Arsenic Trioxide Suppresses Growth of BCR-ABL1 Positive Cells with "Gatekeeper" or Compound Mutation

Introduction: Chronic myeloid leukemia (CML) and 30% of adult acute lymphatic leukemia (ALL) are characterized by the Philadelphia chromosome (Ph +), having a (9;22) chromosomal translocation. The BCR-ABL1 fusion protein is the hallmark of Ph + leukemia. BCR-ABL1 is characterized by constitutively activated ABL1 tyrosine kinase activity that determines its transformation potential. Tyrosine kinase inhibitors (TKI) have greatly improved the overall prognosis of these diseases. However, unsatisfactory responses in advanced disease stages, resistance and long-term tolerability of BCR-ABL1 inhibitors represent major clinical problems. The most important resistance mechanism against TKIs is the acquisition of point mutations within the BCR-ABL1 kinase domain that impair drug binding, restoring the oncoprotein's constitutively active tyrosine kinase activity. The selection of leukemic clones driven by BCR-ABL1 harboring point mutations, such as the E255K, Y253F/H (P-loop), H396R (activation loop) or the T315I (gatekeeper). Second- and third generation TKIs such as nilotinib, dasatinib, and ponatinib effectively overcome point mutation-mediated resistance. Ponatinib is the only U.S. Food and Drug Administration approved TKI with activity against all known BCR-ABL1 point mutations, including BCR-ABL1-T315I. However, the emergence of compound mutations (two mutations within the same BCR-ABL1 allele) has been linked to resistance to all approved TKIs, including ponatinib, posing a clinical challenge with limited treatment options. The anti-cancer agent arsenic trioxide (ATO) has been used to treat patients with acute promyelocytic leukemia (APL). APL patients respond very well to ATO therapy and achieve complete remission, possibly through induction of apoptosis and differentiation. In addition, it has been demonstrated that combined treatment of ATO with interferon or nilotinib significantly suppressed cell proliferation. However, the potential effects of ATO on BCR-ABL1 mutations and especially on compound mutation is not apparent. This study aimed to investigate the role of ATO in BCR-ABL1 resistant mutations, including compound mutation in Ph + leukemias. Methods: We undertook preclinical evaluation of ATO and compared it with approved TKIs e.g. imatinib, nilotinib, dasatinib, ponatinib and ABL inhibitor asciminib, in vitro models of CML and primary patient-derived long term cultures (PD-LTC) of Ph + ALL patients with or without mutation. The effects on mutational resistance were investigated in Ba/F3 cells expressing BCR-ABL1 with T315I mutation and T315I-E255K mutation. For non-mutational resistance, we used PD-LTCs from Ph + ALL patients with different levels of non-mutational drug resistance. Cell proliferation was assessed by XTT. Results: ATO efficiently inhibited the growth of all PD-LTCs in cellular assays at dosages of 200-500nM. It also suppressed the growth of Ph + PD-LTC with non- mutational resistance (BV) and the BCR-ABL1-T315I positive PD-LTC (KO) in this dosage range. In all modelsWe treated Ba/F3 cells expressing native BCR-ABL1, BCR-ABL1-T315I mutation and BCR-ABL1-T315I-E255K (compound mutation) with increasing concentrations of imatinib (250, 500 and 1000nM), nilotinib (100, 200 and 400nM), dasatinib (10, 25 and 50nM), ponatinib (10, 50 and 100nM), asciminib) (ABL allosteric inhibitor) (5, 10 and 20nM) and ATO (0.5, 1.0 and 2.0 µM). We found that all the inhibitors significantly inhibited the proliferation of Ba/F3 cells expressing wild type BCR-ABL1 in a dose-dependent manner. In contrast, the growth of Ba/F3 cells expressing BCR-ABL1-T315I was inhibited by increasing concentration of ponatinib, asciminib and ATO. ATO potently inhibited the most challenging mutation (T315I-E255K) with a clinically relevant concentration (IC50 250nM). All approved ABL kinase inhibitors (AKIs) and allosteric inhibitors like asciminib could not inhibit the growth of Ba/F3 cells expressing BCR-ABL1 compound mutation. Conclusions: Our findings indicate that ATO significantly suppressed the proliferation of cells expressing non-mutated BCR-ABL1, single and compound mutated BCR-ABL1. These results support including ATO in treating patients with Ph + leukemias having BCR-ABL1 resistant single or compound mutati Disclosures Ottmann: Novartis: Honoraria; Amgen: Honoraria, Research Funding; Celgene/BMS: Honoraria, Research Funding; Fusion: Honoraria; Incyte: Honoraria, Research Funding.

Portomesenteric thrombosis after robotic sleeve gastrectomy

Portomesenteric thrombosis is an important but rarely reported complication following bariatric surgery. It has been suggested that the incidence of portal vein thrombosis is directly related to many risk factors inherent in the bariatric population as well as factors related to local and systemic effects of laparoscopic surgery. Possible aetiologies vary from systemic inherited hypercoagulable states to a direct inflammatory reaction of portosystemic vessels. Here we present a case report of a 47-year-old obese women who underwent a robotic sleeve gastrectomy with subsequent development of a main portal vein, complete right intrahepatic portal vein and splenic vein thrombosis ultimately found to have a compound mutation of the methylenetetrahydrofolate reductase C677T and A1298C alleles.

Glucose-6-phosphate dehydrogenase deficiency in the Han Chinese population: molecular characterization and genotype–phenotype association throughout an activity distribution

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is a common hereditary disorder in China. The existing prevalence and molecular epidemiology of G6PD deficiency in China were geographically limited. In this study, the spectrum of G6PD gene mutations was well characterized in a large and diverse population all over the country; and the correlation of genotype and enzyme activity phenotype was explored for the first time. The results showed that the overall prevalence of G6PD deficiency in China was 2.10% at the national level. The top six common mutations were c.1388 G>A, c.1376 G>T, c.95 A>G, c.392 G>T, c.871 G>A and c.1024 C>T, accounting for more than 90% of G6PD deficient alleles. Compound mutation patterns were frequently observed in females with severe deficiency. The distribution of G6PD activities depended on the type of mutation patterns and genders. Hemizygote, homozygote, and compound heterozygote were predominantly associated with severe G6PD deficiency, whereas heterozygotes with single mutation mainly presented moderate enzyme deficiency. A significant gap between G6PD activities in hemizygous and normal males was observed, and yet, the overall distribution of that in females carrying missense mutations was a continuum from G6PD severely deficient to normal. This is the first report of discussing the association between G6PD genetic variants in the Chinese and enzyme activity phenotypes.

Treatment and Outcomes of Metastatic Non-Small-Cell Lung Cancer Harboring Uncommon EGFR Mutations: Are They Different from Those with Common EGFR Mutations?

Approximately 10% of the epidermal growth factor receptor (EGFR) mutations in non-small-cell lung cancer (NSCLC) are uncommon EGFR mutations. Although the efficacy of second (2G) or third generation (3G) EGFR tyrosine kinase inhibitors (EGFR-TKIs) in the patients with uncommon EGFR mutation has been proven, further studies are warranted to define the optimal treatment approach for uncommon EGFR mutation-positive NSCLC. This study retrospectively investigated the treatment patterns and outcomes of patients with uncommon EGFR mutation-positive NSCLC from January 2011 to December 2019 at the Samsung Medical Center, Seoul, Korea. During the study, 2121 patients with EGFR mutation-positive NSCLC received first-generation (1G, gefitinib or erlotinib) or 2G EGFR-TKI (afatinib) as the first-line (1L) systemic therapy. Of this, 135 (6.4%) patients harbored uncommon EGFR mutations. Of 135, 54 (40%, 54/135) patients had overlapping mutations with major EGFR mutations. The objective response rate (ORR) for the 1L EGFR-TKI was 63.3%. The median progression-free survivals (PFSs) were 8.6 months (95% CI: 3.8–13.5), 11.7 months (95% CI: 6.6–16.7), 7.7 months (95% CI: 4.9–17.4), and 5.0 months (95% CI: 3.7–6.1) for major uncommon EGFR mutation (G719X, L861Q), compound mutation with major EGFR mutation (Del 19 or EGFR exon 21 p.L858R), other compound mutation, and other uncommon mutations, respectively. The median overall survivals (OSs) were 25.6 months (16.9–34.2), 28.8 (95% CI: 24.4–33.4), 13.5 months (95% CI: 7.4–27.8), and 9.4 months (95% CI: 3.4–10.5) for major uncommon EGFR mutation (G719X), compound mutation with major EGFR mutation (Del 19 or EGFR exon 21 p.L858R), other compound mutation, and other uncommon mutations, respectively. The response rate, median PFS, and OS were 63.3%, 16.3 months (95% CI: 15.6–16.9), and 37.5 months (95% CI: 35.4–39.6) for common EGFR mutation-positive NSCLC. After failing 1L EGFR-TKI, repeated tissue or liquid biopsy were carried out on 44.9% (35/78) of patients with T790M detected in 10/35 (28.6%) patients. With subsequent 3G EGFR-TKI after failing the first-line EGFR-TKI, the ORR and PFS for 3G EGFR-TKI were 80% and 8.9 months (95% CI: 8.0–9.8). These patients showed a median OS of 34.6 months (95% CI: 29.8–39.4). The ORR, PFS and OS were poorer in patients with uncommon (especially other compound and other uncommon mutation) than those with common EGFR mutations. T790M was detected in 28.6% of the uncommon EGFR mutation-positive patients for whom prior 1G/2G EGFR-TKIs failed and underwent repeat biopsy at the time of progression.