C-kit Tyrosine Kinase Inhibitor Research Articles

A novel drug specific mRNA biomarker predictor for selection of patients responding to dovitinib treatment of advanced renal cell carcinoma and other solid tumors.

Dovitinib is a receptor tyrosine kinase inhibitor of VEGFR1-3, PDGFR, FGFR1/3, c-KIT, FLT3 and topoisomerase 1 and 2. The drug response predictor (DRP) biomarker algorithm or DRP-Dovitinib is being developed as a companion diagnostic to dovitinib and was applied retrospectively. Archival tumor samples were obtained from consenting patients in a phase 3 trial comparing dovitinib to sorafenib in renal cell carcinoma patients and the DRP-Dovitinib was applied. The biomarker algorithm combines the expression of 58 messenger RNAs relevant to the in vitro sensitivity or resistance to dovitinib, including genes associated with FGFR, PDGF, VEGF, PI3K/Akt/mTOR and topoisomerase pathways as well as ABC drug transport, and provides a likelihood score between 0-100%. The DRP-Dovitinib divided the dovitinib treated RCC patients into two groups, sensitive (n = 49, DRP score >50%) or resistant (n = 86, DRP score ≤ 50%) to dovitinib. The DRP sensitive population was compared to the unselected sorafenib arm (n = 286). Median progression-free survival (PFS) was 3.8 months in the DRP sensitive dovitinib arm and 3.6 months in the sorafenib arm (hazard ratio 0.71, 95% CI 0.51-1.01). Median overall survival (OS) was 15.0 months in the DRP sensitive dovitinib arm and 11.2 months in the sorafenib arm (hazard ratio 0.69, 95% CI 0.48-0.99). The observed clinical benefit increased with increasing DRP score. At a cutoff of 67% the median OS was 20.6 months and the median PFS was 5.7 months in the dovitinib arm. The results were confirmed in five smaller phase II trials of dovitinib which showed a similar trend. The DRP-Dovitinib shows promise as a potential biomarker for identifying advanced RCC patients most likely to experience clinical benefit from dovitinib treatment, subject to confirmation in an independent prospective trial of dovitinib in RCC patients.

Antineoplastic Activity of Pazopanib in Anaplastic Thyroid Cancer in Primary Culture.

Anaplastic thyroid cancer (ATC) is a rare and rapidly fatal human cancer. Its usual treatment includes the combination of surgery, external hyperfractionated radiation therapy, and chemotherapy. These treatments permit achieving about 6-10 months of median survival. For this reason, it is challenging to predict the ATC patient clinical therapy responsiveness. Pazopanib is a multitarget tyrosine kinase inhibitor of VEGF receptors, PDGF, and c-Kit. Until now, the effect of pazopanib in primary human ATC cells (pATC) has not been reported in the literature. The aim of our study was to evaluate in vitro the antineoplastic effect of pazopanib in pATC. Surgical thyroidal tissues were collected from five patients with ATC, from thyroid biopsy at the moment of first surgical operation. An inhibition of proliferation, migration, and invasion, and an increase in apoptosis were demonstrated upon treating pATC cells with pazopanib (p < 0.05). Moreover, pazopanib was able to significantly decrease the VEGF expression in pATC cells (p < 0.05). To conclude, in this study, we demonstrate the antineoplastic activity of the antiangiogenic inhibitor, pazopanib, in human pATC in vitro.

PB2059: SUCCESSFUL OUTCOME OF A PATIENT WITH ADVANCED SYSTEMIC MASTOCYTOSIS TREATED WITH AZACYTIDINE AND AVAPRITINIB: A CASE REPORT

Background: Systemic mastocytosis (SM) with an associated hematologic neoplasm (AHN) comprise approximately 70% of patients with Advanced SM (AdvSM). >80% of patients with SM-AHN have associated myeloid neoplasms: CMML being common. The median overall survival of patients with SM-CMML is reported to be 15 months. Current algorithms for patients with SM-AHN direct treatment to each of the components tailored to the patient. Avapritinib,a C-KIT tyrosine kinase inhibitor, approved by the FDA in 2021 for patients with AdvSM has an overall response rate of 70% as reported in early phase trials. Aims: To report successful treatment of advanced SM: SM+CMML, both components requiring treatment simultaneously. Methods: A retrospective review of a case (with patient consent). Results: A 58yr old previously fit male was seen in July 2019 with urticaria pigmentosa, recent significant weight loss & mild hepatosplenomegaly. Initial blood counts:hemoglobin(Hb) 123g/L;leukocytes(WBC) 32.6x109/L;platelets(PLT) 123x109/L;neutrophils 20.5x109/L;lymphocytes 3.3x109/L;monocytes 4.2x109/L;eosinophil 0.7x109/L and normal biochemistry. His MC Tryptase was 54.4µg/L. JAK2 V617F & C-KIT D816V mutations was detected. A diagnostic bone marrow trephine(BM) in July 2019 was >90% cellular with marked granulocytic proliferation, hypolobated megakaryocytes, peritrabecular spindle shaped mast cells(10%) positive for CD117 and CD25 immunostains &focal fibrosis of WHO grade 0-1,with diagnosis of SM with CMML. Cytogenetics were normal. Myeloid gene panel detected high risk mutations (TET2 x2, SRSF2). He initially declined treatment. By October 2020, he had intense pruritus, further weight loss, night sweats, bone pain, progressive hepatosplenomegaly, small volume generalised lymphadenopathy, mild ascites & progressive cytopenias (Hb 60g/L & PLT 43x109/L), leucocytosis(WBC 48.9x109/L) & MC tryptase of 105µg/L. Repeat BM showed MC burden of 15-20% (MC tryptase+, CD117+, CD25+) in a hypercellular marrow with predominant increase in granulopoiesis with 20% monocytic cells(CD14+), no increase in CD34+ cells: consistent with evidence of progression of both components. He was treated with azacytidine to debulk the CMML component due to progressive cytopenias and leucocytosis. His PLT count of < 50 x 109/L precluded eligibility onto the PATHFINDER trial due to a risk of intracranial haemorrhage. After 3 cycles, his blood counts improved (Fig 1) and correction of thrombocytopenia (PLT 282 x109/L) allowed treatment of the SM component by avapritinib via Compassionate Access Programme and he started avapritinib 200mg daily. He had rapid symptom improvement with resolution of ascites, hepatosplenomegaly & lymphadenopathy. BM post 4 cycles of avapritinib showed complete remission of SM with persistent CMML-0. MC tryptase normalised to 7.4 µg/L with WBC slowly rising again off azacitidine(Fig 1). He is currently asymptomatic on 100mg of avapritinib. Image:Summary/Conclusion: This patient needed treatment of symptoms predominantly due to SM; thrombocytopenia precluded treatment with avapritinib. The CMML component was treated first to improve thrombocytopenia with azacytidine followed by avapritinib for the SM component. The outcome was excellent with complete remission of his SM component & marked clinical improvement. The patient can be considered for an allogeniec bone marrow transplant as a curative treatment. International trials with sequential/combination therapy for patients with AdvSM in the new era of targeted C-KIT inhibitors will inform better treatment decisions for patients with SM-AHN.

Vitamin D Enhances Anticancer Properties of Cediranib, a VEGFR Inhibitor, by Modulation of VEGFR2 Expression in Melanoma Cells.

Regardless of the recent groundbreaking introduction of personalized therapy, melanoma continues to be one of the most lethal skin malignancies. Still, a substantial proportion of patients either fail to respond to the therapy or will relapse over time, representing a challenging clinical problem. Recently, we have shown that vitamin D enhances the effectiveness of classical chemotherapeutics in the human malignant melanoma A375 cell line. In search for new combination strategies and adjuvant settings to improve melanoma patient outcomes in the current study, the effects of cediranib (AZD2171), an oral tyrosine kinase inhibitor of VEGFR1-3, PDGFR, and c-KIT, used in combination either with 1,25(OH)2D3 or with low-calcemic analog calcipotriol were tested on four human malignant melanoma cell lines (A375, MNT-1, RPMI-7951, and SK-MEL-28). Melanoma cells were pretreated with vitamin D and subsequently exposed to cediranib. We observed a marked decrease in melanoma cell proliferation (A375 and SK-MEL-28), G2/M cell cycle arrest, and a significant decrease in melanoma cell mobility in experimental conditions used (A375). Surprisingly, concurrently with a very desirable decrease in melanoma cell proliferation and mobility, we noticed the upregulation of VEGFR2 at both protein and mRNA levels. No effect of vitamin D was observed in MNT-1 and RPMI-7951 melanoma cells. It seems that vitamin D derivatives enhance cediranib efficacy by modulation of VEGFR2 expression in melanoma cells expressing VEGFR2. In conclusion, our experiments demonstrated that vitamin D derivatives hold promise as novel adjuvant candidates to conquer melanoma, especially in patients suffering from vitamin D deficiency. However, further extensive research is indispensable to reliably assess their potential benefits for melanoma patients.

Drug Repurposing Patent Applications April–June 2021

Drug Repurposing Patent Applications April–June 2021

1308P Efficacy and safety of anti-PD-1 therapy plus anlotinib in previously treated advanced NSCLC

Nivolumab or pembrolizumab is the standard second-line treatment for patients (pts) with advanced NSCLC. Anlotinib is an oral VEGFR, FGFR, PDGFR and c-Kit tyrosine kinase inhibitor. The interaction between tumor immune microenvironment and angiogenesis has been well established. This study was designed to assess the benefit and optimal time of nivolumab or pembrolizumab plus anlotinib in previously treated advanced NSCLC.

A randomized phase II multi-institutional trial of anlotinib plus docetaxel versus docetaxel in EGFR-wild-type non-small cell lung cancer (NSCLC) patients after progression on first-line platinum-base chemotherapy: ALTER-L018.

e21703 Background: Anlotinib is an oral VEGFR, FGFR, PDGFR and c-Kit tyrosine kinase inhibitor, which can prolong both PFS and OS of refractory advanced NSCLC patients in phase III trial: ALTER0303. The combination of docetaxel and ramucirumab/nintedanib had been demonstrated activity in the second line therapy setting for NSCLC. We performed ALTER-L018 to assessed the safety and efficacy of anlotinib with docetaxel in EGFR-wild type refractory advanced NSCLC (NCT03624309). Methods: Patients (pts) with EGFR-wild type refractory advanced NSCLC, who failed to first-line platinum-based chemotherapy, were randomized to group A(anlotinib: 12mg QD from day 1 to 14 of a 21-day cycle +docetaxel: 75mg/m2 Q3W) and group B(docetaxel: 75mg/m2 Q3W). The primary end points is PFS, and secondary end points include OS, ORR, DCR and safety. Results: Between January and December 2019, 36 pts were enrolled at 10 institutions in Hunan China, with 31(15 in group A, 16 in group B) of these individuals being evaluable for treatment efficacy and safety. Pt characteristics(group A/ group B): median age: 55(39-70)/57(44-67); male: 73%/81%; non-squamous NSCLC: 86%/75%. Median PFS were 5.3 months (95%CI:2.76-7.85) in group A and 2.3 months (95%CI, 1.14-3.46) in group B (HR 0.42; 95% CI:0.16-1.13; p = 0.047); In group A and B, ORR and DCR were 26.67% versus 0%(p = 0.043), 60.00% versus 31.25%(p = 0.16), respectively. Among 31 pts, 89% of treatment-related AEs (TRAEs) were grade 1 or 2, and the most common TRAEs in group A were hand-foot syndrome, pruritus and insomnia of 13%(2/15) each; in group B were alopecia, constipation and anemia of 12%(1/16) each. Toxicities≥grade 3(TRAEs) included: neutropenia, leukopenia, diarrhea and hrombocytopenia, 6.6%(1/15) each in group A. There was 1 grade 5 AE in group A. Conclusions: This combination of anlotinib and docetaxel with significant difference PFS prolonging and manageable safety profile, is a viable option in relapsed NSCLC, should be considered following progression on platinum-based chemotherapy. It will be further explored in a randomized phase III trial. Clinical trial information: NCT03624309.

The efficacy and safety profile of anlotinib with etoposide plus cisplatin/carboplatin in treatment-naive extensive-stage small cell lung cancer(SCLC) patients: Results from a phase II single-arm trial.

9066 Background: Combination of etoposide and cisplatin/carboplatin is the most commonly used initial chemoptherapy regiment in extensive-stage small cell lung cancer. A meta-analysis released that, there is no significant difference was observed in Objective response rate(ORR), progression-free survival (PFS), or overall survival(OS) in patients(pts) receiving cisplatin-base versus carboplatin-based regimens. We performed a single-arm phase II trial to determine if maintain of single-agent anlotinib, an oral VEGFR, FGFR, PDGFR and c-Kit tyrosine kinase inhibitor, after 4-6 cycles of anlotinib + etoposide + cisplatin/carboplatin would improve PFS and ORR. Methods: SCLC pts (18~70 yrs, extensive-stage SCLC, no prior systematic chemo/ICI therapy) received anlotinib( 12mg QD from day 1 to 14 of a 21-day cycle) +etoposide( 100mg/m2, d1~3 of 21-day cycle)+ cisplatin( 75-80mg/m2,Q3W)/ carboplatin( AUC = 5~6,Q3W) for 4~6 cycles, and anlotinib maintenance. The dual-primary endpoint were PFS and ORR. Results: Between Oct.2018 to Dec.2019, 27 pts enrolled and included in the efficacy and safety analysis: age: median 62 (range:44-71); male 93%; cisplatin/ carboplatin/ both 11%/78%/11%; 37%(10/27) of pts required chemotherapy dose modification only, and the other 30% (8/27) of pts required anlotinib+ chemotherapy dose modification.The median PFS was 9.61 months ( 95%Cl:7.80-11.42). ORR was 77.78% (21/27), disease control rate (DCR) was 96.30% (26/27).Toxicities≥grade 3 included: neutropenia 22%, leukopenia 11%, hand-foot syndrome 15%, nausea 4%, mucositis 4%, edema 4%, anorexia 4%, xerostomia 4% and fatigue 4%; there were no grade 5 toxicities. Conclusions: Combined treatment with anlotinib plus etoposide and cisplatin/carboplatin for treatment-naive extensive-stage SCLC was well tolerated with promising PFS and ORR to date but showed no new risk for AEs. Based on these encouraging results, phase III trial of anlotinib plus etoposide and cisplatin/carboplatin for treatment-naive SCLC has been warranted.

Targeted sequencing reveals the mutational landscape responsible for sorafenib therapy in advanced hepatocellular carcinoma.

Rationale: The existence of primary and acquired drug resistance is the main obstacle for the effect of multi-kinase inhibitor sorafenib and regorafenib in advanced hepatocellular carcinoma (HCC). However, plenty of patients did not significantly benefit from sorafenib treatment and little is known about the mechanism of drug resistance.Methods: Laser capture microdissection was used to acquire matched normal liver and tumor tissues on formalin-fixed paraffin-embedded specimens collected before sorafenib therapy from the first surgery of 119 HCC patients. Ultra-deep sequencing (~1000×) targeting whole exons of 440 genes in microdissected specimens and siRNA screen in 7 cell lines were performed to find mutations associated with differential responses to sorafenib. Patient-derived xenograft models were employed to determine the role of TP53 in response to sorafenib. Lentiviruses harboring wild-type and c.G52C-mutant OCT4 were applied to explore the function of OCT4 in resistance to sorafenib. ChIP-PCR assay for analysis of OCT4 transcriptional activity was performed to explore the affinity with the KITLG promoter. Statistical analyses were used to associate levels of p53 and OCT4 with tumor features and patient outcomes.Results: Total 1,050 somatic mutations and 26 significant driver genes were identified. SiRNA screening in 7 HCC cell lines was further performed to identify mutations associated with differential responses to sorafenib. A recurrent nonsynonymous mutation c.G52C in OCT4 (OCT4mut) was strongly associated with good response to sorafenib, whereas the stop-gain mutation in TP53 showed the opposite outcome both in vitro and in vivo. OCT4wt-induced stem cell factor (encoded by KITLG gene, SCF) expression and cross-activation of c-KIT/FLT3-BRAF signals were identified indispensably for sorafenib resistance, which could be reversed by the combination of c-KIT tyrosine kinase inhibitors or neutralizing antibody against SCF. Mechanistically, an OCT4 binding site in upstream of KITLG promoter was identified with a higher affinity to wildtype of OCT4 rather than G52C-mutant form, which is indispensable for OCT4-induced expression of KITLG and sorafenib resistance.Conclusion: Our study reported a novel somatic mutation in OCT4 (c.G52C) responsible for the sorafenib effect, and also shed new light on the treatment of HCC through the combination of specific tyrosine kinase inhibitors according to individual genetic patterns.

P2.01-20 Anlotinib vs. Docetaxel in Advanced Non-Squamous NSCLC (EGFR Wild-Type) After Progression on Platinum-Based Chemotherapy: A Trial Protocol

Anlotinib, an oral VEGFR, FGFR, PDGFR and c-Kit tyrosine kinase inhibitor, showed significantly longer overall survival in a phase 3 trial. In the multi-center, open-label, randomized controlled ALTER-L023 trial, we compared anlotinib with docetaxel as second-line treatment in patients with advanced non-squamous EGFR wild-type non-small cell lung cancer (NSCLC) previously given platinum-based doublet chemotherapy. This multi-center, open-label, randomized controlled ALTER-L023 trial was conducted at 10 hospitals in China. Eligible patients with previously treated non-squamous EGFR wild-type NSCLC were randomly assigned (1:1) to receive anlotinib (12 mg QD from day 1 to 14 of a 21-day cycle) or docetaxel (75mg/m2, on day 1 of a 21-day cycle) till progression or intolerable toxicity. The primary endpoint was progression-free survival (PFS), that was defined as the time from randomization to disease progression or death. The secondary endpoints included objective response rate, disease control rate, duration of response and safety. Based on a two-sided log-rank test at 5% significance level, a power of 80% and a median PFS of 6 months for anlotinib versus 3 months for docetaxel, the simple size was estimated at 77 patients. Allowing for 15% dropouts, the sample size was set at 88 patients (44 patients in both groups). Clinical trial information: NCT03703596 Section not applicable Section not applicable

A phase I study of pazopanib with weekly paclitaxel and carboplatin in advanced solid tumors.

3021 Background: Pazopanib (pazo) is an oral tyrosine kinase inhibitor of VEGFR, PDGFR and c-Kit. It is a weak inhibitor of CYP3A4 and CYP2C8 and may decrease paclitaxel (P) clearance. Daily pazo with P and carboplatin (C) every 21 days was not feasible on a previous study. We hypothesized that pazo dosed intermittently and on a different day from P and C may be tolerable. We sought to determine the maximum tolerated dose (MTD), dose-limiting toxicity (DLT), and pharmacokinetics (PK) of pazo with weekly P and C. Methods: Using a 3+3 standard design, a schedule of P 60-80 mg/m2 and C AUC2 on days 1, 8, and 15 with pazo 400-800 mg on days 2-5, 9-12, and 16-26 on a 28-day cycle was evaluated. Pazo alone could be continued if P and C were omitted due to maximal benefit or toxicity. PK was collected during cycles 1 and 2. Results: 34 patients (pts) were treated over 6 dose levels (Table). Mean age 57 (37-79). Tumor types: breast (22), lung (3) and other (9); 27 had prior platinum. Delay in starting cycle 2 due to grade 3 neutropenia was a DLT at dose level 2 and 5. Pts on 5A missed dosing during C1 and C2 due to neutropenia and required subsequent growth factor, and this was deemed unlikely to be sustainable long-term. All grade toxicities included anemia (62%), neutropenia (59%), and thrombocytopenia (56%). Protocol-defined MTD was not determined. PK analysis showed a dose proportional increase in pazo concentration, consistent with previous reports. Pazo did not alter the PK of C. Cmax of P was higher C2D1 vs C1D1; mean Cmax ratio between C2D1:C1D1 was 1.63 (95% CI:1.29-1.96). There were 11 objective responses (3 CRs, 8 PRs). Five breast pts were on pazo alone for a median of 9 cycles (2-52) with CR (2), PR (2) and SD (1); a squamous cell of unknown primary in CR received 22 cycles. Clinical trial information: NCT01407562. Conclusions: PK confirm that pazo is a weak inhibitor of CYP3A4 and CYP2C8. Myelosuppression was a major adverse event at all dose levels. MTD was not determined. Antitumor activity was achieved with this alternate combination schedule and sustained responses from sequential pazo monotherapy was observed.[Table: see text]

Abstract 2508: Effect of ALK-inhibitors in synovial sarcoma (SS) cell line HS-SYII

Abstract Synovial sarcoma (SS) accounts for approximately 8% of all soft tissue sarcomas (STS). The prognosis is poor because of a few effective chemotherapy regimens for STS such as Doxorubicin, Eribulin, and Trabectedin. Pazopanib, a multi-targeted tyrosine kinase inhibitor of PDGFR, VEGFR and c-Kit, is the first molecular targeted drug approved by FDA for STS. Recently, a preclinical efficacy of MET-inhibitor and ALK-inhibitor for a synovial sarcoma cell line was reported. We found that the response to ALK-inhibitors (Alectinib, Crizotinib and Lorlatinib) for SS cell line HS-SY-II different from Aska-SS cell line in a previous report. In addition, a combination of ALK-inhibitor and Pazopanib, previously reported that single-agent is effective in HS-SY-II, potentiates a cytotoxic effect by MTT assay than each single agent. Western blotting revealed that both of ALK-inhibitor single agent and the combination of Pazopanib and ALK-inhibitor suppress the phosphorylation of ERK and AKT, downstream of MAPK and PI3K pathway. Our data suggests that the combination therapy Pazopanib and ALK-inhibitor may be effective to SS patients clinically. Citation Format: Hiroshi Gyotoku. Effect of ALK-inhibitors in synovial sarcoma (SS) cell line HS-SYII [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2508.

Abstract CT016: Abexinostat (ABX) as a means to reverse pazopanib (PAZ) resistance: a phase I study in advanced solid tumor malignancies

Abstract Background: PAZ is a tyrosine kinase inhibitor of VEGFR, PDGFR, and c-KIT approved for use in renal cell carcinoma (RCC). ABX is a potent pan-HDAC inhibitor (HDACi). Pre-clinical models suggest that HDACi-mediated epigenetic modulation of VEGF expression prevents PAZ resistance and potentiates efficacy. We therefore designed a Phase I clinical trial combining ABX with PAZ in pts with advanced solid tumors with an expansion cohort in RCC. Methods: The primary endpoint was the maximal tolerated dose (MTD) of PAZ plus ABX. Secondary endpoints included pharmacokinetics (PK) and efficacy. PAZ was dosed days 1-28 and ABX days 1-5, 8-12, and 15-19 of 28-day cycle (schedule A) with at a starting dose of 400 mg/day and 45 mg/m2 orally twice daily respectively. An alternate ABX dosing schedule days 1-4, 8-11, and 15-18 was investigated (schedule B) due to toxicity of Schedule A. Results: 52 patients (pts) (RCC; N = 23) with advanced solid tumors were enrolled (N = 22 schedule A; N = 30 schedule B). There were six dose-limiting toxicities including fatigue (N = 2), thrombocytopenia (N = 2), and elevated AST/ALT (N = 2). The most common grade ? 3 related adverse events observed were fatigue (13%), thrombocytopenia (12%), and diarrhea (10%). The MTD was PAZ 800 mg/day + ABX 45 mg/m2 BID on schedule B. 8 evaluable pts (19%) (N = 6 RCC; 2 thyroid; median number of prior lines of therapy = 3) achieved partial tumor response (PR), with median duration of response of 9.2 months (1-33.2+). 7/9 (78%) of pts with prior disease progression on PAZ monotherapy had reduction in tumor burden on study. 15 out of 48 evaluable pts (31%) experienced stable disease or better for ? 6 months, and two previously PAZ-refractory pts with PRs remain on study for &amp;gt; 20 and 37 mos respectively. PK analyses did not reveal drug-drug interaction. Degree of histone acetylation and metabolomic profile are being evaluated. Conclusion: The combination of PAZ + ABX was well tolerated and durable tumor control (&amp;gt; 3 yrs) was observed in RCC and thyroid cancer. Tumor regressions observed in majority of PAZ-refractory tumors preliminarily support the potential of ABX to reverse therapeutic resistance. A randomized phase 2 study with cross-over design is planned to further evaluate the combination of PAZ + HDACi. Citation Format: Rahul Aggarwal, Scott Thomas, Jennifer Grabowsky, Armand Harb, Jim Leng, Anne Reinert, Ilaria Mastroserio, Thach-Giao Truong, Pamela N. Munster. Abexinostat (ABX) as a means to reverse pazopanib (PAZ) resistance: a phase I study in advanced solid tumor malignancies. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr CT016.

Prognostic Value of C-kit and VEGF Expression in Small Cell Lung Cancer

SESSION TITLE: Lung Cancer Treatment Posters SESSION TYPE: Original Investigation Poster PRESENTED ON: Wednesday, October 28, 2015 at 01:30 PM - 02:30 PM PURPOSE: Lung cancer is the leading cause of cancer related death in the world. Small cell lung cancer (SCLC) is an aggressive form of lung cancer with poor clinical course. Despite using new technologies and chemotherapeutic agents, little progress has been made in prolonging survival in SCLC. Performans status (PS), stage, age, gender, number of metastatic sites, weight loss and biochemical variables, such as serum albumin, sodium, alkaline phosphatase, lactat dehidrogenase levels are used to define prognosis in SCLC. However investigations are going on for finding a beter prognostic marker. The C-kit protein, which has type 3 receptor tyrosine kinase activity has been implicated in the pathophysiology of many tumors, including SCLC. Vascular endothelial growth factor (VEGF) expression was also corrolated to an increased risk of metastatic disease and a worse survival due to the role of angiogenesis in SCLC. METHODS: In our study we aimed to evaluate VEGF and C-kit expression and relation between survival and clinical factors affecting the prognosis of 53 patients who were diagnosed with SCLC between January 2005- August 2010. The expressions of VEGF and C-kit were studied immonuhistochemically. RESULTS: The expression of VEGF was detected in 64,2% and the expression of C-kit was detected in 60,4% of the patients. The results showed that VEGF and C-kit expressions were not associated with prognostic factors and survival. A multivariate analysis was perfomed to evaluate independent prognostic role of age, weight loss, PS, serum albumin level and stage. This analysis indicated that PS (p=0.001) and serum albumin (p=0.032) level had independent prognostic value on overall survival. CONCLUSIONS: Although our results did not show any correlations we recommend that the prognostic value of VEGF and C-kit expressions, must be further investigated in prospective and large studies due to their role in pathogenesis. CLINICAL IMPLICATIONS: The role of VEGF and C-kit expressions as an important event in the pathogenesis of SCLC are still debated, and remain to be clarified whether this expressions are relevant for tumor growth and survival. Based on the available data reported in the literature, C-kit tyrosine kinase inhibitors and VEGF-targeting monoclonal antibody bevacizumab have substantial clinical benefits. As a result, to understand the prognostic value of VEGF and C-kit expressions new studies and large series needed. DISCLOSURE: The following authors have nothing to disclose: Gulen Topaloglu, Aydin Yilmaz, Funda Demirag, Yurdanur Erdogan, Sezgi Sahin Duyar, Ulkü Yilmaz No Product/Research Disclosure Information

Endothelial cell derived angiocrine support of acute myeloid leukemia targeted by receptor tyrosine kinase inhibition

In acute myeloid leukemia (AML), refractory disease is a major challenge and the leukemia microenvironment may harbor refractory disease. Human AML cell lines KG-1 and HL-60 expressed receptors also found on endothelial cells (ECs) such as VEGFRs, PDGFRs, and cKit. When human AML cells were co-cultured with human umbilical vein endothelial cells (HUVECs) and primary bone marrow endothelial cell (BMECs), the AML cells were more resistant to cytarabine chemotherapy, even in transwell co-culture suggesting angiocrine regulation. Primary BMECs secreted significantly increased levels of VEGF-A and PDGF-AB after exposure to cytarabine. Pazopanib, a receptor tyrosine kinase inhibitor (RTKI) of VEGFRs, PDGFRs, and cKit, removed EC protection of AML cells and enhanced AML cell sensitivity to cytarabine. Xenograft modeling showed significant regression of AML cells and abrogation of BM hypervascularity in RTKI treated cohorts. Together, these results show direct cytotoxicity of RTKIs on AML cells and reversal of EC protection. Combining RTKIs with chemotherapy may serve as promising therapeutic strategy for patients with AML.

Abstract 1964: Masitinib antagonizes ATP-binding cassette subfamily c member 10-mediated paclitaxel resistance: a preclinical study

Abstract Paclitaxel displays clinical activity against a wide variety of solid tumors. However, resistance to paclitaxel significantly attenuates the response to chemotherapy. The ABC transporter subfamily C member 10 (ABCC10), also known as multi-drug resistance protein 7 (MRP7) efflux transporter, is a major mediator of paclitaxel resistance. In this study, we show that masitinib, a small molecule stem-cell growth factor receptor (c-Kit) tyrosine kinase inhibitor, at non-toxic concentrations, significantly attenuates paclitaxel resistance in HEK293 cells transfected with ABCC10. Our in vitro studies indicated that masitinib (2.5 μM) enhanced the intracellular accumulation and decreased the efflux of paclitaxel by inhibiting the ABCC10 transport activity without altering the expression level of ABCC10 protein. Furthermore, masitinib, in combination with paclitaxel, significantly inhibited the growth of ABCC10-expressing tumors in nude athymic mice in vivo. Masitinib administration also resulted in a significant increase in the levels of paclitaxel in the plasma, tumors and lungs compared to paclitaxel alone. In conclusion, the combination of paclitaxel and masitinib could serve as a novel and useful therapeutic strategy to reverse paclitaxel resistance mediated by ABCC10. Citation Format: Rishil Kathawala, Kamlesh Sodani, Kang Chen, Atish Patel, Alaa Abuznait, Nagaraju Anreddy, Yue-Li Sun, Amal Kaddoumi, Charles R. Ashby, Zhe-Sheng Chen. Masitinib antagonizes ATP-binding cassette subfamily c member 10-mediated paclitaxel resistance: a preclinical study. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1964. doi:10.1158/1538-7445.AM2014-1964

Nilotinib in Combination with Carboplatin and Paclitaxel Is a Candidate for Ovarian Cancer Treatment

Purpose: Nilotinib is a selective tyrosine kinase inhibitor of c-Kit, Abl and platelet-derived growth factor receptor-α/β. To evaluate nilotinib's potential use as a treatment of human ovarian cancer, we tested nilotinib's preclinical activity in ovarian cancer cell lines with different tyrosine kinase expression patterns. Methods: The effects of nilotinib on ovarian cancer cell growth were studied alone and in combination with carboplatin and paclitaxel. Proapoptotic and antimigratory effects were examined using TUNEL and migration assays. Results: Nilotinib alone and in combination with carboplatin and paclitaxel significantly inhibited cell growth in PDGFR-α-positive ovarian cancer cell lines. The combination of nilotinib with carboplatin and paclitaxel showed synergistic effects on cell proliferation. Nilotinib treatment led to the inhibition of cell migration alone and in combination with carboplatin and paclitaxel. Apoptosis induction occurred in response to nilotinib that increased in combination with carboplatin. Conclusions: Nilotinib may be a feasible targeted therapy option for the treatment of ovarian cancer.

Phase I study of pazopanib (PAZ) in combination with abexinostat (ABX) in patients (Pts) with metastatic solid tumors.

2560 Background: PAZ is a tyrosine kinase inhibitor of VEGFR, PDGFR, and C-KIT approved for use in renal cell carcinoma (RCC) and soft tissue sarcoma (STS). ABX is a potent pan-HDAC inhibitor (HDAC...

Masitinib Antagonizes ATP-Binding Cassette Subfamily C Member 10–Mediated Paclitaxel Resistance: A Preclinical Study

Paclitaxel displays clinical activity against a wide variety of solid tumors. However, resistance to paclitaxel significantly attenuates the response to chemotherapy. The ABC transporter subfamily C member 10 (ABCC10), also known as multidrug resistance protein 7 (MRP7) efflux transporter, is a major mediator of paclitaxel resistance. In this study, we show that masitinib, a small molecule stem-cell growth factor receptor (c-Kit) tyrosine kinase inhibitor, at nontoxic concentrations, significantly attenuates paclitaxel resistance in HEK293 cells transfected with ABCC10. Our in vitro studies indicated that masitinib (2.5 μmol/L) enhanced the intracellular accumulation and decreased the efflux of paclitaxel by inhibiting the ABCC10 transport activity without altering the expression level of ABCC10 protein. Furthermore, masitinib, in combination with paclitaxel, significantly inhibited the growth of ABCC10-expressing tumors in nude athymic mice in vivo. Masitinib administration also resulted in a significant increase in the levels of paclitaxel in the plasma, tumors, and lungs compared with paclitaxel alone. In conclusion, the combination of paclitaxel and masitinib could serve as a novel and useful therapeutic strategy to reverse paclitaxel resistance mediated by ABCC10.

Interstitial Cells of Cajal Modulate the Tone of the Human Internal Anal Sphincter In Vitro

Interstitial cells of Cajal, expressing the proto-oncogene c-kit, have been shown to regulate the spontaneous activity of the gastrointestinal tract. They have been described in the human internal anal sphincter; however, their function is still unclear. We examined the effects of the c-kit tyrosine kinase inhibitor imatinib mesylate on sphincter strips to investigate the function of the interstitial cells. This was a case series study. This was a single-center study conducted at the University of Oxford. Internal anal sphincter strips were collected from 10 patients undergoing abdominoperineal resection or proctectomy and mounted in organ bath. Responses to electrical field stimulation and chemical agents were monitored in the absence of drugs and after the administration of increasing doses of imatinib mesylate. Immunohistochemistry was performed to identify interstitial cells. The role of the interstitial cells in the internal anal sphincter was assessed. Imatinib mesylate significantly reduced the tone and the spontaneous activity of the strips. In the absence of drugs, the tone generated was 147.7 ± 33.0 mg/mg of tissue. Administration of ≥5 μM of imatinib mesylate caused a dose-dependent reduction in the tone. Strips exhibited spontaneous activity characterized by intermittent low-amplitude contractions superimposed on basal tone (135.6 ± 4.6 contractions in 10 minutes). Imatinib mesylate significantly reduced the number of contractions at concentration >5 μM. No differences were observed in the responses to electrical field stimulation, carbachol, or phenylephrine. Immunohistochemistry showed c-kit-positive cells. This study was limited by the relatively small number of patients enrolled and thus the difficulty of finding human tissue for laboratory studies. Our results suggest that the interstitial cells modulate the tone and the spontaneous activity of the internal anal sphincter. This provides a foundation for new approaches to preclinical and clinical research. Moreover, these cells may represent a target for drugs inhibiting the c-kit receptor and provide a new approach for treating anorectal diseases.