study design.

Brief background:

CML is a clonal disease of the pluripotential haemopoietic stem cells, caused by a reciprocal translocation between chromosomes 9 and 22 with resultant formation of BCR-ABL1 chimeric gene and oncoprotein with constitutive tyrosine kinase activity. Through constitutive stimulation of multiple signal transduction pathways, this tyrosine kinase leads to neoplastic myeloid lineage expansion, primarily the granulocytic series but also megakaryocytic and only rarely, erythroid cells. Imatinib, is the first-line therapy for the management of Nigerian CML patients, which is consistent with the 2020 British Society of Haematology guidelines on the management of CML (Smith et al., 2020). Since 1998, when imatinib mesylate was first introduced, the treatment of CML has gained radical improvement with better outcome (Schmidli et al., 2005). Imatinib is available free of charge to patients in resource-limited countries such as Nigeria under the Glivec International Patient Assistance Program (GIPAP). A major limiting factor with this drug however, is the development of resistance which makes long-term disease-free remission difficult in some patients. The proportion of patients who achieved clinical cum molecular response after one year of standard dose imatinib daily ranged from 18% to 58% globally. In Nigeria, only 39.4% of CML patients on imatinib achieved major molecular response at ≥ 18 months of therapy while 25% of patients had imatinib-resistance from BCR-ABL1 kinase domain mutations which explained the cause of unsatisfactory response in this category of patients (Oyekunle et al., 2010). Lewandowski and colleagues (2009) also found twelve BCR-ABL mutations in 11 of 92 CML patients causing resistance to imatinib of which 40% were primary mutations while the rest 10.3% were secondary ones (Lewandowski et al., 2016).

Several alternative mechanisms aimed at overcoming imatinib resistance in CML patients have been explored. These include dose escalation of the drug or switching the patient to a second or third-line TKIs. The use of combinations of TKI and interferon [IFN] or pegylated interferon, omacetaxine mepussecinate have also been explored while allogeneic stem cell transplantation following failure of the novel TKIs has also been suggested to overcome the resistance. However, in a resource-limited setting, these options are not easily obtainable due to cost. The need therefore becomes inevitable to continuously search for an affordable alternative, which artesunate potentially presents.

Treatment milestones in Chronic Myeloid Leukaemia:

Mutations in the kinase domain of BCR-ABL are often responsible for resistance to imatinib. However, it is not necessary to request for mutation screening on a routine basis unless there is an indication for a loss of response (Sherbenou et al., 2007). The first therapeutic milestone is based on the evaluation after 3 months of therapy. It is expected that a complete haematologic response (CHR) is achieved at this time for an optimal response (Morotti et al., 2015). A partial haematological response (PHR) is considered a sub-optimal response according to the European Laeukaemia Net (ELN) recommendations (Hehlmann, 2020).

Artesunate use in Chronic Myeloid Leukaemia:

Artesunate is a semi-synthetic artemisinin compound and has been established to be the first-line treatment for malaria (Raffetin et al., 2018). However, it has been reported to possess anti-neoplastic effects either singly or in synergy with established anti-neoplastic drugs (Kumar et al., 2017). The mechanism of action is believed to be majorly due to endoperoxide-induced cytotoxicity via generation of reactive oxygen species when heam or ferrous iron activates the endoperoxide moiety of the drug, this effects toxicity to tumour cells via pathways involving growth arrest, reduced angiogenesis, DNA damage, and very importantly, apoptosis. There is however some evidence that artesunate possibly elicits its actions via multiple pathways including the regulation of key factors such as nuclear factor-kappa B [NFκ-B], BMI-1 and hypoxia-inducible factor-1ɑ pre-clinical study, using animal model of Xeno transplanted CML cells showed significant response to artesunate (Kim et al., 2015). Evidence of antitumor growth effect of this drug against urinary bladder and colorectal cancers has been demonstrated. The selective toxicity of artesunate to tumour cells is partly explained by reduced levels of antioxidant enzymes [e.g. catalase, glutathione peroxidase, superoxide dismutase] in these tumour cells (Krishna et al., 2015). Artesunate may also express toxicity towards some specific tumour proteins or biomarkers. Eling and co-researchers demonstrated this when they showed that artesunate selectively had high toxicity towards pancreatic ductal adenocarcinoma cells expressing KRas oncogene, but did not affect non-neoplastic human pancreatic ductal epithelial cells.

Artesunate at 200mg (2.2 - 3.9 mg/kg/day) for up to four weeks has been used as a continuous daily oral dose in colorectal and breast cancer patients without any significant toxicity. This dose was established to be safe and well tolerated over a four weeks period and is recommended for phase II/III trial. Chen et al recently showed that artesunate enhanced cancer cell death by inhibiting glycolysis in adriamycin-resistant chronic myeloid leukemia cells in vitro, thus giving credence to the molecular basis of artesunate in regulating glycolysis related enzymes (MDR1 and ABCG2) in leukemia cells. It is presently unknown whether artesunate can augment imatinib activity in the treatment of CML. The affordability and good clinical tolerability of artesunate and its proven anti-neoplastic property makes it suitable and worthwhile for this clinical trial in CML patients.

Details

1. . Study population: Consenting BCR-ABL positive chronic phase CML patients accessing imatinib at the OAUTHC, Nigeria.

2. . Study design: The study is a prospective randomized phase II clinical trial of artesunate and imatinib combination therapy in chronic phase CML patients. Patients will be recruited and followed up for at least 6 months of imatinib therapy.

   • Group C shall be 25 imatinib-exposed CML patients who have shown evidence of sub-optimal response to imatinib therapy. This group shall have standard-dose imatinib [400mg daily] plus artesunate [2mg/kg/day or 4mg/kg/day daily for 14 days every month]. Patients will be randomized to either doses called Group C2 or Group C4.

   Suboptimal response as defined by inability to achieve complete haematologic response (CHR) at 3months, major cytogenetic response (MCyR) at 6months, complete cytogenetic response (CCyR) at 12months or major molecular response (MMR) at 18months (Morotti et al., 2015).

   Group A: 25 newly diagnosed, imatinib naive, CP-CML patients placed on imatinib.

   Group B: 25 newly diagnosed, imatinib naive, CP-CML patients placed on imatinib and artesunate

3. . Sample Collections for pharmacokinetics analysis and imatinib levels 3mls of blood samples will be withdrawn from all the patients at pre-determined time intervals (0min, 30mins, 60mins, 120mins \& 360mins) into EDTA tubes this will be further processed to obtain plasma and this will be stored at -20oC.
4. . Tests: The following investigations will be conducted at the time of recruitment and monthly; Full blood count, Renal function test, Liver function test, and Bcr-Abl testing (every three months).
5. . Pharmacokinetic analysis: A bio-analytical LC-MS/MS will be developed and validated according to ICH guidelines to simultaneously determine the amount of imatinib, its metabolite (N-desmethylimatinib) and artesunate and its metabolite (dihydroartemisin). This method will be used to quantify the amount of these drugs in the plasma of the patients at 3months, 6months and 12months of follow-up.
6. . Study End points: The primary endpoint will be the achievement of Major Molecular remission (MMR/MR3) with bcr/abl-1 gene transcript ≤0.1 and deep molecular response (MR4) with bcr/abl-1 gene transcript ≤0.01 at 12 months. The secondary endpoints will include plasma imatinib levels at 6 and 12 months, disease progression and adverse events relating to long-term use of artesunate.

(h). Statistical analysis: The cumulative incidence of molecular response rate at 12 months, the primary end point, will be estimated using the Kaplan-Meier method. Secondary endpoints regarding patient characteristics and safety indices will be estimated with the use of paired-sample tests. Confidence intervals will be estimated at the 95% confidence level and 2-sided P \<0.05 will be considered to indicate statistical significance.

POTENTIAL VALUE OF THE RESEARCH RESULTS:

The results of the research may demonstrate if the use of artesunate is safe in CML patients beyond the traditional antimalaria dosing period as it has been determined in colorectal and breast cancer. The research may also evaluate if the combination of artesunate with imatinib may lead to better therapeutic outcome of the achievement of major molecular remission (MMR) in chronic phase CML patients and in the sub-optimal imatinib group. Also, it may show the influence of artesunate on the exposure of imatinib following co-administration of both.